Background: Reduction of unstable slipped capital epiphysis has a bad reputation, especially in severe slips. Treatment frequently causes avascular necrosis (AVN). This study analyzes the role of capsulotomy with evacuation of intraarticular fluid and gentle reduction done as an emergency procedure followed by fixation with unthreaded Kirschner wires (K-wires).
Methods: We treated 64 consecutive cases of unstable slips (37 boys and 27 girls) following the same protocol. Instability was recognized in those children who had experienced a fall or a stumble, followed by acute hip pain, with radiological evidence of capital femoral separation and ultrasonographic evidence of joint effusion. The protocol consisted of capsulotomy, evacuation of intraarticular effusion or hematoma, controlled gentle reduction, and fixation of the reduced physis by smooth K-wires. Surgery was done as an emergency procedure if possible within 24 hours after the onset of acute symptoms.
Results: There were 20 mild slips with slip angles less than 31 degrees, 24 moderate with slip angles between 31 and 50 degrees, 20 slips were severe with slip angles between 51 and 90 degrees. In 61 cases, reduction was successful without being followed by AVN. Three patients, 2 girls and 1 boy, developed partial AVN (4.7%). Two avascular necroses occurred in moderate slips, one in a severe slip, and none in the mild slips. The outcome of 60 patients (34 boys and 26 girls) with unstable slips could be evaluated clinically and radiographically with a mean follow-up of 4.9 years (range, 18 months-104 months). The Iowa hip score in these 60 cases reached an average of 94.5 points out of 100.
Conclusions: Open reduction and evacuation of intraarticular hemarthrosis or effusion detected by ultrasound and smooth K-wire fixation done as an emergency is a safe and reliable treatment option for unstable slips with a low AVN rate. The severity of the slip does not influence the rate of AVN and the outcome measured by the Iowa hip score.
Level of Evidence: Therapeutic, level IV.