Biomechanical impact of repair of the posterior band of the inferior glenohumeral ligament on anterior stabilization of the shoulder with a large glenoid bone defect

Background

Anterior glenohumeral dislocation usually results in capsuloligamentous lesions and the most common repair consists in reattachment of the anterior band of the inferior glenohumeral ligament (IGHL) to the glenoid. But it appears that reattachment of the posterior band (PB) of the IGHL to the glenoid is also important, particularly when there is an anterior glenoid bone loss. The aim of this biomechanical study was to analyze the effect of such a complementary repair of the IGHL PB compared to an isolated anterior repair, in an unstable shoulder with anterior glenoid bone defect.

Methods

Six fresh-frozen cadaveric shoulders were tested intact, after creating a 20% glenoid bone defect and anterior and posterior injuries of the IGHL, after anterior repair and finally after anterior and posterior repairs. Shoulders were placed at 90° of humerothoracic elevation in scapular plane and 60° of external rotation. Joint stability was analyzed by applying an anteroinferior loading and measuring three-dimensional humeral head displacements. Maximal range of external rotation was also measured.

Results

A lesion to the PB is needed to produce high instabilities in anteroinferior direction and a complementary repair of the PB increased the stability of the glenohumeral joint compared to an isolated anterior repair. The 2 repairs did not produce any deficit in external rotation compared to intact situation.

Conclusion

In the present testing conditions, repair of the PB of the IGHL increased shoulder stability when compared to isolated anterior repair, even when there was a 20% anterior glenoid bone loss.