Regeneration process of mechanoreceptors in the reconstructed anterior cruciate ligament.

We performed reconstructive surgery on the anterior cruciate ligament (ACL) of the rabbit using a free bone-patellar tendon-bone (BTB) graft and evaluated nerve regeneration in the graft. The right ACL of 15 Japanese white rabbits was resected and reconstructed using a BTB graft. The BTB and ACL from the contralateral knee served as controls. The graft and control BTB were collected at 2, 4, and 8 weeks after the operation. We measured the number of mechanoreceptors in the ligaments using a modified gold chloride method. In the control patellar tendon, mechanoreceptors were present in all the samples. At 2 weeks after the operation, mechanoreceptors were not observed in the reconstructed ligaments. They were observed at 4 weeks but in lower numbers than in the control knees. At 8 weeks, the total number of mechanoreceptors did not differ significantly in the reconstructed and control tendons. The appearance of mechanoreceptors in the graft between 2 and 4 weeks postoperatively suggests that regeneration of mechanoreceptors occurred during this time period. At 4 and 8 weeks postoperatively, there was no significant difference in the number of mechanoreceptors between the intra-articular portion of grafted tendon and the contralateral ACL. The further increase between 4 and 8 weeks to control levels suggests that this regeneration may restore mechanoreceptors in BTB grafts to normal levels.