In patients with Duchenne Muscular Dystrophy (DMD), height measurement is essential to assess growth, nutrition, kidney and lung function, and medication dosages. Over time, height measurements become unreliable given weakness, spinal deformities, contractures, and discomfort. Standardized equations that estimate standing height based on segmental measurements were developed for patients with cerebral palsy and those without neuromuscular disease. There is little evidence which of these is most accurate in DMD boys.
From a quality improvement perspective, we sought to determine which of five equations (four standardized in healthy children and one in children with cerebral palsy) may be most useful in estimating the standing height in a single DMD clinic.
Patients with DMD had their standing height/length taken with up to three segmental measurements (ulnar, tibial, and arm span length). Using the five equations, these measurements estimated standing height and were compared with the standing height/length measured at that same visit. The average difference between the estimated and standing/lying height was calculated for each equation.
The Miller and Koreska ulnar equation differed from measured height by an average of 6.9cm (N=28). The Gauld tibial equation differed by an average of 2.9cm (N=28). The Gauld ulnar equation differed by an average of 1.8cm (N=28). The Gauld arm span equation differed by an average of 0.4cm (N=26). The Stevenson tibial equation differed by an average of 12.2cm (N=28).
In our pilot clinic sample, the three Gauld equations were closest to standing height/length in our patients, with the arm span equation performing best. They were also the only equations to incorporate age at measurement. The equation for patients with cerebral palsy did not seem useful in this population. More multi-center studies are needed to determine which equation is most accurate and reliable at predicting height.