When our bodies are developing cells get an assignment, some are programmed to be cartilage, some programed to be ligaments, others bone. In some cases there may be errors, joints dont develop properly and form a bridge across two separate bones which should have been separated by a joint. These are called bony coalitions and they can occur anywhere in the skeleton, we call them tarsal coalition- tarsal refers to bones of the foot.
There are two common types that we regularly treat, the subtalar coalition and the calcaneo-navicular coalition. The subtalar coalition is between two bones the talus and the calcaneus, the calcaneal- navicular is between the navicular and the calcaneus ( heel bone ).
Here is an image taken from a CT scan, on the left is a normal subtalar joint, the red arrows points to it. On the right is the same joint on the patients other foot, there is no joint separation, this is a subtalar coalition.
The calcaneo-navicular coalition is best seen on xray, look below on the left is a normal foot xray the arrow points to a normal disconnect between two bones, on the right please compare and see a bone connection.
These coalitions sometimes become obvious when the kids are in their early teens, the reason is that as the bones all harden up the coalition becomes an irritant, inflammed and painful. On occasion kids can remember a particular event like a bad ankle sprain that starts the pain. On more severe occasion patients present to us with a muscle spasm that actually flattens the foot and make it point to the outside, this is most commonly called a a peroneal spastic flatfoot here is an example photograph of a 12 year old girl with that condition, the muscles on the outside of her ankle are in spasm because on the joint pain and the foot is everted outward. Her left foot is straight, right foot in spasm.
THE TREATMENT :
In many occasions a nerve block can break one of these muscle spasms related to a tarsal coalition.In other cases where the coalition causes a flatfoot we can approach it conservatively with orthotics and physical therapy if there is not considerable pain. In other cases we serve the patient better in both the short term and the long term by performing asurgical correction of both the coalition and the flatfoot simultaneously.
In very young children generally 15 and under we can surgically remove the coalition from the joint and allow for normal functioning. In older teens and adults we generally perform a fusion surgery to remove the coalition as well as the rest of the joint. This stops any motion in that damaged joint and thus relieves the pain. A joint fusion may seen scary to most patients but in these cases the joints move so little in the first place having them fused doed not at all change the persons activity or gait walking pattern.
Of course a proper examination is needed to formulate a treatment and diagnosis plan.