What to know about Boutonniere deformity

Deformity of the buttonniere allows the middle joint to curve inward in a finger or thumb and the end joint to turn outward.

This can be treated with a splint, but other treatments are sometimes required.

Deformities of the boutonniere can result from injuries to the tendons running along the finger or thumb back. These are different from “deformities in the swan neck” which affect the base joint.

This article discusses what are deformities of boutonniere, their causes, and some possible options for treatment.

Definition

A person may have a boutonniere deformity in the middle joint of any finger or the thumb.
Image credit: Alborz Fallah, 2013
A person may have a boutonniere deformity in the middle joint of any finger or the thumb.
Image credit: Alborz Fallah, 2013

A deformation of the boutonniere happens when a finger’s middle joint bends inwards, while the joint at the end points outward. It can impact on any finger or thumb.

It is easy to confuse deformity of a boutonniere with deformity of a swan neck. A deformation of the swan neck occurs when the base joint of the finger bends inward, rather than the middle joint.

Diagnosis

A doctor must physically examine the fingers and the hand to diagnose a deformity of the boutonniere.

We will test each joint position to rule out common deformities, such as deformation of the swan neck.

The doctor should assess the medical history of a individual, too. They will look for conditions, such as arthritis, that increase the risk of boutonniere deformity.

They may also use medical imaging to check for any signs of bone damage, such as X-rays.

Causes and symptoms

A deformity of the boutonniere may occur due to an injury or underlying condition of health. The primary cause is typically damage to the tendon which runs along the back of the finger or thumb joint.

The injury usually occurs on the tendon of the middle phalanx extensor, which is at the bottom of the tendon. This causes the joint bone to push through the tendon and thus creates the deformity.

Another possible cause of boutonniere deformity is rheumatoid arthritis. Rheumatoid arthritis and the like can cause inflammation in the finger tendons, such as psoriatic arthritis. This can weaken or damage the tendon over time which causes the joint to bend.

This irregularity can make straightening a person’s finger or thumb difficult. With time it may get worse, too.

Deformities in the buttonniere can cause problems using the finger. For example, typing an object on a computer or griping it can be difficult.

Providing prompt treatment is important to help prevent the irregularity from getting worse.

Treatment

Through early treatment a deformity of the boutonniere will generally be repaired without permanent damage being left. Treatments can be either surgical or non-operative, depending on the severity of the abnormalities.

Splints are a common type of nonoperational therapy. A splint is a brace which can be added to the finger to provide protection.

These are useful for keeping your finger straight. Wearing a splint can slowly allow the joints to return to their normal positions.

Splints are most successful when a tendon injury is caused, and prompt treatment. The length of time that the splint is needed for depends on the severity of the injury and the age of the individual.

A young person may need to wear a splint for up to 6 weeks, for example, while an older adult may wear the split for around 3 weeks.

Typically, a doctor or hand professional tests a person’s progress multiple times while using a splint. During this time, it is best not to participate in contact sports, play an instrument or do any other activities that may cause more finger damage.

When a disease causes the deformity it can need more than just a splint. For example, a doctor may prescribe corticosteroids to help reduce tendon inflammation.

A doctor can recommend surgery if the tendon is broken or other therapies don’t function.

In surgery, a health care practitioner can cut a tendon area to release pressure on the joint. They may also insert a screw or wiring similar to a splint, to straighten the joints. This will fuse the joint to a fixed position.

Surgical treatment is more common when a condition, such as rheumatoid arthritis, causes a deformation of the boutonnière.

Exercises

A doctor can recommend some exercises to stretch the fingers when a person no longer uses a splint and the fingers are in the final stages of healing. These may help to improve tendon strength and flexibility.

For instance, they may suggest bending the fingers down towards the palm from the base until they hit an angle of 90 degrees. Keep your fingers straight as much as possible and hold the position for a few seconds.

Or, they may suggest bending the finger tips just slightly towards the palm and holding for a few seconds.

A doctor will decide on whether and how often these exercises are to be done, and when it is best to start. Before doing any exercises with a doctor or hand specialist to avoid further damage, it is important that you discuss them.

Summary

A boutonniere deformity occurs when a finger or thumb’s middle joint bends inwards, and the end joint bends outwards.

It is a common occurrence which may result from injuries or conditions of health, such as rheumatoid arthritis.

Normally a doctor recommends using a splint. Over time this may help heal tendon injuries. Certain procedures, like surgery, may be appropriate where the cause is a disease.

A doctor may also prescribe exercises to help with rehabilitation. These tendons can be strengthened, and flexibility improved.

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