Abstract:
This research aims to identify specific joint positions for standardizing physical examinations of the shoulder to improve the diagnosis of capsule pathology following anterior dislocation. The shoulder is the most frequently dislocated joint, with over 80% of dislocations occurring anteriorly. A major challenge in clinical practice is the lack of standardized joint positions during physical examinations, which can lead to inaccurate diagnoses of the location and extent of capsular pathology. These misdiagnoses have been linked to over 50% of redislocations and over 80% of cases of pain and loss of motion after surgery. To address this, two subject-specific finite element models of the glenohumeral joint were created from cadaveric data. The capsule was represented using an isotropic hyperelastic constitutive model. The models were validated by comparing predicted capsule strains to experimental data in clinically relevant positions. The models were then used to identify joint positions where the distribution of predicted capsule strain was highly correlated (r 2>0.7) between the two models. The study found that applying a 25 N anterior load at 60° of glenohumeral abduction and 10°–40° of external rotation resulted in correlated strain distributions. At external rotation angles of 20°–40°, the strains were significantly higher in the glenoid side of the anterior band of the inferior glenohumeral ligament. Based on these findings, the research suggests that standardizing physical examinations for anterior instability at joint positions with abduction and a mid-range of external rotation could help clinicians more accurately diagnose capsular pathology, potentially leading to improved surgical outcomes. This work lays the groundwork for further research to identify additional standardized positions for a more comprehensive diagnosis of the entire capsule.
