The Clinical Syndrome

Sesamoid bones are small, rounded structures embedded in the flexor tendons of the hand, usually in close proximity to the joints ( Fig. 57.1 ). The name sesamoid was first used by second century physician Galen to underscore these bones’ resemblance to sesame seeds. These bones serve to decrease the friction and pressure of the flexor tendon as it passes in proximity to a joint. Most patients have two sesamoid bones at the metacarpal phalangeal joint, one at the interphalangeal joint of the thumb, one at the metacarpophalangeal joint of the index finger, and one at the metacarpophalangeal joint of the little finger. These bones are subject to fracture, dislocation, tumors, avascular necrosis, inflammation, and associated tendinitis, all of which can cause hand pain and functional disability ( Fig. 57.2 ).

The sesamoid bones of the hand (arrows).

(From Ozcanli H, Sekerci R, Keles N. Sesamoid disorders of the hand. J Hand Surg Am 2015;40(6):1231–2123.)

Computed tomography and reconstruction views showing proximal displacement of the radial sesamoid of the thumb.

(From Deshmukh NV, Saikia AN, Norton ER, Sonanis SV. Sesamoid displacement: a rare cause of “clicking thumb.” Injury. 1999; 30(2):141–143.)

Sesamoiditis is characterized by tenderness and pain over the flexor aspect of the thumb or, much less commonly, the index finger ( Fig. 57.3 ). When grasping something, the patient often feels that he or she has a foreign body embedded in the affected digit. The pain of sesamoiditis worsens with repeated flexion and extension of the affected digit. When the thumb is affected, it is usually on the radial side, where the condyle of the adjacent metacarpal is less obtrusive. Patients suffering from psoriatic arthritis may have a higher incidence of sesamoiditis of the hand.

Sesamoiditis is characterized by tenderness and pain over the flexor aspect of the thumb.

(From Waldman SD. Atlas of pain management injection techniques . 2nd ed. Philadelphia: Saunders; 2007:238.)

Signs and Symptoms

On physical examination, pain can be reproduced by pressure on the sesamoid bone. In patients with sesamoiditis, the tender area moves with the flexor tendon when the patient actively flexes the thumb or finger, whereas with occult bony disease of the phalanges, the tender area remains over the pathologic area. Clicking and triggering of the affected digit may be present on passive and active flexion and extension. With acute trauma to the sesamoid, ecchymosis over the flexor surface of the affected digit may be present.