Bilateral brachymetapody

CLINICAL HISTORY

A 41-year-old woman presented with a known history of bilateral foot deformities and new complaints of bilateral foot pain.

FINDINGS

Anteroposterior (Figures 1 and 2) and lateral (Figures 3 and 4) plain films of the patient's feet demonstrate bilateral shortening of the third and fourth metatarsals with associated shortening of the distal phalanges. Additionally, the patient has bilateral hallux valgus deformities (bunions).

DIAGNOSIS

Bilateral brachymetapody with associated hallux valgus deformities.

DISCUSSION

Brachymetatarsia, or hypoplastic metatarsal, is a form of brachydactyly in which a single metatarsal is abnormally short. Brachymetapody involves multiple short metatarsals. Brachymetapody is most often congenital in origin and usually occurs as an isolated dysmelia. The considered pathogenesis is premature closure of the epiphyseal plate of the metatarsal bones without a specific cause.

Brachymetapody has been linked to several disease processes, including Down syndrome, Apert's syndrome, Albright hereditary osteodystrophy, myositis ossificans, Turner's syndrome, pseudohypoparathyroidism, sickle cell anemia, and dystrophic dwarfism. Brachymetatarsia and brachymetapody may be acquired postsurgery or secondary to trauma or Freiberg's disease.

Brachymetapody and brachymetatarsia can be unilateral, but patients present most often with a bilateral process. Many authors describe the fourth digit as the one most commonly involved. Some, however, state that congenital shortening of the first metatarsal, also known as Morton's syndrome, is the condition's most common manifestation.

Incidence of brachymetapody and brachymetatarsia is reported to be between 0.022% (one in 4586) and 0.05% (one in 1820). The ratio of male to female patients is approximately 1:20. The limited reports on hereditary patterns of brachymetapody and brachymetatarsia suggest the anomaly is autosomal dominant with incomplete manifestation. Variability of expression explains the differences in laterality and number of digits involved.

Patients with brachymetatarsia or brachymetapody usually present between the ages of 10 and 14, when the shortness of the metatarsals becomes apparent. Clinical suspicion of this diagnosis is raised in patients who present with atrophy of the involved toe and/or the toe drawn upwards on the dorsum of the foot in what is known as the “cocked-up” deformity.

Diagnosis is made radiographically when the involved metatarsal is 5 mm or more proximal to the parabolic arc of the metatarsal heads.

Patients may remain asymptomatic, or metatarsalgia may develop. The proximal phalanx of the shortened metatarsal comes to lie between the metatarsal heads and is unable to bear weight, which results in transfer metatarsalgia.

he cocked-up toe deformity sometimes also causes painful callus formation, and adjacent metatarsals may have increased plantar hyperkeratosis as a result of the increased load. As demonstrated in our case, a short third metatarsal can result in hallux valgus deformity when the medial toes angulate to occupy the space of the dorsiflexed third digit.

Treatment options for brachymetapody and brachymetatarsia include both operative and nonoperative techniques. Most patients do not require treatment, though both pain and cosmesis are appropriate indications for surgery. Nonoperative techniques include metatarsal pads and orthoses. Operative techniques include one-stage lengthening procedures for cases in which less than 15 mm of lengthening is needed. If more than 15 mm is needed, gradual metatarsal lengthening reduces the risk of neurovascular compromise in the affected digit.

Submitted by Andrew Allmendinger, DO, Paul Yeghiayan, MD, and Robert Perone, MD, all of St. Vincent's Medical Center in New York City.