This particular elbow problem comes about when some change in the normal anatomy alters the way the elbow moves. The ulna and radius may be stuck together preventing normal movement between the two bones at the elbow. Most often, the radial head has gotten trapped under the annular ligament. The annular ligament is a thin, broad fibrous layer that covers the front surface of the elbow joint.
The radial head is the top part of the radial bone (one of two bones in the forearm that makes up the elbow joint). Anything that changes the alignment of the annular ligament and the radial head can contribute to the elbow problems associated with congenital radioulnar synostosis. That could be a dislocated radial head or trapped radial head.
Just separating the two bones doesn’t usually do the trick. And it may depend on what the underlying cause is — dislocations can be relocated. Surgery is required to move the elbow through its full range-of-motion, a procedure called manipulation.
In very young children, when the radial head is trapped underneath the annular ligament, the problem may correct itself with a little time and patience. But in the older child who is less flexible and more developed, the surgeon may have to release the radial head. This is done by cutting the ligament and removing the radial head. Removing the top of the radial bone is advised because it prevents future elbow problems like pinching against the capitellum, another bony part of the elbow.
An open procedure is advised rather than an arthroscopic approach because of the way the soft tissues all blend together around the elbow. It can be very difficult for the surgeon to separate the tissues in order to release the annular ligament. An open incision makes it possible to see how the tissue is formed all the way around the elbow and do a thorough job removing the problem tissue.