Front Matter

302 Canine Sports Medicine and Rehabilitation

Cause

The cause of injury in performance dogs
appears to be repeated strain injury, including
two‐on/two‐off contacts in agility, landing ver­
tically on the thoracic limbs following a mis­
judged jump, overstretching the muscle, quick
turns, and repetitive contractions of the muscle
with the shoulder flexed and/or elbow
extended. The tendon can be injured via strain
from overloading, leading to degeneration or
disruption (Wernham et al., 2008). Disruption
can occur from a single, less‐than‐maximum
load that injures some fibers without complete
failure of the tendon. Because the blood supply
to the tendon is poor, healing time is protracted
(Sharma & Maffulli, 2005). Degeneration of the
tendon may be initiated by repetitive strain
(Sharma & Maffulli, 2005). Continuous reinjury
of the biceps tendon may sufficiently weaken it
such that the surrounding tendons become
inflamed and/or develop microtears, ulti­
mately leading to shoulder joint instability
(Gilley et al., 2002).

Diagnosis

Complaints of difficulty with quick turns and
reluctance to jump are common in performance
dogs with BT. Agility dogs present with com­
plaints regarding performing two‐on/two‐off
contacts and knocking bars with their thoracic
limbs.
Patients often have a shortened stride and a
weight‐bearing lameness that can range from
subtle to severe. The lameness worsens with

activity. Direct palpation over the biceps ten­

don may elicit a pain response. Pain and spasm

may be noted when performing the biceps

stretch (flexing the shoulder with the elbow in

extension) (Gilley et al., 2002) (Figure 12.8). A

bony avulsion may be detected radiographi­

cally. Chronic cases may reveal mineralization

of the tendon or sclerosis within the bicipital

grove (Gilley et al., 2002). MRI and ultrasound

may be used to identify acute and chronic cases

(Gilley et al., 2002; Wernham et al., 2008) (Figure

12.9). Shoulder arthroscopy is an excellent diag­

nostic modality as well as therapeutic tool, if

indicated (Wernham et al., 2008) (Figure 12.10).

Figure 12.8 Example of a passive biceps stretch (shoulder flexion with elbow extension).

Supraglenoid

tubercle

Abnormal fibrous tissue

Humerus

Mixed echogenicity

representing disrupted

biceps tendon fibers

Figure 12.9 Ultrasound image demonstrating disrupted

hypoechoic biceps tendon fibers.