Page 868 - Adams and Stashak's Lameness in Horses, 7th Edition

834 Chapter 7

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Figure 7.34. Three 0.25‐in. (6.35‐mm) diameter threaded
intramedullary (IM) pins were placed through the distal metatarsus
and incorporated into a fiberglass cast (transfixation pin cast) to
prevent collapse of this severely comminuted first phalanx fracture.
Two transfixation pins are usually recommended with the most distal
pin placed in the center of, or slightly proximal to, the condylar
97
fossa. Source: Rossignol et al. Reproduced with permission of
Veterinary Surgery.
internal fixation of fractures may need to be removed in
performance horses to prevent these problems.
Another problem that can arise secondary to fracture Figure 7.35. A radiograph of the third metacarpal fracture
fixation is the secondary problems related to casting. It repaired with internal fixation. Note the lysis at the fracture line that
is not uncommon to see significant loss of bone density, is indicative of a nonunion (arrow).
especially within the proximal sesamoid bones
35
(Figure 7.21). Clinically significant lameness unrelated open fractures or those repaired with internal fixation.
7
to the primary disease can also result, as has been seen Severe infections may necessitate euthanasia of the ani­
in several experimental studies in which lower limb mal, whereas milder more chronic infections may neces­
casts have been applied to horses. Lameness, pain on sitate removal of the implants or necrotic bone to resolve
flexion, and significant physical changes to bone density the infection. Open infected fractures that eventually
and soft tissue integrity have been observed. heal are often accompanied by considerably more fibro­
Tendon and muscle flaccidity and atrophy of sur­ sis with a greater chance of loss of function of surround­
rounding muscles are also seen in horses with fractures ing structures than closed noninfected fractures. The
treated with external immobilization such as casts. This limb may be permanently thickened due to scar tissue
usually is a temporary problem that is self‐correcting and callus formation, which may lead to impaired limb
with time, but may lead to permanent lameness. Other function. 119
aspects of so‐called fracture disease in the non‐fractured
limb include ALDs due to excessive axial loading on Bone Infections
active growth plates in young horses, stretching of flexor
tendons and associated muscles, and support limb lami­ Osteitis and osteomyelitis are terms used to describe
nitis due to excessive weight‐bearing. Support limb lam­ inflammation of bone involving the periosteum and con­
initis with rotation of the distal phalanx is unique to the nective tissues of the Haversian and Volkmann canals as
horse and is a potentially devastating complication of well as the medullary cavity. If the process begins or
119
equine fracture repair. involves the periosteum and outer bone cortex, the term
Infection is a serious complication of fractures that osteitis or osteoperiostitis is used. If the infection involves
can eventually lead to permanent lameness or a nonun­ the medullary cavity, the term osteomyelitis is used. The
ion of the fracture. Infection is most likely to occur with prognosis and treatments for osteitis and osteomyelitis