Alteration of patellofemoral contact during healing of canine patellar tendon after removal of its central third

Alterations of the patellofemoral (PF) contact pressure and area were asses sed using pressure-sensitive film after the removal of the central third of patellar tendon (PT) with healing over time in twelve dogs. The contralate ral knee served as control. Histological sections were prepared for descrip tive evaluation. No alterations in PT strain, PF contact pressure and area were measured immediately after the removal of the central third of PT comp ared with that before its removal. Compared with contralateral control, the healing of the donor PF induced a significantly increased PF contact area but not PF contact pressure in the specimens harvested at 6, 12, and 18 mon ths after operation. Increased PF contact area indicated a proximal shift o f the PF joint contact during flexion, which was associated with an increas ed strain of the healing PT under loading. The healing PT became hypertroph ic compared with control, but the differences in the cross-sectional area w ere reduced over time. Histologically, a poorly organized extracellular mat rix was observed at 6 months, with a progressive improvement in collagen fi ber alignment up to 18 months postoperatively. The results of this study su ggest that the removal of the central third of PT does not immediately chan ge PF contact pressure and areas. However, remodeling of the healing tendon may cause an elongated PT, resulting in an increase in PF contact area und er a given quadriceps force by knee extension. (C) 2000 Elsevier Science Lt d. All rights reserved.