Boutonnière Deformity; finger condition, middle joint proximal interphalangeal joint, PIP bends

Описание: Boutonnière deformity is a finger condition where the middle joint (PIP) bends inward toward the palm while the fingertip (DIP) bends backward, usually caused by injury or diseases like rheumatoid arthritis. It results from damage to the central slip of the extensor tendon, and treatment often involves splinting or surgery depending on severity.

Key Features of Boutonnière Deformity
Appearance:

PIP joint (middle knuckle) is bent forward (flexion).

DIP joint (fingertip knuckle) is bent backward (hyperextension).

Cause: Rupture or displacement of the central slip tendon that normally straightens the finger.

Name origin: Comes from French “boutonnière” meaning “buttonhole,” describing how the bone slips through the tendon gap like a button through a hole.

Common Causes
Trauma:

Jammed finger, lacerations, or avulsion injuries.

Medical conditions:

Rheumatoid arthritis (up to 50% of patients may develop it).

Psoriatic arthritis.

Genetic connective tissue disorders (e.g., Ehlers-Danlos syndrome).

Symptoms
Finger stuck in abnormal bent/extended positions.

Difficulty straightening the finger.

Pain, swelling, or stiffness around the PIP joint.

Diagnosis
Clinical exam: Visible deformity of PIP flexion and DIP hyperextension.

Elson test: A specific test to confirm central slip injury.

Treatment Options
Acute injuries:

Splinting the PIP joint in extension for several weeks.

Hand therapy exercises to restore tendon balance.

Chronic or severe cases:

Surgical repair or tendon reconstruction.

Joint fusion in advanced arthritis cases

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