THE REMODELING PROCESS OF ALLOGENEIC AND AUTOGENOUS PATELLAR TENDON GRAFTS IN RATS - A RADIOCHEMICAL STUDY

In order to study the remodelling of collagen fibres of transplanted t endons, one-half of the patellar tendon of the knee in 54 rats was rep laced with a radioisotope (H-3-profile)-labelled patellar tendon procu red from a donor rat. Three transplantation models were used in this s tudy: fresh-frozen allograft, fresh-frozen autograft (fresh-frozen iso graft), and fresh autograft (fresh isograft). The percentage of old co llagen was calculated as an indicator of collagen turnover from the am ount of hydroxyproline and the radioactivity level of H-3-hydroxyproli ne in the transplanted tendons at 4, 12 and 24 weeks postoperatively. Histological evaluation was also performed at 2, 4, 12 and 24 weeks. A t 4 weeks, the percentage of old collagen in the grafts from the fresh -frozen allograft group was significantly lower than in the autograft groups (20% vs. 48%). Although the percentage of old collagen in the f resh-frozen autograft group had decreased to the same level as in the fresh-frozen allograft group by 12 weeks (approximately 10%), the valu e was still high in the fresh autograft group at 12 weeks and remained higher (38%). Histologically, at 2 weeks, the cellularity in the fres h-frozen allograft was higher than in the fresh-frozen autograft. Afte r 4 weeks, however, no significant difference was found between these two groups, In the fresh autograft group, the cellularity was lower th an in the fresh-frozen groups at all times. In conclusion, the collage n turnover rate in the fresh-frozen allograft was the most rapid of th e three transplantation models based on hydroxyproline turnover.