An in vitro analysis of patellofemoral contact areas and pressures following procurement of the central one-third patellar tendon

Patients have complained of pain after the use of the central one-third patellar tendon for reconstruction of the anterior cruciate ligament-deficient knee. This study investigated the effect on patellofemoral contact areas and pressures of harvesting the central 10 mm of the patellar tendon in five cadaveric knees. Isometric quad riceps forces were applied to produce approximately 30% of reported maximum voluntary extension mo ments at the knee. Using Fuji pressure-sensitive film, measurements were recorded for three states: the normal knee, after the graft removal, and after the tendon was closed. Contact areas and pressures were measured at 20°, 30°, 60°, and 80° of knee flexion in each specimen. Tests of the reproducibility of our meth ods were performed. Average patellofemoral contact areas for three states ranged from 1.6 cm2 at 20° of knee flexion to 3.0 cm2 at 60°. The average patellofemoral contact pressures ranged from 1.9 MPa at 20° of knee flexion to 3.0 MPa at 30°. At each flexion angle there were no significant differences in average patellar contact area or pressure for the three states ( P < 0.05). These results suggest that neither harvesting the central 10 mm of the patellar tendon, nor closing the gap, significantly alters patello femoral contact area or pressure.