Comparison of bone surface and trough fixation on bone–tendon healing in a rabbit patella–patellar tendon injury model

Many orthopedic surgical procedures involve reattachment between tendon and bone. Whether bone–tendon healing is better facilitated by tendon fixation on a bone surface or within a tunnel is unknown. The purpose of this study was to comparatively evaluate the effects of bone surface versus bone trough fixation on bone–tendon healing in a rabbit patella–patellar tendon (PPT) injury model. The rabbits underwent partial patellectomy with patellar-tendon fixation on the osteotomy surface (bone surface fixation, BSF group) (n = 28) or within a bone trough (bone trough fixation, BTF group) (n = 28). The PPT interface was evaluated by macroscopic observation, micro-computed tomography scanning, histological analysis, and biomechanical testing at postoperative week 8 or week 16. Macroscopically, no signs of infection or osteoarthritis were observed, and the regenerated tissue bridging the residual patella and patellar tendon showed no obvious difference between the two groups. There were significantly higher bone mineral density ​and trabecular thickness ​in BSF group compared with BTF group at week 8 ( p  ​< ​0.05 for both). However, the bone volume fraction (BVF), bone mineral density and trabecular thickness in BSF group were significantly lower than those in BTF group ( p  ​< ​0.05 for all) at week 16. Histological analysis demonstrated that new bone was formed at the proximal patella and reattached to the residual patellar tendon through a regenerated fibrocartilage-like tissue in both groups. There was more formation and better remodelling of fibrocartilage-like tissue in BTF group than BSF group at week 8 and week 16 ( p  ​< ​0.05 for both). Biomechanical testing revealed that there was higher failure load and stiffness at the PPT interface in BTF group than BSF group at week 16 ( p  ​< ​0.05 for both). These results suggested that raptured tendon fixation in a bone trough resulted in superior bone–tendon healing in comparison with tendon fixation on bone surface in a rabbit PPT injury model. Although the structural and functional difference of knee joint between human and rabbit limit the results to be directly used in clinical, our research does offer a valuable reference for the improvement of reattachment between bone and tendon.