Suspensory Versus Interference Screw Fixation for Arthroscopic Anterior Cruciate Ligament Reconstruction in a Translational Large-Animal Model

Purpose: To compare all-inside cortical-button suspensory fixation in sockets versus interference screw fixation in tunnels with respect to clinical, histologic, and biomechanical assessments of all-soft tissue (AST) tendon autografts used for anterior cruciate ligament (ACL) reconstruction in a canine model. Methods: By use of a validated "hybrid" double-bundle ACL reconstruction technique (reconstruction of the anteromedial bundle with preservation of the native posterolateral bundle), dogs were randomly assigned to undergo either suspensory fixation in sockets (n = 6) or interference screw fixation in tunnels (n = 6). Contralateral knees were used as nonoperated controls (n = 12). Quadrupled extensor tendon autografts were used for both ACL reconstruction groups. Dogs were assessed radiographically and functionally and humanely euthanized at 12 weeks after surgery for arthroscopic, gross, biomechanical, and histologic assessments. Results: Histologic assessments showed significantly (P = .018) better graft incorporation with 4-zone direct healing to bone for the grafts using suspensory fixation in sockets (16.3 +/- 1.5) compared with the grafts using interference screw fixation in tunnels (14.2 +/- 2.1). Furthermore, graft healing to bone was significantly better at the aperture (P = .05) and mid-socket (P = .01) location for the group that underwent suspensory fixation in sockets (16.1 +/- 1.8 and 16.4 +/- 1.9, respectively). Conclusions: Suspensory fixation of AST grafts in sockets was associated with superior tendon-to-bone healing compared with interference screw fixation in tunnels, with 4-zone direct graft healing to bone seen for femoral and tibial sockets only in the suspensory-fixation group. Biomechanical properties were similar between groups.