The biomechanical effect of injury and repair of the inferior glenohumeral ligament on glenohumeral stability: Contribution of the posterior band

Abstract Background Many surgical procedures are proposed to manage shoulder instability with recurrent dislocation but there is still a high rate of failure or complications. Repairs are often limited to anterior part of inferior glenohumeral ligament but some authors are reporting better clinical results if its posterior band is also repaired. This biomechanical study aimed to investigate the impact of a supplementary posterior injury compared with an isolated anterior injury and to analyze the contribution of a posterior repair of the inferior glenohumeral ligament compared with an isolated anterior repair. Methods Six fresh-frozen cadaveric shoulders were tested intact and after both anterior and posterior injuries and repairs of the inferior glenohumeral ligament. Shoulders were placed at 90° of humerothoracic elevation in scapular plane and 60° of external rotation. Joint stability was analyzed by successively applying anterior, posterior, inferior and superior glenohumeral displacements and measuring the resulting forces or by applying an anteroinferior loading and measuring three-dimensional head displacements. Maximal range of external rotation was also measured. Findings Combined anterior and posterior injuries of the inferior glenohumeral ligament were necessary to obtain significant instabilities in anterior and inferior directions. A complementary repair of the posterior band improved the biomechanical stability of the glenohumeral joint compared to an isolated anterior repair when anterior and posterior bands are injured. No reduction of external rotation was observed after repairs compared to intact condition. Interpretation These results show the biomechanical interest of this surgical procedure and contribute to document its relevance in clinical practice.