Soft-Tissue Interference Fixation: Bioabsorbable Screw Versus Metal Screw

Purpose: To compare the biomechanical properties of eccentrically positioned bioabsorbable and titanium interference screws for quadrupled hamstring tendon graft (QHTG) fixation. Type of Study: In vitro, biomechanical study. Methods: In 10 paired cadaveric tibiae and femurs (mean age, 66.5 years; range, 53 to 81 years), QHTG fixation was performed in tunnels sized to within 0.5 mm of QHTG diameter using either a titanium (RCI; Smith & Nephew Donjoy, Carlsbad, CA) or a bioabsorbable (BioScrew; Linvatec, Largo, FL) screw of equal size. Constructs then underwent biomechanical load-to-failure testing on a servo-hydraulic device at 20 mm/min. Results: Load at failure was greater for femoral-side QHTG fixation using the bioabsorbable screw than the titanium screw (486 ± 223.7 N v 246 ± 99.1 N, P = .006); however, displacement did not differ (P = .81). There were no statistically significant differences between groups for tibial side load at failure (P = .54), stiffness (P = .44), or displacement (P = .50). Screw thread-induced graft laceration was more frequently observed in the titanium screw group (9 of 10 grafts during femoral-side testing, 0 of 10 grafts during tibial-side testing) than in the bioabsorbable screw group (0 of 10 grafts during femoral-side testing, 1 of 10 grafts during tibial-side testing). Conclusions: BioScrew interference screw fixation was comparable or superior to RCI titanium interference screw fixation. BioScrew interference screw fixation also produced less screw thread-induced laceration of the QHTG during load-to-failure testing. Clinical Relevance: Use of a biodegradable interference screw positioned directly against a soft-tisse graft provides fixation properties similar to those of a metal interference screw.