title: Medial longitudinal arch biomechanics evaluation during gait in subjects with flexible flatfoot.
abstract: OBJECTIVE
  Medial longitudinal arch (MLA) strengthening has been considered an important part of successful flatfoot treatment. But, to date, the biomechanical loading behavior of the medial arch in flatfoot has not been evaluated. This study aimed to evaluate the MLA moment, MLA deformation angle, foot kinematics and ground reaction forces (GRF) in both normal foot and flatfoot groups.
  
  
  METHODS
  Each participant's foot was classified according to arch type using foot prints and radiographs. Twenty-eight non-obese adults (13 flatfeet and 15 normal feet) were involved. The biomechanics data were collected in a 3D motion analysis laboratory. The MLA biomechanics were calculated. Hindfoot and forefoot kinematics were also analyzed.
  
  
  RESULTS
  The flatfoot group had a significantly greater peak eversion MLA moment (p = 0.005) and a smaller peak MLA deformation angle (p < 0.05) during specific subphases. The peak of hindfoot plantarflexion (p < 0.05) and internal rotation (p < 0.05) and the peak of forefoot abduction ( p < 0.05) in the specific subphases were greater in the flatfoot group. The flatfoot group also had significantly smaller peak vertical GRF ( p < 0.05) during late stance and larger peak medial GRF (p < 0.05) during mid stance.
  
  
  CONCLUSIONS
  This study found a significantly greater eversion deforming force acting at the MLA structure, greater hindfoot and forefoot motion, less MLA flexibility and abnormal GRF in a flatfoot group during walking, which reflected the deficit of foot function in a flatfoot group.
authors.affiliation: Institute of Biomedical Engineering, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand.
authors.forename: Tulaya
authors.initials: T
authors.lastname: Prachgosin
authors.affiliation: Department of Biomedical Engineering, Faculty of Engineering, National University of Singapore, Singapore.
authors.forename: Desmond Y R
authors.initials: DY
authors.lastname: Chong
authors.affiliation: Department of Orthopaedic Surgery and Physical Medicine, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand.
authors.forename: Wipawan
authors.initials: W
authors.lastname: Leelasamran
authors.affiliation: Department of Mechanical Engineering, Faculty of Engineering, Prince of Songkla University, Songkhla, Thailand.
authors.forename: Pruittikorn
authors.initials: P
authors.lastname: Smithmaitrie
authors.affiliation: Institute of Biomedical Engineering, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand.
authors.forename: Surapong
authors.initials: S
authors.lastname: Chatpun
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D005260:Female; D005413:Flatfoot / Q000503:physiopathology* / Q000628:therapy; D005545:Forefoot, Human / Q000503:physiopathology; D005684:Gait / Q000502:physiology*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D011403:Pronation / Q000502:physiology; D016474:Weight-Bearing / Q000502:physiology; D055815:Young Adult