Initial fixation strength of bioabsorbable and titanium interference screws in anterior cruciate ligament reconstruction - Biomechanical evaluation by single cycle and cyclic loading

We evaluated the initial bone-patellar tendon-bone graft fixation strength of bioabsorbable as compared with titanium interference screws in anterior cruciate ligament reconstruction using matched pairs of porcine knees. Ten pairs underwent single-cycle failure loading at a rate of 50 mm/min,and 10 pairs underwent cyclic-loading at half-hertz frequency. The cyclic loading started with 100 load cycles between 50 and 150 N. We then progressively in creased toads in 50-N increments after each set of 100 cycles. After 100 cy cles at 850 N, the specimens were loaded to failure at a rate of 50 mm/min. In the single-cycle failure loading test, the mean ultimate failure loads (+/- SD) for the bioabsorbable (837 +/- 260 N) and titanium interference sc rews (863 +/- 192 N) were not significantly different, nor were the mean yi eld loads or the-stiffness of the fixation. In the cyclic loading test, the yield loads were 605 +/- 142 N and 585 +/- 103 N for the bioabsorbable and titanium interference screws; respectively (no significant difference). Al though there was no significant difference in-the ultimate failure load, mo re: bone block fractures were found in the grafts fixed with a titanium int erference screw. Bioabsorbable interference screw fixation thus seems to pr ovide a reasonable alternative to titanium screws.