LATERAL RELEASE AND PATELLO-FEMORAL TRACKING IN PS MOBILE BEARING KNEE

Abstract

Introduction: Although the problems of patello-femoral kinematics in contemporary total knee arthroplasty are multifactorial, meticulous surgical technique is pivotal in providing optimal and durable function. The goal of this study was to evaluate the incidence of lateral release comparing fixed and mobile bearing posterior stabilized modular press-fit condylar TKA’s with patellar resurfacing.

Materials and methods: Cohort 1 comprised 100 consecutive cemented Press-Fit Condylar Sigma, (Johnson & Johnson, Raynham, Massachusetts) modular total knee prostheses with a posterior cruciate substituting design and dome shaped single peg patellar component implanted prospectively by a single surgeon. Cohort 2 comprised 100 consecutive cemented Press-Fit Rotating Platform Sigma (Johnson & Johnson, Raynham, Massachusetts) modular total knee prostheses with the same posterior cruciate substituting design and patellar component.

The surgical technique comprised cutting the tibial surface perpendicular to the long axis, ligament balancing in extension followed by femoral component rotation referenced off the proximal tibial cut to produce a rectangular flexion gap. The patella was cut to the level of the lateral facet and tibial component rotation was referenced off the center of the ankle. Lateral release was performed if congruent patello-femoral contact was not attained in knee flexion. Clinical and radiographic review was performed as per Knee Society criteria. Additional radiographic evaluation included patellar displacement, tilt, residual bone thickness and coverage ratio. A patient-administered questionnaire was used to evaluate anterior knee pain and patello-femoral function 1 year after surgery.

Results: The incidence of lateral release in the fixed-bearing cohort was 10% 1 compared to 0% in the mobile bearing cohort (p< 0.05). There were no significant differences in terms of clinical or radiographic parameters at short term.

Discussion: This study demonstrates the benefit of self-correction of tibiofemoral rotational mismatch with mobile bearing TKA’s and improvement in patello-femoral tracking. Longer follow-up is necessary to confirm the effect on patello-femoral wear, fixation and durability.