Radial Tunnel Syndrome is entrapment of the Posterior Interosseous Nerve (PIN), the major branch of the Radial Nerve, near the outside of the elbow. Radial Tunnel Syndrome leads to pain on the outside of the elbow, and its symptoms are often confused with the much more common Tennis Elbow. While the pain of Radial Tunnel Syndrome can radiate down the forearm, unlike most other nerve compressions there is no numbness or tingling involved. Similar to other nerve compressions, the pain of Radial Tunnel Syndrome often occurs at night.
The diagnosis of Radial Tunnel Syndrome is best made with a physical examination by an experienced Orthopedic Upper Extremity or Elbow Surgeon. While there are many tests alleged to help differentiate Radial Tunnel Syndrome from Tennis Elbow, the 2 most accurate factors that help diagnose Radial Tunnel Syndrome are 1) The point of maximum tenderness, 2) Response to a diagnostic injection. Nerve studies are notoriously insensitive for Radial Tunnel Syndrome, and it’s uncommon that they help with this diagnosis.
The point of maximum tenderness for Radial Tunnel Syndrome is over the Radial Tunnel, which is located on the forearm close to the elbow, 2 inches away from the tendons affected by Tennis Elbow. A diagnostic injection is probably the best way to make the diagnosis of Radial Tunnel Syndrome. Diagnostic injections are analogous to a dentist trying to determine which tooth is causing mouth pain. If numbing a certain tooth resolves the pain, then that’s the painful tooth. If numbing a tooth resolves part of the pain, then part of the pain is coming from that tooth and part is coming from somewhere else.
Following a diagnostic injection into the Radial Tunnel, the PIN will not work for 3-4 hours, making it difficult to use the hand because wrist and finger extension will be temporarily lost. If there’s any question as to whether or not both Tennis Elbow and Radial Tunnel Syndrome are present, it’s best to inject the Tennis Elbow area first, as the lack of wrist extension following the Radial Tunnel injection will make it difficult to perform the physical examination for Tennis Elbow. If the elbow pain is resolved following a Radial Tunnel injection, then the diagnosis of Radial Tunnel Syndrome is confirmed.
For treatment, Radial Tunnel Syndrome is usually “observed” for 3 months. The diagnostic injection also contains some steroid in it, which can potentially reduce any inflammation compressing the PIN. If the Radial Tunnel Syndrome is still problematic after 3 months from the onset of symptoms, a Radial Tunnel Release can be considered.
Radial Tunnel Release is an outpatient procedure that releases the tight structures that are compressing the PIN. These can include fibrous bands, tight tendon edges, or large venous varicosities. If Tennis Elbow is also present, it can be treated at the same time. Following a simple Radial Tunnel Release, no immobilization is necessary and motion exercises can be started after a few days.
The wound should be kept clean and dry for 3 days, at which point showering can begin. The wound should not be submerged underwater until the stitches are removed, which is at the first post-operative visit at 2 weeks. The wound can be covered by a light dressing or Band-Aids until then. It’s probably best to avoid heavy activity and strengthening for a month following Radial Tunnel Release.
Following Radial Tunnel Release, the PIN can take 18 months to fully recover from its compression. In my experience, the vast majority of patients experience significant pain relief following Radial Tunnel Release. However, it is not uncommon to have some residual pain of roughly 20% following Radial Tunnel Release. In other words, most patients get at least 80% pain relief, although not always 100% relief. However, an 80% decrease in pain is usually much appreciated.