Agreement Between Actual Height and Estimated Height Using Segmental Limb Lengths for Individuals with Cerebral Palsy

The purpose of this study was to determine the agreement between actual height or segmental length and estimated height from segmental measures among individuals with cerebral palsy.

A convenience sample of 137 children and young adults with cerebral palsy (age 2-25 yrs) were recruited from a tertiary care center. Height, body mass, recumbent length, knee height, tibia length, and ulna length were measured. Estimated height was calculated using several common prediction equations. Agreement between measured and estimated height was determined using the Bland-Altman method.

Limits of agreement were wide for all equations, usually in the range of ±10 cm. Repeatability of the individual measures was high, with a coefficient of variation of 1%-2% for all measures. The equation using knee height demonstrated a nonuniform difference in which height estimation worsened as overall height increased.

Accurate measurement of height is important but very difficult in individuals with cerebral palsy. Segmental measures are highly repeatable and thus may be used on their own to monitor growth. However, when an accurate measure of height is needed to monitor nutritional status (i.e., for body mass index calculation), caution is warranted because there is only fair-to-poor agreement between actual height and estimated height.