Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

Chapter Four The Appendicular Skeleton 545
Fig. 4-90 A, 5-year-old male Rottweiler had several months of
lameness of the left forelimb. Radiographic findings revealed that the
seventh palmar metacarpophalangeal sesamoid (arrow) was in multiple
pieces. Diagnosis: Fragmented palmar sesamoid.
patchy and mottled, and expand to fill the medullary canal. The endosteal surface may
become irregular and mild periosteal proliferation may be present (Fig. 4-94). These
changes persist for 4 to 6 weeks and then gradually recede. During the fourth and final
phase, the medullary canal regains a normal or decreased density and cortical thickening
may persist. Detecting very early lesions is difficult, especially if the radiograph is underexposed.
Comparison radiographs of the unaffected limb may be extremely helpful. The radiographic
lesion may not be visible at the time the lameness is first observed.
Differential diagnosis of these lesions should include panosteitis as well as neoplasia
and hematogenous osteomyelitis. The history and clinical signs are important in determining
a final diagnosis.
H Y P E RT R O P H I C O S T E O D Y S T R O P H Y
Hypertrophic osteodystrophy usually is seen in rapidly growing large-breed dogs between
3 and 8 months of age. 395-397 The cause is unknown, although infectious and nutritional
etiologies have been proposed. 398-402 The affected dog may be intermittently depressed,
anorectic, febrile, and reluctant to walk or stand. Often there are obvious distal metaphyseal
swellings, which may feel warm on palpation. Spontaneous remission may occur; however,
recurrent episodes are common. Severe disease may result in angular limb deformity
and retarded growth.
Initial radiographic changes include transverse radiolucent bands within the metaphysis
adjacent to the physeal plate and soft-tissue swelling. All long bones may be affected, and
lesions also may be seen at the costochondral junctions. The abnormalities are most obvious
in the distal radius, ulna, and tibia due to the rapid rate of bone growth in these areas.
With time, the metaphyses will appear widened and their opacity will increase. A cuff of
periosteal proliferation may be seen that is separated from the metaphysis by a thin linear
radiolucency, but it gradually blends with the diaphyseal cortex. The bony changes appear