Abstract
Background:To date, there is still no consensus on what soft tissues must be preserved and what structures can be safely released during total knee arthroplasty (TKA) with a medially stabilized implant.Objective:The aim of this study was to analyze the effect of a progressive selective release of the medial and lateral soft tissues in a knee implanted with a medially stabilized prosthesis.Method:Six cadaveric fresh-frozen full leg specimens were tested. In each case, kinematic pattern and mediolateral laxity were measured in three stages: firstly, prior to implantation; secondly, after the implantation of the trial components, but before any soft tissue release; and thirdly, progressively as soft tissue was released with the trial implant in place. The incremental impact of each selective release on knee balance was then analyzed.Results:In all cases sagittal stability was not affected by the progressive release of the lateral soft tissue envelope. It was possible to perform progressive lateral release provided the anterior one-third of the iliotibial band (ITB) remained intact. Progressive medial release could be performed on the medial side provided the anterior fibers of the superficial medial collateral ligament (sMCL) remained intact.Conclusion:The medially conforming implant remains stable provided the anterior fibers of sMCL and the anterior fibers of the ITB remain intact. The implant’s sagittal stability is mainly dependent on its medial ball-in-socket design.
Highlights
In the native knee, during flexion, the medial contact point remains almost fixed, whereas the lateral contact point of the femur translates posteriorly [1]
In all cases sagittal stability was not affected by the progressive release of the lateral soft tissue envelope
Progressive medial release could be performed on the medial side provided the anterior fibers of the superficial medial collateral ligament remained intact
Summary
In the native knee, during flexion, the medial contact point remains almost fixed, whereas the lateral contact point of the femur translates posteriorly [1]. Current total knee arthroplasty (TKA) designs (cruciate retaining, posterior stabilized, and mobile-bearing) do not provide normal kinematics, and “paradoxical” anterior translation of the femur on the tibia during flexion is common [2]. Conforming knee designs offer an alternative, which aims to minimize paradoxical movement thereby mimicking the native kinematics. They feature asymmetric tibial inserts with a highly congruent medial compartment, alongside a less conforming lateral compartment. There is still no consensus on what soft tissues must be preserved and what structures can be safely released during total knee arthroplasty (TKA) with a medially stabilized implant
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