Sesamoid injuries

What is it?

Anatomically, a sesamoid bone is a bone located in a muscle or tendon. Its etymology comes from the Latin “sesamum”, which means sesame, given their resemblance to a sesame seed.

They are located in several areas of the human body such as the patella (kneecap) or the thumb in the hand.

In the foot, this type of injury is encountered in many forms, but generally speaking it refers to the two small bones beneath the first metatarsal head, which are defined as “sesamoid”.

Fig. 1

Sesamoid bone located under the head of the first metatarsal.

They have several functions in the foot:

– Shock absorption
– Role in supporting the body’s weight
– Act as a pulley

Shock absorption and their role in bearing the body’s weight largely explain the susceptibility of these structures to direct or chronic trauma. However, their pulley function increases the effect of the various flexor muscles on which they depend and for which they are used as insertions.

There are several types of sesamoid injuries, which generally differ by their occurrence or radiological images. The main injuries are:

Sesamoiditis (30%)

Inflammatory damage generally caused by chronic overload.

Stress fracture/fatigue (40%)

It typically appears following prolonged activity (running, marathon, etc.) or with the development of chronic sesamoiditis.

Acute fracture (10%)

As a result of axial trauma, for example (a fall, etc.).

Arthritis (<10%)

Often associated with hallux valgus or diffuse arthritis of the big toe.

Clinical presentation

Whether chronic or acute, sesamoid injuries always present as a pain under the big toe next to the affected sesamoid. Mobilising the toe can increase the pain. Finally, the presence of thickened skin at the lesion (= hyperkeratosis) is usually an indication of a chronic process.

Sport is often a source of significant pain, especially when running or doing endurance sports. It is worth highlighting the situations that trigger pain and the aggravating factors.

The clinical assessment is always accompanied by radiological images in order to highlight, for example, a fracture. The tests are often accompanied by a scan or an MRI to clarify any uncertainties. They can also be used to diagnose the viability of a sesamoid bone after a fracture.

When should you consult a specialist?

When chronic pain or traumatic pain presents under the big toe, it is advisable to consult a doctor to avoid the development of a chronic condition or a worsening of the injury.

Non-surgical treatment

The first step to take is to change the footwear. Plantar support plays a major role in the treatment by offering a partial unloading of the sesamoid affected. It is important to relieve the injured structure to give it a chance to recover spontaneously.

The use of walking sticks and partial weight-bearing is often recommended for the same reason. The non-weight-bearing period can last for 4 to 6 weeks.

Anti-inflammatory drugs can provide temporary pain relief.

Finally, a far-reaching change to sporting activities should be discussed. In fact, any treatment, whether conservative or surgical, requires rest and a reduction or stoppage of sporting activities.
Surgical treatment

Non-surgical treatment is the primary therapy used to treat sesamoid injuries. However, after several months of progression without improvement, surgery may be considered.

Not many options are available. The classic technique is in the simple excision of the sesamoid affected. It is usually sufficient to treat the pain as it has no major impact on the functioning of the foot. However, the removal of both sesamoid bones often results in major functional disorders and should not be proposed, with some exceptions.

Other little documented and sometimes experimental techniques, such as arthroscopic or percutaneous drilling, are sometimes proposed. However, they must be used with care. More experience and further studies are required to validate their benefits.

Surgical fixation by screws has been described but the results are no more successful than simple excision, and it may be technically difficult to perform. For this reason, it is rarely suggested.
Post-surgical follow up

The post-surgical sequelae differ depending on the surgery performed. For simple excisions, weight-bearing walking is permitted depending on the pain after a few weeks, with the foot protected by an orthopaedic shoe.

The foot requires protection for much longer if fixation has been used.

The time off work will range from 2 to 12 weeks, depending on the profession (sedentary or more active job, whether standing up or not, etc.).

In terms of sport, swimming or riding a bike can resume after 6 weeks; running or contact sports will require up to around 3 months. Such activities can resume much earlier when the patient has shown good progress.
Risks and complications
The risks mainly relate to the anatomy of the sesamoid. In fact, they receive a low vascularisation and can easily become necrotic (die) after injury, reacting badly to trauma. This complication is particularly true after a conservative treatment or fixation.

Besides the possible complications after any type of surgery (thrombosis, infection <1%, algodystrophy <1%), it is recognised that the removal involves the following risks and complications:
- hallux valgus or post-surgical varus (rare)
- overload of healthy sesamoid
- stiffness of the big toe (rare)
- persistent pain (rare)

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Sesamoid injuries

What is it?

Clinical presentation

When should you consult a specialist?

Non-surgical treatment

Surgical treatment

Post-surgical follow up

Risks and complications

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