The incidence of hip displacement in children with cerebral palsy is approximately 30% in large population based studies. The purpose of this study was to report the long-term effect of hip surgery on the incidence of hip displacement using a newly validated Cerebral Palsy (CP) hip classification. Retrospectively, a sub-group of 100 children who underwent surgery for hip displacement were identified from a large-population based cohort of children born with CP between January 1990 and December 1992. These children were followed to skeletal maturity and closure of their tri-radiate cartilage. All patients returned at maturity for clinical and radiographic examination, while caregivers completed the disease specific quality of life assessments. Patients were grouped according to motor disorder, topographical distribution and GMFCS. Radiographs were independently graded according to CP hip classification scheme to ensure reliability. Surgical Failures were defined as CP Grade > IV.Purpose
Method
Proximal femoral deformity is common in children with cerebral palsy (CP), contributing to hip instability and ambulation difficulties. This population-based cohort study investigates the prevalence and significance of these deformities in relation to Gross Motor Function Classification System (GMFCS) level. Children with a confirmed diagnosis of CP born within a three-year period were identified from a statewide register. Motor type, topographical distribution and GMFCS level were obtained from clinical notes. Neck Shaft Angle (NSA) and Migration Percentage (MP) were measured from an anteroposterior pelvis x-ray with the hips internally rotated. Measurement of FNA was by the Trochanteric Palpation Test (TPAT) or during fluoroscopic screening of the hip with a guide wire in the centre of the femoral neck. Linear regression analysis was performed for FNA, NSA and MP according to GMFCS level. 292 children were eligible. FNA was increased in all GMFCS levels. The lowest measurements were at GMFCS levels I and II p<0.001. GMFCS levels III, IV, and V were uniformly high p<0.001. Neck shaft angle increased sequentially from GMFCS levels I to V (p<0.001). This study confirms a very high prevalence of increased FNA in children with CP in all GMFCS levels. In contrast, NSA and MP progressed step-wise with GMFCS level. We propose that increased FNA in children with CP represents failure to remodel normal fetal alignment because of delay in ambulation and muscle imbalance across the hip joint. In contrast, coxa valga is an acquired deformity and is largely related to lack of weight bearing and functional ambulation. The high prevalence of both deformities at GMFCS levels IV and V explain the high rate of displacement in these hips and the need for proximal femoral realignment surgery in the prevention and management of hip displacement.
