A mature homeless cat was brought into the clinic lame on the right hind leg with no additional history. A single VD view of the pelvis was made with the legs in partial extension.

• A recent oblique midshaft femoral fracture was identified and it was stabilized using an external fixator. A technician assumed responsibility for the daily care of the cat at her home.
• A second set of radiographs was made after 4 weeks following removal of the fixator assuming that fracture healing had occurred as expected.

• Radiographs made 4 weeks following the injury show the fragments in good alignment with callus bridging the fracture site. Healing was as expected.
• The cat, however, remained lame on the limb.

Enlargements of the distal femur at the time of the injury (A) and at the time of evaluation of fracture healing (B).

Comments

• The destructive lesion in the distal femur was not noticed on the first radiographic study and was only detected on the studies made to evaluate fracture healing because of searching for a cause of the persistent lameness.
• The radiographic changes are typical of those seen with a primary bone tumor.
• The absence of any periosteal new bone make osteomyelitis an unlikely differential diagnosis.
• Because of an absence of an owner, the cat was euthanized without diagnostic biopsy or treatment.
• The fracture was not considered a pathologic fracture since it was away from the tumor and thought to be through healthy bone.