Sesamoiditis

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Sesamoiditis is a common cause of pain in the forefoot. The most common symptom is pain felt under the ball of the foot, more specifically under the big toe joint or your 1st metatarsal bone. The term sesamoiditis describes any irritation or inflammation of the sesamoid bones and surrounding soft tissue. These sesamoid bones are very similar to your knee cap. They are 2 very small bones that sit in a tendon that runs under your foot all the way to your big toe.

Sesamoiditis is a common cause of pain in the forefoot. The most common symptom is pain felt under the ball of the foot, more specifically under the big toe joint or your 1st metatarsal bone. The term sesamoiditis describes any irritation or inflammation of the sesamoid bones and surrounding soft tissue. These  sesamoid bones are very similar to your knee cap. They are 2 very small bones that sit in a tendon that runs under your foot all the way to your big toe. Like the kneecap the sesamoids act like a pulley increasing the leverage of the tendons acting on the big toe. Every step you take involves bending your big toe and this requires the use of this tendon and your sesamoid bones. If repetitive damage continues and the sesamoid bone are damaged then mircoscopic tears or fractures can develop in the bone structure resulting in a stress fracture.

 

Anatomy:

The anatomy of the Hallux or big toe, consists of two toe bones or phalanges and two joints called interphalangeal joints. Two tiny, round bones called sesamoids exist just behind the base of the 1st of these joints, they help to move the big toe up and down.

The sesamoid bone located closest to the inside of the foot is called the tibial or medial sesamoid bone; the one closest to the outside of the foot is called Fibula or lateral sesamoid bone. The sesamoids help to form a joint and are held in position by the flexor hallucis brevis tendon which is one of the tendons that helps stabilise the big toe against the ground and helps propel the foot off the ground.

 

Function of the sesamoids:

One of the main functions of the sesamoid bones is to help absorb and disperse forces in the forefoot when walking. The way this is achieved is through their numerous attachments to other tendons and ligaments. Tendons of the adductor and abductor hallucis muscles, sesamophalangeal ligament, and metatarsosesamoid ligment all attach to the sesamoid bones. It is through these multiple attachment points that some of the shock and force of the foot striking the ground is dispersed.

Another primary function of the sesamoids and connecting tendons and ligaments is to act as a fulcrum or lever, enhancing the big toe mechanical advantage enabling it to push off the ground during gait.

 

Sesamoiditis is the most common term used to describe inflammation of the sesamoids, however it may fall under broader terms such as metatarsalgia or forefoot pain used to describe any general pain in the forefoot region of the body.

 

Causes

Sesamoiditis is usually caused by repetitive excessive trauma and overload of the sesamoids, tendons and other structures under the 1st metatarsal phalangeal joint or big toe joint.  Any activity that involves constant  or repetitive pressure or requires the big toe to be flexed while under load can cause sesamoiditis. It is common problem experienced by dancers, runnners and even walkers.  The way you walk and your foot structure can predispose you to sesamoiditis. People with stiff high arched feet, boney feet or flat feet can be prone to greater forces on the sesamoids.

 

Typical Signs and symptoms

The pain associated with sesamoiditis is commonly described as a mild ache which has come on gradually. In the majority of cases no one initiating event or injury can be remembered by the patient. If the aggravating activity is continued than the pain and swelling typically increase to the point that walking or weight bearing becomes painful. The area underneath the big toe joint or 1st metatarsal phalangeal joint can become swollen, however erythema or bruising is rare. Movement of the big toe joint can become limited due to swelling and often full dorsiflexion (bending up) of the toe will result in pain.

In cases where the pain has come on suddenly or an impact injury has occurred the pain can be quite intense and any weight bearing can be painful. These symptoms suggest a possible fracture to one of the sesamoids and usually require further investigation such as x-ray to confirm the diagnosis.

 

Demographics

It typically occurs in young people who are physically active or involved in sports activities running and dancing that can overload the big toe and consequently the sesamoids. It can also occur in older populations especially those who have bunions, hallux limitis or osteoarthritis of the big toe joint or 1st metatarsal phalangeal joint. If the big toe doesn't bend correctly than the sesamoids can become overloaded and inflamed.

 

Diagnostic testing

If the diagnosis of the problem is not entirely clear or there is a suspicion of a fracture further diagnostic tests may be ordered.

X-rays from several views including a special axial view are the most commonly ordered. This axial view allows a really good view of the sesamoids and shows the space between the sesamoids and the big toe bones and joints.

Normal sesamoids show up as 2 pea sized bones that sit just behind the head of the  1st Metatarsal bone. In some cases they may appear to be split into 2 or more separate bones. This is normal in about 10 percent of the population and is referred to as  bi-partitie or tri-partitie sesamoids. If the divisions between the bones look rough or uneven than this may indicate a fracture and further testing may be needed.

If a fracture is suspected and X-rays are inconclusive than a bone scan or magnetic resonance imaging (MRI) may be ordered.

 

 

Management - conservative and surgical options

In the majority of cases non-invasive conservative treatment is all that will be required. Treatment will vary between patients; however initial treatment will focus on offloading the injured area and settling pain and inflammation. This will involve resting from all activities that are likely to aggravate the problem, then offloading the area using strapping, padding  innersoles or orthotics in conjunction with careful footwear choices. To settle the pain and inflammation ice and oral anti-inflammatories can help. A soft full length functional orthotic is commonly employed to deflect pressure and tension away from the painful areas. If an underlying foot condition such as flat feet (pes planus), high arched feet (pes cavus), bunions or Hallux limitus are identified and are contributing to the sesamoiditits than a function foot orthotic becomes an essential part of the treatment plan.

Severe cases of sesamoiditis will often require a period of forced rest. This is best achieved by the use of a short leg pneumatic walker with a rocker sole for a period of between 2 and 6 weeks. Failing this steroid injections or surgery may be considered.

 

Sesamoid fractures:

Surgery:

Surgery is only considered as a last resort. If all conservative treatment has been tried and failed than a consultation with a surgeon specialising in the foot and lower limb may be required. Further tests such as X-rays, MRIs or bone scans may be ordered before the surgeon decides on a treatment plan. The exact surgical procedure with differ between patients and will depend on the severity of the case and the anatomy involved and the surgeons preference. Surgical treatment usually involves the removal of the entire sesamoid bone often referred to as a sesamoidectomy. This removal is favoured over any procedure involving planing or reshaping the sesamoid as it has been found to weaken the bone and may lead to longer healing times or fractures of the sesamoid during recovery. A more involved procedure that is sometimes used is an osteotomy of the base of the 1st Metatarsal bone. This involves cutting and elevating the head of 1st Metatarsal to elevate the plantar pressure on the sesamoids.  Recovery from any of the surgical procedures involves wearing a Pneumatic walker for a period of 6 weeks. Surgery involves cutting through the joint capsule and other soft tissue structures, consequently the supporting structures around the big toe can be weakened. This weakening of the soft tissues and removal of the sesamoids can severely alter the function of the foot which in turn can lead to dysfunction or misalignment of the forefoot.

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