Bone - Callus

Bone - Callus in a male Wistar rat from a chronic study. There is callus formation surrounding a rib, characterized by a marked proliferative fibrous connective tissue response and bony remodeling.
Figure 1 of 4

Bone - callus in a male Wistar rat from a chronic study (higher magnification of figure 1). Section of a bone callus, characterized by a marked proliferative fibrous connective tissue response and bony remodeling.
Figure 2 of 4

Bone - callus in a male F344/N rat from a chronic study. This section of long bone with a callus is characterized by a focal fibroblastic response (arrowhead).
Figure 3 of 4
comment:
Shortly after fracture and resolution of hemorrhage, fibroblasts adjacent to the fracture site begin to replicate and form loose granulation tissue ( Figure 1



recommendation:
Bone - callus, when observed, should be diagnosed but not graded. When observed in conjunction with a fracture secondary to neoplasia, ongoing inflammation or infection, or metabolic disease, fracture callus should not be diagnosed but should be discussed in the narrative. Associated lesions, such as inflammation or fibrosis, should not be diagnosed separately unless warranted by their severity.references:
Brighton CT, Hunt RM. 1991. Early histologic and ultrastructural changes in medullary fracture callus. J Bone Joint Surg 73:832-847. Abstract: http://www.ncbi.nlm.nih.gov/pubmed/2071617
Leininger JR, Riley MGI. 1990. Bones, joints, and synovia. In: Pathology of the Fischer Rat: Reference and Atlas (Boorman G, Eustis SL, Elwell MR, Montgomery CA, MacKenzie WF, eds). Academic Press, San Diego, 209-226.
Long PH, Leininger JR. 1999. Bones, joints, and synovia. In: Pathology of the Mouse (Maronpot R, Boorman G, Gaul BW, eds). Cache River Press, St Louis, 645-678.
Web page last updated on: March 13, 2015