A Tarsal coalition refers to an abnormal union between two tarsal bones. The tarsal bones are seven small bones that form the hind part of the foot. Normally these bones are connected to each other through a specific type of joint called the synovial joint. Synovial joints allow a greater amount of movement between the articulating bones, as compared to other types of joints.
In tarsal coalition, instead of the normal synovial joint the fused bones have either a fibrous, a cartilaginous or a bony connection, or a combination of all these. This abnormal union may only involve a part of the joint or may replace the whole joint, and in about 50% of cases both feet are involved.
In about 90% of cases, the coalition is either:
– between the heel bone (calcaneus) and the anklebone (talus) called Talo-calcaneal coalition
– or between the heel bone and the navicular bone (located right next to the ankle) called the Calcaneo-navicular coalition
Other tarsal coalitions are quite rare.
Tarsal coalition is a rare problem. It can either be:
– Congenital: meaning that the problem arises during fetal life and a person is born with the defect. This is the most common cause of tarsal coalition; in about 1% of population, the problem is present at birth, though symptoms don’t usually appear until adolescence or later.
– Acquired later in life as a result of trauma, infection, a joint disorder or surgery that results in abnormal union between the bones.
– Genetics are also considered to play a role in tarsal coalitions, as many patients have a positive family history of the condition.
Tarsal coalitions restrict the normal movement at the joint, making the foot less flexible and imposing undue stress on the local and neighboring joints. These coalitions become more rigid and bony with age, therefore symptoms usually appear in the second decade of life as the bone formation completes.
– Pain is the most common complaint, which mostly occurs around the outer or front side of the ankle or at the back of the foot
– Pain intensifies with vigorous or weight-bearing activities
– Spasms of the muscles on the outer side of the lower leg (peroneal muscles)
– The affected foot is often flat
– Stiffness of the foot and ankle, Talo-calcaneal coalitions restrict the movements most.
An injury or sprain can transform a non-painful tarsal coalition into a painful one.
Coalitions may lead to arthritis or joint disease later in age.
The diagnosis is usually based on the symptoms and physical examinations. X-rays are also helpful in diagnosing the condition; however, CT scans and MRI are more confirmatory.
The initial treatment consists of resolving the symptoms by:
– immobilizing the foot in a rigid cast or boot and using crutches to avoid weight
– using pain killers or anesthetic injections to control pain
– insole devices help to disperse the weight and decrease the stress at the location
– physiotherapy such as massage, ultrasound therapy and specific exercises may help to reduce stiffness in the foot.
The above-mentioned treatment does not resolve the cause of the problem; however, in many cases it does alleviate the symptoms successfully. If the symptoms persist, surgery is required.
Surgical treatment of tarsal coalition involves:
Excising the abnormal union between the bones:
This is the treatment of choice in children and young adults. The abnormal cartilaginous or bony coalition is excised and the empty space between the two bones is filled with either muscle or fat tissue to prevent the reformation of bone tissue in the gap. This allows restoration of normal movement between the two bones.
Fusing the bones completely:
In cases when the affected joint is extensively worn down, it is unlikely that normal movement could be restored. In such cases, the best option is to remove the cartilage covering the joint surfaces of the bones, which then unite as they heal.