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Boutonniere Deformity

Boutonniere deformity is a characteristic finger deformity involving abnormal positioning of the finger joints. It is defined by flexion of the proximal interphalangeal (PIP) joint (the middle joint of the finger) combined with hyperextension of the distal interphalangeal (DIP) joint (the joint closest to the fingertip). This abnormal posture makes the finger appear as though it is passing through a buttonhole in clothing, which is the origin of the name “boutonnière” (French for buttonhole).

Boutonniere deformity can interfere with both the cosmetic appearance and the functional capacity of the hand. It makes it difficult to straighten the finger fully and can impair activities that require precise finger movements, such as writing, gripping, or typing.

Tendon Problems

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Causes and Mechanism of Deformity

The deformity occurs due to disruption of the extensor mechanism of the finger. The extensor tendon on the back of the finger splits into three parts as it crosses the PIP joint: a central slip that attaches to the middle phalanx and two lateral bands that continue to the distal phalanx.

  • Central Slip Injury: If the central slip is torn or ruptured, the PIP joint loses its main extensor force, leading to uncontrolled flexion at this joint.
  • Lateral Band Imbalance: With the central slip disrupted, the lateral bands slip downward to the sides of the finger. Over time, they shift below the axis of the PIP joint, turning into flexors instead of extensors. As a result, the DIP joint is pulled into hyperextension, while the PIP joint stays flexed.

Common Causes:

1. Trauma

  • A direct blow to the back of the finger or forceful bending of the PIP joint can rupture the central slip.
  • Sports injuries, falls, or lacerations are typical traumatic causes.

2. Rheumatoid Arthritis

  • Chronic inflammation weakens the tendon structures and ligaments, making them susceptible to rupture and deformity.

3. Other Conditions

  • Osteoarthritis, burns, or untreated finger injuries such as mallet finger may predispose to boutonnière deformity.

Clinical Features

Appearance:

  • PIP joint flexed.
  • DIP joint hyperextended.
  • The finger assumes a bent posture resembling a buttonhole.

Symptoms:

  • Pain and swelling at the PIP joint, particularly soon after injury.
  • Difficulty extending the PIP joint actively.
  • Progressive stiffness and deformity if untreated.
  • Functional impairment in gripping or pinching.

Diagnosis

  • Inability to actively extend the PIP joint.
  • Hyperextension at the DIP joint.
  • Tenderness over the central slip insertion (middle phalanx dorsum).
  • Elson’s test: The patient attempts to extend the PIP joint against resistance while the finger is bent at 90°. If the central slip is ruptured, extension is weak or absent, and the DIP joint stiffens.
  • X-rays: To exclude fractures or dislocations.
  • MRI/Ultrasound: May be used to confirm tendon injury in complex cases.
  • In rheumatoid arthritis patients, doctors check for other hand deformities such as swan neck deformity or joint instability.

Treatment

1. Non-Surgical Management

  • The primary treatment for acute injuries.
  • The PIP joint is immobilized in full extension using a splint for 4–6 weeks in acute trauma, or 6–8 weeks in rheumatoid arthritis-related deformity.
  • The DIP joint is left free to move, which prevents stiffness and maintains flexibility.
  • Exercises: After splinting, gentle exercises help restore mobility and strengthen surrounding structures.
  • Medication: NSAIDs for pain and inflammation. In rheumatoid arthritis, disease-modifying drugs are also used to control progression.

2. Surgical Management

  • The deformity is severe or chronic.
  • There is a complete rupture of the central slip.
  • Non-surgical management fails.
  • Direct Repair of the central slip in acute injuries.
  • Lateral Band Relocation to restore their normal alignment above the PIP joint.
  • Tendon Grafting or Reconstruction when tendon tissue is severely damaged.
  • Joint Fusion (Arthrodesis) of the PIP joint in functional position if deformity is rigid and painful, especially in arthritis patients.

Complications

  • Permanent finger deformity.
  • Joint stiffness and limited mobility.
  • Functional impairment in daily tasks.
  • Progressive joint degeneration and arthritis.
  • Cosmetic dissatisfaction.

Prognosis

  • Acute traumatic cases treated early with splinting often heal well, with good recovery of function.
  • Chronic deformities or those due to rheumatoid arthritis may be harder to correct but can be improved with surgery or splinting.
  • Even with optimal care, some patients may experience minor stiffness or incomplete extension.

Prevention

  • Early recognition and treatment of finger injuries, especially central slip ruptures, are crucial.
  • In rheumatoid arthritis patients, controlling inflammation with appropriate medications reduces the risk of tendon damage and deformity.
  • Protective splints during sports or high-risk activities can prevent traumatic injuries.

Conclusion

Boutonniere deformity is a disabling finger condition characterized by flexion of the PIP joint and hyperextension of the DIP joint due to disruption of the extensor mechanism. It commonly results from trauma, rheumatoid arthritis, or chronic tendon imbalance. Prompt diagnosis and early treatment with splinting are vital for restoring finger function and preventing long-term deformity. Surgical correction is reserved for severe or chronic cases. With proper management, many patients achieve significant improvement in function and appearance of the affected finger.

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