PURPOSE: Ulnar shortening osteotmy is a common operation for the treatment of ulnar impaction syndrome. The purpose of this study was to evaluate factors that may affect the occurrence of distal radioulnar joint (DRUJ) arthritis after ulnar shortening osteotomy. METHODS: From September 2005 to August 2012, we performed 81 ulnar shortening osteotomies for ulnar impaction syndrome, and evaluated occurrence or deterioration of DRUJ arthritis in 58 patients with a minimum follow-up of 1 year. We analyzed potential factors that may affect the occurrence of DRUJ arthritis, such as, age, sex, hand dominance, pre- and postoperative ulnar variance, preexisting DRUJ arthritis, types of radial sigmoid notch, amount of ulnar shortening, and follow up period. RESULTS: DRUJ arthritis occurred or deteriorated in 32 out of the 58 patients. Regression analysis indicated a significant correlation between the type of radial sigmoid notch (type 1) and DRUJ arthritis. Other factors were not found to be correlated with occurrence or deterioration of DRUJ arthritis. CONCLUSION: This study suggests that patients with type 1 radial sigmoid notch (ulnar inclination of more than 10 degrees) are more likely to develop DRUJ arthritis after ulnar shortening osteotomy.