The medial patellofemoral ligament (MPFL) has been recognised as the most important medial structure preventing lateral dislocation or subluxation of the patella (LeGrand 2007). After MPFL rupture the patella deviates from the optimal path resulting in an altered retropatellar pressure distribution. This may lead to an early degeneration with loss of function and need for endoprosthetic joint replacement. The goal of this study was to obtain first data about retropatellar pressure distribution under simulation of physiological quadriceps muscle loading and evaluate the influence of ligament instabilities. On ten fresh-frozen cadaveric knees the quadriceps muscle was divided into 5 parts along their anatomic fiber orientation analogous to Farahmand 1998. Muscular loading was achieved by applying weights to each of the five components in proportion to the cross sectional muscle area (total load 175 N). A custom made sensor was introduced between the patella and femur [Pliance, Novel / Germany]. The sensor consists of 85 single cells. The robot-control-unit is liked to a force-torque sensor. The force free knee-flexion-path from 0° to 90° was calculated during three “passive path” measurements. The actual measurements followed with identical parameters. At first, the retropatellar pressure distribution was recorded with intact ligaments (“native”). After cutting the MPFL the test was repeated. Then double bundle MPFL reconstruction (Schoettle 2009) was performed and the pressure distribution was obtained again. Minimum, mean and maximum pressures and forces were statistically compared in each of the three tested conditions (native Patella with intact MPFL, cut and reconstructed MPFL). We followed the hypothesis that MPFL reconstruction can restore native retropatellar pressure distribution.INTRODUCTION
MATERIALS AND METHOD
