The central slip is an important part of the extensor mechanism of the finger that inserts over the middle joint of the finger, the proximal interphalangeal joint (PIP). It plays an important role in extending, or straightening, this joint. Damage to this structure can occur due to a deep cut over the PIP joint, a jammed finger, or even as a long-term consequence of Rheumatoid Arthritis. A central slip injury or rupture can also be called a Zone 3 extensor tendon injury.
If left untreated, the finger can become stiff and remain bent in a certain way, this is called a Boutonnière Deformity. This occurs when the PIP joint is bent, and the tip joint (the DIP joint) also becomes hyperextended over time due to an imbalance of forces of the soft tissues within the finger. This can be quite functionally limiting.
Symptoms / Presentation:
- Inability to actively extend the PIP joint completely
- Pain, tenderness and swelling over the back of the PIP joint
- In an established Boutonnière Deformity, the PIP is bent and the DIP is hyperextended. It may or may not be able to be passively corrected
Your therapist can perform simple clinical tests which can diagnose a central slip disruption; however imaging may also be helpful. Early therapy intervention can help prevent a Boutonnière Deformity from occurring.
If your injury can be conservatively managed, your therapist will fabricate you a static splint (still) to keep that joint straight in order to allow your tendon to heal. You will need to wear this as instructed to avoid any complications.
If this is a chronic Boutonnière Deformity, your therapist will discuss options with you which may include a dynamic extension splint, called a capener splint. This splint will help gently stretch the stiff joint, and your therapist will also provide specific exercises.
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