Many methods have been proposed for correction of distal radius malunions. However, correction of a malunion that requires simultaneous adjustment of angulation and rotation in multiple planes is difficult. This is a prospective study that measures radiographic and functional outcomes using an internal osteotomy, distraction and fixation system for severe distal radius malunions. Five patients with distal radius malunions requiring correction in multiple planes were recruited. All underwent correction using the above device. Radiographic and functional outcomes were measured pre- and post-operatively. All radiographic measurements improved. Grip and pinch strength, and the Jebsen-Taylor test showed marginal improvement. Ulnar deviation and pronation-supination improved, but wrist flexion-extension did not. The Michigan Hand Outcomes Questionnaire (MHQ) showed improvement in all domains, particularly in overall, work, aesthetic and satisfaction domains (p<0.05). However, the MHQ still demonstrated residual impairment in all domains. Corrective osteotomy using this device resulted in improvement in distal radius anatomy and in function. But not all improvements were statistically significant, and anatomy and function were not returned to baseline. In spite of residual disability, patients noted subjective improvement. This system useful for improving anatomy and function, but patients should be informed that they cannot expect to regain normal anatomy or function.