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CHAPTER 17 III The Leg 167

Unreduced pile-driver fractures involving the distal
tarsometatarsal shaft can resemble expansile bone
tumors and admittedly are quite rare in birds. Pile-
driver fractures split the bone distally, which doubles or

triples its width, and then fill in the surrounding tissue
void with an excessive volume of cloudlike new bone
encouraged by fragment movement (Figure 17-9).
In my experience, appendicular soft tissue tumors
occur more commonly than primary or secondary
bone tumors. In some instances, these soft tissue
tumors invade the nearby bone quite extensively and
can be difficult to distinguish from infection (Figure

17-10).
Irrespective of cause or location, the radiographic
diagnosis of both recent (Figure 17-11) and old (Figure
17-12) tibiotarsal injuries is best served with at least a
pair of projections made at right angles to one
another.

Pathological Fractures
Other than the insuffi ciency fractures that can accom-
pany nutritional secondary hyperparathyroidism,
pathological fractures rarely occur in birds. When they
do, it is usually because of a primary bone tumor or
an invasive soft tissue neoplasm (Figure 17-13).

III LOWER LIMB AND FOOT

Figure 17-6 • Immediate postoperative, craniocaudal view of the Getting a Grip: The Importance
proximal right tibia of a snow goose shows not only the recently
installed pin and cerclage system used to repair the tibia but also of Perching
a partial dislocation of the genual joint as well, which was missed
in the initial radiographic assessment. A bird’s ability to perch, or inability as the case may
be, cannot be overstated. Many birds eat, drink, groom,
Sprain and sleep while perched. The elaborate pebbled-pad
system found on the undersurface of the digits of some
Isolated sprains and related dislocations are rare in birds enables them to maintain their grip even on rain-
birds; most such injuries are caused by some form of slicked or icy surfaces (Figure 17-14).
entrapment. In my experience, fractures and fracture- Some birds, such as jays, not only use their feet for
dislocations of the genual joint, particularly those that perching but also to grasp their food as they eat (Figure
involve the proximal tibia, account for the majority of 17-15). Woodpeckers typically assume a unique heads-
third-degree knee sprains (Figure 17-6). up position as they ascend and descend the trunks of
trees, constantly probing for insects as they go.
Hawks can often be seen perched on power poles,
Infection
regularly swiveling their heads as they search the sur-
Infection, particularly that associated with deeply pen- rounding landscape for unwary prairie dogs. Owls,
etrating wounds, can extend to one or more of the harboring similar ambitions, may remain motionless
nearby knee bones, causing osteomyelitis (Figure 17- for minutes at a time, except for the occasional blink
7). Intraarticular puncture wounds can inoculate bac- of an eye. Many cage birds, including some raptors,
teria directly into the joint, causing septic arthritis. can conveniently be examined while perched on a
hand or finger, thereby eliminating restraint-related

stress (Figure 17-16).
III TIBIOTARSAL FRACTURES
With perhaps a single exception, there is little that is III TALONS: THE ULTIMATE
unique about tibiotarsal body fractures, with most EXTERNAL FIXATOR
being readily identified using the standard two-view

study. The exception is the folding or bending fracture, a The talons of raptors are extremely versatile, capable

form of insufficiency injury, which often accompanies of stunning, impaling, and mortally wounding prey,
nutritional secondary hyperparathyroidism (Figure 17-8). Text continued on p. 177.

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