The Posterior Active Subluxation Sign for Posterior Glenoid Bone Loss: A Retrospective Case Series

INTRODUCTION: Diagnosis of posterior shoulder instability is made primarily through a combination of history and physical examination. Several examination maneuvers have been described to diagnose instability, but have not been described to identify clinically meaningful posterior glenoid bone loss (pGBL) that would enable surgeons to plan for glenoid augmentation procedures. Our aim was to report a clinical sign that suggests the presence of clinically significant pGBL in patients with posterior shoulder instability. MATERIALS AND METHODS: In this retrospective study, we reviewed all patients who underwent posterior shoulder stabilization procedures by two military surgeons that had a positive posterior active subluxation sign (PASS) preoperatively. There were no exclusion criteria. The PASS is positive if the humeral head subluxates posteriorly into the void from pGBL with active forward flexion from 60° to 90° and cannot be flexed beyond 90° until the humeral head is relocated actively or manually. Clinical and surgical history was collected. Imaging was reviewed to measure preoperative acromial tilt, glenoid version, and pGBL. RESULTS: Eleven patients were included for analysis: 9 who underwent arthroscopic posterior glenoid augmentations and 2 who underwent arthroscopic posterior labral repairs. For shoulders in this series, mean pGBL was 17.9 ± 8.1%, glenoid version was 11.2 ± 5.1° of retroversion, and acromial tilt was 75.3 ± 8.1°. CONCLUSIONS: Preliminary results suggest the PASS can be used as a clinical screening tool for pGBL and potential indication for bone block augmentation. Further standardized, prospective study is needed to validate and determine the reliability of this clinical sign and to define the relative contribution of scapular morphologic features. LEVEL OF EVIDENCE: Level IV, Case Series.