Methods: An IRB approved retrospective review identified 255 children with hip fractures treated at a single institution from 1983 to 2009. Children were excluded if they had metabolic bone disease, subtrochanteric or pathologic fractures, slipped capital femoral epiphysis, or less than 1 year follow-up. This left 43 patients with 44 fractures in our study. Factors analyzed included age, Delbet classification, displacement, time to reduction, reduction quality and type, and whether or not a decompression was performed. Two-sided Fisher’s Exact tests were used with p < 0.05 considered statistically significant.
Results: Of the 44 cases included in the study, 9 (20%) developed ON. The rate of ON for Delbet type I fractures was 50% (2/4), type II was 28% (5/18), type III was 8% (1/12), and type IV was 10% (1/10). Age greater than or equal to 11 years was the only statistically significant independent predictor of ON (p = 0.04). There were no significant differences of ON rates between those undergoing early (less than or equal to 12 hours) or late reduction or those with or without capsular decompression; however, sample sizes needed to achieve 80% power for these factors ranged from 480 to 680 cases. Further analysis of the age greater than or equal to 11 year subgroup also did not identify any significant predictors.
Conclusion: This is a relatively large case series of 44 femoral neck fractures with a relatively low ON rate of 20%. Of all variables analyzed, age greater than or equal to 11 years was the only significant independent predictor of ON (p = 0.04). A much larger case series is needed to determine whether other variables, such as time to reduction (early versus late), affect the rate of ON. This case series therefore adds to the literature and demonstrates the need for a national database to determine the best way to decrease the risk of developing ON following pediatric femoral neck fractures.