Free-gliding screw fixation in slipped capital femoral epiphysis: potentially growing im-plants for symptomatic and prophylactic pinning.

INTRODUCTION: In situ fixation is the gold standard for mild and moderate slipped capital femoral epiphysis (SCFE) cases. The condition is associated with a low percentage of avascular necrosis and chondrolysis.[1] The present study examines the postoperative femoral neck remodelling and implant elongation in cases of therapeutic and prophylactic in situ fixation using the free-gliding screw system.

AIM: The aim of our study was to assess the postoperative femoral neck growth and evaluate the biomechanical evolution and complication's rate for 19 therapeutic and 11 prophylactic in situ fixations with a free-gliding screw.

MATERIALS AND METHODS: We measured the preoperative and postoperative articulo-trochanteric distance (ATD), alpha angle (α angle) and screw elongation in symptomatic hips and in contralateral hips with prophylactic fixation. We compared the radiographic param-eters of 30 hips.

RESULTS: ATD remains approximately the same for symptomatic cases, whereas it increases for prophylactic fixated hip. Screw elongates in both group with statistically higher value for the prophylactic group. The alpha angle remains pathological in these cases with a mean value of 67.12±4.62°, but decreases for group II. Screw elongates by a mean value of 3.14±2.74 mm for group I and 6.78±8.81 mm for group II.

CONCLUSIONS: Prophylactic in situ fixation with free-gliding screws does not affect the proximal femoral growth (ATD), and does not decrease the alpha angle significantly. Screw elongates statistically in both groups, but more significantly for group II. For symptomatic hips, the in situ fixation allows the femoral neck to grow with ATD preserved, but significantly less than in group II. The alpha angle decreases but remains pathological.