Redefining “Critical” Bone Loss in Shoulder Instability: Functional Outcomes Worsen With “Subcritical” Bone Loss

Background: Glenoid bone loss is a common finding in association with anterior shoulder instability. This loss has been identified as a predictor of failure after operative stabilization procedures. Historically, 20% to 25% has been accepted as the “critical” cutoff where glenoid bone loss should be addressed in a primary procedure. Few data are available, however, on lesser, “subcritical” amounts of bone loss (below the 20%-25% range) on functional outcomes and failure rates after primary arthroscopic stabilization for shoulder instability. Purpose: To evaluate the effect of glenoid bone loss, especially in subcritical bone loss (below the 20%-25% range), on outcomes assessments and redislocation rates after an isolated arthroscopic Bankart repair for anterior shoulder instability. Study Design: Cohort study; Level of evidence, 3. Methods: Subjects were 72 consecutive anterior instability patients (73 shoulders) who underwent isolated anterior arthroscopic labral repair at a single military institution by 1 of 3 sports medicine fellowship-trained orthopaedic surgeons. Data were collected on demographics, the Western Ontario Shoulder Instability (WOSI) score, Single Assessment Numeric Evaluation (SANE) score, and failure rates. Failure was defined as recurrent dislocation. Glenoid bone loss was calculated via a standardized technique on preoperative imaging. The average bone loss across the group was calculated, and patients were divided into quartiles based on the percentage of glenoid bone loss. Outcomes were analyzed for the entire cohort, between the quartiles, and within each quartile. Outcomes were then further stratified between those sustaining a recurrence versus those who remained stable. Results: The mean age at surgery was 26.3 years (range, 20-42 years), and the mean follow-up was 48.3 months (range, 23-58 months). The cohort was divided into quartiles based on bone loss. Quartile 1 (n = 18) had a mean bone loss of 2.8% (range, 0%-7.1%), quartile 2 (n = 19) had 10.4% (range, 7.3%-13.5%), quartile 3 (n = 18) had 16.1% (range, 13.5%-19.8%), and quartile 4 (n = 18) had 24.5% (range, 20.0%-35.5%). The overall mean WOSI score was 756.8 (range, 0-2097). The mean WOSI score correlated with SANE scores and worsened as bone loss increased in each quartile. There were significant differences (P < .05) between quartile 1 (mean WOSI/SANE, 383.3/62.1) and quartile 2 (mean, 594.0/65.2), between quartile 2 and quartile 3 (mean, 839.5/52.0), and between quart