Mid-ulnar Ostectomy in the Treatment of Fragmented Coronoid Process and Radio-ulnar Incongruence in Young Dogs

Introduction
Radio-ulnar incongruence (RUI) is often seen in combination with a fragmented coronoid process (FCP) in large breed dogs. A proximal osteotomy of the ulna is the traditional treatment for RUI but is associated with high morbidity. The objective of this prospective study was to evaluate the short-term and long-term clinical effects of a mid-ulnar ostectomy (MUO) in young patients with FCP and RUI.

Materials and methods
Dogs under 1 year of age presenting with arthroscopic evidence of FCP and RUI were treated with arthroscopic fragment removal and MUO (2007-2012). Clinical and radiographic reevaluation was performed at 1 to 3 months (short-term) and at more than 6 months (long-term) postoperatively.

Results
Fifty-four dogs (98 elbows) met the inclusion criteria. Pre-operative mean lameness score was 2 (range 1-4 on a 5-point scale). Postoperatively, all owners reported only mild discomfort for a mean of 10 days (0-28). As early as 4 weeks postoperatively, radiographic evidence of a caudolateral shift of the proximal ulnar fragment was present. Short-term lameness scores significantly decreased to a mean of 1 (range 0-3) (p<0.001) as did long- term scores (range 0-3) (p<0.001). Eighty-seven percent (87%) of dogs returned to normal activity.

Discussion
Combining arthroscopic FCP removal with MUO in young dogs with FCP and RUI allows the proximal ulna to shift laterally and caudally thus creating a larger joint space at the medial compartment. Both short- and long-term follow-up examinations showed a significant decrease in lameness score compared to the pre-operative situation. When compared to the proximal osteotomy, the MUO appears to have a much lower morbidity. Based on the results of our study, MUO is indicated as an ancillary procedure to arthroscopic removal of FCP in young dogs with FCP and RUI.