A boutonniere deformity occurs when the tendon that straightens the middle joint of your finger is injured, weakened or stretched. The injury allows the middle finger joint to bend (flex) and the end finger joint to pull back and hyperextend. This makes the finger appear crooked.
A boutonniere deformity can cause pain and loss of function. Treatments include splinting, hand therapy, and surgery. When treated promptly, conditions tend to have the best outcomes.
Your fingers are made up of three bones called phalanges. Two joints separate the phalanges. The distal interphalangeal (DIP) joints are located near your fingertips. The proximal interphalangeal (PIP) joints are located in the middle of your fingers. The extensor tendons allow your fingers to extend and straighten.
A boutonniere deformity occurs when the extensor tendon attachment at the central slip on the middle phalanx is injured. The PIP joint is not able to straighten and remains bent (flexed). The DIP joint is pulled back into hyperextension by the extensor mechanism that has become out of balance. This results in a crooked and poorly functioning finger.
Arthritis, burns, Dupuytren’s contracture, and injuries, can disrupt the extensor tendon. The tendon may partially or completely tear. The extensor tendon can remain intact but pull a piece of bone away from where it attaches on the phalanx, also called an avulsion fracture.
A boutonniere deformity can cause your PIP joint to feel painful and swollen. You may not be able to straighten out your PIP joint. Your DIP joint may be hyperextended, causing your finger to look crooked.
Your doctor can diagnose a boutonniere deformity by examining your hand. X-rays will be taken to check for fractures and the condition of the joints.
Some boutonniere deformities can be treated with splinting. Splinting can help certain new and old injuries. There are many types of splints for boutonniere deformities. Hand therapy is especially important to ease symptoms and gain functioning. Splinting is usually tried for at least six weeks.
Surgery may be necessary to reconstruct a tendon or joint. If past treatments and surgery fail, the bones in the finger can be surgically fused together and kept from moving. All types of surgeries are followed by splinting and hand therapy.
Recovery from boutonniere deformity surgery can take three to four months. It can take up to six months for a full recovery. Recovery is individualized and your doctor will let you know what to expect.
You should contact your doctor if you notice you are developing a boutonniere deformity. In most cases, early treatment is associated with the best outcomes. Following treatment, your hand therapist can recommend ways to perform your regular activities to help you avoid future injuries.