Initial fixation strength of two bioabsorbable pins for the fixation of hamstring grafts compared to interference screw fixation: single cycle and cyclic loading

Abstract

Background: During the early postoperative period, the fixation of a hamstring graft to the bone tunnel is the primary factor in limiting rehabilitation.

Hypothesis: The initial fixation strength of a double cross pin fixation technique is comparable with the biodegradable interference screw fixation technique.

Study design: Experimental laboratory study.

Methods: The authors examined the initial fixation strength of two 3.3-mm bioabsorbable pins compared to interference screws for hamstring grafts in bovine knees.

Results: Analysis of yield load, maximum load, and stiffness in the single-cycle loading test showed no statistically significant differences for cross pin and interference fixation (P <.05). For cross pins and interference screws, the mean displacement under 1000 cycles to 250 N was 5.07 ( +/- 1.9) mm and 4.81 ( +/- 2.5) mm, stiffness 252 ( +/- 78) N/mm and 289 ( +/- 148) N/mm. Only grafts fixed with cross pins survived 1000 cycles to 450 N.

Conclusion: The initial fixation strength of the double cross pin technique is comparable to that of interference screw fixation with a stiffness comparable to that of the native ACL.

Clinical relevance: Hamstring graft fixation using two cross pins provides an alternative to bioabsorbable interference screw fixation.