Keisuke Komiyama1, Satoshi Hamai2, Satoru Ikebe3, Kensei Yoshimoto1, Hidehiko Higaki4, Kyohei Shiomoto1, Hirotaka Gondo4, Daisuke Hara1, Yifeng Wang4, Yasuharu Nakashima1. 1. Department of Orthopedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan. 2. Department of Orthopedic Surgery, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan. Electronic address: hamachan@ortho.med.kyushu-u.ac.jp. 3. Department of Creative Engineering, National Institute of Technology, Kitakyushu College, 5-20-1 Shii, Kokuraminami-ku, Kitakyushu, Fukuoka 802-0985, Japan. 4. Department of Life Science, Faculty of Life Science, Kyushu Sangyo University, 2-3-1 Matsugadai, Higashi-ku, Fukuoka, 813-0004, Japan.
Abstract
BACKGROUND: Dynamic hip kinematics during stationary cycling after total hip arthroplasty (THA) have been unclear. Furthermore, no computer simulation of optimal cup position based on in vivo kinematics has yet been assessed. METHODS: This study consisted of 7 patients who underwent unilateral primary THA for symptomatic osteoarthritis. Using a flat-panel X-ray detector, continuous radiographs were obtained during stationary cycling. We analyzed the three-dimensional replaced hip kinematics from the top to the bottom position of the crank using image-matching techniques and quantified minimum liner-to-stem neck distance. Simulation analyses with in vivo kinematics were performed to examine patient-specific optimal cup placement against prosthetic impingement. FINDINGS: During stationary cycling, pelvis showed 27.1° of posterior tilt on average without significant change. Hip flexed by 59.4° and 19.3° on average at the top and bottom positions, respectively. Minimum liner-to-neck distance was 8.8 mm on average at the bottom position. Liner-to-neck, bone-to-bone, or bone-to-component impingement was not observed at any positions in any hips. Simulation analysis of cup placement showed that larger cup anteversion, inclination, and use of elevated liner significantly decreased the minimum distance between posterior liner and stem neck. Cup anteversion of more than 30° with elevated liner could cause posterior liner-to-neck impingement at bottom position. INTERPRETATION: Stationary cycling after THA provides no excessive hip range of motion or liner-to-neck contact. Cup placement and use of elevated liner significantly influence the minimum liner-to-neck distance, in some cases simulating posterior prosthetic impingement.
BACKGROUND: Dynamic hip kinematics during stationary cycling after total hip arthroplasty (THA) have been unclear. Furthermore, no computer simulation of optimal cup position based on in vivo kinematics has yet been assessed. METHODS: This study consisted of 7 patients who underwent unilateral primary THA for symptomatic osteoarthritis. Using a flat-panel X-ray detector, continuous radiographs were obtained during stationary cycling. We analyzed the three-dimensional replaced hip kinematics from the top to the bottom position of the crank using image-matching techniques and quantified minimum liner-to-stem neck distance. Simulation analyses with in vivo kinematics were performed to examine patient-specific optimal cup placement against prosthetic impingement. FINDINGS: During stationary cycling, pelvis showed 27.1° of posterior tilt on average without significant change. Hip flexed by 59.4° and 19.3° on average at the top and bottom positions, respectively. Minimum liner-to-neck distance was 8.8 mm on average at the bottom position. Liner-to-neck, bone-to-bone, or bone-to-component impingement was not observed at any positions in any hips. Simulation analysis of cup placement showed that larger cup anteversion, inclination, and use of elevated liner significantly decreased the minimum distance between posterior liner and stem neck. Cup anteversion of more than 30° with elevated liner could cause posterior liner-to-neck impingement at bottom position. INTERPRETATION: Stationary cycling after THA provides no excessive hip range of motion or liner-to-neck contact. Cup placement and use of elevated liner significantly influence the minimum liner-to-neck distance, in some cases simulating posterior prosthetic impingement.