Sesamoid bones are commonly found in and around joints. While sesamoid bones can be found around any joint in the foot, they are consistently found within the joint of the great toe. The great toe joint contains 2 sesamoid bones, the tibial and fibular sesamoids.
The sesamoids serve 2 very important functions based on their location:
- they serve to protect the large tendon to the great toe, the Flexor Hallucis Longus, which functions to pull the toe down against the ground during gait. The tendon courses between these two bones
- they also serve as a fulcrum for the short flexor tendon, Flexor Hallucis Brevis, which attaches to the base of the great toe. This tendon stabilizes the toe against the ground at the push-off phase of gait and allows for effective forward propulsion of the body.
Because of their location and the amount of force transmitted through these bones, they are susceptible to a variety of injuries. Additionally, certain foot structures and activities will increase the susceptibility of these bones. Fractures and inflammation (sesamoiditis) are quite common. Fractures of a sesamoid bone can involve either the tibial or fibular sesamoid. This is an actual break within the bone. Because the flexor hallucis brevis tendon is attached to the sesamoids, there is often displacement of the fracture, leading to a high rate of delayed or even nonunion.
Sesamoiditis is an inflammatory condition of the periosteum or bone lining of the sesamoid bone. Typically, patients will relate a history of excessive activity as a precursor to pain in this location. Other risk factors include: running, jumping from a height, ballet dancing, wearing of high heels or shoes with little cushioning and high-arched foot type. With early and appropriate treatment, these often improve.
Initial diagnosis is made by a careful history and physical examination. Pain localized to the bottom of the great toe joint is the typically presentation of these types of injury. The pain can be easily localized to either the tibial or fibular sesamoid by directly pressing on either bone. Movement of the joint may also duplicate the patient’s pain. Occasionally, swelling and redness may also be seen depending on the mechanism of injury. X-rays are often obtained to differentiate sesamoiditis from a sesamoid fracture. Three different views of the sesamoids are commonly taken. Also, when sesamoid fractures are suspected, it is helpful to x-ray the uninvolved side as well. Typically, the sesamoid bones are 2 well-defined bones on x-ray. This is the case for approximately 85% of the population. However, in 15% of patients each sesamoid bone may consist of 2 or more fragments (referred to as multipartite – several pieces). This will often make the distinction between normal and fracture difficult. In this case, a bone scan or MRI can be helpful. It is important to differentiate between sesamoiditis versus fracture since the treatment is dramatically different.
The treatment of sesamoid injuries is dependent on making a definitive diagnosis. Because sesamoiditis is an inflammatory condition, treatment directed at reducing inflammation is often helpful. This may include: rest, ice, anti-inflammatory medications and physical therapy. More resistant cases of sesamoiditis may be helped by an occasional cortisone injection. These should only be performed after the physician is fairly certain a fracture does not exist.
Long-term therapy must be geared to identifying the cause of the sesamoiditis so as to avoid these situations or to accommodate foot deformities or modify shoes. This may include the use of orthotic devices. This may also include the limited use of high heel shoes.
Sesamoid fractures require a more aggressive course of treatment because of the high risk of nonunion. Cast immobilization for 6-8 weeks is the initial treatment of choice. The patient should then be advanced gradually to full weight-bearing with a removable brace. Even in spite of appropriate treatment, many sesamoid fractures go on to delayed or non-unions. When conservative care has failed to render the patient pain free, consideration to removal of the offending sesamoid should be given. Once again, long-term therapy should be geared at identifying the cause of the fracture and treating or modifying those activities leading to the fracture in the first place.