Summary

There are no significant differences in load to failure between screw and suture anchor for femoral fixation of an LET, while staple fixation exhibits high rates of early failure and inferior load to failure

Abstract

Background

Lateral extra-articular tenodesis (LET) is an augmentation procedure performed concomitantly in the setting of high-risk primary or revision anterior cruciate ligament reconstruction (ACLR) to provide adjunctive rotational stability. While positive clinical outcomes of the procedure have been demonstrated in randomized controlled trials, the biomechanically ideal fixation technique remains unknown.

Purpose

To evaluate the biomechanical properties of LET performed with onlay staple fixation, inlay interference screw fixation, and an onlay all-suture anchor fixation technique.

Methods

24 non-matched pairs of human cadaveric knees were used in this study. Knees were randomized to receive either cortical staple (n=8), interference screw (n=8), and all-suture anchor (n=8). An LET was performed as described by Chahla et al. for all knees using their respective fixation technique with the knee in 30º of knee flexion. Biomechanical testing was performed using a tensile-testing apparatus (MTS Systems). All knees were subjected to an axially directed pre-load cycle and subsequently assessed for load-to-failure. Primary outcome was load-to-failure. Secondary outcomes were cyclic creep and mechanism of failure. Results were analyzed via analysis of variance (ANOVA) while post-hoc Bonferroni´s test was utilized for pairwise comparison between groups.

Results

(preliminary): Three LETs in the onlay staple fixation group failed during the cyclic loading phase and were thus not subsequently subjected to load-to-failure testing. None of the interference screw or all-suture anchor fixated LETs failed during cyclic loading. The average displacement during cyclic loading was 4.91 mm, 4.05 mm, and 6.58 mm for the staple, interference screw, and all-suture groups, respectively. The average load-to-failure observed in this study was 212.8 N, with a maximum load-to-failure of 304.3 N. The average load to failure was 174.1 N, 250.6 N, and 212.8 N in the staple, interference screw, and all-suture anchor groups, respectively. Upon post-hoc analysis, there was no statistically significant difference between interference screw and all-suture anchor in load-to-failure (p=0.12). However, only the interference screw demonstrated significantly greater load-to-failure compared to staple fixation (p = 0.03) with the all-suture anchor cohort not reaching significance (p >0.05).

Conclusion

There are no significant differences in load to failure between screw and suture anchor for femoral fixation of an LET, while staple fixation exhibits high rates of early failure and inferior load to failure. Suture anchor fixation is an alternative to screw fixation, minimizing tunnel convergence implications. Suture anchor fixation demonstrates greater creep (p = ns between pairwise comparisons), which may reduce the risk of over-constraining the lateral tibiofemoral chamber.