Boutonniere deformity describes a medical condition in which the finger is flexed at the proximal interphalangeal joint (PIP), and there is hyperextension at the distal interphalangeal joint (DIP). This is usually a result of trauma in the acute setting and is caused by force applied to the top of a bent middle joint of a finger. There is a direct injury to the central slip that damages the extensor function of the affected digit. A boutonniere deformity can also result from a laceration on the top of a finger, which can sever the tendon and detach it from the bone. It can also happen if the patient would suffer a full-thickness burn resulting in direct injury to the central slip. However, more commonly, it's secondary to an inflammatory condition, such as rheumatoid arthritis.
Injury to the extensor tendon causes this flexion deformity of the proximal interphalangeal joint. The extensor tendon is disrupted and the lateral aspects of the tendon separate. The head of the proximal phalanx projects through this disrupted area. The deformity garnished its name because the injury caused the proximal phalanx to protrude through like a finger through a buttonhole (hence the name, from French boutonniere, which translates into buttonhole). Football and basketball are the most common source of sports-related boutonniere deformities.
A small number of emergency department diagnosed patients with jammed or sprained finger will eventually have boutonniere deformity. Up to half or 50% of patients with rheumatoid arthritis develop a boutonniere deformity in at least one digit.
A boutonniere deformity results when the triangular ligament and the central slip of the extensor tendon of a digit are disrupted. This disruption of the ligament and tendon will cause the lateral bands to the volar surface of the finger. This will result in forced flexion of the finger, and then the dorsal interphalangeal joint will experience difficulty in extension. Over time, the oblique retinacular ligament will contract. This ligament contracture will gradually worsen the hyperextension deformity of the joint. The pathophysiology is different if it is secondary to rheumatoid arthritis. Inflammatory cells collect in the synovial fluid of the joint which forms a layer of fibrous tissue. This leads to bony erosion and damage to cartilage and ligaments. The joints gradually deform which leads to loss of function and pain.
A thorough history and physical should be obtained to determine the mechanism of injury to the affected digit. It is important to recognize the type and extent of the injury as treatments options are varied depending on injury pattern. It is also necessary to prevent long-term complications and deformities from these injuries. It is usually one of the injuries associated with a “jammed finger.” Symptoms can be immediate or delayed for several weeks. If the injury occurs as a result of a laceration, the area needs to be thoroughly cleaned and examined in a “bloodless field” for tendon integrity. This can easily be accomplished by using a glove. Simply cut the finger off a glove and place on the affected digit and then cut a small hole at the distal aspect of the finger glove. Then, roll the finger glove proximally until it forms a “ring” at the base of the digit which will function as a tourniquet. The condition of the tendon will determine treatment options.
If rheumatoid arthritis causes a boutonniere deformity, a thorough history should include the duration of symptoms, medications (both previous and current), level of pain and degree of disability.
X-rays are indicated to determine if there are any associated fractures. It is also important to identify any disruption of the bones that attach to the central slip of the tendon. Lateral radiographs can be used to determine the degree of hyperextension.
The goal of treatment is to regain full range of motion of the affected finger. Treatment options include both surgical and nonsurgical modalities. Splinting is a nonsurgical treatment and involves immobilizing the affected joint to allow for straightening to occur. This also allows the tendon to heal and not continue to separate. Splints are usually maintained for 3 to 6 weeks depending on the patient’s age and severity of the injury. Often patients will be instructed to wear the splint at night for several more weeks. Management should also include exercises to improve the strength and flexibility of the affected digit. If the injury is a result of sports activity, the affected area may be taped or have other protective splinting applied to protect it further if resuming activities. Surgical correction can occur if the tendon is severed or if there is a significant bone fragment displaced from its normal position of function. It may also be an option if it does not improve with conservative measures, such as splinting. If a large avulsion is present, surgical fixation with a wire or screw is used to correct for the extensor injury. The deformity becomes more difficult to correct if the deformity has been left untreated for greater than three weeks.
The treatment options for a boutonniere deformity vary if it is a result of sequelae of rheumatoid arthritis. The classes of medications to treat rheumatoid arthritis are disease-modifying anti-rheumatic drugs (DMARDs), biologic response modifiers, glucocorticoids, nonsteroidal anti-inflammatory medications (NSAIDs), and analgesics. DMARDs are used to delay the progression of rheumatoid arthritis. DMARDs have different mechanisms of action and are often used in combination therapy. Although the mechanism of action varies, they have the similar impact of the disease process. Biologic response modifiers are genetically engineered and work by interrupting a patient’s immune system signals that are responsible for tissue damage. Most of these medications attempt to interfere with the activity of tumor necrosis factor. Glucocorticoids are used to reduce inflammation and also to curb the autoimmune activity. They are often used in conjunction with DMARDs. NSAIDs can aid with pain control, swelling, and inflammation, but do not affect slowing the disease process. Analgesics are used to control pain only.
If nonsurgical measures are unsuccessful, surgical joint replacement may be necessary. Joint fusion is another surgical procedure that involves fusing the two joint surfaces of the affected digit together. The benefits of joint fusion are pain improvement, increased the stability of the joint, and prevention of worsening joint deformity. After surgery, patients are instructed to wear a splint or brace for several weeks to keep the proximal interphalangeal joint straight. Physical or occupational therapy often follows splinting.