Fragmented Medial Coronoid Process (FMCP), Fragmented Coronoid Process (FCP), Ununited Anconeal Process (UAP), Radioulnar Incongruity, Elbow Incongruity, Osteochondrosis of the Elbow
Canine elbow dysplasia (ED) is a disease of the elbows of dogs caused by growth disturbances in the elbow joint. There are a number of theories as to the exact cause of the disease that include defects in cartilage growth, trauma, genetics, exercise, diet and so on. It is likely that a combination of these factors leads to a mismatch of growth between the two bones in the fore leg located between the elbow and the wrist (radius and ulna). If the radius grows more slowly than the ulna it becomes shorter leading to increased pressure on the medial coronoid process of the ulna (Figure 1). This in turn can cause damage to the cartilage in joint and even fracture of the tip of the coronoid process, which damages the medial compartment (side closest to the body) of the joint. Less commonly, if the ulna grows too slowly then the radius pushes the upper arm bone (humerus) against the anconeal process, which can then lead to failure of the anconeal process to attach to the ulna at maturity. It is believed that the mismatch in growth between the radius and ulna may sometimes only occur during a puppy’s growth, but it may also persist when the pup has finished growing.
Signs and Symptoms:
Elbow dysplasia is most often seen in large to giant breed dogs, particularly Labradors, Golden Retrievers, German Shepherds, and Rottweilers, but can occur in most breeds of dog. Different breeds have predispositions to different forms of the disease, so that ununited anconeal process (UAP) is largely a problem of German Shepherds, medial compartment disease (medial coronoid injury) is seen in many other breeds and sight hounds are free of the disease.
Unfortunately once the elbow joint has been damaged through either cartilage loss, the presence of medial coronoid fragments or an ununited anconeal process, a vicious circle of inflammation and further cartilage damage begins. Ultimately this causesprogressive arthritis of the elbow joint leading to pain and loss of function.
Dogs affected by elbow dysplasia often show signs from an early age, typically from 5 months on, but some may first be diagnosed after 4–6 years. Affected dogs develop a front limb lameness that typically worsens over a period of weeks to months. Lameness is usually worse after exercise and typically never completely resolves with rest. Often both fore legs are affected, which can make detection of lameness difficult, as the gait is not asymmetric. When both elbows are involved the dog usually becomes unwilling to exercise for long periods or may even refuse to complete a walk.
Diagnosis of elbow dysplasia is usually performed with a combination of clinical examination and x-rays. Usually the dog has pain on fully bending or extending the elbow and often your veterinarian will want to watch your dog walk or trot to detect any lameness. X-rays will typically shows signs of arthritis but may also show the presence of small bone fragments in the joint or an ununited anconeal process (Figures 2 and 3). Your veterinarian may also choose to refer you to a specialist veterinary surgeon for more advanced diagnostic procedures to be performed. This may include CT scans, MRI scans, or arthroscopy (Figures 4 and 5).
Treatment depends on the severity of the disease in the elbow. In many cases surgery is recommended, but your veterinarian may recommend medical management if the problem is very mild or so severe that the joint is not likely to benefit from routine surgery. Treatment can be divided into the correction of a joint step between the radius and ulna if present, and treatment of any other joint damage. Often surgery is best performed arthroscopically, but conventional open surgery can also be done. Depending on the individual dog’s elbow problem surgery may involve:
- Correction of joint step; is usually done by cutting the ulna to re-establish elbow congruence.
- Removal of any coronoid fragments and removal of loose cartilage (Figure 6)
- Surgical alteration of the elbow joint to shift weight away from damaged areas (Figure 7)
- Reattachment or removal of an united anconeal process of the medial joint compartment (Figure 8)
- Joint replacement if the elbow is severely diseased
Aftercare and Outcome:
Obviously the aftercare will depend on the type of surgery performed, and your veterinarian will advise you of exactly what is required. In general your dog will need to be quiet and confined for a period of time, usually from 2–6 weeks or more.
The outcome will vary between dogs, but in general the more mild the disease and the earlier it is treated, the better the long-term outcome. Most dogs will benefit from surgical treatment even if disease is more advanced, but unfortunately once arthritis is well established it will slowly progress regardless of any treatment. The aim is to slow the progression of arthritis and prolong the patients’ use of the elbow.
Content by the American College of Veterinary Surgeons