Revascularization and ligamentization of autogenous anterior cruciate ligament grafts in humans

Forty-eight patients were enrolled in a study to determine the time interval for maturity and remodeling following arthroscopically assisted autogenous anterior cruciate ligament reconstruction (ACLR). Two biopsy specimens, one superficial and one deep, at the same level in the midsubstance of the ACL were obtained. Graft age, time from ACL reconstruction to biopsy, ranged from 3 months to 120 months. The patients were placed into four groups, (1) 3 to 6 months, (2) 7 to 12 months, (3) more than 12 months, and (4) control, in accordance with the time following ACL reconstruction. Each specimen was independently evaluated using light microscopy by two different observers in a blinded design. The biopsy specimens were evaluated for vascularity, cellularity, fiber pattern, and metaplasia when compared with the normal ACL. None of the patients was protected from activity as a result of ligament biopsy and no adverse outcomes were reported as a result of biopsy. Our study showed that fiber pattern, cellularity, vascularity, and degree of metaplasia obtained gross histological similarity with a normal ACL by 12 months after autogenous reconstruction. Unexpectedly, no significant statistical differences were noted for all grafts more than 6 months after ACLR, for two of the histological features studied, vascularity and fiber pattern, P=.05. We conclude that by 12 months after autogenous ACLR, graft maturity resembles a normal ACL. Additionally, because no statistical differences were noted in vascularity and fiber pattern after 6 months following autogenous ACLR, significant graft maturity may occur before 12 months. This may allow early postoperative return to full activity and support proponents of accelerated rehabilitation programs following autogenous ACLR.