Boutonnière deformity (also called buttonhole deformity) is a medical condition affecting the tendons of the finger which causes the finger to appear crooked, the middle joint bent down toward the palm and the end joint bent backwards. Boutonnière deformity is often the result of a blunt force injury to the finger, but can also be caused by chronic inflammation due to rheumatoid arthritis or a penetrating laceration. In rare cases, a mild Boutonnière deformity may be congenital (present at birth).
The tendon damage involved in Boutonnière deformity causes the affected finger to be unable to fully extend. Prompt treatment of the finger deformity is key to successfully regaining full range of motion.
How Boutonnière Deformity Occurs
Finger flexion (bending) and extension (straightening) is a complex process dependent on tendons that are located on the tops and sides of the fingers. These tendons, which are attached to the finger bones, stretch and contract to allow the fingers to straighten and bend.
Tendons in the finger include:
- Flexor tendons: Located on the palm side of each finger and pull the finger down to bend
- Extensor tendons: Attached to the bone in several places on the back side of each finger and pull the finger into a straightened position
Each finger is made up of three bones called phalanges (phalanx singularly). The fingertip is the distal phalanx, the middle phalanx is in the center, and the proximal phalanx is located next to the hand. Extensor tendons attach to the middle and distal phalanges. The area where the extensor tendon attaches to the middle phalanx is called the central slip. Damage to the central slip is what causes Boutonnière (French for buttonhole due to the nature of the tear) deformity. When the central slip is injured, the extensor tendon can no longer pull the finger into the extended position, therefore it remains bent. Similarly, when the extensor tendon attached to the distal phalanx is damaged, the result is a mallet finger.
The second aspect of Boutonnière deformity involves the distal phalanx. Because the first knuckle (also called the PIP joint) is unable to straighten, the ligaments on the sides of the finger shift and begin to hyperextend the end knuckle (DIP joint), adding to the crooked appearance of the finger.
What Causes Boutonnière Deformity?
When the condition is the result of an injury, Boutonnière deformity typically occurs after a sharp blow to the central slip while the finger is in the flexed position, such as in a work or sports injury. The patient may feel as if the finger has been jammed because of the pain and swelling.
In cases involving laceration, the central slip may become cut or detached from the bone, requiring surgery.
Approximately 1/3 of patients with rheumatoid arthritis are affected byBoutonnière deformity due to the central slip becoming damaged by inflammation.
Dupuytren’s contracture, a hand condition which affects finger extension, can also lead to Boutonnière deformity.
Boutonnière deformity may appear immediately after an injury, but can also present 1-3 weeks after the finger has been injured. In any case, the finger should be treated as quickly as possible to restore functionality and prevent permanent damage.
Symptoms of Boutonnière Deformity
No matter the cause, Boutonnière deformity has a distinct appearance of the affected finger, with the middle of the finger bent down and the end of the finger bent backwards.
Other symptoms of Boutonnière deformity include:
- Swelling over the central slip (top middle of injured finger)
- Painful and/or swollen joints in the affected finger
- Inability to bend the distal phalanx downward or straighten the finger
Diagnosing and Treating Boutonnière Deformity
Boutonnière deformity can typically be diagnosed during a physical examination, however, if an injury has occurred, your doctor may recommend x-rays to determine if any bone fractures are present. Treatment of Boutonnière deformity can vary depending on its cause and may include:
- Splinting: Most acute cases diagnosed promptly can be treated with splinting the PIP joint into the straight position, typically for 3-6 weeks. After this rehabilitation period, finger splinting at night may still be necessary for a time.
- Hand therapy: Stretching and other flexibility exercises can improve range of motion and finger strength. Rehabilitative therapy will likely be recommended in conjunction with both surgical and non-surgical treatment options. The Fort Worth Hand Therapy Center at OSMI provides comprehensive hand rehabilitation services with a Certified Hand Therapist.
- Hand surgery: Surgery may be required for the injured tendon if a penetrating laceration or additional finger damage is involved. For prolonged, untreated Boutonnière deformity, rheumatoid arthritis, or conditions that are unresponsive to splinting, surgery to reconstruct the ligament and repair the tendon may be recommended.
In cases of rheumatoid arthritis, oral medication and/or steroid injections may also be utilized during treatment. Splinting after surgery is typically required, and although surgery is usually successful in improving function and reducing or eliminating pain, the affected finger may remain misshapen.
Goals of Boutonnière deformity treatment include:
- Early diagnosis (left untreated, the deformity can progress and become permanent)
- Elimination or greatest possible reduction in deformity
- Restored range of motion and fine motor abilities
- Reduction/elimination of pain
- Improved strength
After treatment, you may need to wear protective tape or a splint during recreational or other physical activity to guard against re-injury. Keep in mind that Boutonnière deformity left untreated for over 3 weeks is much more difficult to correct. If you suffer an injury to your finger and experience symptoms of Boutonnière deformity, contact your orthopedic specialist as soon as possible for an evaluation.
If you are ready to choose a team of hand, wrist and elbow orthopedic and sports medicine specialists that offer state-of-the-art treatment and highly personalized care, contact the OSMI office or call 817-529-1900 today!