EXPERIMENTAL MODIFICATION OF MUSCLE MIGRATION IN RABBIT

Abstract

During growth in length of mammalian long bones, the muscles, tendons and ligaments attached to the diaphyses must migrate or creep along the shaft in order to maintain a normal relationship to the end of the growing bone. Factors controlling migration were studied in semimembranosus muscles of 8 wk old New Zealand White rabbits. For all animals, the tibia was marked with a piece of stainless steel suture wire. The original position of muscle insertion was measured. The muscle was detached and re-attached in the same position in 19 legs; moved 5 mm distally in 4, 10 mm distally in 5, 20 mm distally in 5 and left in the same position in 11. Animals were sacrificed 3 mo. later and position of insertion determined. The mean distance migrated for each group was 3.1, 4.7, 9.7, 23.9 and 11.1 mm, respectively. The correlation (r) between distance moved and distance migrated was 0.86, and the regression of distance migrated on distance moved was Y = 0.99 X + 2.35. There were no significant differences between length of the tibiae or weights of selected leg muscles between any experimental groups. Growth in length of the proximal end of the tibia during this time was about 14.7 mm. Apparently migration in the control animals kept approximate pace with bone growth, but the distance migrated in the experimental legs was greater the further distally the muscle was moved. There was some ability of the muscle to adjust its position and results did not support the hypothesis that rate and distance migrated was primarily dependent on position of attachment.