Analysis of retrieved polymer fiber based replacements for the ACL

The present retrospective analysis of 117 surgically excised anterior cruci ate ligament (ACL) prostheses was designed to elucidate the etiology and me chanisms of failure of synthetic ligamentous prostheses. They were harveste d from young and active patients (26 +/- 7 yrs) at various orthopaedic cent ers in France between 1983 and 1993. The average duration of implantation o f augmentation and replacement prostheses were 21.5 +/- 12.6 and 33.2 +/- 2 5.3 months, respectively. The principal causes for their excision were rupt ures and synovitis. Each ACL prosthesis was examined macroscopically, histo logically, and, after tissue removal, by scanning electron microscopy (SEM) to determine the model, manufacturer, surgical technique used at implantat ion, the extent of healing, the site of rupture, and the morphology of the damaged fibers. Fourteen types of ACL prostheses were analysed, each fabric ated using a different combination of polymers, fibers and textile construc tions. Consequently, they generated a variety of healing characteristics an d mechanical responses in vivo. SEM observations revealed that abrasion of the textile fibers as a result of yarn-on-yarn and/or yam-on-bone contact w as a common phenomenon to almost all models, and was the primary cause of p rosthetic failure. Healing inside the synthetic ACL was poorly organized, i ncomplete and unpredictable as the extent of collagenous infiltration into the textile structure did not increase with the duration of implantation. I n fact, the collagenous infiltration into certain models appeared to be mor e detrimental than beneficial since it caused deterioration and fraying of the textile structure rather than serving as a reinforcing matrix around th e prosthesis. In conclusion, the present study shows that three mechanisms may be involved in the failure of ACL prostheses: (1) inadequate fiber abra sion resistance against osseous surfaces; (2) flexural and rotational fatig ue of the fibers, and (3) loss of integrity of the textile structure due to unpredictable tissue infiltration during healing. (C) 2000 Elsevier Scienc e Ltd. All rights reserved.