Pettitt RA, Tattersall J, Gemmill T, Butterworth SJ, O'Neill TJ, Langley-Hobbs SJ, Comerford EJ, Innes JF. Small Animal Teaching Hospital, Faculty of Veterinary Science, Department of Veterinary Clinical Science, University of Liverpool, Leahurst campus, Chester High Road, Neston CH64 7TE, UK. JSAP 2009 Oct 50 10 545-8 OBJECTIVES: The aim of this study was to determine if internal fixation of the anconeus combined with a proximal ulnar osteotomy was more likely to result in fusion of the anconeus to the ulna compared with a proximal ulnar osteotomy alone. METHODS: A total of 12 orthopaedic referral clinics reviewed their clinical databases for cases of ununited anconeal process. Demographic and clinical parameters were collected along with radiographic follow-up at a minimum of four weeks. Cases treated with proximal ulnar osteotomy alone were compared with those treated with proximal ulnar osteotomy + internal fixation. Both groups were compared for background and disease variables. We tested for an association between treatment method and whether radiographic anconeal union had occurred. RESULTS: A total of 47 elbows (44 dogs) were identified. Of these, 28 cases (average age 7.6 months) were treated with proximal ulnar osteotomy (of which eight were stabilised with an intramedullary pin) alone. Nineteen cases (average age 7.1 months) were treated with proximal ulnar osteotomy + internal fixation. The two groups were not significantly different in age (P=0.638, Mann-Whitney U test). Fourteen of 28 cases with proximal ulnar osteotomy alone displayed anconeal union at follow-up compared with 16 of 19 cases of proximal ulnar osteotomy + internal fixation, and this difference was statistically significant (P=0.029, Fisher's exact test). CLINICAL SIGNIFICANCE: These data suggest that use of a lag screw to stabilise and compress the ununited anconeal process in addition to proximal ulnar osteotomy produces a better radiographic outcome. It is argued that radiographic union of the anconeus is likely to be associated with better long-term clinical outcome but further studies are required to confirm this.