Is a Carpal Boss Serious?

Carpal boss or bossing is the term given to a bony lump on the back of the hand. This protuberance typically occurs at the junction of the long hand bones (metacarpals) and the small wrist bones (carpals). A carpal boss is most commonly located at the middle or index carpometacarpal joint. The word boss comes from the French word bosse, which means a bump or swelling.

Carpal bossing is due to an osseous (bony) formation at the base of the metacarpal bones of the hand. It must be differentiated from other, more common wrist conditions such as:

• Wrist ganglions
• Tendonitis
• Fracture

A carpal boss is not a cancer or a tumor. While very rare bone tumors can occur in the hand, your healthcare provider should be able to differentiate a carpal boss from something more concerning.

Signs and Symptoms of a Carpal Boss

A carpal boss is typically asymptomatic. Most people complain of symptoms related to a carpal boss after they physically bump or hit the prominence on the back of the wrist. This type of trauma can cause irritation around the carpal boss.

Other symptoms associated with a carpal boss can be attributed to complications such as secondary osteoarthritis, bursitis, ganglion formation, or extensor tendon slipping or impingement. Sometimes, you may experience a tendon-snapping sensation as it moves over the bump.

If a person is asymptomatic they may simply not like the cosmetic appearance of the bump on their hand and look to get it removed surgically.

What Causes a Carpal Boss?

Experts don't know the exact cause of carpal bossing. It seems to be related to the following conditions:

• Repetitive wrist motions
• Osteoarthritis
• Joint trauma
• Congenital bone spurs (i.e., os styloideum)
  

How a Carpal Boss Is Diagnosed

Your primary care healthcare provider may look further into the bump, or you may be referred to a hand specialist. If you are having pain and swelling, your healthcare provider will want to rule out more common wrist conditions such as:

• Wrist ganglions
• Tendonitis
• Fracture

A physical exam, your history of when the bump appeared, and your symptoms are used to make the diagnosis. X-rays are typically performed to confirm the diagnosis of a carpal boss. Depending on your symptoms, other imaging or tests include electromyography (which measures muscle response to nerve stimulation), ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI)..

Treatment

Most often, carpal bossing is a problem that can simply be watched—with no specific treatment. If it is painful or inflamed, anti-inflammatory analgesics such as ibuprofen may be suggested. Other forms of conservative management for symptomatic bossing include immobilization with a splint, corticosteroid injections, shock wave therapy, and physiotherapy.

In cases where the condition is causing significant symptoms, a surgical procedure, most commonly a wedge resection, can be done to remove the excess bone and damaged tissues.

Surgery

Surgery for carpal bossing is usually done under local or regional anesthetic. An incision is made on the back of the hand, and the bump and any swollen tissue around it are removed. Depending on the surgery's extent, you can typically use your hand for normal activity after a few days and return to work in a week or two.

Some surgeons will also fuse the bone at the joint where the spur is located to prevent a recurrence of the condition. There is conflicting literature as to how likely it may be that the bump returns after excision, but it is possible. However, excision has risks of joint instability as well as a common risk of infection and scarring.

Summary

A carpal boss is a bony lump on the back of the hand. It may have no symptoms other than its appearance, but it can become irritated if subjected to trauma. Its causes are generally unknown. It is diagnosed with an X-ray. It usually needs no specific treatment except for anti-inflammatories if it becomes irritated.