Comparison of Initial Fixation Strength Between Biodegradable and Metallic Interference Screws and a Press-Fit Fixation Technique in a Porcine Model

Abstract

The objective of this study was to evaluate the initial fixation strength of a biodegradable interference screw compared with press-fit fixation and a titanium interference screw in anterior cruciate ligament reconstruction using a bone-patellar tendon-bone graft. Porcine lower limbs were used. The specimens underwent 500 loading cycles between 60 and 250 N. This corresponds to loads in the graft during aggressive rehabilitation. Thereafter, intact specimens were loaded to failure. Failure mode was defined by visual analysis. Under cyclic loads none of the interference screw fixations failed. In the press-fit group (angle between load axis and tunnel axis 80 degrees), five specimens failed. The mean maximal load to failure was 945 N (+/- 87) for the titanium screw, 797 N (+/- 60) for the biodegradable screw, and 708 N (+/- 211) for the five press-fit specimens that did not fail during cyclic loading. With respect to primary fixation strength, biodegradable screws are a reasonable alternative to titanium interference screws. The press-fit fixation did not provide a secure fixation in all cases. Five press-fit specimens failed under cyclic loads comparable with those seen under conditions of accelerated rehabilitation.

Porcine models for the metabolic syndrome, digestive and bone disorders: a general overview

“…The rate of bone removal and deposition of the trabecular and cortical bone is also similar to that observed in humans (Mosekilde et al, 1993b). A porcine model has also been used to evaluate the initial fixation strength of a biodegradable interference screw in Litten-Brown, Corson and Clarke anterior cruciate ligament reconstruction using a bone-patellar tendon-bone graft (Seil et al, 1998;Walsh et al, 2009).…”

Testing of prototype interference screw for ACL reconstruction in porcine femurs

“…12,37,38 . In comparative works the bioabsorbable and the metallic screw sometimes come from different manufacturer, thus ensuring different geometry 32,33,34,35 . Most times only screw diameter and maybe the length match between the two screws, thread depths and profi le, head size, tine differ 32,33 .…”

“…Since both metallic and biomaterial used in orthopedic implants are stronger than cancellous bone the pull-out strength for identically shaped screws inserted with the same anatomical attributes (gap size, bone block cross-sectional shape, screw dimensions), should be similar 32 . The majority of original and review works show that bioabsorbable and metallic screws have similar failure loads 33,34,35 . Only a smaller number of works indicate that one screw is better than the other.…”

Comparison of bioabsorbable interference screws and posts for distal fixation in anterior cruciate ligament reconstruction

“…Many reports concerning cyst formation, tunnel enlargement, inflammatory reactions and mechanical failures have been published [3,19,20,22,23]. Doubts still exist about whether PLLA degrades completely at all [16].…”