Summary

This study evaluates the effectiveness of ALCOT compared to Latarjet in the setting of anterior instability with a deficient labrum. It proposes, and biomechanically validates, a novel surgical technique for labral reconstruction that may be used by surgeons to treat patients with anterior instability.

Abstract

Introduction

Labral reconstruction has been proposed as an alternative for anterior instability. A new technique called Anterior Labral Circumferential Onlay Technique (ALCOT) was developed, which reconstructs the labrum using the long head of the biceps tendon (LHBT). The purpose of this study was to biomechanically evaluate the efficacy of the ALCOT to stabilize the shoulder joint against anterior dislocation in the setting of a deficient labrum with no glenoid bone loss.

Methods

Ten fresh-frozen cadaveric shoulders were tested in 5 consecutive states using a 6-degrees-of-freedom robotic arm: (1) Native, (2) Capsular Repair, (3) Labral Tear (4) ALCOT (5) Latarjet. For the ALCOT, the biceps tendon was shortened at the distal portion and pulled into the joint. Three knotless all suture anchors were placed at 3, 4:30 and 6 o’clock position on the glenoid rim, and the biceps tendon was secured with suture anchors using mattress stitches to the anterior rim of the glenoid. In the native state, each specimen underwent an initial test to determine the appropriate amount of anterior and inferior displacement for future tests. In this test, a 50N compressive load was maintained while an 80N force was applied in the sagittal plane at a 45° angle between the anterior and inferior axes. The corresponding anterior and inferior displacements were recorded. Then, in each state including native, a dislocation test was performed. In this test, a 50N compressive load was maintained while the joint was driven in position control to the previously recorded positions on the anterior and inferior axes. The amount of force needed to displace the shoulder and the lateral displacement of the humeral head were recorded throughout the motion. Higher lateral translation was considered more stable, because it corresponded to a larger obstacle to overcome during the dislocation

Results

No significant differences were found between the native and capsular repair states. Compared to native, the labral tear significantly decreased the lateral translation of the humeral head during dislocation from 6.5mm to 5.4mm (p<0.001) and decreased the force ratio from 1.8 to 1.1 (p=0.002), corresponding to a decrease from 90N to 55N at 50N of compressive load. The ALCOT restored these values to 6.4 mm and 1.4, respectively, showing no significant difference from native. The Latarjet restored the force ratio to 1.3 (not significant from native) but failed to restore lateral translation with a value of 5.6 mm (p=0.003 from Native, not significantly different from the labral tear).

Discussion

The ALCOT is a novel technique for labral reconstruction that can be considered as a treatment option for anterior instability in the setting of a deficient labrum. Compared to the Latarjet technique, the ALCOT involves less morbidity and represents a more anatomic glenoid surface by replacing the labrum without changing the bony morphology. In this study, the ALCOT also showed superior stabilization by restoring native force ratio and lateral humerus translation. Further research is necessary to clinically validate this technique, and possibly to expand indications to small degrees of glenoid bone loss.