Abstract
PurposeThe aim of this study was to quantify the medial soft tissue contributions to stability following constrained condylar (CC) total knee arthroplasty (TKA) and determine whether a medial reconstruction could restore stability to a soft tissue-deficient, CC-TKA knee.MethodsEight cadaveric knees were mounted in a robotic system and tested at 0°, 30°, 60°, and 90° of flexion with ±50 N anterior–posterior force, ±8 Nm varus–valgus, and ±5 Nm internal–external torque. The deep and superficial medial collateral ligaments (dMCL, sMCL) and posteromedial capsule (PMC) were transected and their relative contributions to stabilising the applied loads were quantified. After complete medial soft tissue transection, a reconstruction using a semitendinosus tendon graft was performed, and the effect on kinematic behaviour under equivocal conditions was measured.ResultsIn the CC-TKA knee, the sMCL was the major medial restraint in anterior drawer, internal–external, and valgus rotation. No significant differences were found between the rotational laxities of the reconstructed knee to the pre-deficient state for the arc of motion examined. The relative contribution of the reconstruction was higher in valgus rotation at 60° than the sMCL; otherwise, the contribution of the reconstruction was similar to that of the sMCL.ConclusionThere is contention whether a CC-TKA can function with medial deficiency or more constraint is required. This work has shown that a CC-TKA may not provide enough stability with an absent sMCL. However, in such cases, combining the CC-TKA with a medial soft tissue reconstruction may be considered as an alternative to a hinged implant.
Highlights
The original version of this article was revised due to a retrospective Open Access order.University Hospital, Newcastle upon Tyne, UK 4 Musculoskeletal Surgery Group, Department of Surgery and Cancer, Charing Cross Hospital, Imperial College London School of Medicine, London W6 8RF, UKConstrained condylar total knee arthroplasty (CC-TKA) was introduced as a form of knee replacement that offers more stability than conventional posterior-stabilised (PS) TKA [36]
The deep MCL (dMCL) was a significant restraint at 0° and 60° (17 ± 7 and 17 ± 12 %, p = 0.002 and 0.033, respectively)
The reconstruction restraint was significantly lower than the combined medial contributions at 0° flexion; at 60° the reconstruction was significantly higher than the individual superficial MCL (sMCL) contribution (Table 2)
Summary
The larger post-cam mechanism is intended to provide more support in varus–valgus and minimise risk of posterior dislocation of the post. It has been utilised when a primary TKA fails and requires revision [6], or as a more constrained primary choice if the surgeon is unable to balance the knee in both flexion and extension [18]. Further restraint can be found in a rotating hinge (RH) design with linked tibial and femoral components. As the design becomes more constrained and massive, greater loads are transmitted to the implant–bone interface (with less soft tissue support), and loosening becomes a greater
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