The aim of this study was to survey existing literature in order to identify all reported predictors associated with nonunion or symptomatic malunion in adult patients with displaced midshaft clavicle fractures treated non-operatively.

A systematic literature search in Medline was carried out in order to identify publications in English, reporting on predictors for nonunion and malunion in adults with displaced midshaft clavicle fractures. After applying inclusion and exclusion criteria, eight publications were included in this systematic review.

A total of 2,117 midshaft clavicle fractures were included in the eight publications. All publications reported on predictors for nonunion but none were found to report on predictors for malunion. The studies were characterized by different definitions for nonunion and symptomatic malunion if at all present. A total of 13 potential factors associated with nonunion were identified, six of these (displacement, comminution, shortening, age, gender and smoking) were reported as predictors for nonunion. Outcome definitions varied among the studies.

The included publications varied greatly in design, sample size, and quality. Based on the present literature most of the predictors were found to be of limited evidence, however displacement seems to be the most likely factor that can be used to predict for nonunion. Treating all clavicle fractures with displacement surgically would inevitably lead to overtreatment, which is why future studies need to focus on predictive factors in order to differentiate between patients that would benefit from surgery and those who would not.