Histomorphometric study of growth plate subjected to different mechanical conditions (compression, tension and neutralization): an experimental study in lambs. Mechanical growth plate behavior.

We studied the morphologic effect of low mechanical stresses (compression, tension and neutralization) on the growth cartilage with an external fixator in 18 young lambs. On radiography, we only found more length in the femora subjected to tension (P < 0.05). Bony bridges were not present, nor were there signs of altered vascularization or Ranvier's perichondral ring. Histomorphometrically, in the group subjected to tension, the germinative layer in the femur was higher (P < 0.001) in the bones that had undergone surgery. The proliferative layer was lower in the operated tibia (P < 0.001), and the hypertrophic layer was higher in operated tibias and femora (P < 0.001). In the group subjected to compression, the germinative layer in the femora was higher in the operated bones (P < 0.05); the proliferative layer of the tibia was lower (P < 0.001) and the hypertrophic layer was higher (P < 0.001) in both operated bones. In the neutralization group, the proliferative layer of both operated bones presented lower values (P < 0.001) and the hypertrophic layer was higher (P < 0.001) than that in the control groups.