Classification and Analysis of Attritional Glenoid Bone Loss in Recurrent Anterior Shoulder Instability

Abstract

Proper recognition and treatment of glenoid bone loss (GBL) is important for successful management of anterior shoulder instability. Although GBL has been thoroughly described in the literature, there is also a fragment of bone that is usually displaced and often undergoes attrition that has been little described. Thus, the purposes of this study include (1) to evaluate ABL of the glenoid fragment in recurrent anterior shoulder instability and (2) correlate ABL with clinical history, fragment size and radiographic findings. GBL was evaluated on 3-dimensional (3D) computed topography (CT) en face view, and measured as percent loss. The bone fragment size was measured and attrition of the fragment was determined by evaluating the amount remaining relative to the initial defect; patients were stratified into minimal (<34%), moderate (34-67%) and severe (>67%) attritional loss groups. Clinical history and demographics were correlated to ABL, and comparison of GBL and ABL was performed. The overall median percent GBL was 15.3% (IQR, 9.9% - 20.0%) with a mean (SD) percent GBL of 16.5% (9.0%). Study participants had a corresponding median percent ABL of 75.8% (IQR, 53.8% - 95.7%) and a mean (SD) percent ABL of 72.0% (24.4%). A total of 61.2% of patients (n=85) exhibited severe ABL, while 30% had moderate ABL and 8.6% had minimal ABL. The total time of instability was significantly associated with percent attritional bone loss (p<0.05). This study highlights that GBL, in most patients with recurrent anterior instability, presents with extensive attrition of the bone fragment independent of initial glenoid bone loss; therefore, surgeons should be cognizant that the remaining bone fragment is unable to reconstitute glenoid bone stock. In addition, there was more attritional bone loss in patients with a longer duration of instability symptoms, indicating need for incorporating symptom duration in determining proper management.