About Boutonniere Deformity
The boutonniere is a French word for botton hole. The term is used to describe this deformity because the lateral bands separate, like a buttonhole, allowing the joint to protrude between them. Initially, the boutonniere deformity involves a flexion deformity of the PIP joint and hyperextension of the DIP joint. However, with chronicity , the PIP joint becomes a fixed contracture necessitating hyperextension of the MCP joint to achive grasp. The boutonniere deformity differs from the swan neck deformity in that the primary etiology is in the PIP joint. The inflammatory process damages the extensor structures to the PIP joint and weakens their attachments. Synovial hypertrophy distends the dorsal capsule mechanically, thus stretching or displacing the extensor structures.
Boutonniere Deformity Cause
Another deformity of the finger in rheumatoid arthritis is the boutonniere deformity, the boutonniere deformity is caused by a rupture or lengthening of the central slip of the EDC tendon. The test for this the client should actively extend the finger. Loss of active PIP extension is indicative of rupture. The central slip of the extensor tendon is ruptured as a result of inflammatory infiltration or bony spurs. Therefore it cannot function to extend the PIP joint on which it acts. The lateral slips slide volarly below the normal angle of pull and act to flex the PIP joint and hyperextend the DIP joint, resulting in typical boutonniere appearance.
The boutonniere deformity can occure when synovitis at the wrist, MP, or PIP joints weakens or destroy the central slip of the extensor tendon that inserts into the base of the middle phalanx. There is often associated with PIP joint arthritis. The boutonniere deformity can result from injuries caused by division, rupture, avulsion, laceration, or closed trauma to the central extensor tendon inserting on to the middle phalanx. Dorsal burns, rheumatoid arthritis, dupuytren’s contracture, and congenital disease are other causes.
Boutonniere Deformity Classified
Several authors have classified different clinical stages of the boutonniere deformity. Tubiana classifies boutonniere deformity into four stages ; stage 1, minimal deficiency of extension ; sage 2, proximal contracture of the middle extensor tendon ; stage 3, contracture of the retinacular ligaments ; stage 4, fixed contracture of the proximal interphalangeal joint. Litter and Eaton have explained this as a three stage process ; stage 1, loss of the central slip results in unopposed PIP flexion by the superficialis tendon; stage 2, volar migration of the lateral bands secondary to transverse retinacular ligament and triangular ligament laxity; and stage 3, intrinsic tendon pull is now directly solely at the distal interphalangeal joint with resultant hyperextension movement. The deformity is described as mild if the loss is 5 to 10 degree, as moderate if the loss is 10 to 30 degree, and as severe if 30 degree or more is lost.
Despite different classifications and numerous surgical techniques for correction of the boutonniere deformity, it appears that most authors’ treatment of choice is conservative long term hand therapy to increase PIP extension and DIP active ful flexion with external splinting. Only when an acute, open injury occurs should immediate surgery be performed. The boutonniere deformity is the most difficult deformity to treat conservatively. Part of the reason is that by the time the lateral bands have displaced sufficiently to create a boutonniere, significant stretching of the supporting fibers has already taken place. Occupational therapists at the University of Michigan, Ann Arbor, have conducted a study evaluating the effectiveness of a 6 weeek extension orthotic immobilization program for reducible early ( less than 20 degree loss of extension ) boutonniere deformity. They found the program effective in reducing the deformity, but prolonged intermittent splinting was necessary to prevent it is return.