An in vitro analysis of medial structures and a medial soft tissue reconstruction in a constrained condylar total knee arthroplasty

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.

Increased valgus laxity in flexion with greater tibial resection depth following total knee arthroplasty

“…In this study, a valgus torque of 10Nm was used, which might be insufficient to produce a valgus laxity in extension. However, multiple previous studies have demonstrated valgus laxity using a valgus torque of 10Nm or less [2,5,7,13].…”

A constrained-condylar fixed-bearing total knee arthroplasty is stabilised by the medial soft tissues

“…A previous study investigating the same soft-tissues with an older design of constrained condylar implant (DePuy Synthes Rotating-Platform TC3) and the same loading conditions found an average of 72% across flexion angles ( p = 0.138 by unpaired 2-way t test, n.s.) [ 2 ]. There were similar findings under ± 50 N AP loads: with anterior drawer the medial soft-tissues resisted 51% for both the Attune and the TC3, and with posterior drawer 17% and 21% with the Attune and TC3 respectively ( p = 0.140, n.s.).…”

Tightening medial collateral ligament during total knee arthroplasty for patients with fixed valgus deformity: A novel technique

“…Nevertheless, good stability cannot be achieved without the laxity of MCL. 13 However, extensive loosening of the lateral structure can destroy the rotational stability of knee joint under knee flexion, concentrate the stress of polyethylene liner and increase the wear. At the same time, the radiolucent lines may appear earlier on the tibial plateau, which are visible in 70% of the patients.…”