Sagittal Fluoroscopy for the Assessment of Hindfoot Kinematics

Current methods of quantifying foot kinematics during gait typically use markers placed externally on bony anatomic locations. These models are unable to analyze talocrural or subtalar motion because the talus lacks palpable landmarks to place external markers. Alternative methods of measuring these clinically relevant joint motions are invasive and have been limited to research purposes only. This study explores the use of fluoroscopy to noninvasively quantify talocrural and subtalar sagittal plane kinematics. A fluoroscopy system (FS) was designed and built to synchronize with an existing motion analysis system (MAS). Simultaneous fluoroscopic, marker motion, and ground reaction force (GRF) data were collected for five subjects to demonstrate system application. A hindfoot sagittal plane model was developed to evaluate talocrural and subtalar joint motion. Maximum talocrural plantar and dorsiflexion angles averaged among all the subjects occur at 12% and 83% of stance, respectively, with a range of motion of 20.1 deg. Maximum talocrural plantar and dorsiflexion angles averaged among all the subjects occur at toe-off and 67% of stance, respectively, with a range of motion of 8.7 deg. Based on the favorable comparison between the current fluoroscopically measured kinematics and previously reported results from alternative methods, it is concluded that fluoroscopic technology is well suited for measuring the sagittal plane hindfoot motion.