Using Multiple Anthropomorphic Measures to Estimate Height in Muscular Dystrophies and Its Impact on Lung Function

Background: An accurate height estimate is important for assessing pulmonary function, and body mass index. If a patient cannot stand, an accurate standing height cannot be directly measured. Knee-heel length, arm span, ulnar length, and tibial length have been studied in otherwise healthy populations as single measurements for height estimation.

Objective: To determine the relation of ulnar length, tibial length, arm span, and knee-heel length to standing height in children with neuromuscular diseases.

Methods: Children and adolescents with neuromuscular diseases were recruited for participation. Knee-heel length, ulnar length, tibial length, arm span, and standing height (in those who could stand) were measured. Height estimation models were built using multivariate regression with backward elimination with criteria to eliminate as p > 0.20. Our results were compared to other published height estimation models.

Results: We enrolled 28 children with a neuromuscular diagnosis who were able to stand. Models for standing height that combined arm span, ulnar length, and tibia length provided the best estimates, yielding an adjusted R square of 0.95 and a mean difference from measured height of 2.7 cm for a 5% difference in predicted forced vital capacity (FVC). Other models yielded a 5-7 cm difference between estimated and standing height for an 8.5%-12% difference in predicted FVC. We enrolled 30 children not able to stand. The mean ratios of anthropomorphic measures were similar in those who could not stand compared to those who could stand.

Conclusions: A model combining three measurements of arm span, ulnar length, and tibial length together provided the best height estimation for patients with neuromuscular disease. Final height estimation model: (arm span [cm] × 0.457) + (ulnar length [cm] × 1.292) + (tibial length [cm] × 0.902) + 17.745 = Standing Height.