Buttonhole Deformity: Causes, Symptoms, Diagnosis, and Treatment

What is Buttonhole Deformity?

Buttonhole deformity, clinically known as Boutonnière deformity, is a common finger deformity characterized by the proximal interphalangeal (PIP) joint being bent in a flexed position, while the distal interphalangeal (DIP) joint is hyperextended.

Understanding Buttonhole Deformity (Boutonnière Deformity)

Buttonhole deformity is a specific type of finger joint dysfunction that primarily affects the PIP joint, the middle joint of the finger. The name "boutonnière" is French for "buttonhole," referring to how the PIP joint appears to protrude through a tear in the extensor mechanism, much like a button through a buttonhole.

Anatomy and Mechanism: The extensor mechanism of the finger is a complex network of tendons that allows the finger to straighten. It consists of the central slip, which attaches to the base of the middle phalanx and extends the PIP joint, and the lateral bands, which travel along either side of the finger and ultimately extend the DIP joint.

In buttonhole deformity, the core issue is damage to the central slip of the extensor tendon at the PIP joint. When this central slip is compromised—due to rupture, stretching, or detachment—the extensor force to the PIP joint is lost. This allows the PIP joint to drop into a flexed position. Simultaneously, the lateral bands, which would normally be held in place by the central slip, shift downward (palmarward) relative to the PIP joint's axis of rotation. This shift causes them to become flexors of the PIP joint, further contributing to its flexion. However, as they continue distally, these displaced lateral bands become more effective extensors of the DIP joint, pulling it into a hyperextended position. The result is the characteristic "buttonhole" appearance.

Causes and Risk Factors

Buttonhole deformity can arise from various factors, broadly categorized into acute trauma and chronic conditions.

Common Causes:

• Acute Trauma:
  • Direct impact: A forceful blow to the top of the bent finger, such as during sports (e.g., catching a ball incorrectly, "jammed finger").
  • Deep cut or laceration: A sharp object cutting the central slip tendon.
  • Forceful flexion: Hyperextension of the PIP joint that tears the extensor mechanism.
• Inflammatory Conditions:
  • Rheumatoid Arthritis (RA): This is a leading cause, where chronic inflammation damages the joint capsule, ligaments, and tendons, particularly the central slip. The inflammatory process weakens the connective tissues, making them susceptible to rupture or progressive stretching.
• Osteoarthritis: Less common than RA, but severe joint degeneration can contribute.
• Systemic Lupus Erythematosus (SLE): Another autoimmune condition that can affect connective tissues.

Risk Factors:

• Participation in contact sports or activities with high risk of finger impact.
• Pre-existing inflammatory arthritis, especially rheumatoid arthritis.
• Occupations that involve repetitive stress on the fingers.

Signs and Symptoms

The presentation of buttonhole deformity typically involves a distinct appearance and functional limitations of the affected finger.

Primary Symptoms:

• PIP Joint Flexion: The middle joint of the finger is noticeably bent, and the individual may be unable to straighten it actively.
• DIP Joint Hyperextension: The outermost joint of the finger (distal interphalangeal joint) is hyperextended, appearing straightened or even bent backward.

Other Manifestations:

• Pain: Often present immediately after an acute injury, or chronic pain in inflammatory conditions.
• Swelling: Around the PIP joint, especially in acute cases or active inflammation.
• Tenderness: To touch over the back of the PIP joint.
• Reduced Range of Motion: Difficulty in fully straightening or bending the finger.
• Functional Impairment: Difficulty with fine motor tasks, gripping objects, or performing daily activities due to the finger's altered mechanics.
• Initial Delay: In some cases, the full deformity may not develop immediately after an injury but can evolve over days or weeks as swelling subsides and the integrity of the extensor mechanism further degrades.

Diagnosis

Accurate diagnosis of buttonhole deformity is crucial for effective management and typically involves a combination of clinical assessment and imaging.

Clinical Examination: A healthcare professional, often a hand specialist, will perform a thorough physical examination.

• Visual Inspection: Observing the characteristic appearance of the flexed PIP and hyperextended DIP joints.
• Palpation: Checking for tenderness and swelling over the PIP joint.
• Range of Motion Assessment: Testing active and passive flexion and extension of both the PIP and DIP joints. The inability to actively extend the PIP joint against resistance while the DIP joint hyperextends is a key diagnostic sign.
• Elson's Test: A specific test where the patient flexes the PIP joint over the edge of a table and attempts to extend it against resistance. If the DIP joint hyperextends, it suggests a central slip injury.

Imaging:

• X-rays: Used to rule out fractures, dislocations, or underlying arthritic changes, especially relevant in traumatic cases or chronic inflammatory conditions.
• Magnetic Resonance Imaging (MRI): May be used in more complex or chronic cases to visualize the soft tissues, including the extent of tendon damage (central slip rupture) and any associated ligamentous injuries.
• Ultrasound: Can sometimes be used to assess tendon integrity.

Treatment and Management

Treatment for buttonhole deformity aims to restore the normal function and appearance of the finger. The approach depends on the cause, severity, and chronicity of the deformity.

Non-Surgical (Conservative) Approaches: Conservative management is the preferred initial treatment, especially for acute injuries or mild deformities.

• Splinting: This is the cornerstone of conservative treatment. A PIP joint extension splint is worn continuously for 6-8 weeks (or longer, up to 12 weeks for chronic cases) to keep the PIP joint in full extension while allowing the DIP joint to move freely. This allows the central slip to heal without tension. The splint is typically only removed for hygiene and specific exercises prescribed by a therapist.
• Physical Therapy/Occupational Therapy: Crucial for regaining strength, flexibility, and function.
  • Range of Motion Exercises: Gentle exercises for the DIP and MCP (metacarpophalangeal) joints to prevent stiffness, while the PIP joint remains splinted.
  • Strengthening Exercises: Once the splint is removed, progressive exercises to strengthen the extensor muscles and improve grip.
  • Scar Management: If applicable, to prevent contractures.
  • Patient Education: Guidance on activity modification and proper hand mechanics.
• Medications: Non-steroidal anti-inflammatory drugs (NSAIDs) may be used to manage pain and reduce inflammation, particularly in acute injuries or inflammatory conditions.
• Corticosteroid Injections: Rarely used directly into the tendon due to risk of rupture, but may be considered for severe inflammation in the joint.

Surgical Intervention: Surgery is typically reserved for cases where conservative treatment has failed, for chronic or severe deformities, or when there is significant functional impairment.

• Indications for Surgery:
  • Acute injuries with complete central slip rupture that cannot be managed with splinting.
  • Chronic, fixed deformities that are not correctable with splinting.
  • Significant functional deficits.
  • Cases where conservative treatment has failed after adequate trial.
  • Deformities associated with significant joint instability or dislocation.
• Types of Surgical Procedures:
  • Tendon Repair/Reconstruction: Repairing the torn central slip or reconstructing it using a tendon graft.
  • Lateral Band Mobilization: Releasing or repositioning the lateral bands to improve PIP extension.
  • Arthrodesis (Joint Fusion): In severe, long-standing cases with significant joint destruction and pain, the PIP joint may be fused in a functional position to alleviate pain and provide stability, though this sacrifices motion.
  • Arthroplasty (Joint Replacement): Less common for this specific deformity but may be considered if the joint is severely damaged.

Prognosis and Rehabilitation

The prognosis for buttonhole deformity varies depending on the cause, severity, and adherence to treatment protocols.

Recovery Timeline:

• Acute Injuries: With prompt and consistent splinting and therapy, many acute cases can achieve good functional outcomes within 3-6 months.
• Chronic Deformities: These are more challenging to treat, and recovery can be prolonged, sometimes taking 6-12 months or longer, especially if surgery is involved. Full correction may not always be achieved.
• Rheumatoid Arthritis: Outcomes can be less predictable due to the ongoing inflammatory process and potential for multiple joint involvement.

Importance of Adherence: Strict adherence to splinting protocols and physical therapy exercises is paramount for successful outcomes. Premature removal of the splint or insufficient therapy can lead to recurrence or worsening of the deformity.

Potential Complications:

• Stiffness: Especially if immobilization is prolonged or therapy is not diligent.
• Persistent Deformity: Inability to achieve full correction, particularly in chronic or severe cases.
• Pain: Chronic pain may persist.
• Recurrence: If the underlying cause is not addressed or if rehabilitation is inadequate.

Prevention

While not all cases of buttonhole deformity can be prevented, especially those related to systemic diseases, certain measures can reduce the risk.

• Injury Prevention:
  • Protective Gear: Wearing appropriate gloves or hand protection during sports or activities that carry a risk of finger impact.
  • Proper Technique: Learning and using correct hand techniques in sports and manual tasks to avoid jamming or hyperextending fingers.
  • Awareness: Being mindful of surroundings and potential hazards that could lead to finger injuries.
• Managing Underlying Conditions:
  • Rheumatoid Arthritis Management: For individuals with RA, strict adherence to medical treatment to control inflammation and disease progression is vital. This can help prevent or mitigate tendon and joint damage that leads to deformities like buttonhole.
  • Early Intervention: Promptly addressing any signs of finger pain or dysfunction, especially in individuals with inflammatory conditions.

When to See a Doctor

Early diagnosis and intervention are critical for optimal outcomes in buttonhole deformity. Consult a healthcare professional if you experience:

• Sudden onset of pain, swelling, and difficulty straightening your finger after an injury, especially if the middle joint is bent and the end joint is hyperextended.
• Gradual development of the characteristic finger deformity (bent middle joint, hyperextended end joint), even without a clear injury, particularly if you have a history of inflammatory arthritis.
• Persistent pain, stiffness, or functional limitations in your finger that do not improve with rest or home remedies.

A hand specialist, orthopedic surgeon, or rheumatologist can provide an accurate diagnosis and develop an appropriate treatment plan.