Lateral laxity in flexion increases the postoperative flexion angle in cruciate-retaining total knee arthroplasty

Thirty-eight patients diagnosed with osteoarthritis underwent 41 cruciate-retaining total knee arthroplasties. In varus and valgus tests at flexion, subjects were seated on a table at 80° of knee flexion; 50 N was applied perpendicular to the lower leg. The factors affecting the postoperative flexion angle were investigated in a multiregression analysis. The mean joint angles of the flexion-valgus and flexion-varus tests were 3.4° ± 1.4° and 6.2° ± 2.5°, respectively. The flexion-varus angle was correlated with the postoperative flexion angle (P < .01). The mean postoperative flexion angles were 110.8° ± 9.6° and 118.1° ± 8.0° in the groups with the flexion-varus angle of 6° or less and more than 6°, respectively (P = .02). Slack lateral laxity in flexion had a significant effect during knee flexion in cruciate-retaining total knee arthroplasty.     

Joint line changes in cruciate-retaining versus posterior-stabilized computer-navigated total knee arthroplasty

Introduction

This study compared joint line changes and functional outcomes between cruciate-retaining (CR) and posterior-stabilized (PS) computer-navigated total knee arthroplasties (TKAs). With the increased precision offered by computer navigation, we hypothesized that there should be minimal differences in the joint line changes between the groups and thus no significant differences in the clinical outcomes.

Materials and methods

A retrospective study of 195 patients with a minimum of 2-year follow-up following primary surgery was conducted. The patients were stratified into two groups: the CR group and the PS group. The joint line changes of both groups were then compared using the Student t test. Multivariate analysis and regression modelling were then utilized to analyze the functional outcomes of both groups.

Results

CR knees had a significantly lesser mean joint line change of 1.70 mm as compared to 2.34 mm in PS knees (p = .04) but the absolute difference was only 0.64 mm. The PS group had significantly better final range of motion of 122° (±9.9°) as compared to 114° (±15.0°) in the CR group (p < .0001). There were no significant differences in the final outcome scores.

Conclusion

Although there is a significant difference statistically in the joint line changes between the groups, this difference is less than 1 mm and probably has no significant clinical impact. This is further affirmed by the fact that there was no significant difference in the clinical outcomes. The increased range seen in PS knees is probably not related to joint line changes.

Level of evidence

III.     

Factors affecting flexion gap tightness in cruciate-retaining total knee arthroplasty

With the exception of flexion gap tightness, which is common in cruciate-retaining (CR) total knee arthroplasty (TKA), the risk factors of flexion gap tightness have not been described. This retrospective study characterized factors that are associated with flexion gap tightness in CR TKA. Data on 203 consecutive knees that underwent CR TKA were reviewed. The prevalence rate of flexion gap tightness was 21.1%. By logistic regression analysis after adjusting for age, preoperative flexion contracture, and referencing method used for femoral sizing, insufficient tibial slope remained a significant independent risk factor of flexion gap tightness. Although excessive tibial slope should be avoided, the findings of the present study demonstrate that the risk of flexion gap tightness can be reduced by increasing the tibial slope in CR TKA.     

Kinematic factors affecting postoperative knee flexion after cruciate-retaining total knee arthroplasty

Purpose

The purpose of this study was to investigate kinematic factors affecting postoperative knee flexion after cruciate-retaining (CR) total knee arthroplasty (TKA) by analysing pre- and postoperative knee kinematics.

Methods

We retrospectively analysed 58 patients with osteoarthritis who received the same implant series. Pre- and postoperative kinematics were measured intraoperatively using a navigation system. As a clinical outcome, we measured the knee flexion angle before and one year after surgery. Correlations among pre- and postoperative kinematics and postoperative flexion were analysed using simple linear regression analyses.

Results

Preoperative knee kinematics, including tibial internal rotation and anterior translation (R?=?0.87, P?<?0.001; R?=?0.53, P?<?0.001, respectively), were significantly correlated with postoperative kinematics. Preoperative varus–valgus movements improved significantly postoperatively; however, tibial internal rotation remained unchanged. Furthermore, postoperative knee flexion angle was significantly correlated with postoperative tibial internal rotation (R?=?0.45, P?<?0.001).

Conclusions

Preoperative knee kinematics were unchanged even after CR-TKA. Postoperative tibial internal rotation is one of the most important factors affecting postoperative knee flexion.     

Intraoperative loose flexion gap may restrict postoperative knee flexion after J-curve design posterior-stabilized total knee arthroplasty

Introduction

Although soft tissue tension during total knee arthroplasty (TKA) has been targeted to achieve equal flexion and extension gaps, such a perfect gap is not always obtained. This study was performed to investigate the impact of difference between flexion and extension gaps on postoperative knee flexion angle.

Materials and methods

We reviewed 107 consecutive TKAs using a J-curve design posterior-stabilized prosthesis. Soft tissue tension was measured intraoperatively using an offset-type tensor under 30 lb force of joint distraction with the patella reduced. All TKAs were performed in a uniform manner including the subvastus approach and without use of a pneumatic tourniquet. We assessed the association between knee flexion angle 1 year after TKA and the difference between flexion and extension gaps using Pearson’s product-moment correlation and multiple regression analysis with age, sex, body mass index, diagnosis, history of diabetes mellitus, preoperative flexion angle, and gap difference as explanatory variables.

Results

The difference between flexion and extension gaps showed a slight negative correlation with postoperative knee flexion angle in univariate analysis (r = − 0.20, 95% CI, − 0.38 to − 0.01, p = 0.04). Multiple regression analysis showed that the gap difference was an independent factor associated with postoperative knee flexion angle (β = − 0.89, 95% CI, − 1.60 to − 0.18, p = 0.01).

Conclusions

The difference between flexion and extension gaps was negatively correlated with postoperative knee flexion angle. Looser flexion gap compared with extension gap should be avoided in J-curve design posterior-stabilized TKA.

     

股骨后髁偏距与高屈曲后稳定型全膝置换术后膝关节屈曲度的相关性分析

目的 分析股骨后髁偏距与高屈曲后稳定型全膝关节置换术中、术后膝关节屈曲度的相关性,探讨其在股骨假体设计中的意义.方法 前瞻性分析2005年3月至2006年10月使用NexGen LPS-Flex假体行单侧全膝关节置换术的男性(男性组)、女性(女性组)各50例骨关节炎患者临床与影像学资料.对患者手术前、后股骨后髁偏距的改变值与术中及术后2年膝关节屈曲度改善值的相关性进行分析.结果 100例患者术后股骨后髁偏距较术前减小(3.4±3.3)mm,减小程度女性高于男性[女性:(-5.4±3.1)mm,男性:(-1.5±2.0)mm,P<0.05].后髁偏距的改变值与术后2年膝关节屈曲度改善值在患者整体内并无相关性(P>0.05).但若分别在男性与女性组内对其观察,则两者间均呈具有正向相关性(P<0.05);术中患者整体、男性组、女性组内膝关节屈曲度改善值均与后髁偏距的改善值呈正向相关性(P<0.05).结论 重建股骨后髁偏距与高屈曲后稳定型全膝置换术后膝关节屈曲度的获得间存在相关性;使用以西方人解剖参数设计的假体不能充分匹配国人特别是我国女性股骨远端的几何学形态,兼以前参照技术进行前后髁截骨通常会导致其后髁偏距的减少,降低了其获得更大膝关节屈曲度的可能,假体设计有必要考虑不同种族和性别间的解剖差异.     

Influence of intra-operative parameters on postoperative early recovery of active knee flexion in posterior-stabilized total knee arthroplasty

Purpose

Active knee flexion is more important for daily activities than passive knee flexion. The hypothesis is that the intra-operative parameters such as osteotomized bone thickness and soft tissue balance affect the postoperative active flexion angle in total knee arthroplasty (TKA). Therefore, we evaluate the influence of intra-operative parameters on postoperative early recovery of active flexion after posterior-stabilized (PS) TKA.

Methods

The subjects were 45 osteoarthritic knees undergoing primary PS TKA with anterior-reference technique. Intra-operative soft tissue balance was measured using an offset type tensor, and each osteotomized bone thickness was also measured. Pre- and postoperative active knee flexion angles were measured using lateral radiographs. Liner regression analysis was used to determine the influence of these intra-operative parameters on postoperative active flexion angles or recovery of active flexion angles.

Results

Pre-operative flexion angle was positively correlated with postoperative flexion angle (R?=?0.52, P?=?0.0002). Postoperative flexion angle was negatively correlated with the osteotomized bone thickness of femoral medial posterior condyle (R?=??0.37, P?=?0.012), and femoral lateral posterior condyle (R?=??0.36, P?=?0.015). Recovery of flexion angle was slightly negatively correlated with gap difference calculated by subtracting joint gap at extension from that at flexion between osteotomized surfaces (R?=??0.30, P?=?0.046).

Conclusions

The osteotomized bone thickness of the femoral posterior condyle is a significant independent factor of postoperative flexion angles. This indicates that the restoration of the posterior condyle offset may lead to larger postoperative active flexion angles in PS TKA.     

Intraoperative soft tissue balance reflects minimum 5-year midterm outcomes in cruciate-retaining and posterior-stabilized total knee arthroplasty

With the use of an offset type tensor for total knee arthroplasties (TKAs), intraoperative soft tissue balance including the joint component gap and ligament balance was measured in 41 varus-type osteoarthritic patients (19 cruciate-retaining [CR] TKAs and 22 posterior-stabilized [PS] TKAs), and the correlations between the intraoperative values and the postoperative values assessed by stress radiographs at extension and flexion were examined at a minimum 5-year follow-up. In CR TKAs, the postoperative soft tissue balances at both angles were significantly correlated with the intraoperative values. In PS TKAs, the postoperative soft tissue balances at extension, not flexion, were significantly correlated with the intraoperative values. In conclusion, the intraoperative condition of the soft tissue balance reflected the postoperative values especially in CR TKAs even at 5-year midterm follow-ups.     

The stability of the cemented tibial component of total knee arthroplasty: posterior cruciate-retaining versus posterior-stabilized design

Micromotion of the tibial component in 40 knee arthroplasties for gonarthrosis was studied using Roentgen stereophotogrammetric analysis. The stability of this component was assessed for 2 years' postoperatively. In all arthroplasties, an attempt was made to reconstruct the preoperative posterior slope. Posterior cruciate-retaining (CR) and posterior-stabilized (PS) components showed at 2 years a maximum total point motion of 0.6 +/- 0.4 mm and 0.7 +/- 0.5 mm, respectively. Whereas 92.5% of the implants were determined to be stable, 1 of the CR group and 2 of the PS group displayed migration between the first and the second year of at least 0.2 mm. A negative correlation between subsidence of the tibial component at 2 years of follow-up and the difference between preoperative and postoperative tibial slope was found. Consequently, we suggest that restoring the original posterior slope of the tibial plateau must be a goal of tibial component implantation.     

Differences in articular track area of posterior-stabilized and cruciate-retaining retrieved total knee implants

Press-fit condylar total knee arthroplasties removed at revision surgery from 27 knees were examined. Fourteen of the implants were posterior-stabilized press-fit condylar systems and 13 were cruciate-retaining press-fit condylar systems. The articular track areas were examined using a digital camera and manual measurements. Findings revealed the track area in posterior-stabilized implants (93%) was larger than in cruciate-retaining implants (59%). Mean posterior distance ratio of the articular track from the posterior limit of the polyethylene was 2% (.08 cm) for posterior-stabilized implants versus 23% (.97 cm) for cruciate-retaining implants. No differences in wear rating were noted. The pattern of articular contact in cruciate-retaining knees demonstrated little migration of the femoral contact surface across the tibial polyethylene plateau.     

Tibial post impingement in posterior-stabilized total knee arthroplasty

Reports of posterior-stabilized total knee replacements have shown excellent clinical success. However, tibial post-femoral cam impingement has been seen in modular component retrievals. This finding has been associated with transmission of rotational forces to the modular tray-polyethylene interface with subsequent backside polyethylene wear and the development of osteolysis. Femoral cam-tibial post designs that allow hyperextension and limit rotational constraint may minimize this impingement. Technical considerations including the avoidance of femoral component flexion and posterior tibial slope will minimize anterior tibial post impingement.     

Effect of flexion angle on coronal laxity in patients with mobile-bearing total knee arthroplasty prostheses

Proper soft tissue tension is one of the important factors in mobile-bearing total knee arthroplasty (TKA). We evaluated varus/valgus laxities, particularly at flexion, which is a key factor in reducing the risk of subluxation and dislocation of bearings to assess the effect that the flexion angle and the presence or absence of the posterior cruciate ligament (PCL) have on laxity in patients with low-contact stress (LCS) prostheses of the PCL-retaining (24 patients, 24 knees) and PCL-sacrificing (24 patients, 24 knees) type designs during extension and flexion. Both types of prosthesis had about 4° laxity at extension and 3° at flexion. PCL-retaining prostheses had significantly less laxity at flexion than at extension (P = 0.0004 in varus, P = 0.0043 in valgus). For good clinical outcomes following TKA, 3°–4° laxity in the varus and valgus orientations is recommended. In addition, the PCL might be involved in flexion and could affect varus/valgus laxity in PCL-retaining prostheses.     

国产TC-Dynamic(后稳定型)膝关节假体置换的临床应用

目的：膝关节置换在国内已广泛开展,发展合适国人自身的假体意义重大,本研究介绍了国产TC-Dy—namic（后稳定型）膝关节置换系统在临床的应用体会。方法：自2003年1月至2004年12月,对51例患者行TC-Dy—namic膝关节置换。男19例,女32例;年龄71—84岁,平均（76．4±4．1）岁;骨性关节炎37例,类风湿性关节炎14例;病程5～40年,症状主要为疼痛及活动受限。术前术后行HSS评分和X线检查。结果：随访48-61个月,术后3个月随访所有患者,HSS评分平均（86．1±7．7）分（63～95分）;共32例患者获48个月随访,HSS评分平均（83．5±8．1）分（60±95分）。负重位X线检查力线测量结果：术前平均膝内翻（21．0±5．8）°（9°±30°）,术后下肢力线基本正常。无感染、假体松动或髌骨脱位等并发症。结论：作为根据国人膝关节解剖特点设计的后稳定型膝关节假体置换术中期疗效满意,长期疗效有待观察。     

Femoral rollback after cruciate-retaining and stabilizing total knee arthroplasty

Limited data comparing the kinematics of posterior cruciate ligament-retaining or substituting total knee arthroplasty with its own intact knee under identical loadings is available. In the current study, posterior femoral translation of the lateral and medial femoral condyles under unloaded conditions was examined for intact, cruciate-retaining, cruciate ligament-deficient cruciate-retaining and posterior-substituting knee arthroplasties. Cruciate-retaining and substituting total knee arthroplasties behaved similarly to the cruciate-deficient cruciate-retaining total knee arthroplasty between 0 degrees and 30 degrees flexion. Beyond 30 degrees, the posterior cruciate-retaining arthroplasty showed a significant increase in posterior translation of both femoral condyles. The posterior cruciate-substituting arthroplasty only showed a significant increase in posterior femoral translation after 90 degrees. At 120 degrees, both arthroplasties restored approximately 80% of that of the native knee. Posterior translation of the lateral femoral condyle was greater than that observed in the medial condyle for all knees, indicating the presence of internal tibial rotation during knee flexion. The data showed that the posterior cruciate ligament is an important structure in posterior cruciate-retaining total knee arthroplasty and proper balancing is imperative to the success of the implant. The cam-spine engagement is valuable in restoring posterior femoral translation in posterior cruciate-substituting total knee arthroplasty.     

Sagittal laxity in vivo after total knee arthroplasty

Introduction A stress arthrometry study of 77 knees undergoing total knee arthroplasty was performed to determine the difference in anteroposterior (AP) laxity between posterior cruciate ligament (PCL)-retaining (PCLR) and PCL-substituting (PCLS) prostheses using the Genesis I TKA.Materials and methods Fifty-three knees had PCLR and 24 had PCLS prostheses. The selected patients had successful arthroplasties after a minimum follow-up of 5 years. AP laxity was measured with a KT-2000 arthrometer (Medmetric, San Diego, CA, USA) using standard protocols.Results At 30° of flexion, there was no statistical difference in anterior (PCLR: 4.7 mm, PCLS: 4.5 mm), posterior (PCLR: 1.1 mm, PCLS: 0.7 mm), or total (PCLR: 5.8 mm, PCLS: 5.3 mm) displacement. At 75°, significant differences were seen in both anterior (PCLR: 3.3 mm, PCLS: 2.3 mm) and total (PCLR: 4.8 mm, PCLS: 3.4 mm) displacement (p=0.001 and p=0.009, respectively), although there was no statistical difference in posterior displacement (PCLR: 1.5 mm, PCLS: 1.1 mm).Conclusion The above values are considered the suitable degree of AP laxity in total knee arthroplasty for a satisfactory clinical outcome 5–9 years after surgery. The PCL in a PCLR prosthesis and the central tibial spine and femoral cam in a PCLS prosthesis might play comparable roles in determining the laxity in the posterior direction in these prostheses.     

Concave versus posterior-stabilized tibial joint surface in total knee arthroplasty: randomized evaluation of 47 knees

Forty-seven knees in 43 patients with severe deformities randomly received AMK total knee arthroplasty with concave (C, n = 25) or posterior-stabilized (PS, n = 22) polyethylene insert and with resection of the posterior cruciate ligament. Radiostereometric examinations were done postoperatively and after 3, 12, and 24 months. Two patients (1 C, 1 PS) underwent revision surgery. At the 2-year follow-up, the median absolute rotations of the tibial inserts ranged from 0.13 degrees to 0.26 degrees (C vs PS; P =.1-.7). The maximum total point motion was almost identical in the 2 groups (C, 0.38; PS, 0.39; P =.9). Maximum subsidence, lift-off, and Hospital for Special Surgery scores did not differ (P =.1-.6). Recipients of 20 of 24 knees with concave design and 14 of 19 knees with posterior-stabilized design reported that their knee could be regarded as normal or almost normal. Variations of the configuration of the polyethylene insert did not alter the outcome in the short term.     

Preoperative laxity in osteoarthritis patients undergoing total knee arthroplasty

A preoperative quantitative evaluation of soft tissues is helpful for planning total knee arthroplasty, in addition to the conventional clinical examinations involved in moving the knee manually. We evaluated preoperative coronal laxity with osteoarthritis in patients undergoing total knee arthroplasty by applying a force of 150 N with an arthrometer. We examined a consecutive series of 120 knees in 102 patients. The median laxity was 0° in abduction and 8° in adduction. The femorotibial angle on non-weight-bearing standard anteroposterior radiographs was 180° and correlated with both abduction (r = −0.244, p = 0.007) and adduction (r = 0.205, p = 0.025) laxity. The results of a regression analysis suggested that the femorotibial angle is helpful for estimating both laxities. Considering the many reports on how to obtain well-balanced soft tissues, stress radiographs might help to improve the preoperative planning for gaining the optimal laxity deemed appropriate by surgeons.

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Résumé  Une analyse avec évaluation quantitative préopératoire des tissus mous est nécessaire dans la planification d’une prothèse totale de genou, ceci en plus des examens cliniques conventionnels, notamment en ce qui concerne l’évaluation de la mobilité. Nous avons évalué, en préopératoire, les laxités ainsi que les stades de l’arthrose chez les patients qui ont bénéficié d’une prothèse totale du genou. Ces résultats ont été réalisés à l’arthromètre. Nous avons réalisé une série consécutive de 120 genoux chez 102 patients. La laxité moyenne était de 0° en abduction et de 8° en adduction. L’angle fémoro tibial, sans appui, sur les radiographies de face et de profil était de 180° et a été corrélé avec la laxité en abduction (r = −0.244, p = 0.007) et en adduction (r = 0.205, p = 0.025). Les résultats nous montrent que l’angle fémoro tibial est utile pour estimer les laxités. Si l’on considère les différentes études et la meilleure manière d’obtenir une bonne balance ligamentaire, les radiographies en stress permettent d’optimiser le planning opératoire et d’avoir une bonne idée des laxités.

     

Long-term follow-up and survivorship of single-radius,posterior-stabilized total knee arthroplasty

Background

We sought to determine the 10-year survivorship of single-radius, posterior-stabilized total knee arthroplasty (TKA) in Asian patients. We also aimed to determine whether the long-term clinical and radiographic results differed between patients with and without patellar resurfacing.