UAP

UAP or ununited anconeal process, is a developmental abnormality where the anconeal process, a bony part of the ulna, doesn't fuse with the rest of the ulna during growth.

The anconeal process is part of the ulna, the longer of the two bones of the forearm, that forms part of the caudal surface of the elbow joint. The anconal process is separated from the ulna by a growth plate and normally attaches to the ulna by about 5 months of age (or later in some giant breed dogs).

If the anconeal process does not fuse to the rest of the ulna correctly, it causes a condition called ununited anconeal process (UAP).

Clinical signs

When this part of the ulna does not fuse, the elbow joint becomes unstable, causing lameness and pain. Instability in the joint causes inflammation and eventually evolves into a degenerative joint disease. In some cases, the bone fragment floats freely in the joint, causing further discomfort and a decreased range of motion in the affected limb.

Etiology and Pathogenesis

The cause of ununited anconeal process is unknown.
The pathogenesis of the disease is unclear, but some hypotheses has been proposed such as hereditary factors, nutritional deficits/imbalances, hormonal imbalances, trauma to the physis, radioulnar incongruency (short ulna) and OCD lesion.

Diagnosis

Signalment and physical examination are often highly suggestive of the disease. UAP can be diagnosed by radiographs (X-rays) of the elbow. Sedation of the patient may be necessary to achieve the optimal positioning for diagnostic purposes. It is highly recommended to perform x-rays of both legs (in neutral, flexed and CrCd positions) since the condition may be present in both elbows and to exclude other conditions that cause elbow dysplasia, including fragmented medial coronoid process (FMCP) and osteochondritis dissecans (OCD).

Treatment
In all cases, the recommended treatment for ununited anconeal process is surgery, and it should be performed as soon as possible.
The type of surgery is based on underlying cause, radiographs, age of the patient, stage of the disease and surgeon preferences.
Surgery may involve removal of the anconeal process from the joint or it can be reattached to the ulna using screws.
In some cases, surgery on the ulna to improve elbow alignment and weight bearing is recommended.

Prognosis
In all cases, some degree of arthritis will develop in the elbow joint. Supportive treatment such as joint protective supplements, weight restriction, rehabilitation and anti-inflammatory medications may be recommended to manage progression of degenerative joint disease.
Since the condition appears to be hereditary, affected dogs should not be used for breeding. If your dog is a purebred, you should notify your breeder.