How do you find out about problems that are so rare only 300 cases have ever been reported around the world in the last 25 years? Articles like this one might help. Three cases of a particular elbow problem called congenital proximal radioulnar synostosis are reported and discussed.
Congenital means the child was born with this problem. It isn’t always obvious at first. In these three cases, the children were between the ages of seven and 13 before trauma and sudden, severe elbow pain brought them to the orthopedic surgeon’s office.
Radioulnar refers to the two bones in your forearm: the radius and the ulna. Proximal tells us the elbow is involved — specifically where the ulna and the radius meet at the elbow. These two bones also meet at the wrist. Synostosis just means there’s an abnormality in the joint. Let’s find out what kind of deformity was present with this diagnosis for these three children.
All put together, the term congenital proximal radioulnar synostosis is a failure of the two bones to separate and form a true joint at the elbow. There can be different reasons why this happens. The joint may be dislocated. In other words, the bones aren’t in the right place to allow for normal joint motion. In some cases, the top of the radial bone (called the radial head) doesn’t form properly.
Instead of being a firm, round bone that moves smoothly to allow elbow motion, it’s made up of a stiff fibrous piece of cartilage. Sometimes the shape of the radial head is all wrong — instead of looking like a miniature drum, it looks like a fat mushroom. An overgrown radial head pushes the annular ligament up and over itself resulting in a rubberband-like effect preventing full elbow extension. Any change in the size or shape of the radial head is going to mean problems with normal elbow motion.
And that’s exactly what happened with these three children: they couldn’t straighten their elbows all the way. The elbow was stuck in a flexed or bent position. How can this problem be solved? Just separating the two bones doesn’t usually do the trick. And treatment may depend on what the underlying cause is — dislocations can be relocated. Surgery is required to distract the joint and then move the elbow through its full range-of-motion, a procedure called reduction and manipulation.
For one of the children in this case series, the radial head had gotten trapped underneath an elbow ligament called the annular ligament. The surgeon was able to release the radial head by cutting the ligament and removing the radial head. This same procedure was done on another patient when the surgeon found that a layer of soft tissue was covering part of the radial head preventing normal elbow extension.
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.
In all three cases, there was a history of trauma (soccer injury, lifting, sleeping with the elbow in a fully flexed position) that contributed to the symptoms. But the congenital condition had been present since birth, so it wasn’t just the incident that caused the acute problem. It was more that the trauma triggered an underlying condition to be made known.
The authors intend to follow-up with each child long-term and report later on the results of the selected surgical treatment. Since this is such a rare condition, reports like this can be very helpful for surgeons who might only see one case in a lifetime.