Combination of PedCAT Weightbearing CT With Pedography Assessment of the Relationship Between Anatomy-Based Foot Center and Force/Pressure-Based Center of Gravity.

Abstract

A customized pedography sensor (Pliance; Novel, Munich, Germany) was inserted into a pedCAT (Curvebeam, Warrington, PA). The aim of this study was to analyze the relative position of the anatomical foot center (FC) and the pedographic center of gravity (COG). The hypothesis was that FC should be a good predictor of mediolateral position of COG but not longitudinal since hindfoot anatomy allows free anteroposterior movement but limited mediolateral movement. In 90 patients (180 feet), a pedCAT scan with simultaneous pedography with full weightbearing in a standing position was performed. The morphology-based definition of the FC was performed with the pedCAT data following the Torque Ankle Lever Arm System (TALAS) algorithm. The force/pressure-based COG was defined with the pedography data using a software-based algorithm. The distance between FC and COG and the direction of a potential shift (distal-proximal, mediolateral) was measured and analyzed. COG motion during data acquisition was recorded and analyzed. Mean age of patients was 53.8 (range, 17-84) years, and 57 (63%) were female. The distance between FC and COG was 28.7 mm on average (range, 0-60). FC was distal to COG in 175 feet (97%; mean, 27.5 mm; range, -15 to 60) and lateral in 112 feet (62%; mean, 2.0 mm; range, -18 to 20). There was a constant and major distal longitudinal shift of COG relative to FC and an inconstant minor mediolateral shift. The data might be taken into consideration for planning and follow-up in foot and ankle surgery.