Fixation in slipped capital femoral epiphysis avoiding femoral-acetabular impingement

BACKGROUND The appropriate treatment in mild slipped capital femoral epiphysis (SCFE) should not only prevent further slipping of the epiphysis but also address potential femoroacetabular impingement by restoring the anatomy of the proximal femur. The aim of this study was to quantify length of the remodeling phase mediated by growth of the femoral neck, after treatment of SCFE with a screw designed to prevent premature closure of the physis and provide stability. METHODS Between 2001 and 2011, 38 patients with unilateral mild SCFE were treated by fixation in situ using a modified screw which does not cause premature physeal arrest. Twenty-four patients were investigated for clinical and radiological evidence of femoroacetabular impingement immediately after surgery, at 6- and 12-month follow-ups. Statistical analysis was performed comparing measurements of neck length and the α angle of the affected and contralateral side. RESULTS Mean α angle immediately after pinning was 56.2 ± 10.6° on the anteroposterior view and 91.4 ± 8.2° on the lateral view. These measurements significantly improved at 6 months post-op to 48.9 ± 5.4° on the anteroposterior view and 51.2 ± 6.5° on the lateral view (p < 0.0001). At 12 months from surgery, AP view α angle was 43.0 ± 2.8° (p < 0.0001) and lateral view was 44.2 ± 4.1° (p < 0.0001). We observed a similar growth rate and speed of the femoral neck of both the affected and unaffected sides during the first year of treatment. The clinical results in all patients were rated as excellent. CONCLUSION Our data supports the use of a surgical technique that allows residual growth of the femoral neck following mild SCFE and permits restoration of the anatomy of the proximal femur while avoiding development of femoroacetabular impingement following mild SCFE.