Review of Carpal Boss in the Wrist

In this article, orthopedic hand surgeons from Brown University in Rhode Island review an uncommon hand condition called carpal boss. Carpal boss refers to a bony bump on the back of the hand between the index and middle fingers near the wrist. It is an extra growth of bone that forms before birth or as a result of degenerative arthritis.

It may be painful with swelling and aching where the bone sticks up. Bending the wrist shows the bump more clearly. Some patients report an injury. Others notice it develops after playing golf or racquet sports. Older adults and/or people who have jobs with repetitive tasks are also at increased risk for this problem.

Carpal boss is easily mistaken for a ganglion cyst or tumor. But it has a much harder consistency than cysts or tumors. Sometimes, a cyst or bursa forms over the bony bump making the diagnosis more challenging.

There are some clinical tests that can be done but they aren't conclusive. These include the malalignment and stress tests. Both of these tests are described in detail. The test results are helpful but don't make the final diagnosis. X-rays are really needed to confirm the diagnosis. In more complicated cases, advanced imaging such as MRIs, CT scans, or angiography may be needed.

Symptoms that don't go away with hand therapy may require surgery. The extra bone can't just be cut out or it will grow back. The surgeon must find all areas of sclerosis (hardening) around the bone and cartilage and remove them. This is called a wide wedge excision.

Care must be taken to remove only the necessary amount of bone to prevent destabilization of the wrist. Joint instability can be treated with a wrist fusion. This procedure may reduce the painful symptoms but can result in loss of motion and function.

More studies are needed to find the best treatment for carpal boss. Identifying who would benefit from surgery and reducing complications after surgery are important research goals.

Reference: 

Min J. Park, MMSc, et al. The Carpal Boss: Review of Diagnosis and Treatment. In Journal of Hand Surgery. March 2008. Vol. 33A. No. 3. Pp. 446-449.

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