MACROSCOPIC, HISTOLOGIC AND ULTRASTRUCTUR AL ANALYSIS OF 89 SURGICALLY EXCISED ANTERIOR CRUCIATE LIGAMENT PROSTHESIS

Purpose of the study This study concerns the etiology of failed synthe tic anterior cruciate ligament (ACL) prostheses, and attemps to identi fy the primary mechanisms that lead to their premature rupture. Materi al and methods A total of 89 failed and surgically excised ACL prosthe ses were retrieved from young and active patients (27 +/- 7 years) at various orthopaedic centres in France. Their average duration of impla ntation was 34 +/- 24 months. They were examined macroscopically, hist ologically and by scanning electron microscopy (SEM) to determine the model, the manufacturer, the surgical technique used at implantation, the extent of healing, the site of rupture, as well as the morphology of the damaged fibers. Results Seventy two of these explants represent ed 6 different models. While all 6 were fabricated from polyester fibr es, each had a different textile construction, and each were associate d with a unique healing and mechanical response in vivo. SEM observati ons confirmed that abrasion of the textile fibres were a phenomenon co mmon to all models, and were the primary cause of prosthesis failure. Such wear zones were particularly prevalent at the exit of the tibial tunnel and around the femoral condyle. Collagenic infiltration into th e synthetic ACL was poorly organized and unpredictable. It did not inc rease with the duration of implantation. In fact in certain models, it appeared to have caused deterioration and fraying of the textile stru cture rather than serving as a reinforcing matrix around the prosthesi s. Discussion A synthetic ACL prosthesis is to be preferred for patien ts who do not have tissue available for autologous ligamentoplasty. Ye t none of the synthetic devices examined in the present study were cap able of stabilizing the knee over the long term. Among the factors tha t influenced their failure we found that the three most common mechani sms were flat abrasion against an osseous surface, flexural and rotati onal fatigue of the fibres, and loss of integrity of the textile struc ture due to unpredictable tissue infiltration during healing. Conclusi on The results of the present study show that none of the current mode ls succeed in replacing the natural ACL. Future improvements may be ac hieved by developing surgical procedures for implantation combined wit h a prosthesis made from fibres and textile structures which are more abrasion resistant and promote predictable and controlled tissue infil tration.