What is the relevant anatomy of the thumb in trigger finger (TF)?

Updated: Apr 26, 2021
  • Author: Satishchandra Kale, MD, MBBS, MBA, MCh(Orth), FRCS(Edin), FRCS(Tr&Orth); Chief Editor: Harris Gellman, MD  more...
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Answer

The flexor anatomy of the thumb differs from that of the fingers. The flexor pollicis longus (FPL) tendon is a single tendon within the flexor sheath that inserts onto the base of the distal phalanx. The fibro-osseous sheath is composed of two annular pulleys (A1 and A2) that arise from the palmar plates of the MCP and interphalangeal (IP) joints, respectively. The oblique pulley, which originates from and inserts onto the proximal phalanx, is the most important pulley from a biomechanical perspective. The oblique pulley is approximately 10 mm in length, blending with a portion of the adductor pollicis insertion.

The digital nerves and arteries run parallel to the tendon sheath distally. At the level of the MCP flexion crease, they lie just deep to the skin. Proximal to the A1 pulley, the radial digital nerve of the thumb crosses obliquely over the sheath.


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