Summary

Knotless all-suture anchors were found to be a viable alternative to conventional, onlay fixation techniques in the setting of a modified Lemaire lateral extra-articular tenodesis.

Abstract

Introduction

Spiked ligament staples (SLS) and biocomposite suture anchors (BSA) are commonly used onlay fixation devices for modified Lemaire lateral extra-articular tenodesis (LET). However, hardware prominence, footprint size, and irritation are documented issues. Knotless all-suture anchors (ASA) are a promising alternative that mitigate these issues. However, there is a paucity of studies comparing the performance of various onlay techniques. The study objective was to compare the biomechanical behavior of LET using ASA to SLS and BSA under simulated anterolateral forces. The hypothesis was that ASA would demonstrate comparable fixation strength to SLS and BSA with comparable survival rates under cyclic loading.

Methods

Human iliotibial band (ITB) grafts were harvested, whipstitched, and fixed onto fresh-frozen porcine femurs using ASA, SLS, or BSA (n=6/group). Each femur was placed in a custom fixture at the base of an electromechanical testing machine, oriented at 60° of flexion with ITB grafts parallel to the load axis, simulating a worst-case scenario. Specimens were pre-tensioned for 10 minutes at 20 N; afterward, specimens were cyclically loaded through the following load ranges for 100 cycles each at 0.5 Hz: 10-50 N, 10-75 N, 10-100 N, and 10-125 N. Final load to failure was performed at 25 mm/min. Five millimeters of displacement was determined as the threshold for clinical failure and survivorship analysis. Biomechanical outcomes included cyclic displacement (mm), survivorship (%), ultimate load to failure (N), and mode of failure. Statistical analyses (P<0.05) included one-way analysis of variance (ANOVA) for cyclic displacement and ultimate load outcomes.

Results

Final cyclic displacement values were 4.25 ± 0.28 mm, 3.94 ± 0.71 mm, and 8.14 ± 1.68 mm for ASA, SLS, and BSA, respectively. No significant differences in cyclic displacement were found between ASA and SLS within each load range, whereas significant differences were found in each load range between BSA and both ASA and SLS (P<0.05). Survivorship was 100% for ASA, 83% for SLS, and 0% for BSA. The ultimate loads were 257 ± 40 N, 300 ± 47 N, and 205 ± 24 N for ASA, SLS, and BSA, respectively; only SLS and BSA were significantly different (P=0.002). All failure loads exceeded the anterolateral ligament’s failure load of 175 N for a relative comparison of adequate strength in the anterolateral compartment. Failure modes included implant failure (2/6) and graft failure (4/6) for ASA, graft failure (6/6) for SLS, and implant failure (5/6) and graft failure (1/6) for BSA.

Conclusion

All-suture anchor onlay fixation demonstrated comparable displacement to SLS and significantly lower displacement to BSA with greater survival during cyclic loading. ASA had comparable failure loading, with all groups exceeding the native anterolateral ligament failure load.

Clinical Relevance: All-suture anchors are a biomechanically viable alternative to spiked staples and biocomposite suture anchors for LET onlay fixation, potentially mitigating complications associated with conventional techniques.