Risk Factors for Avascular Necrosis After Femoral Neck Fractures in Children: 25 Cincinnati Cases and Meta-analysis of 360 Cases

PURPOSE: Avascular necrosis (AVN) is one of the most serious complications of femoral neck fractures in children. Variability in the reported rates of AVN and lack of statistical evidence has minimized the prognostic power of individual studies. The purpose of our study was to review our own cases as well as those from the literature in an effort to identify the risk factors for AVN. METHODS: We conducted a computerized search of medical records to identify all children with femoral neck fractures treated at our institution from 1980 to 2003. Records were reviewed to determine fracture type (Delbet type I to IV), displacement, age, treatment, and incidence of AVN. A structured search of PubMed was also performed to identify all reports published in English, on femoral neck fractures in children, from 1965 to 2003. Hand searches of major orthopedic journals and reference lists of publications identified additional cases. Of the 275 citations initially identified through our computerized search, 47 met the criteria for further evaluation. These citations were reviewed by 2 investigators, and data was abstracted from 20 reports that provided patient-level data and met our criteria for inclusion. RESULTS: Twenty-four patients with 25 femoral neck fractures from our institution were identified including 12 boys and 12 girls with an average age of 8 years (range 1.5 to 16). Over 300 patients who met our study criteria were also identified from the literature, and a total of 360 patients were included in the analysis. Fracture type, displacement, age, and treatment were all statistically significant independent predictors of AVN with P values <or=0.05. With logistic regression analysis, however, fracture type and age were identified as the only significant predictors of AVN. Older children were 1.14 times more likely to develop AVN for each year of increasing age. Type I to III fractures were 15, 6, and 4 times, respectively, more likely to develop AVN than type IV fractures. AVN rate by Delbet class was I=38%, II=28%, III=18%, and IV=5%. CONCLUSION AND SIGNIFICANCE: Although several factors may contribute to the development of AVN, our meta-analysis provides statistical evidence that fracture type and age are the most significant predictors.