Introduction 

Tarsal coalition is when two or more tarsal bones, which are located in the back of the foot and heel, link in a way they shouldn't, causing less motion and more pain. It often starts when a baby grows in the womb, with some children being born with tarsal coalition, whilst others only develop symptoms later in their adolescence.¹

There are three kinds of coalitions, based on what type of tissue links the bones together: fibrous, cartilage, or bone. Knowing the difference between these types of tarsal coalition is necessary for a medical professional to organise the most suitable treatment plan. While some people might not feel it, others get stiff feet, pain, and hurt their ankles repetitively. In some cases, ankle sprains and malformations of the bones also occur.³ The treatment options vary depending on the severity, from non-operative treatments such as arch supports and non-inflammatory drugs used for 4-6 months, to more invasive treatments like surgical procedures (resection of the coalition).³ This article will differentiate between fibrous, cartilaginous, and bony tarsal coalitions, highlighting the effects of each in the clinic. 

Anatomy of the foot and tarsal bones 

The foot is made of many bones that help with steadiness and movement. The tarsal bones make up the back and middle of the foot and are key in holding weight, posture, and gait. There are seven tarsal bones that join together through soft tissue attachment, intertarsal ligaments, collateral ligaments, plantar tarsal ligaments, and fibrous joint capsule. The main tarsal bones are the talus, which joins the foot to the lower leg, and the calcaneus, or heel bone, which takes in shock and helps push when walking. The navicular bone is in front of the talus and helps keep the arch steady. The cuboid and three cuneiform bones, medial, intermediate, and lateral, keep the foot's shape and bend.⁵

These bones collectively move in ways that let us keep our balance, provide mechanical support, and allow for weight bearing to occur during physical activity and walking. The joint called the subtalar, set between the talus and calcaneus bones, lets the foot roll in and out.⁶ The talonavicular and calcaneocuboid joints help the midfoot bend, while the tarsometatarsal joints link the tarsal bones to the metatarsals, making it easier to move and adjust when walking or running.⁶ At times, an odd mix of foot bones, called a tarsal coalition, may take place. This issue develops sometimes from birth, but predominantly affects adolescents, often affecting parts of the foot like the calcaneonavicular and talocalcaneal spots, causing less movement, stiffness, and pain.⁶

Types of Tarsal Coalition 

When two or more tarsal bones are connected by fibrous tissue without actual bone fusion, Fibrous Tarsal Coalition occurs. Incomplete separation of bones during fetal development allows this form of coalition to form, which creates a bridge made of soft tissues connecting the bones involved. It is a “fibrous” coalition since it retains some motion, though it could still cause limited mobility and discomfort.⁷ Foot pain is a common complaint among those with fibrous coalitions (especially in adolescence when a soft tissue bridge tends to be less pliable).⁷ Foot motion in a range of motion-related activities may be met with resistance due to stiffness.⁷ Degenerative changes and subsequent inflammation of the normal adjacent tissue are possible over time through the abnormal connection.⁷

Diagnosis typically involves X-rays, but fibrous coalitions might not be so easily apparent in plane radiographs, often necessitating MRI or CT scanning for confirmation.⁷ Treatment is usually conservative, consisting of the following: immobilisation of the ongoing fracture with cast bracing, physical therapy, anti-inflammatory pain medication, and orthotics to relieve symptoms.⁷ Severe cases may need surgical intervention to restore the joint to normal function.

The tarsal coalition is caused by cobunition when two or more tarsal bones connect with cartage instead of ciliary. This appearance is due to the failure of bony development to be initiated during the embryonic period, resulting in a flexible, abnormal joint.⁸ The areas most commonly affected by coalition include the talocalcaneal and calcaneonavicular joints.⁸ Tarsal coalitions are conditions in which bone growth occurs between tarsal bones, usually causing fusion of the bones by cartilage, fibrous tissue, or fibrocartilage.⁸ Symptoms typically occur during adolescence when the cartilage begins to thicken and stiffen, decreasing joint mobility.⁸ In some cases, it can lead to malalignment that alters the way someone walks, putting additional stress on the surrounding joints and potentially causing secondary conditions.⁸

These bone proximities are often undetectable on our current X-ray units, so various imaging techniques such as MRI or CT may be required⁸. Depending on the resiliency of the cartilage resection, orthotics and anti-inflammatory medications can be used. If severe symptoms persist despite conservative treatments, surgical intervention may be indicated. 

The most severe type of tarsal coalition is when two or more tarsal bones are directly fused with bone, also known as a bony tarsal. The structure of the joint in this case does not allow movement, and functionally stiffens the joint. Bones in the sinus tarsi connect with the talus and calcaneus bones of the foot.⁹ Bony coalitions are located in important areas of the foot that support the main function of the foot, such as walking, running.⁹ For this reason, they must be only removed when the symptoms are severe and there is no other alternative treatment to a surgical approach.⁹ As a result of their bones fusing completely, patients with bony coalitions experience a considerable amount of pain, stiffness, and difficulty in using the joint.⁹ Symptoms usually get worse with physical activity, making it difficult to walk and requiring more effort from surrounding joints.⁹ This can also lead to secondary arthritis and continuing loss of motion as time goes on.⁹

Imaging tests like x-rays confirm the diagnosis, usually showing substantial bony fusion.⁹ CT scans show a clearer, full view of how much the bones have joined, while MRI helps check on the nearby soft areas.⁹ For these bone links, the fix often means surgery. Based on the severity, surgery might take out the fused bones to bring back some movement, or do a joint fusion to make the foot steady.⁹ When the joint is badly worn out, more complex surgery like joint replacement might need to happen to ease pain and help with improving movement.⁹

Treatment options for Tarsal Coalition

Tarsal coalition is taken care of with easy fixes and, if needed, by surgery. At first, the focus is on easing pain and making it easy to move by resting, taking meds for pain and inflammation of the joint, like NSAIDs, and using made-to-fit shoes to help the foot. Doing regular exercises helps make nearby muscles strong and makes it easy to bend, while putting on a cast or boot might be needed in some cases.¹⁰ When simple steps don't work, surgery may be required, most of all for bone links that severely limit movement. Surgery is usually performed under anesthesia and varies according to the type of coalition. Surgeries may involve resection, 3D reconstruction, and realignment, with the recovery rate being high.¹⁰

Summary

There are three types of tarsal bonds: fibrous, cartilage-like, or with bone. Each of these can influence foot function. The early identification of these joints and their problems is crucial to avoid pain, stiff feet, and other related foot complications. It is very important to know what kind of tarsal coalition is in the foot. This way, the most appropriate treatment method could be selected. Physicians need to watch for them in patients with either acute or chronic foot pain, ensuring the diagnosis is made properly using advanced imaging techniques. If found soon, the outcome of non-resolvable rigid flatfoot can be initially managed with pain relief and functional improvement in the short-term, ultimately preventing the development of long-term complications of the foot. Furthermore, it will provide necessary data for examples with patient-centric approaches in care.