The deltoid tuberosity index predicts intraoperative fracture risk in shoulder arthroplasty

Abstract

BackgroundWhen intraoperative fracture of the humerus during primary shoulder arthroplasty occurs, it can have significant clinical implications. To date, there are no described radiographic parameters to preoperatively assess risk of intraoperative fracture. The purpose of the current study was to determine if the deltoid tuberosity index (DTI), a validated tool for radiographic assessment of proximal humerus bone mineral density, correlates with risk of intraoperative humerus fracture during primary shoulder arthroplasty. MethodsA multicenter retrospective matched cohort study was performed utilizing patient data from two geographically diverse high-volume health systems. Intraoperative humerus fractures during primary shoulder arthroplasty were identified and matched 3:1 with a nonfracture cohort based on age, sex, body mass index, and type of arthroplasty surgery. DTIs were measured on preoperative anteroposterior radiographs in a blinded fashion. Additional data collected included American Society of Anesthesiologists score, preoperative diagnosis of osteoporosis, and various descriptive fracture variables. The chi-square test and independent samples t-test were used to analyze categorical and continuous variables, respectively. ResultsEighteen intraoperative humerus fractures were identified and matched with 54 nonfracture primary shoulder arthroplasty cases. The two cohorts did not significantly differ in age, sex, body mass index, type of arthroplasty surgery, mean American Society of Anesthesiologists score, or preoperative osteoporosis diagnosis. The mean DTI of the fracture cohort was significantly lower than that of the nonfracture cohort (1.34 vs. 1.46, P = .0018). A DTI value less than 1.44 was significantly associated with an increased risk of intraoperative humerus fracture (odds ratio = 19.6, 95% confidence interval = 2.4-155.6, P < .0001). Fractures most commonly occurred in female patients (83%), in reverse shoulder arthroplasty (89%), and with use of press-fit systems (72%). ConclusionThe DTI is a simple and broadly applicable tool for assessing a patient’s proximal humerus bone quality preoperatively. We found that a DTI less than 1.44 correlates with an increased risk of intraoperative humerus fracture during primary shoulder arthroplasty. This study provides radiographic parameters for preoperatively assessing a patient’s risk of intraoperative humeral fracture during primary shoulder arthroplasty.