Abstract
The objective of the study was to compare the load to failure between a retro screw
(RS) and a standard interference screw (IS) for tibial-sided anterior cruciate ligament
(ACL) fixation. We used 20 bovine tibia and extensor tendons for the study. A group
of 10 specimens underwent IS fixation while the other 10 underwent RS fixation. Within
each group, five specimens had graft suture in contact (interdigitating) with the
screw threads. All specimens were tested on the MTS 858 Mini Bionix II (MTS Systems,
Shakopee, MN). There was no statistically significant difference between the RS and
IS with respect to peak load to failure. IS with suture interdigitation failed at
an average of 520 N (range: 358 to 793 N), while the RS with suture interdigitation
failed at 613 N (range: 438 to 1089 N). The IS without suture interdigitation failed
at 654 N and the RS without suture interdigitation at 531 N. Specimens with a whipstitch
in contact with the screw did not demonstrate higher pull out strength. The RS fixation
strength appears to equal the IS. Graft suture contact with screw threads does not
increase fixation strength. Based on this study, using a RS for tibial ACL soft tissue
graft fixation is feasible and provides equal fixation strength compared with the
standard IS.
Keywords
anterior cruciate ligament reconstruction - all-inside anterior cruciate ligament
- retro screw - load to failure