The human foot has 2 small sesamoid bones, which sit under the big toe joint of each foot. They are encased within the flexor tendons which help to pull the big toe downward. Each sesamoid bone is about the size of a kidney bean. Sometimes, they get injured by a direct blow to the area i.e. when landing from an excessive height or stepping hard on an object such as a stone. Other times, the sesamoid bones get irritated from the repetitive stress of running, jumping or pivoting particularly in shoes or orthotics that does not supply an adequate amount of cushioning. Those most vulnerable to sesamoid injuries are anybody with a high arched foot. Here, the declination of the metatarsals is more downward causing abnormal pressures to the metatarsal heads. It is also common in individuals whose arches collapse excessively (over pronate). Here, there are increased repetitive pressures to the sesamoid bones and big toe joint on push-off. This “microtrauma” stress can lead to either inflammation of one or both of the sesamoid bones (sesamoiditis) and/or a stress fracture. Rubbing of an enlarged or malpositioned sesamoid bone against the bottom of the first metatarsal head can lead to arthritis.
It has been estimated that 7% to 20% of people are born with a sesamoid bone that is split in 2 portions called a “bipartite sesamoid”. Often times, repetitive activities such as pushups or lunging type movements cause the 2 halves of the sesamoid bone to separate further causing pain very similar to a fracture.
Sesamoid injuries are diagnosed by x-rays of the foot in multiple positions as well as by MRI and CT scan. Once the diagnosis is confirmed, treatment in the office is begun by padding the sesamoids to reduce pressures. Treatment also includes custom orthotic devices, which redistribute pressures across the entire forefoot and back into the arch thereby alleviating unwanted pressures to the sesamoid bones. Icing the area and anti-inflammatory medicine may be helpful. Because this is a very small joint, a corticosteroid injection maybe given under fluoroscopic (x-ray) guidance to ensure proper placement of the medicine to help reduce pain and inflammation.
If the pains are chronic, it is possible that an old fracture may have healed with an enlarged bony prominence (this is a result of calcium deposits trying to bridge together the fracture ends). In this scenario, patients often relate that it feels as if they are walking on a pebble. When conservative treatment fails then we have performed multiple types of sesamoid surgeries. Sometimes remodeling of the sesamoid bone(s) and/or excision of part or all of the sesamoid bone are performed with great success. Following surgery, it is important to wear orthotic devices to help rebalance the forefoot. Should you or anyone you know suffer from the debilitating symptoms of sesamoid injury, please do not hesitate to contact our office.
Written by Richard T. Braver, DPM, FACFAS