Modified Dunn Osteotomy for Moderate and Severe Slipped Capital Femoral Epiphysis - A retrospective study of thirty hips

Abstract

Background: Modified Dunn procedure has become popular for the treatment of severe cases of slipped capital femoral epiphysis (SCFE). We assessed the outcomes in a consecutive series of thirty Indian adolescents treated by the modified Dunn procedure.

Materials and methods: All patients treated by the modified Dunn procedure by a single senior Paediatric Orthopaedic surgeon over six years were retrospectively reviewed. Only moderate and severe slips undergoing modified Dunn procedure were included. Clinical records and radiographs were reviewed to obtain demographic information; to classify the slips by duration of symptoms, severity and physeal stability; and to assess the outcomes by Harris Hip Score, radiological changes and rate of complications.

Results: Thirty consecutive hips with 19 stable and 11 unstable slips were included. Mean age was 13.05 years, 25 boys and 5 girls; six were acute slips, six chronic and eighteen acute-on-chronic. There were 20 moderate and 10 severe slips. Slip angle correction was on average 43.63° ± 8.42° (p < 0.001). At a mean follow-up of 25.36 months, the slip angle averaged 9.9° ± 3.78°, and alpha angle was 33.63° ± 4.14. The average Harris Hip Score was 81.833 ± 7.12 points, with six excellent, 17 good, six fair and one poor result. Osteonecrosis occurred in two hips (6.6%). One hip had post-operative subluxation which was corrected.

Conclusion: This study adds to the evidence that the modified Dunn procedure is safe, reliable and reproducible. It should be the first choice for the treatment of moderate and severe SCFE.

Keywords: Capital realignment; Indian adolescents; Modified dunn procedure; Safe surgical dislocation; Slipped capital femoral epiphysis.

Fig. 1

Intra-operative photographs of modified Dunn osteotomy performed on a left hip. a Incision centered over greater trochanter. b Deep exposure, just prior to digastric osteotomy; star—greater trochanter, black triangle—vastus lateralis, blue triangle—abductors. c Extensile retinacular flaps raised (yellow arrow), Dunn osteotomy being planned (blue arrow). d Slip reduced, active bleeding seen from epiphysis after reduction (arrow head)

Fig. 2

A thirteen-year-old boy with right-sided, acute on chronic, stable slip. Pre-operative X-ray pelvis with both hip joints, a anteroposterior and b frog leg lateral views showing a moderate slip (52°). c Coronal, d transverse, and e three-dimensional reconstruction computerized tomography images prior to surgery. f and g Radiographs at 2.5-year follow-up after capital realignment using modified Dunn procedure (final slip angle 3°, alpha angle 26°)

Fig. 3

A thirteen-year-old boy operated for right-sided acute, unstable slip. X-ray pelvis with both hip joints a anteroposterior and b cross table lateral views at presentation. c Immediate post-operative anteroposterior radiograph showing subluxation. d Anteroposterior and e frog leg lateral radiographs at 18 months after revision surgery (removal of interposed capsular tissue and the trochanteric screws exchange). Note the concentric joint reduction and absence of AVN