title: External torsion in a proximal tibia and internal torsion in a distal tibia occur independently in varus osteoarthritic knees compared to healthy knees.
abstract: BACKGROUND
  The relative torsional angle of the distal tibia is dependent on a deformity of the proximal tibia, and it is a commonly used torsional parameter to describe deformities of the tibia; however, this parameter cannot show the location and direction of the torsional deformity in the entire tibia. This study aimed to identify the detailed deformity in the entire tibia via a coordinate system based on the diaphysis of the tibia by comparing varus osteoarthritic knees to healthy knees.
  
  
  METHODS
  In total, 61 limbs in 58 healthy subjects (age: 54 ± 18 years) and 55 limbs in 50 varus osteoarthritis (OA) subjects (age: 72 ± 7 years) were evaluated. The original coordinate system based on anatomic points only from the tibial diaphysis was established. The evaluation parameters were 1) the relative torsion in the distal tibia to the proximal tibia, 2) the proximal tibial torsion relative to the tibial diaphysis, and 3) the distal tibial torsion relative to the tibial diaphysis.
  
  
  RESULTS
  The relative torsion in the distal tibia to the proximal tibia showed external torsion in both groups, while the external torsion was lower in the OA group than in the healthy group (p < 0.0001). The proximal tibial torsion relative to the tibial diaphysis had a higher external torsion in the OA group (p = 0.012), and the distal tibial torsion relative to the tibial diaphysis had a higher internal torsion in the OA group (p = 0.004) in comparison to the healthy group.
  
  
  CONCLUSIONS
  The reverse torsional deformity, showing a higher external torsion in the proximal tibia and a higher internal torsion in the distal tibia, occurred independently in the OA group in comparison to the healthy group. Clinically, this finding may prove to be a pathogenic factor in varus osteoarthritic knees.
  
  
  METHODS
  Level Ⅲ.
authors.affiliation: Department of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Science, Niigata, Japan; Department of Regenerative and Transplant Medicine, Niigata University Graduate School of Medical and Dental Science, Niigata, Japan. Electronic address: tommochi121710@gmail.com.
authors.forename: Tomoharu
authors.initials: T
authors.lastname: Mochizuki
authors.affiliation: Department of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Science, Niigata, Japan; Department of Regenerative and Transplant Medicine, Niigata University Graduate School of Medical and Dental Science, Niigata, Japan. Electronic address: tanifuji06242000@yahoo.co.jp.
authors.forename: Osamu
authors.initials: O
authors.lastname: Tanifuji
authors.affiliation: Department of Orthopaedic Surgery, Hokuetsu Hospital, Niigata, Japan. Electronic address: koga-y@ka2.so-net.ne.jp.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Koga
authors.affiliation: Department of Mechanical and Production Engineering, Faculty of Engineering, Niigata University, Niigata, Japan. Electronic address: f14b136g@mail.cc.niigata-u.ac.jp.
authors.forename: Ryosuke
authors.initials: R
authors.lastname: Hata
authors.affiliation: Department of Mechanical and Production Engineering, Faculty of Engineering, Niigata University, Niigata, Japan. Electronic address: f16b121h@mail.cc.niigata-u.ac.jp.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Mori
authors.affiliation: Niigata Institute for Health and Sports Medicine, Niigata, Japan. Electronic address: k.nishino@ken-supo.jp.
authors.forename: Katsutoshi
authors.initials: K
authors.lastname: Nishino
authors.affiliation: Department of Orthopaedic Surgery, Niigata Medical Center, Niigata, Japan. Electronic address: takuukat2032@gmail.com.
authors.forename: Takashi
authors.initials: T
authors.lastname: Sato
authors.affiliation: Department of Radiological Technology, Faculty of Health Sciences, Niigata University School of Medicine, Niigata, Japan. Electronic address: koichi.kobayashi11@gmail.com.
authors.forename: Koichi
authors.initials: K
authors.lastname: Kobayashi
authors.affiliation: Department of Health and Sports, Faculty of Health Sciences, Niigata University of Health and Welfare, Niigata, Japan. Electronic address: omori@nuhw.ac.jp.
authors.forename: Go
authors.initials: G
authors.lastname: Omori
authors.affiliation: Department of Radiological Technology, Faculty of Health Sciences, Niigata University School of Medicine, Niigata, Japan. Electronic address: sakamoto@clg.niigata-u.ac.jp.
authors.forename: Makoto
authors.initials: M
authors.lastname: Sakamoto
authors.affiliation: Department of Mechanical and Production Engineering, Faculty of Engineering, Niigata University, Niigata, Japan. Electronic address: y.tanabe@eng.niigata-u.ac.jp.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Tanabe
authors.affiliation: Department of Orthopedic Surgery, Niigata University Graduate School of Medical and Dental Science, Niigata, Japan; Department of Regenerative and Transplant Medicine, Niigata University Graduate School of Medical and Dental Science, Niigata, Japan. Electronic address: endless@med.niigata-u.ac.jp.
authors.forename: Naoto
authors.initials: N
authors.lastname: Endo
mesh_terms: D000368:Aged; D018483:Diaphyses / Q000000981:diagnostic imaging; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications / Q000000981:diagnostic imaging*; D013977:Tibia / Q000000981:diagnostic imaging*; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014102:Torsion Abnormality / Q000175:diagnosis / Q000209:etiology*