IS Case 554: Bipartite sesamoid of the foot
Imaging Sciences URMC 2010
Publication Date: 2010-09-25
Bipartite sesamoid of the foot
In most people, there are two sesamoid bones located at the first metatarsal joint, the tibial and fibular sesamoids. These sesamoids of the foot are located within the tendons of the flexor hallucis brevis. The function of the sesamoids is to help with weight-bearing under the first metatarsal. A bipartite sesamoid is a common variant seen in about 25% of the population, in which we see two small sesamoid bones replacing either the tibial sesamoid or the fibular sesamoid. It is more common in the tibial sesamoid and is usually bilateral.
The presence of a bipartite sesamoid in the foot is usually an incidental finding on a foot radiograph. However, a sesamoid fracture should be excluded before being convinced that it is a bipartite sesamoid. A fracture would usually have irregular margins compared to a normal variant of bipartite sesamoid. Hallux abducto valgus deformity is associated with tibial sesamoids in most patients.
Bipartite sesamoids can sometimes become symptomatic with pain on weight-bearing at the first metatarsophalangeal (MTP) joint area, that is relieved by rest. Conservative approaches are first used for symptomatic bipartite sesamoids. Surgical excision is used as the last step.
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