A boutonniere deformity is a complex imbalance between the flexor and extensor mechanisms of the finger. Often the middle joint of the finger is flexed too much (PIP hyperflexion) and the distal joint is slightly extended beyond neutral (DIP hyperextension).
The problem with Boutonniere deformities is that most patients neglect them as a “sprained finger”. The specific difference between a sprain and a Boutonniere injury is the latter is associated with a rupture of the tendon that extends the middle, PIP joint.
With the tendon rupture the first thing to happen is that you cannot actively extend the finger. One of the classic findings is the ability to passively extend the joint, but a loss of active extension. Furthermore you can find tenderness over the back of the joint.
On the positive side, surgery is usually not needed in most cases. On the other side, the treatment is full time splinting of the joint keeping the finger completely straight at the PIP joint but encouraging flexion of the tip joint. This helps mobilize the tendon to facilitate healing.
The splint needs to be worn 24/7 often for approximately 6 weeks. Our goal is a full restoration of motion, but honestly most patients do lose a permanent motion of the finger. By participating in the splinting and formal therapy program, we can usually minimize the functional loss.