Acetabular morphology in slipped capital femoral epiphysis: comparison at treatment onset and skeletal maturity.

PURPOSE

To investigate changes in acetabular morphology during the follow-up of slipped capital femoral epiphysis (SCFE) and search for factors associated with acetabular dysplasia at skeletal maturity.

METHODS

We evaluated 108 patients with unilateral SCFE (mean age at slip, 12.3 years sd 1.7) to skeletal maturity, with a minimum follow-up of two years (median 4.5 years; interquartile range 3.2 to 6.2). Acetabular parameters obtained from initial and most recent radiographs included the lateral centre-edge angle (LCEA), Tönnis angle (TA) and acetabular depth-width ratio (ADR). Acetabular dysplasia was considered for LCEA < 20° or TA > 10°. Femoral parameters consisted of the most recent head diameter, neck-shaft angle, neck length, articulotrochanteric distance and alpha angle.

RESULTS

At SCFE onset, the affected hip showed a slightly lower LCEA (26.4° sd 6.1° 27.3° sd 5.7°; p = 0.01) and ADR (330 sd 30 340 sd 30; p < 0.001) compared with the uninvolved hip. At final follow-up, the affected hip showed lower LCEA (24.5° sd 7.6° 28.8°sd 6.6°; p < 0.001) and ADR (330 sd 40 350 sd 40; p < 0.001), and TA was larger (5.5° sd 5.4° 2.3° sd 4.2°; p < 0.001) compared with the uninvolved hip. Acetabular dysplasia was observed in 27 (25%) of 108 hips with SCFE. Femoral head overgrowth, age at slip and SCFE severity were independent factors associated with acetabular dysplasia (p < 0.05).

CONCLUSION

Acetabular coverage and depth are not increased in SCFE, and the acetabular coverage tends to decrease up to skeletal maturity. A potential disturbance in the acetabular growth and remodelling exists mainly for young children with severe SCFE, and a potential for acetabular insufficiency may be observed at the diagnosis and follow-up of SCFE.

LEVEL OF EVIDENCE

Prognostic Level IV.