Displaced humeral head after intramedullary nailing for proximal humeral fracture is associated with worse short-term outcomes-a multicenter TRON study.

Background: In recent years, complex and unstable proximal humeral fractures (PHFs) are treated with intramedullary nails (IMNs) in the elderly; however, the postoperative radiographic findings related to the clinical outcome are not clear. This study evaluated the association of clinical outcomes with the radiographic findings of PHFs treated with IMNs. Methods: We collected data of patients aged >60 years with PHFs treated with IMNs from 2015 to 2019 in 13 associated centers' database (named TRON). We excluded patients lost to follow-up of <6 months postoperatively (PO6M). We evaluated clinical outcomes with the University of California at Los Angeles (UCLA) score at PO6M and defined a score of <27 as poor. We assessed the radiographic findings on the anteroposterior view of the humeral head postoperatively, and each radiographic finding such as humeral head height (HHH), head shaft angle, and cranialization of the greater tuberosity was divided into two groups: poor and good. Factors associated with poor UCLA at PO6M were extracted by logistic regression analysis, and the factors were divided into two groups (poor and good) and matched for age, sex, and fracture type. The UCLA score at PO6M between the groups was examined by the Mann-Whitney U test, and the significance level was set at 0.05. The minimal clinical important difference in the UCLA score was set 2 points. Results: The study included 243 patients (mean age, 76 years; range, 60-95 years). The mean follow-up period was 12 months (range, 6-56 months). The correlation coefficients indicated that there was either no or only a weak correlation between HHH, head shaft angle, and cranialization of the greater tuberosity. A poor HHH (HHH <0 or >10 mm) was extracted as a factor associated with a poor UCLA score at PO6M by logistic regression analysis (odds ratio: 5.78, 95% confidence interval = 1.2-27.7, Conclusion: We revealed that the HHH was an independent risk factor for poor short-term outcomes. There was a significant difference in the UCLA score between groups divided by the HHH in cases treated with IMNs. The HHH can be used intraoperatively or postoperatively as a reliable parameter to predict clinical outcomes in PHFs treated with IMNs.