title: Correlation between hindfoot joint three-dimensional kinematics and the changes of the medial arch angle in stage II posterior tibial tendon dysfunction flatfoot.
abstract: BACKGROUND
  The aim of this study was to explore the correlation between the kinematics of the hindfoot joint and the medial arch angle change in stage II posterior tibial tendon dysfunction flatfoot three-dimensionally under loading.
  
  
  METHODS
  Computed tomography (CT) scans of 12 healthy feet and 12 feet with stage II posterior tibial tendon dysfunction flatfoot were taken both in non- and full-body-weight-bearing condition. The CT images of the hindfoot bones were reconstructed into three-dimensional models with Mimics and Geomagic reverse engineering software. The three-dimensional changes of the hindfoot joint were calculated to determine their correlation to the medial longitudinal arch angle.
  
  
  RESULTS
  The medial arch angle change was larger in stage II posterior tibial tendon dysfunction flatfoot compared to that in healthy foot under loading. The rotation and translation of the talocalcaneal joint, the talonavicular joint and the calcanocuboid joint had little influence on the change of the medial arch angle in healthy foot. However, the eversion of the talocalcaneal joint, the proximal translation of the calcaneus relative to the talus and the dorsiflexion of talonavicular joint could increase the medial arch angle in stage II posterior tibial tendon dysfunction flatfoot under loading.
  
  
  CONCLUSIONS
  Joint instability occurred in patients with stage II posterior tibial tendon dysfunction flatfoot under loading. Limitation of over movement of the talocalcaneal joint and the talonavicular joint may help correct the medial longitudinal arch in stage II posterior tibial tendon dysfunction flatfoot.
authors.affiliation: Department of Orthopedic Surgery, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, PR China. Electronic address: zhang63405460@126.com.
authors.forename: Yi-Jun
authors.initials: YJ
authors.lastname: Zhang
authors.affiliation: Department of Orthopedics, Huashan Hospital, Fudan University, Shanghai 200040, PR China. Electronic address: jame0615@yeah.net.
authors.forename: Jian
authors.initials: J
authors.lastname: Xu
authors.affiliation: Department of Orthopedic Surgery, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, PR China. Electronic address: wangyuebone2014@126.com.
authors.forename: Yue
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Orthopedic Surgery, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou 310003, PR China. Electronic address: linxiangjin2014@126.com.
authors.forename: Xiang-Jin
authors.initials: XJ
authors.lastname: Lin
authors.affiliation: Department of Orthopedics, Huashan Hospital, Fudan University, Shanghai 200040, PR China. Electronic address: maxinhuashan@yeah.net.
authors.forename: Xin
authors.initials: X
authors.lastname: Ma
mesh_terms: D000328:Adult; D000842:Ankle / Q000503:physiopathology; D001696:Biomechanical Phenomena; D002111:Calcaneus / Q000000981:diagnostic imaging / Q000503:physiopathology; D005260:Female; D005413:Flatfoot / Q000000981:diagnostic imaging / Q000503:physiopathology*; D033023:Foot Joints / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D007593:Joint Instability / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009068:Movement; D037081:Posterior Tibial Tendon Dysfunction / Q000503:physiopathology*; D013628:Talus / Q000000981:diagnostic imaging / Q000503:physiopathology; D014057:Tomography, X-Ray Computed; D016474:Weight-Bearing
keywords: Flatfoot deformity; Hindfoot joint; Medial arch angle; Three-dimensional motion