Cruciate reconstruction using freeze dried anterior cruciate ligament allograft and a ligament augmentation device (LAD)

Abstract

One ACL in each of 11 mature goats was replaced with a freeze dried bone-ACL-bone allograft and a ligament augmentation device (LAD). The LAD was released from its tibial fixation at 3 months postoperation. Bio mechanical, microvascular, and histological changes were evaluated 1 year following implantation. The re constructed knees had a significantly greater total AP translation (3.1 ± 0.5 mm) (mean and SEM) than the contralateral controls (1.0 ± 0.1 mm). Differences in primary AP translation were responsible for 59% of the difference in total translation, with only a 0.6 mm differ ence in secondary translation. Neutral stiffness in the reconstructive knee was 22% of control, while stiffness at 30 N of anterior force was approximately 35% of controls. Ligament stiffness in the linear region for the ACL allograft/LAD was 53% of the control value of 691 N/mm. The maximum load of the allograft/LADs was 1,052 ± 145 N, or 43% of the contralateral ACL control strength (2,448 ± 144 N). Five of the six allografts failed at the femoral insertion. Energy (39%) to maximum load was less for allograft/LADs than controls but elongation to maximum load was the same as control. Histologic evaluation of the allograft/LADs revealed soft tissue cellular ingrowth into the LAD in the extraarticular por tions. No bony growth into the LAD was observed. The collagen fibers of the graft appear to be arranged in a longitudinal orientation although some areas show cha otic collagen fibers. Microangiography revealed a peri- ligamentous and endoligamentous vascular pattern reminiscent of a normal ACL and complete revascular ization of the bone plugs.