Comparison of the biomechanics and histology of two soft-tissue fixators composed of bioabsorbable copolymers

The purpose of this study was to assess the dynamic in vitro and in vivo ch aracteristics of two different bioabsorbable copolymer soft-tissue fixation devices and to determine their efficacy in reattaching soft tissue to bone . Suretac((R)) fixators (Smith & Nephew/Acufex MicroSurgical Inc., Northwoo d, MA), made of polyglyconate (2:1 glycolic acid: trimethylene carbonate), and Pop Rivets((R)) (Arthrotek, Warsaw, IN), made of LactoSorb((R))(82% pol y L-lactic acid, 18% polyglycolic acid), were anchored into synthetic bone, and their pull-out strengths were evaluated. The devices were also evaluat ed with the use of an ill vivo goat model in which the medial collateral li gament (MCL) was elevated from the tibia and directly reattached. In the il l vitro biomechanical study, the Suretac((R)) fixators had negligible stren gth remaining by four weeks, whereas the Pop Rivets((R)) retained 50% of th eir strength at 4 weeks, 20% at 8 weeks, and negligible strength at 12 week s. The in vivo strength of MCL repairs affected by each implant was not sta tistically different at any of the time points. Histologically, both implan ts were absorbed by 52 weeks, and there was no appreciable adverse tissue r esponse. In conclusion, both copolymer fixators were found to be biocompati ble. The Pop Rivet((R)) fixators demonstrated in vivo performance comparabl e to the Suretac((R)), fixators, although the Pop Rivets((R)) retained stre ngth longer ill vitro. Our results suggest that both devices provide adequa te strength of fixation before degrading to allow the healing soft tissues to reach or surpass their native strength. (C) 2001 John Wiley & Sons, Inc.