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  • Ununited anconeal process

Certain breeds are predisposed to UAP. These include German Shepherd dogs and Wolfhounds, and sometimes UAP occurs because the ulna growth is retarded because of growth plate issues at the bottom of the forearm which (amongst other things) causes the anconeal process to impinge on the back of the humerus.

The UAP can be addressed in one of two ways. It can be treated as a fracture and fixed with metal work or it can be removed.

Fixation presents some problems:

The fragment is small

It is soft bone

It doesn’t always “fit” very well onto the adjacent ulna

There is only room for one implant so the fragment can move on the implant to some degree

Implant placement requires very accurate drilling

If the implant is too long, it will penetrate into the joint

The ulna often needs to be cut to prevent the fixed UAP from impinging on the humerus which would predispose to fixation failure (see separate article on dynamic ulna osteotmy

The patient (a puppy) needs to be strictly confined in the early post-operative period.

Removal of the fragment has some advantages:

It is a cheaper and easier procedure

There is no metalwork to create technical problems

There is no need to cut the ulna

The need for exercise restriction post-op is less critical

The outcome is more predictable.

On the other hand, the keel stability usually provided by the AP is missing if the fragment is removed, and the missing stability  must then be provided by the development of fibrosis and thickening of the periarticular structures.

In both scenarios, some degenerative joint disease, commonly called osteoarthritis, is to be expected in the long term.

25th June 2014

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