Page 30 - Slipped Capital Femoral Epiphysis Pathogenetic and Clinical aspects

Chapter 2
different anatomical levels of the proximal femur in stable and unstable slips. Most osteotomies described in literature are discussed here.
Corrective osteotomy through the physis.
A corrective osteotomy through the physis such as the Dunn or Fish osteotomy is perfect for the reconstruction of the anatomy, but has a high risk of complications occurring like avascular necrosis and fixation failure [61, 69, 143]. Alshryda et al. [6] compared retrospectively a group of moderate and severe SCFE cases, one group treated by in situ screw fixation with no reduction and another with Fish osteotomy. They claim that both the groups showed equal numbers of patients suffering from AVN (around 30%), and they concluded that using a Fish osteotomy was preferable for the better anatomical position and the AVN was caused by the vascular damage and not by the osteotomy.
Ganz (2011) [34] introduced the technically more demanding method of surgical dislocation and open reduction of the slipped epiphysis (modified Dunn). This technique has until now only a few users. By extending the retinacular flap to preserve the vascular supply to the femoral head containing the primary perfusion and by dislocation of the femoral head for the osteoplasty, Ganz claims to see less complications of AVN of the femoral head. Even so, apart from it being technically demanding, it is possible that uncertainty about long-term prognosis and the increased AVN rate if performed by less experienced surgeons, are other factors limiting its use [7, 33, 48, 65, 75, 77, 120, 128, 131, 137, 163]. Novais found superior results with the modified Dunn procedure in comparison with the in situ percutaneous screw fixation for severe SCFE [94]. Anderson [8] performed a subcapital femoral osteotomy in the chronic slips after fusion of the growth plate and describes two out of 12 hips with AVN postoperatively. Ten out of 12 hip joints showed acetabular hyaline cartilage lesions which were caused by repetitive mechanical abrasion of the prominent metaphysis against the anterior rim of the acetabulum. The average time after pinning in situ for this procedure was 29 months. He furthermore states that this procedure carries out a significant risk of major complications. Souder et al. [132] advises only to perform the Ganz/modified Dunn in unstable slips. The rate of AVN is similar in this osteotomy compared to the in situ epiphysiodesis. In stable slips, a higher risk of AVN is found (20% Ganz versus 0% in situ pinning).
Concluding: results of performing a corrective subcapital osteotomy appears to be dependent on the experience of the surgeon. If a subcapital osteotomy is performed the risk of AVN should be taken into account.
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