Coronal plane laxity of valgus osteoarthritic knee

Abstract

Introduction: Balanced soft tissues are important to total knee arthroplasty (TKA) outcomes. Surgical algorithms for balancing are potentially varied in varus and valgus osteoarthritic (OA) knees. While coronal plane varus knee laxity has been documented, no study has objectively defined the medial and lateral laxity of the valgus OA knee. The lower limb was manipulated at the time of TKA using computer navigation, prior to surgical releases, to allow the limb weight-bearing axis to pass through the knee center in maximum extension, 20 and 90 of flexion. The hip-knee-ankle-angle was documented at this position. Coronal plane laxity was then measured in 30 valgus (7.9 + 4.0) knees as medial and lateral displacement from this point and compared to published values for healthy subjects. In maximum knee extension, lateral contracture was present in 26.6% (8/30) of subjects, and abnormally lax medial tissue was present in 46.6% (14/30). Six patterns of medial versus lateral laxity were documented in maximum extension. In maximum knee extension, mean medial laxity was 7.1 (+3.8) compared to 2.7 (+2.7) laterally. In 20 of knee flexion, mean medial laxity was 8.5 (+3.5) compared to 3.0 (+2.6) laterally. In 90 of knee flexion, mean medial laxity was 3.7 (+1.3) and 7.5 (+3.0) laterally. A highly significant difference (p < 0.0001) in mean laxity was demonstrated when comparing medial versus lateral values at each measurement angle and for medial versus medial and lateral versus lateral values for maximum extension and 90 of flexion. The valgus knee at the time of TKA demonstrates significant preoperative mediolateral and flexion-extension imbalance. In maximum extension, medial tissue is significantly laxer whereas in flexion this reverses and the lateral tissue is significantly laxer. We documented more patterns of medial and lateral laxity in maximum extension than advocated in prior subjective grading systems. These findings demonstrate the challenges of valgus OA knee balancing during TKA but provide, for the first time, objective measures for the starting point of this process.

Less gap imbalance with restricted kinematic alignment than with mechanically aligned total knee arthroplasty: simulations on 3-D bone models created from CT-scans

“…There is, however, debate as to whether the knee’s collateral ligament laxities are modified in knees with less than 15° of deformity (McAuliffe et al. 2017, 2019). Soft-tissue releases are technically demanding, unpredictable, and can even introduce further imbalance (Kumar and Dorr 1997).…”

Which Pre- and Postoperative Coronal Plane Laxity Parameters Influence Patient Satisfaction and Function after Primary Total Knee Arthroplasty?

“…Osteoarthritis has been documented in numerous studies to cause altered tissue laxity in extension or early flexion rather than deeper flexion ranges. [17][18][19][20][25][26][27][28] In a related parameter, the change in lateral sided tissue laxity between 20 and 90 degrees of flexion was significantly negatively correlated with satisfaction outcomes. Practically this means that when greater lateral laxity was seen in early flexion compared with 90 degrees of flexion patients were more satisfied postoperatively which is consistent with the opportunity for surgery to correct this abnormally lax tissue.…”

“…The measurement technique has been previously described in detail for the measurement of coronal laxity in the OA knee. [17][18][19] A medial parapatellar approach to the knee was undertaken. The navigation system was utilized for calculation of the mechanical axes of the femur, tibia, lower limb, and generation of an individualized three-dimensional (3D) model of the patient's anatomy using computer navigation software (BrainLab, Munich, Germany).…”

“…3). [17][18][19][20]23,24 These measurements have been previously validated using modern navigation systems. 20 Once the data were recorded a CAS TKA was performed (►Fig.…”

“…23 Our testing methods were consistent with previously described techniques. [17][18][19][20]23,24,29 It is not possible in an in vivo setting to utilize the same invasive techniques with multiple controlled parameters and measurements that are utilized in cadaver studies, given the ethical implications of prolonging surgery, particularly in relation to infection and fracture risk. Such studies utilize load application systems requiring fixation screws, intramedullary rods, and multiple transections around the knee.…”