Muscle-Driven Total Knee Replacement Stability with Virtual Ligaments

TL;DR

This paper introduces a new system to test knee implants by combining muscle and ligament simulations, improving the accuracy of joint stability assessments.

Contribution

The study introduces a muscle actuator system that integrates muscle-driven motion with virtual ligaments for more realistic TKR stability testing.

Findings

Muscle forces are essential for active joint stability in TKR simulations.

Physiological representations of collateral ligaments significantly affect laxity test outcomes.

Abstract

Knee joint stability comprises passive (ligaments), active (muscles), and static (articular congruency) contributors. The stability of total knee replacement (TKR) implants can be assessed pre-clinically using joint motion simulators. However, contemporary testing methods with these platforms do not accurately reproduce the biomechanical contributions of passive stabilizers, active stabilizers, or both. A key component of joint stability is therefore missing from laxity tests. A recently developed muscle actuator system (MAS) pairs the quadriceps-driven motion capabilities of an Oxford knee simulator with the prescribed displacements and laxity testing methods of a VIVO robotic knee testing system, which also includes virtual ligament capabilities. Using a TKR-embedded non-cadaveric joint analogue, TKR with two different virtual ligament models were compared to TKR with no active ligaments. Laxity limits were then obtained for both developed models using the conventional style of laxity testing (the VIVO’s force/displacement control) and compared with results obtained under similar conditions with the MAS (gravity-dependent muscle control). Differences in joint control methods identified the need for muscle forces providing active joint stability, while differences in the effects of the virtual ligament models identified the importance of physiological representations of collateral ligaments during testing.

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