EFFECT OF POSTERIOR CRUCIATE LIGAMENT DEFICIENCY ON TRACKING OF THE PATELLA – A SIMULATIVE CADAVERIC STUDY

Abstract

Introduction: Isolated PCL ruptures are most frequently treated non-operatively, although PCL deficiency may ultimately lead to degenerative changes within the patellofemoral compartment. This study investigated, for the first time under physiological loading conditions, the change in patellar tracking as a result of PCL deficiency, hoping to further understand the clinical consequences in situations where such an injury is treated conservatively.

Method: Using eight fresh cadaveric knees, physiological axial tibiofemoral loads and rotatory torques occurring during level walking, were applied to determine tibial rotation angles. These were then used under dynamic Quadriceps femoris loading to determine contact areas and stresses within the patellofemoral joint at 15°, 30°, 60° and 90° of knee flexion. The PCL was then severed, and the procedure repeated under the same loading conditions.

Results: Significant increases in patellofemoral contact stress in the PCL deficient knees were observed at 15° and 30° knee flexion, both in internal and external rotation of the tibia (TABLE I). For these respective rotation positions the increases were 23% and 20% at 15°, and 19% and 28% at 30°, (in all cases p≤0.05). These significantly increased stresses coincided with unchanged contact patterns on the inferior third of the patella, spanning both its medial and lateral facets.

Conclusions: The increased stresses were due to increased patellofemoral joint reaction force, caused by a decreased angle between the quadriceps and patellar tendons due directly to posterior tibial translation in the PCL deficient knees. Significantly increased patellofemoral contact stresses at 15° and 30° of knee flexion, may be implicated in the degeneration of articular cartilage, on both the medial and lateral facets of the inferior third of the patella. These results point out the need for further biomechanical studies to investigate the effects of more strenuous loading conditions. There is also need for clinical studies to investigate focal lesions associated with long-term PCL deficiency.