This condition is an abnormal fusion of two bones located in the tarsal area of the foot. This tarsal area of the foot is also known as the hindfoot (rearfoot).
The red circle in the accompanying diagram represents the tarsal area. This area encompasses the talus, calcaneus, navicular and cuboid bones. The fusion is most common between the calcaneus-navicular bones and the talus-calcaneal bones. There are three types of fusions. The first is a bony fusion which is bone to bone fusion and tends to be the most rigid type of fusion. Next is a cartilage to cartilage fusion and last is a fusion of two bones through a fibrous union which is similar to scar tissue. These fusions either restrict or completely eliminate normal joint motion which generally forces the foot into a rigid flatfoot. This fusion of bone will ultimately adversely affect adjacent joints eventually leading to arthritis of those joints.
Most midfoot coalitions are of a congenital nature they can also be acquired by degenerative, inflammatory or infectious disease of the tarsal joint. Since the majority of these coalitions are of a congenital origin most people who have this condition are born with it, however, symptoms generally do not occur until the bones begin to mature generally around the ages of 9-16.
In order to limit pain the body will compensate by creating a muscle spasm of the peroneal muscles to limit motion of the hindfoot. The patient will tend to walk with the affected foot pointing outwards.
Diagnosis is generally made through clinical examination but is confirmed through x-rays, CT scans, or MRI (as shown in these two pictures). The first, on the left, is a calcaneal-navicular coalition, the second is a talo-calcaneal coalition).
The goal of conservative treatment is to relieve the symptoms and reduce motion at the fused joint.
Although symptoms may resolve with conservative care, there is always a chance of recurrence. When conservative care fails to alleviate the pain or the relief is only short lived then surgical intervention is warranted. Things that must be considered prior to surgery are the patient’s age, activity level, size of the coalition and adjacent pathology. The two types of surgery that are performed for tarsal coalition are resection, where the fused bone is removed in an effort to regain some kind of motion. The other type of surgery is arthrodesis where the coalition is actually further fused in an effort to reduce pain. The two procedures do sound contradictory but the choice of procedure is predicated on what the exact cause and type of coalition the patient presents with.
Generally, in younger individuals where there is no other adjacent pathology, resection of the tarsal coalition is the treatment of choice. This type of procedure attempts to restore some sort of motion within the joint. The problem here is that if the procedure fails then the patient is looking at a fusion which becomes more difficult when bone has already been removed.
In older individuals where there is associated pathology like arthritis and in those individuals who have had failed resections, arthrodesis or fusion of the two opposed bones is the only option.
If you are reading this section and are a candidate for tarsal coalition resection it is very important that you talk with your surgeon because additional surgical intervention is a possibility. The more severe your tarsal coalition, the greater the chance of additional surgery.