Screw fixation of Grade III slipped capital femoral epiphysis.

From 1987 to 1992, 161 children were treated at The Children's Hospital of Philadelphia for slipped capital femoral epiphysis. Of these, 23 patients (23 hips) had Grade III slips (> 50%). Fixation was achieved by 1 or 2 screws in all patients. Twenty-one of 23 patients were available for followup (average followup, 2.8 years). Four slips were acute, 11 were acute-on-chronic, and 6 were chronic. At the most recent followup, radiographs were taken and a Harris Hip Score was assigned for each patient. Stabilization without progression of slip at followup was achieved in all patients. Screw placement was satisfactory per the criteria of Stambough in all patients. Four children (19%) had major complications: Three (1 acute slip and 2 acute-on-chronic slips) had avascular necrosis of the femoral head; One (chronic slip) had chondrolysis. There were no immediate postoperative complications. The mean Harris Hip Score for these 4 patients was 85 points, versus a mean score of 94 points for all 21 patients. Chronic Grade III slipped capital femoral epiphysis can be treated safely and effectively by screw fixation. Five of 6 patients had satisfactory results; the only exception had evidence of chondrolysis preoperatively. Acute and acute-on-chronic Grade III slipped capital femoral epiphyses treated with screw fixation are less predictable. In 15 patients, reduction occurred in 9 hips despite deliberate avoidance of forceful manipulative maneuvers. Avascular necrosis developed in 3 (33%) of these 9 hips. Reduction of the acute component of the slip during screw fixation, whether deliberate or not, indicates gross instability. It is hypothesized that avascular necrosis may be associated with injury to the epiphyseal vasculature occurring at the time of the acute slip.