Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

482 Small Animal Radiolo g y and Ultrasono graphy
1. Transverse: The fracture line is perpendicular to the long axis or both cortices of
the bone (Fig. 4-4).
2. Oblique: The fracture line strikes the long axis or cortex at an angle other than 90
degrees (Fig. 4-5).
3. Spiral: The fracture line encircles the shaft and forms a spiral relative to the long
axis of the bone (Fig. 4-6).
4. Comminuted (butterfly fragment, segmental): Multiple fracture lines within the
same bony segment divide the fracture into more than two fragments (Fig. 4-7).
5. Impaction (depression, compression): Displacement of one fragment forcibly into
another.
6. Incomplete (including greenstick fractures, which involve all cortices with minimal
to no displacement); plastic bowing fractures, which involve the trabeculae and
microscopic fractures in the cortex resulting in bending with no apparent fracture
line; and torus fractures, which result in bone expansion that combines plastic
deformity and a complete fracture of a cortex (Figs. 4-8 and 4-9).
7. Multiple (segmental): Two or more separate fractures within the same bone with
no communication of fracture lines (Fig. 4-10).
8. Fissure (incomplete fracture): A crack in the cortex (Fig. 4-11).
9. Avulsion: Displacement of fragment at the site of muscle or tendinous insertion
(Fig. 4-12).
10. Pathologic: Fracture that results from underlying disease that decreases bone
strength (Figs. 4-13 and 4-14).
11. Fatigue (stress): Discontinuity due to repetitive stress with gradual interruption of
the bone structure at a greater rate than can be offset by the reparative process.
The position of the major distal fragment relative to the major proximal fragment must
be described according to its location on both views. Displacement may be cranial and
Text continued on p. 488
Fig. 4-4 A 2-year-old female Greyhound unable to bear weight
on the left foreleg. There is marked soft-tissue swelling of the left
foreleg. Transverse fractures of the radius and ulna involve the
middle and distal thirds. There is lateral and cranial displacement
of the distal fragments with overriding. Diagnosis: Transverse
fracture.