Orthopaedic Surgery - Boutonniere Deformity

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Basics

Boutonniere deformity is characterized by flexion of the proximal interphalangeal joint (PIPJ) together with hyperextension of the distal interphalangeal joint (DIPJ).

The deformity develops as a consequence of injury or failure of the central slip of the extensor mechanism.

It may occur after acute trauma or develop gradually in association with inflammatory disease such as rheumatoid arthritis.

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General Prevention

The main preventive measure is appropriate medical control of rheumatoid arthritis, which can reduce chronic synovitis and subsequent attrition of the central slip.

Traumatic cases are not always preventable, but early recognition and treatment of a central slip injury can reduce the risk of progression to a fixed deformity.

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Risk Factors

The most important medical risk factor is rheumatoid arthritis.

Chronic inflammation of the PIP joint can weaken and gradually damage the central slip, eventually producing the characteristic deformity.

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Etiology

Boutonniere deformity results from a central slip injury.

The central slip may fail because of direct rupture, gradual attenuation, or avulsion from its bony insertion.

Inflammatory synovitis of the PIP joint, particularly in rheumatoid arthritis, can also cause attritional failure of the central slip.

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Pathophysiology

The central slip normally extends the PIP joint.

When it is disrupted, the PIP joint begins to fall into flexion.

As the deformity progresses, the extensor mechanism migrates proximally and volarly relative to the PIP joint.

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Lateral Band Migration

Stretching or disruption of the triangular ligament allows the lateral bands to move volarly around the sides of the PIP joint.

Once the lateral bands subluxate below the axis of rotation of the PIP joint, they act as flexors rather than extensors at that joint.

This further reinforces the PIP flexion deformity.

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DIP Hyperextension

As the extensor mechanism migrates proximally, increased tension is transmitted distally through the lateral bands and terminal tendon.

This produces the characteristic hyperextension deformity of the DIP joint.

The combined pattern of PIP flexion and DIP hyperextension creates the classic boutonniere appearance.

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Diagnosis

History

The history may reveal either a chronic inflammatory process or an acute traumatic injury.

Patients with rheumatoid arthritis may describe a slowly progressive deformity.

In traumatic cases, there is often a history of sudden hyperflexion or direct injury to the PIP joint, followed by immediate difficulty actively extending the joint.

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Signs and Symptoms

The classic clinical appearance consists of PIP joint flexion with DIP joint hyperextension.

In early central slip injury, the deformity may not yet be fully developed.

Patients may initially present only with swelling, pain, and an extensor lag at the PIP joint.

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Physical Examination

Examination should determine whether the deformity is flexible or fixed.

Active and passive motion of both the PIP and DIP joints should be assessed.

The integrity of the central slip and lateral bands can be further evaluated using specialized clinical tests.

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Elson Test

The Elson test is commonly used to confirm a central slip injury.

The PIP joint is flexed to approximately 90°, and the patient is asked to extend the PIP joint against resistance.

The examiner simultaneously assesses the behavior of the DIP joint.

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Elson Test Interpretation

If the central slip remains intact, the DIP joint remains relatively supple or lax during resisted PIP extension.

If the central slip is ruptured, the extensor force is redirected through the lateral bands and terminal tendon.

As a result, the DIP joint becomes rigid or stiff in extension during the maneuver.

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Boyes Test

The Boyes test evaluates whether the lateral bands have become shortened or contracted.

The PIP joint is held in full extension while the patient is asked to actively flex the DIP joint.

If the DIP joint flexes fully, the extensor mechanism remains relatively supple.

If active DIP flexion is limited, contracted lateral bands are likely present.

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Limitations of the Boyes Test

The Boyes test may be negative during the acute phase because significant lateral band contracture has not yet developed.

It becomes more useful in chronic deformity when soft-tissue shortening is established.

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Laboratory Tests

No laboratory study is required to diagnose an isolated boutonniere deformity.

Laboratory investigations may be appropriate only when an underlying systemic inflammatory disorder, such as rheumatoid arthritis, is suspected or already known.

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Imaging

Plain Radiographs

Radiographs are useful for identifying associated structural abnormalities.

They can help exclude a bony avulsion fracture, joint dislocation, or degenerative or inflammatory arthritis.

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Radiographic Technique

Imaging should include the entire involved ray so that the metacarpophalangeal joint, PIP joint, and DIP joint can all be evaluated.

This is especially useful when there is concern for more extensive trauma or underlying arthropathy.

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Differential Diagnosis

The main differential diagnosis is pseudoboutonniere deformity.

This condition also produces inability to fully extend the PIP joint, but the mechanism is different.

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Pseudoboutonniere Deformity

Pseudoboutonniere deformity usually follows a hyperextension injury of the PIP joint.

The problem results from scarring or adhesions involving the volar plate and flexor structures rather than central slip disruption.

Unlike true boutonniere deformity, the DIP joint remains functionally normal and does not develop the characteristic hyperextension pattern.

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Treatment

Acute Injuries

Acute central slip injuries are generally treated with the PIP joint held continuously in full extension for approximately 6 weeks.

During this period, the DIP joint should remain free so that active motion can be performed.

This allows the central slip to heal while minimizing stiffness of the distal joint.

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DIP Motion During Splinting

Active DIP flexion and extension exercises are important while the PIP joint remains immobilized.

These exercises help maintain mobility of the lateral bands and reduce the risk of adhesions or contracture.

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Transition After Initial Immobilization

After approximately 6 weeks of continuous PIP extension splinting, patients typically transition to night splinting.

Progressive PIP joint motion is then introduced.

The amount and pace of motion should be advanced gradually to avoid recurrent deformity.

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Chronic Injuries

Chronic boutonniere deformity should first be assessed for passive correctability.

If full passive PIP extension can still be achieved with stretching or progressive splinting, treatment can often proceed similarly to that used for an acute injury.

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Fixed Chronic Deformity

If the deformity is fixed, serial splinting or casting may be required to gradually restore passive PIP extension before definitive treatment.

Surgery is generally reserved for patients in whom splinting fails or who have a meaningful functional deficit.

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Surgical Expectations

Surgical treatment of chronic boutonniere deformity has guarded results.

Complete correction of the extensor lag should not always be expected.

Because of this, surgery is usually considered only when the deformity produces substantial functional impairment.

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Activity

Heavy lifting and sports activities should be avoided until healing is adequate.

Premature loading or repeated flexion stress may disrupt healing of the central slip and lead to recurrent deformity.

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Occupational Therapy

Occupational or hand therapy plays an important role in management.

Treatment may include custom splinting, stretching, edema control, and progressive motion exercises.

Therapy is particularly important in chronic cases and after surgery.

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Acute Central Slip Injury With Bony Avulsion

When the central slip injury includes a bony avulsion fragment, treatment may involve fracture fixation, splinting, or temporary joint pinning in full extension.

Immobilization is generally maintained for approximately 6 weeks.

The exact approach depends on the size and displacement of the fragment and the stability of the joint.

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Acute Central Slip Injury Without Bony Avulsion

When no fracture is present, many injuries can be treated with extension splinting alone.

In selected cases, temporary joint pinning may be used.

Direct repair of the central slip, including fixation with a suture anchor, may be considered when the tendon has been clearly disrupted and operative treatment is appropriate.

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Open Injuries

Open central slip injuries require irrigation and debridement because of the risk of contamination.

Definitive repair or fixation is then performed as indicated.

Temporary pinning of the PIP joint in extension may be used to protect the repair.

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Chronic Passively Correctable Deformity

A chronic deformity that can still be fully corrected passively may be treated in a manner similar to an acute injury.

Approximately 6 weeks of extension splinting or joint pinning may allow soft-tissue rebalancing.

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Terminal Tendon Tenotomy

In selected chronic cases, a terminal tendon tenotomy may be performed.

The purpose is to reduce excessive extension force at the DIP joint and redirect more of the extensor force toward the PIP joint.

This can improve the balance of the extensor mechanism.

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Fixed Contracture With Tight Lateral Bands

When a fixed PIP flexion contracture is accompanied by shortened lateral bands, treatment often begins with serial casting or progressive splinting.

The goal is to restore passive PIP extension.

Once full extension is achieved, treatment can then proceed using principles similar to those for an acute boutonniere injury.

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Fixed Contracture With Volar Plate or Collateral Tightness

If the deformity includes contracture of the volar plate or collateral ligaments, surgical release of the joint contracture may be required.

Soft-tissue rebalancing may then be performed, sometimes in a staged fashion.

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Boutonniere Deformity With PIP Arthrosis

When a fixed boutonniere deformity is associated with substantial PIP joint arthritis, reconstruction of the extensor mechanism alone may not provide adequate pain relief or function.

In such cases, treatment may require PIP joint arthrodesis or arthroplasty.

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Follow-Up

Conservative treatment generally requires at least 12 weeks of follow-up to ensure that splinting and rehabilitation are completed appropriately.

Patients treated surgically require regular postoperative review to monitor healing, alignment, motion, and recurrence.

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Indications for Referral

Referral to a hand or orthopaedic specialist is appropriate for an acute central slip rupture, especially when the diagnosis is uncertain or a bony avulsion is present.

Referral is also appropriate for a chronic boutonniere deformity that produces significant functional impairment.

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Prognosis

The prognosis is generally better when the injury is recognized and treated early.

Chronic fixed deformities have a more guarded outcome.

Even after surgery, some degree of residual PIP extensor lag may persist.

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Complications

Potential complications include recurrent boutonniere deformity, loss of PIP flexion, and development of a mallet-type deformity at the DIP joint.

Stiffness may also result from prolonged immobilization or chronic joint contracture.

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Recurrent Deformity

Recurrence can occur if the central slip fails to heal adequately or if the PIP joint is mobilized too aggressively.

Continued nighttime splinting and gradual rehabilitation may help reduce this risk.

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Limited PIP Flexion

Prolonged extension splinting or surgical scarring may lead to reduced PIP flexion.

Therapy should therefore balance protection of the central slip with preservation of joint mobility.

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DIP Complications

Alteration of the extensor mechanism can occasionally produce a mallet-type deformity at the DIP joint.

This may occur particularly after certain reconstructive procedures or if distal extensor balance becomes abnormal.

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Patient Monitoring

Patients should be monitored closely for recurrent PIP flexion, increasing DIP hyperextension, loss of motion, or persistent extensor lag.

Early detection of recurrent deformity allows adjustment of splinting or rehabilitation before the deformity becomes fixed.