Malunion of forearm shaft fractures in children is relatively uncommon. The acceptable amount of angulation is controversial. The amount of angulation depends on the location of the fracture and the age of the child. In general 15-20 degrees of malunion will usually remodel and lead to satisfactory results in children under the age of 9. However, greater angulation in older children results in lost of forearm rotation. In addition, angulation is less acceptable in the mid portion of the forearm as a bow is required for the radius to rotate around the ulna.
This article represents a case series of nine pediatric and adolescent patients who underwent corrective osteotomy for established malunion over a 10 year period. All fractures were diaphyseal without radial head dislocation, distal radial joint instability or injury to the interosseous membrane. The amount of correction varied as did the type of fixation. The average age of time of osteotomy was 7 years and the average maximum angulation prior to osteotomy was slightly greater than 30 degrees. All patients had correction of deformity within one year of the initial injury.
The surgical technique required defining the deformity utilizing plain radiographs. The authors base normal radiographic parameters on the following criteria: (1) to assess rotation in the radius, the radial tuberosity and the radial styloid are in opposite directions on the PA x-ray. In the ulna, the coronoid process and ulnar styloid are in opposite sides on the lateral x-ray. (2) the ulna is straight on lateral x-ray and has a slight varus angulation on the AP x-ray. (3) the radial bow is best seen on the frontal x-ray and the radius is straight on the lateral x-ray. Using these parameters, the angulated bone was corrected.
Reliable correction was obtained and there were no operative complications. The average gain in forearm rotation was a remarkable 102 degrees and all patients regained full supination. Two patients had residual loss of pronation.
Fracture malunion is under reported in children. Many unacceptable reductions are accepted relying on the remodeling potential during growth. However, angular deformities in the shaft of the radius and ulna greater than 30 degrees rarely remodel with restoration of full forearm rotation. The key to this paper is the early recognition of the malunion and correction within one year of surgery. Many of these patients were corrected between 3 and 7 months post-injury. Further delay complicates assessment and identification of the malunion because of the abundant callus and the remodeling that does occur over time. In addition, secondary changes can occur with growth. The authors conclude that corrective osteotomy of the forearm is recommended when functional range of motion does not return by 6 months after the initial injury.
Journal of Pediatric Orthopaedics