Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

502 Small Animal Radiolo g y and Ultrasono graphy
Fig. 4-32 An 8-month-old female Collie had transverse fractures of
the radius and ulna repaired 5 weeks previously. There are two
intramedullary pins in the radius and ulna that extend into the distal
fragments for a short distance. There is cranial and medial angulation
of the distal fragments and diffuse mild soft-tissue swelling. Marked,
active, irregular periosteal reaction extends both proximal and distal to
the fracture site. There is increased density within the medullary canal
of both the radius and ulna. Areas of irregular bony reabsorption are
present around the distal aspect of the radial intramedullary pin, and
areas of radiolucency with slightly increased density are visible within
the proximal and distal radial metaphyses (arrows). There is extensive
bony destruction at the fracture site. Diagnosis: Osteomyelitis at the
site of fracture repair. The extensive bony proliferation distant to the
fracture site and the areas of bony destruction within the radial metaphysis
and the fracture site suggest the diagnosis of infection. The irregular,
mottled periosteal response should be contrasted with the more
uniform and evenly mineralized callus usually associated with a healing
fracture.
Fig. 4-33 A 4-year-old male Siberian
Husky whose left front foot was
traumatized 4 months previously. A
fractured fifth metacarpal bone was
pinned at that time. The fracture is
still visible and an intramedullary pin
is present within the fifth metacarpal
bone. There is no evidence of callus at
the fracture site. There is an irregular
radiolucency around the intramedullary
pin and extensive bony proliferation
around both the proximal and
distal fragments, as well as on the first
phalanx of the fifth digit. Diagnosis:
Nonunion of fracture secondary to
infection and instability.