A flatfoot is a subjective term that describes a foot with a decreased or absent arch. In the majority of flatfoot cases, the primary problem is an inherited tendency to have no arch. There's a number of biomechanical and developmental reasons why this occurs, but in most cases, the condition is benign and will never really have significant impact on that patient over the course of their lives. Occasionally though we see specific types of flatfeet that are real trouble makers. One of those conditions is called a tarsal coalition.

There are a number of specific congenital (from birth) deformities that we see that result in flatfeet. The most common of these conditions is called a tarsal coalition. Tarsal refers to the bones of the rear portion of the foot and coalition refers to a bridge. What happens in cases of tarsal coalition is that a coalition or bridge of bone forms between two bones, limiting the range of motion of the joints of the foot. The end result is a rigid, painful flatfoot. The initial diagnosis of a tarsal coalition can be difficult to make.  The challenge lies in the fact that the symptoms of a tarsal coalition don't become evident until the late teens. Part of the diagnostic challenge lies in the fact that the bridge of bone in young children is made of fibrous material and cannot be seen on x-ray. As the patient matures, the fibrous tarsal coalition begins to ossify (turn to bone). As this ossification progresses, the foot becomes markedly rigid and painful.

Tarsal coalitions can form at several different locations in the foot. The most common tarsal coalition forms between the calcaneus and navicular (shown in the x-rays on this page). The second most common tarsal coalition forms in the subtalar joint and is subsequently called a talo-calcaneal coalition. The third most common tarsal coalition forms at the talo-navicular joint. The etiology of tarsal coalitions is unclear, but most clinicians assume that the coalition forms as the result of an incomplete separation of the developing bones while in utero.

Treatment of tarsal coalitions

The initial diagnosis of a tarsal coalition is based upon clinical findings of a fixed, rigid foot. Although X-rays don't show any specific location of the early fibrous tarsal coalition, they do show early changes in the bone that are secondary to the limited range of motion. These changes include dorsal spurring of the talo-navicular joint and a halo of increased bone density surrounding the subtalar joint. This density is one of the radiographic signs of the early onset of osteoarthritis in the subtalar joint. A definitive diagnosis of a tarsal coalition can be made with an MRI.

Tarsal coalitions can be managed conservatively from the onset of symptoms until the late teens. Prescription orthotics and ankle bracing can help to relieve a bit of pain but won't help to delay formation of the tarsal coalition. The usual and customary treatment of tarsal coalitions is surgical resection of the coalition with or without fusion of the affected joint space. Generally speaking, calcaneo-navicular (C-N) coalition resections are quite successful. Resection of a C-N coalition would typically be performed with an interposition of soft tissue or muscle to inhibit regrowth of the coalition. Talo-calcaneo coalition resections are not quite as successful as an isolated procedure and are often performed in conjunction with a fusion of the joint between the talus and calcaneus (subtalar joint). The determination of whether fusion is indicated is often dictated by the amount of degenerative change of the subtalar joint seen during the surgery.

When should a tarsal coalition be corrected? From one perspective, the earlier the better is true. If a tarsal coalition is allowed to remain unaddressed, the foot will become rigid and progressively undergo adaptive change during the second and third decades of the patient's life. These changes will become fixed and can only be repaired with a salvage fusion procedure called a triple arthrodesis. But it's also important to allow for skeletal maturity. Most children reach skeletal maturity between the ages of 16 and 19 years old. Therefore, the best time for correction of a tarsal coalition is after the child reaches skeletal maturity.

Abduction (abducto) - a motion of the forefoot out and away from the mid-line of the body.

Pes - Latin, referring to foot.

Planus - Latin, referring to flat.

PTTD - posterior tibial tendon dysfunction .

Tarsal coalition - a bridge of bone that inhibits normal bone growth in the foot and contributes to a flatfoot.

Valgus - a motion of the foot out and away from the mid line of the body.

No information is available for this topic.

Patients with tarsal coalitions begin to have symptoms in their early teens.  As the fibrous bar that initially forms the coalition begins to calcify, the foot begins to stiffen.  Examination of patient's with tarsal coalitions is striking in that the foot is rigid.  Attempts to move the foot produce pain.  Most children with tarsal coalitions are unable to participate in sports due to pain.

The differential diagnosis for a tarsal coalition should include;

Flatfoot

PTTD (posterior tibial tendon dysfunction)

• Ankle Sprain

• Posterior Tibial Tendon Dysfunction

• Sinus Tarsi Syndrome

• Arch Pain

• Ankle Pain

This article was written by Jeffrey A. Oster, DPM and last updated 4/28/10. No additional information is available for this topic.