Combined valgus derotation osteotomy and cervical osteoplasty for severely slipped capital femoral epiphysis: mechanical analysis and report preliminary results using compression screw fixation and early weight bearing.

Although considerable remodeling can occur in slipped capital femoral epiphysis, it is generally conceded that the severely-slipped epiphysis requires corrective osteotomy to restore adequate range of motion, and to prevent early degenerative changes. A study of artifically-created severe slips in cadaver specimens demonstrated that removal of the cervical prominence, as well as valgus-derotational osteotomy is necessary to restore good range of motion and provide a satisfactory weight-bearing surface. Clinical trial in 6 patients also demonstrated that the cervical prominence is a barrier to flexion, internal rotation, and abduction even after a valgus derotational osteotomy. The Watson-Jones approach afforded adequate exposure of the anterior femoral neck and head as well as the femoral shaft to allow excision of the cervical prominence, insertion of internal fixation, and adjustment of valgus and rotation under direct vision. The Richards compression screw proved to be ideal for fixation in the proper degree of valgus, and for allowing rotary alignment of the distal fragments. Early results were very good, and all patients had near-normal hip flexion, internal rotation, and abduction; and most were able to bear weight in the early postoperative period. The operation appears to offer a workable solution to the problem posed by the severly slipped capital femoral epiphysis, but more definitive conclusions must await the results of a larger series.