- 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;
Fractures of the sesmoid bones of the thumb.
PR Dong et al.
American J. of Sports Med.
Vol 23(3): p 336-339. May-Jun 1995.
Tension wire fixation of avulsion fractures at the thumb MP joint.
SH Kozin and AT Bishop.
J. Hand Surg. Am Vol. Vol 19(6) p 1027-1031. Nov 1994.
