Comparison of Surgical Outcomes Between a Triplane Proximal Femoral Osteotomy and the Modified Dunn Procedure for Stable, Moderate to Severe Slipped Capital Femoral Epiphysis

BACKGROUND: Recent studies have demonstrated the intra-articular cartilage and labral damage that can occur from the proximal femoral cam-like deformity of a moderate to severe slipped capital femoral epiphysis (SCFE). The approach to treating this deformity in a symptomatic Loder stable hip is controversial. The purpose of this study was to compare radiographic outcomes, complication rates, and revision rates between Imhauser type triplane proximal femoral osteotomy (TPFO) and the modified Dunn procedure (MDP). METHODS: Twenty-six subjects with minimum 1-year follow-up were included (12 treated with a TPFO, and 14 treated with the MDP). A chart review was performed to capture data related to complications, revision procedures, surgical time, and body mass index. Radiographs were measured preoperatively and at final follow-up to evaluate epiphyseal-slip angle, neck-shaft angle, articular surface to trochanter distance, and medial proximal femoral angle. RESULTS: Surgical time was shorter for the TPFO group (150.0±57.4 min) compared with the MDP group (203.8±30 min) (P=0.005). All preoperative and postoperative radiographic measures were similar between the 2 groups except postoperative neck-shaft angle, which was significantly less in the TPFO group (129.7±8.6 vs. 140.9±9.4 degrees) (P=0.005). There were no cases of femoral head avascular necrosis (AVN) in the TPFO group. The modified Dunn group had a 29% AVN rate (P=0.1). The overall complication rate was similar between the TPFO (33%) and modified Dunn (36%) groups (P=1.0) and the reoperation rate was slightly greater in the TPFO group (33%) as compared with the modified Dunn group (21%) (P=0.67). CONCLUSIONS: The complex 3-dimensional proximal femoral deformity of a moderate to severe SCFE can be difficult to treat with relatively high complication/reoperation rates observed in both TPFO and MDP groups. All 4 instances of AVN in this study of stable slips, however, were in the MDP group. As this can be a devastating complication leading to early total hip arthroplasty, we advise against the MDP in stable SCFE patients. LEVEL OF EVIDENCE: Level III-retrospective comparative study.