title: A novel system of four-dimensional motion analysis after total hip arthroplasty.
abstract: We have developed a novel system of four-dimensional motion analysis after total hip arthroplasty (THA) that can aid in preventing dislocation by assessing safe range of motion for patients in several daily activities. This system uses skeletal structure data from CT and motion capture data from an infrared position sensor. A 3-D model reconstructed from CT data is combined with the motion capture data. Using this system, we analyzed hip motion when getting up from and sitting down in a chair or picking up an object while sitting in a chair in 17 patients (26 hips) who underwent THA. To assess the accuracy of this system's measurements, open MRI was used to evaluate positions of skin markers against bones in five healthy volunteers in various postures. No impingement between bones and/or implants was found in any subjects during any activities. However, mean angle at the point of maximum hip flexion was different for each patient. The open MRI results indicated that average error in hip angle of the present system was within 5 degrees for each static posture. The functional position of the pelvis during daily activities must be taken into account when assessing the real risk of dislocation. The present system enables dynamic analysis involving not only alignment of components and bones of each patient, but also individual differences in characteristics of daily motions. Further investigation using this system can help determine safe ranges of motion for preventing hip dislocation, improving the accuracy of individualized guidance for patients regarding postoperative activities.
authors.affiliation: Department of Orthopaedic Surgery, Osaka University Medical School, 2-2 Yamadaoka, Suita 565-0871, Osaka, Japan. k-hagiO@tc4.so-net.ne.jp
authors.forename: Keisuke
authors.initials: K
authors.lastname: Hagio
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Sugano
authors.forename: Takashi
authors.initials: T
authors.lastname: Nishii
authors.forename: Hidenobu
authors.initials: H
authors.lastname: Miki
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Otake
authors.forename: Asaki
authors.initials: A
authors.lastname: Hattori
authors.forename: Naoki
authors.initials: N
authors.lastname: Suzuki
authors.forename: Kazuo
authors.initials: K
authors.lastname: Yonenobu
authors.forename: Hideki
authors.initials: H
authors.lastname: Yoshikawa
authors.forename: Takahiro
authors.initials: T
authors.lastname: Ochi
mesh_terms: D000293:Adolescent; D000328:Adult; D019644:Arthroplasty, Replacement, Hip; D006617:Hip Dislocation / Q000517:prevention & control; D006621:Hip Joint / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging; D016059:Range of Motion, Articular