Head-shaft angle measurement in children with cerebral palsy

It has been observed in children with cerebral palsy (CP) that the femoral head rests in a valgus position as compared to the proximal neck and/or shaft. The purpose of this study was to compare the head-shaft angle (HSA) as a measure of femoral head valgus in children with CP (group 1) with a subset of children with CP who have more significant hip subluxation (group 2, as demonstrated by the need for surgery to correct the deformity), with age-matched (group 3) and historical controls.

There were a total of 39 patients (70 hips), 15 patients in group 1, 10 in group 2, and 14 in group 3. The HSA was measured as described by Southwick (Southwick WO. Osteotomy of the lesser trochanter for slipped capital femoral epiphysis. J Bone Joint Surg Am. 1967;49A:803-835). Interrater and intrarater reliabilities and the variation of these measures with rotation were assessed.

The mean HSA in group 1 was 160.8 degrees; group 2, 170.3 degrees; group 3, 152.5 degrees; and historical control, 146.7 degrees. The difference was statistically significant between groups 1 and 2 and between both CP groups and the control groups. Intrarater and interrater reliabilities were found to be low, and variation with rotation was found to be minimal.

This study demonstrates that HSA is greater in children with CP than in typically developing children and that this is more pronounced in children with CP who are at risk for eventual subluxation. Evaluation of the HSA may be prudent in children with CP.