High Survivorship and Little Osteoarthritis at 10-year Followup in SCFE Patients Treated With a Modified Dunn Procedure.

BACKGROUND: The modified Dunn procedure has the potential to restore the anatomy in hips with slipped capital femoral epiphyses (SCFE) while protecting the blood supply to the femoral head and minimizing secondary impingement deformities. However, there is controversy about the risks associated with the procedure and mid- to long-term data on clinical outcomes, reoperations, and complications are sparse. QUESTIONS/PURPOSES: Among patients treated with a modified Dunn procedure for SCFE, we report on (1) hip pain and function as measured by the Merle d'Aubigné and Postel score, Drehmann sign, anterior impingement test, limp, and ROM; (2) the cumulative survivorship at minimum 10-year followup with endpoints of osteoarthritis (OA) progression (at least one Tönnis grade), subsequent THA, or a Merle d'Aubigné and Postel score < 15; (3) radiographic anatomy of the proximal femur measured by slip angle, α angle, Klein line, and sphericity index; and (4) the risk of subsequent surgery and complications.
METHODS: Between 1998 and 2005, all patients who presented to our institution with SCFE were treated with a modified Dunn procedure; this approach was applied regardless of whether the slips were mild or severe, acute or chronic, and all were considered potentially eligible here. Of the 43 patients (43 hips) thus treated during that time, 42 (98%) were available for a minimum 10-year followup (mean, 12 years; range, 10-17 years) and complete radiographic and clinical followup was available on 38 hips (88%). The mean age of the patients was 13 years (range, 9-18 years). Ten hips (23%) presented with a mild, 27 hips (63%) with a moderate, and six hips (14%) with a severe slip angle. Pain and function were measured using the Merle d'Aubigné and Postel score, limp, ROM, and the presence of a positive anterior impingement test or Drehmann sign. Cumulative survivorship was calculated according to the method of Kaplan-Meier with three defined endpoints: (1) progression by at least one grade of OA according to Tönnis; (2) subsequent THA; or (3) a Merle d'Aubigné and Postel score < 15. Radiographic anatomy was assessed with the slip angle, Klein line, α angle, and sphericity index.
RESULTS: The Merle d'Aubigné and Postel score improved at the latest followup from 13 ± 2 (7-14) to 17 ± 1 (14-18; p < 0.001), the prevalence of limp decreased from 47% (18 of 38 hips) to 0% (none in 38 hips; p < 0.001), the prevalence of a positive Drehmann sign decreased from 50% (nine of 18 hips) to 0% (none in 38 hips; p < 0.001), and both flexion and internal rotation improved meaningfully. Cumulative survivorship was 93% at 10 years (95% confidence interval, 85%-100%). Radiographic anatomy improved, but secondary impingement deformities remained in some patients, and secondary surgical procedures included nine hips (21%) with screw removal and six hips (14%) undergoing open procedures for impingement deformities. Complications occurred in four hips (9%) and no hips demonstrated avascular necrosis on plain radiographs.
CONCLUSIONS: In this series, the modified Dunn procedure largely corrected slip deformities with little apparent risk of progression to avascular necrosis or THA and high hip scores at 10 years. However, secondary impingement deformities persisted in some hips and of those some underwent further surgical corrections. LEVEL OF EVIDENCE: Level IV, therapeutic study.