forearm rotation occurs around an axis connecting the center of the radial head and the fovea of the distal ulna . various treatments for malunion have been reported , but the optimal method for reduction remains controversial . we planned this study to determine numerical values indicative of healing treatment during deformation of the forearm . we therefore investigated cases in which corrective osteotomy was performed for malunion without dislocation of the elbow or wrist . our hypothesis was that increased differences between the axes of forearm and proximal radius would be associated with increased deterioration of forearm rotational motion . data from patients with corrective osteotomies for malunited forearm fractures without dislocation of the elbow or wrist were reviewed retrospectively . patient demographics were reviewed , including age , sex , and interval between injury and surgery . mean interval between initial injury and surgery was 21 months ( range , 347 months ) . mean duration of follow - up was 12 months ( range , 622 months ) . this retrospective study included eight cases ( 6 men , 2 women ) , and mean patient age was 15 years ( range , 1021 years ) . fracture type was radioulnar shaft fracture in five cases and radial shaft fracture in three cases . initial treatment of forearm fractures comprised conservative treatment in five cases and operative treatment in three cases . pre- and postoperative ranges of motion were obtained from clinical charts . we performed corrective osteotomy of the radius alone in five cases , ulna alone in one case , and both radius and ulna in two cases . intraoperatively , we attempted to restore the normal shape of both bones according to intraoperative fluoroscopic images and anteroposterior and lateral radiographs . we evaluated plain radiographic images using medical image analysis software ( rapideye ; toshiba medical systems , tochigi , japan ) . anteroposterior and lateral radiographs of the forearm were obtained using the same position of forearm rotation ( in the neutral position , if possible ) , with the elbow in 90 of flexion , and the wrist in neutral alignment . two lines were drawn : the axis of the proximal radial head ; and the forearm axis . the angle between these two lines was then measured on both lateral and anteroposterior radiographs ( fig . if the tuberosity of the radius and styloid were not on opposite sides of the bone , we determined malrotation by plain radiography . with the ulna , the coronoid process of the ulna and the ulnar styloid process are normally on opposing sides , so we used this relationship to assess malrotation of the ulna . the longitudinal ( rotational ) axis of the forearm runs from the center of the radial head proximally to the fovea of the distal ulna . the axis of the proximal radius runs between the center of the radial head and the radial neck . proximal radial tilt angle (  ) represents the angle between the rotational axis of the forearm and the axis of the proximal radius . differences in forearm rotation and in radiological assessments were analyzed using the mann - whitney u test . we evaluated plain radiographic images using medical image analysis software ( rapideye ; toshiba medical systems , tochigi , japan ) . anteroposterior and lateral radiographs of the forearm were obtained using the same position of forearm rotation ( in the neutral position , if possible ) , with the elbow in 90 of flexion , and the wrist in neutral alignment . two lines were drawn : the axis of the proximal radial head ; and the forearm axis . the angle between these two lines was then measured on both lateral and anteroposterior radiographs ( fig . if the tuberosity of the radius and styloid were not on opposite sides of the bone , we determined malrotation by plain radiography . with the ulna , the coronoid process of the ulna and the ulnar styloid process are normally on opposing sides , so we used this relationship to assess malrotation of the ulna . the longitudinal ( rotational ) axis of the forearm runs from the center of the radial head proximally to the fovea of the distal ulna . the axis of the proximal radius runs between the center of the radial head and the radial neck . proximal radial tilt angle (  ) represents the angle between the rotational axis of the forearm and the axis of the proximal radius . differences in forearm rotation and in radiological assessments were analyzed using the mann - whitney u test . mean forearm rotation increased from 81 ( range , 0135 ) preoperatively to 138 ( range , 108175 ) postoperatively . mean proximal radial tilt angle improved from 14 to 9.3 , compared to 3.3 on the normal side . postoperative rotation correlated with proximal radial tilt angle , and severe malunion affected the range of forearm rotation ( fig . 2 ) . three patients were considered to show radial malrotation and no patients displayed ulnar malrotation . mean rotation in malrotation cases was 128  17.2 , compared to 145  26.9 in the remaining cases . the forearm is composed of the radius and ulna , which are linked by the interosseous membrane and intercalated between the elbow and wrist . the forearm rotation axis runs through the center of the radial head to the ulnar head , and radial motion around the ulna results in forearm rotation . angular deformity of the forearm affects forearm rotation , so the treatment for malunion of the forearm should be provided by treating the radius and ulna as bones of a joint . although corrective osteotomy can achieve good rotation within 1 year after injury , the factors contributing to clinical results remain unclear and no reports have clarified how deformity of the axis of rotational motion affects forearm rotation . the acceptable range of deformity at initial treatment for fracture remains contentious , particularly in pediatric cases , due to good remodeling ability . our series included skeletally immature cases , but a previous report showed that in diaphyseal fractures , the distal radial epiphyseal plate realigned well only in children under 10 years of age , so our results appear reasonable . some recent papers have reported three - dimensional computed tomography ( 3dct ) and computer - assisted osteotomy for malunion . indeed , we think that malunion of the forearm should be treated in 3d , but we investigated the indicators for corrective osteotomy only on plain radiographs in consideration of radiation exposure and usability . we tried to reduce malrotation , and only three cases showed malunion and the degrees of deformity were mild . differences in each parameter were also relatively small and the small sample size could have limited the statistical power of the analyses . bones , ligaments and soft tissues would affect rotation , but the rigid body element must provide the primary effects on forearm rotation . we evaluated the results of corrective osteotomy for forearm fracture malunion using plain radiography . to improve the range of rotation we think the angle between the axis of rotation of the forearm and the axis of the proximal radius offers a useful indicator for corrective osteotomy .