Sesamoid bones are found embedded in the tendons near many joints. They function to protect the tendon and enhance its mechanical effect. Most sesamoid bones are small and resemble grains of sesame; the meaning of the word's greek root is "shaped like a sesame." The two largest sesamoids in the foot reside near the first metatarsophalangeal (MTP) joint and are susceptible to fracture.
This topic review will discuss sesamoid fractures of the foot in adults. Other foot fractures are discussed elsewhere. (See "Toe fractures in adults" and "Stress fractures of the metatarsal shaft" and "Metatarsal shaft fractures".)
There are two relatively large sesamoids adjacent to the first metatarsophalangeal (MTP) joint (image 1). Injuries to these sesamoids comprise 12 percent of injuries to the great toe complex . Small sesamoids are occasionally seen elsewhere in the foot, most notably beneath the fifth MTP joint (image 2A-C). These smaller sesamoids are rarely of clinical significance (figure 1A-C).
The sesamoids of the first MTP joint are embedded within the tendon of the flexor hallucis brevis and allow for increased dorsiflexion of the MTP. They are also involved in shock absorption, reduction of friction, and protection of tendons . The medial (ie, tibial) sesamoid is thought to bear greater force during the normal gait cycle and is more commonly fractured from either direct force or cumulative stress [3,4]. The lateral (ie, fibular) sesamoid is injured much less often.
It is important to recognize that sesamoids are sometimes "partite," ie, one sesamoid is made up of two or three separate pieces (image 3). A study of 35 cadaveric feet found the incidence of partite sesamoids to be 11.1 percent . This finding is comparable to other studies. Partite sesamoids are frequently bilateral. Hence, bilateral comparison views are sometimes helpful in distinguishing a partite from a fractured sesamoid. (See 'Partite sesamoids' below.)