How useful is knemometry in measuring neonatal growth?

Background:  Knemometry has been used to accurately measure linear growth in both neonates and children over the last 20 years. It has been used principally as a research tool.

Aim:  To investigate whether serial measurement of lower leg length (LLL) by knemometry is a useful addition to other measures of growth in the neonatal unit.

Methods:  A 1-year prospective hospital-based cohort study from 2004 to 2005. Knemometry was performed every 3–4 days from the time of consent to time of discharge. Infants were grouped by gestation at birth for analysis (<28 weeks, 28–31 weeks, 32–36 weeks and >36 weeks gestation). The main outcome assessed was longitudinal growth. Subgroup analyses were performed on infants <10th percentile for weight, surgical infants and infants who had received antenatal steroids.

Results:  LLL measured by knemometry correlated well with postmenstrual age (r = 0.93) and weight (r = 0.93). The mean (SD) increase in LLL was 0.45 (0.7) mm/day.

Conclusion:  Change in LLL correlates well with change in weight and postmenstrual age in the neonatal period but adds little extra information to routine practice in the neonatal unit.