Page 275 - Canine Lameness

15.9 Osteochondrosis Dissecans 247

factor (Richardson and Zentek 1998). On occasion, evidence of osteochondrosis may become appar-
ent incidentally, as the disease progresses with secondary osteoarthritis, or if OCD affects other
structures (bicipital impingement secondary to joint mouse). Patients are typically lame in one limb,
with the lameness worsening with exercise or intensive activity. In spite of the tendency for unilat-
eral symptoms, approximately half of patients will have bilateral lesions (Rochat 2018).

15.9.2 Physical Exam
Most animals present with a mild-moderate weight-bearing lameness. Muscle atrophy may be pre-
sent if symptoms have been noted for a prolonged period. Patients experience pain most com-
monly on flexion of the shoulder joint; however, some dogs react on extension as well. It is
important to carefully examine the contralateral limb, given the frequency of bilaterality.
An absence of pain reaction does not rule out the presence of osteochondrosis or OCD.

15.9.3 Diagnostics

Radiographs are the first-line diagnostic of choice. OCD lesions typically are readily appreciated on
the caudal surface of the humeral head as a defect in the subchondral continuity. The flap is not
actually visualized radiographically unless it has mineralized. Subchondral sclerosis can be appre-
ciated with osteochondrosis or OCD. Positioning of the shoulder joint relative to other structures
should be heeded, as summation may challenge interpretation. The lateral view is best obtained
with the shoulder joint pulled distally away from the neck, and the contralateral thoracic limb
pulled caudally away from the radiographic beam. If OCD is suspected, but not apparent radio-
graphically, lateral views with pronation and supination of the limb can improve visualization of
the caudal humeral head surface and delineate a lesion not otherwise apparent (Figure 15.15; Wall
et al. 2015). In some cases, the OCD flap may be displaced or completely dislodged and relocated
within the joint space. This is challenging to evaluate radiographically unless the dislodged flap is
mineralized, which can occur with chronicity.

(A) (B) (C) SHOULDER REGION

(D)

Figure 15.15 Shoulder images of a single dog with (A-D) OCD illustrating that radiographic positioning
substantially changes the appearance of the lesion: (A) lateral, supinated radiograph demonstrating
characteristic OCD lesion of the caudal humeral head. There is flattening of the subchondral surface, with
minimal calcification of the flap; (B) lateral, neutral radiograph – note the mild lucency of the caudal humeral
head and flattening of the surface; (C) lateral, pronated view – there is very mild lucency of the caudal
humeral head but the lesion can easily be missed on this view; and (D) arthroscopic view of the OCD flap.