Elbow dysplasia

What it is

Elbow dysplasia is not a single disease but a collective term for several developmental lesions of the elbow (articulatio cubiti) that share a common outcome: incongruity of the joint and early osteoarthritis. The recognised components are:

• Medial coronoid disease (fragmented medial coronoid process of the ulna), the most frequent.
• Osteochondrosis / osteochondritis dissecans (OCD) of the medial part of the humeral condyle.
• Ununited anconeal process (UAP), a failure of the anconeal process to fuse with the ulna.
• Elbow incongruity, a step between the articular surfaces of radius and ulna (short radius or short ulna).

The causes are multifactorial: genetics (it is heritable), rapid growth, excess energy and calcium in the diet, and asynchronous growth of the radius and ulna.

Who it affects

Young, fast-growing dogs of medium, large and giant breeds: Labrador and golden retriever, Rottweiler, Bernese mountain dog, German shepherd (typical breed for UAP), Newfoundland, chow chow. Signs usually start between 4 and 10 months of age, although some dogs are first presented as adults with established osteoarthritis. It is often bilateral.

Anatomy involved

The elbow is a composite joint between the humeral condyle, the trochlear notch of the ulna and the head of the radius. The medial coronoid process of the ulna and the medial part of the humeral condyle carry a large share of the load; when the radius and ulna do not form a smooth joint surface, that region is overloaded and the coronoid cartilage and subchondral bone fragment. The anconeal process, which locks into the olecranon fossa of the humerus during extension, has a separate ossification centre that normally fuses with the ulna by about 5 months; if it does not, it stays loose.

Clinical signs

Intermittent or persistent thoracic limb lameness that worsens after exercise and after rest, stiffness on rising, outward rotation of the paw with the elbow held close to the body, pain on hyperextension and flexion of the elbow, joint effusion palpable between the lateral epicondyle and the olecranon and, in chronic cases, reduced range of motion and crepitus. Bilateral cases may show a short, stilted gait rather than obvious lameness.

Diagnosis

• Radiographs: mediolateral (neutral and flexed) and craniocaudal views of both elbows. The flexed lateral view shows UAP. Medial coronoid disease is often not visible directly; indirect signs include sclerosis of the ulna at the base of the coronoid, osteophytes on the anconeal process and the medial epicondyle, and incongruity.
• CT: the most useful imaging method to see coronoid fragments and incongruity.
• Arthroscopy: confirms and treats cartilage lesions and fragments.
• Screening: radiographic grading schemes (IEWG, OFA, FCI) are used to select breeding animals.

Treatment

Removal of the coronoid fragments or OCD flap, usually by arthroscopy, followed by weight control, controlled exercise, physiotherapy and NSAIDs. UAP is treated by lag-screw fixation of the process, often combined with a proximal ulnar osteotomy, or by its removal. Corrective osteotomies of the ulna or radius are used for marked incongruity. Surgery does not stop osteoarthritis, so long-term management of the arthritic joint is part of the plan. The only prevention is to breed from unaffected dogs and to avoid overfeeding during growth.