Maximum Principal Strains in the Glenohumeral Capsule During a Clinical Exam: A Validated Finite Element Model

The shoulder is the most frequently dislocated joint in the body, with 80% of dislocations occurring in the anterior direction [1]. One of the primary contributors to anterior shoulder stability is the glenohumeral capsule. Up to 23% of repaired shoulders redislocate following arthroscopic surgical techniques [2], and the function of the capsule in response to external loading remains unclear. Information on the strain distribution throughout the capsule during joint motion can help lead to more effective pre- and post-surgical diagnostics for capsular pathologies. One common diagnostic examination is the apprehension test, in which anterior loading is applied to the humerus at 60° of glenohumeral abduction with varying amounts of external rotation. The inferior glenohumeral ligament (IGHL), composed of three regions, the anterior band (AB-IGHL), axillary pouch, and posterior band (PB-IGHL), has been shown to be the primary region of the capsule to provide stability in this joint position [3]. The objective of this study was to determine the maximum principal strains in each region of the IGHL during an apprehension test at 0, 30, and 60° of external rotation, using a validated subject-specific model of the glenohumeral joint. The strain distribution may help elucidate the function of these regions in providing stability and transferring load between the humerus and scapula.