An in vivo study of hindfoot 3D kinetics in stage II posterior tibial tendon dysfunction (PTTD) flatfoot based on weight-bearing CT scan

Y Zhang; J Xu; X Wang; J Huang; C Zhang; L Chen; C Wang; X Ma

doi:10.1302/2046-3758.212.2000220

An in vivo study of hindfoot 3D kinetics in stage II posterior tibial tendon dysfunction (PTTD) flatfoot based on weight-bearing CT scan

Bone Joint Res. 2013 Dec 9;2(12):255-63. doi: 10.1302/2046-3758.212.2000220. Print 2013.

Authors

Y Zhang¹, J Xu, X Wang, J Huang, C Zhang, L Chen, C Wang, X Ma

Affiliation

¹ Huashan Hospital, Departmentof Orthopedics, Fudan University, Shanghai200040, China.

Abstract

Objective: The objective of this study was to evaluate the rotation and translation of each joint in the hindfoot and compare the load response in healthy feet with that in stage II posterior tibial tendon dysfunction (PTTD) flatfoot by analysing the reconstructive three-dimensional (3D) computed tomography (CT) image data during simulated weight-bearing.

Methods: CT scans of 15 healthy feet and 15 feet with stage II PTTD flatfoot were taken first in a non-weight-bearing condition, followed by a simulated full-body weight-bearing condition. The images of the hindfoot bones were reconstructed into 3D models. The 'twice registration' method in three planes was used to calculate the position of the talus relative to the calcaneus in the talocalcaneal joint, the navicular relative to the talus in talonavicular joint, and the cuboid relative to the calcaneus in the calcaneocuboid joint.

Results: From non- to full-body-weight-bearing condition, the difference in the talus position relative to the calcaneus in the talocalcaneal joint was 0.6° more dorsiflexed (p = 0.032), 1.4° more everted (p = 0.026), 0.9 mm more anterior (p = 0.031) and 1.0 mm more proximal (p = 0.004) in stage II PTTD flatfoot compared with that in a healthy foot. The navicular position difference relative to the talus in the talonavicular joint was 3° more everted (p = 0.012), 1.3 mm more lateral (p = 0.024), 0.8 mm more anterior (p = 0.037) and 2.1 mm more proximal (p = 0.017). The cuboid position difference relative to the calcaneus in the calcaneocuboid joint did not change significantly in rotation and translation (all p ≥ 0.08).

Conclusion: Referring to a previous study regarding both the cadaveric foot and the live foot, joint instability occurred in the hindfoot in simulated weight-bearing condition in patients with stage II PTTD flatfoot. The method used in this study might be applied to clinical analysis of the aetiology and evolution of PTTD flatfoot, and may inform biomechanical analyses of the effects of foot surgery in the future. Cite this article: Bone Joint Res 2013;2:255-63.

Keywords: Computed tomography; Stage II PTTD flatfoot; Three-dimensional image; Weight-bearing.

Grants and funding

This work was supported by the National Natural Science Foundation of China (No: 81171670) to X. Ma. Dr Y. Zhang and Dr J. Xu are co-first authors on this paper and contributed equally to this research.