Sesamoiditis is an inflammatory condition of the sesamoid bones which are located on the plantar (bottom) aspect of the first metatarsal phalangeal joint (1st MPJ or big toe joint).

Treatment of Sesamoiditis

Conservative treatment of sesamoiditis consists of limiting activities and padding or 'off loading' of the joint. Off loading refers to taking the weight bearing load off of a particular area by use of a pad. In the case of sesamoiditis, the pad should be approximately 1/4" thick with a cut out for the bottom of the 1st MPJ. Should padding help, a prescription orthotic with a similar pad would be helpful.

Surgical treatment of sesamoiditis usually consists of removal of the entire sesamoid bone. Occasionally planing of the bone, or removing the bottom half of the bone may be a useful surgical procedure. Planing is used less often than total excision due to the fact that planing will weaken the sesamoid and lead to fractures of the sesamoid.

Removal of the tibial or fibular sesamoids does not typically effect the normal function of the joint. If a patient has a family history of bunions or currently has a bunion, there will be a tendency to increase the rate that a bunion will form with isolated removal of the tibial sesamoid. By removing the tibial sesamoid, the pull of the FHB muscle will become slightly more powerful through the remaining fibular sesamoid. As a result, this may accelerate the formation of a bunion. If there is no history of bunions in the family, this may not even become a factor in choosing to excise the tibial sesamoid.

Nomenclature:

First metatarsal phalangeal joint - the big toe joint. Often referred to as the 1st MPJ.

itis - used as a suffix and refers to any structure that is inflamed.

plantarflex - to move down toward the plantar surface (or floor).

Sesamoid is derived from Greek and refers to a sesame seed. The Greeks apparently related the shape of the sesamoid bone to a sesame seed.

Anatomy:

The two sesamoid bones are located on the bottom surface of the first metatarsal phalangeal joint. The sesamoids are actually a working part of the 1st MPJ and articulate with the plantar surface of the first metatarsal. The sesamoid bones are an extension of the flexor hallucis brevis (FHB) muscle and give the FHB a greater range of motion and improved lever action at the level of the 1st MPJ.

Sesamoid bones are referred to by their location and are called the tibial sesamoid (medial) and the fibular sesamoid (lateral). Tibial and fibular make reference to the bones of the lower leg.

Sesamoid bones are most common to the 1st MPJ but may also be found at other tendon/joint surfaces where a tendon changes direction. Although they're found with much less frequency, other locations include the lesser MPJ's and even the metacarpal phalangeal joint (the thumb).

Biomechanics:

The flexor hallucis brevis muscle (FHB) originates on the plantar surface of the calcaneus (heel bone). When the FHB fires, its' function is to plantarflex the great toe. The primary function of the FHB is to aid in balance and assist the calf with the toe off portion of gait. As the FHB fires, the load generated by the body of the muscle is sent through the sesamoid to an extension of the FHB that attaches to the plantar aspect of the great toe. The net result is that the great toe plantarflexes using the sesamoid bones to glide around the plantar surface of the 1st MPJ.

Symptoms:

The onset of sesamoiditis may be insidious or abrupt. An insidious onset would suggest an inflammatory condition of the joint between the articular surface of the sesamoid and the articular surface of the 1st metatarsal. An abrupt onset would suggest a fracture of the sesamoid. Regardless of onset, pain is typical specific to the bottom of the 1st MPJ. Occasionally the entire 1st MPJ may swell and become stiff. Pain is aggravated by long periods of standing, squatting and the use of higher heeled shoes.

X-ray findings in cases of sesamoiditis usually show an increased density of the affected sesamoid bone. When viewing an AP x-ray, the appearance of the bone would light up brighter indicating increased density of the bone consistent with inflammation.

Differential Diagnosis:

Arthritis

Bunion

Fractured sesamoid

Gout and pseudogout

Hallux limitus and hallux rigidus

Infection of the joint (septic joint)