Inferior subluxation of humeral head after osteosynthesis for greater tuberosity fracture

BACKGROUND: Inferior subluxation of the humeral head is frequently observed immediately after surgery for proximal humerus fractures; however, the incidence and risk factors of inferior subluxation after osteosynthesis for isolated greater tuberosity fractures remain unsolved. Additionally, the postoperative course of inferior subluxation has not been elucidated. The purpose of the present study is to identify the predictors for the occurrence of postoperative inferior subluxation by multivariate analysis and investigate the postoperative shift of inferior subluxation and its effect on surgical outcomes. METHODS: We retrospectively identified 68 patients who underwent surgery for isolated greater tuberosity fractures. The dependent variable was the inferior subluxation at 1 week postoperatively. The explanatory variables were age, sex, affected side of the shoulder, body mass index, history of smoking, local osteoporosis, time period to surgery, axillary nerve injury, inferior subluxation before surgery, fracture dislocation, surgical approach, surgical method, operative time, amount of blood loss, and postoperative drainage. Baseline variables that were statistically significant in the univariate analyses were included in the logistic regression analysis. The patients were further categorized into two groups according to the presence of inferior shoulder subluxation exhibited 1 week postoperatively: patients with inferior subluxation (+ IS group) and patients without inferior subluxation (− IS group). We compared the incidence of postoperative complications between the two groups. RESULTS: Of 68 patients, 17 (25.0%) had inferior shoulder subluxation observed 1 week postoperatively. Multivariate analysis showed that long operative time was a risk factor for postoperative subluxation (odds ratio = 1.03; P = 0.030). In all cases, inferior subluxation disappeared within 3 months of surgery. No significant difference in complication rate was observed between the + IS and − IS groups. CONCLUSIONS: The present study provides novel information regarding postoperative inferior subluxation of fractures of the greater tuberosity. Inferior subluxation occurred in 25% of patients immediately after surgery. Long operative time contributes to the onset of postoperative inferior subluxation; however, this was temporary in all cases and had no significant effect on the surgical outcomes. Level of Evidence: Level III.