Complications after modified Dunn osteotomy for the treatment of adolescent slipped capital femoral epiphysis.

BACKGROUND: Modified Dunn osteotomy has gained popularity over the past decade in the treatment of moderate to severe adolescent slipped capital femoral epiphysis. The purpose of this study was to retrospectively evaluate a consecutive series of adolescent slipped capital femoral epiphysis patients treated with the modified Dunn procedure at a single institution. We analyze the indications for the procedure as well as the complications after surgical treatment. METHODS: Forty-three adolescent patients (18 boys and 25 girls) were treated with the modified Dunn procedure at our institution between September 2001 and August 2012. The average follow-up for this cohort was 2.6 years (range, 1 to 8 y). Complications were graded according to the modified Dindo-Clavien classification. RESULTS: Twenty-six patients (60%) had an unstable injury with an inability to ambulate with our without crutches. Seventeen patients (40%) had an acute injury with duration of symptoms <3 weeks. Thirty-seven patients (86%) had a severe slip based on a Southwick slip angle of >50 degrees. Twenty-two complications occurred in 16 patients (37%) in this cohort. Fifteen revision procedures were performed for femoral head avascular necrosis, fixation failure with deformity progression, or postoperative hip dislocation. Two patients developed end-stage degenerative joint disease and severe femoral head avascular necrosis and were referred for a total hip arthroplasty. CONCLUSIONS: The complication rate in this series is higher than most previous reports. This may be in part because of the fact that as a tertiary referral center our patient population was more complex. However, we identified a clear inverse relationship between surgeon-volume and patient-outcomes. On the basis of our results we have modified our practice. A high-volume surgeon must be present during each modified Dunn procedure, and only patients that have sustained an acute severe (>50 degrees) epiphyseal displacement with mild chronic remodeling of the metaphysis that can be addressed within 24 hours of the slip may be treated with the modified Dunn technique. LEVEL OF EVIDENCE: Level IV-therapeutic study.