How is boutonniere deformity in rheumatoid arthritis (RA) treated?

Updated: Jan 11, 2019
  • Author: Michael Neumeister, MD, FRCSC, FACS; Chief Editor: Joseph A Molnar, MD, PhD, FACS  more...
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Answer

Answer

The same disease processes in RA that result in swan-neck deformity also cause the converse deformity, the boutonniere, in which the PIP joint is flexed and the DIP and MP joints are hyperextended. This abnormal finger posture usually starts with PIP joint flexion that leads to the changes in the other joints. Specifically, synovial proliferation in the PIP joint stretches and weakens the extensor mechanism; therefore, full extension cannot be maintained. Then, the lateral bands are displaced volarly and the oblique retinacular ligaments are shortened, which causes hyperextension of the DIP joint. In compensation for increasing PIP joint flexion, the MP joint hyperextends. Generally, if the problem is corrected early, passive treatments are adequate. In the later stages, salvage procedures are indicated.

With mild boutonniere deformity, minimal distortion of the joint positions and functional loss occur. A slight extensor lag (10-15°) is present at the PIP joint with slight hyperextension at the DIP joint and no involvement of the MP joint. Surgical treatment usually consists of extensor tenotomy, which should not threaten existing function while increasing DIP joint flexion.

With moderate boutonniere deformity, the flexion deformity at the PIP joint increases to 30-40° and the MP joint begins to hyperextend in order to compensate. At this stage, reconstruction of the extensor mechanism by shortening the central slip and moving the lateral bands dorsally is indicated to restore PIP extension and hand function. Certain criteria should be met before correction is attempted, including good dorsal skin, smooth joint surfaces, functional flexor tendons, and the ability to passively correct the PIP joint. [2] If wrist deformity is present, it should be corrected before addressing the PIP extensor mechanism. Conversely, PIP joint flexion should be corrected before MP joint arthroplasty because achieving adequate MP joint flexion while the PIP joint is also flexed is difficult.

When the PIP joint can no longer be passively extended, the boutonniere deformity is severe. Fusion of the joint or arthroplasty is now warranted. Fusion of the PIP joint should be performed so that the treated finger is in a functional or flexed position. The degree of flexion should increase from the index finger (25°) to small finger (40°). [2] Postfusion, patients often regain MP joint function. If PIP joint arthroplasty is chosen in order to maintain motion, the extensor mechanism should also be repaired. This option is particularly useful for boutonniere deformities of the small and ring fingers to maintain or improve grip strength.


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