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A Patient's Guide to Boutonniere Deformity of the Finger Introduction The tendons that allow each finger to straighten, the extensor tendons, at first appear to be relatively simple. But, as the extensor tendon runs into the finger it becomes a complex and elegantly balanced mechanism that allows very fine control of the motion of each joint of the finger. When this mechanism is damaged in certain areas, this balance can be destroyed and the result is a finger that doesn't work properly. Over time, the imbalance can lead to contractures and other changes that result in a permanently crooked finger. The boutonniere deformity is one such problem that affects the extensor tendons of the finger. This guide will help you understand • what parts make up the extensor tendons of the fingers • what causes the boutonniere deformity • how the problem is treated • what to expect from treatment Anatomy What parts of the finger are involved? The extensor tendons begin as muscles that arise from the bones of the back side of forearm. These muscles travel towards the hand where they eventually connect to the extensor tendons before traveling across the back of the wrist joint. As they travel into the fingers, the extensor tendons become what is called the extensor hood. It flattens out to cover the top of the finger and sends 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. View graphic of general anatomy of the finger AP and Lateral with extensor hood. Causes How do these injuries of the PIP joint occur? 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, or 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 and the middle phalanx dislocates towards the palm. View graphic of the lateral finger closeup showing central slip tear. View dislocation of middle phalanx with central slip tear. The boutonniere deformity may not occur right away. It is the imbalance in the extensor hood that results from the torn tendon that eventually causes the deformity. Because the middle phalanx no longer is pulled by the central slip, the flexor tendon on the other side begins to bend the PIP joint without resistance. The lateral bands begin to slide down along the side of the finger where they continue to straighten the DIP joint. Eventually the finger becomes stiff in this position. View boutonniere deformity. Symptoms What do boutonniere deformities look and feel like? 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 as described above. Diagnosis What tests will my doctor do? Usually the diagnosis is evident just from the physical examination. X-rays are required to see if there is an associated avulsion fracture since this may change the recommended treatment. No other tests are required normally. View boutonniere deformity. 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 6 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. While a simple homemade splint will work, there are many splints that have been designed to make it easier to wear at all times. There are also special splints that have been designed that are similar to springs. These splints can be used to gently stretch out a contracture of the PIP joint over several weeks. The spring applies gentle pressure all the time and the PIP joint slowly straightens. Splinting and a rigorous exercise program may even work when the injury is quite old. Many hand surgeons will try a six week trial 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 repairng or reconstructing the extensor hood. Surgical Treatment 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 different types of operations that have been designed to try and rebalance the extensor hood. 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 dependant on a well designed and rigorous exercise program folllowing the surgery. A physical therapist or occupational therapist will work closely with you during your recovery.

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