Page 217 - Canine Lameness

13.7 ctrF ­gesrresres ooracgoe ctrf rFrral reg o 189

13.7.3 Hypertrophic Osteodystrophy
HOD is an inflammatory disease affecting the metaphyseal region of long bones in growing dogs,
particularly dogs of large and giant breeds. The disease is often limited to or is most severe in the
distal portion of the antebrachium (if it extends beyond the distal region). Usually developing at
3–4 months of age, HOD is often associated with hyperthermia, anorexia, diarrhea, severe pain in
the metaphyseal regions of long bones, and a loss of willingness to ambulate. The clinical signs
often subside after a week or so. However, severely affected dogs may require hospitalization and
supportive care. Episodes can recur every few weeks until the end of growth. The cause of HOD is
not known. Factors implicated have included vitamin C deficiency and the presence of viral RNA
in metaphyseal osteoblasts. In severe instances, HOD can lead to the formation of periosteal new
bone and to antebrachial and crural deformities. Soft tissue mineralization has been reported in
severely affected dogs. HOD is diagnosed by use of radiography (Figure 13.12). The distal radial CARPAL REGION

(A) (C) (E)

(B) (D)

Figure 13.12 Hypertrophic osteodystrophy (HOD): (A, B) classic appearance of a lucent “double physis” line
(white arrow) paralleling the distal radial and ulnar physes; (C, D) variations of a double physis; (C) a broader
lucent line is visible particularly in the distal radius; (D) early changes with HOD, showing a faintly visible lucency
adjacent to the physis; and (E) chronic appearance of HOD, note that the double physeal lines are still visible.