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11 Mann Award-Kido manuscript_Fig 1.gif
Fig. 1 A 3D CT model of the tibia and the hindfoot bones (talus, navicular, and calcaneus). A global X-Y-Z coordinate system corresponding to anatomical axes was used to describe the orientation of tarsal bones. The Z-axis was set along the tibial shaft through the center of the ankle, and the Y-axis was set parallel to the projection of a line connecting the center of the heel and the second metatarsal head on a plane perpendicular to the Z-axis. The X-axis was determined according to a right-hand rule from the Y-axis and the Z-axis. Used with permission of Foot & Ankle International.

AAOS Now

Published 9/1/2011
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Terry Stanton

Study provides 3-D view of flatfoot

At the 2011 annual meeting of the American Orthopaedic Foot & Ankle Society, the Roger A. Mann Award for best clinical paper went to the first study to use three-dimensional (3-D) computed tomography (CT) imaging to visualize feet with flatfoot deformity under full weight bearing.

The study was performed by Masamitsu Kido, MD, and associates at the department of orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Japan.

Researchers took CT scans of 21 normal feet and 21 feet with flatfoot deformity in both nonload and full-body, weight-bearing load conditions, and made 3-D models based on the images. They then calculated the rotation of the following bones: the talus relative to the tibia in the tibiotalar joint, the navicular relative to the talus in the talonavicular joint, and the calcaneus relative to the talus in the talocalcaneal joint.

The investigators had hypothesized that that the motions of the talus, navicular, and calcaneus observed at the tarsal joints in patients with flatfoot deformity would increase under loading, especially around the hindfoot, due to either posterior tibial tendon dysfunction or a failure of soft supporting tissues.

A global X-Y-Z coordinate system corresponding to the anatomic axes was used to describe the orientation of tarsal bones (Fig. 1). The coronal (XY), sagittal (XZ), and transverse (YZ) planes were defined from these X-Y-Z axes. A local coordinate system was defined for each tarsal bone with its origin at the gravity center of each bone and the same orientations as the X-Y-Z axes.

The rotation of the talus under loading relative to the tibia at the tibiotalar joint was larger in the plantarflexed direction in a flatfoot as compared to a normal foot (P = 0.031). But no significant differences were observed in either the coronal plane or the transverse plane.

Under loading, the flatfoot navicular was more everted in the coronal plane relative to the talus at the talonavicular joint as compared to the normal foot navicular (P = 0.0034), but no significant difference was observed in either the sagittal plane or the transverse plane.

Significant differences were also found for dorsiflexion in the sagittal plane (P = 0.006) and eversion in the coronal plane (P = 0.0018) for the calcaneus in the flatfoot compared to a normal foot calcaneus, relative to the talus at the talocalcaneal joint under loading. No significant difference was observed in the transverse plane.

The total rotations under loading were significantly larger in the flatfoot compared with the normal foot in all three joints (tibiotalar, talonavicular, and talocalcaneal)

According to the authors, the increased precision of this method, over 2-D imaging and cadaver studies used to evaluate flatfoot, could have clinical benefits in classifying flatfoot and in providing a tarsal kinetic analysis to evaluate the effects of foot surgery.

Co-authors of “Load response of the tarsal bones in patients with flatfoot deformity: In vivo 3D kinematic study” are Kazuya Ikoma, MD, PhD; Kan Imai, MD; Masahiro Maki, MD, PhD; Ryota Takatori, MD, PhD; Daisaku Tokunaga, MD, PhD; Nozomu Inoue, MD, PhD; Toshikazu Kubo, MD, PhD.

Disclosure information: Drs. Kubo, Inoue, and Tokunaga—no conflicts; Drs. Kido, Takatori, Maki, Imai, and Ikoma—no data.

Terry Stanton is senior science writer for AAOS Now. He can be reached at tstanton@aaos.org

Bottom Line

  • This study used CT scans of both normal feet and flatfeet to create 3-D models so researchers could measure the effect of loading on flatfoot deformity.
  • Researchers found differences in rotational movements among tarsal bones between the flatfeet and the normal feet.
  • This process may be helpful in clinical analysis of foot problems and in evaluating the effects of foot surgery in the future.