A study of retrieved allografts used to replace anterior cruciate ligaments.

Purpose: The purpose of the study was the examination of retrieved whole anterior cruciate ligament (ACL) replacement grafts to determine the rate and the extent of cellular replacement and remodeling of the grafts.

Type Of Study: Gross and histopathologic examination of specimens.

Methods: Nine specimens of ACL replacement allografts and 1 autograft were obtained at autopsy and surgical procedures.

Results: Examination of these specimens from 20 days to 10 years after transplantation revealed a pattern of revascularization similar to that reported in previous biopsy studies. However, examination of the entire allografts showed that, at 2 years after transplantation, the central portions of the grafts remained acellular and that complete attachment was not present, but was found in a 3.5-year post-transplantation specimen.

Conclusions: Because attachment of the graft to bone tunnel walls required over 2 years, the tunnel remodeling may be explained on a mechanical basis. The remodeling of ACL replacement grafts is a gradual or slow process. Complete remodeling and cellular replacement of the entire graft may require 3 years or longer.