Paralysis and long bone growth in the chick: growth shape trajectories of the pelvic limb.

Growth of chick embryonic femora, tibiotarsi and first phalanges of digit three were measured at one day intervals from day 6 through 16 of incubation. Normal controls were compared to embryos paralyzed at 5 days of incubation. Over the 10 day study period, length of the paralyzed femora, length and width of the paralyzed tibiotarsi and differences in length of the phalanges were observed. Growth in length of phalanx one of digit three was most affected by paralysis over this period. Changes in shape of these bones also occurred during growth. Normal long bones undergo changes in shape as differential growth in length and width occurs. Such changes in shape can be considered as the bone's normal growth "trajectory". Paralyzed bones displayed a different growth trajectory than normal bones. As expected, the long bones of paralyzed embryos were shorter than age-matched controls. Contrary to expectations, however, paralyzed long bones were relatively more stout than age-matched controls.