Risk factors for fracture-related infection after open reduction and internal fixation of proximal humerus fractures: A multicenter retrospective study of 496 fractures (TRON group study)

One of the complications of the surgical therapy for proximal humerus fractures is fracture-related infection (FRI). This multicenter study aimed to investigate the incidence of FRI and clarify the risk factors associated with FRI in patients receiving open reduction and internal fixation for proximal humerus fracture.Among 684 patients diagnosed as having proximal humerus fracture and who were treated by surgical therapy in 13 institutions (named TRON group) from 2015 through 2020, 496 patients (men, n = 134, women, n = 362; mean [SD] age, 68.5 [14.5] years; mean [SD] body mass index [BMI], 23.0 [4.4] kg/m2) were included as subjects. Excluded were 188 patients due to less than 12 month's follow-up, patients who underwent osteosynthesis using neither plate nor nail and those with open fracture. We extracted the following as risk factors of FRI: sex, BMI, smoking status, diabetes, glenohumeral fracture dislocation, fracture classification, approach, implant, waiting period, type of anesthesia, operative time and blood loss during surgery. We conducted logistic regression analysis to investigate the risk factors of FRI using these extracted items as explanatory variables and the presence or absence of FRI as the response variable.FRI occurred after surgery for proximal humerus fracture in 9 of the 496 patients (1.8%). The causative organism was methicillin-susceptible Staphylococcus aureus in 4 patients, Pseudomonas aeruginosa in one patient and Enterococcus faecalis in one patient. In the other 3 patients, causative organisms were not detected. The univariate analysis showed significant differences for present of glenohumeral fracture dislocation (p = 0.004). Logistic regression analysis showed glenohumeral fracture dislocation to be the significant explanatory factor for FRI (odds ratio 12.3, p = 0.0375).This study revealed an infection rate following open reduction and internal fixation of proximal humerus fracture of 1.8% (9 patients) and that Staphylococcus was the most frequent causative organism. Glenohumeral fracture dislocation is a significant risk for postoperative FRI.