Femoral neck-shaft angle changes based on the severity of neurologic impairment in children with cerebral palsy and spinal muscular atrophy

Introduction: The neck-shaft angle and head-shaft angle in children with varying levels of neurological disability were evaluated to define change over different ages.

Methods: Children aged 1-12 years with spastic cerebral palsy, spinal muscular atrophy types 1 and 2, or typical development were reviewed to evaluate the neck-shaft angle and head-shaft angle. Patients were divided into five groups: Gross Motor Function Classification System levels I and II, Gross Motor Function Classification System level III, Gross Motor Function Classification System levels IV and V, spinal muscular atrophy types 1 and 2, and typical development. A linear mixed model was utilized to evaluate neck-shaft angle and head-shaft angle.

Results: Data from 196 children (mean age 4.8 ± 4.5 years) were included. Gross Motor Function Classification System levels I and II: 22 children, 130 hip radiographs measured, neck-shaft angle 143.7 ± 7.4, and head-shaft angle 160.0 ± 7.1. Gross Motor Function Classification System level III: 8 children, 33 hips evaluated, neck-shaft angle 153.1 ± 4.3, and head-shaft angle 163.4 ± 4.2. Gross Motor Function Classification System levels IV and V: 30 children, 137 hip radiographs measured, neck-shaft angle 156.4 ± 5.6, and head-shaft angle 167.9 ± 6.8. Spinal muscular atrophy types 1 and 2: 32 children, 83 hip radiographs measured, neck-shaft angle 161.9 ± 9.7, and head-shaft angle 173.4 ± 7.4. Typical development: 104 children, 222 hip radiographs measured, neck-shaft angle 138.6 ± 7.0, and head-shaft angle 156.4 ± 5.9. There were significant statistical differences when comparing neck-shaft angle and head-shaft angle.

Conclusion: As children grow, neck-shaft angle and head-shaft angle tend to decrease in typical development and Gross Motor Function Classification System levels I and II groups. However, in low-tone (spinal muscular atrophy types 1 and 2) and high-tone groups (Gross Motor Function Classification System levels IV and V), neck-shaft angle and head-shaft angle tend to increase with age. In both low-tone and high-tone groups, coxa valga is observed. When evaluating the effect of proximal femur-guided growth, these defined normal growth patterns should be considered.

Level of evidence: Level III Retrospective comparative study.