Morphological and radiological findings in induced abnormal bone growth in lambs.

Unilateral hip excision arthroplasty in skeletally immature lambs resulted in altered load bearing and posture in the contralateral limb. Derangement of endochondral bone growth occurred in distal tibiae and metatarsi and both angular and torsional deformities developed. There was no absolute correlation between torsional and angular deformities. Although femoral torsion was variable, the unoperated pelvic limbs frequently developed exaggerated internal torsion of tibiae and metatarsi. Tibiae of operated limbs developed less torsion than was seen in control animals. These findings suggest that functional limb loading can modify developing bone torsion and that torsional deformities in lambs may be a consequence of increased functional torque.