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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.