AIM To assess the accuracy of skinfold equations in estimating percentage body fat in children with cerebral palsy (CP), compared with assessment of body fat from dual energy X-ray absorptiometry (DXA).METHOD Data were collected from 71 participants (30 females, 41 males) with CP (Gross Motor Function Classification System [GMFCS] levels I-V) between the ages of 8 and 18 years. Estimated percentage body fat was computed using established (Slaughter) equations based on the triceps and subscapular skinfolds. A linear model was fitted to assess the use of a simple correction to these equations for children with CP. RESULTSSlaughter's equations consistently underestimated percentage body fat (mean difference compared with DXA percentage body fat )9.6 ⁄ 100 [SD 6.2]; 95% confidence interval [CI] )11.0 to )8.1). New equations were developed in which a correction factor was added to the existing equations based on sex, race, GMFCS level, size, and pubertal status. These corrected equations for children with CP agree better with DXA (mean difference 0.2 ⁄ 100 [SD=4.8]; 95% CI )1.0 to 1.3) than existing equations.INTERPRETATION A simple correction factor to commonly used equations substantially improves the ability to estimate percentage body fat from two skinfold measures in children with CP.Although accurate assessment of nutritional status for children with cerebral palsy (CP) is important from clinical and research perspectives, physical impairments and growth differences hinder evaluation and interpretation in this population. Difficulties in measurement of stature arise from altered body posture and fixed contractures that interfere with reliable estimation of height or recumbent length. Equations that estimate height from segmental measures 1 have been developed and are widely used. Additionally, it is possible to use specialized chair scales or weigh a child along with a caregiver. 2 These modifications have allowed clinicians to obtain reliable measures of height and weight. Despite these improvements in measurement ability, clinicians continue to have challenges in interpreting growth and nutritional status in children with CP.Because children with CP often have malnutrition associated with short stature, simple measurements of weight and height are not adequate to identify nutritional abnormalities. Known alterations in body composition in malnourished children with CP include increased total body water, depleted fat and muscle stores, short stature, and decreased bone density. [3][4][5] Reliable measures of weight and height have allowed the use of weight-for-height centiles and body mass index (BMI), but the validity of these measures in assessing nutritional status in children with CP has been called into question. 3 Reliable and valid methods that are also quick and readily available are needed to estimate fat mass (as an indicator of nutritional status) for research and to guide clinical care for children with CP because of the constraints described above. Dual-energy X-ray absorptiometry (DXA) is one m...

Children with limited or no ability to ambulate frequently sustain fragility fractures. Joint contractures, scoliosis, hip dysplasia, and metallic implants often prevent reliable measures of bone mineral density (BMD) in the proximal femur and lumbar spine, where BMD is commonly measured. Further, the relevance of lumbar spine BMD to fracture risk in this population is questionable. In an effort to obtain bone density measures that are both technically feasible and clinically relevant, a technique was developed involving dual-energy X-ray absorptiometry (DXA) measures of the distal femur projected in the lateral plane. The purpose of this study is to test the hypothesis that these new measures of BMD correlate with fractures in children with limited or no ability to ambulate. The relationship between distal femur BMD Z-scores and fracture history was assessed in a cross-sectional study of 619 children aged 6 to 18 years with muscular dystrophy or moderate to severe cerebral palsy compiled from eight centers. There was a strong correlation between fracture history and BMD Z-scores in the distal femur; 35% to 42% of those with BMD Z-scores less than −5 had fractured compared with 13% to 15% of those with BMD Z-scores greater than −1. Risk ratios were 1.06 to 1.15 (95% confidence interval 1.04–1.22), meaning a 6% to 15% increased risk of fracture with each 1.0 decrease in BMD Z-score. In clinical practice, DXA measure of BMD in the distal femur is the technique of choice for the assessment of children with impaired mobility. © 2010 American Society for Bone and Mineral Research

Single anthropometric measures do not perform well in predicting percentage body fat in children with or without CP. Further work is needed to develop clinically useful and simple assessments that will predict percentage body fat and to determine the relation between percentage body fat and health to guide clinical practice.