An ununited anconeal process (UAP) is a disorder of the elbow. It occurs when a small bony projection called the anconeal process fails to unite and fuse with the ulna, the smaller of the bones making up the foreleg. The anconeal process is critical for the proper formation of the elbow joint. It provides stability to the joint, especially when the leg is extended.
Generally, the anconeal process and ulna fuse by 24 weeks of age. After this age, a lameness will develop if the anconeal process remains separated. German Shepherds, Basset Hounds, and Saint Bernards have the highest incidence of UAP. It is considered a genetically transmitted disorder and affected individuals should not be bred.
What are the symptoms?
This condition can affect one or both elbows. The dog will be lame on the involved limb(s). Additionally, the elbow may appear swollen and painful, especially when the leg is extended. Most cases are seen in young dogs between six and twelve months of age.
What are the risks?
Quite commonly, without treatment, the joint will become severely painful and useless. The dog will walk on three legs, or not at all if both elbows are involved. The condition worsens with age, with severe arthritic changes occurring.
Dogs with an ununited anconeal process may have other abnormalities of the bones in the elbow joint. Sometimes a flap or piece of cartilage may become dislodged from the bone. This is called osteochondritis dissecans.
What is the management?
Radiographs (x-rays) are needed to confirm the diagnosis. Once confirmed, surgery is generally recommended. Several surgical procedures can be used to either attach the anconeal process with screws, or remove it completely. Even with surgery, the function of the elbow joint is usually compromised to some degree.