Safely Reducing the Incidence of Contralateral Slipped Capital Femoral Epiphysis: Results of a Prospectively Implemented Prophylactic Fixation Protocol Using the Posterior Sloping Angle.

BACKGROUND: Bilateral slipped capital femoral epiphysis (SCFE) is common. The management of the contralateral hip in unilateral SCFE remains controversial. The aim of this study was to report on the clinical outcomes using a posterior sloping angle (PSA) threshold of 14.5 degrees for prophylactic fixation in preventing contralateral SCFE. METHODS: Having previously established through a retrospective study that PSA was predictive of future slip, the authors put in place a protocol where patients with unilateral SCFE who had a PSA ≥14.5 degrees on the contralateral side were offered prophylactic fixation. Those with unilateral SCFE presenting between January 2008 and December 2018 with a minimum of 12-month follow-up were included. Patients with renal or endocrine disorders were excluded. Primary outcomes were the number of slips prevented, the number needed to treat, and the complication rate. RESULTS: Of the 219 patients who were included, 114 (52.1%) underwent prophylactic fixation.A PSA threshold of 14.5 degrees prevented 77% of subsequent slips with a number needed to treat of 2.4 in our population. There were no cases of chondrolysis, avascular necrosis, or periprosthetic fracture associated with prophylactic pinning. CONCLUSIONS: Prophylactic fixation using a PSA of 14.5 degrees is safe, decreases unnecessary intervention, and reduces 77% of subsequent SCFE. The PSA can increase over time and the authors recommend that the protocol be applied for the duration of follow-up. LEVEL OF EVIDENCE: Level III.