Common Pedal Coalitions

A coalition refers to the union of two parts that are not normally united.  In the foot, this refers to the union of two bones where there is usually either a joint or a space between the bones.  Coalitions can theoretically be seen between any two adjacent bones, but are more common in some areas of the foot than in others. 

There are three types of coalition that are described.  These include cartilaginous coalitions, fibrous coalitions, and true osseous coalitions.  Osseous coalitions will completely eliminate movement between the two bones, while fibrous and cartilaginous coalitions will limit the motions. 

Coalitions are thought to form from the failure of the mesenchyme, the tissue that dictates bone structure in the developing fetus, to differentiate.  The mesenchyme will normally differentiate into two distinct bones.  In the presence of coalition, this does not happen.

The most common pedal coalition is seen between the distal and intermediate phalanges of the toes, most frequently in the fifth toe.  This coalition is typically of little consequence, and is rarely symptomatic.  It is present in almost half of the population, with many suggesting that this is actually and anatomic variant rather than a pathological abnormality. 

Pathological coalitions are described as incorporating the bones of the rearfoot, or the major tarsal bones.  The rearfoot complex dictates movement of the entire foot, and a limitation of movement in these joints can cause significant pain and deformity.  The most common types of tarsal coalition are between the talus and calcaneus (talocalcaneal coaltion), between the calcaneus and the navicular (calcaneonavicular coalition), and between the talus and the navicular (talonavicular coalition).  Of these three, talocalcaneal and calcaneonavicular coalitions are by far the most common.

These tarsal coalitions often present with the triad of a rigid flatfoot deformity, spasm of the peroneal muscles, and pain.  The treatment of tarsal coalition centers around reducing the pain associated with the deformity, and begins with conservative treatment such as immobilization, orthotics, shoe modifications, and corticosteroid injections locally into the area of pain. 

Surgery is often indicated in theses cases, as conservative treatment can be very limited in its effectiveness and recurrence of pain is likely.  Depending on the extent of the coalition and which joint is involved, various procedures focus on either the resection of the coalition or complete fusion of the joints involved.  Resection serves to increase motion at the joint, which would restore function and eliminate pain.  A fusion of the joint limits the motion completely, which would eliminate pain but would not restore function of the joint. 

The diagnosis of tarsal coalition is often aided with the use of CT scanning or MRI.  These advanced imaging modalities aid the surgeon in planning the appropriate treatment, and can evaluate the extent of the coalition.  They can also be used to uncover a coalition that can not be seen on x-ray.

Central Florida Foot and Ankle Center 

101 6th St Nw Winter Haven, Fl 33881 

Phone: (863) 299-4551 

www.FLFootandAnkle.com