Forearm rotation occurs around an axis connecting the center of the radial head and the fovea of the distal ulna. The purpose of the present study was to demonstrate the usefulness of the difference between forearm and proximal radial axis in the treatment of malunited forearm fractures. We reviewed the results of eight corrective osteotomies for malunited fractures of the forearm without dislocations of the wrist or elbow. Subjects were 6 men and 2 women (mean age, 15 years
range, 10-21 years). Corrective osteotomy was performed at the fracture site. Preoperatively and at final follow-up, the arc of forearm rotation was recorded and anteroposterior and lateral X-rays were taken. Proximal radius tilt was defined as the angle between the rotational axis of the forearm and the axis of the proximal radius. Corrective osteotomy improved proximal radius tilt in all cases. Three patients were considered to have malrotation. Postoperative rotational arc correlated with proximal radial tilt (r = -0.83). No significant difference in rotational arc was evident between malunited cases and the remaining cases. To improve forearm rotation, corrective osteotomy should be planned to minimize proximal radius tilt.