Bone in dermatosparaxis. I. Morphologic analysis.

Normal (N-) calf bone consists of lamellae regularly spaced and oriented parallel to the periosteum. The lamellae increase in thickness from the periosteum to the medullary cavity, by apposition of layers of cells and a calcifying matrix on either side of a hypercalcified primer. In the dermatosparactic (D-) bone, the hypercalcified primer is barely visible and the cells are irregularly arranged within the lamellae. The poorly defined vascular spaces are partly filled with an acellular calcified material. In the D-bone, the collagen fibers are sparse and radiate from the vascular space, while in the N-bone they are abundant and laid down concentric with the blood channels. In the D-bone, only a few weeks old, the outer lamellae are radially oriented with respect to the medullar cavity, while haversian remodeling already occurs in the inner part of the diaphysis. At 6 months, the inner half of the diaphysis is made up of normal haversian secondary bone, while the outer half is made up of radial lamellae. The alteration of the mechanical properties of procollagen fibers in the D-bone might be responsible for its defective organization. A resistant fibrous framework, therefore, seems required to ensure the spatial organization of the cells in the calcifying matrix and to maintain its cohesion.