The big-toe sesamoids are two small bones, each roughly a centimetre in size, beneath the head of the first metatarsal. They support the proper function of the big-toe flexor tendons and distribute forces beneath its metatarsophalangeal joint during walking, running and jumping.

Sesamoid disorders

  • sesamoid inflammation
  • sesamoid fracture: acute fracture or stress fracture
  • avascular necrosis of a sesamoid (AVN)
  • “turf toe” injury

Symptoms of sesamoid conditions

  • all sesamoid conditions cause pain beneath the sesamoid that increases during standing and at push-off when walking or running, as the big toe bends upwards under body weight
  • swelling
  • sometimes dorsal subluxation of the big toe, which is raised above the ground when standing

Causes of sesamoid conditions

Sesamoid inflammation most often results from cumulative overload. Repeated microtrauma, particularly in dancers and runners, may contribute. Overload can also arise from unsuitable footwear, a congenital high-arched foot or excessive activity of the peroneus longus muscle. Acute fractures follow trauma, most often jumping from a height, suddenly starting to run or accelerating quickly towards a ball.

Stress fractures have the same causes as sesamoid inflammation.

No single cause of sesamoid avascular necrosis has been identified. Previous injuries, overload, microthrombi, hormonal fluctuations, smoking and other factors are suspected. Turf toe involves injury to soft tissues around the sesamoids, an avulsion fracture at the base of the big-toe phalanx or disruption of a bipartite sesamoid. These injuries most often occur during a sudden push-off from the big toe, such as jumping or accelerating towards a ball.

Diagnosis of sesamoid conditions

  • weight-bearing X-rays
  • standing CT scan
  • pedobarography

In some cases, also:

  • magnetic resonance imaging
  • SPECT-CT

Treatment of sesamoid conditions

Non-surgical treatment: most sesamoid disorders and injuries are initially treated without surgery. Treatment includes reducing weight-bearing on the affected limb, immobilising it in an orthopaedic boot or brace, as for an acute fracture, and taping the big toe in a position that relieves the affected area. Anti-inflammatory medicines and rehabilitation treatments can help. When patients return to their own shoes, special insoles reduce pressure on the sesamoids. For sesamoid inflammation, an intra-articular steroid injection may also be used.

For avascular necrosis of a sesamoid, a percutaneous platelet-rich plasma injection may be used.

Surgical treatment

If conservative treatment is unsuccessful, surgical options include:

  • fixation of a sesamoid fracture using bone grafts
  • for avascular necrosis, percutaneous drilling of the affected sesamoid combined with platelet-rich plasma or concentrated bone marrow cells
  • sesamoidectomy: partial or complete removal of the diseased sesamoid in advanced avascular necrosis
  • correction of a high-arched foot
  • transfer of the peroneus longus tendon to the peroneus brevis tendon when the peroneus longus is overactive