Introduction

The extensor tendons, which allow each finger to straighten, run into the finger becoming a complex balanced mechanism allowing for fine control of each finger joint. If damaged in certain areas, this control can be destroyed and the result is a finger that doesn't work properly. Over time, the imbalance can lead to changes that result in a permanently crooked finger. The boutonniere deformity is one such problem that affects the extensor tendons of the finger.

Anatomy

As the extensor tendons travel into the fingers, they become the extensor hood, flattening out to cover the top of the finger and sending out branches that connect to the middle phalanx and the distal phalanx. When the extensor muscle contracts it shortens and pulls on these attachments to straighten the finger.

Small ligaments also connect the extensor hood with other tendons that travel into the finger to bend the finger. These connections help balance the motion of the finger so that all the bones of the finger work together giving a smooth bending and straightening action.

Causes

The boutonniere deformity occurs when the extensor tendon attachment to the middle phalanx is injured. This area is called the central slip. This tendon attachment may be injured in many ways. The central slip may simply be damaged when a cut occurs on the back of the finger over the joint. More commonly the central slip is torn (avulsed) from its attachment on the bone when the finger is jammed from the end, forcing the PIP joint to bend. Sometimes a small amount of bone is pulled off with the tendon. Finally, the central slip can be torn when the PIP joint is dislocated.  

The boutonniere deformity may not occur right away. It is the imbalance in the extensor hood that eventually causes the deformity. Eventually the finger becomes stiff in position. 

Symptoms

Initially, the finger is painful and swollen around the PIP joint. The PIP joint may not straighten out completely under its own power. The finger can be straightened easily with help from the other hand. Eventually, the imbalance leads to the typical shape of the finger with a boutonniere deformity.

Diagnosis

Usually the diagnosis is evident just from the physical examination. X-rays are required to see if there is an associated fracture since this may change the recommended treatment. No other tests are usually required.

Treatment

Treatment for boutonniere deformity depends on whether the injury to the central slip is recognized immediately or if the deformity has been present for a long time. When the injury is the result of a laceration of the finger, the surgeon will usually repair the tendon as well as suture the skin. 

Conservative Treatment

If the injury to the central slip results from a simple avulsion of the tendon from the bone, splinting of the PIP joint for six weeks should allow the tendon to heal and prevent the boutonniere deformity from occurring. The DIP joint is free to move throughout this period and can be exercised throughout this period to prevent stiffness in the DIP joint. 

Splinting and a rigorous exercise program may even work when the injury is quite old. Many hand surgeons will try six weeks of splinting with the spring type splint and exercise to see if the deformity lessens to a tolerable limit before considering surgery. This may also be desirable before surgery to stretch out any contracture before repairing or reconstructing the extensor hood.
 
Surgery

Surgical treatment is required for several cases. When the deformity is the result of a dislocation of the PIP joint, surgery may be required to repair the damaged structures and prevent the later development of a boutonniere deformity. In cases where the balance cannot be restored to a tolerable limit with splinting, surgery may be required to reconstruct and rebalance the extensor hood.

There are numerous operations designed to try and rebalance the extensor hood including fusion of the bone at the end of your finger (distal phalanx). None are completely successful. This type of surgery carries a relatively high risk of failure to achieve completely normal functioning of the extensor mechanism of the finger. All of the repair and reconstruction procedures are dependent on a well designed and rigorous exercise program following the surgery. A physical therapist or occupational therapist will work closely with you during your recovery.

Rehabilitation

If conservative treatment is successful, you may see improvement in eight to 12 weeks. After wearing a finger splint for up to eight weeks, doctors may have you continue wearing the splint at night for at least another month. It is important during this time that the joints on either side of the splint are moved. This may require the help of a physical or occupational therapist.

After surgery, you'll wear a splint or brace. A protective finger splint holds the PIP joint straight and is used for at least three weeks after surgery. Doctors may apply a dynamic splint to help gradually straighten the PIP joint. Physical or occupational therapy treatments usually start three to six weeks after surgery.

You may need to attend therapy sessions for three to four months. The first few therapy treatments will focus on controlling the pain and swelling from surgery. Then you'll begin gentle range-of-motion exercise. Strengthening exercises are started eight to 10 weeks after surgery. You'll learn ways to grip and support items in order to do your tasks safely and with the least amount of stress on your finger joint. As with any surgery, you need to avoid doing too much, too quickly.

Eventually, you'll begin doing exercises designed to get your hand and fingers working in ways that are similar to your work tasks and daily activities. Your therapist will help you find ways to do your tasks that don't put too much stress on your finger joint. Before your therapy sessions end, your therapist will teach you a number of ways to avoid future problems.