Computer-Assisted Distal Radius Osteotomy George S. Athwal, MD, FRSC, Randy E. Ellis, PhD, Carolyn F. Small, PhD, David R. Pichora, MD, FRSC, Kingston, Canada Purpose: To establish the accuracy, precision, and clinical feasibility of a novel technique of computer-assisted distal radius osteotomy for the correction of symptomatic distal radius malunion. Methods: Six patients underwent a computer-assisted distal radius osteotomy and were fol- lowed-up for an average of 25 months. Objective radiographic measurements and functional outcomes, as measured by clinical examination including grip strength and range of motion, and Disability of the Arm, Shoulder and Hand (DASH) questionnaires, were used. Results: The mean radiographic parameters included an increase of radial inclination to 21° from 12° (normal, 23°). Dorsal and volar tilt (malunion) were corrected to 9° from -30° and 21°, respectively (normal, 10°). Ulnar variance was corrected to 1.9 mm from 7.5 mm (normal, +1.5 mm). Normal is defined as the average of the contralateral limb radiographs. The mean clinical outcome measures at an average of 25 months included a DASH global score of 14, a DASH individual item average score of 1.6, and an average affected side grip strength of 79% when compared with the unaffected side. Conclusions: The results of the computer-assisted technique were comparable with published results of traditional non– computer-assisted opening wedge osteotomy techniques. This technique allows a surgeon to accurately and precisely recognize and correct 3-dimensional deformities of the distal radius including axial malalignment (supination). The technique has the added benefit of reducing radiation exposure to the patient and surgical team because fluoroscopy is not used during the procedure. Additional benefits of the computer-assisted technique include the ability to perform multiple surgical simulations to optimize the alignment plan, and it serves as an excellent teaching tool for less-experienced surgeons. (J Hand Surg 2003;28A:951–958. Copyright © 2003 by the American Society for Surgery of the Hand.) Key words: Malunion, osteotomy, radius fracture, computer-assisted surgery. Fractures of the distal radius constitute about one sixth of all fractures seen in the emergency room. 1 Current treatment methods for distal radius fractures lead to satisfactory results in the majority of patients. Malunion, however, is a recognized complication and usually can be prevented by appropriate treat- ment of the original fracture. McGrory and Amadio 2 reported that the incidence of distal radius malunions in fractures treated by simple cast immobilization ranged from 12% to 70% and the pooled mean was 23%. The incidence after primary surgical treatment ranged from 0% to 33% (pooled mean, 10.6%). Un- fortunately malunion may cause alterations in align- ment, kinematics, and load transfer across the wrist. Patients may experience pain, arthrosis, reduced range of motion, reduced grip strength, carpal insta- bility, cosmetic deformity, late neuropathy, or tendon rupture. 2–6 From the Division of Orthopaedic Surgery, Department of Surgery, the School of Computing, and the Department of Mechanical Engineering, Queen’s University, Kingston, Canada. Received for publication February 15, 2002; accepted in revised form June 26, 2003. Supported in part by the Natural Sciences and Engineering Research Council of Canada, the Ontario Research and Development Challenge Fund, and the Institute for Robotics and Intelligent Systems. No benefits in any form have been received or will be received by a commercial party related directly or indirectly to the subject of this article. Reprint requests: D. R. Pichora, MD, FRCSC, Division of Orthopaedic Surgery, Kingston General Hospital, 76 Stuart St, Kingston, Ontario, Canada K7L 2V7. Copyright © 2003 by the American Society for Surgery of the Hand 0363-5023/03/28A06-0010$30.00/0 doi:10.1016/S0363-5023(03)00375-7 The Journal of Hand Surgery 951