Sesamoid Surgery

The sesamoid bones are two small, pea-shaped bones located beneath the big toe joint (first metatarso-phalangeal joint or MPJ). They play a critical role in foot biomechanics by providing leverage for the flexor tendons, absorbing impact, and aiding in weight distribution during walking or running. There are two sesamoids:  the lateral sesamoid, located on the outer side of the big toe, and the medial sesamoid which is  located on the inner side of the big toe.   Some people are born with bi-partite sesamoids, which is when one or both of the sesamoid bones are composed of two vs. one bone.

These small bones are prone to fractures due to their position and function. A fractured sesamoid can result from acute trauma, repetitive stress, or overuse, often leading to significant pain, swelling, and difficulty with weight-bearing activities.  There are scenarios where sesamoids are fractured, however there is no pain or difficulty with function.

When conservative treatments such as rest, immobilization, custom orthotics, and physical therapy fail to alleviate symptoms, surgical intervention may be considered. Surgery typically involves either attempting to repair the fractured sesamoid or removing it entirely, depending on the severity of the injury, the patient’s symptoms, and the likelihood of restoring normal function.

Surgical correction to sesamoid injuries is not easy or reliable given the lack of blood flow to these small bones, as well as the anatomical difficulties due to their location.  Repairing a fractured sesamoid aims to restore the bone’s integrity and function while preserving its role in foot biomechanics. This procedure is generally considered when the sesamoid is fractured into large, reparable fragments.

When repair is not feasible due to extensive fragmentation, poor bone quality, or chronic nonunion, removing the lateral sesamoid may be the best option.  This imposes it’s own challenges which will be reviewed later in this consent.

The Procedure

Sesamoid surgery involves a few steps.  The first step is dissection and exposure of the deformity.

This step requires an incision on the medial side of the foot over the MPJ.  This incision is then deepened to the level of the joint capsule.  This is a layer of ligamentous tissue that is thick and covers the entire joint.  The capsule is incised to expose the joint (it will be repaired later).  Dissection is then continued to expose both sesamoids and depending on which one is injured prepare for the procedure.

If the fracture is observable and can be repaired, then an attempt repair is made.  If however it appears that the fracture is not repairable or attempts to repair it will likely not succeed, a decision is made to either further separate the fragments creating an intact sesamoid apparatus, which now operates like a bi-partite sesamoid; or complete excision/removal of the involved sesamoid.   Generally a complete excision/removal is avoided since there can be injury to the flexor tendon that is connected to the sesamoid, and lack of stability once the sesamoid has been removed.

Ultimately these procedures weigh heavily on direct observation, exploration and decision making inside surgery since imaging often does not reveal the complete extend of injury.

Possible Complications Related to Sesamoid Surgery

Altered Foot Biomechanics
Although the goal of the surgery is to improve foot function, changing the structure of the foot can lead to altered biomechanics, potentially causing discomfort or difficulty with certain activities.  They can also lead to stiffness of other joints and/or limited range of motion.

Removing a sesamoid can change the dynamics of the first metatarso-phalangeal joint, potentially leading to issues such as reduced push-off strength, imbalance, or overloading of the medial sesamoid.

Hallux Varus
This complication can be due to contracture of the tissues on the side of the first metatarsal-phalangeal joint, causing a drifting of the toe in the opposite direction of a bunion deformity.  Almost all hallux varus complications can be resolved with either conservative or surgical revision.