Boutonnière Deformity

Boutonnière deformity is a condition that affects your ability to straighten the middle joint of a finger (or, less commonly, a toe). Your middle joint is stuck in a bent position and won’t straighten. At the same time, the joint toward the tip of your finger or toe is flexed upward.

A boutonnière deformity can happen if you injure a tendon in your finger called the central slip. This is the tendon that allows you to straighten your finger at the middle joint. It runs over the top of your finger, and you might be able to see it where it passes over your knuckles.

If an injury stretches or tears this tendon, it creates a split in the fibers that looks like a buttonhole. (Boutonnière means “buttonhole” in French.) If this tear isn’t repaired, the tendon won’t work right, and you won’t be able to straighten your finger joints.

Central slip injuries are the most common cause of boutonnière deformity, but arthritis can also cause it. In this case, damage to the soft tissues in your finger may force the tendon out of place by stretching it or weakening it. This can have the same effect as a tear.

Symptoms of boutonnière deformity

The primary symptom of boutonnière deformity is the abnormal position of your finger joints. You’ll be unable to straighten the middle joint (proximal interphalangeal or PIP joint). Also, the joint at the tip (distal interphalangeal or DIP joint) will be hyperextended.

You may also have:

• Pain and swelling in the joints
• Stiffness that gets worse with time

Symptoms may develop immediately after a finger injury or up to several weeks afterward. If you have arthritis of the hand, boutonnière deformity may develop very gradually. The first sign may be that your finger just doesn’t bend and straighten as easily as it should.

Causes of boutonnière deformity

Boutonnière deformity is usually the result of a traumatic injury to your central slip tendon.

Examples include:

• A jammed finger that tears the tendon as well as ligaments
• A broken finger where the bone stretches or tears the tendon
• A finger joint dislocation that stretches or tears the tendon
• Blunt or penetrating trauma to your finger and the tendon

Anyone can get a central slip injury, but it’s more common in athletes, who are prone to sports injuries.

Other possible causes include:

• Rheumatoid arthritis. Constant inflammation and swelling in your hand can weaken the tendon.
• Burn injuries. Burns can weaken the tendon and, in some cases, can lead to rupture.
• Congenital hand deformity. Boutonnière deformity may be a birth defect (congenital disorder).
• Connective tissue diseases. Certain genetic disorders can weaken your connective tissues.

Your central slip tendon works together with a network of other tendons that extend your finger. They’re called extensor tendons. If the central slip slackens or ruptures, it can’t pull your PIP joint. It also affects the extensors that pull your DIP joint, making them pull more.

How doctors diagnose boutonnière deformity

A healthcare provider will examine your finger and ask you about your symptoms and health history. Boutonnière deformity is easy to recognize on sight. But if it’s just starting to develop, it might not be obvious yet. They might perform a quick test called Elson’s test.

They’ll ask you to curl your fingers around the edge of a table. They’ll gently press down on the bone in your forefinger (middle phalanx). Then, they’ll ask you to straighten your finger against their resistance. If you can’t straighten it, they’ll know your central slip is impaired.

Your provider might want to follow up with X-rays to evaluate the injury and plan your treatment.

How is boutonnière deformity treated?

Most of the time, healthcare providers start with conservative (nonsurgical) treatments for boutonnière deformity. But it’s important to treat it sooner than later. The longer it goes untreated, the harder it may be to correct the deformity, even with surgery.

Conservative treatment for boutonnière deformity

If your condition is relatively recent, your healthcare provider will start by splinting your finger. The splint will hold your PIP joint in an extended position for several months while the injured tendon heals. After this, you’ll have several months of physiotherapy.

Surgical treatment for boutonnière deformity

For severe injuries and older conditions that have failed to heal with conservative treatment, you might need surgery. You might have scar tissue in your finger that’s holding it in the wrong position, or your surgeon might need to put parts back where they belong.

Your surgeon might:

• Repair or reconstruct the central slip tendon
• Reposition or release tension in other extensor tendons
• Repair or fuse the PIP joint (if arthritis is involved)

After surgery, you’ll wear a finger splint for several weeks while your finger heals. After the first week, you’ll have hand exercises to practice as you recover. Your physiotherapist or hand therapist will guide your rehabilitation during the next few months.

What can I expect if I have boutonnière deformity?

Boutonnière deformity is treatable, but timing matters. If you get treatment right away after an injury, you may recover completely, with or without surgery. If it takes a while to recognize and treat your boutonnière deformity, it may be more challenging.

The cause of your deformity also matters. Chronic conditions like arthritis can interfere with healing and recovery. Severe injuries and congenital disorders may be harder to fix with surgery. Sometimes, surgeons can restore some of your finger joint flexibility, but not all.

Recovering from boutonnière deformity can take many months, and it requires active participation from you — especially when it’s time to start exercising your finger. But most people who follow their healthcare team’s guidance will have good outcomes.