Abnormal Proximal Fifth Metatarsal and Os Vesalianum Pedis

To the Editor:

Abnormal foot bones can be observed as incidental radiographic findings and may have a congenital or developmental origin. Many asymptomatic accessory ossicles can also exist in the foot. We present a case of a fifth metatarsal with an abnormal tuberosity demonstrating unique features similar to those of os vesalianum pedis.

Case Report

A 52-year-old woman presented to the outpatient clinic of Orthopedics and Traumatology, Baskent University, Zübeyde Hanim Hospital, Izmir, Turkey, with the complaint of left heel pain. There was no history of trauma, and a detailed physical examination revealed a normal foot and ankle with mild tenderness at the sole of the rearfoot. A lateral oblique radiograph showed an abnormal tuberosity of the fifth metatarsal (Fig. 1). The tuberosity was unusually long, and there was a distinct articulation between the tuberosity and the lateral aspect of the cuboid bone. The same radiographic findings were observed in the asymptomatic right foot (Fig. 2).

Discussion

Many accessory bones can be found in the human foot, one of which is os vesalianum pedis. Accessory bones of the foot are considered to be developmental anomalies.[1] Various etiologic factors have been reported, including existence of an independent element in cartilage before calcification; misclassification as tendon bones; an independent ossification center; and existence of an unrecognized pathologic condition.[2]

We previously presented a case of os vesalianum pedis that was separated from the adjacent proximal fifth metatarsal by a thin, horizontally oriented, radiolucent line that likely represented synchondrosis.[3] Because of these unique features, the case was considered a “developmental variant.” There was an articulation between this ossicle and the cuboid bone.

Articulation with the cuboid bone, bilateral presentation, and absence of clinical symptoms characterized the present case as well as our previously presented case of os vesalianum pedis. In the present case, however, no radiolucent line separating the abnormal tuberosity from the fifth metatarsal was observed radiographically. This pathology seems to be a “developmental variant” of the proximal fifth metatarsal. Os vesalianum pedis and abnormal proximal fifth metatarsal may have a similar etiology. To our knowledge, this is the first report of this abnormality at the proximal region of the fifth metatarsal in a patient who had no pain in that region.