Head-shaft angle is a risk factor for hip displacement in children with cerebral palsy

Abstract

Background and purpose Hip dislocation in children with cerebral palsy (CP) is a common and severe problem. The Swedish follow-up program for CP (CPUP) includes standardized monitoring of the hips. Migration percentage (MP) is a widely accepted measure of hip displacement. Coxa valga and valgus of the femoral head in relation to the femoral neck can be measured as the head-shaft angle (HSA). We assessed HSA as a risk factor for hip displacement in CP.Patients and methods We analyzed radiographs of children within CPUP from selected regions of Sweden. Inclusion criteria were children with Gross Motor Function Classification System (GMFCS) levels III–V, MP of < 40% in both hips at the first radiograph, and a follow-up period of 5 years or until development of MP > 40% of either hip within 5 years. Risk ratio between children who differed in HSA by 1 degree was calculated and corrected for age, MP, and GMFCS level using multiple Poisson regression.Results 145 children (73 boys) with a mean age of 3.5 (0.6–9.7) years at the initial radiograph were included. 51 children developed hip displacement whereas 94 children maintained a MP of < 40%. The risk ratio for hip displacement was 1.05 (p < 0.001; 95% CI 1.02–1.08). When comparing 2 children of the same age, GMFCS level, and MP, a 10-degree difference in HSA results in a 1.6-times higher risk of hip displacement in the child with the higher HSA.Interpretation A high HSA appears to be a risk factor for hip displacement in children with CP.

Is head–shaft angle a valuable continuous risk factor for hip migration in cerebral palsy?

“…The mean HSA in our study was 161.7°, which was lower than 166° reported by Hermanson et al [15]. The mean age at first radiograph was also higher in our study (8.8, range 3–18) compared to Hermanson et al (3.5, range 0.6–9.7).…”

“…The measured NSA has a predictable error, which potentially prevents its use as another predictor of hip migration. The HSA incorporates the position of the head compared to the neck and is less influenced by femoral anteversion [13, 15, 25]. …”

“…Hermanson et al [15] assessed the HSA as a risk factor for hip displacement in 145 children with CP. The risk ratio for developing hip displacement independently of age and GMFCS was determined.…”

“…This relationship is increased in children with cerebral palsy and in hips requiring surgical correction [13]. The prognostic value of the HSA in children with CP has recently been investigated and it was suggested to be a predictor for hip displacement [14, 15]. …”

Evaluación del seguimiento radiográfico para desplazamiento de cadera en pacientes con parálisis cerebral en el Centro Hospitalario Pereira Rossell

“…Muchos pacientes con PC también se presentan con coxa valga, con una cabeza femoral con valgo aumentado en relación con el cuello femoral. Estas deformidades se presentan en combinación y se pueden medir con el ángulo cérvico-diafisiario (ACD), ángulo que se ha demostrado que aumenta en los niños con PC y que ha demostrado ser un factor de riesgo válido para el desplazamiento de la cadera en esta cohorte de pacientes (6) . Existen formas de tratamiento conservador para prevenir la migración de cadera, entre las que destacan terapia física, férulas (aparatos ortopédicos), toxina botulínica, marcos de abducción y sillas moldeadas especiales, con efectividad limitada, logrando solo retrasar la aparición de esta complicación (7) .…”