Longitudinal shrinkage in lower legs: "Negative growth" in healthy late-adolescent males

Abstract

We examined the final period of tibial growth in late adolescent males. Forty-one healthy male subjects, aged 15.7 to 19.8 years participated in a study on lower leg length (LLL) growth, body height and weight increments. All subjects were measured and weighed at weekly intervals over a period of one year. Body height was determined by an anthropometer, body weight by conventional scales, and LLL was measured by a hand-held knemometer. The state of maturity of the proximal tibial epiphyses was determined by magnetic resonance imaging (MRI). Skeletal maturity was independently assessed by two radiologists. The growth plates were categorized as being open (category I), centrally but not completely fused (category II), or completely fused (category III). Our findings demonstrate that in these adolescents, final tibial growth is characterized by longitudinal shrinkage. As shown in the MRI, when the proximal tibial growth plates have fused (i.e., at an age when lower leg growth is commonly believed to have completed), the lower leg of healthy adolescent males begins to shrink with a negative growth rate of -2.4 (SD 2.1) mm/year. Apart from sporadic observations in anorectic girls, longitudinal shrinkage in LLL has not been previously documented. We assume that the final period of growth includes small reductions in bone length, possibly due to stabilization and rearrangements in the formerly growing cartilaginous tissues.