RADIOGRAPHIC CHARACTERISTICS OF HIPS AT RISK FOR SLIPPED CAPITAL FEMORAL EPIPHYSIS

Abstract

Slipped capital femoral epiphysis is an important orthopaedic problem of early adolescence. Many hypotheses about its etiology have been proposed; still the underlying mechanisms are not clearly understood. The aim of our paper is to examine radiographic characteristics of hips at risk for slipped capital epiphysis.

Two groups of hips were compared: a group of 100 asymptomatic hips contralateral to the slipped ones and a group of 70 age- and gender-matched healthy hips. The hips contralateral to the slipped ones were assumed to have identical morphology to the preslip-page morphology of the slipped hips. In each hip the following radiographic parameters were measured: the inter-hip distance, the femoral neck length/width, the pelvic height, the pelvic width, the femoral head radius, the coordinates of the abductor muscles trochanteric attachment, the inclination of the femoral epiphyseal growth plate, the femoral neck-shaft angle and the Wiberg center-edge angle.

Subjects with hips at risk for slipping had significantly higher body weight (590 vs. 500 N; p < 0.001), larger diameter of the femoral neck (38.6 vs 37.3 mm; p = 0.027), higher (138.9 vs. 134.6 mm; p = 0.022) and wider pelvis (53.8 vs. 48.7 mm; p < 0.001) and more laterally placed abductor muscles trochanteric attachment. There were no significant differences in the inter-hip distance, the femoral head radius, the femoral neck length and the femoral neck-shaft angle angle. Hips contralateral to the slipped ones had a more vertically inclined physeal angle (55.4 vs. 63.2 degrees; p < 0.001) in comparison to the healthy hips. The Wiberg centre-edge angle of the hips contralateral to the slipped ones was on average 7% larger from the healthy group (34.7 vs. 32.2 degrees; p = 0.003).

Children with hips at risk for slipping had larger pelvices and femora with more vertically inclined femoral epiphyseal growth plate. In addition, one cannot overlook the significant difference in the body weight between the age- and gender-matched groups of our study, confirming previous findings on the role of body weight in SCFE. It is therefore possible that anatomical changes may be a downstream effect of bone remodelling caused by altered loading during growth and development. This may suggest that the predisposition of the hip to slipping occurs earlier in the patient’s lifetime and that targeted radiographic examinations in obese individuals could reveal changes in pelvic geometry even before adolescence. Considering the high rates of bilateral involvement, our results could be used to predict the need for preventive fixation of asymptomatic hips after the capital femoral epiphysis has slipped in the contralateral hip.