Risk factors for nonunion in 337 displaced midshaft clavicular fractures treated with Knowles pin fixation

Background: Clavicular fractures account for nearly 10 % of all fractures, and the majority of those fractures involve the midshaft. Historically, these fractures were treated nonoperatively; however, recent data suggest an increased risk of nonunion and symptomatic malunion for displaced, comminuted midshaft clavicular fractures treated conservatively. Surgical intervention via plate osteosynthesis or intramedullary fixation with pins, nails, or screws has been shown to reduce, but not eliminate, this risk. Identification of risk factors predictive of nonunion would improve the overall management of displaced, comminuted midshaft clavicular fractures. Methods: The medical records of 337 consecutive patients who underwent Knowles pin fixation and supplemental cerclage for the treatment of displaced, comminuted midshaft clavicular fractures between April 2007 and March 2009 were retrospectively reviewed. The records of the mechanism of injury, side of injury, Robinson fracture classification, presence of associated injuries, cerclage material, and patient-related variables, including diabetes mellitus, hypertension and smoking, were analyzed. Variables were assessed by univariate and multivariate analysis to identify those factors significantly associated with the development of fracture nonunion. Results: A total of 19 nonunions occurred. Increasing age and use of wire for supplemental cerclage fixation were significantly associated with an increased risk for fracture nonunion (p < 0.001). Although suggested as predictors of nonunion in other studies, female gender and fracture severity were not significantly associated with nonunion. Conclusions: Nonunion remains a significant complication in the treatment of displaced, comminuted midshaft clavicular fractures even with intramedullary fixation. Use of absorbable suture in place of wire for cerclage fixation and careful selection of treatment strategy in the elderly may reduce the risk for nonunion.