Post-traumatic radioulnar synostosis after forearm fracture osteosynthesis.

One hundred sixty-seven forearm fractures treated with plate osteosynthesis were analyzed for synostosis occurring between the radius and the ulna. Eleven cases (6.6%) were found, in 7 of which both bones of the forearm had been fractured, while the other 4 were cases of isolated radial or ulnar fracture. Overall there were 89 cases of fracture of both bones; of the 65 cases treated utilizing the two-incision approach, cross-union was seen in only 1, while in a comparable group (12 cases) in which the fractures were stabilized using the Boyd approach, there were 5 synostoses. In 38 cases of isolated ulna fracture, only 2 synostoses were seen one associated with severe soft-tissue trauma and the other arising after treatment with a modified Boyd approach. Among 40 isolated radial fractures, 2 radioulnar synostoses occurred, one in an open fracture and the other after fixation via the Boyd approach. These results emphasize the importance of using two approaches for fractures of both forearm bones. The highest risk of post-osteosynthetic synostosis appears to be in fractures of the proximal third of both radius and ulna.