title: Features of hindfoot 3D kinetics in flat foot in ankle-joint maximal dorsiflexion and plantarflexion.
abstract: BACKGROUND
  It is difficult to evaluate the kinematics of flat foot from 2D images, and no definitive methods have so far been established to diagnose flat foot. This study evaluated hindfoot kinetics through the progression of posterior tibial tendon dysfunction (PTTD) in patients with stages II and III PTTD flat foot compared with those in normal patients under dorsiflexion and plantarflexion conditions using 3D  computed tomography (CT) reconstruction images.
  
  
  METHODS
  CT images were taken of 26 normal and 32 flat feet in neutral, plantarflexion, and dorsiflexion positions of the ankle joint, from which 3D virtual models were made of each hindfoot bone. The 3D bone motion of these models was calculated using volume merge methods in three major planes.
  
  
  RESULTS
  Tibiotalar-joint motion in ankle-joint plantarflexion became less plantarflexed (normal -41.2°, stage II -33.5°, stage III -25.3°) and less adducted (normal -13.9°, stage II -10.7°, stage III -5.6°) as the stage progressed. Talocalcaneal-joint  motion in stage III became more plantarflexed (normal -0.8°, stage II -3.0°, stage III -8.7°) and more adducted (normal -0.3°, stage II -4.7°, stage III -10.3°) as the stage progressed. Talonavicular-joint motion in stage III became more plantarflexed (normal -7.2°, stage II -7.6°, stage III -14.9°) and more adducted (normal 1.0°, stage II -7.3°, stage III -17.9°) as the stage progressed.
  
  
  CONCLUSIONS
  Tibiotalar-joint plantarflexion decreased and talocalcaneal and talonavicular-joint adduction increased in the maximal ankle-joint plantarflexion in stage II in comparison with normal cases. Tibiotalar-joint plantarflexion and adduction were decreased and of the talocalcaneal and talonavicular joints increased in stage III in comparison with stage II cases.
authors.affiliation: Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine, Kawaramachi-Hirokoji, Kamigyo-ku, Kyoto, 602-8566, Japan.
authors.forename: Kan
authors.initials: K
authors.lastname: Imai
authors.forename: Kazuya
authors.initials: K
authors.lastname: Ikoma
authors.forename: Masahiro
authors.initials: M
authors.lastname: Maki
authors.forename: Masamitsu
authors.initials: M
authors.lastname: Kido
authors.forename: Yoshiro
authors.initials: Y
authors.lastname: Tsuji
authors.forename: Ryota
authors.initials: R
authors.lastname: Takatori
authors.forename: Daisaku
authors.initials: D
authors.lastname: Tokunaga
authors.forename: Nozomu
authors.initials: N
authors.lastname: Inoue
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Kubo
mesh_terms: D000328:Adult; D000843:Ankle Joint / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001696:Biomechanical Phenomena; D002111:Calcaneus / Q000000981:diagnostic imaging / Q000503:physiopathology; D005260:Female; D005413:Flatfoot / Q000000981:diagnostic imaging / Q000503:physiopathology*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D013628:Talus / Q000000981:diagnostic imaging / Q000503:physiopathology; D014057:Tomography, X-Ray Computed / Q000379:methods