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94 SECTION I III The Birds

Figure 10-1 • Dean Hamilton releases an owl after its complete recovery from a fractured wing.

salts. But later, the interfragmentary gap begins to Given the influence of fragment motion (or lack

cloud as mineralization occurs and new bone forms thereof) on callus size, one should be suspicious of any
along the fragment edges. These events characterize nonreduced fracture that fails to readily form a callus.
the conversion of a soft to a hard callus (Figure 10-4). Likewise, one should also be concerned about a
With the further passage of time the callus becomes reduced fracture that forms an inappropriately large

increasingly denser, reflecting its conversion to bone. callus.
Concurrently, the fracture line or lines become increas-
ingly faint, eventually disappearing. On reaching Delayed Fracture Healing. A delayed fracture is one
maturity, a purposeful callus slowly begins to recede, that requires more time to heal than originally pre-
eventually being fully or partially incorporated into dicted. For example, a simple, minimally displaced
the adjacent bone, and sometimes also disappears fracture of the radial midshaft in an otherwise healthy
(Figure 10-5). raptor, treated by simple strapping, might be expected
A nonpurposeful callus is one that develops at the to heal in about a month. But if the bird repeatedly
ends of one or both fragments but fails to form in the undoes its bandaging, necessitating capture, anesthe-
interfragmentary gap. This type of ineffective callus is sia, and rewrapping, the resultant callus disturbance
usually the result of fragment motion, which inhibits will likely add an additional 1 or 2 weeks to the total
or disrupts the development of local vascularization. healing time. Accordingly, the healing process will be
The presence of a nonpurposeful callus signals the prolonged.
potential for a delayed union, or worse, a nonunion Some fractures, for example, those involving the
(Figure 10-6). shoulder bones, especially the coracoid, routinely take
longer to heal than other wing bones. Often, there is
Callus Size and Its Prognostic Signifi cance. For little or no evidence of healing for a month or more
various reasons, surgery is not always performed on (Figure 10-7). Occasionally, new bone forms near but
many wing fractures. In such instances, callus forma- not actually in the fracture gap, making it seem that
tion often appears excessive. However, the presence of the fracture is healing in the ventrodorsal (VD) view.
an exuberant callus in an unstabilized fracture is not a A lateral, wings-up projection will usually reveal the
cause for concern because it is almost certainly the true status of the injury (Figure 10-8).
result of fragment motion and the additional bony
response incurred. The Calculation of Predicted
Conversely, a fracture that has been anatomically Healing Time
reduced and stabilized often shows only minimal

callus formation, especially in the first weeks after the As indicated previously, the predicted healing time of

surgery, which is mostly a result of a lack of fragment a given fracture is first based on its severity and next
motion and is characteristic of plated fractures. Text continued on p. 102.

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