ANKLE & FOOT
The 2 sesamoid bones are located under the big toe joint in the foot. Sesamoids act like pulleys that provide a smooth surface for the tendons to slide over increasing the ability of the tendons to transmit muscle forces. The sesamoids in the foot assist with weightbearing and help elevate the bones of the big toe. Like other bones, sesamoids can fracture due to an acute injury for repetitive stress.
Fractured sesamoid bones and bipartite bones are distinct conditions but can cause similar symptoms in the foot. Bipartite sesamoids are naturally divided into 2 pieces and are normal anatomical variants. Bipartite sesamoids result from an incomplete fusion of the bone during development. On an x-ray, a bipartite sesamoid will have 2 pieces that will have smooth, corticated well-defined edges and the medial (or tibial) sesamoid is often larger than the lateral (or fibular) sesamoid. Bipartite sesamoids are often present on both feet. For this reason it is recommended that the clinician orders bilateral foot films for comparison in ruling out a bipartite sesamoid versus a fractured sesamoid.
A fractured sesamoid is usually caused by trauma, such as a sudden impact, a fall or a repetitive stress. The patient will usually complain of pain under the big toe joint, swelling and difficulty bending the big toe joint and pain with weightbearing. The appearance on an x-ray will show a fracture line that is usually sharp, jagged, radiolucent and the fragments usually fit together. The components of a bipartite sesamoid usually do not fit together. Sesamoid fractures are usually unilateral on plain films. Bipartite sesamoids are usually larger in size than a single, unfractured sesamoid, while fractured sesamoids are often the same size or slightly larger than the other sesamoid on the same foot.
X-rays are the primary tools for diagnoses. Ordering bilateral foot films are also helpful to distinguish between a bipartite versus fractured sesamoids. However, bone scans or MRIs may be used to differentiate between a bipartite sesamoid versus a fractured sesamoid as well. Further differential diagnoses that should be considered when dealing with a painful big toe joint includes turf toe and sesamoiditis. Turf toe is an injury of the soft tissues surrounding the big toe joint. It usually occurs when the big toe joint is extended beyond its normal range. Turf toe causes immediate, sharp pain and swelling that usually affects the entire big toe joint and limits the motion of the toe. Turf toe may result in an injury to the soft tissue attached to the sesamoid or a fracture of the sesamoid. Sesamoiditis tends to be an overuse injury involving chronic inflammation of the sesamoid bones and the tendons involved with those bones. Sesamoiditis is often caused by increased pressure on the sesamoids. Often, sesamoiditis is associated with chronic dull pain underneath the big toe joint. The pain is transient, and usually occurs with certain activities or shoes.
Treatment is generally nonsurgical. Nonsurgical treatments include stopping the activity causing the pain. This may include a period of non-weightbearing status. Ibuprofen or aspirin may relieve some of the pain. Icing the bottom of the foot and wearing stiff soled low heeled shoes may also help. Custom orthotics with a special modifications to offload the sesamoidal apparatus are also helpful. However, if conservative treatments do not relieve symptoms, your doctor may recommend surgery to remove the sesamoid bone. Surgery may be recommended for longstanding sesamoiditis that has failed to improve with nonsurgical treatments. A sesamoid fracture that is displaced or not healing may also require surgery. Recovery from sesamoiditis or sesamoid fracture depends on the severity of the problem. Recovery may take a long time, with multiple weeks or months.
