Positional relationships of structures attached to long bones during growth. Cross-sectional studies.

The various soft structures attached to bones maintain relatively constant relationships during growth. The exact number of these relationships has, however, never been studied. As part of our ongoing research into the factors controlling muscle migration, we have determined these relationships for some structures. We studied the positions of 37 muscles from 24 New Zealand white rabbits ranging in age from birth to maturity. The muscles were selected to illustrate different kinds of attachments: fleshy and tendonous, restricted and extensive, and at both ends of a bone. The proximal and distal edges of attachments were carefully exposed and measured in a device that allowed us to measure the position relative to the ends of the bones without parallax distortion. We used the data to compute correlation coefficients and regression equations for position vs. length of bone. Results show that the correlation coefficient was above 0.9 for most cases and was significant at the 0.5 level for all but 4 cases. Slopes of the regression equations varied considerably, but in all cases they indicated that the closer to the end of a bone, the greater the distance migrated. The significance of these results is discussed.