LCK Low, YW Kwan, MC Tsang, CY Yeung, J Karlberg

Aim Lower leg length (LLL) gives a more accurate estimate of short-term linear growth than total body length as it is less influenced by measuring error. The aim of this work was to construct reference values for LLL in healthy Chinese infants during the first year of life.

Material and Methods Seventy-one Hong Kong born healthy full-term Chinese infants were studied every second month from birth to one year of age. LLL was measured by means of the hand-held knemometer (manufactured by the FORCE Institute, Denmark), LLL is was estimated by the means of a pair of electronic callipers which automatically recorded the measurement when the pressure applied on the heel reached a preset value. The measuring system is based on a magnetic encoder with a resolution of 0.01 mm. Five sequential measurements were performed and the result of the measurement sequence was expressed as the average of the last four measurements.

Results The mean and SD of LLL were computed at the different ages between birth and one year of age (both sexes pooled); both estimates were fitted by a second degree polynomial function:

mean=125.724+13 0291*t-1.05321*t²+0.041012*t³

SD=3.67018+0.85278*t-0.092090*t²+0.0038488*t³

where t is age in years The mean values were similar to the mean values of Danish infants being followed between birth and six months of age, but the SD values were higher in the Danish series. In our study the boys had on the average significantly higher LLL values than girls; 0.35 SDS in comparison with -0.35 SDS based on our gender combined reference standard (t test, p<0.05 for all ages). At this stage we present the pooled data results for comparison with the Danish study.

Conclusion This is the first report on LLL reference values between birth and one year of age in normal infants. Our mean LLL values was similar to the values reported in Danish infants during the first 6 months of life implying no ethnic group differences for this body measurement. The reference values would be useful in metabolic and nutritional studies of different patient groups.

This study was supported by the Faculty of Medicine, University of Hong Kong