Glenoid bone resorption after Bankart repair: finite element analysis of postoperative stress distribution of the glenoid.

ABSTRACT

BACKGROUND: There are various modifications of the Bankart repair, and postoperative changes to the glenoid morphology after the repair are reported. Among the various procedures performed, a decrease in the lateral glenoid diameter might be related to the surgery that involves removal of the articular cartilage and repair of the labrum-anterior inferior glenohumeral ligament complex on the glenoid surface. This is in contrast to cases without significant bony Bankart lesions that are not on the edge of the glenoid. Thus, this study aimed to compare glenoid rim stress after Bankart repair using 2 methods of finite element analysis: a method of removing the anteroinferior cartilage and repairing the glenohumeral ligament complex on the glenoid and a method of preserving the cartilage and repairing the glenohumeral ligament complex on the glenoid edge. METHODS: Five preoperative computed tomography scans of patients with traumatic anterior instability who underwent arthroscopic Bankart repair were used. Two models simulating different surgical procedures were created as follows in model G, a 5-mm-thick cartilage on the glenoid rim was removed between 2 and 7 o'clock, and the glenohumeral ligament complex was repaired on the medial edge of the glenoid bone where the cartilage was removed. In model E, the cartilage on the glenoid rim was not removed, and the glenohumeral ligament complex was repaired on the glenoid edge. The load stresses on the anteroinferior area of the glenoid after Bankart repair with models G and E were measured using finite element analysis. RESULTS: The stress on the glenoid at 3-4 o'clock was 3.16 MPa in model G and 6.42 MPa in model E (P = .043). The stress at 4-5 o'clock was 1.68 MPa in model G and 4.53 MPa in model E (P = .043). The stress at 5-6 o'clock was 2.26 MPa in model G and 3.93 MPa in model E (P = .043). CONCLUSION: Significantly lower load stresses were observed at the anteroinferior rim of the glenoid in model G than in model E.