Estimation of length or height in infants and young children using ulnar and lower leg length with dual-energy X-ray absorptiometry validation

The American Academy of Pediatrics recommends frequent length measurements during the first 18 months of a child’s life. In infants and children, length and height measurements are used in the determination of weight status,1 and measurements of stature are important in monitoring the growth and development of children. Therefore, accurate and reproducible measurements are important in preventing the misdiagnosis of several medical conditions. Frequent measurements of length are made in preterm infants and accurate monitoring is important as changes are small. Because preterm infants are sensitive to over-stimulation, a less invasive method for estimating length would be beneficial. Length and height measurements are also used in the estimation of pulmonary function and inaccurate measurements can lead to misdiagnoses. In children who are unable to have their height measured using standard measures, ulnar length measurements may provide an alternative method. Ulnar length measurements have been used to predict pulmonary function2 and height3 in children aged between 5 and 19 years. Our study expands on the findings reported by Gauld et al.3 to include infants and children from birth to 5 years of age. Data describing the accuracy of current length measurement methods in children vary and are inconclusive. Some studies have determined that when a proper technique is utilized the infant length board measurement is reliable and repeatable.4,5 However, other studies have reported the amount of error that exists between different examiners when using an infant length board measurement is large,6,7 and this has warranted the investigation of alternative length and height estimation methods. Heel-to-knee height has been used in the estimation of height in children with cerebral palsy.8,9 Additionally, a prediction equation using ulna length and age to determine height has been created for children between 5 and 19 years of age;3 however, no study has focused exclusively on children younger than 6 years of age using ulna measurements. A chart has been developed that expresses predicted segmental bone lengths as a percentage of sitting height in children as young as 2 years of age,10 but whether this relates to total body length or height is unknown Large epidemiological studies currently assess infant length using a supine length board and a child’s height using a portable stadiometer. One problem is that many of these visits take place in participants’ homes and the amount of equipment required for these visits can be overwhelming. The primary purpose of this study was to compare the accuracy and reproducibility of using ulnar and lower leg length to create prediction equations for length and height in infants and children aged 0 to 5 years. With this measurement technique, only a segmometer would be required. Other goals of this study were to determine if the reproducibility of limb measurements would be better than the reproducibility of infant length board and stadiometer measurements, and to determine whether the limb length measurements correlated with bone measurements using dual-energy X-ray absorptiometry (DXA).