Glenohumeral Stability During External Rotation in Patients Treated With the Latarjet Procedure: A Two-Year Dynamic Radiostereometric Study.

The Latarjet procedure is widely used for anterior shoulder instability with glenoid bone loss, yet its influence on glenohumeral joint (GHJ) kinematics during functional movement remains unclear. This study evaluated GHJ kinematics during active external rotation compared with the contralateral shoulder preoperatively and at 1- and 2-year follow-up using dynamic radiostereometry (RSA) and CT-derived 3D bone models registered to the radiographs. Patient-reported outcomes were assessed using the Western Ontario Shoulder Instability Index (WOSI). Preoperatively, the injured shoulder showed a tendency toward a more anterior (up to 1.5 mm, CI -0.3-3.3) and inferior (up to 1.1 mm, CI -0.3-2.5) humeral head position. At 1 year postoperatively, the humeral head was more posterior (up to 1.8 mm, CI 0.8-2.9) and superior (4.0 mm, CI -4.1-12.1) compared with preoperatively, with an additional posterior shift at 2 years (1.5 mm, CI 0.4-2.6). Postoperative kinematics did not differ from the healthy shoulder. Contact area decreased preoperatively by up to 121.7 mm2 (CI 57.1-186.3) and increased by up to 110.8 mm2 (CI 42.3-179.3) at 2 years. WOSI improved from 55% (CI 49-61) preoperatively to 36% (CI 25-48) at 1 year and 27% (CI 17-36) at 2 years. The Latarjet procedure resulted in GHJ kinematics comparable to the healthy shoulder during external rotation. Postoperatively, kinematics shifted posteriorly and superiorly with improved WOSI scores over 2 years. Clinical Significance: Near-normal GHJ kinematics during external rotation are achieved within 2 years, supporting improved shoulder function in anterior instability following the Latarjet procedure.