Knee-heel length measurements in preterm infants: evaluation of a simple electronically equipped instrument.
OBJECTIVE
To compare and evaluate a mini-knemometer with a simple and inexpensive electronic caliper with regard to precision, handling error (technical error) and estimation of growth velocity.


METHODS
Thirty-five prematurely born infants, with a median gestational age of 29 (range 24-33) wk and a median birthweight of 960 (range 480-2,480) g, were measured on 409 different occasions with both instruments. On each occasion, five independent readings were made.


RESULTS
There was no significant difference in precision between the two instruments, when measuring growth velocity over a 4 wk period (median 0.41, range 0.10-0.59 mm d(-1)). The handling error in this study, calculated as the mean standard deviation, was 0.36 (SD 0.18, coefficient of variation 0.38%) mm for the simple electronic caliper and 0.59 mm for the mini-knemometer. Short-term growth was detectable within 2 d when growth velocity was normal.


CONCLUSIONS
Longitudinal measurement of lower leg length is a gentle and useful complementary method for assessing growth in preterm infants. An inexpensive electronic caliper is well suited for routine use in clinical practice, with measurements taken once or twice a week.
Engström
E
E
Department of Pediatrics, Göteborg Pediatric Growth Research Center, The Queen Silvia Children's Hospital, Sahlgrenska Academy, University of Göteborg, Sweden. eva.engstrom@vgregion.se
Wållgren
K
K
Hellström
A
A
Niklasson
A
A
D000886:Anthropometry / Q000295:instrumentation*; D004582:Electronics, Medical / Q000295:instrumentation*; D005260:Female; D005865:Gestational Age; D006365:Heel; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000254:growth & development*; D007717:Knee; D008137:Longitudinal Studies; D008297:Male; D015203:Reproducibility of Results; D013997:Time Factors