title: Plantar-flexion of the ankle joint complex in terminal stance is initiated by subtalar plantar-flexion: A bi-planar fluoroscopy study.
abstract: Gross motion of the ankle joint complex (AJC) is a summation of the ankle and subtalar joints. Although AJC kinematics have been widely used to evaluate the function of the AJC, the coordinated movements of the ankle and subtalar joints are not well understood. The purpose of this study was to accurately quantify the individual kinematics of the ankle and subtalar joints in the intact foot during ground walking by using a bi-planar fluoroscopic system. Bi-planar fluoroscopic images of the foot and ankle during walking and standing were acquired from 10 healthy subjects. The three-dimensional movements of the tibia, talus, and calcaneus were calculated with a three-dimensional/two-dimensional registration method. The skeletal kinematics were quantified from 9% to 86% of the full stance phase because of the limited camera speed of the X-ray system. At the beginning of terminal stance, plantar-flexion of the AJC was initiated in the subtalar joint on average at 75% ranging from 62% to 76% of the stance phase, and plantar-flexion of the ankle joint did not start until 86% of the stance phase. The earlier change to plantar-flexion in the AJC than the ankle joint due to the early plantar-flexion in the subtalar joint was observed in 8 of the 10 subjects. This phenomenon could be explained by the absence of direct muscle insertion on the talus. Preceding subtalar plantar-flexion could contribute to efficient and stable ankle plantar-flexion by locking the midtarsal joint, but this explanation needs further investigation.
authors.affiliation: Department of Mechanical Engineering, Chung-Ang University, 84 Heukseokro, Dongjak-gu, Seoul 156-756, Republic of Korea. Electronic address: skoo@cau.ac.kr.
authors.forename: Seungbum
authors.initials: S
authors.lastname: Koo
authors.affiliation: Department of Orthopedic Surgery, Seoul National University Bundang Hospital, Seongnam, Republic of Korea.
authors.forename: Kyoung Min
authors.initials: KM
authors.lastname: Lee
authors.affiliation: Department of Laboratory Medicine and Medical Device Clinical Trials Center, Chung-Ang University Hospital, Seoul, Republic of Korea.
authors.forename: Young Joo
authors.initials: YJ
authors.lastname: Cha
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000000981:diagnostic imaging / Q000502:physiology*; D001696:Biomechanical Phenomena; D005471:Fluoroscopy / Q000379:methods; D005528:Foot / Q000000981:diagnostic imaging / Q000502:physiology*; D005684:Gait / Q000502:physiology*; D064368:Healthy Volunteers; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D013380:Subtalar Joint / Q000000981:diagnostic imaging / Q000502:physiology*; D016138:Walking / Q000502:physiology*
keywords: Bi-planar fluoroscopic analysis; Foot and ankle; Gait; Joint kinematics; Subtalar joint