In-line Pull-out Strength of Two Acetabular Fixation Methods for Ligamentum Teres Reconstruction of the Hip: A Cadaveric Study

Background:
Ligamentum teres reconstruction is an appropriate alternative in select cases of ligamentum teres full-thickness tears, resulting in of hip micro- or macro-instability. Graft fixation at the acetabular fossa is critical to achieving the best functional results.

Purpose:
To compare the pull-out strength of two different graft fixation methods used for ligamentum teres reconstruction of the hip.

Methods:
In seven cadaveric specimens, the acetabular socket was prepared after the native ligamentum teres was transected and the femoral head was removed. Seven separate tibialis anterior grafts were then prepared by suturing a running-locking #2 suture on each tail of the graft. Three specimens had fixation of the graft to the acetabulum using an adjustable cortical suspension suture-button; the remaining four were fixed to the acetabulum using a knotless suture anchor. Specimens were then mounted on a custom jig within a mechanical test frame to allow for the in-line pull of the graft-fixation construct. Following a 5-N preload, each specimen was loaded to failure at 0.5 mm/s. Stiffness and load to failure were measured for each specimen construct.

Results:
Suture button fixation had higher mean load to failure compared to the knotless anchor fixation method (438.1 ± 114.3 N vs. 195.9 ± 50.0 N, p = 0.01). There was no significant difference (p = 0.6) in mean stiffness between the two methods of fixation (24.5 ± 1.4 vs 26.5 ±23 5.8 N/mm).

Conclusion:
This cadaveric study examined differences in load to failure between two methods of graft fixation to the acetabulum that are commonly utilized in ligamentum teres reconstruction. The suture button fixation demonstrated greater load to failure compared to the knotless anchor fixation.