Elbow Dysplasia

The elbow is made up from several components, and is one of the most complicated joints in the body. Elbow dysplasia ("dysplasia" meaning “abnormal in form”) normally presents in young, fast growing large breed dogs and also chondrodysplastic breeds (basset hounds, dachshunds, etc). The patient is usually 4-8 months of age, but occasionally older.

Elbow dysplasia is normally classified as one of the following; ununited anconeal process (UAP), fragmented medial coronoid process (FMCP), and osteochondrosis dissecans of the medial humeral condyle (OCD). See below.

Fragmented medial coronoid process (FMCP)

FMCP is the most common type of elbow dysplasia, and certain breeds, are especially susceptible to this developmental condition (strong hereditary component). FMCP may rise from different pathophysiologies. One of the most frequent cause is asynchronous forearm growth, whereby the radius is lagging behind the growth of its ulnar and humeral counterpoints, causing an incongruous joint surface, as is frequently seen in young and fast growing large and giant breed dogs. FMCP occurs bilaterally in 26 percent of affected Labrador retrievers. Other causes of FMCP are Osteochrondrosis (see below) and trochlear notch malformation.

Clinical features include lameness and gait abnormalities, with reduced limb stride and abduction. The limb may also adopt an abnormal conformation, with internal rotation of the elbow with compensatory supination of the carpus and pes in an attempt to reduce weight bearing on the affected area. Joint effusion and crepitus may be present, and loss of range of movement (ROM) is likely, especially loss of extension. End result without intervention is joint instability and osteoarthritis (OA) although it appears that onset of OA is ultimately inevitable.

Surgical management may either be removal of the fragment, a low ulnar ostectomy or a dynamic ulnar osteotomy, the latter two normally performed concurrently with fragment removal. Post-operative care and physiotherapy may depend on the surgery performed, length of sequelae and the severity of OA. Appropriate analgesic medication such as NSAIDs is important to facilitate pain free rehabilitation, and may be used prior to each physiotherapy session.

Ununited Anconeal Process (UAP)

The anconeal process is a relatively small bony projection which forms part of the ulna at the back of the elbow joint. It is critical to the formation of the elbow joint, providing stability especially when the leg is extended. In very young animals this part of the ulna is not fused with the rest of the ulna; they fuse by approximately 24 weeks of age. Sometimes, during the ossification (unifying) process the anconeal process fails to fuse, forming a separate bone, and this is called an ununited anconeal process. Dogs with UAP will develop lameness after this time. German Shepherds, Basset Hounds, and St Bernards have the highest incidence rates of UAP. It is considered a genetically transmitted disorder and affected individuals should not be bred.

Osteochondrosis Dessicans (OCD)

OCD can occur in many joints, but when it occurs in an elbow it most commonly is on the lower, inner aspect of the humerus (medial humeral condyle). In essence OCD is a vertical break in the articular cartilage of the humerus, which can lead to a flap (either attached or loose) of cartilage within the joint. This flap leads to irritation and degeneration within the joint as a result of an inflammatory process, and this may ultimately lead to osteoarthritis of the affected joint.