Sesamoiditis
Background
Everyone is born with two sesamoid bones in the foot. The sesamoid bones normally lie under the 1st metatarsal head, on the big toe side of the ball of the foot.
Normally, the sesamoid bones cause no problem and are a helpful part of big toe function. They are analogous to the knee cap (patella), in that they lie within a tendon (the flexor hallicus brevis tendon, in this case). Their purpose is similar to that of a pulley, redirecting the trajectory of the tendon and in doing so improving the tendon’s line of pull.
There are two sesamoid bones: medial and lateral. Their function is similar.
The sesamoids can become diseased in several ways:
Fracture of the sesamoid: Patients who sustain trauma to the foot, often athletes, can fracture one of their sesamoid bones. Often this occurs when the big toe is pushing off from the ground but experiences a greater force than usual, perhaps because the patient was simultaneously cutting or redirecting their momentum, because of an impact with another player, or because of some other unexpected event. In either case, the sesamoid splits into two or more fragments. Fractures can either be nondisplaced, where the fragments don’t pull very far apart, or they can be displaced, where a gap develops between them.
Avascular necrosis of the sesamoid: The sesamoid bones have a tenuous blood supply due to their position within the relatively avascular flexor hallicus brevis tendons. If the tenuous blood supply becomes further compromised, the bone cells within the sesamoid can starve from lack of oxygen. When this occurs, the bone actually begins to die and a relatively predictable process called avascular necrosis ensues.
Symptomatic bipartite sesamoid: Sometimes people are born with a sesamoid that has a split down the middle naturally. This can be mistaken for a fresh fracture by untrained eyes. This split is usually filled with fibrous scar tissue that is strong, and consequently, the split is asymptomatic for much of a patient’s life. However, the fibrous scar tissue can begin to break down and become inflamed, causing pain with weight bearing.
Ultimately, all three of these pathologic processes can cause sesamoid inflammation, also known as “sesamoiditis,” which is extraordinarily painful and debilitating for patients. In the normal foot, both sesamoids are an important part of the weight bearing surface — that is, we walk right on the sesamoid bones. Hence, an inflamed, fractured, or avascular sesamoid hurts when you put weight on it. Additionally, the sesamoid bone experiences stress when the big toe is in dorsiflexion (aka extension). Hence, an inflamed, fractured, or avascular sesamoid also hurts during the toe-off phase of gait, right before your foot leaves the ground.
Diagnosis
MRI showing medial sesamoidits (inflamed medial sesamoid)
The first step Dr. Bohl will take when you arrive at the office is to obtain weight-bearing x-rays of your foot and ankle. This will provide critical information about the overall alignment of your foot. It will also provide a view of the bony structure of your sesamoid bones and big toe joints. Even if you have had x-rays performed elsewhere, Dr. Bohl will likely want to repeat them in a specific manner to obtain the best understanding of your foot and ankle mechanics.
After your x-rays are obtained, Dr. Bohl will examine your foot in the clinic. He will go over the x-rays with you on the screen. Many sesamoid conditions can be diagnosed with simple clinical examination and x-ray. Nonsurgical treatment can often be initiated with just these two tools.
If nonsurgical treatment doesn’t work or is insufficient, or if the diagnosis is unclear, Dr. Bohl will recommend an MRI of your foot. This will help to clarify the pathologic process occurring in the sesamoid bone, to rule out other potentially associated conditions, and to direct any additional nonsurgical or surgical recommendations.
Nonsurgical Treatment
The symptoms from sesamoid pathology result from two distinct forces, so nonsurgical treatment is entirely directed upon reducing these forces.
The first force is stretching of the flexor hallicus brevis tendon, in which the sesamoid bones lie. When the flexor hallicus brevis tendon is stretched, the sesamoid is stretched and causes pain. To reduce stretch on the flexor hallicus brevis tendon, we need to reduce dorsiflexion (aka extension) of the big toe at the first metatarsophalangeal joint. That is, we don’t want the big toe to get pushed up as much towards the end of your step, right before the big toe leaves the ground. The way to accomplish this is to wear shoes with a stiff sole, such that your toe doesn’t get bent up. This means minimizing barefoot ambulation and minimizing flip flops or unsupportive flats. Another way to accomplish this is to insert a carbon fiber foot plate orthotic under the cushioned orthotic in your shoe.
The second force is weight bearing directly on the sesamoid bone. When you put weight over towards the big toe side of your foot, the sesamoid bone gets pinched between the hard floor and your first metatarsal. This is painful if your sesamoid is inflamed. The best way to reduce this pressure is to pad the inside of your shoe with a soft, full length, well cushioned over-the-counter orthotic. A silicone orthotic may work best. Such an orthotic can actually be placed over the carbon fiber orthotic mentioned in the paragraph above for an optimal combination to manage sesamoiditis.
Non-steroidal anti-inflammatory medications and Voltaren gel can also help.
Dr. Bohl recommends against injections of steroid for sesamoid disease because of the damage it can cause to the important tissues on the bottom of your foot, including the flexor hallicus longus, flexor hallicus brevis, plantar plate, and fat pad.
Surgical Treatment
Fortunately, surgery for sesamoid disease is one of the most effective procedures an orthopaedic foot and ankle surgeon performs. Typically, only one of the two sesamoid bones is diseased. In almost all cases, the surgical solution is simple removal of the diseased bone (medial or lateral sesamoidectomy). This relieves the stress on the bone from the flexor hallicus brevis, and it relieves the pressure on the bone from weight bearing. Repair of the soft tissues after removal of the sesamoid bone is critical to preventing complications from the procedures. And studies indicate that as long as these tissues are repaired well, you really only need one of your two sesamoid bones. So it is critical to ask your surgeon about the repair to the tissues that he or she does after the sesamoid bone is removed. This repair is the most important part of the procedure.
Both the medial and the lateral sesamoid bones can be removed. Dr. Bohl removes the medial sesamoid bone through a single small incision on the medial (inside) border of the foot. This is a highly cosmetic incision that is typically out of sight. Dr. Bohl removes the lateral sesamoid bone through a single small incision on the plantar (underside) surface of the foot. Most patients don’t mind this scar at all, because it heals well and faces the ground. The soft tissue defect is then meticulously repaired using a tiny but strong non-absorbable suture.
Immediately after sesamoidectomy, patients are placed in a lightweight dressing and an orthopaedic shoe. Recovery is generally pretty easey, as you are allowed to put weight on your foot, as long as you are wearing the orthopaedic shoe. The purpose of the orthopaedic shoe is to protect the soft tissue repair where the sesamoid bone used to be. Dr. Bohl will ask you to continue wearing the shoe for 4-6 weeks, after which you can begin to ease back into your normal activities.
In rare circumstances of recent fracture or injury to the flexor hallicus brevis, repair of the sesamoid may be superior to removal. If repair is an option, Dr. Bohl will present this to you.
Revision Procedures
The most common reason that Dr. Bohl see’s patients from other hospitals needing additional surgery after sesamoidectomy is insufficient soft tissue repair. When soft tissue repair is inadequate, the big toe can drift away from the excised sesamoid bone, causing (1) a bunion, (2) a gap between the first and second toe, or (3) a “cock-up” or “floating” toe that doesn’t stay down.
Fortunately, Dr. Bohl is experienced in recognizing and managing this complication. There are two different ways to manage it. The first involves reconstruction of the soft tissues using tendon transfers, ligament reconstructions, suture anchors, and temporary pinning of the toe. The second involves fusion of the first metatarsophalangeal joint.
If you have had a sesamoidectomy and your big toe has begun drift to medial, lateral, or upwards—or if you have persistent pain after sesamoidectomy—Dr. Bohl will be happy to discuss the risks and benifits of additional surgical or nonsugical management.