Boutonniere (Buttonhole) Deformity Treatment & Management

In the setting of an acute injury to the central slip, conservative management should be employed in an attempt to permit tendon healing before the onset of a boutonnière (buttonhole) deformity (BD). Left untreated, an injury to the central slip can result in a BD within 2-3 weeks.

For an acute injury with a supple digit, management consists of either splinting or pinning of the proximal interphalangeal (PIP) joint in full extension for 4-6 weeks (see the image below). During this time, the distal interphalangeal (DIP) joint is not splinted; rather, this joint is taken through frequent flexion/extension exercises.

Bunnell safety-pin splint.

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With the contralateral index finger stabilizing the PIP joint in full extension and the contralateral thumb placed on the volar aspect of the DIP joint, the patient actively flexes the DIP joint. This exercise protocol stabilizes the PIP joint and the central slip while stretching the lateral bands and the oblique retinacular ligaments, preventing contracture and the pathologic boutonnière posture. Thereafter, PIP joint flexion exercises are introduced; however, PIP joint extension splinting is continued at night for an additional 4-8 weeks. ^{[13, 14]}

In the case of a large avulsion of the dorsal lip of the middle phalanx, fixation with a Kirschner wire (K-wire) or screw fixation can be employed to reconstitute the extensor mechanism. If the fragment is small and nondisplaced, the injury can be managed nonoperatively with the splinting protocol as described above.

Open injuries should always be irrigated appropriately. The central slip should be repaired if it is completely lacerated. The proximal central slip tendon can be directly repaired to the residual central slip distally, or if there is insufficient tendon distally, the proximal end of the central slip can be anchored directly to the middle phalanx. In concert with nonoperative management, the PIP joint should be maintained in full extension to permit healing.

Classification

BDs can be categorized according to the Burton classification, as follows ^[15] :

• Burton stage I - BD with a supple and passively correctable joint
• Burton stage II - BD with a fixed contracture and contracted lateral bands; PIP joint spaces are maintained
• Burton stage III - BD with a fixed deformity, contractures of lateral bands, volar plate and collateral ligaments; the PIP joint suffers from intra-articular fibrosis
• Burton stage IV - BD with a fixed deformity, contractures of lateral bands, volar plate and collateral ligaments; the PIP joint suffers from intra-articular fibrosis and arthritis as evident on radiography

The Burton classification is based on the clinical examination and plain radiographs. Ultimately, surgical management is guided by the degree of deformity at the PIP joint, the suppleness or correctability of the joints, and the presence of arthritis at the PIP joint. ^{[5, 16]}

Management

For many patients, a BD does not impart excessive functional deficits; however, for those patients that suffer moderate-to-severe functional deficits, an operative approach may be indicated. In such instances, a detailed conversation with an orthopedic hand surgeon should be pursued to explore the options and to arrive at appropriate expectations.

In the setting of a mild deformity, in which the PIP joint can be corrected passively, patients may still suffer from an extensor lag at the PIP joint and from hyperextension at the DIP joint. Because the functional limitation is secondary to the lack of PIP joint extension and DIP joint flexion, management is aimed at correcting these deformities.

To relieve the hyperextension at the DIP joint and to permit increased flexion, an extensor tenotomy overlying the middle phalanx can be performed. The extensor tenotomy is performed through a midaxial longitudinal incision overlying the dorsum of the middle phalanx, lengthening the extensor mechanism and returning a degree of flexion to the DIP joint. Because the flexion deformity at the PIP joint is, by definition, passively correctable in a mild deformity, dynamic splinting is utilized to reduce the extension lag. ^{[17, 18]}

In patients with a moderate BD, the PIP joint flexion deformity may exceed 30-40°. Nonetheless, if the PIP joint is passively correctable, the BD is amenable to soft-tissue reconstruction.

Operative management entails reconstruction of the extensor mechanism through shortening of the central slip and reduction of the lateral bands dorsally. ^[19] It is vital to the functionality of the digit that PIP joint flexion be preserved; accordingly, such a reconstruction should not be performed in a patient with an incompetent flexor mechanism. This operation is often coupled with an extensor tenotomy to enable functional DIP flexion.

Severe BDs involve fixed contractures and may exhibit PIP joint arthrosis on radiographs. Fixed deformities are not amenable to the soft-tissue reconstruction techniques described above. In an attempt to achieve extension at the PIP joint, dynamic splinting or serial casting may be employed to achieve passive extension. This may be coupled with soft-tissue releases, including releases of the accessory collateral ligaments.

In the setting of PIP arthrosis, management consists of fusion or arthroplasty. In PIP fusion, the joint is fused in relative flexion to permit grasping of objects. Splinting is utilized to allow union to occur over a period of 4-6 weeks. PIP joint arthroplasty, on the other hand, entails a more extensive approach, in that the surgeon must recreate and maintain functional motion at the PIP joint. Consequently, soft-tissue reconstruction is once again necessary and includes shortening of the central slip and reduction of the lateral bands dorsally.

The full course of treatment of a BD should be discussed at the initiation of therapy. Patients will often wear a static splint maintaining full PIP extension after an operation to allow for healing. Thereafter, patients will proceed to intermittent splinting and undergo passive stretching exercises. Throughout the course of treatment, dedicated hand therapy is integral to the management and correction of a BD.

Correction of a BD is not without complexity. While there is an attempt at improvement in function, patients may experience any of the following:

• Continued debility
• Incomplete correction of the deformity
• Recurrence of the deformity
• Loss of mobility—specifically, flexion at the PIP joint or extension at the DIP joint
• Chronic pain
• Infection at the site of open injury or the surgical site
• Reoperation