Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

496 Small Animal Radiolo g y and Ultrasono graphy
Fig. 4-27 A 4-month-old female mixed breed dog that was hit
by a car and had a fracture of the right elbow repaired 6 weeks
previously. The dog was again not bearing weight on the right
front leg. There is a transverse fracture of the right humerus.
The fracture fragment margins are indistinct. There is a faint
periosteal response on the medial and lateral aspects of the distal
fragment (arrows) and medial displacement of the fragment.
There is an old malunion fracture of the distal right humerus.
The lateral condyle is displaced proximally. This fracture has
healed, with callus bridging the old fracture site and considerable
elbow deformity. Sclerosis of the ulnar articular surface
indicates the presence of degenerative joint disease. The indistinct
margins and bony proliferation in the midshaft humerus
are compatible with a 1-week-old fracture. There is no evidence
of underlying bone disease. The cortical thickness and
medullary density are normal. This represents early healing and
not a pathologic fracture. Diagnosis: Healing transverse
humeral fracture.
The nature of the fracture, the type of repair and its adherence to proper fixation principles,
and the patient’s clinical signs determine the frequency with which follow-up
radiographs should be obtained. A change in the patient’s status (i.e., reluctance to use the
limb, sudden onset of swelling, pain, or discharge) is an indication for immediate reevaluation.
Follow-up radiographs should be examined carefully for the progression of healing
or for the presence of complications.
C O M P L I C AT I O N S O F F R AC T U R E H E A L I N G
Complications that may be detected radiographically include the following:
1. Infection. 112-114
2. Fracture fragment movement.
3. Orthopedic device movement or failure.
4. Delayed union or nonunion of fracture. 112,113,115
5. New injury.
6. Joint disease, related or unrelated.
7. Soft-tissue abnormality, such as swelling, contracture, subcutaneous emphysema,
atrophy, or mineralization. 116
8. Premature physeal closure, partial or complete.
9. Fracture-induced sarcoma, usually long after fracture healing. 117
Identifying osteomyelitis at the site of a healing fracture can be difficult, because the radiographic
changes indicative of osteomyelitis are similar to those observed with normal
fracture healing (i.e., periosteal proliferation and bone lysis). 118 Excessive periosteal proliferation
or bone lysis, especially when located away from the actual fracture site, suggests
osteomyelitis (Figs. 4-32 and 4-33). 119 Exuberant periosteal proliferation also may occur in
young dogs when multiple intramedullary pins, or “stack pinning,” are used or extensive
periosteal stripping occurs. This may resemble infection; however, the absence of bony
destruction is helpful in recognizing this reaction.
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