ABSTRACT
The purpose of this study was to evaluate the influence of hormonal milieu on endochondral
growth. This was achieved by transplanting hind limbs of juvenile rats to syngeneic
adult rats. Because there is no potential for rejection, the limb can be transplanted
between animals of different ages, to study the influence of hormonal maturity on
stimulation and cessation of physeal growth and maturation. Tibial length and the
histologic appearance of the physis were recorded.
Whole vascularized hind-limb transplantation in syngeneic Lewis rats was used. Group
1: Thirty-five transplants between animals of the same age (three weeks old) were
performed (isochronografts). Group 2: In 35 procedures, the age of the donor was three
weeks and of the recipient, 15 weeks (heterochronografts). In the first two study
groups, the transplanted limb was placed on the dorsal flank of the recipient animal
without nerve reconstruction. Controls were the contralateral hind limb of the donor
animal.
Because the limb was transplanted with loss of femoral and sciatic nerve supply to
the dorsal flank position, the effects of denervation and lack of weight bearing were
also evaluated. Group 3: Thirty-five limbs in three-week-old animals were transposed
to the dorsal flank position, after severing the femoral and sciatic nerves. Analysis
of variance of tibial length was used to compare study groups.
Limbs transplanted to older animals (heterochronografts-Group 2) achieved the greatest
length, 91 percent of normal, and significantly more when compared to Groups 1 (84
percent) and 3 (83 percent) (p < .005).
Growth of the limb was adversely affected by limb position and denervation. The growth
rate of the transposed limb (Group 3), in comparison to the paired unoperated limb,
significantly slowed at four weeks of age. The columnar arrangement at the growth
plate was also adversely affected by limb position and denervation.
