Fractures of the Sesamoid Bones of Thumb



- Anatomy:
    - sesamoids of MP joint of thumb lie with in lateral margins of palmar plate at origin of fibrous tunnel of flexor pollicis longus;
    - accessory collateral ligaments insert into lateral margins of sesamoids;
    - tendon of adductor pollicis inserts on ulnar sesamoid
    - tendon of FPB inserts on the radial sesamoid;

- Fracture Patterns:
    - frx results from hyperextension injury to MP joint of thumb and is often associated w/ dislocation of thumb MP joint;
    - frx of sesamoids may be associated w/ rupture of palmar plate or rupture of accessory collateral ligaments;
    - type I:
           - palmar plate is intact;
           - pt maintains normal flexion posture of MP joint, and ability to flex MP & IP joint;
    - type II:
           - palmar plate is ruptured;
           - MP joint assumes hyperextension posture, & pt is unable to flex IP;

- Clinical Exam & Presentation:
    - ecchymosis is seen on flexor side of joint extending to thenar eminence;
    - tenderness over one or both sesamoid bones;
    - joint is examined for palmar plate and collateral ligament disruption;

- Radiographs:
    - radial & ulnar oblique views of MP joint;
    - comparative views of opposite thumb are helpful to r/o bipartite sesamoids


Tension wire fixation of avulsion fractures at the thumb metacarpophalangeal joint

Fractures of the sesmoid bones of the thumb.



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Thursday, October 4, 2012 5:24 pm