Session VI - Pediatrics
Screw Placement in Slipped Capital Femoral Epiphysis: Is Good the Enemy of Better?
Purpose: The goal of dynamic screw fixation for the treatment of slipped upper femoral epiphysis (SUFE) is to achieve physeal stability, to prevent further slippage, and to avoid premature physeal closure. A single dynamic hip screw is the recommended method of fixation, with current practice favoring the placement of the screw in the center of the femoral head on both anteroposterior and lateral planes. The purpose of this study was to investigate the correlation between the different positions of the screw to the prevalence of late slippage, osteonecrosis (ON), and chondrolysis.
Methods: In a retrospective study, the clinical notes and radiographs of 38 consecutive patients (61 hips) who underwent single screw fixation for SUFE between 1995 and 1999 were evaluated. All measurements were made by the principle author to minimize interobserver variation. Parameters of investigation included the type and degree of the slip (classified according to the systems by Loder and Southwick respectively), the position of the screw in the femoral head, the time to epiphyseal closure, the type of screw (Richards 6.5 mm, AO 7.3 mm), and the radiologic signs of chondrolysis and ON.
Results: The cohort contained 14 girls and 24 boys. The mean time for follow-up was 39 months (range, 18 to 56 months). There were 16 acute slips, 18 chronic slips, and 10 acute on chronic slips. 17 slips were treated prophylactically. Mild slip was encountered in 39 hips, moderate in 4, and severe in 1 hip. The central-central position was only achieved in 31 of 61 hips and in 24 of 39 hips (61%) with mild SUFE. The position of the screw in the other quadrants of the femoral head was almost evenly distributed for the remaining 30 hips. The most significant results of the study were : (1) no significant difference between the time to epiphyseal closure and the position of the screw; and (2) no late slippage, ON, or chondrolysis was observed in the series.
Conclusion: Our results showed that the position of the screw, other than in the center of the femoral head, has the ability to provide physeal stability and has no correlation to the premature closure of the epiphysis and the risk of ON. Central-central positioning of the screw has the potential advantage of avoiding the risk of lateral epiphyseal vessel injuries and penetration of the hip. It therefore minimizes the risk of ON and chondrolysis. However, to achieve this position, several attempts may be required by the treating surgeon. Such attempts may carry the potential hazard of joint surface penetration and therefore increase the risk of ON and chondrolysis. We therefore recommend that other positions be accepted if the optimal central position was not initially achieved, especially for the treatment of mild SUFE. This can be important from a medicolegal standpoint because surgeons have been criticized for not achieving adequate results in negligence cases.