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Anatomy of the Anterior Cruciate Ligament with Regard to Its Two Bundles
Abstract
The anterior cruciate ligament (ACL) consists of two major fiber bundles, namely the anteromedial and posterolateral bundle. When the knee is extended, the posterolateral bundle (PL) is tight and the anteromedial (AM) bundle is moderately lax. As the knee is flexed, the femoral attachment of the ACL becomes a more horizontal orientation; causing the AM bundle to tighten and the PL bundle to relax. There is some degree of variability for the femoral origin of the anterome-dial and posterolateral bundle. The anteromedial bundle is located proximal and anterior in the femoral ACL origin (high and deep in the notch when the knee is flexed at 90 degrees ); the posterolateral bundle starts in the distal and posterior aspect of the femoral ACL origin (shallow and low when the knee is flexed at 90 degrees ). In the frontal plane the anteromedial bundle origin is in the 10:30 clock position and the postero-lateral bundle origin in the 9:30 clock position. At the tibial insertion the ACL fans out to form the foot region. The anteromedial bundle insertion is in the anterior part of the tibial ACL footprint, the posterolateral bundle in the posterior part. While the anteromedial bundle is the primary restraint against anterior tibial translation, the posterolateral bundle tends to stabilize the knee near full extension, particularly against rotatory loads.
... Landmarks for the femoral ACL insertion are the intercondylar line and the cartilage-bony junction as described previously. 6 If the guidewire entry point is deemed correct, the guidewire is reinserted and overdrilled with a 4.5 mm drill bit. The length of the tunnel is then determined. ...
... Potential complications and their corresponding prevention techniques include the following: infection that can be prevented by presoaking the graft in vancomycin, 3 cartilage damage at the medial femoral condyle due to the drill bit that can be prevented by correct medial portal placement, 6 posterior blow out of the femoral tunnel (consider femoral suspensory fixation), tunnel malplacement that can be prevented if you are familiar with anatomic landmarks and if you are uncertain, check the tunnel position with the fluoroscope. 6 For postoperative rehabilitation, a 3-phase and criteriabased rehabilitation protocol is recommended. ...
... Potential complications and their corresponding prevention techniques include the following: infection that can be prevented by presoaking the graft in vancomycin, 3 cartilage damage at the medial femoral condyle due to the drill bit that can be prevented by correct medial portal placement, 6 posterior blow out of the femoral tunnel (consider femoral suspensory fixation), tunnel malplacement that can be prevented if you are familiar with anatomic landmarks and if you are uncertain, check the tunnel position with the fluoroscope. 6 For postoperative rehabilitation, a 3-phase and criteriabased rehabilitation protocol is recommended. Phase 1 focuses on controlling inflammation and pain. ...
Background
Recently, there has been an increase in interest in the quadriceps tendon (QT) as an alternative autologous graft option for primary anterior cruciate ligament (ACL) reconstruction.
Indication
Anterior cruciate ligament reconstruction in skeletally mature patients (high-risk patients for re-rupture and patients with medial instability).
Technique Description
The QT graft is harvested with a 4-cm skin incision over the superior pole of the patella. A double knife and an oscillating saw are used to obtain the QT graft with a bone block from the patella (65 mm x 10 mm graft and 15 mm bone block). Then an arthroscopy is carried out with assessment of the ACL tear and treatment of further intraarticular injuries. ACL reconstruction begins with debridement of the femoral insertion to expose the land marks. The medial portal is used for femoral tunnel drilling with the knee in more than 110° of flexion. A special portal aiming device is introduced via the anteromedial portal and a guide wire is placed in the area of the femoral anteromedial insertion. This guide wire is gradually overdrilled with various drills and dilators of increasing size. The final diameter should be 0.5 mm smaller than the diameter of the bone block of the graft to allow for press-fit fixation. Then, the tibial tunnel is drilled using a tibial drill guide leaving the tibial stump of the original ACL intact. The graft is pulled into the joint through the tibial tunnel until the bone block stops at the femoral tunnel entrance. The bone block is then pushed through the medial portal into the femoral tunnel (press-fit fixation). The tibial fixation is performed with an interference screw and optionally with an extracortical button.
Results
Prior studies with 2 years follow-up have shown that the clinical outcomes in primary and revision ACL reconstruction were not significantly different between the use of QT grafts with femoral press-fit fixation and the use of hamstring grafts with femoral suspension fixation.
Discussion/Conclusion
Quadriceps tendon bone autograft and femoral press-fit fixation provides an excellent alternative as a graft choice in ACL reconstruction. The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.
... The new ligament is placed over the tunnel layer exactly in the tibial cruciate ligament stump so that the old ligament encloses the new one. At the femoral side, the insertion was debrided only as much that the important landmarks for tunnel drilling became visible [26,31]. ...
... The follow-up time was one year after surgery, since most arthrolyses or cyclops resections have to be performed during this time due to movement complications [7]. In all patients with an arthroscopic cyclops resection, the position of the tibial and femoral bone tunnel was checked on lateral X-rays according to the quadrant method stated by Bernard and Hertel for the femur and according statements of Petersen and Zantop at the tibia [6,21,26]. According to the quadrant method, the center of the femoral tunnel should be located at between 20 and 30% of the distance t measured from the most posterior contour of the lateral femoral condyle and between 25 and 35% of the height h measured from Blumensaat's line. ...
... In all revision cases, the center of the tibial and femoral bone tunnel was located within the landmarks stated by Bernard and Hertel [6] and Petersen and Zantop [26]. ...
Background
Remnant-preserving anterior cruciate ligament reconstruction (ACLR) should have advantages for postoperative remodeling and proprioception. However, it has been suggested that the larger diameter of the graft tends to lead to impingement phenomena with a higher rate of cyclops lesions. The aim of this work was to find out whether the remnant-preserving ACLR actually leads to an increased rate of range of motion restraints compared to the remnant-sacrificing technique.
Methods
Patients, who fulfilled the inclusion criteria, were followed up for one year after surgery. The primary endpoint was arthrolysis due to extension deficit or cyclops syndrome.
Secondary outcome measures were pain (NRS), knee function (KOOS), patient satisfaction and return to sports rate.
Results
One hundred and sixty-four patients were included in the study, 60 of whom received the “remnant augmentation” procedure (group 1). In the remnant augmentation group, one cyclops resection was performed, whereas in the non-remnant augmentation group three cyclops lesion resections had to be performed (odds ratio 0.6). There was no difference between the groups in pain (NRS) and knee function (KOOS) and patient satisfaction. The return to sports rate after one year was higher in the remnant augmentation group.
Conclusions
Patients who have undergone the sparing “remnant augmentation” ACLR have no increased risk of cyclops lesion formation or extension deficit in the first year after surgery. An improvement of the proprioceptive abilities by remnant augmentation ACLR should be investigated in further studies.
Level of evidence
III (prospective cohort study).
... Studies have shown that the men and women with noncontact ACL injuries had measurements of greater lateral meniscus slopes [8]. The ACL is a band of connective tissue, however the ACL does not function as a simple band of fibers with a constant tension as the knee flexes and extends [40,47], With the differentiation of tension of the ACL in different angles, one theory for the difference in tensions is that this band can be divided into bundles [47,40]. ...
... Studies have shown that the men and women with noncontact ACL injuries had measurements of greater lateral meniscus slopes [8]. The ACL is a band of connective tissue, however the ACL does not function as a simple band of fibers with a constant tension as the knee flexes and extends [40,47], With the differentiation of tension of the ACL in different angles, one theory for the difference in tensions is that this band can be divided into bundles [47,40]. ...
... The division of the ACL into bundles is a controversial idea, many studies vary the number of bundles in the ACL [40,47]. Though the number varies study to study, most studies agree that the posterolateral and anteromedial bundle are the major functional bands of the ACL [40,47]. ...
INTRODUCTION: An increase in participation in females sports has created an increase of female athletes at risk for injuring their Anterior Cruciate Ligament(ACL)[12,21,29,44]. Traditional jumping sports have the highest rate of non contact ACL injuries, due to the use of movements of cutting, pivoting and landing on one foot[5,8,32,33,38]. ACL injuries can also be attributed to neuromuscular deficits such as the ‘Ligament Dominance Theory’, ‘Quadricep Dominance Theory’, ‘Trunk Dominance Theory’ and the ‘Leg Dominance Theory’[24,33]. The neuromuscular deficits are muscle strength, power or activation patterns that can cause an individual to have an increased risk of ACL injury[33]. Female traditional jumping sport athletes have been associated with being at a higher risk of ACL injury than their male counterparts due to anatomical, hormonal and neuromuscular differences[2,8,24,28,32,37,38,44,47]. However, female dancers trained with ballet have a lower risk of ACL injury than their female athlete counterparts, but also have a similar ACL injury to their male dancing counterparts [28,37,45,47]. METHODS: This study analyzed six papers that compared the lower body biomechanics of female traditional jumping sport athletes to female dancers trained in ballet. The results of the measurement of this study will be placed into a chart to compare the results of each study to each other, to confirm the results of the comparison between the two populations. The next part of this study will examine unused turnout angle data collected from a previous thesis performed by Ashley Tornio. The data was taken from 20 participants, 15 female traditional jumping sport athletes and 5 female dancers trained in ballet. The averages of these two groups will be compared using an f test to determine differences in the turnout capabilities of each group. RESULTS: The results of the data comparison found only six comparable measurements between the 6 papers. The papers were in agreement that female traditional jumping sport athlete had greater hip adduction moments and trunk forward flexion than female dancers trained in ballet. The papers were also in agreement that there was no statistically significant difference in the knee stiffness between the two populations. There was no consensus for the results of knee valgus angle, knee rotation, muscle activation or leg stiffness between the six papers. For the turnout angle f test, female traditional jumping sport athletes had an average turnout angle of 120.5 degrees and the female dancers trained in ballet had an average turnout angle of 141.2 degrees. It was found that the there was no statistically significant difference between the two populations at the 95% confidence level. However, there was a statistically significant difference between the two populations average turnout at a reduced confidence level of 80%. The DISCUSSION: The limiting number of studies which compare female traditional jumping sport athletes and female dancers trained in ballet, were unable to form consensus on the difference between the biomechanics of each group during a landing task. The turnout angle data was also limited in the number of participants and a valid conclusion was unable to be made determining the ability to use the turnout angle as an indicator for risk of ACL injury. There needs to be continued research on the comparison of the female traditional jumping sport athletes and female dancers trained in ballet to determine the biomechanical advantages female dancers have for protection of the ACL.
... There are two bundles of the ACL; the anteromedial bundle that resists anterior tibia translation in the knee being flexed and the posterolateral bundle that resists anterior tibia translation in the knee being extended [3]. ...
... ACL is a primary stabilizer against anterior tibial translation and had a secondary stabilizer against tibial medial and lateral rotation [3]. ...
... Since these bone tunnels are often outside the femoral insertion zone of the original ACL, they are also referred to as non-anatomical [9]. A problem with the non-anatomical tunnel position is that rotational stability is not restored as well as with an anatomical tunnel position [10,11]. The prevention of osteoarthritis is said to be better with anatomical than with non-anatomical surgical techniques [12]. ...
... Therefore, anatomical techniques for ACL reconstruction are highly recommended in a recently published consensus paper [13]. The independent drilling technique is considered a key feature of anatomical ACL reconstruction, since the femoral insertion zone of the ACL can be better reached via the medial portal than via the tibial tunnel [9,10]. The most commonly used independent drilling technique is the medial portal drilling technique [14]. ...
Purpose
Aim of this systematic review was to analyze the outcome after transphyseal ACL reconstruction in children and adolescents regarding the femoral drilling technique.
Methods
A systematic literature search was carried out in various databases on studies on transphyseal ACL reconstruction in children and adolescents. The literature search was limited to the last 20 years. Primary outcome criterion was the failure rate. Secondary outcome criteria were growth disturbances such as leg length discrepancies or deformities and clinical scores.
The present study was registered prospectively ( www.crd.york.ac.uk/PROSPERO ; CRD42022345964).
Results
A total of 22 retrospective or prospective case series (level 4 evidence) were identified that reported on transphyseal ACL reconstruction in children and adolescents. The overall failure/rupture rate after transphyseal ACL reconstruction was 11.0%. The overall ACL rupture rate of the contralateral side was 9.7%. No statistical significant difference in the failure rates between independent and transtibial drilling techniques could be detected (( p = 0.76/ p = 0.28)). Furthermore no statistical significant differences in the rate of reported growth disturbances between independent and transtibial drilling techniques were shown ( p = 0.15). The reported clinical scores at follow-up (mean follow-up 5.05 years) revealed good to very good results.
Conclusion
This systematic review demonstrates that children and adolescents have a relatively high failure rate after transpyseal ACL reconstruction without any statistically significant differences between independent or transtibial drilling techniques regarding reruptur rates or the rate of growth disturbances. The results of this systematic review warrant a comparison of both techniques for femoral tunnel drilling in a controlled randomized trial.
... In female, these distances were observed to be 9.31 ±0.33mm, 6.34 ±0.22mm and 8.59 ±0.24mm on right side while on left side these were 9.22 ±0.37mm, 6.39 ±0.28mm and 8.65 ±0.28mm respectively. These findings are comparable with previous researchers like Peterson et al. (17) and Tran TD (18). In previous studies data were not separated according to side and sex of the individual; while in the present study, measurements of both sides in both sexes were taken and analysed for more accuracy. ...
... The distances from the centre of the tibial attachment site of the ACL, the AM and the PL bundle to the RER in our study were 8.69 ±0.17 mm, 15.54 ±0.19 mm and 11.35 ±0.10 mm, respectively in male on right side. Similar observations were made by Peterson et al. (17) and Tran TD (18). ...
Objectives:
The journey of Anterior Cruciate Ligament (ACL) reconstruction surgery has long way from open surgery to arthroscopy. Therefore, the anatomical features of the ACL and its two bundles description rewarded as good outcome of procedure.
Material and methods:
Fifty fresh knees were dissected. The insertion position, length and diameter of ACL and patellar tendon length were measured and determines the range of normality according to sex and side.
Results:
The average lengths of Antero- medial (AM) and postero- lateral (PL) bundle of the ACL were 35.35 mm and 26.11mm in male on right side, respectively while 34.21mm and 25.53 mm in female. Patellar tendon length was 45.24 mm in right side of male and 43.38 mm in female obtained. The average lengths of AM and PL bundle of the ACL were 35.47 mm and 26.04 mm in male on left side, respectively while 34.23 mm and 25.38 mm in female.
Conclusion:
The length of ligaments was higher in male than female. There was strong correlation between height and length of ligaments but no correlation with age.
... The anterior cruciate ligament (ACL) is a knee ligament that runs from the medial aspect of the lateral femoral condyle through the intercondylar fossa to the medial tibial eminence [1]. Magnetic resonance imaging (MRI) is the ideal imaging method for knee evaluation and ACL injuries, which has been shown to have high sensitivity and specificity [2]. ...
... The function of the ACL is the containment of anterior translation, primarily. However, the ACL also prevents lateral rotation, varus and valgus stress, extension, and hypertension [1]. The ACL is the most commonly damaged ligament in the knee, with 100,000 to 200,000 injuries occurring each year in the United States [4]. ...
Background
Anterior cruciate ligament (ACL) injuries have been increasing significantly over time. The relationship between the ACL injury and the knee joint structures is poorly understood. The purpose of this study is to examine whether the measurements of different structures in the knee joint are linked with ACL injury in affected patients.
Methods
This retrospective case–control study included patients who suffered from ACL tears and underwent magnetic resonance imaging (MRI). A control group of patients with no knee pathologies on MRI was included. Fourteen knee variables, including lateral meniscus (LM) posterior horn height, length, depth, and volume; medial meniscus (MM) posterior horn height, length, depth, and volume; lateral and medial (MFC) femoral condyle sphere diameter; lateral and medial tibial plateau length; and patella tendon horizontal and vertical diameter, were collected. A multivariate logistic regression including LM posterior horn depth, MM posterior horn length, MM volume, MFC sphere diameter, and patella tendon horizontal diameter and receiver operating characteristic curve, was used to compare the two groups.
Results
A total of 85 patients were included in our study; 54 suffered from ACL injuries and 31 as a control group with normal knee MRI. Logistic regression revealed that increased LM posterior horn depth (OR = 1.27; 95% CI = 1.03–1.56; p = 0.028), decreased MM posterior horn length (OR = 0.71; 95% CI = 0.55–0.93; p = 0.013), and MFC sphere diameter (OR = 1.20; 95% CI = 1.01–1.43; p = 0.035) were independent risk factors for ACL rupture. The MFC sphere diameter yielded the highest area under the curve: 0.747 (95% CI, 0.632–0.862). No difference was found in the other measurements between the two groups.
Conclusions
Concerning the difference in anatomical variations, the lateral meniscus posterior horn depth and medial femoral condyle sphere diameter were higher, while medial meniscus posterior horn length was lower in patients with an ACL injury. These structural knee measurements could have a possible increase in the likelihood of sustaining an ACL injury and can be used by clinicians to predict ACL injury.
... The AM bundle is tight in flexion, and the PL bundle is tight in extension. 5 The incidence of ACL tear in the general population has been estimated to be between 30 to 78 per 100,000 people. 6,7 The treatment of an ACL tear is one of the most frequently studied and updated treatments in the orthopaedic literature. ...
... The AM bundle is tight in flexion, and the PL bundle is tight in extension. 5 Ideally both bundle reconstruction is needed for a good outcome of ACL reconstruction surgery. Muneta et al. 15 introduced the double-bundle technique in which 2 tunnels were made in both the femur and the tibia to reconstruct both bundles and to increase footprint coverage. ...
The anterior cruciate ligament (ACL) consists of an anteromedial bundle and a posterolateral bundle giving anteroposterior and rotational stability. It’s one of the most commonly injured ligaments and also one of the most commonly performed arthroscopic procedures. Management of ACL injuries is one of the most frequently studied subjects in the literature. Surgical management of ACL injuries varies from extraarticular tenodesis to arthroscopic transtibial reconstruction to double-bundle reconstruction to anatomic single-bundle reconstruction. Although double-bundle ACL reconstruction gives more rotational stability than anatomic single-bundle, functional outcome of both are the same, but the complication rates are much higher for double-bundle reconstruction. Hence, anatomic single-bundle ACL reconstruction has gained popularity. The femoral and tibial footprint of the ACL varies in shape and size; it can be oval, elliptical, rectangular, C-shape, and more. But all available ACL reconstruction techniques prepare a circular tunnel; hence, the footprint coverage of the native ACL is maximum after double-bundle reconstruction and less after anatomic single-bundle reconstruction. So, to have the benefit of double-bundle reconstruction with a single tunnel, we propose our technique of a single-tunnel double-bundle-like effect, with the footprint enhancing ACL reconstruction using our newly designed tunnel dilators.
... 15,25,26 The bundles serve unique roles throughout the entirety of the knee range of motion (ROM)dthe AM bundle is tight in flexion and is primarily responsible for restraining anterior tibial translation, whereas the PL bundle is tight in extension and more responsible for rotational stability. 27,28 The bundles change alignment as the knee moves from extension to flexion. In full extension (0 ), the 2 bundles are oriented vertically/in parallel (Fig 4a). ...
... As the knee flexes to 90 , the femoral AM bundle insertion site rotates posteroinferiorly while the PL bundle site rotates anterosuperiorly. 28 Consequently, the 2 bundles cross around each other into a horizontal orientation. ...
Despite advancements in our understanding of anterior cruciate ligament (ACL) injury prevention and nonsurgical management, ACL reconstruction continues to occur at an alarming rate. Among athletic patients, individuals participating in basketball, soccer, and football have the highest incidence of ACL injury, often requiring surgical intervention. To ensure the optimal treatment strategy for return to sport and prevention of secondary graft re-tear, it is important to tailor to the specific demands of the injured athlete and apply evidence-based best practices and rehabilitation principles. The purpose of this review is to provide readers with a brief background regarding ACL injuries, a focused review of clinical outcome studies after ACL reconstruction, and an updated framework with expert-guided recommendations for postoperative rehabilitation and return to sporting activity. Currently, there is no gold standard for rehabilitation after ACL reconstruction, highlighting the need for robust studies evaluating the best modalities for athlete rehabilitation, as well as determining the efficacy of new tools for improving therapy including blood flow restriction therapy and neuromuscular electrical stimulation. Based on clinical experience, a renewed focus on objective, criteria-based milestones may maximize the ability of return to preinjury levels of athletic function.
... The tibial insertion shows an oval, triangular shape with a mean diameter of 11-17 mm. From the origin of the lateral femoral condyle, the fibers of the ACL run obliquely to its insertion at the medial and lateral tibial spine and the area in between [3]. Graft choice for anterior cruciate ligament (ACL) reconstruction remains a controversial issue, but most surgeons are using autografts and, especially, the bone-patellar tendon-bone (BPTB) graft and the hamstring tendon autograft (HTA). ...
... A distinct amount of ACL fibers appear in approximately the 8th week after gestation. At this time, the fibroblasts within the ligament are already aligned to the axis of strain of the ACL (7,8) . ...
... The ACL is a hypocellular and weakly vascularized connective tissue that is mostly made up of aligned type 1 collagen fibrils and surrounded by fibroblasts, elastin, and glycoproteins as well as glycosaminoglycans. When the knee is stretched, the posterolateral bundle will get tight and the anteromedial bundle will relax depending on the viscoelastic and biomechanical properties of the ACL, which are controlled mainly by the collagen fibrils (Petersen and Zantop, 2007). The ACL is positioned diagonally at the center of the knee and a tear or rupture of the collagen fibrils of the ACL results in structural and morphological changes mainly in the form of a variation in the diameter distribution of collagen fibrils and a reduction in the mean diameter (Ochi et al., 1999;Beisbayeva et al., 2021). ...
Reconstructed ACL cannot completely restore its functions due to absence of physiologically viable environment for optimal biomaterial-cell interaction. Currently available procedures only mechanically attach grafts to bone without any biological integration. How the ACL cells perform this biological attachment is not fully understood partly due to the absence of appropriate environment to test cell behavior both in vitro and in vivo . Availability of biomimetic models would enable the scientists to better explore the behavior of cells at health and during tissue healing. In this study, it is hypothesized that the collagen fibril diameter distribution in rat ACL changes from a bimodal distribution in the healthy ACL to a unimodal distribution after injury, and that this change can be mimicked in synthetic nanofiber-based constructs. This hypothesis was tested by first creating an injured rat ACL model by applying a mechanical tensile force to the healthy ACL tissue until rupture. Secondly, the collagen fibril diameter distributions of healthy and injured ACL tissue were determined, and polycaprolactone (PCL) constructs were created to mimic the distributions of collagen fibrils in healthy and injured tissues. Findings reveal that the fiber diameter distribution of aligned bimodal PCL constructs were similar to that of the collagen fibrils in native ACL tissue. This study is significant because suggested bimodal and unimodal fibrous model constructs, respectively, represent a healthy and injured tissue environment and the behavior of ACL cells cultured on these constructs may provide significant input on ACL regeneration mechanism.
... The ACL consists of two bundles, the anteromedial bundle (AMB) and the posterolateral bundle (PLB). It shows complex biomechanical characteristics with a tightened AMB and a relatively relaxed PLB in flexion and approximately contrary tension-settings in extension [3], which means that different parts within the ligament change their length and tension during motion [2]. The ACL mainly contains of collagen fibers and its vascularization is provided by branches of the middle genicular artery [4]. ...
The anterior cruciate ligament (ACL) plays a significant role in knee stability, protects the joint under multiple loading conditions and shows complex biomechanics. Beside mechanical stability, the ACL seems to play a crucial role in proprioception, and it is well known, that ACL injuries can cause functional deficits due to decreased proprioception. However, the mechanism of proprioception is not completely understood yet. In this context, primary cilia (PC), which play a significant role in the signaling between the intra- and extracellular space, could be of interest. However, until today, primary cilia are not yet described in human ACL. In total, seven human ACL’s underwent transmission electron-microscopical examination. Three cadaveric ACL’s and four freshly injured ACL’s were examined. Single cells of each ACL were examined regarding the presence of axonemes or basal bodies, which represent components of a PC. In total, 276 cells of the cadaveric ACL’s and 180 cells of the injured ACL’s were examined.
Basal bodies could be detected in three of the four specimens of the injured ACL’s as well as in one of the three cadaveric ACL’s, resulting in a mean positivity of 2.54% in the cadaveric group and 2.78% in the injured group. In case of PC-presence, only one PC per cell could be detected. No statistically significant difference regarding the frequency could be detected between both groups
In this pilot-study, we present for the first time an ultrastructural study of human ACLs with respect to the occurrence of PC and any structural and morphological features of these complex and dynamic cell organelles. PCs are present in almost all non-hematopoietic tissues of the human body. However, there are different reports on the number, incidence, orientation, and morphology of these cell organelles in the respective tissues. Compared to other tissues and ligaments of other species, we found a significantly lower rate of PC positive cells. This observation might represent a tissue-specific characteristic of ACL tissue. However, our observations need to be explored in more detail in further studies.
... It has been a long-held belief that the human ACL has two main functional bundles (anteromedial and posterolateral bundles). 57 This however has been recently revisited where some have described additional bundles or contend that the ACL is actually a single ribbon-like structure. [58][59][60][61] Regardless of the number of bundles, it is likely that tendon graft reconstruction of the ACL likely does not recapture all of the exquisite detail of the native ACL. ...
Anterior cruciate ligament (ACL) injuries are common knee ligament injuries. While generally successful, ACL reconstruction that uses a tendon graft to stabilize the knee is still associated with a notable percentage of failures and long‐term morbidities. Preclinical research that uses small laboratory species (i.e., mice, rats, rabbits) to model ACL reconstruction are important to evaluate factors that can impact graft incorporation or post‐traumatic OA after ACL reconstruction. Small animal ACL reconstruction models are also used for proof‐of‐concept studies for development of emerging biologic strategies aimed at improving ACL reconstruction healing. The objective of this review is to provide an overview on the use of common small animal laboratory species to model ACL reconstruction. The review includes a discussion on comparative knee anatomy, technical considerations including types of tendon grafts employed amongst the small laboratory species (i.e., mice rats, rabbits), and common laboratory evaluative methods used to study healing and outcomes after ACL reconstruction in small laboratory animals. The review will also highlight common research questions addressed with small animal models of ACL reconstruction. This article is protected by copyright. All rights reserved.
... To the best of our knowledge, the structural relationship between the ACL and articular cartilage has not yet been reported. Conventionally, it was believed that the tibial side of ACL did not attach to the articular cartilage, and only its attachment to the bone surface was analyzed 7,[10][11][12][13][14]16,20,[22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] . In contrast, several studies have reported the close relationship of the tibial side of ACL with LM, describing it as an "overlap, " "adjoin, " or "adjacent" 7,11,12,14-17 . ...
Knowledge of the anatomy of the anterior cruciate ligament (ACL) is important to understand the function and pathology of the knee joint. However, on the tibial side of ACL, its structural relationships with the articular cartilage and lateral meniscus remain unclear. Furthermore, conventional research methods are limited to analyzing the bone attachments. We provide a comprehensive, three-dimensional anatomical description of the tibial side of the ACL that questions the principle that “a ligament is necessarily a structure connecting a bone to another bone.” In our study, 11 knees from 6 cadavers were used for macroscopic anatomical examinations, serial-section histological analyses, and three-dimensional reconstructions. The attachments of the tibial side of ACL consisted of attachments to the bone (102.6 ± 27.5 mm²), articular cartilage (40.9 ± 13.6 mm²), and lateral meniscus (6.5 ± 4.6 mm²), suggesting that the ACL has close structural relationships with the articular cartilage and lateral meniscus. Our study demonstrates that the tibial side of the ACL is not attached to the bone surface only and provides new perspectives on ligamentous attachments. Considering its attachment to the articular cartilage would enable more accurate functional evaluations of the mechanical tensioning of the ACL.
... The ACL is the primary stabilizer against anterior tibial translation and internal tibial rotation [26]. Therefore, in the case of an ACL rupture, anterior and rotational instability can occur, which leads to functional impairment of the patient. ...
PurposeThe aim of this consensus project was to validate which endogenous and exogenous factors contribute to the development of post-traumatic osteoarthritis and to what extent ACL (anterior cruciate ligament) reconstruction can prevent secondary damage to the knee joint. Based on these findings, an algorithm for the management after ACL rupture should be established.Methods
The consensus project was initiated by the Ligament Injuries Committee of the German Knee Society (Deutsche Kniegesellschaft, DKG). A modified Delphi process was used to answer scientific questions. This process was based on key topic complexes previously formed during an initial face-to-face meeting of the steering group with the expert group. For each key topic, a comprehensive review of available literature was performed by the steering group. The results of the literature review were sent to the rating group with the option to give anonymous comments until a final consensus voting was performed. Consensus was defined a-priori as eighty percent agreement.ResultsOf the 17 final statements, 15 achieved consensus, and 2 have not reached consensus. Results of the consensus were summarized in an algorithm for the management after ACL rupture (infographic/Fig. 2).Conclusion
This consensus process has shown that the development of post-traumatic osteoarthritis is a complex multifactorial process. Exogenous (primary and secondary meniscus lesions) and endogenous factors (varus deformity) play a decisive role. Due to the complex interplay of these factors, an ACL reconstruction cannot always halt post-traumatic osteoarthritis of the knee. However, there is evidence that ACL reconstruction can prevent secondary joint damage such as meniscus lesions and that the success of meniscus repair is higher with simultaneous ACL reconstruction. Therefore, we recommend ACL reconstruction in case of a combined injury of the ACL and a meniscus lesion which is suitable for repair.Level of evidenceLevel V.
... The antero-medial (AM) bundle, taut in flexion, is primarily responsible for restraining anterior tibial translation (anterior drawer test). The postero-lateral (PL) bundle on the other-hand, is taut in extension and is primarily responsible for rotational stability (pivot shift test) [6]. ...
Background
The incidence of anterior cruciate ligament (ACL) injuries represents a large burden of knee injuries in both the general and sporting populations, often requiring surgical intervention. Although there is much research on complete ACL tears including outcomes and indications for surgery, little is known about the short- and long-term outcomes of non-operative, physiotherapy led intervention in partial ACL tears. The primary aim of this study was to evaluate studies looking at the effectiveness of physiotherapy led interventions in improving pain and function in young and middle-aged adults with partial ACL tears. Additionally, the secondary aim was to evaluate the completeness of exercise prescription in randomised trials for physiotherapy led interventions in the management in partial ACL tears.
Methods
A comprehensive and systematic search was performed on six databases ( Medline, CINAHL, EMBASE, PEDro, Scopus , SPORTDiscus and Cochrane). The search strategy consisted of two main concepts: (i) partial ACL tears, and (ii) non-operative management. 7,587 papers were identified by the search. After screening of eligible articles by two independent reviewers, 2 randomised studies were included for analysis. The same two reviewers assessed the completeness of reporting using the Toigio and Boutellier mechanobiological exercise descriptions and Template for Intervention Description and Replication (TIDieR) checklist. Group mean standard deviations (SD) for the main outcomes was extracted from both papers for analysis. Prospero Registration Number: CRD42020179892.
Results
The search strategy identified two studies; one looking at Tai Chi and the other Pilates. The analysis indicated that Tai Chi was significant in reducing pain scores and both Tai Chi and Pilates were found to increase Muscle Peak Torque Strength (MPTS) at 180 degrees. Furthermore, Tai Chi showed a significant increase in proprioception.
Conclusions
Physiotherapy led interventions such as Pilates, and Tai Chi may improve pain, proprioception and strength in young and middle-aged adults with partial ACL tears, however full scale, high-quality randomised studies are required with long term outcomes recorded.
... The ACL is placed at the midpoint of the knee. ACL functionality is fundamental as it prevents anterior sliding of the tibia relative to the femur, excessive tibial medial and lateral rotation and withstands varus and valgus stresses (Petersen and Zantop, 2007). It is composed of two bundles, the antero -medial and postero -lateral bundle and extends from the lateral femoral intercondylar notch towards the tibial plateau and the intercondyloid eminence (Duthon et al., 2006). ...
The Anterior Cruciate Ligament rupture is a very common knee injury during sport activities. Landing after a jump is one of the most prominent human body movement scenarios that can lead to such an injury. The landing - related Anterior Cruciate Ligament (ACL) injury risk factors have been in the spotlight of research interest. Computational modeling and simulation allows for studying musculoskeletal systems. Specifically, predictive simulation approaches offer researchers the opportunity to predict and study new biological motions without the demands of acquiring experimental data. In this thesis, we present a pipeline that aims to predict and identify key parameters of interest that are related to ACL injury during single - leg landings. We examined the following conditions of single - leg landing: a) initial landing height, b) hip internal and external rotation, c) lumbar forward - backward leaning, d) lumbar medial - lateral bending, e) lumbar internal - external rotation, f) muscle forces permutations and g) effort goal weight. Identified on related research studies, we evaluated the following risk factors: vertical Ground Reaction Force, knee joint Anterior force, knee joint Abduction moment, and Quadricep / Hamstring force ratio. Our study clearly demonstrated that ACL injury is a rather complicated mechanism with many associated risk factors which are evidently correlated. Nevertheless, our results were mostly in agreement with other research studies regarding the ACL risk factors. Despite the limitations regarding the adopted modeling assumptions, our pipeline clearly showcased promising potential of predictive simulations to evaluate different aspects of complicated phenomena, such as the ACL injury.
... This illustrates the dynamic nature of the ACL with a changing stress distribution throughout the physiologic range-of-motion. Taking the distinct femoral and tibial insertion sites of each bundle into account, it becomes evident that the AM and PL bundles act differently but are synergistic [6,16]. The AM bundle acts as the primary restraint against anterior tibial translation (ATT) in higher exion angles, while the PL bundle acts as the primary restraint against ATT in lower exion angles and against combined rotatory loads [6]. ...
To better care for patients with anterior cruciate ligament (ACL) injuries, surgeons and researchers must familiarize themselves with the anatomy and biomechanics of the ACL. The primary function of the ACL is to provide a restraint to anterior tibial translation, but it is also important in maintaining rotatory knee stability. Injury to the ACL leads to alterations in knee kinematics and increases the risk of injury to other structures in the knee, including the menisci, cartilage, and surrounding soft tissues. Operative intervention for ACL injuries has been advocated to restore knee stability. When performing an ACL reconstruction, the graft choice, including autograft and allograft, is an important component of surgical decision making, each with their own unique advantages and disadvantages. This chapter aims to discuss the relevant anatomy and biomechanics of the ACL in an intact knee, describe the effects of ACL deficiency on knee kinematics, and review graft options for surgical planning.
... Based on macroscopic observations, the femoral ACL insertion point is relatively large and oval in shape at the medial surface of the lateral femoral condyle; it is located posterior to the lateral intercondylar ridge, which is also known as the resident's ridge [4][5][6][7][8]. The ACL fibers are aligned parallel to the intercondylar roof in the fully extended position; the posterior portion of the femoral attachment consists of fanlike extension fibers that appear to be thin and coarse compared to the midsubstance fibers [8]. ...
Background
This study compared the failure load of the femoral insertion site of the anterior cruciate ligament between different portions and knee flexion angles.
Methods
In total, 87 fresh-frozen, porcine knees were used in this study. Three knees were used for histological evaluation; the remaining 84 knees were randomly divided into 4 groups: anterior anteromedial bundle, posterior anteromedial bundle, anterior posterolateral bundle, and posterior posterolateral bundle groups ( n =21 per group). The anterior cruciate ligament femoral insertion site was divided into these four areas and excised, leaving a 3-mm square attachment in the center of each bundle. Tibia-anterior cruciate ligament-femur complexes were placed in a material testing machine at 30°, 120°, and 150° of knee flexion ( n =7), and the failure load for each portion was measured under anterior tibial loading (0.33 mm/s).
Results
Histological study showed that the anterior cruciate ligament femoral insertion site consisted of direct and indirect insertions. Comparison of the failure load between the knee flexion angles revealed that all the failure loads decreased with knee flexion; significant decreases were observed in the failure load between 30 and 150° knee flexion in the posterior anteromedial bundle and posterior posterolateral bundle groups. Comparison of the failure load according to different portions revealed a significant difference between the anteromedial and posterolateral bundle groups at 150° of knee flexion, but no significant difference among the groups at 30° of flexion.
Conclusions
Although the failure load of the posterior portion decreased significantly in the knee flexion position, it (mainly consisting of indirect insertion) plays a significant role against anterior tibial load in the knee extension position; this appears to be related to the characteristics of the insertion site. Reflecting the complex structure and function of the ACL, this study showed that the failure load of the femoral insertion site varies with differences in positions and knee flexion angles.
... On the medial wall of the lateral condyle, the lateral intercondylar ridge (LIR, Figure 1A) is referred to as the anterior border of the ACL in knee flexion. This ridge is also called "resident's ridge" because inexperienced surgeons can mistake it for the posterior edge of the lateral femoral condyle, leading to incorrect anterior tunnel placement and in consequence to premature failures of ACL reconstruction (Bicer et al., 2010;Ferretti et al., 2007;Hutchinson & Ash, 2003;Petersen & Zantop, 2007;Sasaki et al., 2012;Shino et al., 2010;Zauleck et al., 2014;Ziegler et al., 2011). The lateral bifurcate ridge (LBR) subdivides the footprint of the ACL into its two bundles (Forsythe et al., 2010;Fu & Jordan, 2007;Kopf et al., 2009;van Eck, Morse, Lesniak, et al., 2010;van Eck, Schreiber, Liu, & Fu, 2010;van Eck, Schreiber, Mejia, et al., 2010;Zauleck et al., 2014;Ziegler et al., 2011). ...
The intercondylar fossa (“intercondylar notch”, IN) is a groove at the distal end of the femur, housing important stabilizing structures: cruciate ligaments and meniscofemoral ligaments. As the risk for injury to these structures correlates with changes to the IN, exact knowledge of its morphology, possible physiological and pathological changes and different approaches for evaluating it are important. The divergent ways of assessing the IN and the corresponding measurement methods have led to various descriptions of its possible shapes. Ridges at the medial and lateral wall are considered clinically important because they can help with orientation during arthroscopy, whereas ridges at the osteochondral border could affect the risk of ligament injury. Changes related to aging and sex differences have been documented, further emphasizing the importance of individual assessment of the knee joint. Overall, it is of the utmost importance to remember the interactions between the osseous housing and the structures within.
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... The surgeon used an anteromedial portal aimer (Karl Storz) to place a Kirschner wire (K-wire) into the center of the anatomic ACL insertion (landmarks for femoral tunnel placement are the intercondylar line and the cartilage border). 7,26 The position of the K-wire was double-checked via the anteromedial portal. 7,24 Then, in a stepwise manner, the femoral tunnel was drilled until the correct size (graft diameter, 1 mm) was achieved with a depth of 20 to 25 mm. ...
Background:
The choice of graft in anterior cruciate ligament (ACL) reconstruction is still under discussion. The hamstrings are currently the most used grafts for primary ACL reconstruction in Europe. However, increased interest has arisen in the quadriceps tendon (QT) as an alternative autologous graft option for primary ACL reconstruction.
Purpose:
To evaluate knee stability and the subjective outcome after ACL reconstruction using either autologous QT graft in implant-free femoral press-fit fixation technique or semitendinosus tendon (ST) graft.
Study design:
Cohort study; Level of evidence, 2.
Methods:
We evaluated 50 patients who underwent ACL reconstruction, including 25 patients who received autologous ipsilateral QT graft (QT group) and 25 patients who received the ipsilateral ST graft (ST group). The follow-up for this prospective comparative study was at least 2 years after surgery, comprising KT-1000 arthrometer testing, pivot-shift test, Knee injury and Osteoarthritis Outcome Score (KOOS), Lysholm score, and rerupture rate.
Results:
The mean patient age was 31.72 years (9 women, 16 men) in the QT group and 32.08 years (13 women, 12 men) in the ST group. The mean ± standard deviation postoperative side-to-side difference assessed using KT-1000 arthrometer was 1.56 ± 1.56 mm for the QT group and 1.64 ± 1.41 mm for the ST group, with no significant difference. No significant difference was found on any of the KOOS subscale scores (P = .694) or the Lysholm score (P = .682). No rerupture or positive pivot-shift test occurred during follow-up. No difference was found in donor-site morbidity between the study groups.
Conclusion:
Clinical outcomes were not significantly different between QT and ST grafts in the current study. Thus, the QT may serve as a good alternative graft for primary ACL reconstruction.
... Anatomically, the ACL is composed of two functionally distinct bundles, namely the anteromedial (AM) and posterolateral (PL) bundles that shorten with increasing knee flexion and elongate with extension and exhibit reciprocal tensions [7], [8]. The concept of double-bundle (DB) ACLR was hence borne with the idea that restoring the normal anatomy of the ACL with two bundles will result in improved restoration of normal knee biomechanics and rotational stability [9]. ...
BACKGROUND: Double-bundle (DB) anterior cruciate ligament reconstruction (ACLR) has been known to result in better functional outcomes, joint stability, and lower revision rates compared to single-bundle (SB) ACLR. However, given the increased invasiveness and damage to the surrounding tissue area, it is proposed that it may be associated with increased pain. AIM: This review aims to gather all studies and literature that reported pain as an outcome when comparing SB versus DB ACLR. METHODS: Literature searching was conducted across seven search engines for studies reporting pain as an outcome and comparing SB versus DB ACLR. RESULTS: Eight studies met the eligibility criteria and were included in the study. Overall, the studies show variable findings regarding pain in DB compared to SB ACLR, with the only statistically significant results from two studies indicating that DB ACLR is associated with more pain than SB ACLR. CONCLUSION: Based on the limited evidence available, no conclusions can be made regarding the pain experienced between people receiving either procedure. This constitutes a need for additional studies with increased follow-up time periods, larger sample size, and better study design.
... However, while doing so, all the studies based on skin marker-based motion data confront a major sources of error, commonly referred to as Soft Tissue Artifact (STA) as already mentioned in Chapter 1 (subsection 1.3.2). STA is known to be dependent on subjects, performed tasks and marker configuration (Petersen and Zantop, 2007). If not compensated for, STA can lead to biased outcomes resulted from bone interference while assessing skeletal kinematics (Dyrby and Andriacchi, 2004;Benoit et al., 2006;Stagni et al., 2005). ...
Musculoskeletal disorder of the lower limb is one of the most common health burdens that may lead to functional impairment in an individual. Although various operative management options are available, there seems no unanimity on a particular procedure that serves the best. To objectively assess disorders and effectively plan surgeries, it is essential to understand lower limb biomechanics under physiological loading conditions. With that motivation, this PhD aims to develop a comprehensive finite element based musculoskeletal modeling framework of the lower limb. The first phase of the PhD focuses on the development and evaluation of subject-specific finite element models under passive flexion. Novel approaches are proposed and evaluated for fast model development focusing on geometry and ligament properties. In the second phase, a novel finite element based approach for soft tissue artifact compensation is proposed and evaluated. This contribution allowed to effectively compensate for soft tissue artifact in motion analysis by taking subject specificity into account. The third phase of the PhD is dedicated to clinical application, where the utility of the biplanar X-ray system in evaluating Total Knee Arthroplasty implant alignment is briefly explored. Overall, this PhD may help to accurately estimate and understand lower limb biomechanics under clinically relevant loading conditions, and bring the model a step closer to clinical routine.
... AM and PL bundles have different functions for knee stability. The main function of the AM bundle was considered to prevent anterior tibial translation, and that of the PL bundle was considered to maintain rotational stability [30,36]. Because of the presence of tibial tunnel coalition in the ACL-reconstructed knees, the posterior wall of the AM bone tunnel disappeared, resulting in an increase of tibial anterior subluxation, and the anterior wall of the PL bone tunnel collapsed and affected rotational instability. ...
PurposeTo evaluate the effect of tibial tunnel coalition on knee rotatory laxity and clinical outcomes after double-bundle (DB) anterior cruciate ligament (ACL) reconstruction.Methods
Forty-one patients who underwent anatomic DB ACL reconstruction were included prospectively. Three-dimensional computed tomography of the knee joint was obtained at approximately 1 year postoperatively to determine if tunnel coalition occurred. After excluding seven cases of femoral tunnel coalition, two groups were established based on the existence of a tibial tunnel coalition. The pivot-shift test was quantitatively evaluated on the basis of tibial acceleration preoperatively and at 1 year postoperatively. Two subjective scores, the International Knee Documentation Committee (IKDC) subjective and Lysholm scores, were also collected. The pivot-shift measurement and subjective scores were compared between the ACL-reconstructed knees with and without tibial tunnel coalition. The independent t test, Pearson’s chi-square test, and Student t tests were used in data analysis.ResultsTwenty-one knees had tibial tunnel coalition (group C), whereas 13 knees did not have tunnel coalition(group N). Pivot-shift was significantly diminished postoperatively in both groups on the basis of the clinical examination and quantitative evaluations (p < 0.05). However, there was a small but significant difference in tibial acceleration demonstrating larger pivot-shift in group C (1.0 ± 0.6 m/s2) than in group N (0.5 ± 0.3 m/s2, p < 0.05). No significant difference was observed in the IKDC subjective and Lysholm scores (both n.s.).Conclusion
When the tibial tunnel coalition occurs after DB ACL reconstruction, knee rotatory laxity may not be restored in ACL-reconstructed knees, as expected in those without tunnel coalition. It is recommended that two tibial tunnels should be created separately when performing DB-ACL reconstruction to achieve better control of rotatory knee laxity.Level of evidenceIII.
... The purpose of the performed static analyses is to determine the state of stresses in the CORA area for the uniplane opening osteotomies, taking into account the studied parameteres, namely: X1the position of the cutting point relative to the corresponding tibial plateau ( Figure 2a) and X2-the value of the required correction angle (Figure 2b). The characteristics of the materials necessary for performing these analyses resulted from the previously conducted bibliographic study [30][31][32][33][34][35][36][37][38][39][40]. The values for the healthy mature bone, as summarized in [41], are the following: Density-1.6 to 1.9 g/cm 3 for the cortical bone, 0.2 to 1 g/cm 3 for the trabecular bone. ...
This paper provides an analysis from a biomechanical perspective of the medial opening wedge high tibial osteotomy surgery, a medical procedure commonly used in treating knee osteoarthritis. The aim of this research is to improve the analysed surgical strategy by establishing optimal values for several very important parameters for the geometric planning of this type of surgical intervention. The research methods used are numerical and experimental. We used finite element, a numerical method used to study the intraoperative behavior of the CORA area for different positions of the initiation point of the cut of the osteotomy plane and for different correction angles. We also used an experimental method in order to determine the maximum force which causes the occurrence of cracks or microcracks in the CORA area. This helped us to determine the stresses, the maximum forces, and the force-displacement variations in the hinge area, elements that allowed us to identify the optimal geometric parameters for planning the surgery.
... Hlavnou funkciou predného krížneho väzu je brániť predo-zadnému posunu tibie voči femuru tzv. translačnému pohybu (22). Predný krížny väz tiež zabraňuje nadmernému rotačnému pohybu, a tiež zabraňuje rotačnej laxicite (19). ...
Anterior cruciate ligament (ACL) rupture is one of the most common traumatic injuries of the knee joint. Acute knee injury is often characterized by pain and the typical accompanying rupture sound. The injured person often feels pain in the knee, with swelling, the movement is painful in the full range of motion. The most commonly used test procedures for rupture include Lachman test, pivot shift test, anterior drawer and lever sign test. This review includes a description of individual tests and the diagnostic value of examination after the ACL rupture. The sensitivity and specificity of the lever sign test was 0.92-1.00, the specificity was 0.94-1.00. The anterior drawer testing reported sensitivity values ranged from 0.18 to 0.92 and specificity values ranged from 0.78 to 0.98. The sensitivity and specificity of the pivot shift test ranged from 0.18 to 0.48 and the specificity from 0.90 to 0.99. The sensitivity and specificity of the Lachman test were 0.63-0.93 and the specificity was 0.55-0.99. The lever sign test, the pivot shift test, the anterior drawer test and the Lachman test are valid parts of the anterior cruciate ligament examination with respect to the prediction of anterior cruciate ligament rupture using Magnetic Resonance Imaging and arthroscopy. Key words: rupture ligamentum cruciatum anterius, test maneuvers, lever sign test, pivot shift test, anterior drawer, Lachman test.
... With the increase in flexion angle, the posterolateral bundle gradually relaxed and the anteromedial bundle gradually tensed. 32 The results of this study were consistent with this conclusion. In addition, stress concentration on the anteromedial bundle increased more sharply with the increase in flexion angle, which means that the anteromedial bundle of the ACL was more easily damaged at high flexion. ...
The use of dynamic finite element analysis to investigate the biomechanical behavior of the knee joint is mainly based on movement of the joint. Challenges are associated with simulation of knee joint flexion-extension activity. This study investigated changes in the length and stress state of ligaments during lunge with a displacement controlled finite element analysis of the knee joint based on in vivo fluoroscopic kinematic data. The geometric center axis (GCA) was used to represent knee kinematics to quantify femoral motion relative to the tibia. Because the GCA was considered as a functional flexion axis, 2 degrees of freedom could be reduced. Published data on the in vivo fluoroscopic kinematic features of the GCA were used to establish the equations for degrees of freedom. Data for 4 degrees of freedom were obtained simultaneously at every 5° of knee flexion. Displacement and rotation were applied to the femur and tibia to produce relative displacement, and the elongation and stress state of the knee ligaments were computed. The predictions confirmed that lunge affected the biomechanical behavior of ligaments. Displacement controlled finite element analysis of knee flexion can be simulated on the basis of fluoroscopic kinematic data to achieve physiologic movement. [Orthopedics. 2021;44(x):xx-xx.].
Background
Following anterior cruciate ligament (ACL) tears, both repair and reconstruction may be performed to restore joint biomechanics and proprioception. The present study compared joint laxity, patient-reported outcome measures (PROMs), and rate of failure following primary repair versus reconstruction for ACL ruptures.
Methods
This meta-analysis followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Pubmed, Google scholar, Embase, and Web of Science were accessed in September 2022. All the clinical investigations comparing repair versus reconstruction for primary ACL tears were accessed. Studies reporting data on multiple ligament injuries settings were not eligible.
Results
Data from eight articles (708 procedures) were collected. The mean length of the follow-up was 67.3 ± 119.4 months. The mean age of the patients was 27.1 ± 5.7 years. Thirty-six percent (255 of 708 patients) were women. The mean body mass index (BMI) was 24.3 ± 1.1 kg/m ² . The mean time span from injury to surgery was 36.2 ± 32.3 months. There was comparability at baseline with regards to instrumental laxity, Lachman test, International Knee Document Committee (IKDC), and Tegner Scale ( P > 0.1). Similarity between ACL reconstruction and repair was found in IKDC ( P = 0.2) and visual analog scale (VAS) satisfaction ( P = 0.7). The repair group demonstrated greater mean laxity ( P = 0.0005) and greater rate of failure ( P = 0.004).
Conclusion
ACL reconstruction may yield greater joint stability and lower rate of failure compared with surgical repair. Similarity was found in PROMs.
Level of evidence
III
Background: The knee is one of the complex joints in the human body and consists of several internal structures that may lead to the emergence of symptoms of knee injuries [1]. The anterior cruciate ligament, or ACL, is one of the major ligaments of the knee that is located in the middle of the knee and runs from the femur (thigh bone) to the tibia (shin bone). It prevents the tibia from sliding out in front of the femur. Together with posterior cruciate ligament (PCL) it provides rotational stability to the knee [2]. In the case of ACL injuries of the knee, magnetic resonance imaging (MRI) is used to diagnose the affected knee. From this point of view, this study aims to identify the sites of ACL tears and evaluate the role of magnetic resonance imaging (MRI) in the diagnosis of Anterior Cruciate Ligament (ACL) tears. Materials and Methods: This study was conducted at the Department of Radiological Diagnostics of Medical Services, Abu Dhabi Police, United Arab Emirates. After getting the institutional approval, the study sample was selected from those with knee injuries. Socio-demographic information about these patients such as gender, age, etc. was recorded. The study sample included 150 patients (113 males and 37 females), their ages ranged between 17 and 52 years, with a mean age of 25 years, and all the patients underwent an initial diagnosis of anterior cruciate ligament injuries. MRI of the knee joint was performed for all cases using different MRI techniques. Results: MRI results confirmed that among the 155 patients, 68% had an ACL tear (89.33% complete tear, 10.67% partial tear), while 32% had no ACL tear. Also, the prevalence of the location of an ACL tear distributed in the femoral end of the knee (62%), the mid third of the knee (14%) and the tibial end (23%). Conclusion: MRI findings have proven to be more effective in assessing complete ACL tear, while the assessment of partial tear requires the use of more developed MRI techniques. All cases of ....
Knowledge of anatomy is important for understanding the knee with capsular ligament structures, their biomechanical properties and their influence on joint kinematics. Therefore, this first chapter is a guide through the main anatomical structures of the knee ligament apparatus, as well as their biomechanical and articulated kinematic tasks, and explains the latest findings and understanding. The anterior cruciate ligament is the primary stabilizer of anterior tibial translation (ATT) of about 86%. The anteromedial bundle, with its short fibers, seems to have a low effect on ATT stabilization. The posterior cruciate ligament (PCL) is the strongest ligament with a tensile strength of more than 1500 N. The medial capsule and ligaments symbolize the complex function in stabilization to different forces on variable positions of the knee joint. The lateral knee is a multilayer complex of capsular, ligamentous, and musculoskeletal structures with importance for stability in knee rotation and translation.
Introduction
Pigs are widely used for clinical research on the anterior cruciate ligament (ACL) because of the similarity of the knee structure to the human knee. But evidence to support the suitability of using porcine samples to guide clinical practices is limited. This study aims to explore the qualitative and quantitative morphological features of the porcine knee and ACL, and to compare these with data on humans reported in literature.
Methods
Nineteen porcine knees were used for this study. The bone structures were measured on coronal X-ray images. The length of the ACL was measured using a caliper. The ACL bone insertion sites were marked and measured on a digital photograph. The lengths of the long and short axis of the ACL isthmus were measured on the X-ray microscopy reconstructed images. The outcomes were compared with previously reported data on humans using an abstract independent-samples T test.
Results
Qualitative observation indicated a similar location, orientation and general morphology of the porcine ACL to human ACLs. The major difference was the location of the ACL tibial insertion with respect to the anterior horn of the lateral meniscus (AHLM). The porcine ACL was split into AM and PL bundles by the AHLM, while the AHLM was adjacent to the anterolateral border of the ACL tibial insertion in human knees. The quantitative comparison showed no significant difference between the human and porcine ACL in terms of the length of the ACL, the width of the femoral condyle and tibial plateau, and the tibial interspinal width. However, the CSA, the lengths of the long and short axis of the ACL isthmus, and the femoral and tibial insertion areas of the porcine ACL were all significantly larger than the reported features in human knees.
Conclusion
The location, orientation and basic morphology of the porcine ACL and knee are similar to humans. However, the two-bundle structure is more distinct in a porcine ACL, and the dimensions of the porcine ACL are generally larger. This study may provide useful information to researchers when assessing the feasibility and limitations of using porcine samples for research on the human ACL and knee.
Background
To treat anterior cruciate ligament (ACL) injuries, double-bundle ACL reconstruction has been proposed as a more anatomical approach relative to single-bundle reconstruction. However, controversy remains over which technique is superior in addressing knee instability, particularly rotational laxity. We hypothesize that double-bundle reconstruction better restores rotational knee laxity, while both methods are similar in restoring anterior knee laxity, to intact knee levels.
Methods
A controlled laboratory study. Eight cadaveric knees were tested accordingly: (1) static anterior laxity testing under 150 N-anterior tibial loading at 20°, 60° and 90° knee flexion using a material testing machine, followed by (2) dynamic simulated pivot-shift with knee-specific loading involving iliotibial band forces, valgus and internal rotation torques, while the knee was brought from extension to 90° flexion on a 6°-of-freedom custom-designed rig. Tibiofemoral kinematics were recorded using an electromagnetic tracking system for the ACL-intact, ACL-deficient, single-bundle and double-bundle ACL-reconstructed knee conditions.
Findings
Double-bundle reconstruction reduced internal rotation under pivot-shift to levels not significantly different from ACL-intact conditions (P > .173), unlike single-bundle that remained significantly higher at 10–40° flexion (P < .05). For anterior laxity, there was no significant difference between double-bundle, single-bundle, and ACL-intact conditions under static testing (P > .175) or pivot-shift (P = .219). The maximum extent of knee envelope laxity was significantly reduced for double-bundle relative to single-bundle, particularly for the rotatory component (P = .012).
Interpretation
Double-bundle was biomechanically superior to single-bundle in addressing envelope of rotation, while both techniques restored anterior knee laxity to ACL-intact levels.
The knee is a common site of musculoskeletal injury. This chapter reviews basic anatomy and biomechanics as well as some common physical exam maneuvers.
Mucoid degeneration of the anterior cruciate ligament: a little-known cause of deep knee pain Mucoid degeneration of the anterior cruciate ligament (ACL) is a little-known cause of deep atraumatic knee pain that is relatively frequent. Recent studies have reported a prevalence of 1,8-9,2% on MRI of the knee. Mucoid lesions consist of interstitial deposits of glycosaminoglycan between the collagen bundles. This causes hypertrophy of the ACL, which leads to mechanical impingement at the femoral notch, typically resulting in deep or posterior knee pain in terminal flexion and/or extension. Unlike the often-occurring traumatic ACL ruptures, there are no instability complaints. The gold standard for diagnosing mucoid degeneration of the ACL is MRI. This shows an abnormally thickened and ill-defined ACL with an increased intraligamentary signal on all sequences, but the orientation and continuity are usually maintained. Arthroscopically, the mucoid degeneration can be recognized by a hypertrophic ACL with yellowish to brown substances between the fibers. In addition, an absence of the synovial outline of the ACL is seen regularly. An arthroscopic partial or total ACL resection is the treatment of choice for symptomatic mucoid degeneration of the ACL and results in good post-operative outcomes without development of instability.
Recently robotic assistive leg exoskeletons have gained popularity because an increased number of people crave for powered devices to run faster and longer or carry heavier loads. However, these powered devices have the potential to impair knee ligaments. This work was aimed to develop an instrumented knee joint via rapid prototyping that measures the displacements of the four major knee ligaments\textemdash the anterior cruciate ligament (ACL), posterior crucial ligament (PCL), medial collateral ligament (MCL), and lateral collateral ligament (LCL)\textemdash to quantify the strain experienced by these ligaments. The knee model consists of a femur, lateral and medial menisci, and a tibia-fibula, which were printed from 3D imaging scans. Non-stretchable cords served as main fiber bundles of the ligaments with their desired stiffnesses provided by springs. The displacement of each cord was obtained via a rotary encoder mechanism, and the leg flexion angle was acquired via a closed-loop four-bar linkage of a diamond shape. The displacements were corroborated by published data, demonstrating the profiles of the displacement curves agreed with known results. The paper shows the feasibility of developing a subject-specific knee joint via rapid prototyping that is capable of quantifying the ligament strain via rapid prototyping.
Normal arthroscopic anatomy should be well known for an adequate and effective surgical intervention for successful results in surgery. Successful differentiation of normal tissue and pathological tissue is the first step of arthroscopic surgery. In this context, the arthroscopic anatomy of the knee joint is essential for knee arthroscopy which is the most commonly performed orthopaedic procedure [1, 2].
The posterior cruciate ligament (PCL) is the primary posterior stabilizer in the knee. Recent anatomical and biomechanical studies have provided a better understanding of PCL function. PCL injuries are typically associated with other ligament, meniscus, and chondral injuries. Stress radiography is very important in surgical decision making and postoperative evaluation. While isolated grade I or II PCL injuries can usually be treated without surgery, surgical treatment is indicated when acute grade III PCL ruptures occur in conjunction with other ligament injuries and/or repairable meniscus tears. Surgical options for PCL reconstruction are transtibial and tibial inlay reconstruction techniques with single- or double-bundle reconstruction. These techniques can be performed both arthroscopically and open. However, it is not clear which is the best method for PCL reconstruction.
This review identifies the three-dimensional knee loads that have the highest risk of injuring the anterior cruciate ligament (ACL) in the athlete. It is the combination of the muscular resistance to a large knee flexion moment, an external reaction force generating knee compression, an internal tibial torque, and a knee abduction moment during a single-leg athletic manoeuvre such as landing from a jump, abruptly changing direction, or rapidly decelerating that results in the greatest ACL loads. While there is consensus that an anterior tibial shear force is the primary ACL loading mechanism, controversy exists regarding the secondary order of importance of transverse-plane and frontal-plane loading in ACL injury scenarios. Large knee compression forces combined with a posteriorly and inferiorly sloped tibial plateau, especially the lateral plateau—an important ACL injury risk factor—causes anterior tibial translation and internal tibial rotation, which increases ACL loading. Furthermore, while the ACL can fail under a single supramaximal loading cycle, recent evidence shows that it can also fail following repeated submaximal loading cycles due to microdamage accumulating in the ligament with each cycle. This challenges the existing dogma that non-contact ACL injuries are predominantly due to a single manoeuvre that catastrophically overloads the ACL.
Background
The concept of anterior cruciate ligament (ACL) reconstruction (ACLR) has become widely accepted, gaining increased attention in recent years and resulting in many research achievements in this field.
Purpose
The aim of this study was to determine which original articles on ACLR have been most influential in this field by identifying and analyzing the characteristics of the 100 most cited articles.
Study Design
Cross-sectional study.
Methods
Articles on ACLR were identified via the Thomson ISI Web of Science database on November 30, 2019. The 100 most cited articles were identified based on inclusion and exclusion criteria. The data extracted from each article for the subsequent analysis included title, date of publication, total citations, average citations per year (ACY), journal name, first author, institutions, themes, level of evidence, and keywords.
Results
The total number of citations was 29,629. The date of publication ranged from 1975 to 2015. A majority of the articles originated from the United States (58%) and were published in the 1990s (32%) and 2000s (48%). The mean ACY was 18.43 ± 9.51. Of the selected articles, nearly one-half were published in the American Journal of Sports Medicine (42%). The most prolific co-author and first author were Freddie H. Fu (n = 13) and K. Donald Shelbourne (n = 5), respectively. The most productive institution was the University of Pittsburgh (14%). Material comparison (19%) and technique comparison (16%) were the 2 most popular themes. More than one-quarter of articles were level 4 evidence (37%). Moreover, the keywords ACL, ACL reconstruction, ACL rupture, knee joint, knee injuries, and human showed the highest degree of centrality.
Conclusion
By analyzing the characteristics of articles, this study demonstrated that ACLR is a growing and popular area of research, with the focus of research varying through timeline trends. Studies on anatomic reconstruction and biomechanics might be areas of future trends.
Partial anterior cruciate ligament (ACL) tears comprise an estimated 10% to 27% of isolated ACL injuries. Partial ACL tears may be challenging to clinically diagnose. We reviewed relevant studies focusing on the anatomy, diagnosis, imaging, and treatment of a partial injury with the goal of providing guidance to clinicians. Although a comprehensive patient history, thorough clinical examination, and imaging studies are helpful in arriving at a diagnosis, the benchmark for diagnosis remains visualization and examination of the ACL at the time of knee arthroscopy. Currently, limited data exist about the long-term outcomes of nonsurgical treatment. Some studies demonstrate that younger, active patients have the risk of progressing to a complete ACL rupture with conservative treatment. The decision to proceed with surgery is based on careful history and physical examination findings that suggest either a "functional" or "nonfunctional" ACL. Surgical treatment consists of augmenting the intact bundle with a selective bundle reconstruction versus a traditional ACL reconstruction. Selective bundle reconstruction has limited data available but is an option. The best evidence supports traditional ACL reconstruction for the surgical management of patients with documented nonfunctional partial tears of the ACL.
The ligaments of the knee function as static stabilizers of a dynamic joint. The anterior cruciate ligament (ACL) is commonly injured during sports; subsequently, ACL reconstruction is one of the most prevalent procedures in the field of orthopedic surgery. Therefore, knowing basic knee anatomy, ACL graft options, and the biologic healing process is critical for understanding how to treat this injury. Current research is focused on using biologic agents to enhance orthopedic surgeries. Innovative technology including platelet-rich plasma, stem cells, and biologic scaffolding shows promise for improved outcomes after ACL reconstruction.
Background: Although there is a higher prevalence of noncontact anterior cruciate ligament (ACL) injuries during a direction diversion maneuver (DDM), no previous studies have reported how foot-planting strategies affect ACL loading.
Purpose: To investigate the effect of foot-planting strategies on ACL loading in women during a DDM task using a musculoskeletal modeling approach.
Study Design: Descriptive laboratory study.
Methods: A total of 13 female participants performed a DDM task, which involved running at 4.5 ± 0.2 m/s and turning left at 35� to 55� under a foot-planting strategy in 3 directions: neutral, toe-in, and toe-out. Kinematic and kinetic data were measured with the
use of a 3-dimensional motion capture system and force platform to calculate variables such as joint angle, shear force, and
moment. Anterior ACL and posterior ACL forces were extracted using musculoskeletal modeling.
Results: The peak anterior ACL force was significantly larger for the toe-out condition (31.29 ± 4.02 N/body weight [BW]) compared with the toe-in condition (25.43 ± 5.68 N/BW) (P ¼ .047), with no significant difference in the neutral condition. The toe-out condition had a higher knee valgus angle (2.98� ± 4.20�; P ¼ .041), knee shear force (10.20 ± 1.69 N/BW; P ¼ .009), and knee internal rotation moment (–0.18 ± 0.16 N�m/BW�height; P ¼ .012) than the toe-in and neutral conditions.
Conclusion: Through musculoskeletal modeling, we were able to conclude that the toe-out condition during the DDM might result in a higher risk of ACL injuries. Athletes and sports practitioners should avoid the toe-out foot-planting strategy when participating in a sporting activity.
Clinical Relevance: Based on these findings, medical professionals and athletic coaches can gain knowledge on how footplanting strategy affects ACL loading. Understanding the actual cause of an ACL injury can be useful for designing preventive training programs or strategies to decrease the risk of such injuries.
A six-degrees-of-freedom mechanical linkage device was designed and used to study the unconstrained motion of ten intact human cadaver knees. The knees were subjected to externally applied varus and valgus (V-V) moments up to 14 N-m as well as anterior and posterior (A-P) loads up to 100 N. Tests were done at four knee flexion angles; 0, 30, 45, and 90 deg. Significant coupled axial tibial rotation was found, up to 21.0 deg for V-V loading (at 90 deg of flexion) and 14.2 deg for A-P loading (at 45 deg of flexion). Subsequently, the knees were dissected and the locations of the insertion sites to the femur and tibia for the anteromedial (AM), posterolateral (PL), and intermediate (IM) portions of the ACL were identified. The distances between the insertion sites for all external loading conditions were calculated. In the case when the external load was zero, the AM portion of the ACL lengthened with knee flexion, while the PL portion shortened and the intermediate (IM) portion did not change in length. With the application of 14 N-m valgus moment, the PL and IM portions of the ACL lengthened significantly more than the AM portion (p less than 0.001). With the application of 100 N anterior load, the AM portion lengthened slightly less than the PL portion, which lengthened slightly less than the IM portion (p less than 0.005). In general, the amount of lengthening of the three portions of the ACL during valgus and anterior loading was observed to increase with knee flexion angle (p less than 0.001).
To evaluate the possible relationship between femoral intercondylar notch stenosis and anterior cruciate ligament injuries in pivoting and cutting sports, a 2-year prospective study was performed on intercollegiate athletes at a Division I university. Daily practice times and athlete participation in practices and games were recorded for each sport during the 2-year period. Bilateral intercondylar notch view radiographs were taken of all athletes enrolled in the study. The notch width index, a ratio that measures the width of the anterior outlet of the intercondylar notch divided by the total condylar width at the level of the popliteal groove, was measured for each knee. A total of 213 athletes, representing 415 anterior cruciate ligament-intact knees, were enrolled in the study. There were 7 anterior cruciate ligament tears. Statistical analysis demonstrated a correlation between femoral intercondylar notch stenosis and anterior cruciate ligament injuries. No statistical difference was found between the sex of the athlete and notch width indices or rate of anterior cruciate ligament tears. Athletes with intercondylar notch stenosis appear to be at increased risk for noncontact anterior cruciate ligament injuries.
With today's increasing emphasis on sporting activities, the incidence of anterior cruciate ligament injuries has also increased. Epidemiologic studies estimate that the prevalence of anterior cruciate ligament injuries is about 1 per 3000 Americans. Management of these injuries has evolved from nonoperative treatment to extracapsular augmentation and primary ligament repair to anterior cruciate ligament reconstruction. Treatment of these injuries has significantly improved over the last few decades with the application of knowledge gained from both basic science and clinical research. This article is composed of two parts. The first part reviews the biology and biomechanics of the injured anterior cruciate ligament and the basic science of reconstruction. In the second part, to be published later, current operative concepts of reconstruction, as well as clinical correlations, are reviewed. Summarizing the latest information on basic scientific as well as clinical studies regarding the anterior cruciate ligament, this article intends to demonstrate the correlation between the application of basic science knowledge and improvement of clinical outcomes.
PURPOSE: To compare the outcome of ACL reconstuction using patellar tendon (PAT) to that when using hamstring tendons. Type of Study: Meta-analysis of controlled trials of patellar tendon versus hamstring tendons for ACL reconstruction. METHODS: Meta-analysis is a systematic method for statistical analyses that allows compilation of combined data from various independent studies. This allows one to assess the potential benefits of various treatments when conclusions based on individual studies are difficult to assess. We conducted a meta-analyses (M-A) using controlled trials (CTs) to determine if there are differences between the 2 methods. Although both surgical techniques have potential for good results, we hypothesized that there are differences in outcomes between these techniques. We included CTs that used standard evaluation techniques with a minimum 2-year follow-up. Outcomes evaluated included: return to preinjury level of activity, KT testing, Lachman scores, pivot shift scores, range of motion (ROM) loss in flexion and extension, complications, and failures. Relative risks for each outcome were calculated for each study and pooled across studies using a fixed effects method. RESULTS: Four studies fulfilled our inclusion criteria. Relative risks with 95% confidence intervals and P values were obtained for each of the outcomes listed above. The results show significant differences between PAT and semitendinosus and gracilis tendon (ST&G) reconstructions. PAT patients have a greater chance of attaining a statically stable knee (as measured by KT) and nearly a 20% greater chance of returning to preinjury activity levels. CONCLUSIONS: Although both techniques, as performed in the late 1980s and early 1990s, yielded good results, PAT reconstuction led to higher postoperative activity levels and greater static stability than hamstring reconstruction. This is statistically significant based on this meta-analysis.
The focus of most anterior cruciate ligament reconstructions has been on replacing the anteromedial bundle and not the posterolateral bundle.
Anatomic two-bundle reconstruction restores knee kinematics more closely to normal than does single-bundle reconstruction.
Controlled laboratory study.
Ten cadaveric knees were subjected to external loading conditions: 1) a 134-N anterior tibial load and 2) a combined rotatory load of 5-N x m internal tibial torque and 10-N x m valgus torque. Resulting knee kinematics and in situ force in the anterior cruciate ligament or replacement graft were determined by using a robotic/universal force-moment sensor testing system for 1) intact, 2) anterior cruciate ligament deficient, 3) single-bundle reconstructed, and 4) anatomically reconstructed knees.
Anterior tibial translation for the anatomic reconstruction was significantly closer to that of the intact knee than was the single-bundle reconstruction. The in situ force normalized to the intact anterior cruciate ligament for the anatomic reconstruction was 97% +/- 9%, whereas the single-bundle reconstruction was only 89% +/- 13%. With a combined rotatory load, the normalized in situ force for the single-bundle and anatomic reconstructions at 30 degrees of flexion was 66% +/- 40%and 91% +/- 35%, respectively.
Anatomic reconstruction may produce a better biomechanical outcome, especially during rotatory loads.
Results may lead to the use of a two-bundle technique.
Knee Joint.- Ankle Joint.- Wrist.- Elbow Joint.- Shoulder.- Subtalar Joint.- Joints of the Toes.- Joints of the Fingers.- Hip Joint.- Carpal Tunnel Syndrome.- Bursal Endoscopy.- Minimally Invasive Endoscopically Assisted Techniques.
Purpose: The purpose of this study was to better delineate the anatomy of "resident's ridge," a term coined by William Clancy Jr., M.D., to describe the raised bony landmark commonly visualized just anterior to the femoral attachment of the anterior cruciate ligament (ACL). This landmark can mislead the novice surgeon into misplacing the femoral tunnel of ACL reconstructions. Type of Study: Cadaveric anatomic study. Methods: Ten human distal femurs harvested from embalmed specimens were fixed, sectioned, and analyzed for the presence and descriptive characteristics of resident's ridge. A single, blinded examiner evaluated slope, cortical thickness at 4 sites, and the presence or absence of a distinct ridge relative to the attachment of the ACL. Results: A defined resident's ridge was present in 9 of 10 specimens. This was directly associated with a change in slope of the intracondylar roof in the same 9 of 10 patients. The mean cortical thickness at the ACL attachment site was 1.6 mm. This was thicker than at resident's ridge.(mean, 0.90 mm), the cartilage-intercondylar notch junction (mean, 0.96 mm), and a point midway between the ACL attachment and the cartilage-intercondylar notch junction (mean, 0.90 mm). Conclusions: The phenomenon of "resident's ridge" is accounted for by a distinctive change in slope of the femoral notch roof that occurs just anterior to the femoral attachment of the ACL. The density change apparent at the time, of notchplasty is probably caused by the transition between normal cortical thickness just anterior to the ACL and the cortical thickness of the ACL attachment. No distinctive increased cortical thickness can be identified as "resident's ridge."
An internet-based literature review using the catalog of the National Library of Medicine for the keyword “anterior cruciate ligament” results in 5884 hits, thus reflecting the high importance of basic and clinical research. To achieve a satisfying surgical outcome after anterior cruciate ligament (ACL) reconstruction, a basic knowledge of the anatomy of the ACL is essential. The early manifestation of the ACL in the fetal knee joint suggests that the knee joint is early under the stabilization of the ACL. The origin of the ACL is at the medial surface of the lateral femoral condyle and runs distal-anterior-medial to the insertion at the medial tibial eminence. In the literature, a 2-bundle description of the ACL into anteromedial and posterolateral bundle has been accepted as a basis for the understanding the function of the ACL. Length and diameter of the native ACL may play an important role for choosing the type of graft and for the preparation of the graft. Microscopically, femoral origin and tibial insertion have the structure of a chondral apophyseal enthesis and can be separated into 4 layers. The collagen fibrils of the ACL are surrounded by connective tissue forming multiple fascicles. Proximal and distal vessels support a synovial plexus from which small vessels run into the ligament and align longitudinally parallel to the collagen bundles.
Nonsimultaneous, bilateral ACL injuries are not uncommon. We studied a group of patients with these injuries to determine possible predisposing factors that could aid in early detection and prevention of contralateral ACL injury. Retrospective analysis of 1,120 patients with ACL ruptures who were treated between 1983 and 1987 revealed 45 patients with bilateral ruptures. Complete follow-up data were available for 41 of these patients. We examined age at initial injury, sex, interval between initial and contralateral ACL injury, mechanism of injury, activity at injury, medical and family histories, treatment of initial injury, and radiographic measurement of intercondylar notch width. The overall incidence of bilaterality was 4.01% in the 28 male and 13 female patients. Their average age was 19 years and 10 months. The average interval between initial and contralateral injury was 47 months. A noncontact cutting maneuver was the most common mechanism of injury. We devised a method to measure and compare intercondylar notch widths on plain radiographs. We compared the mean notch width index (NWI) of the bilateral group to the mean NWI of a group of 50 consecutive patients with "normal" knees and to the mean NWI of 50 consecutive patients with acute ACL ruptures. The mean NWI for the normal group was .2338, for the acute ACL group, .2248, and for the bilateral group, .1961. We noted a statistically significant difference when we compared the bilateral group to the normal and acute groups (P less than 0.0001, respectively). There was no statistically significant difference between the NWI of the normal and acute ACL groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Supported by the Arthritis Research Campaign, a charity based in Chesterfield, UK. Dr. Lie was supported by the Singapore Government.
The study of the altered knee joint movement patterns that follow anterior cruciate ligament (ACL) rupture can be very insightful in the development of prevention and therapeutic strategies concerning this injury. This can be achieved through three-dimensional kinematic analysis, because it provides an objective evaluation in vivo of the knee joint function. It has been demonstrated that ACL-deficient patients develop functional adaptations (ie, quadriceps avoidance gait) and walk with the knee in a more extended position to compensate for the ACL loss. Furthermore, it has been shown that ACL rupture results in anterior tibial translation and excessive tibial rotation while performing everyday activities. Although anterior tibial translation is restored with ACL reconstruction, tibial rotation seems to be restored only during low-demanding activities, whereas it remains increased during high-demanding activities. A possible explanation for the lack of restoration of tibial rotation to normal levels is the absence of complete reinstatement of the actual anatomy of the ACL. Reconstruction techniques should become more anatomic and try to approximate both ACL bundles. Two-bundle reconstruction may have advantages over single-bundle reconstruction, with respect to regaining a structure that morphologically and functionally better resembles a normal ACL. This technique however, has not been investigated dynamically, and future research should be performed. Therefore, long-term follow-up studies should focus on the advantages and disadvantages of different surgical procedures, whether it is the graft material or the tunnel positioning, so that dynamic knee function is restored and future pathology of the knee joint is prevented.
The purposes of this review are to explain surgical and biomechanical concepts of anatomic anatomic anterior cruciate ligament (ACL) reconstruction and to introduce our anatomic reconstruction procedure of the anteromedial (AM) and posterolateral (PL) bundles of the ACL using hamstring tendon autografts. According to common medical concept, anatomical ACL reconstruction is defined as the reconstruction in which all 4 ends of 2 tendon grafts are grafted at the center of the anatomical attachment of the AM bundles or the PL bundles, not only on the femur but also on the tibia, because only such a procedure allows for the reconstruction of 2 bundles having an anatomical orientation. On the basis of our anatomic studies on the normal attachments of the ACL, we developed an arthroscopy-assisted anatomic reconstruction procedure of the AM and PL bundles that involves a new method of creating the tibial and femoral tunnels for the posterolateral bundle. To insert a Kirschner wire as a guide into the tibia, we use an originally developed a Wire-navigator, which is a key device for the trans-tibial tunnel technique. To visualize the femoral attachment of the posterolateral bundle, the medial infra-patellar portal is more useful than the lateral one. Biomechanical studies have shown that anatomic double-bundle ACL reconstruction has some biomechanical advantages over a single-bundle reconstruction. In our clinical experience, results of the anatomic reconstruction were superior to those of the one-bundle reconstruction. We believe that the anatomic reconstruction of the AM and PL bundles using hamstring tendon autografts is clinically practical in the treatment for the ACL-deficient knee.
Anatomical observation and biomechanical studies have shown that the anterior cruciate ligament (ACL) mainly consists of 2 distinct bundles, the anteromedial bundle (AMB) and posterolateral bundle (PLB). These 2 bundles have different roles in the control of knee stability. The AMB essentially controls the anterior tibial translation, whereas the PLB mainly controls the rotatory stability of the knee by limiting the internal rotation of the lateral tibial plateau. Current techniques for reconstruction do not completely reproduce the anatomy and function of the ACL. They address only the anteromedial bundle, which does not fully restore ACL function throughout the arc of motion. Current grafts control the anterior tibial subluxation near extension but are less efficacious in providing rotatory stability. Recently several authors have suggested reconstructing not only the anteromedial bundle, but also the posterolateral bundle. After discussing the relevant anatomical and biomechanical data, this article describes a double-bundle ACL reconstruction technique using hamstring tendons routed through 2 tibial and 2 femoral independent tunnels. Short-term results of this technique are encouraging; however, long-term follow-up studies are needed to compare the outcome of a more physiologic double-bundle ACL reconstruction with single-bundle techniques.
The anterior cruciate ligament (ACL) is a complex structure consisting of 2 functionally independent anatomic bundles, the anteromedial and posterolateral bundles. Anatomic and biomechanical studies have demonstrated distinctive functions for each of these bundles at various degrees of flexion. ACL reconstructions have traditionally focused solely on the reconstruction of the anteromedial bundle, with little consideration for the posterolateral bundle. Recent reports have appeared describing various techniques for anatomic ACL reconstruction in an attempt to recreate the native anatomy. We present an arthroscopic technique of anatomic, double-bundle ACL reconstruction using tibialis anterior tendon allografts. This technique restores the anatomic footprint of the native ACL on both the tibia and the femur. We believe that focusing reconstructive techniques on recreating both bundles of the ACL more closely recreates the biomechanical function of the native ligament. Oper Tech Orthop 15:140-145 © 2005 Elsevier Inc. All rights reserved. KEYWORDS anterior cruciate ligament, anatomic reconstruction, double bundle, allograft, arthroscopy R econstruction of the injured anterior cruciate ligament (ACL) has been the subject of considerable scrutiny for the past 3 decades. Modern ACL reconstructive procedures have focused on endoscopic reconstruction of the anterome-dial (AM) bundle of the ACL using a variety of graft choices and fixation options. Clinical success rates of modern tech-niques have varied between 69% and 95% in various se-ries. 1-3 The explanation for these less than satisfactory results remains elusive but may be the consequence of a failure of modern techniques to fully restore normal kinematics to the knee. Recent biomechanical studies have revealed some interest-ing insight regarding the role that the posterolateral (PL) bundle may have in restoring knee stability. Biomechanical studies in our research center have shown that standard ACL reconstructions using either quadruple-loop hamstring or bone-patellar tendon-bone grafts are successful at restoring anterior stability to the knee. However, these standard tech-niques are deficient at restoring stability in response to a combined rotatory and internal rotation force with valgus torque, as one would see with a pivot shift. 4 Current recon-structive procedures place the graft to close to the central axis of the tibia and femur, making them inadequate to resist these rotational moments. This concept was further illus-trated recently when Loh and coworkers 5 examined the bio-mechanical implications of femoral tunnel placement at ei-ther a 10 o'clock or 11 o'clock position. They discovered that both positions were able to effectively resist anterior tibial translation; however, the 10 o'clock position, which is closer to the footprint of the PL bundle, was far superior at resisting rotatory loads. As one would expect, neither single bundle reconstruction was successful at fully restoring knee stability back to the level of the intact knee. Further investigations in our laboratory examined the bio-mechanical differences between standard single-bundle and anatomic double-bundle ACL constructs in a cadaveric model. 6 Anatomic double-bundle reconstructions were able to more closely restore normal kinematics to the knee when compared with a single-bundle technique. Both anterior
The anterior cruciate ligament has a complex fiber anatomy and is not considered to be a uniform structure. Current anterior cruciate ligament reconstructions succeed in stabilizing the knee, but they neither fully restore normal knee kinematics nor reproduce normal ligament, function. To improve the outcome of the reconstruction, it may be necessary to reproduce the complex function of the intact anterior cruciate ligament in the replacement graft. We examined the in situ forces in nine human anterior cruciate ligaments as well as the force distribution between the anteromedial and posterolateral bundles of the ligament in response to applied anterioi tibial loads ranging from 22 to 110 N at knee flexion angles of 0–90°. The analysis was performed using a robotic manipulator in conjunction with a universal force-moment sensor. The in situ forces were determined with no device attached to the ligament, while the knee was permitted to move freely in response to the applied loads. We found that the in situ forces in the anterior cruciate ligament ranged from 12.8 ± 7.3 N under 22 N of anterior tibial load applied at 90° of knee flexion to 110.6 ± 14.8 N under 110 N of applied load at 15° of flexion. The magnitude of the in situ force in the posterolateral bundle was larger than that in the anteromedial bundle at knee flexion angles between 0 and 45°, reaching a maximum of 75.2 ± 18.3 N at 15° of knee flexion under an anterior tibial load of 110 N. The magnitude of the in situ force in the posterolateral bundle was significantly affected by knee flexion angle and anterior tibial load in a fashion remarkably similar to that seen in the anterior cruciate ligament. The magnitude of the in situ force in the anteromedial bundle, in contrast, remained relatively constant, not changing with flexion angle. Significant differences in the direction of the in situ force between the anteromedial bundle and the posterolateral bundle were found only at flexion angles of 0 and 60° and only under applied anterior tibial loads greater than 66 N. We have demonstrated the nonuniformity of the anterior cruciate ligament under unconstrained anterior tibial loads. Our data further suggest that in order for the anterior cruciate ligament replacement graft to reproduce the in situ forces of the normal anterior cruciate ligament, reconstruction techniques should take into account the role of the posterolateral bundle in addition to that of the anteromedial bundle.
The anterior cruciate ligament originates at the medial wall of the lateral femoral condyle and inserts into the middle of the intercondylar area. It contributes significantly to the stabilization and kinematics of the knee joint.
The femoral origin is oval and is located in the posterior aspect of the lateral femoral condyle. Therefore, it is difficult to visualize the femoral origin arthroscopically. This might be one reason for anterior malpositioning of the femoral bone tunnel during anterior cruciate ligament reconstruction. The position of the femoral origin is behind the center of rotation of the knee joint; therefore, it becomes tense when the knee is extended. The tibial insertion is oval and its center is nearly in the middle of the tibial plateau. Definite landmarks for tibial tunnel placement in anterior cruciate ligament reconstruction are the distance between the central insertion point at the intercondylar floor and the posterior cruciate ligament (7-8 mm) and the anterior horn of the lateral meniscus.
The anterior cruciate ligament consists of multiple small fiber bundles. From a functional point of view, one can differentiate the anteromedial and posterolateral fiber bundles. The anteromedial fibers are tense during a greater range of motion than the posterolateral fibers.
The main part of the anterior cruciate ligament consists of type I collagen-positive dense connective tissue. The longitudinal fibrils of type I collagen are divided into small bundles by thin type III collagen-positive fibrils. In the distal third, the structure of the tissue varies from the typical structure of a ligament. In this region, the structure of the tissue resembles fibrocartilage. Oval-shaped cells surrounded by a metachromatic extracellular matrix lie between the longitudinal collagen fibrils. The femoral origin and the tibial insertion have the structure of a chondral apophyseal enthesis. Near the anchoring region at the femur and tibia, there should be various mechanoreceptors, which might have an important function for the kinematics of the knee joint.
The blood supply of the anterior cruciate ligament arises from the middle geniculate artery. The ligament is covered by a synovial fold where the terminal branches of the middle and the inferior geniculate artery form a periligamentous network. From the synovial sheath, the blood vessels penetrate the ligament in a horizontal direction and anastomose with a longitudinally orientated intraligamentous network. The distribution of blood vessels within the anterior cruciate ligament is not homogeneous. We detected three avascular areas within the ligament: Both fibrocartilaginous entheses of the anterior cruciate ligament are devoid of blood vessels. A third avascular zone is located in the distal zone of fibrocartilage adjacent to the roof of the intercondylar fossa.
The anatomical and functional details of the cruciate ligamants of the knee were studied on 20 cadaver knees and 24 fresh knees. Each anterior cruciate ligament was found to consist of 2 parts: a distinct anteromedial band (AMB) and a main posterolateral part. The exact geometry of the ligaments and their relationship to bony landmarks were recorded in detail. The state of the cruciate ligaments, i.e. tightness or looseness was recorded in the various positions of the knee as the basis for classification of the function of the various anatomical components. Selective cutting of the anterior cruciate ligament resulted in an increase of anterior drawer flexion and extension. External and internal rotation were increased in both flexion and extionsion. Hyperextension also was increased. It is suggested that the AMB of the anterior cruciate is responsible for the in anteroposterior drawer with flexion. The selective cutting of the posterior cruciate ligament demonstrated that it is important in the flexed knee and produces an.increased posterior drawer sign. Rotational stability was unchanged in extension, but altered in flexion after cutting the posterior cruciate.
In transverse and longitudinal paraffin-embedded sections, the human anterior cruciate ligament (ACL) is made up of wavy bundles of collagen fibres arrayed in various directions, the majority around the axis of the ligament with a few running parallel to it. The fascicles making up the larger bundles are also characterised by this undulating appearance. In thin sections 2 types of collagen fibrils are observed: small (with a single diameter peak at 45 nm) and large (3 peaks at 35, 50 and 75 nm respectively), organised into distinct areas made up of either large or small bundles of fibrils. The numerous fibroblasts that are present appear elongated in the direction of the bundles with branches and short cytoplasmic processes. The elastic system is made up of both elastic and oxytalan fibres. The varied orientation of the bundles in the ACL, the complex ultrastructural organisation and the abundant elastic system make it very different from other ligaments and tendons, providing a structure able to withstand the multiaxial stresses and varying tensile strains imposed upon it.
This work studied the fibre bundle anatomy of the anterior cruciate ligament. Three functional bundles--anteromedial, intermediate, and posterolateral--were identified in cadaver knees. Their contributions to resisting anterior subluxation in flexion and extension were found by repeated tests after sequential bundle transection. Changes of length in flexion and extension and in tibial rotation were measured. None of the fibres were isometric. The posterolateral bundle was stretched in extension and the anteromedial in flexion, which correlated with increased contributions to knee stability and the likelihood of partial ruptures in these positions. Tibial rotation had no significant effect. The fibre length changes suggested that the 'isometric point' aimed at by some ligament replacements lay anterior and superior to the femoral origin of the intermediate fibre bundle and towards the roof of the intercondylar notch.
A technique is demonstrated, employing an instrumented spatial linkage, for the determination of the length patterns of discrete fiber bundles within a ligament under controlled loading conditions. The instrumented spatial linkage was used to measure the three-dimensional joint motion. The linkage was also used as a three-dimensional coordinate digitizer to determine the spatial location of bony landmarks and the ligament's insertion areas. The length of pseudo fiber bundles was determined as the straight line distance between bone attachments. A comparison is presented, showing good agreement, between elongation patterns obtained from this method and those measured using an instrumented fine wire cable fiber. A sensitivity analysis was performed to evaluate the influence of tibial and femoral attachment location on the length pattern of fiber bundles of the anterior cruciate ligament. It was found that the relationship between fiber elongation and knee flexion depended strongly on the fibers femoral attachment location but not on its tibial attachment location.
In thirty-three normal cadaver knees from adults (mean age, twenty-nine years), the average length of the anterior cruciate ligament was 31 +/- 3 millimeters and the angle between the ligament and the long axis of the femur was 28 +/- 4 degrees with the knee at 90 degrees of flexion. We could find no macroscopic or microscopic evidence of discrete subdivisions of the anterior cruciate ligament. We studied the functional importance of the positions of the attachments of the anterior cruciate ligament. The distance between the central points of the normal attachment areas on the tibia and on the femur was found to be isometric during flexion and extension. The so-called over-the-top position on the femur was the least favorable of the positions that we tested, since it resulted in an average elongation of the ligament of ten millimeters with the knee in full extension as compared with full flexion. On the basis of the results in the present study, we suggest some basic principles for a standardized replacement operation for a deficient anterior cruciate ligament.
In a biomechanical and morphological study of cadaver knees and a clinical end result study of fifty patients with tears of the anterior cruciate ligament, the structure and function of the ligament, the mechanism of injury, and the results of various forms of therapy were analyzed. It was concluded that tension of the anterior cruciate ligament varies during knee motion, being least at from 40 to 50 degrees of flexion; that there are adequate intraligamentous blood vessels and nerves for healing to occur; that isolated tears of the anterior cruciate ligament do occur (probably as the result of internal rotation displacement of the tibia with respect to the femur); that such tears are frequently associated with meniscal tears; and that early results of operative or nonoperative treatment of the anterior cruciate ligament are acceptable although late instability may occur.
Semitendinosus anatomic reconstruction (STAR) rebuilds the major anatomic bands of the anterior cruciate ligament (ACL) and provides isometric ligamentous relationships. STAR secures a graft firmly enough to allow intraoperative testing and early motion. It provides a graft comparable in strength with a normal ACL and salvages the insufficient cruciate ligament even after other procedures have failed. Although technically difficult, this procedure can be accomplished in approximately one hour after it has been mastered. During more than four years of experience, STAR has been a predictable and reliable method for anterior cruciate acute augmentation, as well as reconstruction for chronic cruciate ligament insufficiency.
The anterior cruciate ligament (ACL) is a multifascicular structure whose femoral and tibial attachments, as well as spatial orientation within the knee, are directly related to its function as a constraint of joint motion. The ACL is made up of multiple collagen bundles that give rise to the multifascicular nature of the ligament. This arrangement results in a different portion of the ligament being taut and therefore functional, throughout the range of motion. The ACL receives its blood supply from branches of the middle genicular artery, which from a vascular synovial envelope around the ligament. These periligamentous vessels penetrate the ligament transversely and anastomose with a longitudinal network of endoligamentous vessels. The body attachments do not contribute significantly to the vascularity of the ligament. The nerve supply to the ACL originates from the tibial nerve. Although the majority of fibers appear to have a vasomotor function, some fibers may serve a proprioceptive or sensory function.
Knowledge of the anatomy of the anterior cruciate ligament (ACL), including its course and orientation in relation to the roof of the intercondylar fossa, is a prerequisite for successful intra-articular ACL reconstruction. To attain precision placement of the tibial attachment site and to avoid graft/roof conflict in the extended knee position, we assessed the anteroposterior tibial insertion of the ACL in the midsagittal plane of the extended knee. We measured the anterior-posterior (AP) limits and the center of the tibial attachment area of the ACL from the anterior tibial margin. The inclination angle of the intercondylar fossa roof was measured with respect to the shaft axis of the femur. The tibial attachment area of the ACL was determined in ten cadaveric knees. Using the cryoplaning technique, we determined the tibial attachment of the ACL in five knees. Using contrast magnetic resonance arthrography (MRA), we measured the tibial insertion of the ACL in 35 patients (23 male and 12 female) with intact ACLs. The total AP midsagittal diameter of the tibia averaged 51.0 +/- 5.8 mm in the cadaveric knees, 49 mm on cryosections, and 53.7 mm in men and 49.0 mm in women with MRA. The average anterior limit of the ACL, measured from the anterior tibial margin, was 14 +/- 4.2 mm in the cadaveric knees, 12.1 mm at cryosectional anatomy, and 15.2 mm in men and 13.4 mm in women with MRA.(ABSTRACT TRUNCATED AT 250 WORDS)
The purpose of this prospective study was to define constant anatomic intraarticular and extraarticular landmarks that can be used as definitive reference points to reproducibly create a tibial tunnel for anterior cruciate ligament (ACL) reconstruction that (1) results in an impingement-free graft in full extension without an intercondylar roofplasty; (2) positions the tibial tunnel's intraarticular orafice sagittally central in the original ACL insertion without visually guessing; (3) positions the tibial tunnel such that the sagittal tunnel-plateau angle is parallel with the sagittal intercondylar roof-plateau angle in full extension to minimize shear seen by the graft at the tibial tunnel inlet, and by doing so; (4) maximizes tunnel length to avoid patellar tendon graft-tunnel length mismatch allowing for endosteal interference screw fixation on both sides of the joint. Anatomic dissections in 50 knees showed the ACL sagittal central insertion point on the intercondylar floor averages 7 mm (range 7 to 8 mm) sagittally anterior to the anterior margin of the posterior cruciate ligament (PCL) with the knee flexed 90 degrees such that the PCL may be used as a reliable reference landmark for locating the ACL sagittal central insertion. This constant relationship was found to be independent of knee size. Extraarticularly, beginning the tibial tunnel sagittally 1 cm above the superior (sartorial) border of the pes anserinus insertion and coronally 1.5 cm posteromedial from the medial margin of the tibial tubercle along the superior surface of the pes, directed toward the sagittal central ACL insertion, led to a sagittal tunnel-plateau angle that averaged 68 degrees (range 64 degrees to 72 degrees) with a corresponding tunnel length that averaged 58 mm (range 50 to 65 mm) in 23 knees. This data correlated well with data obtained clinically in a series of 50 consecutive ACL reconstructions using intraarticular PCL and extraarticular pes anserine-medial tibial tubercle referenced tibial tunnels in which postoperative full extension lateral radiographs confirmed a sagittal tunnel-plateau angle parallel or near parallel with the intercondylar roof-plateau angle in all cases averaging 68 degrees +/- 3.8 degrees. Tibial tunnel length averaged 60 mm (range 52 to 66 mm) and in no case was there a patellar tendon autograft-tunnel length mismatch.
The best proximal insertion for an ACL graft is an anatomic insertion. The anatomic landmarks of this insertion area are well known, but it is sometimes difficult to find these anatomic landmarks during the operation. Thus, it is desirable to have an objective method to control the insertion. This study was undertaken because no description is available how you can localize the projection of the anatomic ALC insertion exactly in an X-ray picture. We dissected ten human cadaveric knees with intact ACLs. The most ventral, dorsal, distal and proximal borders of the insertion area were marked with 4 K-wires. The K-wires were shortened exactly on the bone border of the intercondylar space. Then the knees were X-rayed in a strictly lateral position. Thus, the shortened ends of the K-wires determined the projection of the ACL insertion in the X-ray picture. The center of this marked area was called point K. Then we determined 4 distances in the X-ray picture: distance t: the sagittal diameter of the lateral condyle, measured along the Blumensaat line distance h: the maximal height of the notch distance a: the distance between K and the dorsal border of the condyle, measured along t distance b: the distance between t and K, measured on a perpendicular line on t Distance a is a partial distance of t and distance b is a partial distance of h. Because of varying projection factors and varying knee sizes, absolute values of these distances are not helpful. This is the reason why we expressed a and b as a proportion of t and h. Distance a was measured 24.8% of distance t. Distance b was measured 28.5% of distance h. The maximal deviation of a and b was 2.2% and 2.5%. Therefore, you can say: In a strictly lateral X-ray picture the distance of K (midpoint of proximal ACL insertion) from the dorsal border of the condyle is 24.8% of the whole diameter of the condyle, and the distance of K from the roof of the notch is 28.5% of the notch-height. This method does not depend on the size of the knee and the distance between the X-ray unit and the knee. The only condition is that the X-ray of the knee must be strictly lateral. This method is easy to handle and is reproducible. It can be used intraoperatively if the surgeon is not sure about the right insertion or if the anatomic landmarks cannot be seen exactly. It can be used postoperatively for documentation of the right position of the substitute. It can be used to find out the possible reason for rupture of a transplant (insertion too ventral) before the revision operation.
The general objectives of the work reported in this article were to describe and validate a method for directly measuring strain in the posterolateral bundle (PLB) of the anterior cruciate ligament (ACL). The method is a procedure for gaining surgical access to the posterior fibers of the PLB through a portal incised in the joint capsule and then suturing a liquid metal strain gage (LMSG) on to these fibres. Because the incision possibly alters the load-displacement mechanics of the joint, validation included performing experiments to test the hypothesis that the incision did not significantly affect load-displacement relations. To illustrate the utility of the method, strains in both the anteromedial bundle (AMB) and PLB were measured and compared over the full range of flexion. Validation experiments revealed that the capsular incision as well as other incisions had no measurable effect on the load-displacement mechanics of the joint. Also, the PLB strain was significantly different from the AMB strain during passive flexion with a reciprocating function in load sharing evident between the two bundles.
The purpose of this study was to compare the measurements of the intercondylar notch width (NW) in men and women radiographically and intraoperatively, and to determine if the radiograph would demonstrate a difference in the patients with unilateral and bilateral anterior cruciate ligament (ACL) tears compared with non-injured patients. The control groups consisted of 100 men and 100 women from our young adult clinic population without a history of knee injury or clinical evidence of ligamentous deficiency. The study group consisted of 90 men with bilateral and 297 with unilateral ACL reconstructions (mean age 25.1 years, range 13-53 years) and 41 women with bilateral and 129 with unilateral ACL reconstructions (mean age 22.3 years, range 13-48 years). On 45 degrees flexion weight-bearing radiographs, we measured the intercondylar NW in controls and patients at one-half notch height from the lateral edge of the articular margin of the medial femoral condyle to the apex of the intercondylar notch. Intraoperatively, the surgeon took a direct measurement at the same site with sterile calipers. The surgeon was unaware of the radiographic measurement. The mean radiographic NW measurements for women were 12.8 mm in the bilateral group, 13.8 mm in the unilateral group, and 14.5 mm in the control group (P < 0.05) and, for men, 15.3 mm in the bilateral group, 15.8 mm in the unilateral group, and 16.9 mm in the control group (P < 0.05). The preoperative radiographic NW measurements correlated with actual intraoperative measurements (r = 0.72, P < 0.01). We conclude that the intercondylar NW of the femur is narrower in women than men, and, in both men and women, the NW is narrower in patients who sustain ACL tears compared with controls.
Stationary bicycling is commonly prescribed after anterior cruciate ligament injury or reconstruction; however, the strains on the ligament or ligament graft during stationary bicycling remain unknown. In this study we measured ligament strain on eight patients who were candidates for arthroscopic meniscectomy under local anesthesia. Six different riding conditions were evaluated: three power levels (75, 125, and 175 W), each of which was performed at two cadences (60 and 90 rpm). The peak ligament strain values ranged from 1.2% for the 175-W, 90-rpm, condition to 2.1% for the 125-W, 60-rpm, condition. No significant differences were found in peak strain values due to changes in power level or cadence. Thus, the strain values were pooled across the six riding conditions tested. The mean peak strain value was 1.7%, a value that is relatively low compared with other rehabilitation activities previously tested. These data suggest that knee rehabilitation programs can be designed to include this selection of power and cadence levels without significantly changing ligament strain values. Thus, stationary bicycling is a rehabilitation exercise that permits the patient to increase muscle activity by increasing the power level or decreasing the cadence without subjecting the ligament or ligament graft to higher strain values.
Reconstruction of a form anterior cruciate ligament (ACL) cannot be successful without a properly placed tibial tunnel. Preventable complications such as anterior knee pain, effusions, extension loss, and recurrent instability can occur when the tibial tunnel is improperly placed and the roof and notchplasty are insufficient. This article reviews the principles for anatomic placement of the tibial tunnel so that complications associated with impingement of the ACL graft on the intercondylar roof can be prevented. Five factors that contribute to roof impingement are discussed, including differences in the size and shape of the ACL and the graft, variability in knee extension and roof angle between patients, inability to view the contact between the intercondylar roof and the graft, accentuation of roof impingement from anterior tibial translation caused by quadriceps contraction, and the use of tibial guides that rely on soft-tissue landmarks. A surgical technique is presented which consistently places the tibial tunnel in the pathway of the normal ACL (i.e., anatomic placement) and avoids roof impingement. The indications and need for roof- and wallplasty are discussed.
This paper reports on a scientific workshop to study anterior cruciate ligament (ACL) reconstruction. The aim is to present recommendations for ACL reconstruction methods that will be of use for surgeons. A study of knee anatomy and graft placement concluded that the tibial attachment must be posterior enough to avoid graft impingement against the femur, and methods to attain this were presented. On the femur, poor graft placement leads to excessive changes of the graft attachment site separation distance as the knee flexes, and the worst case corresponds to the attachment being too far anterior. It was agreed that there were typical patterns of graft tension changes as the knee flexes, and that grafts should be tensioned close to full knee extension. A typical tensioning protocol would be 60 N tension applied at 10 degrees of flexion. It was recognised that graft remodelling caused uncontrollable tension changes post-operation. Graft twisting, to recreate the anatomical spiral of ACL fibres seen in the flexed knee, was also discussed.
We describe a technique to visualise and then to measure the position of the ACL femoral attachment. A method for removal and accurate replacement of the medial femoral condyle is described. This was shown to provide wide exposure of the intercondylar notch without affecting A-P laxity significantly. A method for navigating around the ACL femoral attachment, using orthogonal micrometers working from a datum at the centre of the posterior lateral femoral condyle, with the diameter of the condyle as a normalising dimension, is also described. The accuracy of these methods was assessed, and they are recommended for experimental work on the ACL.
Although an increasing number of revision anterior cruciate ligament (ACL) reconstructions are being performed each year, the failure rate may be high unless the factors of this unique procedure are addressed. The authors stress the distinction between this procedure and primary ACL surgery, and review the unique strategies which must be considered in order for this procedure to be successful: patient history and examination, preoperative planning, surgical and graft tissue factors, and rehabilitation.
The structure and vascularization of the human anterior and posterior cruciate ligament were investigated by light microscopy, transmission electron microscopy,, injection techniques and by immunohistochemistry. The major part of the anterior and posterior cruciate ligament is composed of bundles of type I collagen. Type III collagen-positive fibrils separate the bundles. The major cell type is the elongated fibroblast, lying solitarily between the parallel collagen fibrils. The histologic structure of the cruciate ligaments is not homogeneous. In both ligaments there is a zone where the tissue resembles fibrocartilage. In the anterior cruciate ligament the fibrocartilaginous zone is located 5-10 mm proximal of the tibial ligament insertion in the anterior portion of the ligament. In the posterior cruciate ligament the fibrocartilage is located in the central part of the middle third. Within those zones the cells are arranged in columns and the cell shape is round to ovoid. Transmission electron microscopy reveals typical features of chondrocytes. The chondrocytes are surrounded by a felt-like pericellular matrix, a high content of cellular organelles and short processes on the cell surface. The pericellular collagen is positive for type II collagen. The major blood supply of the cruciate ligaments arises from the middle geniculate artery. The distal part of both cruciate ligaments is vascularized by branches of the lateral and medial inferior geniculate artery. Both ligaments are surrounded by a synovial fold where the terminal branches of the middle and inferior arteries form a periligamentous network. From the synovial sheath blood vessels penetrate the ligament in a horizontal direction and anastomose with a longitudinally orientated intraligamentous vascular network. The density of blood vessels within the ligaments is not homogeneous. In the anterior cruciate ligament an avascular zone is located within the fibrocartilage of the anterior part where the ligament faces the anterior rim of the intercondylar fossa. The fibrocartilaginous zone of the middle third of the posterior cruciate ligament is also avascular. According to Pauwel's theory of the "causal histogenesis" (1960) the stimulus for the development of fibrocartilage within dense connective tissue is shearing and compressive stress. In the anterior cruciate ligament this biomechanical situation may occur when the ligament impinges on the anterior rim of the intercondylar fossa when the knee is fully extended. Compressive and shearing stress in the center of the middle third of the posterior cruciate ligament may result from twisting of the fiber bundles.
