[Macroscopic, histologic and ultrastructural study of 89 prostheses of anterior cruciate ligament excised because of prosthesis failure].

PURPOSE OF THE STUDY

This study concerns the etiology of failed synthetic anterior cruciate ligament (ACL) prostheses, and attempts to identify the primary mechanisms that lead to their premature rupture.

MATERIAL AND METHODS

A total of 89 failed and surgically excised ACL prostheses were retrieved from young and active patients (27 +/- 7 years) at various orthopaedic centres in France. Their average duration of implantation was 34 +/- 24 months. They were examined macroscopically, histologically 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 damage fibers.

RESULTS

Seventy two of these explants represented 6 different models. While all 6 were fabricated from polyester fibres, each had a different textile construction, and each were associated with a unique healing and mechanical response in vivo. SEM observations confirmed that abrasion of the textile fibres were a phenomenon common 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 the synthetic ACL was poorly organized and unpredictable. It did not increase with the duration of implantation. In fact in certain models, it appeared to have caused deterioration and fraying of the textile structure rather than serving as a reinforcing matrix around the prosthesis.

DISCUSSION

A synthetic ACL prosthesis is to be preferred for patients who do not have tissue available for autologous ligamentoplasty. Yet none of the synthetic devices examined in the present study were capable of stabilizing the knee over the long term. Among the factors that influenced their failure we found that the three most common mechanisms were flat abrasion against an osseous surface, flexural and rotational fatigue of the fibres, and loss of integrity of the textile structure due to unpredictable tissue infiltration during healing.

CONCLUSION

The results of the present study show that none of the current models succeed in replacing the natural ACL. Future improvements may be achieved by developing surgical procedures for implantation combined with a prosthesis made from fibres and textile structures which are more abrasion resistant and promote predictable and controlled tissue infiltration.