This study aimed: (1) to determine the probability of and the amount of time needed to achieve fracture healing in children with displaced femoral neck fractures (FNFs) treated surgically; and (2) to determine which factors can affect both the probability of and the amount of time needed to achieve radiological fracture healing in those patients.

Pediatric FNFs require longer time to achieve union than previously reported.

We retrospectively reviewed the data of 177 children (mean age 10.5±3.9 years) with FNFs treated surgically. Risk factors, including age, sex, laterality, the mechanism of injury, the initial displacement severity, the type of fracture, the time to reduction, the reduction method, the fixation method and the reduction quality, were recorded. Furthermore, the presence of a comminuted medial or posterior cortex on anteroposterior (AP) or lateral radiographs was also recorded.

A total of 172 hips (97.2%) achieved radiological fracture healing during the follow-up period. Severe initial displacement, a comminuted cortex on the AP or lateral radiographs and poor reduction quality significantly increased the time needed to achieve radiological fracture healing (p<0.05). Cox regression analysis indicated that the cumulative probability of achieving fracture healing increased linearly during the first 6 months and then plateaued, with a monthly increase of less than 5%. The severity of initial displacement, presence/absence of comminution on the medial or posterior cortex, and reduction quality were factors influencing the probability of achieving fracture healing within the first 6 months after injury (p<0.05).

Radiological union of displaced pediatric FNFs treated surgically increases linearly during the first six month after surgery and then it tends to plateau. Risk factors for nonunion are severe initial displacement, poor reduction quality and the presence of comminuted medial or posterior cortex on AP or lateral radiographs; the same factors are associated with a longer time to achieve fracture healing.

III.