Boutonnière deformity is an injury to the tendons in your fingers that usually prevents the finger from fully straightening. The result is that the middle joint of the injured finger bends down, while the fingertip bends back. This is the characteristic shape of a boutonnière deformity. Unless this injury is treated promptly, the deformity may progress, resulting in permanent deformity and impaired functioning.
There are several tendons in your fingers that work together to bend and straighten the finger. These tendons run along the side and top of the finger. The tendon on the top of the finger attaches to the middle bone of the finger (the central slip of tendon). When this tendon is injured, the finger is not able to be fully straightened.
Causes of Boutonniere Deformity
Boutonnière deformity is generally caused by a forceful blow to the bent finger.
It also can be caused by a cut on the top of the finger, which can sever the central slip from its attachment to the bone. The tear looks like a buttonhole (“boutonnière” in French). In some cases, the bone actually can pop through the opening.
Boutonnière deformities may also be caused by arthritis. About one third of all people with rheumatoid arthritis also have fingers with boutonnière deformities.
Symptoms of Boutonniere Deformity
Signs of boutonnière deformity can develop immediately following an injury to the finger or it may develop seven to 21 days later.
- The finger at the middle joint cannot be straightened and the fingertip cannot be bent.
- Swelling and pain on the top of the middle joint of the finger.
- Splints: A splint will be applied to the finger at the middle joint to straighten it. This keeps the ends of the tendon from separating as it heals. It is important to wear the splint for the recommended length of time-usually 6 weeks for a young patient and 3 weeks for an elderly patient. Following this period of immobilization, you may still have to wear the splint at night.
- Exercises: Your physician may recommend stretching exercises to improve the strength and flexibility in the fingers.
- Protection: If you participate in sports, you may have to wear protective splinting or taping for several weeks after the splint is removed.
People with boutonnière deformity caused by arthritis may be treated with oral medications or corticosteroid injections as well as splinting.
While nonsurgical treatment of boutonnière deformity is preferred, surgery is an option in certain cases, such as when:
- The deformity results from rheumatoid arthritis.
- The tendon is severed.
- A large bone fragment is displaced from its normal position.
- The condition does not improve with splinting.
Surgery can reduce pain and improve functioning, but it may not be able to fully correct the condition and make the finger look normal. If the boutonniere deformity remains untreated for more than 3 weeks, it becomes much more difficult to treat.