Injury: Sesamoid Injury, Sesamoiditis, Sesamoid Fracture
Anatomy
The foot has multiple bones that can become injured during sports activity, however, this post will focus on two small bones at the "ball" of the foot called sesamoid bones. A sesamoid bone is an independent bone that is embedded within a tendon or a muscle usually where that tendon crosses a joint. An example of a sesamoid bone is actually the patella (knee cap). The sesamoid bones of the foot are situated at the big toe joint on the undersurface of the foot, which can be seen in the foot model above. They are located within the flexor tendons of the big toe. The primary purposes of these sesamoid bones are to help with shock absorption as well as leverage and mechanics of the big toe with running and walking activities. Below you will see an x-ray showing the typical appearance of the sesamoid bones within the foot.
X-Ray Image of Sesamoid Bones
Types of Sesamoid Injuries
A sesamoid injury can occur with overuse of the ball of the foot. In general, inflammation around the sesamoid bones that occurs from chronic overuse is referred to as sesamoiditis. The painful condition can develop from the pounding and cutting of running sports. I tend to see this injury most commonly in dancers, runners, gymnasts and basketball athletes. The pain is usually reported as a dull and achy pain at the ball of the foot. Untreated sesamoiditis can progress to an actual stress fracture of the bone. On the other hand, a sesamoid fracture can occur secondary to a traumatic event. One mechanism of injury is a forceful toe off or extension of the big toe causing a pull on the sesamoid bone creating a fracture. Of note, a normal condition called a bipartite sesamoid can be confused for a fracture. Although a bipartite sesamoid can predispose individuals to sesamoiditis, many athletes have a bipartite sesamoid that is completely pain-free. You will note in the pictures below, a bipartite sesamoid will usually have two separate pieces with smooth edges, rather than the asymmetric appearance and rough edges of a fractured sesamoid.
Sesamoid Fracture
Bipartite Sesamoid
Examination
In general, a full examination of the ankle and lower leg should be performed. However, there are a few key findings that can help determine sesamoid injury. One common finding is swelling and bruising at the site of the injury. The classic physical examination finding in patients with a sesamoid injury is tenderness directly over the ball of the foot (see below). Pain may also be elicited with extension of the great toe. Keep in mind the diagnosis of turf toe can be easily mistaken for sesamoiditis and takes a careful examination.
Evaluation
Plain x-rays can be helpful in determining the presence of a bipartite sesamoid as well as a fractured sesamoid. The sesamoid bones can be seen on a standard foot x-ray series, however, there is a dedicated sesamoid x-ray series with additional views that may be helpful to the clinician. An x-ray will not show the soft tissue, such as tendons, that surrounds the sesamoid bone. One may consider an MRI of the foot to help determine the presence of soft tissue inflammation or a stress fracture of the sesamoid. However, a thoughtful clinician may realize that the treatment plan may not change based on the outcome of the MRI, therefore resulting in the MRI being unnecessary.
Treatment
Typically sesamoiditis is generally managed with a conservative course of treatment. Minor irritation can include minimal treatment with a foam donut pad supporting the ball of the foot and allowing less pressure over the sesamoid bones. If this intervention provides relief, it is certainly possible to allow sports participation if approved by the treating provider. Treatment of more severe pain usually involves some form of boot or hard-soled shoe. The rigid sole helps to eliminate flexion and extension of the big toe. Athletes may use additional treatments such as ice baths and physical therapy techniques to expedite the healing process. In general, fractures are most commonly treated with boot immobilization, however, a short leg cast may be used in some circumstances. The benefit of the boot is that the athlete can maintain ankle strength with physical therapy exercises during the healing process.
In rare cases, sesamoiditis can be chronic in nature. In these situations, the provider may opt to administer a corticosteroid injection around the sesamoid bone to reduce pain and inflammation in the surrounding soft tissue. An additional option for patients with chronic sesamoiditis or non-healing sesamoid fractures is to remove the bone altogether. As the sesamoid bones play a role in proper foot mechanics this treatment should be avoided if possible.
Return TO PLAY
The key to optimal return to sports is regaining the strength, balance and agility that was present before the injury. Although return to play is variable depending on the severity of the injury, sesamoiditis treated non-operatively generally have an estimated return of about 2 - 4 weeks. A sesamoid fracture may have a slightly prolonged healing process in an otherwise healthy athlete at approximately 4 - 6 weeks.