Aims. Our retrospective analysis reports the outcome of patients operated for slipped capital femoral epiphysis using the modified Dunn procedure. Results, complications, and the need for revision surgery are compared with the recent literature. Methods. We retrospectively evaluated 17 patients (18 hips) who underwent the modified Dunn procedure for the treatment of slipped capital femoral epiphysis. Outcome measurement included standardized scores. Clinical assessment included ambulation, leg length discrepancy, and hip mobility. Radiographically, the quality of epiphyseal reduction was evaluated using the Southwick and Alpha-angles. Avascular necrosis, heterotopic ossifications, and osteoarthritis were documented at follow-up. Results. At a mean follow-up of more than nine years, the mean modified Harris Hip score was 88.7 points, the Hip Disability and Osteoarthritis Outcome Score (HOOS) 87.4 , the Merle d’Aubigné Score 16.5 points, and the UCLA Activity Score 8.4. One patient developed a partial avascular necrosis of the femoral head, and one patient already had an avascular necrosis at the time of delayed diagnosis. Two hips developed osteoarthritic signs at 14 and 16 years after the index operation. Six patients needed a total of nine revision surgeries. One operation was needed for postoperative hip subluxation, one for secondary displacement and implant failure, two for late femoroacetabular impingement, one for femoroacetabular impingement of the opposite hip, and four for implant removal. Conclusion. Our series shows good results and is comparable to previous published studies. The modified Dunn procedure allows the anatomic repositioning of the slipped epiphysis. Long-term results with subjective and objective hip function are superior, avascular necrosis and development of osteoarthritis inferior to other reported treatment modalities. Nevertheless, the procedure is technically demanding and revision surgery for secondary femoroacetabular impingement and implant removal are frequent. Cite this article: 2020;1-4:80–87

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. However, there is controversy about the risks associated with the procedure especially in the most severe capital slips. Therefore, we report on (1) clinical outcome, (2) the cumulative survivorship with endpoints AVN and/or OA progression and (3) radiographic anatomy of the proximal femur at followup in patients treated with a modified Dunn procedure for severe SCFE. We performed a retrospective analysis involving 46 hips of 46 patients treated with a modified Dunn procedure for severe SCFE (slip angle >60°) between 1999 and 2016. Followup averaged 8 years, (range 1–17) with 2 patients lost to followup after one year. The mean age was 13 years (range 9–19 years). Mean preoperative slip angle was 64° (range 60–90) and 14 out of 46 hips (30%) presented with unstable slips. Clinical scores and PROMs were evaluated and the hips were followed standard x-rays. Cumulative survivorship (Kaplan-Meier) with three defined endpoints: (1) AVN; (2) progression by at least one OA grade according to Tönnis; (3) non-preserved hip joint. (1)Mean Harris Hip score (HHS) was 93 points (66–100) and mean Hip Disability and Osteoarthritis Outcome Score (HOOS) was 90 points (67–100) at last followup. (2)Cumulative survivorship was 93% at 10-year followup. Three hips reached an endpoint. Two hips (4%) had AVN, one of them underwent hip arthrodesis. One hip had OA progression. (3)Postoperative slip angle was 7° (1–16). Alpha angle on axial radiograph was 39° (26–71) at followup. 41/44 hips (93%) had no OA (Tönnis 0). The modified Dunn procedure largely corrected slip deformities with low apparent risk of progression to avascular necrosis or osteoarthritis at mean 8-years followup. The AVN rate in severe and unstable (30%) capital slip was 4% (2 hips) with this procedure

Introduction. Hips following in-situ pinning for slipped capital femoral epiphysis (SCFE) have an altered morphology of the proximal femur with cam type deformity. This deformity can result in femoroacetabular impingement and early joint degeneration. The modified Dunn procedure allows to reorientate the slipped epiphysis to restore hip morphology and function. Objectives. To evaluate (1) hip pain and function, (2) 10-year survival rate and (3) subsequent surgeries and complications in hips undergoing modified Dunn procedure for SCFE. Methods. Between April 1998 and December 2005 we performed the modified Dunn procedure for 43 patients (43 hips) with SCFE. Twenty-five hips (58) presented with an acute or acute on chronic slip. The mean slip angle was 43° (range, 15° – 80°). A majority of 53% of procedures were performed in male patients and the mean age at operation was 13 years (10 – 19 years). We could followup all except one hip (followup of 5.5 year) for a minimum of 10 years (mean followup 13 [10 – 18 years]). We used the anterior impingement test to assess pain and the Merle d'Aubigné- ostel score to assess function. Survivorship calculation was performed using the method of Kaplan and Meier and any of the following factors as a definition of failure: radiographic evidence of worsening osteoarthritis (OA), or a Merle d'Aubigné-Postel score less than 15. Results. (1) The prevalence of a positive anterior impingement test decreased from 100% to 16% (p<0.001). The mean Merle d'Aubigné-Postel score improved from 13 (7 – 14) to 17 (14 – 18) at most recent followup (p<0.001). (2) Four hips (9%) showed progression of OA and three hips (7%) had a Merle d'Aubigné-Postel score of less than 15 at most recent followup. This resulted in a 93% survival rate at 10-year followup. (3) No hip developed avascular necrosis. Five hips (12%) had complications with reosteosynthesis due to screw breakage or nonunion. Another nine hips (21%) had subsequent surgeries including acetabular rim trimming / offset creation in 5 hips and screw removal in 4 hips. Conclusion. The modified Dunn procedure is a safe method to correct the morphology of the proximal femur in hips with SCFE. Ninety-free percent of the hips showed no progression of OA and a good clinical result at the 10-year followup. Twelve percent required revision surgery for complications all including screw breakage with nonunion of the greater trochanter

Tannast has recently shown that safe hip dislocation (SHD) for femoroacetabular impingement treatment does not result in atrophy and degeneration of periarticular hip muscles. In more complex procedures, such as relative neck lengthening for Perthes disease (PD) or modified Dunn procedure for slipped capital epiphysis (SCFE), minimus gluteus femoral insertion is detached to achieve enough mobility of osteotomized trochanter and to fix the latter more distally. Aim of this study was to evaluate MRI appearance of minimus and medius gluteus after relative neck lengthening. Patients treated with SHD and relative neck lengthening eventually associated to epiphyseal realignment for PD or SCFE treatment underwent magnetic resonance imaging (MRI) to study gluteus minimus (MI) and medius (ME) muscles. In the axial T1-weighted sequences, cross sectional area (CSA) and signal intensity were evaluated at acetabular roof level. Statistical comparison was made with the opposite healthy side. Fifteen patients underwent an MRI at an average of 59 months (SD=27.3) after surgery. Average ratio between gluteus minimus CSA (treated/healthy side) was 0.90 (SD=0.2): this reduction in volume was statistically significant (p=0.04) as well as the signal intensity (p=0.04). CSA and signal intensity of gluteus medius did not differ between two sides (respectively p=0.78 and p=0.30). In conclusion, gluteus medius appearance was not influenced by distal fixation of the trochanter. The minimus gluteus was reduced in volume as much as 10% in respect to healty side; increased signal intensity in MRI T1-weighted (fatty infiltration) was found in the minimus gluteus

The April 2014 Children’s orthopaedics Roundup³⁶⁰ looks at: urgent supracondylar fractures; rotational osteotomy for synostosis; predicting slip in paediatric forearm fractures; progressive lengthening of the digit is possible; treatment of SUFE with the Dunn osteotomy; and the best way to apply the eight-plate?.