Characterization of regional and age-related variations in the growth of the rabbit distal femur.

Abstract

Fluorochrome labeling and microcomputed tomography were used to completely characterize the regional and age-related variations in bone growth in the distal femur of the young rabbit. Use of the microcomputed tomography system, in conjunction with the more routine fluorochrome labeling, allows the investigation of changes in shape that occur during development. The growth plate in the distal femur studied here is remarkable for several reasons. First, growth rates of as much as 700 microns/day were measured, a much higher rate than those typically measured in other species or in more mature animals. In addition, regional variations in bone growth rates of as much as 300 microns/day were identified in the 6-week-old rabbit. These variations resulted in the formation of a complex curvature in the growth plate, including four mammillary processes. Identifying the factors that regulate this type of regional variation may be especially useful in understanding the causes for angular deformities such as tibia vara or developmental dysplasias.