Faculty of Veterinary Science, University of Liverpool, Liverpool, UK.

Ununited anconeal process (UAP) is one of a group of diseases known as elbow dysplasia. However, unlike the other diseases of this group, it occurs primarily in the German Shepherd dog. Published evidence would suggest that the disease is associated with delayed growth of the ulna causing increased tension within the elbow joint [1]. The anconeal process develops as a separate centre of ossification in affected breeds and it should fuse to the proximal ulna by 18 weeks of age; persistence of a radiolucent line between the anconeus and the olecranon, beyond 18 weeks is suggestive of ununited anconeal process. The realization that a short ulna contributes to the disease has significantly changed the surgical approach to this condition.

DIAGNOSIS
Dogs with ununited anconeal process usually present between 5 and 6 months of age. Although German Shepherd dogs are most commonly affected, the Bassett Hound and a variety of medium-large breed dogs may suffer this condition. Unilateral thoracic limb lameness with pain on full extension of the joint are typical findings; joint effusion may be prominent.

TREATMENT
Traditional treatment for this condition has been removal of the ununited anconeus. However, this destabilizes the joint and tends to result in progressive osteoarthritis [2] and poor function (HR Denny, personal communication). Fixation of the anconeal process is also reported using lag screws [3] or screw plus pin [4]. Results seem satisfactory but fixation alone can result in implant failure.

Ulna osteotomy has also been advocated as a logical extrapolation of the data on etiopathogenesis [1]. Ulna osteotomy alone can result in spontaneous fusion of the anconeus [1,5] although it appears that the technique is more successful in younger dogs.

Ulna osteotomy combined with fixation appears to give the most predictable results [4,5] and this is the author’s preferred technique (Figures 1–3).

Figure 1. Ununited anconeal process.
 

Figure 2. Use of an AO aiming device for accurate screw position.
 

Figure 3. Immediate postoperative radiograph (far left) and 8-week follow-up radiograph (near left) showing fusion of the anconeal process.
 
 

References
1. Sjostrom L, Kasstrom H, Kallberg M. Ununited anconeal process in the dog - Pathogenesis and treatment by osteotomy of the ulna. Vet Comp Orthopaedics Traumatol 1995; 8:170-176.
2. Roy RG, Wallace LJ, Johnston GR. A retrospective long-term evaluation of ununited anconeal process excision on the canine elbow. Vet Comp Orthopaedics Traumatol 1994; 7:94-97.
3. Fox SM, Burbidge HM, Bray JC, Guerin SR. Ununited anconeal process: Lag-screw fixation. J Am Anim Hospl Assoc 1996; 32:52-56.
4. Meyer-Lindenbeg A, Fehr M, Nolte I. Short- and long-term results after surgical treatment of an ununited anconeal process in the dog. Vet Comp Orthopaedics Traumatol 2001; 14:101-110.
5. Turner BM, Abercromby RH, Innes J, McKee WM, Ness MG. Dynamic proximal ulnar osteotomy for the treatment of ununited anconeal process in 17 dogs. Vet Comp Orthopaedics Traumatol 1998; 11:76-79.
6. Krotscheck U, Hulse DA, Bahr A, Jerram RM. Ununited anconeal process: lag-screw fixation with proximal ulnar osteotomy. Vet Comp Orthopaedics Traumatol 2000; 13:212-216.
Last updated: 13-Jan-2007.