Tarsal coalition is an abnormal connecting bridge of tissue between two normally-separate tarsal bones. The term 'coalition' means a coming together of two or more entities to merge into one mass. The tissue connecting the bones, often referred to as a "bar", may be composed of fibrous or osseous tissue. The two most common types of tarsal coalitions are calcaneo-

navicular The navicular bone is a small bone found in the feet of most mammals. Human anatomy The navicular bone in humans is one of the tarsal bones, found in the foot. Its name derives from the human bone's resemblance to a small boat, caused by th ...

(calcaneonavicular bar) and talo- calcaneal (talocalcaneal bar), comprising 90% of all tarsal coalitions. There are other bone coalition combinations possible, but they are very rare.Tarsal coalition and painful flatfoot, K.A. Vincent, Shriners Hospital for Children, Portland, Oregon and Department of Orthopedics, Oregon Health Sciences University, Portland, OR 97201-3905, USA Symptoms tend to occur in the same location, regardless of the location of coalition: on the

lateral Lateral is a geometric term of location which may refer to: Healthcare *Lateral (anatomy), an anatomical direction *Lateral cricoarytenoid muscle *Lateral release (surgery), a surgical procedure on the side of a kneecap Phonetics *Lateral cons ...

foot, just

anterior Standard anatomical terms of location are used to unambiguously describe the anatomy of animals, including humans. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

and below the lateral

malleolus A malleolus is the bony prominence on each side of the human ankle. Each leg is supported by two bones, the tibia on the inner side (medial) of the leg and the fibula on the outer side (lateral) of the leg. The medial malleolus is the promine ...

. This area is called the sinus tarsi.

Symptoms

The bones of children are very malleable in infancy. This will generally mean that, despite the presence of a coalition, the bones can deform enough to allow painless walking until the child's skeleton has matured enough. 'Skeletal maturing' means that bone is laid down in the tissue that forms the immature bone shape gradually until adult bone is achieved at about the age of seventeen years in the feet. Other body parts reach skeletal maturity at different times. The onset of symptoms related to a tarsal coalition usually occurs at about nine to seventeen years of age, with a peak incidence occurring at ten to fourteen years of age. Symptoms may start suddenly one day and persist, and can include pain (may be quite severe), lack of endurance for activity, fatigue, muscle spasms and cramps, an inability to rotate the foot, or

antalgic gait An antalgic gait is a gait that develops as a way to avoid pain while walking ('' antalgic'' = ''anti-'' + '' alge'', "against pain"). It is a form of gait abnormality where the stance phase of gait is abnormally shortened relative to the swing pha ...

Causes

Tarsal coalition is almost exclusively a product of an error during the dividing of embryonic cells in utero. Other causes of

synostosis Synostosis (plural: synostoses) is fusion of two or more bones. It can be normal in puberty, fusion of the epiphyseal plate to become the epiphyseal line, or abnormal. When synostosis is abnormal it is a type of dysostosis. Examples of synostoses ...

(bone fusion) could include a surgical 'screwing together' of two bones, a very advanced case of arthritis leading to self-fusion of a joint by an internal process within the body or some other very traumatic event. The birth defect responsible for tarsal coalition is thought to often be an autosomal dominant genetic condition. This means that if you have a parent with the disorder it is highly likely to be passed on to offspring.

Anatomy

Anatomically, the abnormal connecting 'bridge' is virtually all

cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck an ...

in the young child, often nearly all bone in an adult and a mixture as the skeleton

ossifies Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in t ...

in between these ages. Some fibrous tissue (like gristle) is often also involved. When the bridging link becomes bony enough, it results in a limitation of motion and this brings about the onset of pain. The bones of the tarsus are the rear most bones in the adjacent diagram: calcaneus, talus, navicular, cuboid, medial cuneiform, intermediate cuneiform and lateral cuneiform bones. These bones create the two major foot joints – the subtalar and

midtarsal joint The transverse tarsal joint or midtarsal joint or Chopart's joint is formed by the articulation of the calcaneus with the cuboid (the calcaneocuboid joint), and the articulation of the talus with the navicular (the talocalcaneonavicular joint) ...

s – that allow complex motions to occur in the feet. These motions are necessary for such activities as walking over uneven terrain and creating a gait that allows normal function of the knees, hips, back, etc.

Diagnosis

In a case of an adolescent with rear foot pain, the physical exam will reveal that the foot movement is limited. This is both because there is a physical blockade to movement and because the brain will 'turn on' the muscles around the area to stop the joint moving toward the painful 'zone'.

X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

s will usually be ordered and, in general, if there is enough toughness to the tissue bridge that pain has begun – there will usually be enough bone laid down to show up in an x-ray. More high-tech investigations such as CT scan will be required if proceeding to surgery. If the bridge appears to be mostly fibrous tissue, an

MRI Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio waves ...

would be the preferred modality to use.

Treatment

The goal of non-surgical treatment of tarsal coalition is to relieve the symptoms by reducing the movement of the affected joint. This might include

non-steroidal anti-inflammatory drug Non-steroidal anti-inflammatory drugs (NSAID) are members of a therapeutic drug class which reduces pain, decreases inflammation, decreases fever, and prevents blood clots. Side effects depend on the specific drug, its dose and duration of ...

s (NSAIDs), steroidal anti-inflammatory injection, stabilizing orthotics or immobilization via a leg cast. At times, short term immobilization followed by long term

orthotic Orthotics ( el, Ορθός, translit=ortho, lit=to straighten, to align) is a medical specialty that focuses on the design and application of orthoses, or braces. An is "an externally applied device used to influence the structural and functio ...

use may be sufficient to keep the area free of pain. Surgery is very commonly required. The type and complexity of the surgery will depend on the location of the coalition. Essentially, there are two types of surgery. Wherever possible, the bar will be removed to restore normal motion between the two bones. If this is not possible, it may be necessary to fuse the affected joints together by using screws to connect them solidly. Cutting away the coalition is more likely to succeed the younger the patient. With age comes extra wear in the affected and adjacent joints that makes treatment more difficult.

Symptoms

Causes

Anatomy

Diagnosis

Treatment

See also

References

Further reading