Treatment of Unstable Slipped Capital Epiphysis Via the Modified Dunn Procedure

Background: The modified Dunn procedure has been shown to be safe and effective in treating unstable slipped capital femoral epiphysis (SCFE). We present a consecutive series of unstable SCFE managed by a single surgeon with a focus on timing of surgical intervention, postoperative complications, and radiographic results.

Methods: Thirty-one consecutive unstable SCFEs were treated. Demographics, presentation time to time of operation, surgical times, and complications were recorded. Bilateral hip radiographs at latest follow-up were utilized to record slip angle, α angle, greater trochanteric height, and femoral neck length.

Results: Thirty-one consecutive hips in 30 patients were reviewed: 15 males (50%) and 15 females (50%), average age 12.37 years (range, 8.75 to 14.8 y), 20 left hips (65%) and 11 right hips (35%). Mean follow-up was 27.9 months (range, 1 to 82 mo). Time from presentation to intervention averaged 13.9 hours (range, 2.17 to 23.4 h). Two patients (6%) developed avascular necrosis at average 19 weeks postoperative. Three patients (10%) developed mild heterotopic ossification requiring no treatment. Two patients (6%) required removal of symptomatic hardware. One patient had hardware failure and in no patients was nonunion, delayed union, or postoperative hip subluxation/dislocation seen. Three patients (10%) presented with bilateral, stable SCFE requiring contralateral in situ pinning. Five patients (16%) had sequential SCFE requiring treatment with 1 patient having an acute, unstable SCFE 10 months after the previous realignment. Mean postoperative slip angle measured 2.5 degrees (range, +19 to -9.4 degrees) (SD, 7.2), α angle 47.43 degrees (range, 34 to 64 degrees) (SD, 7.49), greater trochanteric height averaged 3.5 mm below the center of femoral head (-17.5 to +25 mm), and mean femoral neck length difference measured -7.75 mm (range, -1.8 to -18.6 mm).

Conclusions: A single surgeon series of unstable SCFEs treated by a modified Dunn procedure showed a 6% incidence of avascular necrosis and low complication rates at latest follow-up. Radiographs showed restoration of the slip angle, α angle, femoral neck length, and greater trochanteric height. This series reveals the safety and effectiveness of the modified Dunn procedure for unstable SCFE.

Level Of Evidence: Level III-retrospective review.