Brachymetatarsia is a condition in which one of the five long bones of the foot (the metatarsals) is abnormally short, resulting in a shortened toe. This condition usually occurs in both feet (i.e., bilaterally) and in the fourth toe. If it affects more than one toe, the condition is called brachymetapody.
Causes of Brachymetatarsia
In most cases, brachymetatarsia results when the metatarsal growth plate closes too early. Once the growth plate closes, the bone can no longer grow. This can be caused by a genetic factor or by trauma to the foot that results in a metatarsal growth plate fracture.
Physiology of Brachymetatarsia
A shortened toe can cause several problems. During walking, the weight normally is transferred from the fifth toe to the fourth, then to the third, and so on until it reaches the first toe (hallux). This occurs because the toes are gradually longer and as weight is transferred to the forefoot, the next longest toe assumes the weight. Brachymetatarsia disrupts this process.
If the fourth toe is shorter than the fifth toe, it never assumes the body weight and cannot transfer it to the third toe correctly. As a result, the fifth and third toes receive extra weight and pain develops in those areas. An abnormally short toe also tends to drift upward, which often causes problems with footwear.
Treatment for Brachymetatarsia
Treatment for brachymetatarsia is limited. Conservative treatment involves wearing shoes with extra depth to allow more room for the shortened toe. Padding can help protect the toe from pressure and friction from the top of the shoe, which may cause ulcerations. Orthotics may be used to relieve pressure under the other toes.
In some cases, surgery is performed to lengthen the short toe. In this procedure, the short metatarsal is usually cut and a piece of bone is grafted between the two ends. When the graft heals, the metatarsal and toe are the correct size. In most cases, the toe’s extensor tendons and the surrounding skin also must be lengthened to accommodate the repaired toe.
An exceptionally short metatarsal may make grafting impossible. In this case, the two metatarsals flanking it may be shortened slightly to correct the arc of the toes and restore the foot’s ability to transfer weight sequentially.
Following surgery, all weight must be kept off the surgically repaired foot for 3 months, after which the patient wears a snug-fitting lace-up shoe (e.g., oxford, sneaker) for about 6 weeks.
Newer treatment involves using an external device, which is attached to the metatarsal with pins, to gradually draw out the bone to the appropriate length.