Contralateral slip prediction in slipped capital femoral epiphysis: is bone age the answer?

Prophylactic pinning of an asymptomatic hip in Slipped Capital Femoral Epiphysis (SCFE) is controversial. Bone age has been used as a predictor of future contralateral slip risk and also in the decision making for prophylactic intervention. The efficacy of bone age at predicting a contralateral slip was tested in this study. Eighteen Caucasian children prospectively had bone age assessment using wrist and hand radiographs when presenting with a unilateral SCFE. After in situ fixation of the affected side prospective monitoring was performed at regular intervals in the outpatient department. Surgical intervention was undertaken if the contralateral hip was symptomatic. Three children (2 boys and 1 girl) went on to develop a contralateral slip at a mean of 20 months from initial presentation. Six children were deemed at risk of contralateral slip due to a bone age of > or = 12.5 years for boys and > or = 10.5 years for girls. Only one from this group developed a contralateral slip. The relative risk of proceeding to a contralateral slip when the bone age is below the designated values was 1 (95% confidence interval of 0.1118 to 8.95). The sensitivity and specificity were 33% and 66% respectively. The positive predictive value was 15% and the diagnostic efficiency was 61%. Although this is a small study, it would appear that delayed bone age by itself is not a good predictor of future contralateral slip. Routine prophylactic pinning is not justified based on bone age alone, with the risks of surgical fixation it carries. A prospective long term longitudinal study is required.