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ABSTRACT: PURPOSE: To study the effect of increasing patellar thickness (overstuffing) on patellofemoral kinematics in total knee arthroplasty and whether subsequent lateral retinacular release would restore the change in kinematics. METHODS: The quadriceps of eight fresh-frozen knees were loaded on a custom-made jig. Kinematic data were recorded using an optical tracking device for the native knee, following total knee arthroplasty (TKA), then with patellar thicknesses from -2 to +4 mm, during knee extension motion. Staged lateral retinacular releases were performed to examine the restoration of normal patellar kinematics. RESULTS: Compared to the native knee, TKA led to significant changes in patellofemoral kinematics, with significant increases in lateral shift, tilt and rotation. When patellar composite thickness was increased, the patella tilted further laterally. Lateral release partly corrected this lateral tilt but caused abnormal tibial external rotation. With complete release of the lateral retinaculum and capsule, the patella with an increased thickness of 4 mm remained more laterally tilted compared to the TKA with normal patellar thickness between 45° and 55° knee flexion and from 75° onwards. This was on average by 2.4° ± 2.9° (p < 0.05) and 2.°9 ± 3.0° (p < 0.01), respectively. Before the release, for those flexion ranges, the patella was tilted laterally by 4.7° ± 3.2° and 5.4° ± 2.7° more than in the TKA with matched patellar thickness. CONCLUSION: Patellar thickness affects patellofemoral kinematics after TKA. Although lateral tilt was partly corrected by lateral retinacular release, this affected the tibiofemoral kinematics. LEVEL OF EVIDENCE: IV.
Knee Surgery Sports Traumatology Arthroscopy 12/2012; · 2.21 Impact Factor
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ABSTRACT: Establishing the appropriate size of the patellar implant-bone composite is one of the important steps ensuring functional
success in arthroplasty. Conventionally, the patella is measured intraoperatively and its thickness is used to guide the depth
of resection. However, in a diseased joint, this may not reflect the native patellar thickness. We studied the relationship
between the patellar thickness and various patellar dimensions on three-dimensional reconstructed computed tomographic scans
from 37 normal adult knees. Patellar width correlated with thickness. The average patellar width:thickness ratio was 2.0 (standard
deviation, 0.106; 95% confidence interval, 1.96–2.03). The cartilage thickness was on average 2.5mm (standard deviation,
1.0). The width:thickness ratio was similar in 79 digital radiographs taken before TKA of knees without patellofemoral disease
(mean, 2.1; standard deviation, 0.28). When compared with the two other methods for calculating patellar resection described
in the literature, the width:thickness ratio was more reliable. The width:thickness ratio appears anatomically constant and
may be a useful guide for estimating premorbid patellar thickness.
Clinical Orthopaedics and Related Research 04/2012; 466(5):1198-1203. · 2.53 Impact Factor
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ABSTRACT: Total knee arthroplasty (TKA) is a procedure with function dependent upon correct tensioning of the soft-tissue constraints. The purpose of this study was to examine the length-change behaviour of the collateral ligaments during knee flexion-extension before and after TKA. The influence of differing degrees of internal-external rotation of the femoral component on slackening/tightening of the collateral ligaments during knee flexion was to be studied.
The length-change patterns of the collateral ligaments were measured in eight intact knees in vitro: sutures were passed along the ligaments and attached to displacement transducers. Measurements were repeated after TKA with the femoral component in neutral rotation, then with 5° internal and 5° external rotation.
Both the MCL and LCL slackened during knee flexion from 0° to 110° flexion, at all stages of the experiment. In the native knee, the MCL slackened 2 mm, whilst the LCL slackened 7 mm. The MCL slackened a further 3 mm and the LCL a further 4 mm during flexion post-TKA. A 5° external rotation of the femoral component slackened the MCL 2 mm more and tightened the LCL by 2 mm. The opposite effects resulted from 5° internal rotation.
The collateral ligaments slackened more than normal following TKA, and these length changes were increased by femoral component rotation. External rotation of the femoral component to address patellar tracking may slacken the MCL and thus lead to valgus instability in the flexed knee.
Knee Surgery Sports Traumatology Arthroscopy 12/2011; 20(7):1349-56. · 2.21 Impact Factor
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ABSTRACT: Although both anatomic double-bundle and single-bundle anterior cruciate ligament reconstruction procedures are in use, it remains controversial whether the anatomic double-bundle procedure is biomechanically superior.
The anatomic double-bundle procedure would be better than both laterally placed anatomic and nonanatomic transtibial single-bundle procedures at restoring to normal the tibial anterior translation, internal rotation, and pivot-shift instability. It was also hypothesized that tibial internal rotation would be closer to normal after laterally placed anatomic single-bundle reconstruction than after the nonanatomic reconstruction.
Controlled laboratory study.
Eight cadaveric knees were mounted in a 6 degrees of freedom rig and tested using the following loading conditions: 90-N anterior and posterior tibial forces, 5-N·m internal and external tibial rotation torques, and a simulated pivot-shift test. Tibiofemoral kinematics during the flexion-extension cycle were recorded with an optical tracking system for (1) intact, (2) anterior cruciate ligament-deficient knee, (3) anatomic double-bundle reconstruction, (4) nonanatomic single-bundle reconstruction, and (5) laterally placed single-bundle reconstruction.
Rotational laxity with internal tibial torque and anterior laxity in the simulated pivot shift were significantly less in the double-bundle reconstruction and laterally placed single-bundle reconstruction compared with the nonanatomic single-bundle reconstruction. There were no significant differences between the 3 procedures when anterior and posterior tibial translation forces and external rotation torques were applied. In addition, there were no significant differences between the double-bundle reconstruction and laterally placed single-bundle reconstruction.
The postoperative rotational and pivot-shift laxity after anatomic double-bundle anterior cruciate ligament reconstruction was significantly better than that after nonanatomic single-bundle reconstruction. However, there were no significant differences between the double-bundle reconstruction and laterally placed single-bundle reconstruction.
This work suggests that a single-bundle reconstruction may be better able to control both knee laxity and pivot-shift instability if the femoral tunnel is moved to a more lateral position and that then the double-bundle reconstruction may not offer significant further advantages.
The American journal of sports medicine 02/2011; 39(2):279-88. · 3.61 Impact Factor
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ABSTRACT: Several trials have compared the clinical results between anatomic double-bundle and single-bundle anterior cruciate ligament reconstruction procedures. However, it remains controversial whether the anatomic double-bundle procedure is superior to the single-bundle procedure.
The anatomic double-bundle procedure will be better than the single-bundle procedure at resisting anterior laxity, internal rotation laxity, and pivot-shift instability.
Controlled laboratory study.
Eight cadaveric knees were tested in a 6 degrees of freedom rig using the following loading conditions: 90-N anterior tibialforce, 5-N.m internal and external tibial torques, and a simulated pivot-shift test. Tibiofemoral kinematics during the flexion-extension cycle were recorded with an optical tracking system for (1) intact, (2) anterior cruciate ligament-deficient knee, (3) anatomic double-bundle reconstruction, and (4) single-bundle reconstruction placed at 11 o'clock in the intercondylar notch.
There were significant reductions of anterior laxity of 3.5 mm at 20 degrees of flexion, internal rotational laxity of 2.5 degrees at 20 degrees of flexion, and anterior translations (2 mm) and internal rotations (5 degrees ) in the simulated pivot-shift test in the double-bundle reconstruction com-pared with the single-bundle reconstruction. There were no significant differences between the 2 procedures for external rotation laxity.
The postoperative anterior translation and internal rotation stability after anatomic double-bundle anterior cruciate ligament reconstruction were significantly better than after single-bundle reconstruction, in both static tests and the pivot shift.
Unlike previous laboratory studies, this work used clinical arthroscopic methods for anterior cruciate ligament reconstruction, and found that the anatomic reconstruction was superior to a single graft placed at 11 o'clock.
The American journal of sports medicine 07/2010; 38(7):1349-58. · 3.61 Impact Factor
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ABSTRACT: Malrotation of the femoral component may cause patellofemoral complications after total knee replacement (TKR). We hypothesized that femoral component malrotation would cause excessive lengthening of the retinacula. Retinacular length changes were measured by threading fine sutures along them and attaching these to the patella and to displacement transducers. The knee post-TKR was flexed-extended while the quadriceps were tensed, then the measurements repeated after rotating the femoral component 5 degrees internally and then 5 degrees externally. Internal rotation shortened the medial patellofemoral ligament (MPFL) significantly from 100 degrees to 0 degrees extension. External rotation lengthened the MPFL significantly from 90 degrees to 0 degrees extension. The transverse fibers of the lateral retinaculum showed no significant differences. The MPFL attaches directly from bone to bone, so it was lengthened directly by movement of the trochlea and patella, whereas the deep transverse fibers of the lateral retinaculum attach to the mobile iliotibial tract, so they were not lengthened directly.
Journal of Orthopaedic Research 03/2010; 28(9):1136-41. · 2.81 Impact Factor
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ABSTRACT: Differing descriptions of patellar motion relative to the femur have resulted from previous studies. We hypothesized that patellar kinematics would correlate to the trochlear geometry and that differing descriptions could be reconciled by accounting for differing alignments of measurement axes. Seven normal fresh-frozen knees were CT scanned, and their kinematics with quadriceps loading was measured by an optical tracker system. Kinematics was calculated in relation to the femoral epicondylar, anatomic, and mechanical axes. A novel trochlear axis was defined, between the centers of spheres best fitted to the medial and lateral trochlear articular surfaces. The path of the center of the patella was circular and uniplanar (root-mean-square error 0.3 mm) above 16+/-3 degrees (mean+/-SD) knee flexion. In the coronal plane, this circle was aligned 6+/-2 degrees from the femoral anatomical axis, close to the mechanical axis alignment. It was 91+/-3 degrees from the epicondylar axis, and 88+/-3 degrees from the trochlear axis. In the transverse plane it was 91+/-3 degrees and 88+/-3 degrees from the epicondylar and trochlear axes, respectively. Manipulation of the data to different axis alignments showed that differing previously published data could be reconciled. The circular path of patellar motion around the trochlea, aligned with the mechanical axis of the leg, is easily visualized and understood.
Journal of Orthopaedic Research 11/2009; 28(5):589-94. · 2.81 Impact Factor
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ABSTRACT: We carried out a prospective study of 47 Exeter (Stryker Inc, Warsaw, Ind) small stem total hip arthroplasty in 42 patients with an average age of 58 years and a mean follow-up of 8.5 years. The Oxford hip score improved from a preoperative mean of 47 to 17 at last follow-up. More than 87% patients had excellent or good Harris hip scores, and 90% were able to walk with little or no pain. Stem subsidence within the cement mantle was observed in 26% of cases, and none showed evidence of aseptic loosening or implant failure. Two stems were removed due to infection. The survival rate of this implant was 95.7% at 10 years. This first series of Exeter small stem showed excellent medium-term results, comparable to its larger counterparts.
The Journal of arthroplasty 09/2009; 24(8):1200-4. · 1.79 Impact Factor
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ABSTRACT: Although lateral retinacular releases are not uncommon, there is very little scientific knowledge about the properties of these tissues, on which to base a rationale for the surgery. We hypothesised that we could identify specific tissue bands and measure their structural properties. Eight fresh-frozen knees were dissected, and the lateral soft tissues prepared into three distinct structures: a broad tissue band linking the iliotibial band (ITB) to the patella, and two capsular ligaments: patellofemoral and patellomeniscal. These were individually tensile tested to failure by gripping the patella in a vice jaw and the soft tissues in a freezing clamp. Results: the ITB-patellar band was strongest, at a mean of 582N, and stiffest, at 97 N/mm. The patellofemoral ligament failed at 172 N with 16 N/mm stiffness; the patellomeniscal ligament failed at 85 N, with 13N/mm stiffness. These structural properties suggest that most of the load in-vivo is transmitted to the patella by the transverse fibres that originate from the ITB.
Journal of biomechanics 08/2009; 42(14):2323-9. · 2.66 Impact Factor
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ABSTRACT: The iliotibial band (ITB) has an important role in knee mechanics and tightness can cause patellofemoral maltracking. This study investigated the effects of increasing ITB tension on knee kinematics. Nine fresh-frozen cadaveric knees had the components of the quadriceps loaded with 175 N. A Polaris optical tracking system was used to acquire joint kinematics during extension from 100 degrees to 0 degrees flexion. This was repeated after the following ITB loads: 30, 60 and 90 N. There was no change with 30 N load for patellar translation. On average, at 60 and 90 N, the patella translated laterally by 0.8 and 1.4mm in the mid flexion range compared to the ITB unloaded condition. The patella became more laterally tilted with increasing ITB loads by 0.7 degrees, 1.2 degrees and 1.5 degrees for 30, 60 and 90 N, respectively. There were comparable increases in patellar lateral rotation (distal patella moves laterally) towards the end of the flexion cycle. Increased external rotation of the tibia occurred from early flexion onwards and was maximal between 60 degrees and 75 degrees flexion. The increase was 5.2 degrees, 9.5 degrees and 13 degrees in this range for 30, 60 and 90 N, respectively. Increased tibial abduction with ITB loads was not observed. The combination of increased patellar lateral translation and tilt suggests increased lateral cartilage pressure. Additionally, the increased tibial external rotation would increase the Q angle. The clinical consequences and their relationship to lateral retinacular releases may be examined, now that the effects of a tight ITB are known.
Journal of biomechanics 06/2009; 42(10):1539-46. · 2.66 Impact Factor
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ABSTRACT: Patellofemoral dysfunction following total knee replacement (TKR) is a significant clinical problem, but little information exists on the mechanics of the patellofemoral retinacula or the effects of TKR on these structures. We hypothesized that TKR would cause significant elongation of the retinacula. Retinacular length changes were measured by threading sutures along the retinacula, fixing the sutures to the patella and the iliotibial band (ITB), and attaching the femoral ends to displacement transducers. The intact knee was flexed-extended while the quadriceps and ITB were tensed and the retinacular length change patterns were recorded. The measurements were repeated post-TKR. The medial patellofemoral ligament (MPFL) was close to isometric, stretching 2 mm in terminal knee extension, whereas the lateral retinaculum slackened 8 mm from 110 degrees to 0 degrees flexion. TKR did not cause significant elongation of either of the retinacula, the largest change being 3 mm elongation of the MPFL around 40 degrees , which stretched the MPFL by 1.4 mm above its maximum natural length. Thus, this work did not support the hypothesis that TKR causes significant elongation of the retinacula sufficient to affect knee function.
Journal of Orthopaedic Research 02/2009; 27(7):865-70. · 2.81 Impact Factor
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ABSTRACT: Patient selection for lateral retinacular release (LRR) and its efficacy are controversial. Iatrogenic medial subluxation can occur with inappropriate LRR. The aim of this study was to determine the reduction in patellofemoral stability with progressively more extensive LRR. The force required to displace the patella 10mm medially and laterally in nine cadaveric knees was measured with and without loading of the quadriceps and iliotibial band. The knee was tested intact, then after progressive release beginning proximal to the patella (PR), the mid-level between the proximal and distal limit of the patella (MR) where the fibres are more transverse, then distally till Gerdy's tubercle (DR) and finally the joint capsule (CR). Both medial and lateral stability decreased with progressive releases, larger for the medial. The MR caused a significant reduction of lateral stability between 30 degrees and 90 degrees of knee flexion. There was an 8% reduction in medial stability at 0 degrees flexion with a complete LRR (DR). A comparable reduction in medial stability in the loaded knee at 20 degrees and 30 degrees flexion was obtained with MR alone, with no further reduction after DR. A capsular release caused a further reduction in medial stability at 0 degrees and 20 degrees and this was marked in the unloaded knee. In extension, the main lateral restraint was the joint capsule. At 30 degrees flexion, the transverse fibres were the main contributor to the lateral restraint.
Journal of Biomechanics 02/2009; 42(3):291-6. · 2.43 Impact Factor
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ABSTRACT: This paper describes a longitudinal patellar-splitting approach to the knee that includes provision for accurate reconstruction. Our in vitro experiments showed that patellofemoral kinematics and length-change patterns of specific bands of the peripatellar retinacula were not changed significantly by opening and closing the knee via the transpatellar approach. This surgical approach will be useful for in vitro experiments on the knee, when effects due to alterations of internal structures such as cruciate ligament reconstructions or joint replacement are to be studied, avoiding confounding effects caused by changes to the retinacula.
Journal of Orthopaedic Research 11/2008; 27(3):330-4. · 2.81 Impact Factor
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ABSTRACT: This study investigated the effect of loading the iliotibial band (ITB) on the stability of the patellofemoral joint. We measured the restraining force required to displace the patella 10 mm medially and laterally (defined as medial and lateral stability, respectively) in 14 fresh-frozen knees from 0 to 90 degrees knee flexion. The testing rig allowed the patella to rotate and translate freely during this displacement. The quadriceps was separated into five components and loaded with 175 N total tension. Testing was performed at 0 to 90 N ITB tension. With no ITB tension, the lateral restraining force ranged from 82 to 101 N across 0 to 90 degrees flexion. Increasing ITB tension caused progressive reduction of the lateral restraining force. The maximum reduction was 25% at 60 degrees flexion and 90 N ITB tension. Medial restraining force increased progressively with increasing knee flexion and increasing ITB loads; it ranged from 74 N at 0 degrees knee flexion and 0 N ITB tension to 211 N at 90 degrees knee flexion and 90 N ITB tension. The maximum effect was an increase of medial restraining force of 50% at 90 degrees flexion and 90 N ITB tension.
Journal of Orthopaedic Research 11/2008; 27(3):335-9. · 2.81 Impact Factor
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ABSTRACT: Optimal patellar tracking and component alignment are important in achieving a well-functioning total knee arthroplasty (TKA). The patella is constrained partly by design of the prosthetic trochlear groove, and patellar tracking is governed by a combination of static and dynamic factors. Maltracking may result from excessive or unbalanced tension in the surrounding soft tissues. This article describes a staged progressive lateral release of the patellar retinaculum in TKA, which is classified into 6 stages. Stage 1 transects the deep lateral patellofemoral ligament; stages 2 to 6 extend the lateral patellar incision distally from vastus lateralis to the tibial tubercle. This technique was used in a series of 96 primary TKAs. We report the rates of the various stages of lateral release and the variables that might affect the decision to perform such a release.
The Journal of arthroplasty 06/2008; 24(5):735-42. · 1.79 Impact Factor
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ABSTRACT: Establishing the appropriate size of the patellar implant-bone composite is one of the important steps ensuring functional success in arthroplasty. Conventionally, the patella is measured intraoperatively and its thickness is used to guide the depth of resection. However, in a diseased joint, this may not reflect the native patellar thickness. We studied the relationship between the patellar thickness and various patellar dimensions on three-dimensional reconstructed computed tomographic scans from 37 normal adult knees. Patellar width correlated with thickness. The average patellar width:thickness ratio was 2.0 (standard deviation, 0.106; 95% confidence interval, 1.96-2.03). The cartilage thickness was on average 2.5 mm (standard deviation, 1.0). The width:thickness ratio was similar in 79 digital radiographs taken before TKA of knees without patellofemoral disease (mean, 2.1; standard deviation, 0.28). When compared with the two other methods for calculating patellar resection described in the literature, the width:thickness ratio was more reliable. The width:thickness ratio appears anatomically constant and may be a useful guide for estimating premorbid patellar thickness.
Clinical Orthopaedics and Related Research 06/2008; 466(5):1198-203. · 2.53 Impact Factor
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ABSTRACT: The Fitmore titanium mesh cementless acetabular component in 115 hip arthroplasties was reviewed at an average of 33 months of follow-up. None were revised nor had infection. One hip dislocated 4 years postoperatively. Two femoral components were revised. The average Harris Hip Score at the last follow-up was 90 points. In the 96 sets of radiographs available, there was no loosening or new radiolucency. One hip had nonprogressive osteolysis adjacent to a screw. This press-fit cup has its polar region flattened and is rim loading. Noncontact (gaps) at the acetabular floor is expected and is not critical for fixation. In all but 6 hips, these gaps filled. In 5 hips, a minimal gap (<or=0.5 mm) remained in part of the equatorial region. The Fitmore cup osseointegrates successfully.
The Journal of Arthroplasty 09/2006; 21(6):846-51. · 2.38 Impact Factor
