Figure 820

Photomicrograph of fractured long bone undergoing repair.

a. This low-magnification photomicrograph of a 3-week-old bone fracture, stained with H8-E, shows parts of the bone separated from each other by the fibrocartilaginous callus. At this stage, the cartilage undergoes endochondral ossification. In addition, the osteoblasts of the periosteum are involved in secretion of new bony matrix on the outer surface of the callus. On the right of the microphotograph, the fibrocartilaginous callus is covered by periosteum, which also serves as the attachment site for the skeletal muscle. x35. b. Higher magnification of the callus from the area indicated by the upper rectangle in reapproximating the normal structure, and holding the parts in place by internal fixation (by pins, screws, or plates) or by external fixation (by casts or by pins and screws) speeds the healing process and usually results in superior structural and functional restoration.

a shows osteoblasts lining bone trabeculae. Most of the original fibrous and cartilaginous matrix at this site has been replaced by bone. The early bone is deposited as an immature bone, which is later replaced by mature compact bone. x300. c. Higher magnification of the callus from the area indicated by the lower rectangle in a. A fragment of old bone pulled away from the fracture site by the periosteum is now adjacent to the cartilage. It will be removed by osteoclast activity. The cartilage will calcify and be replaced by new bone spicules as seen in b. X300.

0 0

Post a comment