People who have rheumatoid arthritis of the hands often develop a finger deformity referred to as a Boutonniere deformity. The name comes from a French word for "button hole". We will explain that further after we describe the deformity.
When the affected finger is viewed from the side, it has a zig-zag appearance. That's because the joint of the middle knuckle of the finger (called the proximal interphalangeal or PIP joint) is permanently bent toward the palm while the tip of the finger (as the distal interphalangeal or DIP joint) is bent back or hyperextended.
This flexion deformity of the middle joint (the proximal interphalangeal or PIP joint) occurs when the central slip of the extensor tendon separates. The head of the proximal phalanx (middle finger) bone literally pops through the gap. It's like a finger through a button hole and thus the name boutonniere.
The tip of the finger is then drawn into hyperextension because the two slips of the extensor tendon on either side of the separated central tendon are stretched by the head of the proximal phalanx. The two peripheral slips attach to the distal phalanx (finger tip bone), while the proximal slip is inserted into the middle phalanx. This deformity makes it difficult or impossible to extend the proximal interphalangeal (PIP) joint and bend the finger tip.
You can imagine how difficult it is to perform daily activities that require flexibility of the fingers. Try picking anything up with your fingers stuck in a Boutonniere position. Better yet, try using a key to unlock a door or turn a door knob. You will probably have to put anything down you are carrying and use two hands together.
What can be done about this problem? Treatment depends on how severe the deformity is, how much motion there is at each joint, and whether or not the joint can be passively straightened. Fingers that can be stretched or moved back to their normal resting position may benefit from hand therapy and splinting.
But fingers that are in a Boutonniere position and can't be moved to a normal position are considered contracted. Surgery becomes the only option at that point. The surgical choices include synovectomy, tenotomy, or reconstruction of the extensor tendon. If the deformity is severe, then a joint fusion (called arthrodesis) or joint replacement (arthroplasty) may be required. These two procedures are referred to as salvage surgery).
Surgeons use a special classification system to decide just how severe is the deformity and therefore which surgical procedure to choose. There are three stages of Boutonniere deformity. Stage one (mild) is correctable with passive motion. The joint surface is normal without any signs of joint damage or degeneration.
Stage two Boutonniere deformity is considered moderate in severity. The joints can be partially returned to their normal anatomic position (neutral). And the articular (joint) surface remains unchanged. In the early phase of stage two deformity, it may still be possible to convert to a stage one deformity with conservative (nonoperative) care.
Stage three is defined by a fixed contracture (does not correct with passive motion) and the joint surface is damaged to the point of destruction. This is the stage that most often requires surgical intervention.
Stages one and two may still respond to hand therapy, splinting, and/or steroid injection of the joint. If stage one and stage two deformities fail to respond to conservative care, then surgery may be recommended for them, too.
When choosing the surgical technique for each patient, the surgeon takes into consideration the condition of the most affected joint, the adjacent joints, the skin, joint motion, and overall hand function.
One of the most commonly used approaches is to make an incision over the proximal interphalangeal (PIP) joint and remove the extra piece of central tendon where it has separated. The tendon is reattached where it can function best. The surgeon also corrects the tendon pull on the distal phalanx (tip of the finger).
Every effort is made to restore as much normal motion as possible to the two joints affected. Studies show that results of surgery are best when the procedures are done before the deformities become fixed contractures. But when all else fails and the finger is stuck and nonfunctional, it may be necessary to proceed to a joint fusion or replacement. Silicone implants are recommended by most surgeons who perform these replacement procedures.
Patients facing surgery for boutonniere deformities should be aware of a couple things. First, no matter what type of surgery is done, there is often a residual deformity called extensor lag at the tip of the finger. That means when the patient tries to extend or straighten the tip of the finger, it now moves but it doesn't straighten all the way. Instead there is still a small amount of flexion at the finger tip.
And even if the patient has had hand therapy before surgery, further rehabilitation will be necessary after surgery. Once again, the hand therapist will use splinting, exercises, and specific therapeutic activities to help patients regain lost motion and maximize function. Patients usually wear splints 24/7 for at least four weeks to protect the healing tendon. A special splint for night time use may be prescribed for another four to eight weeks. Overall results vary but most patients can expect a good or satisfactory result.
Reference: Keoni Williams, MD, and Andrew L. Terrono, MD. Treatment of Boutonniere Finger Deformity in Rheumatoid Arthritis. In The Journal of Hand Surgery. August 2011. Vol. 36A. No. 8. Pp. 1388-1393.