Treatment of Slipped Capital Femoral Epiphysis with a Modified Dunn Procedure

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Background:Surgical procedures with use of traditional techniques to reposition the proximal femoral epiphysis in the treatment of slipped capital femoral epiphysis are associated with a high rate of femoral head osteonecrosis. Therefore, most surgeons advocate in situ fixation of the slipped epiphysis with acceptance of any persistent deformity in the proximal part of the femur. This residual deformity can lead to secondary osteoarthritis resulting from femoroacetabular cam impingement.Methods:We retrospectively assessed the cases of twenty-three patients with slipped capital femoral epiphysis after surgical correction with a modified Dunn procedure, an approach that included surgical hip dislocation. The study reviewed the clinical status and radiographs made at the time of surgery, as well as the intraoperative findings. At a minimum follow-up of twenty-four months after surgery, the motion of the treated hip was compared with the motion of the contralateral hip, and the radiographic findings related to the anatomy of the femoral head-neck junction, as well as signs of early osteoarthritis or osteonecrosis, were evaluated.Results:Twenty-one patients had excellent clinical and radiographic outcomes with respect to hip function and radiographic parameters. Two patients who developed severe osteoarthritis and osteonecrosis had a poor outcome. The mean slip angle of the femoral head of 47.6° preoperatively was corrected to a normal value of 4.6° (p < 0.0001). The mean flexion and internal rotation postoperatively were 107.3° and 37.8°, respectively. The mean range of motion of the treated hips was not significantly different (p > 0.05) from that of the normal, contralateral hips. Of the eight hips that were considered unstable in the intraoperative clinical assessment, six had been considered stable preoperatively.Conclusions:The treatment of slipped capital femoral epiphysis with the modified Dunn procedure allows the restoration of more normal proximal femoral anatomy by complete correction of the slip angle, such that probability of secondary osteoarthritis and femoroacetabular cam impingement may be minimized. The complication rate from this procedure in our series was low, even in the treatment of unstable slipped capital femoral epiphysis, compared with alternative procedures described in the literature for fixation of slipped capital femoral epiphysis.Level of Evidence:Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.

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