Overview
This lecture focuses on the examination of extensor tendons in the hand, highlighting their anatomy, function, common injuries, and clinical tests for assessment.
Extensor Tendon Anatomy
- Extensor tendons run along the back of the fingers, receiving contributions from lumbricals and interossei muscles.
- At the proximal phalanx, the extensor expansion or "hood" splits into three: central slip (middle phalanx) and two lateral bands (distal phalanx).
- The long extensor is responsible for finger extension at the metacarpophalangeal (MCP) joint.
Clinical Examination and Injuries
- Inability to extend at the MCP joint indicates injury to the long extensor tendon.
- Inability to extend at the proximal interphalangeal (PIP) joint suggests central slip injury.
- Central slip injuries can be masked by secondary pull from other structures, allowing some PIP extension.
- The Elson test helps diagnose central slip injuries when standard extension is preserved.
- Central slip injury may result in a boutonnière deformity: PIP flexion with distal interphalangeal (DIP) hyperextension.
- Injury distal to the central slip causes inability to extend at the DIP joint, known as mallet finger.
- Mallet finger may eventually cause swan-neck deformity: hyperextension of PIP and flexion of DIP.
Diagnostic Maneuvers
- Modified Elson test: flex PIP, ask patient to extend DIP; inability to extend indicates central slip injury.
- Another method: flex both PIP joints of adjacent fingers, push nails together, and check for asymmetry in DIP extension.
Key Terms & Definitions
- Extensor Tendon — tendon that straightens the fingers, located on the back of the hand.
- Central Slip — part of extensor mechanism inserting into the middle phalanx.
- Mallet Finger — inability to extend the DIP joint due to distal extensor tendon injury.
- Boutonnière Deformity — PIP joint flexion with DIP joint hyperextension, often from central slip injury.
- Elson Test — clinical test for central slip integrity.
- Swan-Neck Deformity — PIP hyperextension and DIP flexion, seen in chronic mallet finger.
Action Items / Next Steps
- Review the anatomy of hand extensor tendons.
- Practice Elson test and its modifications in a lab or clinical setting.
- Watch the detailed video on the Elson test as referenced in the lecture.