Measurement of vertical alignment of metatarsal heads using a novel ultrasonographic device

Although the vertical alignment of the metatarsal head (MTH) has been defined radiographically, data vary and are questionable. Recently, ultrasonography has been applied to measure the sole thickness of MTHs, but primarily in an unloading condition. This study designed a novel ultrasonographic device that incorporated a 10-MHz linear-array ultrasound (US) transducer on a platform to measure precisely the soft tissue thickness under the MTH on standing. A total of 25 healthy subjects with plantigrade feet were enrolled in this study. Each subject stood steadily on the platform, and the thickness of soft tissue of the MTH was measured based on the distance between the MTH and the plantar skin on the sonogram. The result showed that the MTHs were aligned linearly and inclined to the level surface with the first ray elevated. We concluded that there was neither transverse arch at the distal MTH on standing nor leveling alignment of the MTH, as speculated in conventional plantigrade foot studies.