2025 ISAKOS Congress in Munich, Germany

2025 ISAKOS Biennial Congress Paper


Adequate Failure Loads for Modified Lemaire Lateral Extra-Articular Tenodesis are Achieved with an Interference Screw, Staple, and Suture Anchor: A Biomechanical Study of Structural Properties

Luke V. Tollefson, BS, Edina, MN UNITED STATES
Evan Shoemaker, BA, Edina, MN UNITED STATES
Erik Slette, MD, Fargo, North Dakota UNITED STATES
Mitchell Carlson , MS, BME, Eagan, Minnesota UNITED STATES
Robert F. LaPrade, MD, PhD, Edina, MN UNITED STATES
Lars Engebretsen, MD, PhD, Oslo NORWAY
Gilbert Moatshe, MD, PhD, Oslo NORWAY
Andrew Geeslin, MD, Burlington, VT UNITED STATES

Twin Cities Orthopedics, Edina, MN, UNITED STATES

FDA Status Not Applicable

Summary

For LET fixation between an interference screw, staple, and suture anchor, all three femoral fixation methods achieved adequate failure loads, although the interference screw had a greater failure load than the suture anchor and there was no significant difference between these implants and the staple.

Abstract

Background

A lateral extra-articular tenodesis (LET) is increasingly being utilized to augment an anterior cruciate ligament (ACL) reconstruction because it has been shown to reduce the risk of post-reconstruction graft failure or recurrent rotatory instability. Various femoral fixation techniques are available including the use of an interference screw, a staple, or a suture anchor.

Purpose

The purpose of this study was to determine and compare the biomechanical properties of an LET graft when using an interference screw, a staple, or a suture anchor for the femoral fixation for a modified Lemaire LET. We hypothesized that there would be variable failure modes but no difference in failure load or stiffness between fixation methods.

Methods

Eighteen fresh frozen cadaveric knees were obtained and randomly assigned to undergo a modified Lemaire LET using either an interference screw, a staple, or a suture anchor for femoral fixation. The specimens included 4 bilateral male knees, 5 bilateral female knees. The mean age was 73.8 years (SD 15.4 years, range 40-87 years). The specimen underwent load-to-failure testing at 20 mm/min until graft failure. The maximum failure load, stiffness, and failure mode for each specimen were recorded. Statistical analysis was performed using one-way ANOVA and Tukey’s HSD to compare the failure load and stiffness for the 3 fixation methods.

Results

The average failure load was highest for the interference screw (252.7 ± 131.2 N), followed by the staple (151.8 ± 34.1 N), and the suture anchor (105.7 ± 16.4 N). There was a significant difference in failure load between the interference screw and the suture anchor (p = 0.015). There was no significant difference between the staple and the interference screw (p = 0.101) or the suture anchor (p = 0.577) (Figure 2).

The mean graft stiffness was highest for the 6 mm interference screw at 22.7 ± 12.5 N/mm (Range, 8.9-45.4), followed by the staple at 12.2 N/mm (Range, 6.6-17.1; SD, 3.6), and the suture anchor at 11.6 N/mm (Range, 4.8-27.7; SD, 8.7). There was no significant difference in graft stiffness across all fixation methods (p = 0.089) (Figure 3).

The failure modes varied between fixation method. For the interference screw, 3 grafts pulled out of the femoral tunnel (mean failure load: 157.4 N; mean stiffness: 16.6 N/m) and 3 grafts failed near the femoral fixation point (mean failure load: 347.9 N; mean stiffness: 28.8 N/m). For the staple fixation, 3 grafts pulled out from under the staple (mean failure load: 153.9 N; mean stiffness: 13.1 N/m) and 3 grafts tore at the staple-osseous fixation point (mean failure load: 149.8 N; mean stiffness: 11.4 N/m). For the suture anchor, all graft failure occurred due to the sutures ripping through the graft at the femoral fixation location (Table 1).

Conclusion

All three femoral fixation methods achieved adequate failure loads, although the interference screw had a greater failure load than the suture anchor and there was no significant difference between these implants and the staple. There were no significant differences in stiffness between the fixation methods.