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Influence of collateral ligament laxity on patient satisfaction after total knee arthroplasty: A comparative bilateral study

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Influence of collateral ligament laxity on patient satisfaction after total knee arthroplasty: A comparative bilateral study

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Abstract

Correct ligamentous balancing is an important determinant of the clinical outcome in total knee arthroplasty (TKA). Many surgeons prefer a tight rather than a lax knee during implantation of a TKA. The hypothesis in this study was that patients with a slightly laxer knee joint might perform better than patients with a tight knee joint after implantation of a TKA. Twenty-two patients with bilateral knee arthroplasties were clinically and radiologically evaluated at a mean follow-up of 4.5 years, ranging from 2 to 7 years. There were 12 women and 10 men with an average age of 68.9 years (range 32-82 years) at the time of surgery. A modified HSS score (excluding laxity), varus and valgus stress X-rays in 30 degrees of knee flexion, and the subjective outcome of both knees were compared. A knee was considered tight when it opened less than 4 degrees and lax if it opened 4 degrees or more on stress X-ray. There was a trend towards improved range of motion and HSS score for the laxer knee joints. However, the difference did not achieve statistical significance. Eleven of the 22 patients considered one side subjectively better than the other side. In 10 out of these 11 TKA, the slacker knee joint was the preferred side ( p<0.05). As the present study compared bilateral knee joints after TKA, the same patient could act as a control group, and subtle subjective differences were revealed which are not quantifiable. The results showed that patients with a preferred side felt significantly more comfortable on the laxer side, indicating that during intraoperative ligamentous tensioning, some varus and valgus laxity at 20-30 degrees of flexion might be preferable to an over-tight knee joint. Further biomechanical and prospective investigations will be necessary to establish the correct soft-tissue tensioning.

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... These biomechanical findings suggest that increased flexion gap might result in better postoperative ROM while not influencing knee stability. Several clinical comparative studies have also indicated increased patient satisfaction in slightly lax knees [7,17]. However, most of these studies did not intentionally increase the flexion gap, and little clinical research has been published to evaluate the above cadaver findings. ...
... In a clinical comparative study on bilateral TKAs, Kuster et al. [17] showed that patients favoured the laxer to the tighter knees, indicating that a certain laxity in TKA might feel more normal. This lead to a cadaver study [15], which showed that increased flexion gap could have a positive effect on postoperative flexion and ligament strain without affecting knee stability. ...
... The fear that a greater flexion gap could result in instability in deep flexion was not confirmed and postoperative knee laxity did not differ between the two groups. Slight laxity could be favourable as it has been shown to improve patient-reported results [7,17]. Finally the appropriate choice of outcome measurements seems to be important to distinguish between well and very well-functioning knee replacements. ...
Article
Purpose Increased range of motion (ROM) while maintaining joint stability is the goal of modern total knee arthroplasty (TKA). A biomechanical study has shown that small increases in flexion gap result in decreased tibiofemoral force beyond 90° flexion. The purpose of this paper was to investigate clinical implications of controlled increased flexion gap. Methods Four hundred and four TKAs were allocated into one of two groups and analysed retrospectively. In the first group (n = 352), flexion gap exceeded extension gap by 2.5 mm, while in the second group (n = 52) flexion gap was equal to the extension gap. The procedures were performed from 2008 to 2012. The patients were reviewed 12 months postoperatively. Objective clinical results were assessed for ROM, mediolateral and sagittal stability. Patient-reported outcome measures were the WOMAC score and the Forgotten Joint Score (FJS-12). Results After categorizing postoperative flexion into three groups (poor < 90°, satisfactory 91°–119°, good ≥ 120°) significantly more patients in group 1 achieved satisfactory or good ROM (p = 0.006). Group 1 also showed a significantly higher mean FJS-12 (group 1: 73, group 2: 61, p = 0.02). The mean WOMAC score was 11 in the first and 14 in the second group (n.s.). Increase in flexion gap did not influence knee stability. Conclusions The clinical relevance of this study is that a controlled flexion gap increase of 2.5 mm may have a positive effect on postoperative flexion and patient satisfaction after TKA. Neither knee stability in the coronal and sagittal planes nor complications were influenced by a controlled increase in flexion gap. Level of evidence III.
... The current recommendations for TKA balance lack detail and may have oversimplified which balance parameters contribute to better TKA outcomes. 3,[5][6][7][8][9][10][11][12][13][14][15] There is data to support that a total varus-valgus arc of movement in extension or early flexion of 6 to 8 degrees is optimal. Ishii and Matsuda in separate studies utilizing a telos arthrometer in maximum extension both concluded that approximately 4 degrees each of medial and lateral laxity in full extension was an appropriate surgical goal that provided satisfactory clinical outcomes. ...
... They found lax joints, those with 4 degrees or more of medial or lateral opening, had significantly improved range of motion (ROM) and clinical outcomes. 7 Edwards et al conducted a study investigating postoperative laxity in 20 degrees of flexion and found mild-to-moderate degrees of laxity were not detrimental to long-term clinical outcomes. Their measurement of laxity was subjective. ...
... 13,14 Differing prostheses, such as posterior stabilized (PS), CR, and rotating platform-CR and substituting TKA, were utilized across the studies that made these laxity recommendations. [5][6][7][8][9][10][11][12][13][14][15] Few studies to date have specifically studied PS TKA in terms of optimal soft tissue laxity with varied findings. These include one study where subjective measurements were taken only in 30 degrees of flexion which limits the strength of its recommendations. ...
Article
Soft tissue balancing, while accepted as crucial to total knee arthroplasty (TKA) outcomes, is incompletely defined as the subject of broad recommendations. We analyzed 120 computer-assisted, posterior stabilized TKA undertaken for osteoarthritis. Coronal plane laxity was measured, in the 91 varus and 29 valgus knees, prior to any bone resection or soft tissue release, and again after implant insertion. Soft tissue laxity parameters were correlated to the American Knee Society Score (2011) at a minimum follow-up of 12 months with a focus on patient function and satisfaction. Thirteen specific laxity parameters showed a significant correlation to satisfaction, one parameter correlated to function, and another to both functional and satisfaction outcomes. Most correlations were weak, the strongest related to postoperative decreases in coronal plane laxity. Greater preoperative varus but not valgus deformity was associated with higher satisfaction scores. Additionally, 30 patients who reported 40 of 40 satisfaction and that their TKA knee felt normal at all times did not have soft tissue balancing parameters distinguishing them from other subjects. Patient satisfaction and function outcomes demonstrated limited correlation to coronal plane soft tissue parameters. It appears that optimizing TKA satisfaction and function is not as simple as producing a narrow range of coronal laxity parameters. The ongoing debate around optimal coronal plane alignment and its subsequent effect on coronal plane soft tissues may not be as independently important as currently argued. Soft tissue balance may need to be considered as a more complex global envelope.
... The negative effect of overly tight ligaments on knee motion and prosthetic survival has also been described previously [1,17,31,35]. A few studies have reported the influence of ligament balance measured postoperatively on functional outcome after TKA [9,18,20]. They concluded that relatively loose knees perform better than tight knees. ...
... Most previous studies investigated laxity that was measured clinically or radiographically postoperatively [9,18,20,33]. In order to correct unacceptable results before the end of the surgical procedure, orthopaedic surgeons need information on the relationship between laxity measured intraoperatively and outcome. ...
... The findings in this study differ from those in earlier reports where functional outcome was found to be better in lax knees. In the studies by Kuster et al. [18] and Edwards et al. [9] laxity measurements were performed in 30°and n.s. 20°of flexion, respectively. ...
Article
Purpose To find out if there is an association between ligament laxity measured intraoperatively and functional outcome 1 year after total knee arthroplasty (TKA). Methods Medial and lateral ligament laxities were measured intraoperatively in extension and in 90° of flexion in 108 patients [122 knees; median age 70 (range 42–83) years]. Mechanical axes were measured preoperatively and at 1-year follow-up. Outcome measures were the Knee Injury and Osteoarthritis Outcome Score (KOOS), the Knee Society Clinical Rating System, the Oxford Knee Score and patient satisfaction. The relationships between laxity and outcome scores were examined by median regression analyses. Results Post-operative mechanical axis had a significant effect on the association between ligament laxity and KOOS. Therefore, the material was stratified on post-operative mechanical axis. In perfectly aligned and valgus-aligned TKAs, there was a negative correlation between medial laxity and all subscores in KOOS. The most important regression coefficient (β) was recorded for the effect of medial laxity in extension on activities of daily living (ADLs) (β = −7.32, p < 0.001), sport/recreation (β = −6.9, p = 0.017) and pain (β = −5.9, p = 0.006), and for the effect of medial laxity in flexion on ADLs (β = −3.11, p = 0.023) and sport/recreation (β = −4.18, p = 0.042). Conclusions In order to improve the functional results after TKA, orthopaedic surgeons should monitor ligament laxity and mechanical axis intraoperatively and avoid medial laxity more than 2 mm in extension and 3 mm in flexion in neutral and valgus-aligned knees. Level of evidence II.
... 1,14 Previous studies suggested that some degree of knee instability (5-10 mm) in the anteroposterior (AP) direction gives satisfactory results including ROM in mid-flexion or 90 flexion; however, recent studies suggested that midflexion AP instability was related to poor outcome after TKA. [15][16][17][18][19][20][21][22] These studies have conducted investigations of a CR or PS design; however, no study evaluated correlation between mid-flexion instability and postoperative outcomes in the UC-type insert. ...
... However, to the best of our knowledge, including our results, a favorable result of fixed-bearing UC was demonstrated when comparing with fixed-bearing PS. 1,14 It is controversial if there is correlation between AP stability and ROM, some previous studies have demonstrated that greater AP translation is correlated with better postoperative ROM in PS-and CR-type TKA, these studies suggested that additional flexion gap than extension gap occurred better flexion range. [15][16][17][18][19][20][21] We think these previous results supported our results that patients with "fair" stability showed greater ROM than "good" stability regardless of insert design. Some previous studies reported AP translation of 5-10 mm was related to similar or better patients' clinical outcomes. ...
Article
Full-text available
Purpose (1) To compare postoperative range of motion (ROM), stability, and clinical outcomes between fixed-bearing posterior-stabilized (PS) and ultracongruent (UC). (2) The effect of postoperative stability on ROM and clinical outcomes was also evaluated in both designs. Materials and methods Propensity score matching was conducted for age, gender, body mass index, preoperative ROM, Western Ontario and McMaster Universities Osteoarthritis (WOMAC) index, Knee Society (KS) scores, hip–knee–ankle (HKA) alignment, and follow-up period. Two hundred patients (100 PS and 100 UC) were enrolled. Preoperative and final follow-up outcomes including postoperative ROM, anteroposterior (AP) stability (good, fair, and poor), WOMAC index, and KS scores were compared. Then, postoperative outcomes compared between the PS and UC. We also analyzed if AP stability was associated with the postoperative outcomes in both implant designs. Results In both groups, ROM and clinical outcomes of final follow-up showed improvement than preoperation. Statistical significance was not determined between the PS and UC groups in terms of postoperative ROM (PS vs. UC, 134.6° vs. 133.4°, p = 0.13), stability (good/fair/poor, 91/9/0 vs. 84/14/0, p = 0.376), WOMAC index, KS scores, and outliers of HKA alignment (15% vs. 10%, p = 0.393). “Fair” stability showed inferior KS scores but greater ROM than “good” stability in both designs. Conclusion TKA with UC insert provided similar ROM, AP stability, and clinical outcomes when compared to PS insert. In both designs, greater postoperative ROM was found but inferior clinical outcomes were found when TKA resulted in fair stability instead of good stability. Level of evidence III Retrospective comparative study.
... However, some investigators argue that a certain degree of laxity in the joint may be related to decreased postoperative pain and a better range of motion [12;13]. Opinions in the literature differ about which type of meticulous liga mental alignment will ensure the best outcome [14][15][16]. ...
... Nie któ rzy au to rzy do wo dzą, iż pe wien sto pień "lu zu" w sta wie jest nie zbęd ny i przy czy nia się do zmniej sze nia odczu wa nia bó lu po ope ra cyj ne go, a ta kże umo żli wia więk szy za kres ru chu [12,13]. Opi nie w do stęp nym pi śmien nic twie w kwe stii wy bo ru opty mal ne go balan su wię za dło we go, któ ry za pew niał by naj lep szy wy nik kli nicz ny, są po dzie lo ne [14][15][16]. ...
Article
Background: Total knee arthroplasty in joints with valgus or varus deformity is technically demanding. Careful soft tissue balance as well as restitution of anatomical knee axis has a profound effect on postoperative function of the joint, however little is known about differences in subjective stability following surgery between preoperative valgus and varus knees. Material and methods: Studied group consisted of 60 patients who underwent total condylar knee arthroplasty with one type of implant (Stryker Triathlon). Mean follow-up was 2,9 years (1-6 years). The group included 25 patients with valgus and 35 patients with varus preoperative deformity. All patients filled Knee Injury and Osteoarthritis Outcome Score (KOOS) forms. Detailed clinical and radiological assessment was performed. Results: Mean KOOS score was slightly higher in patients with varus deformity, as compared to cases with valgus deformity. At physical examination higher LCL deficiency rate was observed in varus knees. Subjective instability was reported by eight patients (5 valgus and 3 varus). In all cases instability coexisted with decreased MCL tightness and implant position was correct in those patients. No subjective instability was reported by patients with clinical LCL deficiency. Furthermore KOOS scores in these patients were higher (85,8) as compared to cases with decreased MCL tension (79,1). Conclusions: 1. In patients with proper implant alignment subjective instability is related to postoperative MCL deficiency, regardless preoperative deformity in coronal plane. 2. The post-op LCL laxity does not compromise subjective stability, nor influence subjective outcome, as demonstrated with KOOS scores.
... In this situation, malposition such as internal rotation of the femoral or tibial components is a known cause of reduced satisfaction [4,6,7,16]. In addition, dissatisfaction might be due to postoperative 1 3 medial-lateral ligament imbalance [3,17,25,30], but it is not known how much intraoperative ligament imbalance during flexion is permitted. ...
... On the other hand, this study showed that ROM was almost the same postoperatively as preoperatively, regardless of medial joint laxity at 90° flexion. The relationship between postoperative ROM or patient satisfaction and ligament balancing is controversial [17,34]. Limited postoperative ROM has certainly been shown to lead to patient dissatisfaction [19]. ...
Article
Full-text available
Introduction: The relationship between postoperative tibiofemoral ligament balance and patient satisfaction in total knee arthroplasty (TKA) has been explored previously. However, the optimal intraoperative medial-lateral ligament balance during knee flexion in terms of postoperative patient satisfaction remains unknown. We evaluated the effect of intraoperative flexion instability on patient satisfaction after TKA. Materials and methods: This study consisted of 46 knees with varus osteoarthritis undergoing TKA. Medial-lateral component gaps at 0° knee extension and 90° flexion were measured intraoperatively using a knee balancer. Differences in postoperative patient outcomes at 3 weeks and 1 year were compared between medially tight knees in 90° flexion with a medial component gap of < 4 mm and medially loose knees in 90° flexion with a gap of ≥ 4 mm. Outcomes were measured using the 2011 Knee Society Scoring System (2011 KS). Results: The median total 2011 KS score at 1 year postoperatively in the medially loose knees [median 97; interquartile range (IQR) 75-117] was significantly lower than that in the medially tight knees (median 128; IQR 104-139, P < 0.01), while preoperative and 3-week postoperative scores were similar. In addition, medial flexion gaps were not significantly associated with total 2011 KS scores before surgery or at 3 weeks postoperatively. However, at 1 year after surgery, medial component flexion gaps were negatively associated with the total 2011 KS score (R = - 0.42; P < 0.01) and the 2011 KS satisfaction subscale score (R = - 0.36; P = 0.01). Conclusions: Excessive intraoperative medial joint laxity of ≥ 4 mm at 90° flexion progressively decreased patient satisfaction for 1 year. Since intraoperative medial laxity in flexion is likely to interfere with functional recovery after TKA, medial stabilization during TKA is important throughout knee flexion. Level of evidence: Therapeutic study, Level III.
... A key contributor to medial knee stability is the medial collateral ligament (MCL), which, in the intact knee, is the primary restraint to tibial abduction under valgus loading, prevents external rotation when the knee is flexed [1], and serves as a secondary restraint to anterior tibial translation [2][3][4]. For knee arthroplasty patients, the MCL may play an even more crucial role, as other stabilizing ligaments are often sacrificed during surgery (e.g., the anterior cruciate ligament [5]), and maintaining a stable knee can be critical to implant success [6][7][8][9][10] and patient satisfaction [11]. The MCL is also frequently injured as it is involved in 42% of all ligamentous injuries in the knee [12]. ...
... For example, there is evidence that MCL-deficient knees show significantly greater values of absolute gap width compared with intact knees [24,25,33], and medial gap width may be a suitable method for assessing the efficacy of MCL repair [25]. Varus/valgus instability post-arthroplasty, which has been linked to patient satisfaction [11], and is often assessed clinically with radiographic examination, may also be possible to evaluate with ultrasound, though reverberation artifacts off of the metallic prosthesis [41] may make gap width measures more challenging in these cases. ...
Article
Full-text available
Introduction Medial knee instability is a key clinical parameter for assessing ligament injury and arthroplasty success, but current methods for measuring stability are typically either qualitative or involve ionizing radiation. The purpose of this study was to perform a preliminary analysis of whether ultrasound (US) could be used as an alternate approach for quantifying medial instability by comparing an US method with an approach mimicking the current gold standard fluoroscopy method. Materials and methods US data from the medial knee were collected, while cadaveric lower limbs (n = 8) were loaded in valgus (10 Nm). During post-processing, the US gap width was measured by identifying the medial edges of the femur and tibia and computing the gap width between these points. For comparison, mimicked fluoroscopy (mFluoro) images were created from specimen-specific bone models, developed from segmented CT scans, and from kinematic data collected during testing. Then, gap width was measured in the mFluoro images based on two different published approaches with gap width measured either at the most medial or at the most distal aspect of the femur. Results Gap width increased significantly with loading (p < 0.001), and there were no significant differences between the US method (unloaded: 8.7 ± 2.4 mm, loaded: 10.7 ± 2.2 mm) and the mFluoro method that measured gap width at the medial femur. In terms of the change in gap width with load, no correlation with the change in abduction angle was observed, with no correlation between the various methods. Inter-rater reliability for the US method was high (0.899–0.952). Conclusions Ultrasound shows promise as a suitable alternative for quantifying medial instability without radiation exposure. However, the outstanding limitations of existing approaches and lack of true ground-truth data require that further validation work is necessary to better understand the clinical viability of an US approach for measuring medial knee gap width.
... After removal of duplicates 3,228 studies were screened based on title, abstract, and in some cases full text. 34 full-text articles were assessed for eligibility and 14 articles fulfilled the criteria (Yamakado et al. 2003, Kuster et al. 2004, Ishii et al. 2005, Jones et al. 2006, Seon et al. 2007, Van Hal et al. 2007, Seon et al. 2010, Schuster et al. 2011, Seah et al. 2012, Nakahara et al. 2015, Oh et al. 2015, Graff et al. 2016, Tsukiyama et al. 2017, Matsumoto et al. 2017 (Figure). ...
... The methods used are to the best of our knowledge not yet validated. 1 study reported validation by double measurements of 4 patients, which in this particular study equals 8 knees and 16 radiographs; the results from the double measurements are reported to lie within 1°, but the results are not described statistically (Kuster et al. 2004). Reading of angulation from coronal stress radiography is validated (Nakahara et al. 2015, Hatayama et al. 2017. ...
Article
Full-text available
Background and purpose — Instability following primary total knee arthroplasty (TKA) is, according to all national registries, one of the major failure mechanisms leading to revision surgery. However, the range of soft-tissue laxity that favors both pain relief and optimal knee function following TKA remains unclear. We reviewed current evidence on the relationship between instrumented knee laxity measured postoperatively and outcome scores following primary TKA. Patients and methods — We conducted a systematic search of PubMed, Embase, and Cochrane databases to identify relevant studies, which were cross-referenced using Web of Science. Results — 14 eligible studies were identified; all were methodologically similar. Both sagittal and coronal laxity measurement were reported; 6 studies reported on measurement in both extension and flexion. In knee extension from 0° to 30° none of 11 studies could establish statistically significant association between laxity and outcome scores. In flexion from 60° to 90° 6 of 9 studies found statistically significant association. Favorable results were reported for posterior cruciate retaining (CR) knees with sagittal laxity between 5 and 10 mm at 75–80° and for knees with medial coronal laxity below 4° in 80–90° of flexion. Interpretation — In order to improve outcome following TKA careful measuring and adjusting of ligament laxity intraoperatively seems important. Future studies using newer outcome scores supplemented by performance-based scores may complement current evidence.
... A JL elevation above 5 mm 1 3 might cause mid-flexion instability [22,27]. In general, a slight laxity is associated with a better outcome [15]. ...
Article
Full-text available
Purpose: The epicondylar ratio (ER) is used to restore the individual joint line (JL), especially in revision total knee arthroplasty. It was first described in magnetic resonance imaging (MRI) but is usually applied to a.p. radiographs of the knee for preoperative planning. The objective of the current study was to define reliable landmarks in MRI and X-ray images of the knee, which allow comparison of the image modalities. Furthermore, the correlation of the measured ER in MRI and X-rays of the knee was calculated. Methods: A consecutive series of 87 patients who underwent an arthroscopical intervention of the knee were included into the present study. The lateral epicondyle was defined as the most lateral and distal prominence. On the medial side, the measurement was aligned to the epicondylar sulcus. The medial and lateral ER were calculated by dividing the perpendicular distance from the JL to the epicondyle by the transepicondylar distance. One observer determined the ER twice to calculate the intramethod intraobserver agreement, and a second observer obtained the intramethod interobserer agreement. The ER obtained from X-ray and MRI was compared to calculate the intermethod correlation. Results: The average lateral ER was 0.29 on X-ray versus 0.28 on MRI. The average medial ER was 0.33 and 0.33, respectively. Intramethod agreement ranged from 0.66 to 0.88 and intermethod correlation from 0.49 to 0.57. Conclusions: The ER can be determined reliably on MRI and X-ray images of the knee. The correlation of the ER in MRI and X-ray is fair.
... Finally, optimal ligament balancing has until recently been unknown. Some earlier reports that compared lax and tight TKAs found better functional outcomes in lax knees (Edwards et al. 1988, Kuster et al. 2004). However, during the last decade different research groups have come to conclusions or recommendations that seem to resemble each other. ...
Article
Full-text available
Background and purpose — In the classical mechanical alignment technique, ligament balancing is considered a prerequisite for good function and endurance in total knee arthroplasty (TKA). However, it has been argued that ligament balancing may have a negative effect on knee function, and some authors advocate anatomic or kinematic alignment in order to reduce the extent of ligament releases. The effect of the trauma induced by ligament balancing on functional outcome is unknown; therefore, the aim of this study was to investigate this effect. Patients and methods — 129 knees (73 women) were investigated. Mean age was 69 years (42–82), and mean BMI was 29 (20–43). Preoperatively 103 knees had a varus deformity, 21 knees had valgus deformity, and 5 knees were neutral. The primary outcome measure was the Knee injury and Osteoarthritis Outcome Score (KOOS). Secondary outcome measures were the Oxford Knee Score (OKS) and patient satisfaction (VAS). All ligament releases were registered intraoperatively and outcome at 3 years’ follow-up in knees with and without ligament balancing was compared Results — 86 knees were ligament balanced and 43 knees were not. Ligament-balanced varus knees had more preoperative deformity than varus knees without ligament balancing (p = 0.01). There were no statistically significant differences in outcomes between ligament-balanced and non-ligament-balanced knees at 3 years’ follow-up. No correlation was found between increasing numbers of soft tissue structures released and outcome. Interpretation — We did not find any negative effect of the trauma induced by ligament balancing on knee function after 3 years.
... One explanation for this hypothesis can be found in the cadaveric study by Delport et al. [10] as the strains in the collateral ligaments closely resembled the preoperative pattern of the native knee specimens when constitutional alignment was restored. As the soft-tissue tension is important for providing neurosensory feedback, taking into consideration the preoperative alignment might influence the patients' satisfaction [16,23]. ...
Article
Purpose: The optimal coronal alignment is still under debate. However, in most of the studies, alignment was only assessed using radiographs, which are not accurate enough for assessment of tibial and femoral TKA position. The primary purpose of this study was to assess the relationship between coronal TKA alignment using 3D-reconstructed CTs and clinical outcome in patients with preoperative varus in comparison with patients with natural or valgus deformity. It was the hypothesis that neutral limb alignment shows a better outcome after TKA. Methods: Prospectively collected data of 38 patients were included. The clinical and radiological follow-up was 24 months. The patients were grouped into two groups with regard to their preoperative limb alignment. Group A (varus) consisted of 21 patients with preoperative varus of 3° or more, while group B (non-varus) consisted of 17 patients with neutral (- 3 < 0 > + 3) or valgus alignment (> + 3). For assessment of TKA component position and orientation, 3D-reconstructed CT was used. The measurements of the deviation from the whole limb mechanical axis (HKA angle) and the joint line alignment in the femoral (mLDFA) and the tibial side (MPTA) were assessed in the preoperative leg as well as during follow-up after TKA. For clinical outcome assessment, the Knee Society Score (KSS) was used at 1 and 2 years postoperatively. Correlation between KSS score and each variable was done using a linear and quadratic regression model (p < 0.05). Results: The mean postoperative HKA angle was - 1.3 (varus) in the varus group and + 1.4 (valgus) in the non-varus group. Overall, significant correlations between the preoperative and postoperative alignments were found. In the preoperatively non-varus group, a highly significant correlation was found between neutral limb alignment (HKA = 0° ± 3°) and higher KSS (r2 = 0.74, p = 0.00). In the varus group, no correlation was found between the postoperative whole limb alignment and the components' position in the coronal plane to KSS score. Conclusion: A significant correlation was found between neutral limb alignment and higher KSS only in patients with preoperative non-varus alignment. The concept of constitutional varus alignment is still under debate. Moreover, it appears that one should aim for a more individualized, alignment target based on the individual knee morphotype. Level of evidence: Diagnostic study, Level II.
... Currently, the etiology of sub-optimal knee function is largely unknown but since total knee arthroplasty relies on the surrounding soft tissue for mechanical stability, lax ligaments (Aunan et al., 2015;Nakano et al., 2016;Kuster et al., 2004) and/or weak muscles (Stevens-Lapsley et al., 2010;Mizner and Snyder-Mackler, 2005;LaStayo et al., 2009), have been suggested as possible etiologies. During surgery, ligaments such as the anterior-cruciate ligament (ACL) or posteriorcruciate ligament (PCL) are resected while the medial and lateral collateral ligaments (MCL and LCL) are manipulated to balance the knee joint. ...
Article
Nearly 20% of patients who have undergone total knee arthroplasty (TKA) report persistent poor knee function. This study explores the idea that, despite similar knee joint biomechanics, the neuro-motor synergies may be different between high-functional and low-functional TKA patients. We hypothesized that (1) high-functional TKA recruit a more complex neuro-motor synergy pattern compared to low-functional TKA and (2) high-functional TKA patients demonstrate more stride-to-stride variability (flexibility) in their synergies. Gait and electromyography (EMG) data were collected during level walking for three groups of participants: (i) high-functional TKA patients (n=13); (ii) low-functional TKA patients (n=13) and (iii) non-operative controls (n=18). Synergies were extracted from EMG data using non-negative matrix factorization. Analysis of variance and Spearman correlation analyses were used to investigate between-group differences in gait and neuro-motor synergies. Results showed that synergy patterns were different among the three groups. Control subjects used 5-6 independent neural commands to execute a gait cycle. High functional TKA patients used 4-5 independent neural commands while low-functional TKA patients relied on only 2-3 independent neural commands to execute a gait cycle. Furthermore, stride-to-stride variability of muscles' response to the neural commands was reduced up to 15% in low-functional TKAs compared to the other two groups.
... GB having greater laxity than rKA is likely attributed to surgeon preference as soft tissue balancing is inherently subjective [15,22,29]. During early use of the robotic system, the GB surgeon observed the final laxity was often tighter than desired in extension and began targeting a looser knee. ...
Article
Full-text available
Purpose: The purpose of this study was to compare ligament balance and laxity profiles achieved throughout flexion in restricted kinematic alignment (rKA) and gap balancing (GB). rKA and GB both aim to improve soft tissue balance and reduce ligament releases in total knee arthroplasty (TKA). Methods: One surgeon performed 68 rKA, another performed 73 GB TKAs using the same CR implant and robotic system. rKA limited femoral valgus and tibial varus to 6°, with tibial recuts performed to achieve balance. GB limited tibial varus and femoral valgus to 2°, with femoral resections adjusted to achieve mediolateral balance throughout flexion using predictive-gap planning software. Final joint laxity was measured using a robotic ligament tensioner. Statistical analyses were performed to compare differences in mediolateral balance and joint laxity throughout flexion. Further analyses compared alignment, joint line elevation and orientation (JLO), and frequency of ligament releases and bone recuts. Results: Both techniques reported greater lateral laxity throughout flexion, with GB reporting improved mediolateral balance from 10° to 45° flexion. GB resected 1.7 mm more distal femur (p ≤ 0.001) and had greater overall laxity than rKA throughout flexion (p ≤ 0.01). rKA increased JLO by 2.5° and 3° on the femur and tibia (p ≤ 0.001). Pre-operative and post-operative coronal alignment were similar across both techniques. rKA had a higher tibial recut rate: 26.5% vs 1.4%, p < 0.001. Conclusions: rKA and GB both report lateral laxity but with different JLO and elevation. Use of a predictive-gap GB workflow resulted in greater mediolateral gap symmetry with fewer recuts. Level of evidence: III, retrospective cohort study.
... This translation is present in the native knee and is necessary for achieving deep flexion [48][49][50][51]. This consequence is supported by a recent clinical study that showed patients preferred a more lax knee after TKA [52]. ...
Chapter
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Soft tissue balance is a measure of the relative tensions in the soft tissue restraints of the knee. The soft tissues should be considered “balanced” when they are appropriately tensioned to stabilize the joint without causing stiffness, limited motion, or pain. The native knee is inherently stable and has adequate mobility to enable individuals to perform a wide range of activities without pain, stiffness, or feelings of instability. Hence, surgeons may avoid some of the common sources of dissatisfaction and indications for revision after total knee arthroplasty (TKA) including instability, stiffness, functional limitations, and residual pain by striving to restore the soft tissue balance of the native knee. Soft tissue balance is most commonly assessed based on the laxities because no clinical methods are currently available to directly measure the tension in individual soft tissue restraints and the laxities can be measured pre-, intra-, and postoperatively. When using the laxities of the native knee to guide soft tissue balancing during TKA, surgeons must remember that the native knee has negligible laxity in extension and on average becomes three times more lax in varus-valgus, internal-external rotation, and distraction at 90° of flexion. The advantage of striving to restore a patient’s native soft tissue balance after TKA is evident in the positive clinical outcomes after kinematically aligned TKA in which the surgeon strives to restore the native soft tissue balance. After kinematically aligned TKA, patients have better pain relief, have higher functional scores, achieve greater flexion, have more normal kinematics, and are three times more likely to report that their knee feels normal than patients after mechanically aligned TKA, in which surgeons do not strive to restore the native soft tissue balance.
... Han et al [26] accept asymmetry up to 3 mm for the extension gap and 5 mm for the flexion gap. Kuster et al [27] reported that 4 of mediolateral laxity is acceptable and Griffin et al [11] accepted asymmetries up to 3 mm for both gaps. ...
Article
Background: To analyze 2 methods of manual spreader gap assessment accuracy, visual vs blinded, compared with a controlled tensioner in total knee arthroplasty. Methods: Twenty-two fresh frozen cadaver knees were used to perform total knee arthroplasty by 22 surgeons. Extension and flexion gaps were measured with empirical manual force application with spreaders in 2 different manners: (1) surgeons were blinded to gap geometry formation-blind method group (BM) and (2) surgeons viewed them-viewing method group (VM). A tensioner was used to measure the corresponding ligament tension applied during spreader measurements and to measure the extension and flexion gaps with standard force of 100 and 80 N (tensioner method [TM]) in each femorotibial compartment. Results: All measurements with spreaders (VM and BM) presented extension and flexion gaps oversized and asymmetric (P < .0001), when compared with the same gaps measured with the tensioner. Approximately 63% (P = <0.001) and 77.3% (P = .161) of the VM group and 68.2% (P = .018) and 77.3% (P = .161) of the BM group demonstrated asymmetry for extension and flexion gaps up to 3 mm to the TM. Gaps measured in the VM group presented results with slightly less oversizing and asymmetries than the measurements in the BM group compared with TM, although significantly different (P < .0001). Conclusion: The assessment of extension and flexion gaps with empirical manual applied force spreaders produced oversized and asymmetric gaps compared with the use of tensioner. No visual influence was observed during the spreader applied empirical manual force compared with the blinded assessment.
... A recent report investigating patient-reported outcomes after TKA indicated that patient satisfaction levels for TKA were as high as 80% in patients [2], and risk factors for poor subjective outcomes include patient age, arthritis severity, comorbidities, pain profile, psychological status, and expectations [3][4][5][6][7][8]. Other possible causes are TKA imbalance, implant malalignment, and postoperative kinematics, such as abnormal rotational pattern and femoral condylar liftoff [9][10][11][12]. Postoperative extension-flexion gap balance is particularly known to affect the range of motion (ROM), function, and polyethylene wear [13][14][15], which may consequently result in patient dissatisfaction with TKA. ...
Article
Background: We hypothesized that postoperative anteroposterior (AP) stability of the knee correlates with patient-reported clinical outcome and knee function after total knee arthroplasty (TKA). Methods: This study enrolled 110 knees in 81 patients after TKA. AP laxity was measured with a KS Measure Arthrometer at 30°, 60°, and 90° flexion, which was confirmed with a goniometer. We assessed knee pain and function by using the Knee Society Function Score (KSS) and Knee Injury and Osteoarthritis Outcome Score (KOOS). Correlations among AP translation values and KOOS subscale scores (pain symptom, activities of daily living, and knee-related quality of life), KSS, and range of motion (ROM) were analyzed. Results: The mean follow-up period for the assessment of the KOOS was 4.4 ± 2.2 years (range, 1.1-11.5 years). Twenty-five knees had posterior-stabilized fixed-bearing TKA, and 85 knees had posterior-stabilized mobile-bearing TKA. The mean KSS functional score and mean ROM were 96.3 ± 5.7 (range, 75-100) and 121.6° ± 14.4° (range, 90°-145°), respectively. The mean AP laxity was 4.5 ± 2.2 mm, 3.6 ± 1.9 mm, and 3.0 ± 1.9 mm at 30°, 60°, and 90° knee flexion, respectively. A significant inverse association was observed between AP laxity at 60° knee flexion and KOOS pain (P = .02(∗), R(2) = 0.05), but no significant association was found between AP laxity and other KOOS subscale score, KSS, and ROM. Conclusion: We found that the AP laxity at 60° knee flexion in this study significantly correlated with patient-reported pain. The observed AP laxity can be considered as a register of normal AP translations after arthroplasty.
... Patients tend to prefer the knee with mild-to-moderate laxity. 29, 30 In patients with balanced mediolateral laxity, those with a total laxity in varus-valgus between 6°and 10°had the best Knee Society function and the Western Ontario and McMaster Universities Osteoarthritis Index scores, 28 suggesting that an optimal range might exist for an envelope of laxity. ...
Article
Knee stability is the ability for the joint to maintain an appropriate functional position throughout its range of motion. Knee instability can be defined as excessive laxity during activities of daily living. Intraoperative knee laxity can be affected by implant design, alignment of components, and soft-tissue balancing. Soft-tissue balance is a major contributor to knee instability. Mechanical balancing instruments can be classified as spacer blocks or joint-distraction devices. Conventional wisdom favors rectangular and equal flexion-extension gaps. However, knee balance is elusive even with mechanical balancing instruments. First-generation electronic balancing devices are equivalent in concept to spacer blocks instrumented with force sensors. Second-generation electronic balancing devices are equivalent in concept to mechanical distraction devices instrumented with pressure and displacement sensors. Electronic ligament balancers can be useful in documenting intraoperative knee laxity for quantifiable correlation with postoperative outcomes, thus directly relating postoperative stability to surgical balance, and may predict outcomes and knee stability.
... [14,23] Conversely, patients have been reported to prefer a TKA with mild to moderate mediolateral laxity than a truly balanced knee. [11] Edwards et al. first reported that Hospital for Special Surgery scores were greater for lax knees than those without mediolateral laxity. [3] Similar results have been reported by Liebs et al., stating that patients with a larger lateral gap in extension demonstrated significantly greater WOMAC pain scores than those that had increased medial gap. ...
Article
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Purpose: The purpose of this study was to determine if using a sensor-equipped tibial insert would reduce medial (MED) and lateral (LAT) gapping and create more equivalent compressive forces in the MED and LAT compartments. Methods: 7 orthopedic surgeons each performed bilateral TKA on complete lower extremity cadaveric specimens. Left TKA was performed first without the use of the instrumented tibial insert. With trial components placed, the patella was reduced and joint capsule closed with towel clips. Surgeons performed varus and valgus stress tests on each knee and the mm of MED and LAT gapping were recorded. Compressive forces in the MED and LAT compartment were measured at 10°, 45°, and 90° of flexion. Sensor-assisted TKA was then performed on the right knee and compressive forces and gapping were again recorded. MED, LAT, and total mediolateral (ML) gapping and MED and LAT compressive forces were compared between conventional TKA and sensor-assisted TKA with paired t-tests. Results: Sensor-assisted TKA resulted in significantly reduced MED (1.2 vs. 1.9 mm, p
... In case of very rigid soft tissue the patient often suffers from subjective limitations in range of motion with a simultaneous increase in pain intensity. Kuster et al. [18] examined a total of 22 patients to which both sides were supplied with a total knee replacement. He examined the ligamentous laxity with side-to-side difference, and found that the laxer knee joint is tolerated more than the tighter contralateral side. ...
Article
Rotational laxity and collateral ligament laxity following total knee arthroplasty with rotating platform Purpose The aim of this study was to evaluate laxity in knees with pre-operative (preop) valgus alignment compared to knees with pre-operative varus alignment after total knee arthroplasty (TKA). Methods This was a retrospective study including 81 patients, with six years follow-up, for pre-operative valgus- or varus alignment of the leg. All patients had been supplied with the same cruciate retaining (CR) TKA with rotating platform. Clinical findings were assessed by KSS, OKS and IKDC 2000 score. Rotational knee laxity was evaluated by a validated instrument (Laxitester®) with 2 Nm torque in 30° flexion. Collateral ligament laxity was tested manually in 30° flexion with a bending moment of approximately5 Nm. Biomechanical results were compared to the contralateral side. Results Thirty-one patients had a preop valgus alignment of 8.96° and 50 patients a varus leg axis of 4.99° in the mean. In the preop valgus knees rotational analysis showed an increased laxity of 10.7° compared to preop varus knees (p=0.001). There was no significant difference in medial (valgus 2.6 mm, varus 2.5 mm) and lateral (valgus 2.8 mm, varus 2.7 mm) laxity. KSS and OKS showed no significant differences in the follow-up results. In the IKDC 2000 objective score 50 % of the preop varus knees and 25.8 % of the preop valgus knees were classified as nearly normal. The difference in the IKDC objective was highly significant (p<0.001). Conclusion Preop valgus knees show a significantly increased rotational laxity but no increased collateral ligament laxity compared to pre-operative varus knees six years after TKA with rotating platform. There is a significant difference in IKDC objective. Keywords Knee laxity . Total knee replacement . Rotational laxity knee . Rotating platform TKA . Cruciate retaining TKA . Laxitester
... The other parameter that could possibly affect the function is the total contact force, which is one measure of how loose or tight the joint was. In a study of bilateral total knee arthroplasty, it was found that patients preferred the looser knee over the tighter one, although statistical significance was not achieved [18]. At surgery, the tightness is not controlled directly, but a major factor is the thickness of the tibial component which is selected based on reaching full extension [19]. ...
Article
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Background: The purpose of the study was to investigate the accuracy of balancing which could be achieved at total knee surgery and its relation to functional outcomes. Methods: During surgery, the forces on the medial and lateral plateaus were measured at 10-15 degrees flexion in 101 patients, using an instrumented tibial trial, with equal forces being targeted. Of the initial 101 cases, 71 cases completed all follow-up visits to 1 year. At each follow-up visit, the function was measured using the Knee Society Scoring System, and varus and valgus laxity angles were measured. Results: The mean medial/(medial + lateral) compartmental force ratio was 0.52, with a standard deviation of 0.09. The total contact force was 217 Newtons, with a standard deviation of 72 Newtons. No correlations were found between the functional scores and the compartmental force ratio or total contact force. However, the mean varus and valgus laxity angles, 2.8 and 2.3 degrees, respectively, were very close to the angles of normal intact knees. Conclusions: The likely reason for the lack of correlation of function was that the large majority of the balancing ratios were within the range 0.4-0.6 but with a wide spread of functional scores typical of total knee study groups. However, the normal varus and valgus angles achieved at follow-up indicated that equal balancing in early flexion was a reasonable surgical target. Using instrumented tibial trials enabled accurate and consistent balancing values to be achieved, as well as normal varus and valgus laxity angles, which may be important in obtaining optimal outcomes.
... Balancing the collateral ligaments is therefore considered as an important factor affecting the clinical success after total knee arthroplasty (TKA) [1]. Leaving the knee too loose may theoretically lead to tibio-femoral instability, whereas excessive tightness may cause stiffness [2][3][4][5][6]. Elevation of the knee joint line during TKA could in theory disturb this balance and should therefore probably be avoided. ...
Article
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Correct restoration of the joint line is generally considered as crucial when performing total knee arthroplasty (TKA). During revision knee arthroplasty however, elevation of the joint line occurs frequently. The general belief is that this negatively affects the clinical outcome, but the reasons are still not well understood. In this cadaveric in vitro study the biomechanical consequences of joint line elevation were investigated using a previously validated cadaver model simulating active deep knee squats and passive flexion-extension cycles. Knee specimens were sequentially tested after total knee arthroplasty with joint line restoration and after 4 mm joint line elevation. The tibia rotated internally with increasing knee flexion during both passive and squatting motion (range: 17° and 7° respectively). Joint line elevation of 4 mm did not make a statistically significant difference. During passive motion, the tibia tended to become slightly more adducted with increasing knee flexion (range: 2°), while it went into slighlty less adduction during squatting (range: -2°). Neither of both trends was influenced by joint line elevation. Also anteroposterior translation of the femoral condyle centres was not affected by joint line elevation, although there was a tendency for a small posterior shift (of about 3 mm) during squatting after joint line elevation. In terms of kinetics, ligaments lengths and length changes, tibiofemoral contact pressures and quadriceps forces all showed the same patterns before and joint line elevation. No statistically significant changes could be detected. Our study suggests that joint line elevation by 4 mm in revision total knee arthroplasty does not cause significant kinematic and kinetic differences during passive flexion/extension movement and squatting in the tibio-femoral joint, nor does it affect the elongation patterns of collateral ligaments. Therefore, clinical problems after joint line elevation are probably situated in the patello-femoral joint or caused by joint line elevation of more than 4 mm.
... In particular, the question of clinically relevant thresholds for anterior-posterior translation or medial-lateral joint opening is yet unanswered. The establishment of cut-off values might be difficult as there is an individual and physiological range of laxity among patients after TKA [9,18]. In addition, it is the general laxity of joints in each patient, which appears to make patients more or less prone for developing an instability with a looser or tighter joint play. ...
Article
PurposeThe primary aim of this study was to investigate the potential benefit of stress radiographs for diagnosis of unstable total knee arthroplasty (TKA) and to identify clinically relevant cut-off values to differentiate between unstable and stable TKAs.Methods Data of 40 patients with 49 cruciate retaining (CR) TKA who underwent stress radiographs as part of the diagnostic algorithm in a painful knee clinic were prospectively collected. Anterior and posterior stress radiographs were done in 90° and 15° flexion, varus-valgus stress radiographs in 0° and 30° knee flexion. Knee laxity was measured in mm and degrees by two independent observers using standardized landmarks. Intra- and inter-observer single measure intraclass correlations were between 0.92 to 1 and 0.89 to 1, respectively. For evaluation and investigation of the potential cut-off values, two groups of patients with and without revision surgery due to instability were compared. Radiographic measures of standardized z values according to the group without revision due to instability were used to calculate average and maximum laxity z-scores.ResultsKnees undergoing revision TKA due to instability showed significantly (p < 0.001) lower (KSS) pain/function scores (94 ± 6.3, range 80–100; control group: 112 ± 19.2, range 80–148) and total KSS scores when compared to the control group. The laxity values of patients with instability were significantly higher in terms of mean values (p < 0.01) when compared to the control group. The maximum laxity z-score showed the strongest difference between the groups (R2 = 0.26, p < 0.001). The following cut-off values indicating need of revision due to instability were established: in 90° (15°) flexion—anterior translation 5.2 mm (22.4 mm), posterior translation 16.6 mm (13.2 mm); varus stress in 0° (20°–30°) flexion—inlay gap 5.2 mm (6.1 mm) or joint angle 6.1° (6.8°); valgus stress in 0° (20°–30°) flexion—inlay gap 4.6 mm (5.7 mm) or joint angle 5.2° (7.1°).Conclusion Standardized stress radiographs are helpful tools for diagnosis of instability after TKA. The established cut-off values help to guide decision making in this challenging group of patients. However, laxity values should not be considered as the only criteria for diagnosis of unstable TKA.Level of evidenceIV.
... Numerous investigations also suggested a lax knee joint can improve the range of flexion [3,10]. In a clinical study with bilateral TKAs, patients preferred the laxer knee and felt more comfortable [28]. In addition, weightbearing, high-flexion activities such as kneeling and squatting necessitate more than 20° of internal tibial rotation and the joint stiffness will increase with muscle contractions. ...
Article
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Purpose: The primary intent of total knee arthroplasty is the restoration of normal knee kinematics, with ligamentous constraint being a key influential factor. Displacement of the joint line may lead to alterations in ligament attachment sites relative to knee flexion axis and variance of ligamentous constraints on tibiofemoral movement. This study aimed to investigate collaterals strains and tibiofemoral kinematics with different joint line levels. Methods: A previously validated knee model was employed to analyse the change in length of the collateral ligaments and tibiofemoral motion during knee flexion. The models shifted the joint line by 3 and 5 mm both proximally and distally from the anatomical level. The data were captured from full extension to flexion 135°. Results: The elevated joint line revealed a relative increase in distance between ligament attachments for both collateral ligaments in comparison with the anatomical model. Also, tibiofemoral movement decreased with an elevation in the joint line. Conversely, lowering the joint line led to a significant decrease in distance between ligament attachments, but greater tibiofemoral motion. Conclusion: Elevation of the joint line would strengthen the capacity of collateral ligaments for knee motion constraint, whereas a distally shifted joint line might have the advantage of improving tibiofemoral movement by slackening the collaterals. It implies that surgeons can appropriately change the joint line position in accordance with patient's requirement or collateral tensions. A lowered joint line level may improve knee kinematics, whereas joint line elevation could be useful to maintain knee stability. LEVEL OF EVIDENCE: V.
... A few recent reports highlighted that better reproduction of the normal anatomy of the knee, with mild to moderate mediolateral laxity during a varus stress test, is linked to a better clinical score. 40 Edwards et al. 41 The current study showed that the intraoperative use of load sensors improved the use of a medial pivot implant (characterized by a lower level of constraint when compared to PS), intraoperatively reproducing a normal kinematic without increasing the risk of postoperative patient-detected instability. The current results differ from those of previous studies. ...
Article
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Methods: Two cohorts of 50 patients each were preoperatively matched to receive the same TKA, having a J-curve femoral design with an adapted "medially congruent" polyethylene insert; the second cohort (group B) underwent the intraoperative sensor-check. Intraoperative sensor data were recorded as tibiofemoral load at 10°, 45°, and 90°. We considered stable knees those with a pressure <50 lbs on the medial compartment, <35 lbs on the lateral, and a mediolateral inter-compartmental difference <15 lbs. Clinical outcomes were evaluated according to the Oxford Knee Score (OKS) and Knee Society Score (KSS). Results: All patients (group A: no sensor; group B: sensor) were available at 2-year minimum follow-up (FU; min. 24 months, max. 34 months); no preoperative statistical differences existed between groups in the average range of motion (ROM), OKS, KSS, and body mass index. There were no statistical differences at final FU between groups in the average OKS (group A: 41.1; group B: 41.5), in the average KSS (group A: 165.7; group B: 166.3), or in final ROM (group A: 123°; group B: 124°). One patient in each group required a manipulation under anesthesia. In the sensor group, an accessory soft tissue release/bone recut was necessary after sensor testing with trial components in 24% to obtain the desired loads; in the same group, the level of constraint in the final components was increased to posterior-stabilized in 12% because of an inter-compartmental difference >40 lbs. Surgical time was 8 min longer in the sensor group. Conclusion: The use of this sensing technology did not improve the clinical outcome but supported multiple intraoperative decisions aimed to better reproduce the medial pivot kinematic of the normal knee.
... Patients in this study showed good clinical results despite of more than 5 mm of joint opening and this corresponds with previous reports indicating that TKA with a lax ligament showed better results than tight knees in flexion [7,18]. ...
Article
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Purpose: Medial collateral ligament (MCL) release is one of the essential steps toward the achievement of ligament balancing during the total knee arthroplasty (TKA) in patients with varus deformity. When the varus deformity is severe, complete release of the MCL until balanced is often required. However, it is believed that complete MCL release may lead to catastrophic laxity. The purpose of this prospective study is to compare the medial joint gap opening in postoperative valgus stress radiograph in patients with complete MCL release against patients with partial release. Methods: Out of 209 primary TKAs performed for degenerative osteoarthritis, complete MCL release was required in 33 cases (group I) by sub-periosteal detachment at proximal tibia using periosteal elevator. For the remaining 176 knees (group II), partial release of MCL was done. At postoperative 6 months and 1 year, both groups were evaluated for comparing the joint gap on valgus stress radiographs using modified Telos device in 0°, 45°, and 90° of flexion. Additional parameters which were analyzed included preoperative varus and valgus stress radiographs in full extension and pre- and postoperative mechanical alignment in each group. The knee range of motion (ROM) and clinical scores were evaluated at 1-year follow-up. Results: The mean values of the joint opening on the postoperative valgus stress test with the knee joint extended, and in the 45° and 90° flexed states at 6 months and at 1 year postoperatively in group I were not statistically significantly different from those of group II. The clinical scores also did not show a statistically significant difference between two groups. There was a statistically significant difference in ROM between two groups, pre- and postoperatively and the difference was 5°, respectively. Conclusion: This study suggests that complete MCL release for ligament balancing is a safe procedure and does not lead to postoperative laxity.
... When the thickness of the insert is initially small, it will not significantly affect the rectangular shape of the joint gap or the balance of surrounding soft tissue due to its small distraction force on the joint gap. However, using too thin of an insert may lead to joint laxity and poor stability after the operation, which is associated with patient dissatisfaction and the risk of implant failure in the mid-to long-term (19,23,24). In contrast, tighter inserts can improve joint stability (25,26) but can cause pain, discomfort, and functional deficits (23), including reduced ROM, polyethylene wear, and prosthesis loosening (27,28). ...
Article
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Background: The normal femorotibial pressure and its variation under different gap values remain unknown. Thus, for the purpose of improving soft-tissue balancing in total knee arthroplasty (TKA), a load-sensor device was used to measure femorotibial pressures. More specifically, the aim of this study was to analyze the trend in pressure changes. Methods: Twenty TKAs were first balanced by conventional techniques, and then femorotibial pressure was measured using the sensor. After this, the difference in pressure among different joint gaps was calculated to analyze the trend. A repeated measure of analysis of variance and a Tukey's honestly significant difference (HSD) test were used to analyze the data. Results: The medial gap pressure was significantly increased at extension and flexion as the thickness of the sensor increased in most patients, while the lateral gap pressure changed without a specific trend. The average medial gap pressure was significantly larger than the average lateral gap pressure at both the full extension and 90° flexion positions. The average extension gap pressure was larger than the average flexion gap pressure at both the medial and lateral gaps. Conclusions: The tension of the soft tissue around the knee joint changes with the joint gap. The tension at the medial side is higher than that on the lateral side, and that of the extension position is higher than that of the flexion position. The use of the pressure sensor insert has a better auxiliary effect on the operation using the gap-balancing technique.
... On the other hand, a tight knee might impair ROM and can also cause pain. Therefore, moderate laxity should be pursued to obtain optimal functional results [9,25]. Important factors that influence sagittal balance after PCL retaining TKA include the posterior tibial slope, a functional posterior cruciate ligament and the geometry of the prosthesis [7]. ...
Article
Background: The cruciate retaining lipped (CR-lipped) bearing is designed to provide more anterior-posterior (AP) stability and could be employed to resolve excessive intraoperative laxity during the cruciate retaining TKA (CR-TKA). The aim of the study was to determine whether the CR-lipped bearing in CR-TKAs with a perioperative excessive laxity allows equivalent functional results as compared to the standard CR articulation. Methods: A cohort of 111 TKAs with CR-lipped bearings was matched to a cohort of con- ventional CR bearings regarding age and sex. The CR-lipped bearing was used in patients with excessive knee AP laxity and the regular CR bearing was used in patients without excessive AP laxity during TKA. Various PROMs (WOMAC, KSS, SF-36) were assessed pre- operatively and at 5-years postoperative in combination with revision rate and Range of Motion (ROM). Results: PROMs did not differ significantly between both groups 5-years postoperatively. Mean ROM (flexion) 5-years postoperatively was not significantly different. The implant survivorship was 100% for both cohorts with revision for any reason as end point. Conclusion: Based on these results, the CR-lipped bearing is a safe and effective solution for mild interoperatively assessed PCL laxity during CR-TKA without loss of function or decreased survivorship at 5 years. Peroperative conversion to a PS-TKA in order to obtain satisfactory functional scores might therefore not be necessary when mild PCL laxity is observed during surgery. Further research should focus on verifying this approach and longer follow-up is needed to generate data on long term survivorship. Level of evidence: Level IV therapeutic, retrospective, cohort study.
... From the authors' perspective, this could be a reason for the lower clinical results. Previous clinical studies also suggested that TKA designs with symmetric inlays on medial and lateral compartment reported lower postoperative outcomes in the presence of an over-constrained medial compartment [15,22]. ...
Article
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Purpose To investigate if postoperative clinical outcomes correlate with specific kinematic patterns after total knee arthroplasty (TKA) surgery. The hypothesis was that the group of patients with higher clinical outcomes would have shown postoperative medial pivot kinematics, while the group of patients with lower clinical outcomes would have not. Methods 52 patients undergoing TKA surgery were prospectively evaluated at least a year of follow-up (13.5 ± 6.8 months) through clinical and functional Knee Society Score (KSS), and kinematically through dynamic radiostereometric analysis (RSA) during a sit-to-stand motor task. Patients received posterior-stabilized TKA design. Based on the result of the KSS, patients were divided into two groups: “KSS > 70 group”, patients with a good-to-excellent score (93.1 ± 6.8 points, n = 44); “KSS < 70 group”, patients with a fair-to-poor score (53.3 ± 18.3 points, n = 8). The anteroposterior (AP) low point (lowest femorotibial contact points) translation of medial and lateral femoral compartments was compared through Student’s t test ( p < 0.05). Results Low point AP translation of the medial compartment was significantly lower ( p < 0.05) than the lateral one in both the KSS > 70 (6.1 mm ± 4.4 mm vs 10.7 mm ± 4.6 mm) and the KSS < 70 groups (2.7 mm ± 3.5 mm vs 11.0 mm ± 5.6 mm). Furthermore, the AP translation of the lateral femoral compartment was not significantly different ( p > 0.05) between the two groups, while the AP translation of the medial femoral compartment was significantly higher for the KSS > 70 group ( p = 0.0442). Conclusion In the group of patients with a postoperative KSS < 70, the medial compartment translation was almost one-fourth of the lateral one. Surgeons should be aware that an over-constrained kinematic of the medial compartment might lead to lower clinical outcomes. Level of evidence II.
... Interestingly, the varus/valgus laxity testing in our study demonstrated similar symmetrical behavior of the medial and lateral balance in both extension and flexion post-operatively, which is a specific target of the PIPB technique. This finding also extends to the comparable strains in the MCL and LCL, which has been reported to be an important factor in terms of patient satisfaction [1,2,5,15,41,[50][51][52][53][54]. ...
Article
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IntroductionPoor soft tissue balance in total knee arthroplasty (TKA) often results in patient dissatisfaction and reduced joint longevity. Patella-in-place balancing (PIPB) is a novel technique which aims to restore native collateral ligament behavior without collateral ligament release, while restoring post-operative patellar position. This study aimed to assess the effectiveness of this novel technique through a detailed ex vivo biomechanical analysis by comparing post-TKA tibiofemoral kinematics and collateral ligament behavior to the native condition. Materials and methodsEight fresh-frozen cadaveric legs (89.2 ± 6 years) were tested on a validated dynamic knee simulator, following computed tomography imaging. Specimens were subjected to passive flexion (10–120°), squatting (35–100°), and varus/valgus laxity testing (10 Nm at 0°, 30°, 60°, 90° flexion). An optical motion capture system recorded markers affixed rigidly to the femur, tibia, and patella, while digital extensometers longitudinally affixed to the superficial medial collateral ligament (MCL) and lateral collateral ligament (LCL) collected synchronized strain data. Following native testing, a Stryker Triathlon CR TKA (Stryker, MI, USA) was performed on each specimen and the identical testing protocol was repeated. Statistical analyses were performed using a linear mixed model for functional motor tasks, while Wilcoxon signed-rank test was used for laxity tests (p < 0.05). ResultsPostoperative laxity was lower than the native condition at all flexion angles while post-operative ligament strain was lowered only for MCL at 30° (p = 0.017) and 60° (p = 0.011). Postoperative femoral rollback patterns were comparable to the native condition in passive flexion but demonstrated a more pronounced medial pivot during squatting.Conclusions Balancing a TKA with the PIPB technique resulted in reduced joint laxity, while restoring collateral ligament strains. The technique also seemed to restore kinematics and strains, especially in passive flexion.
Article
Purpose To evaluate the difference in post-operative knee awareness between knees in patients undergoing bilateral simultaneous total knee arthroplasty (TKA) and to assess factors predicting high or low knee awareness. Methods This study was conducted on 99 bilateral simultaneous TKAs performed at our institution from 2008 to 2012. All patients received one set of questionnaires [Forgotten Joint Score (FJS) and Oxford Knee Score (OKS)] for each knee. Based on the FJS, the patients’ knees were divided into two groups: “best” and “worst” knees. The median of the absolute difference in FJS and OKS within each patient was calculated. Multivariate linear regression was performed to identify factors affecting FJS. Results The difference between knees was 1 point (CI 0–5) for the FJS and 1 point (CI 0–2) for the OKS. The FJS for females increased (decreasing awareness) with increasing age. Males had the highest FJS (lowest awareness) at the age of 67. An increase in the FJS (lower knee awareness) of 12.0 points was found for Kellgren–Lawrence (K–L) grades 3 + 4 compared with K–L grades 1 + 2. A preoperative anatomical alignment of 3° valgus resulted in the lowest FJS (highest knee awareness) with decreasing knee awareness for decreasing tibio-femoral angles. Post-operative alignment did not significantly affect FJS. Conclusion Knee awareness did not differ significantly between the “best” and the “worst” knee. Bilateral simultaneous TKA can be performed without compromising the result in one of the knees. Knee awareness after primary TKA was influenced by age, gender, preoperative knee alignment, and severity of OA. Level of evidence III.
Article
The postoperative flexion angle reportedly shows a positive correlation with the preoperative flexion angle, but in some cases, the postoperative flexion angle decreases in patients with a large preoperative flexion angle. The purpose of this study was to investigate factors affecting the range of motion after total knee arthroplasty (TKA) in patients with a large preoperative flexion angle. The study evaluated 120 knees with more than 120 degrees of preoperative flexion angle that underwent NexGen LPS-Flex mobile bearing. The groups with and without a reduction in the postoperative flexion angle were compared. Also, a logistic regression analysis was performed, where the presence or absence of a reduction in the postoperative flexion angle was the dependent variable and age, sex, body mass index (BMI), preoperative femorotibial angle (FTA), γ angle, δ angle, pre/postoperative change amount in posterior condylar offset (PCO), pre/postoperative change amount in joint line, and pre/postoperative change amount in patellar thickness were independent variables. Those with preoperative FTA of 186° or larger did not have a reduction in the postoperative flexion angle, compared with the angle of 185° or smaller. Those with δ angle of 83° or smaller also did not have a reduction in the postoperative flexion angle, compared with the angle of 84° or larger. Our results showed that preoperative FTA and δ angle had an impact on a reduction in the postoperative flexion angle. The installation angle of the tibial component in the sagittal plane is important.
Article
We investigated the relations between flexion balances and functional outcomes after total knee arthroplasty (TKA). Sixty-one knees that underwent a TKA were included in this study. Clinical assessments were performed and flexion balances of the knee were assessed on varus and valgus stress radiographs at 90° of knee flexion. Total laxity was defined as the sum of medial and lateral laxities. Knees were divided into balanced (≤3°, n = 51) and unbalanced (>3°, n = 10) groups based on the only difference of mediolateral laxity regardless of total laxity. And the balanced group was divided into Grade I (<6°), Grade II (≥6° but ≤10°) or Grade III (>10°) groups based on the amount of total laxity. Although no statistically significant differences were observed between the balanced and unbalanced groups in terms of range of motion (ROM) and KS pain scores, the balanced group achieved better results in terms of KS function and WOMAC scores than the unbalanced group. Total laxity was significantly less in the balanced group. In addition, Grade II knees in the balanced group had significantly better KS pain and function scores, and WOMAC scores than Grade Ior Grade III knees. These results suggest that total knees with good balanced flexion stability can provide good functional outcomes after TKA.
Article
Purpose: The aim of the present study was to clarify whether varus-valgus laxities under static stress in extension, femoral condylar lift-off during walking, and patient-reported outcomes after total knee arthroplasty (TKA) were correlated with each other. Methods: Ninety-four knees, which had undergone posterior-stabilized TKA, were analysed. The varus-valgus laxity during knee extension was measured using a stress radiograph. New Knee Society Score (KSS) questionnaires were mailed to all patients. Correlations between the values of stress radiographs and KSS were analysed. Additionally, continuous radiological images were taken of 15 patients while each walked on a treadmill to determine condylar lift-off from the tibial tray using a 3D-to-2D image-to-model registration technique. Correlations between the amount of lift-off and either the stress radiograph or the KSS were also analyzed. Results: The mean angle measured was 5.9 ± 2.7° with varus stress and 5.0 ± 1.6° with valgus stress. The difference between them was 0.9 ± 2.8°. Varus-valgus laxities, or the differences between them, did not show any statistically significant correlation with either component of the KSS (p > 0.05). The average amount of femoral condylar lift-off during walking was 1.4 ± 0.8 mm (medial side) and 1.3 ± 0.6 mm (lateral side). The amount of lift-off did not correlate with either varus-valgus laxities or the KSS (p > 0.05). Conclusions: No correlations were found among varus-valgus laxities under static stress in extension, femoral condylar lift-off during walking, or patient-reported outcomes after well-aligned TKA. This study suggests that small variations in coronal laxities do not influence lift-off during walking and the patient-reported outcomes. Level of evidence: IV.
Article
Purpose To examine the effect of implantation of the femoral component of a total knee arthroplasty (TKA) system in 0°, 3°, and 6° of flexion on the sagittal plane morphology of the femoral load-bearing surfaces. It was hypothesized that increasing the flexion angle would result in undersizing of the anterior surface without changing the flexion gap. Methods Computer simulation of a TKA using three-dimensional models of 10 healthy knees, matched to three different sized femoral components. Size discrepancy in the sagittal plane anterior, distal, and posterior joint surfaces between the native and prosthetic knees was calculated at 0°, 3°, and 6° of flexion. Results The required component size varied with the angle of implantation: 0°, size 3/size 4 (N = 7/3), 3°, size 3 (N = 10); and 6°, size 2/size 3 (N = 4/6). Component undersizing ranged between 4.4–6.3 mm at the anterior lateral surface, with a significant difference between 0° and 6° (p < 0.05), and 1.2–3.5 mm at the anterior medial surface. Component oversizing of the distal surface of the lateral condyle (2.9 mm) and undersizing of the medial surface of the posterior condyle (1.6–2.3 mm) were comparable at all three flexion angles of component implantation. Conclusions Increasing the flexion angle of implantation increased the incidence of using a smaller size of femoral component without significant interference with the flexion gap. However, the effect of a smaller femoral component on undersizing of the anterior surface of the condyle and the impact on the extensor mechanism need to be considered.
Article
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Total knee arthroplasty (TKA) is the gold standard of treatment for advanced osteoarthritis of the knee. The technical methods of cartilage regeneration procedures are now well-developed. Indications for this procedure are being expanded to the treatment of osteoarthritis. We compared data from 42 patients who underwent TKA and from 52 patients who underwent MCIC (autologous bone marrow mesenchymal-cell-induced-chondrogenesis). All patients were over 50 years of age and showed grade IV of the Kellgren-Lawrence classification. The TKA patients were older and predominantly female, compared to the MCIC patients. There was no difference between the two groups regarding the patient satisfaction. Clinical evaluation of the two groups showed significant mean improvement in the tKSS-A (pain) and tKSS-B (function) scores throughout the postoperative follow-up period. The monetary cost of TKA was relatively higher than that of MCIC. Therefore, considering the patient age and quality of life, MCIC is a potential treatment option for osteoarthritis as it thus delays the disease progression.
Article
Background: The purpose of this study was to determine if postoperative patient satisfaction, subjective outcomes, and functional force testing differed between those with symmetric or asymmetric intraoperative mediolateral (ML) compressive forces. We hypothesized that the threshold would be similar to the previously reported valued of 15 lbf and that a significantly greater proportion of those with more symmetrical medial and lateral compressive forces would be satisfied with their total knee arthroplasty. Methods: A commercially available instrumented trial tibial liner was used to measure ML compressive force differences with the knee at 0°, 20°, and 90°. Patient satisfaction and Knee Society Scores were compared between patients with ML asymmetries above and below the calculated optimal threshold. Results: Surprisingly, lower ML asymmetries in extension were associated with a greater risk of being dissatisfied. Of the 50 total knee arthroplasties, 6 of 23 (26%) with ML force asymmetries <10 lbf were dissatisfied compared with 0 of 27 with ML asymmetries >10 lbf (P = .01). Greater asymmetry was associated with significantly greater gains in EQ-5D scores (P = .05) and pain scores (P = .03) and greater pain relief (P = .006) and reduced impact forces when navigating stairs (P = .05). Conclusion: Contrary to our hypotheses, the results of this study support the concept that recreating greater forces in the medial compartment much like that of the native knee may yield improved patient-reported outcomes and increased patient satisfaction. The current results further suggest that recreating greater medial compartment forces may have the greatest affect on more demanding activities such as navigating stairs.
Chapter
Das Kapitel beinhaltet die wichtigsten Prinzipien der Operationstechnik eines Oberflächenersatzes am Kniegelenk. Verschiedene Optionen der aktuellen Systeme werden mit ihren Vor- und Nachteilen beschrieben. Hierzu zählen intra- und extramedulläre Ausrichtung, Ausrichtung der tibialen und femoralen Komponenten in Bezug auf Varus/Valgus, Flexion/Slope und Rotation, jeweils mit den gebräuchlichsten anatomischen Landmarken. Die konkurrierenden Operationssequenzen „tibia first“ und „femur first“ werden miteinander verglichen. Darüber hinaus werden die patientenspezifischen Instrumentarien und Implantate, die verschiedenen Kopplungsgrade in Abhängigkeit der vorhandenen Bänder, die operativen Techniken des Patellarückflächenersatzes und das Balancing des Patellofemoralgelenks beschrieben. Abschließend werden die Verankerung (zementiert und zementfrei) und das sog. „ligament balancing“ dargestellt.
Article
PurposeFlexion instability following total knee arthroplasty (TKA) is a common indication of early revision. The association between the objective anteroposterior (AP) laxity direction in mid-range flexion and the subjective healing of instability remains unclear; thus, this study aimed to clarify this association. Methods In this study, 110 knees (74 females, 92 knees; 16 males, 18 knees) with medial pivot implants were examined with a median age of 79 (range 60–92) years for a median follow-up duration of 22 (range 6–125) months. AP laxity was measured using a KT-1000 arthrometer. Self-reported knee instability score was used for the subjective healing of instability. ResultsEighty-seven knees did not feel unstable (Group 0), whereas 23 knees felt unstable (Group 1). There was a significant difference in AP displacement [Group 0: median 6 mm; range 2–15 mm and Group 1: median 8 mm; range 4–14; p < 0.0001]. The threshold value of 7 mm was determined using the area under receiver operating characteristic curve of 0.79 [95% confidence interval (CI) 0.69–0.88, p < 0.0001]. In multivariate analysis, AP displacement of ≥7 mm was an independent risk factor for feelings of instability (odds ratio 7.695; 95% CI 2.306–25.674; p = 0.001). ConclusionsAP laxity of ≥7 mm represents a known cause of feelings of instability. By controlling AP laxity in TKAs, without stiffness in the knee, it is possible to prevent feelings of instability. The clinical relevance is that AP laxity of <7 mm is one of the target areas in TKA. Level of evidenceIV.
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Instability after total knee replacement (TKR) is the third common cause for revision surgery. Asymmetric instability such as varus, valgus or posterior instability should be distinguished from symmetric instability, which includes isolated or combined flexion and extension instability. Isolated instability might be treated in a biological way by reconstruction of the unstable soft tissue using the semitendinosus autograft. Soft tissue release of the contralateral side will allow rebalancing of the knee. The release should be followed according to a strict algorithm in order to avoid overcorrection. Rebalancing of both the flexion and extension gap needs to be performed. Rebalancing of the knee will require a higher inlay in order to fill the enlarged flexion and extension gap. The epicondylar sliding technique might be used to readjust the femoral insertion site. Often component exchange is required, and a more constraint design is used such as the total stabilized or hinged design in which the function of the collateral ligaments is less important.
Article
Introduction: Few studies have evaluated the concomitant effect of both total knee arthroplasty (TKA) limb alignment and ligament laxity. Therefore, the primary aim of this study is to evaluate the impact of lower extremity alignment on the short-term outcome (one year) following TKA, including pain relief, function, and patient satisfaction. The secondary aim of the study is to evaluate the impact of ligament laxity and balance on early outcomes following TKA. Materials and methods: A prospective evaluation of mechanical alignment and ligament tension was performed for 110 consecutive TKAs using an identical surgical technique. Patients were evaluated with knee society score, visual analog pain score, and satisfaction one year following TKA. Linear regression analysis was then performed to determine the effect of lower extremity alignment and ligament laxity. Results: There was no significant relationship between lower extremity alignment and outcome measures. A significant relationship was identified between medial collateral laxity in full extension and knee society scores for function, but not for pain. There was also a significant relationship identified between lateral knee laxity at 90 degrees of flexion and knee society score and pain at one-year follow up. Conclusion: Our results demonstrated no correlation between mechanical alignment restoration and pain or function. However, more interestingly, this study found patients with medial laxity in extension and lateral laxity in knee flexion, similar to normal physiologic knee laxity, to have less pain and greater function and satisfaction at one-year short-term follow up.
Article
Purpose Both coronal and sagittal laxity of well-functioning knees after total knee arthroplasty (TKA) was examined, and the correlations between the joint laxity and the clinical outcomes were analyzed to clarify the adequate joint laxity for the prosthesis, and the relationship between the laxity and the outcomes. Methods Forty well-functioning TKA knees with a high-flexion posterior-stabilized (PS) prosthesis were studied. All patients were diagnosed as having osteoarthritis with varus deformity and were followed up for 2 years or more. The coronal and sagittal laxity was assessed at extension and flexion, and the correlations between the joint laxity and the clinical outcomes were evaluated. Results The varus and valgus laxity averaged 5.6 ± 1.8° and 3.6 ± 1.2° at 10° knee flexion, and 7.4 ± 5.1° and 3.6 ± 2.7° at 80° knee flexion, respectively, and the AP laxity at 30° and 75° knee flexion averaged 8.7 ± 3.6 mm and 6.6 ± 2.3 mm, respectively. Knee flexion angle correlated with the joint laxity, while the other outcomes including patient-reported pain and instability were adversely affected by the greater laxity. Conclusions This study exhibited the importance of consistent medial laxity both at extension and flexion, which averaged 3.6°. Care should be taken to maintain the medial stability and to obtain adequate laxity both at extension and flexion during surgery. A few degrees of medial tightness can be allowed to achieve excellent clinical results after TKA for preoperative varus knees. Level of evidence Therapeutic study, Level III.
Article
Background: Stress radiography is used in the valuation of soft tissue laxity following total knee arthroplasty (TKA). However, reliability and agreement is largely unknown. Methods: In this prospective reliability study, we included 15 participants with prior TKA. Standardized coronal stress radiographs were obtained in both extension and flexion and with both varus and valgus stress. All radiographs were repeated (test-retest). In extension the Telos stress device was used, and flexion radiographs were obtained using the epicondylar-view. Three independent raters measured angulation between femoral and tibial component from all radiographs. Reliability was assessed by intra-class correlation coefficient (ICC) and agreement visualized with Bland-Altman plots and by mean difference and limits of agreement (LOA). Results: Stress radiography in extension showed excellent reliability with ICC = 0.96 (0.95-0.98) and LOA of ±1.2°. Stress radiography at 80-90° of flexion showed good to excellent reliability when measuring medial laxity with ICC = 0.94 (0.89-0.97) and LOA of ±1.7°; however, when measuring lateral laxity the reliability was only moderate to good with ICC = 0.70 (0.51-0.84) and LOA of ±6.3°. Conclusion: Stress radiography is clinically applicable and the methods described in this study provide excellent reliability for measurement of laxity in extension. The reliability of measurements in flexion is good to excellent when measuring medial laxity but only moderate to good when measuring lateral laxity.
Article
Background: The aim of this retrospective study was to identify the preoperative patient-related factors affecting the soft tissue balancing in cruciate-retaining total knee arthroplasty. This is an important clinical issue, as the acquisition of adequate soft tissue balancing is essential for successful outcomes. Methods: The study group included 59 knees treated for medial compartment osteoarthritis. The extension gap was measured using the newly electric tensor that enables continuous quantification of a distraction force ranging from 0 to 40 lbf. We performed regression analyses to identify the relationship between preoperative factors and the extension gap. Results: Patient height, weight, and percent mechanical axis showed univariate correlation with the extension gap of either 30 lbf or 40 lbf. In the multivariate regression analysis without encountering multicollinearity, percent mechanical axis was inversely associated with the extension gap (t-value = -2.31, p = 0.02 for 30 lbf; and t-value = -2.39; p = 0.02 for 40lbf) as a significant independent factor. Conclusions: We revealed the significant influence of several factors on the absolute value of the extension gap. Particularly, the severity of preoperative coronal alignment was a statistically independent explanatory variable, and the extension gap was overvalued in knees with severe varus deformity. This influence should be considered when comparing different individual cases longitudinally. Our feasible strategies could lead to a better understanding about the soft tissue balancing in total knee arthroplasty.
Article
Aims To compare patients undergoing total knee arthroplasty (TKA) with ≤ 80° range of movement (ROM) operated with a 2 mm increase in the flexion gap with matched non-stiff patients with at least 100° of preoperative ROM and balanced flexion and extension gaps. Methods In a retrospective cohort study, 98 TKAs (91 patients) with a preoperative ROM of ≤ 80° were examined. Mean follow-up time was 53 months (24 to 112). All TKAs in stiff knees were performed with a 2 mm increased flexion gap. Data were compared to a matched control group of 98 TKAs (86 patients) with a mean follow-up of 43 months (24 to 89). Knees in the control group had a preoperative ROM of at least 100° and balanced flexion and extension gaps. In all stiff and non-stiff knees posterior stabilized (PS) TKAs with patellar resurfacing in combination with adequate soft tissue balancing were used. Results Overall mean ROM in stiff knees increased preoperatively from 67° (0° to 80°) to 114° postoperatively (65° to 135°) (p < 0.001). Mean knee flexion improved from 82° (0° to 110°) to 115° (65° to 135°) and mean flexion contracture decreased from 14° (0° to 50°) to 1° (0° to 10°) (p < 0.001). The mean Knee Society Score (KSS) improved from 34 (0 to 71) to 88 (38 to 100) (p < 0.001) and the KSS Functional Score from 43 (0 to 70) to 86 (0 to 100). Seven knees (7%) required manipulations under anaesthesia (MUA) and none of the knees had flexion instability. The mean overall ROM in the control group improved from 117° (100° to 140°) to 123° (100° to 130°) (p < 0.001). Mean knee flexion improved from 119° (100° to 140°) to 123° (100° to 130°) (p < 0.001) and mean flexion contracture decreased from 2° (0° to 15°) to 0° (0° to 5°) (p < 0.001). None of the knees in the control group had flexion instability or required MUA. The mean KSS Knee Score improved from 48 (0 to 80) to 94 (79 to 100) (p < 0.001) and the KSS Functional Score from 52 (5 to 100) to 95 (60 to 100) (p < 0.001). Mean improvement in ROM (p < 0.001) and KSS Knee Score (p = 0.017) were greater in knees with preoperative stiffness compared with the control group, but the KSS Functional Score improvement was comparable (p = 0.885). Conclusion TKA with a 2 mm increased flexion gap provided a significant improvement of ROM in knees with preoperative stiffness. While the improvement in ROM was greater, the absolute postoperative ROM was less than in matched non-stiff knees. PS TKA with patellar resurfacing and a 2 mm increased flexion gap, in combination with adequate soft tissue balancing, provides excellent ROM and knee function when stiffness of the knee had been present preoperatively. Cite this article: Bone Joint J 2020;102-B(4):426–433.
Article
Background It is well-documented in the orthopaedic literature that 1 in 5 patients are dissatisfied following total knee arthroplasty (TKA). However, multiple statistical models have failed to explain the causes of dissatisfaction. Further, payors are interested in using patient-reported satisfaction scores to adjust surgeon reimbursement rates without a full understanding of the influencing parameters. The purpose of this study was to more comprehensively identify predictors of satisfaction and compare results using both a statistical model and a machine learning (ML) algorithm. Methods A retrospective review of consecutive TKAs performed by two surgeons was conducted. Identical perioperative protocols were utilized by both surgeons. Patients were grouped as satisfied or unsatisfied based on self-reported satisfaction scores. Fifteen variables were correlated with satisfaction using binary logistic regression (BLR) and stochastic gradient boosted ML models. Results 1,325 consecutive TKAs were performed. After exclusions, 897 TKAs were available with minimum one-year follow-up. 85.3% of patients were satisfied. Older age generation and performing surgeon were predictors of satisfaction in both models. The ML model also retained CR/CS implant; lack of inflammatory conditions, preoperative narcotic use, depression and lumbar spine pain; female sex, and a preserved PCL as predictors of satisfaction which allowed for a significantly higher area under the ROC curve compared to the BLR model (0.81 vs. 0.60). Conclusion Findings indicate patient satisfaction may be multifactorial with some factors beyond the scope of a surgeon’s control. Further study is warranted to investigate predictors of patient satisfaction particularly with awareness of differences in results between traditional statistical models and ML algorithms. Level of Evidence Therapeutic Level III
Article
Background Adequate soft tissue tension and balance is paramount to achieve favourable outcomes of total knee arthroplasty (TKA). Implant manufacturers offer 1-mm liner increments to fine-tune ligament tension and balance. In this study, we assessed if soft tissue tension changes introduced by minimal changes in liner thicknesses affect early patient reported outcomes.Methods Eighty-nine patients undergoing 99 primary, elective TKAs by a single surgeon were included. After achieving adequate ligament balance, the first 50 knees received an insert that would allow 2–3 mm of medial and lateral opening (control group), whereas the last 49 received an insert which was 1 mm thicker, resulting in a slight increase in ligament tension (study group). Sensor technology was used to record compartmental loads. Knee Society Score (KSS), KOOS Jr., and ROM were recorded pre-operatively, six weeks, four and 12 months post-operatively. The Forgotten Joint Score (FJS) was administered four and 12 months post-operatively.ResultsNo differences were observed in demographic variables, pre-operative outcome scores, and ROM measures between groups. Six weeks post-operatively, there was no statistically significant difference in the outcome variables. Four months post-operatively, statistically significant differences were only observed in KOOS Jr. (79 and 73.6; p = 0.05), and FJS (59.9 and 45.5; p < 0.01); all of which favoured the control group. There was no difference in the outcome variables at 12 months.Conclusion Minor changes in soft tissue tension induced by 1-mm changes in liner thickness resulted in clinically meaningful differences favouring the control group four months post-operatively, but in no clinically noticeable differences 12 months post-operatively. It is possible that lower soft tissue tension may lead to transient improvement in patient-reported early outcomes.
Chapter
Understanding the laxity of the collateral ligaments of the native knee, in extension and flexion, may help surgeons to avoid undesirable outcomes following total knee arthroplasty (TKA). Some authors suggest that medial soft tissue releases or femoral component external rotation may loosen the medial collateral ligament and affect TKA outcomes. Surgeons must perform collateral ligament release to adjust the mediolateral and flexion/extension balance. A looser well‐balanced TKA seems to be better tolerated by patients than a tighter TKA. Numerous TKA surgical techniques have been described to adjust implant position and help balance collateral ligaments in flexion and extension. An unstable TKA is linked with increased complication and revision rates. The collateral ligaments play a significant role in knee balance post TKA and should be carefully considered intraoperatively. The chapter provides recommendations for implementing evidence‐based practice in the clinical setting.
Chapter
Appropriate patient selection is necessary to achieve successful outcomes after total knee arthroplasty (TKAs). Indication for TKAs is an end-stage arthritis not responding to any other treatment. However, infected arthritis is absolute contraindication of TKA. In order to improve postoperative patient satisfaction and prevent complications, the patient’s physical and mental health status besides knee condition should be assessed preoperatively. Materials used for prosthesis should be biologically inert. The type of the prosthesis is divided into CR or PS type depending on PCL retention and fixed or mobile type depending on the method of PE insert fixation. There is no significant difference in clinical outcomes or long-term survival rates based on prosthesis types. The basic principle of performing TKA is to obtain proper soft tissue balancing and restoration of lower limb alignment. In a practical way, mechanical alignment is the most widely used for restoration of limb alignment. Proper soft tissue balancing is also an important factor in the successful outcome of TKA. Therefore, it is necessary to understand the anatomy and function of various soft tissues around the knee. In addition, soft tissue release must be carried out meticulously and gradually to avoid over-release. The most widely used method for prosthesis fixation is cemented fixation. Postoperative management is also important for patient satisfaction and clinical outcomes. Failure to control pain after surgery has a great effect on patient dissatisfaction and function loss. Every effort should be made for decreasing the postoperative pain. Periprosthetic joint infection (PJI) is still the most common cause of failed TKAs. Prevention of PJI is important, but once it occurs, accurate diagnosis and prompt treatment are needed. TKA is a successful surgical method for patients with knee OA. Successful outcomes require proper patient selection, preoperative planning, meticulous surgical techniques, and postoperative planned management. Surgeons should do their best to give patients the best results.
Article
A precept of a successful Total Knee Arthroplasty(TKA) would be a well balanced, stable knee. We analyzed the effects of medial-lateral(ML) stability on functional outcome at 2 years post-operatively. Prospectively collected Joint Registry data of all unilateral primary TKAs between 2004 and March 2008 was used. ML stability(Group 1:< 5°,Group 2:6-9°,Group 3:≥ 10°) was assessed by 3 independent researchers. 1500 patients undergoing 1507 arthroplasties were divided into their various groups. Outcome assessment involved Range of motion(ROM) and functional outcome, using the Knee Society Function Score(KSS), Oxford Knee Score(OKS) and SF-36 score. At 2 years, Group 1 patients reported significantly higher KSS(p < 0.001) and SF-36 scores. All groups had good post-operative ROM. A stable knee(ML stability < 5°) post TKA is likely associated with significantly better functional outcome.
Article
Purpose of the study: The preservation of the posterior cruciate ligament (PCL) was introduced in total knee arthroplasty to improve the quadriceps efficiency and the range of flexion in stairs. The purpose of this study was to determine if these goals were achieved with the Miller-Galante total knee prothesis and to assess the relation between knee laxity and function. Material and Method: We assessed retrospectively the results of 48 consecutives Miller-Galante with PCL retaining. Four patients were excluded: 2 died, 2 lost to follow-up. Forty-four prostheses were evaluated in 38 patients mean aged 65 (33-79). The preoperative HSS score was 41 ± 12.4 [21- 63]. All the components were cemented with patellar resurfacing (25 metal- backed, 19 polyethylene). Stressed Xrays with Telos(TM) device were performed to assess frontal and antero-posterior laxity. All radiographic measurements were carried out with a digitizer (Orthographics(TM)). Results: After 6 years of follow-up, 8 prostheses (18.1 p. 100) were already revised because of: 1) 3 excessive anterior tibial translations and severe polyethylene wear; 2) 5 femoro-patellar disorders. These last 5 knees (4 patellar metal-backed) had a greater patellar thickness [(25 mm ± 1.2) (p = 0.01)]. The mean HSS knee score for the 36 remaining prostheses was 73.8 ± 11.3 (35-92). Only 5 patients were able to climb stairs without support. The mean mechanical axis was 2.3°in varus, but 81 percent of the knees were at 5°around neutral position. The mean laxity in valgus was 4°± 2.3°[1-10], and 4.1°± 2.1° [1-9] in varus. The mean anterior tibial translation was 5.3 mm ± 5 [1-17] and posterior laxity was 4.7 mm ± 2.5 [1-10]. HSS knee score was lowered by 9 points when frontal laxity (valgus + varus) was greater than 5°(p = 0.01), and by 9.8 points when posterior laxity was 5 mm or more (p = 0.02). The mean thickness of the patella was 22 mm ± 2.3 [16-27]. Discussion: These results were unsatisfactory considering the high revision rate and the low functional score observed despite of a correct implant positioning. The major challenge for PCL retaining (i.e. free stair climbing) was achieved in few cases. The wide range of posterior laxity underlined the difficulties to control PCL tension. On the other hand, PCL tension has to be controlled as it could influence knee function. Patello-femoral disorders was the main reason for revision surgery and an insufficient patellar bone resection may be contributive. Sagittal anterior laxity was the second reason for revision and it should be carefully detected as it could drive to catastrophic polyethylene wear. Conclusion: The advantages of PCL retaining were not demonstrated with this low constrained design. Surgical control of PCL tension could give a wide range of posterior laxity. Sagittal femoro- tibial laxity and femoro-patellar disorders should be detected before severe polyethylene wear. These results advocates for: 1)more congruent designs with PCL retaining or for PCL substituting designs, 2) improvement of patello- femoral design.
Article
From 1986 to the present, 126 total knee revisions were performed by the authors. Twenty-five cases (20%) were revised for instability of the tibiofemoral articulation. Patellofemoral instability and those patients treated conservatively were excluded from this subset of patients. All patients were clinically evaluated using the Hospital for Special Surgery knee rating system and radiographically rated using The Knee Society scoring system. The average follow-up period was 28 months. Preoperative synovial fluid analysis showed a predominance of red blood cells (average, 64,000). Reasons for instability were ligamentous imbalance and incompetence, malalignment and late ligamentous incompetence, a deficient extensor mechanism, inadequate prosthetic design, and surgical error. All patients currently have stable knees with an overall improvement in clinical and radiographic scores. When evaluating a patient with a painful knee after total knee arthroplasty, this diagnosis should be considered. Careful physical examination, dynamic radiographs, and synovial fluid analysis should help to make a proper diagnosis. Treatment should aim to correct the cause of instability. The prosthesis chosen should compensate for the specific ligamentous deficiency present.
Article
A new total knee rating system has been developed by The Knee Society to provide an up-to-date more stringent evaluation form. The system is subdivided into a knee score that rates only the knee joint itself and a functional score that rates the patient's ability to walk and climb stairs. The dual rating system eliminates the problem of declining knee scores associated with patient infirmity.
Article
Forty-seven patients who had been treated by 63 total knee arthroplasties were assessed at 12-84 months after the operation. The data were analyzed to determine if collateral ligament laxity had a detrimental effect on the clinical outcome. The Hospital for Special Surgery (HSS) score was used to make the clinical assessment and a modified HSS score, which excluded points awarded for laxity, was also used. Unidirectional (varus or valgus) and total (varus and valgus) laxity were used as a basis of analysis. None of the examined parameters produced results suggesting that lax knees were worse than stable knees. Indeed, knees with increasing laxity through the categories of mild and moderate showed better statistically significant results in HSS score and pain than those with lesser degrees of laxity. Seventy-five percent of the knees with unidirectional laxity were classified as excellent; only 38.5% of the stable knees were graded as excellent (p less than 0.01). Only 9% of the lax knees had complaints of pain; 38% of the stable knees were painful (p less than 0.05). No significant difference in functional score and walking ability was noted between the lax and the stable knees. Seventy-eight percent of the lax knees had a range of motion over 100 degrees; 62.5% of the stable knees achieved this range.
Article
The art and science of total knee arthroplasty (TKA) has come a long way in the last 15 years. TKA has become a highly regarded and frequently recommended procedure. However, some of the uncertainties of the past about selection of design continue today, albeit in modified form. Ten years ago the surgeon was faced with a sometimes bewildering choice of prosthetic devices for which there were various indications. The same remains true today.
Article
This study was designed to determine the influence of laxity on clinical function after knee replacement. Using a recently developed computerized method, anteroposterior laxities were measured in 29 Insall-Burstein posterior stabilized, 25 Kinemax Condylar (posterior cruciate retaining), and 10 Oxford bicompartmental (anterior and posterior cruciate retaining) knee replacements. Laxities of less than 5 min, irrespective of implant design, was associated with an impaired range of passive motion and an increased likelihood of incurring a flexion deformity in excess of 4 degrees. Clinical function, as reflected by the American Knee Society Clinical Rating system, demonstrated a particular sensitivity in the Oxford knee to anteroposterior laxity. It was concluded that anteroposterior laxity in excess of 5 mm in prosthetic knees is desirable for unimpaired joint function, although an upper limit of acceptable anteroposterior laxity could not be identified. These findings, which emphasize the need for attention to ligamentous tensions at the time of surgery, also indicate the need for appropriate weighting of anteroposterior laxity in the continuing evolution of clinical rating systems.
Article
Numerous studies indicate that total knee arthroplasty (TKA) achieves excellent long-term success whether the posterior cruciate ligament (PCL) is saved or excised. In 13 patients, 16 PCL-retaining TKAs were identified with incapacitating instability secondary to early PCL deficiency. Patients with clinical PCL insufficiency present with a triad of subjective complaints: persistent swelling/effusions, anterior knee pain, and giving-way or instability episodes with activities of daily living. Of 13 patients, 12 had at least three postoperative visits with identical subjective complaints before PCL deficiency was diagnosed. On examination all patients exhibited effusion, posterior sag, positive quadriceps active test, and a visible anterior translation of the tibia on the femur while extending the leg from a seated, 90 degree flexed position. This sign has not been previously described to our knowledge but was present in all of our study patients. No patients had radiographic evidence of loosening or osteolysis. Joint aspiration was negative for infection in all patients. No patient had lateral patellofemoral maltracking. By radiographic measurement, the PCL-deficient knees had an average joint line elevation of 10.3 mm, compared with well-functioning TKAs which had an average joint line elevation of 5.0 mm. There was no correlation of PCL deficiency with excessive proximal tibial resection. Nonsurgical intervention provided no improvement in pain or instability. Six patients had improvement of pain, effusion, and stability after revision to a cruciate-substituting implant. We believe that this complication occurs more frequently than is currently being identified and should be considered in problem TKAs with normal radiographs.
Article
Between 1990 and 1995, 25 painful primary posterior cruciate ligament retaining total knee arthroplasties were revised for flexion instability. These patients shared typical clinical presentations that included a sense of instability without frank giving way, recurrent knee joint effusion, soft tissue tenderness involving the pes anserine tendons and the retinacular tissue, posterior instability of 2+ or 3+ with a posterior drawer or a posterior sag sign at 90 degrees flexion, and above average motion of their total knee arthroplasty. The primary total knee arthroplasty was performed for osteoarthritis in 23 patients and rheumatoid arthritis in two patients. There were 13 male and 12 female patients and their mean age was 65 years (range, 35-77 years). Before the revision operation, Knee Society knee scores averaged 45 points (range, 17-68 points) and function scores averaged 42 points (range, 0-60 points). Twenty-two of the knee replacements were revised to posterior stabilized implants and three underwent tibial polyethylene liner exchange only. Nineteen of the 22 knee replacements revised to a posterior stabilized implant were improved markedly after the revision surgery. Only one of three knee replacements that underwent tibial polyethylene exchange was improved. After the revision for flexion instability, Knee Society knee scores averaged 90 points (range, 82-99 points) and function scores averaged 75 points (range, 45-100 points) for the 20 knees with a successful outcome. This study suggests that flexion instability can be a cause of persistent pain and functional impairment after posterior cruciate ligament retaining total knee arthroplasty. A revision operation that focuses on balancing the flexion and extension spaces, in conjunction with a posterior stabilized knee implant, seems to be a reliable treatment for symptomatic flexion instability after posterior cruciate retaining total knee arthroplasty.
Article
We present the midterm results and complications of 101 low contact stress total knee replacements performed in 94 patients and reviewed at an average follow-up of 5.2 years (range, 4-8 years). The mean age at the time of surgery was 66 years (range, 53-76 years). Meniscal bearings were used in 83 knees and a rotating platform in the remaining 18 cases; cemented fixation was used only for 16 tibial components. At most recent follow-up, average knee and function scores were 93 and 78 points. None of the knees was revised because of loosening. Five knees showed distal femoral stress shielding. Complications included infection, supracondylar fracture, patellar component dislodgment, meniscal dislocation (2 cases), catastrophic wear of polyethylene, and progressive osteolysis (2 cases).
Article
The preservation of the posterior cruciate ligament (PCL) was introduced in total knee arthroplasty to improve the quadriceps efficiency and the range of flexion in stairs. The purpose of this study was to determine if these goals were achieved with the Miller-Galante total knee prothesis and to assess the relation between knee laxity and function. We assessed retrospectively the results of 48 consecutive Miller-Galante with PCL retaining. Four patients were excluded: 2 died, 2 lost to follow-up. Forty-four prostheses were evaluated in 38 patients mean aged 65 (33-79). The preoperative HSS score was 41 +/- 12.4 [21-63]. All the components were cemented with patellar resurfacing (25 metal-backed, 19 polyethylene). Stressed X-rays with Telos device were performed to assess frontal and antero-posterior laxity. All radiographic measurements were carried out with a digitizer (Orthographics). After 6 years of follow-up, 8 prostheses (18.1 p. 100) were already revised because of: 1) 3 excessive anterior tibial translations and severe polyethylene wear; 2) 5 femoro-patellar disorders. These last 5 knees (4 patellar metal-backed) had a greater patellar thickness [(25 mm +/- 1.2) (p = 0.01)]. The mean HSS knee score for the 36 remaining prostheses was 73.8 +/- 11.3 (35-92). Only 5 patients were able to climb stairs without support. The mean mechanical axis was 2.3 degrees in varus, but 81 percent of the knees were at 5 degrees around neutral position. The mean laxity in valgus was 4 degrees +/- 2.3 degrees [1-10], and 4.1 degrees +/- 2.1 degrees [1-9] in varus. The mean anterior tibial translation was 5.3 mm +/- 5 [1-17] and posterior laxity was 4.7 mm +/- 2.5 [1-10]. HSS knee score was lowered by 9 points when frontal laxity (valgus + varus) was greater than 5 degrees (p = 0.01), and by 9.8 points when posterior laxity was 5 mm or more (p = 0.02). The mean thickness of the patella was 22 mm +/- 2.3 [16-27]. These results were unsatisfactory considering the high revision rate and the low functional score observed despite of a correct implant positioning. The major challenge for PCL retaining (i.e. free stair climbing) was achieved in few cases. The wide range of posterior laxity underlined the difficulties to control PCL tension. On the other hand, PCL tension has to be controlled as it could influence knee function. Patello-femoral disorders was the main reason for revision surgery and an insufficient patellar bone resection may be contributive. Sagittal anterior laxity was the second reason for revision and it should be carefully detected as it could drive to catastrophic polyethylene wear. The advantages of PCL retaining were not demonstrated with this low constrained design. Surgical control of PCL tension could give a wide range of posterior laxity. Sagittal femoral-tibial laxity and femoro-patellar disorders should be detected before severe polyethylene wear. These results advocates for: 1) more congruent designs with PCL retaining or for PCL substituting designs, 2) improvement of patello-femoral design.
Article
How does the sagittal stability influence the outcome in unconstrained knee arthroplasty? In order to clarify this aspect, 76 arthroplasties (10 male, 66 female, 39x gonarthrosis, 37x rheumatoid arthritis) in 61 patients with unconstrained primary knee arthroplasty were examined with a mean follow-up of 4 years. The determined values were the HSS-Score, the Knee-Society-Score, the range of motion, the flexion contracture as well as the posterior and anterior drawer with the KT 1000. The laxity was defined as the sum of the anterior and posterior drawer. The mean values measured were 2.9 mm for the anterior drawer, 1.9 mm for the posterior drawer and 4.8 mm for the laxity. The total patient population reached 81.3 points in the Knee Score, 70.9 points in the Function-Score and 80.7 points in the HSS-Score. The medium range of motion was determined as 103.5 degrees, the medium flexion contracture as 3.5 degrees. For an anterior drawer of > 6 mm and a posterior drawer of < 1 mm the results deteriorated significantly. A laxity of 8-11 mm gave the best score results. An anterior drawer of < 6 mm, a posterior drawer of 2-5 mm and a laxity of 8-11 mm seem to be recommendable for unconstrained knee arthroplasty.
Article
A loosely balanced total knee arthroplasty (TKA) is reported to produce a good postoperative range of motion (ROM), but too much laxity is thought to be the cause of persistent pain and worsened functionality. The anteroposterior and mediolateral laxity values were measured to evaluate the influence of stability after cruciate-retaining (CR) TKA on ROM and the modified Knee Society score at 4-8 years after the operation. Twenty-one knees in 15 patients with an average age of 68 years who had undergone a CR TKA for osteoarthrosis were examined. The mean preoperative and postoperative ROM was 124 degrees and 112 degrees, respectively. The mean anteroposterior and mediolateral laxity values were 9.7 mm and 10.6 degrees, respectively. No correlation was found between the postoperative ROM and laxity or between the modified Knee Society score and laxity. A loosely balanced TKA did not produce a good postoperative ROM. No parameters suggested that lax knees showed a higher pain score and lower functional score than stable knees.
Article
Instability after total knee arthroplasty is reported to result in implant failure, and substantial instability often requires revision surgery. Successful outcomes can be achieved after revision total knee arthroplasty, particularly if the etiology of the instability is identified before the revision procedure. After careful clinical and radiologic analysis, instability can be classified as extension instability, flexion instability, or genu recurvatum. It is important to understand the causes and recommended treatments of each type of instability.