Front Matter

308 Canine Sports Medicine and Rehabilitation

Additional shoulder disorders

Shoulder conditions that occur less commonly
but that should be considered during the work‐
up include infraspinatus tendinopathy, teres
major strains, shoulder dysplasia, glenoid frac­
tures, osteoarthritis, frozen shoulder (Carr et al.,
2016), osteosarcoma, and synovial cell sarcoma.
Conditions that may cause referred shoulder pain
and resemble shoulder conditions include caudal
cervical disease and brachial plexus masses.

Elbow disorders

Elbow dysplasia

Elbow dysplasia is a common cause of thoracic
limb lameness in companion dogs. The term
dysplasia simply means an abnormality in
development (Blood & Studdert, 1999). Elbow
dysplasia encompasses three distinct syn­
dromes that result from abnormal growth
and  development: ununited anconeal process
(UAP), fragmented medial coronoid process
(FCP), and osteochondrosis (Wind & Packard,
1986; Schulz & Krotscheck, 2003; Trostel et al.,
2003b). The pathogenesis responsible for these

growth disturbances is not completely under­

stood, but is thought to be due to asynchronous

growth of the radius and ulna with genetic and

nutritional origins (Wind & Packard, 1986;

Schulz & Krotscheck, 2003; Trostel et al., 2003b).

Other developmental conditions of the elbow

that are not classically included in the defini­

tion of elbow dysplasia include incomplete

ossification of the humeral condyle (IOHC) and

ununited medial epicondyle (UME) (Marcellin‐

Little et al., 1994; de Bakker et al., 2011).

Ununited anconeal process

Pathophysiology

The pathophysiology of UAP is incompletely

understood. Several theories have been

proposed, including nutritional deficiency,

trochlear notch dysplasia, trauma, osteochon­

drosis, metabolic deficiencies, and hormonal

effects (Corley et al., 1968; Krotscheck et al., 2000;

Schulz & Krotscheck, 2003; Trostel et al., 2003b).

Evidence suggests that incongruous growth of

the radius and ulna, such that the radius is rela­

tively longer than the ulna, results in abnormal

pressure on the ossification center of the anco­

neal process, leading to failure of the anconeal

process to fuse to the proximal ulna (Wind &

Packard, 1986; Schulz & Krotscheck, 2003). The

anconeal process normally fuses with the ulna

by 20 weeks of age (Corley et al., 1968).

A genetic basis for UAP has been postulated

and German Shepherd Dogs are overrepresented,

with an incidence of 18–30% reported (Wind &

Packard, 1986). Other large, giant, and chondro­

dystrophic breeds can be commonly affected as

well (small‐breed dogs do not have a separate

center of ossification at the anconeal process)

(Wind & Packard, 1986; Trostel et al., 2003b). Male

dogs may be predisposed, and the condition is

bilateral in up to 30% of dogs (Wind & Packard,

1986; Trostel et al., 2003b). Other developmental

conditions of the elbow do not commonly occur

in conjunction with UAP; although one study

found that 16% of dogs with UAP also had FCP

(Meyer‐Lindenberg et al., 2006).

Diagnosis

Diagnosis of UAP cannot be made until a dog is

older than 20 weeks (Corley et al., 1968). Most

Figure 12.18 Postoperative radiograph of a shoulder
reconstruction using a prosthetic ligament and anchor
system (severe medial shoulder instability).