What is a Boutonniere Deformity?
A Boutonniere deformity affects the tendons that straighten (or extend) your finger. These tendons are a part of a complex system, the extensor mechanism. If you injure a certain area of these tendons, a boutonniere deformity can occur. This deformity, as shown in the image below, is when your middle joint (PIP joint) flexes and the tip joint (DIP joint) hyper-extends. The deformity may not be as pronounced as in the image, so if you injured your finger and have slight variations, we recommend you see a hand surgeon or hand therapist.
The lateral bands can slip out of place due to stretching or rupture. The lateral bands typically move when you move your finger. If they overstretch or tear, they can slide down (towards the palm-side of your finger). When the lateral bands slide down, they hold your middle joint (PIP joint) in a flexed position. In the image below, there is a simplified outline of where the lateral bands rest with your finger straight (left) versus how the slide down when you flex your finger (right).
How Does Boutonniere Deformity Occur?
Boutonniere deformity can be the result of an injury or arthritis (see below). Similar to mallet finger injuries which we discussed last week, boutonniere deformities can be caused by blunt trauma (especially to the tip), finger fracture or dislocation, or a laceration on the top of your finger.
Treatment for Boutonniere Deformity
Deformity from Injury
For a boutonniere deformity caused by an injury, the lateral bands over-stretch or rupture. This is treated by splinting the finger for at least 6 weeks. This time period could be longer depending on how severe your injury was. If your therapist is unable to straighten your finger at the first visit, the initial goal is to regain the extension at the middle, PIP joint. Once the PIP joint is straight, you will then wear an extension splint for 6-12 weeks.
If your injury was more severe such as a fracture, rupture, or laceration, you may require surgery and should consult a hand surgeon.
Deformity from Arthritis
We typically see boutonniere deformities in patients with rheumatoid arthritis, or RA. With RA there is swelling in the covering around the joints (joint capsule). This increase in fluid can cause stretching to the lateral bands. Typically with arthritis, we work to treat the swelling and use splints to prevent further deformity. Boutonniere deformities in arthritis can be mechanically corrected via the use of splints or they can be surgically corrected. They typically do not heal on their own.
Have you sustained an injury between or including your shoulder and fingertips? Do you suspect that your workplace environment is causing you pain? If so, you could be a candidate for hand therapy services at LB Hand Therapy in Maryland. Visit our Where to Begin page to become a patient.