Biomechanical Effect of Differential Tensioning on Suture-Augmented Ulnar Collateral Ligament Reconstruction of the Elbow

Abstract

Background:

Medial ulnar collateral ligament (mUCL) reconstructions are becoming increasingly prevalent among the overhand throwing population. Suture tape augmentation has the potential to provide biomechanical advantages over standard docking reconstruction. However, the optimal tensioning of the suture augmentation technique has not yet been evaluated.

Purpose:

To compare the subfailure biomechanical performance and graft strain of a standard docking mUCL reconstruction to an mUCL reconstruction using suture tape augmentation tensioned with 1 mm or 3 mm of laxity.

Study Design:

Controlled laboratory study.

Methods:

A total of 18 cadaveric elbows were dissected to the mUCL anterior band and biomechanically assessed via a valgus torque protocol to failure. Elbows were randomly assigned to be reconstructed via (1) a standard docking technique, (2) a suture-augmented reconstruction with 1-mm laxity, or (3) a suture-augmented reconstruction with 3-mm laxity. Reconstructed elbows were then subjected to the same loading protocol. Subfailure mechanical properties, failure mode, and mUCL/palmaris strain were assessed.

Results:

All reconstruction groups had decreased rotational stiffness, torque at 5° of angular rotation, and resilience compared with matched native controls. There were no differences in transition torque between groups. The failure mode of suture-augmented specimens was most often due to bone tunnel failure or reaching the maximum allowable angular displacement. In native controls or docking reconstructions, the primary failure mechanism was in the ligament or graft midsubstance. There were no significant differences in strain on the reconstructed or suture-augmented groups at any laxity compared with native controls.

Conclusion:

Suture augmentation results in similar subfailure joint biomechanical properties as the standard docking reconstruction procedure at both laxity levels in a cadaveric model. There are improvements in the failure mode of suture-augmented specimens compared with standard docking. Graft strain may be modestly reduced in the 1-mm laxity group compared with other reconstruction groups.

Clinical Relevance:

Suture augmentation at both 1-mm and 3-mm laxity appears to offer similar advantages in subfailure biomechanics to standard docking reconstruction of the mUCL, with some improvements associated with failure mode. Strain data suggest a potential avoidance of graft stress shielding when tensioning the suture augmentation to 3-mm laxity, which is not as apparent with 1-mm laxity.