Effects of partial patellectomy and reattachment of the patellar tendon on patellofemoral contact areas and pressures.

We used a previously reported experimental method to measure patellofemoral contact areas and pressures in four pairs of human cadaveric knees before and after a partial patellectomy. The knee joints were loaded by application of a flexion moment, which was resisted by the extension moment of the quadriceps mechanism. Patellofemoral contact was measured with the use of pressure-sensitive film, at 30, 60, and 90 degrees of flexion of the knee. Partial patellectomy decreased the patellofemoral contact area and increased pressure. We observed alterations in the patterns of contact, including a proximal shift in patellofemoral contact, after partial patellectomy. An anterior reattachment of the patellar tendon significantly minimized the effects of 20 and 40 per cent patellectomies (p < 0.05). After a 60 per cent patellectomy, patellofemoral contact was altered markedly, with the contact area reduced to less than 50 per cent of the control values regardless of the position of the patellar tendon reattachment.