Front Matter

Chapter 12 Disorders of the Canine Thoracic Limb: Diagnosis and Treatment 319

fibrocartilage that results in loss of palmar sup­
port and secondary hyperextension. Commonly,
carpal hyperextension injuries result from
trauma due to falls, stepping in a hole, or from
a twisting motion at the limb. One author (DD)
has noted unilateral and bilateral carpal
hyperextension injuries as a result of chronic
overloading of the carpi due to pelvic limb
impairment such as chronic cranial cruciate
ligament injuries. The degree of damage (grade
1, 2, or 3) will dictate the appropriate treatment;
however, conservative management of grade 3
carpal hyperextension injuries is rarely success­
ful and surgical fixation is recommended (pan­
carpal or partial carpal arthrodesis).
Luxations and subluxations can involve
the disruption of multiple ligaments (Figure
12.26B) as well as the joint capsule, and most
will require surgical intervention consisting
of either a pancarpal or partial carpal arthro­
desis (Kapatkin et al., 2012). The level of lux­
ation in dogs in one report has been shown to
be 31% at the antebrachiocarpal joint, 22% at
the middle carpal joint, and 47% at the carpo­
metacarpal joint (Parker et al., 1981), while
in  another report the authors suggest the
distribution to be 10% antebrachiocarpal,
50% middle carpal, and 40% carpometacar­
pal (Piermattei et al., 2006).

Common fractures associated with carpal

injuries in sporting and agility dogs include the

attachment sites for the collateral ligaments

(avulsion fractures) and compression or shear

fractures. Fractures of these sites result in joint

instability when stressed on palpation or dur­

ing weight bearing. Fractures of the carpal

bones can also occur and can be difficult to

diagnose on standard radiographs. Radial car­

pal bone fractures have been shown to occur in

active dogs that have not sustained significant

trauma, and male dogs tend to have a predilec­

tion. Boxers, English Springer Spaniels, Setters,

and Pointers may be at an increased risk and

the theory for this is due to incomplete fusion of

the centers of ossification in the radial carpal

bone of these breeds (Li et al., 2000; Tomlin et al.,

2001; Gnudi et al., 2003). Traumatic radial carpal

bone fractures are commonly associated with

the right carpus of racing Greyhounds (Johnson

& Piras, 2005). Right accessory carpal bone frac­

tures are also commonly diagnosed in racing

Greyhounds, likely due to the accessory carpal

bone acting as a fulcrum for the palmar carpal

ligaments and the flexor tendons thus pre­

venting hyperextension. Accessory carpal bone

fractures have been broken down into five

types based on the location (Johnson, 1987;

Johnson et al., 1989; Johnson & Piras, 2005).

(A) (B)

Figure 12.26 (A) Stress radiograph of a left carpal hyperextension injury. (B) Radiograph of a carpal subluxation with
damage to the dorsal carpal ligaments.