Boutonniere deformity describes a medical condition in which the finger is flexed at the proximal interphalangeal joint (PIP) and hyperextended at the distal interphalangeal joint (DIP). This is usually a result of trauma in the acute setting and is caused by a rupture of the PIP central slip. This results in damage to the extensor function of the affected digit. A boutonniere deformity can also result from laceration injury to the central slip and dorsal capsule.   Boutonniere deformities can also occur secondary to burn injury, with tension ischemia representing a possible etiology for tendon rupture.  Overall, Boutonniere deformities common represent sequela of inflammatory arthritides, such as rheumatoid arthritis.
Injury to the extensor tendon is the chief etiology for this flexion deformity of the PIP joint. The extensor tendon is disrupted and the lateral aspects of the tendon separate. The head of the proximal phalanx subsequently projects through the disrupted tendon elements. This deformity obtained its name presumably due to its appearance to a buttonhole on surgical exploration. Football and basketball-related injuries are the most common sources of sports-related boutonniere deformities.
While jam-injuries represent a heterogeneous group of trauma-related injuries, central slip injuries and subsequent development of boutonniere deformities constitute a well-known sequela of jam-injuries.  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 displace volarly. This results in forced flexion of the finger, and subsequent limitation of the DIP joint to extend. Over time, the oblique retinacular ligament gradually contracts. This ligament contracture will gradually worsen the hyperextension deformity of the joint.  The pathophysiology is different if it is secondary to rheumatoid arthritis (RA) or a burn injury. In the setting of inflammatory arthritides such as RA, 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. Treatment options vary depending on etiology and early identification of injury can prevent long-term complications and deformities from these injuries. A deformity can take several weeks to manifest. In the setting of a laceration injury, the area needs to be thoroughly cleaned and examined in a “bloodless field” for tendon integrity.  In the setting of "jam injuries," a central slip injury is oftentimes occult. The "Elson test" can be performed to assess tendon integrity, and involves the following steps :
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.
Radiographs are indicated to determine if there are any associated fractures. It is also important to identify any cortical 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 PIP flexion(straightening) to occur. This also allows the tendon to heal and not continue to volarly separate. Splints are usually maintained for 3 to 6 weeks depending on the patient’s age and severity of the injury.  Patients will often 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 further splinted for protection on activity resumption. Surgical correction can be employed 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 if it represents a chronic sequela 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 a similar impact on 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.
Complications with or without treatment include :
Considering that prognosis and outcomes are often varied with patients rarely returning to baseline functionality, the physician plays an important role in managing expectations. Patients should be educated on various complications such as limited chronic range of motion, early arthritis, and predisposition to reinjury. A physician managing athletes, especially those predisposed to finger injuries such as football and basketball players, should advice his/her patients to present early in the setting of jam-injuries of the fingers. Educating patients that a delay in management can have possible long term sequela that could limit further participation in sports.
The diagnosis and management of boutonniere deformity is complex and requires an interprofessional team that includes a primary care provider, nurse practitioner, physical therapist, hand surgeon, and orthopedic surgeon. The goal of treatment is to regain full range of motion of the affected finger. Treatment options include both surgical and nonsurgical modalities. 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. The outcomes for boutonniere deformity are guarded. While recovery is possible, it may take a long time to improve range of motion and function. (Level V)
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