Paper 284: Double Bundle Anterior Cruciate Ligament Reconstruction Using a Polylactide Carbonate (CALAXO) Osteoconductive Interference Screw

Abstract

The purpose of this study was to describe our experience of the new Polylactide Carbonate (Calaxo) Osteoconductive interference screw (Smith & Nephew) when used for both femoral and tibial graft fixation in Double Bundle ACL reconstruction. Since May 2006, patients with an ACL deficient knee were reconstructed using the Double Bundle technique. All were followed prospectively and outcome data collected. Evidence of fixation failure was established subjectively by clinical examination (Pivot Shift) and objectively via KT-1000 arthrometer. Following ethical approval, post-operative CT scans (immediate and 12-18 months) were performed on five (a further 5 awaited) patients allowing assessment of tunnel dimensions/fill. Twenty nine patients (26 male, 3 female) with a mean age of 30 (range 18-47) were included. At last follow-up, no evidence of graft/fixation failure was found; KT-1000 mean side-side difference 1.4mm (range −3 to +6). All patients had a positive pivot shift preoperatively which was abolished postoperatively. Subjective IKDC score was significantly improved with a mean of 76.27% (SD 17.38) at last review compared with 54.02% (SD 17.86) preoperatively (t (22) = −5.37, p<0.05) One patient had a postoperative infection with no other complications reported. Radiologically the screws did not show complete resorption in 2 cases, with significant tunnel widening found on 3 cases. Some evidence of new bone formation was noted but not found to be significant. We have shown satisfactory clinical results with use of the Calaxo screw when used in Double Bundle ACL Reconstruction. However, radiologically the ostoeconductive properties of the screw shown in the pre-clinical animal model were not evident. This study helps illustrate that preclinical animal data cannot necessarily be translated into human practice. Surgeons should proceed with caution when using new biological implants tested purely in animal models. Although we have not had any cases of the reported adverse local soft tissue reaction associated with Calaxo, we support Smith & Nephew's decision to withdraw the screw from clinical use.