Patella tracking and patella contact pressure in modular patellofemoral arthroplasty: a biomechanical in vitro analysis.

Introduction: In the recent years modular partial knee prosthesis with the opportunity to combine unicompartmental tibiofemoral (UKA) and patellofemoral prosthesis (PFJ) were introduced to the clinics. To date, little is known about the biomechanics of these bi-cruciate retaining prosthetic designs. Aim of this study was to evaluate the influence of a PFJ in bicompartmental arthroplasty (UKA + PFJ) on patella tracking and retropatella pressure distribution.

Quadriceps force during knee extension in different replacement scenarios with a modular partial prosthesis.

Background: Previous biomechanical studies have shown that bi-cruciate retaining knee replacement does not significantly alter normal knee kinematics, however, there are no data on the influence of a combined medial and patellofemoral bi-compartimental arthroplasty. The purpose of this in vitro study was to evaluate the effect of different replacement scenarios with a modular partial knee replacement system on the amount of quadriceps force required to extend the knee during an isokinetic extension cycle.

Methods: Ten human knee specimens were tested in a kinematic knee simulator under (1) physiologic condition and after subsequent implantation of (2) a medial unicondylar and (3) a trochlear replacement.