Influence of gait analysis on decision-marketing for lower extremity surgery

Proximal femoral geometry in cerebral palsy: a population-based cross-sectional study

I ROBIN MBBS A,B,C, F DOBSON PHD A,B,C, R BAKER PHD A, P SELBER MD A, H K GRAHAM MD A,B

  1. 1. Hugh Williamson Gait Lasboratory, Royal Children’s Hospital;
  2. 2. The University of Melbourne,
  3. 3. The Murdoch Childrens Research Institute, Melbourne, Australia

Background: Proximal femoral deformity in the transverse (increased femaoral neck anteversion [FNA] and coronal planes (increased neck shaft angle [NSA] or `coax valga’) are common in children with cerebral palsy (CP), contributing to hip instability and ambulation difficulties. The prevalence and significance of these deformities have not been studied in a population-based cohort to our knowledge. Hip instability was examined in these deformities via migration percentage (MP).

Design: Large, population-based cross-sectional study.

Participants: Children with a confirmed diagnosis of CP born within a 3-year period were identified from a statewide register with high levels of ascertainment and accuracy. Inclusion criteria were: FNA measurement by experienced physical therapists using a reliable, standardized clinical technique (trochanteric palpation test [TPAT]0, good quality anteroposterior pelvis x-ray, and well documented motor type, topographical distribution, and Gross Motor Function Classification System (GMFCS) level.

Method: Each child’s unique identifying number was used to obtain clinical (movement disorder, topographical distribution, GMFCS levels, hip rotation range, and FNA) and radiological data (NSA and MP) held in either a motion analysis laboratory or hip surveillance database. NSA was measured from an anteroposterior pelvis x-ray with the hips internally rotated by the FNA amount suggested clinically or during fluoroscopic screening of the hip with a guide wire in the centre of the femoral neck.
Linear regression analyses were performed for FNA, NSA, and MP according to GMFCS.

Results: Two hundred and ninety-two children  were eligible for the study; results are presented in Table C:1. Mean FNA was increased in all GMFCS levels (p<0.001). The lowest measurements were at GMFCS Levels I and II; GMFCS Levels III, IV, and V were uniformly high (p<0.001). Neck shaft angle was found to increase sequentially from GMFCS Levels I to V (p<0.001).

Conclusions: 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. This information is highly relevant to understanding the origin and management of these deformities. 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, coax 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.

 
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