Overview

Tarsal coalition refers to a condition that affects approximately 1% of the world’s population.¹ This is when connective tissues, either fibrous, cartilaginous, or calcified bone connects bones in the middle of the foot together, or otherwise at the back of the feet together so that they can’t move freely. There are 7 bones in these regions of the foot, and when they connect together they can restrict movement. Commonly, the tarsal coalitions that form are:¹

• Calcaneo-navicular coalition: abnormal fusion of the heel bone with the bone in front of it (calcaneus and navicular bone)
• Talo-calcaneal coalition: abnormal fusion of the 2 bones on top of each other, in the heel of the foot (calcaneus and talus)
• Talo-navicular coalition (rare ~10% of cases): abnormal fusion of the upper heel bone with the bone in front, at the bottom of the foot (talus and navicular bone) 

Read on to find out more about how these conditions can be diagnosed.

Symptoms of tarsal coalition

Often, this condition may not result in symptoms for several years after the abnormal fusion begins to form. Tarsal coalition is usually caused by a genetic abnormality, preventing the bones in the foot from separating completely during foetal development. However, as the individual gets older, the bones ossify, and eventually symptoms can begin to present themselves. This can affect children, teenagers, or adults. Pain is often felt in the back or middle of the foot, often below the ankle, and it can be triggered when the bones begin to stiffen. The bones stiffening is called ossification. The further this progresses, the more solid the fusion,rom fibrous tissue to the cartilage to the bone. 

Certain types of tarsal coalitions affect some age groups more than others. Those aged 8-12 often suffer from talo-calcaneus coalitions, whereas young teenagers aged 12-15 often feel the effects of talo-navicular coalitions arising.¹ 

Trauma or comorbidities can lead to symptoms arising in adults, for example, ankle sprains or arthritis affecting the joint. Flat-foot may also be a condition in some of those affected, with spasming tendons and ligament strain contributing to the pain in those affected with tarsal coalition. 

The most common symptoms of tarsal coalition include:

• Pain: in the middle or back of the foot, especially during movement
• Flat feet: when the arch of the foot is lower than normal, often stiff and unable to return to a more neutral position
• Stiffness and rigidity: restricted movement in the foot, particularly around the ankle joint
• Spasms: over time, peroneal tendon spasms may occur around the ankles, causing discomfort
• Frequent sprains: these often occur due to ligament strain and can cause difficulty walking on uneven surfaces

Despite both feet equally being likely to be affected, bipedal symptoms are present in only 50% of cases, even though one foot may have more severe symptoms. In other cases, only one foot will cause discomfort, although both feet may have malformations to some extent. 

Diagnosis of tarsal coalition

Diagnosis of tarsal coalition begins with an appropriate physical examination and complete medical history, including prenatal, birth, and family. Physical examinations may exhibit a flat foot with low, rigid arches that do not correct when the patient stands on tiptoes. Imaging studies are required if a tarsal coalition is suggested by symptoms.

X-rays

These are typically the first imaging modality used to identify the coalition. Standing X-rays allow a preliminary evaluation of the alignment and architecture of the tarsal bones. While X-rays are helpful in identifying large coalitions and obvious deformities, they sometimes fail to detect small or early coalitions. They are especially helpful in confirming the presence of a flat-foot, a common complaint of tarsal coalition. The images obtained can also help to rule out other causes of foot pain, such as fractures or misaligned joints

CT scan

Computed tomography (CT) scans provide a very high level of detail and so they are often used to confirm tarsal coalitions. They provide cross-sectional, 3D images of the tarsal foot bones and precise details about the size, shape, and location of the coalition. The high-resolution images allow the doctor to observe the way the bones are connected and if the coalition is caused by soft tissues, such as cartilage or fibrous tissue. These advantages, coupled with the few minutes it takes to get a CT scan, are all beneficial factors that can assist treatment plans, especially if surgery is indicated. However, this type of scanning should be avoided if the patient is pregnant, as the ionising rays may be harmful to the foetus 

MRI

Magnetic resonance imaging (MRI) is used to provide additional information, particularly with respect to the surrounding soft tissues. MRI scanning allows for the clear imaging of the soft tissue elements of the foot, including muscles, ligaments, and tendons. This is especially useful with suspicion of coexisting conditions like muscle spasm, nerve entrapment, or inflammation. They may also be used to assess the degree of joint degeneration, which is useful in ascertaining whether arthritis or soft tissue damage is a contributing factor in the patient's condition. This scan is non-invasive and potentially can help rule out other disorders that may cause symptoms similar to those of tarsal coalition, such as infection, tumours, or nerve involvement. However, MRIs do take a long time to form a picture, are much more costly than the other imaging techniques, and cannot be done if the patient has any metal in their body, e.g. metal rod in the knee joint. As such, the physician will take medical history into account when deciding whether an MRI is necessary. 

Both feet are generally scanned even if only one is symptomatic, since the condition would be bilateral.

Treatment options

Treatment for tarsal coalition depends on the severity of the condition and the level of discomfort experienced by the patient. While some individuals may not require treatment, others may need interventions ranging from non-surgical management to surgical procedures.

Non-operative treatment options

Before considering surgery, a range of non-surgical treatment options can be explored. These approaches focus on alleviating symptoms and managing the condition without resorting to invasive procedures. Some of the non-operative treatments include:

1. Limiting high-impact activities, such as running or jumping, can help reduce strain on the affected foot and provide relief from pain
2. Exercises that focus on stretching and strengthening the muscles in the foot and ankle can help improve flexibility and reduce discomfort
3. Changing footwear to provide better support, such as wearing an ankle boot that restricts joint movement or using shoes with rocker-bottom soles, can help manage the condition
4. Custom insoles, ankle braces, or other orthotic devices can offer additional support and stability to the foot, which can alleviate pain in some patients
5. Non-steroidal anti-inflammatory drugs (NSAIDs) can be used to reduce inflammation and relieve pain
6. In some cases, corticosteroid injections can provide powerful anti-inflammatory effects, reducing pain and swelling
7. A period of rest or immobilisation, such as wearing a cast or brace, may help reduce inflammation and ease symptoms

Surgery is also an option. In these cases, imaging scans can be very useful for assessing the entry point and course of the surgery. For example, a talo-calcanear coalition will require a different entry point to a calcaneo-navicular coalition, based on the position of the bones which require separation. 

Summary

Tarsal coalition affects approximately 1 in 100 people, causing pain and restricted movement in the foot. In 50% of cases, both feet may experience symptoms, but in most cases, one foot will experience worse symptoms than the other foot, despite both feet presenting abnormal anatomy. There are both genetic and traumatic causes for these conditions, and the cause will often depend on how the specific coalition is treated. Initial exams and X-rays can be coupled with CT scans and MRIs to inform the physician's course of treatment. Non-operative treatment methods are possible, but often these will be short-lived and symptoms may return later on. Operative treatments also exist but are coupled with their own greater risks, much like any other surgery.