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A newly developed knemometric device for lower leg length measurement in premature and newborn infants is presented and validated. The present study was performed to establish a standardized method of use of this instrument. Two independent observers obtained 10 subsequential readings per measurement in three infants over 43 days, after which analysis showed that 5 subsequential readings per measurement gave comparable technical errors. Thirty-one premature infants were assessed by knemometry by two independent observers. The correlation coefficient of all measurements was 0.998. The acquired technical error (mean Standard Deviation (SD) of 5 sequential readings) over a total observation period of 294 days in all studied infants was 0.06 and 0.05 mm, respectively. By a mean lower leg length growth velocity of 0.52 mm per day the technical error amounted to 11% of daily bone growth. The described mini-knemometer is an accurate device for the detection of daily individual growth. A learning period of 21 days is necessary to obtain reliable results.

The study aimed to measure the direct effect of dexamethasone (DEXA) on daily lower leg length per mini-knemometry of premature infants and to examine whether the administration of different doses is associated with alternations in growth.We observed 20 premature children and had 276 complete mini-knemometrical and weight measurements (13.8 measurements per single child) for analysis. The gestational age of the infants was 26.8 +/- 1.9 weeks; the mean birth weight was 973 +/- 336 g. All infants underwent daily measurements of lower leg length performed by mini-knemometry. We divided the 41 DEXA administrations into three subgroups. Group I included a cumulative dose of 0.75 mg DEXA per kg bodyweight (BW), group II doses between 0.75 and 1.0 mg per kg BW and group III dosages above 1.0 mg per kg BW.We observed catch-up growth in group I within 24 h after stopping therapy. Groups II and III needed 48-72 h to achieve a normal level in short-term growth.Lower doses seemed to have an equivalent effect without long-term effect on lower leg length. In higher doses (groups II and III) the growth was suppressed for more than 24 h.

Lower leg length measurements in 19 healthy preterm infants were obtained by knemometry to assess short term growth. Eight infants received fortified human milk and 11 infants commercially available preterm formulas. Two independent observers measured lower leg length in each infant daily during the study period, weight was measured daily with a neonatal scale. While weight gain showed linearity in all infants, lower leg length growth showed mini growth spurts of 5 +/- 1.7 days, growth periods of 20 +/- 11 days or both types of short term growth. The overall weight gain was 35 +/- 5.6 g/day in infants fed human milk and 33 +/- 7 g/day in infants fed preterm formula. The overall lower leg length growth velocity was 0.51 +/- 0.04 mm/day versus 0.54 +/- 0.09 mm/day, respectively. Both groups had comparable weight and length increments. No correlation existed between the type of nonlinear lower leg length growth (mini growth spurts versus growth periods) and the feedings received by the infants.

During recent years knemometry has been introduced for short-term assessment of the growth-suppressive effect of exogenous glucocorticosteroids in children. The aim of the present paper is to review methodological aspects of short-term knemometry used for this purpose. Knemometry has proven a highly accurate and reproducible method for assessment of short-term growth suppression in populations of children treated with exogenous glucocorticosteroids. Randomized, double-blind crossover and parallel designs applying consistent measurement intervals can be used. Confounding influences on the growth results from possible inter-group differences in spontaneous growth velocities are reduced in the crossover design. Glucocorticosteroid-induced knemometric growth suppression seems to reflect suppressive effects on soft tissue and bone components in the lower leg. In children treated with systemic glucocorticosteroids a shortening of the lower leg, which may be due to a reduction of the water content in the soft tissue, may confound the growth assessment. Suppressed short-term growth rates should be considered to have a poor correlation with long-term growth, though prospectively planned, controlled studies of the relation are needed in glucocorticosteroid-treated children.

A novel miniaturization of knemometry for accurate measurements of the lower leg length in prematures, newborns and infants (mini-knemometry), is presented. The study was performed in four healthy neonates, born at term, and one infant, born in the 34th week of gestation, measured daily for periods of 40 days; and in two monozygotic healthy twin sisters, born in the 32nd week of gestation, measured daily for periods of 58 days. Each of the 316 measurements consisted of four independent subsequent estimations of the distance between heel and knee, which are grasped by two metallic holders under light compression of 2.0-3.0 N. After an initial training of 1 week the technical error is 144 microns. Lower leg growth is non-linear (p0.001) with periods of stunted, and periods of accelerated, growth velocity.

Knemometry is an accurate and non-invasive method of quantifying lower leg length changes. It reveals multiple fluctuations in leg length velocity over a short period of measurement, and on the basis of this it has been proposed that short-term growth is saltatory rather than a continuous phenomenon. The technical error (TE) of the technique which is generally employed, and which is subject to observer bias, ranges from 0.09 to 0.16 mm. This study was undertaken to compare the original method (OM) to a modified technique which involved measuring from a baseline value of which the operator was not aware; this technique is referred to as the random zero method (RM). Over a period of 10 months, 58 subjects were measured on 413 occasions. Overall, median TE in the RM group at 0.15 mm (P5-0, P95-0.65) was higher than the median TE in the OM group at 0.11 mm (P5-0, P95-0.37). However, the median TE over the last 3 months of 0.15 mm (P5-0.05, P95-0.87) was lower than the TE in the preceding 4 months of 0.20 mm (P5-0, P95-0.55) (WSR, p = 0.04) pointing towards the presence of an operator learning curve. The random zero method is a simple modification of the original method. It reduces observer bias but leads to a higher TE, which could explain some of the fluctuations seen between frequent knemometric measurements. Some knowledge of the length of the training period is important in the design of new studies involving knemometry; our data suggest that there should be a learning period of about 4 months if knemometry is performed as often as quoted above.

Recently, a new anthropometric method of accurate lower leg length measurement (knemometry) was introduced. The present study was performed to investigate rigorously its strengths and weaknesses for auxological purposes, and to promote a standardized method of use. The data are based on 6 x 2200 single estimations of the lower leg length in 90 children of both sexes with normal, tall or short stature aged between 2.4 and 17.1 years. The overall technical error of this measurement was found to be 0.16 mm, which is reduced to 0.13 mm if the first estimation within each series of six is ignored. The following sources of systematic error could be detected: intra-daily variation, dependency on physical pressure put on or removed from the leg, vigorous physical activity prior to the measuring procedure, and a slow but significant correlation between day-to-day variation of lower leg length and body weight (r = 0.299, b = 0.372 mm/kg). There was no covariation with atmospheric parameters such as outside temperature, barometric pressure and others. After elimination of a linear trend from the individual growth curves, there was a remaining day-to-day variation of SD = 0.697 mm. This represents real changes of lower leg length and cannot be explained by the technical error of measurement which contributes to less than 10% of the total variation. Some of this day-to-day variation may be explained by non-linearity of growth. Knemometry appears to be a robust and precise new tool for the investigation of short term kinetics of longitudinal growth. Proposals for a standardized use of this technique are given.

Evidence has accumulated that predictions of annual or half-annual growth rates are of limited validity when derived from extrapolations of short term growth rates. In order to investigate whether the poor predictive qualities of short sections of individual growth curves are caused by non-linearity of human growth, we have studied 73 healthy children, aged 2.9 to 15.9 years, with standard deviation scores for body height ranging between -3.3 and +3.0. The children were measured between 18 and 106 times once or twice per week throughout periods of 180 to 306 days by knemometry, a novel and noninvasive technique of accurate lower leg length measurement. Non-linearity of growth was found in about 70% of those children who could be measured more than 35 times. 45 children provided evidence for a characteristic up-and-down pattern of lower leg growth velocity consisting of sharp growth spurts ('mini growth spurts') alternating with periods of decreased growth velocity every 30 to 55 days. This pattern seemed to appear spontaneously, though in some cases we found a marked coincidence between periods of growth arrest and intermittent infectious illness.