title: The use of navigation in medial opening wedge high tibial osteotomy can improve tibial slope maintenance and reduce radiation exposure.
abstract: OBJECTIVE
  We sought to determine the usefulness and the disadvantages of the navigation in medial opening wedge high tibial osteotomy (MOWHTO) compared to the conventional technique, in terms of target coronal alignment achievement, tibial slope maintenance, radiation exposure and operative time.
  
  
  METHODS
  We retrospectively compared 40 knees treated with navigated MOWHTO by one surgeon with 20 knees treated with conventional MOWHTO by another surgeon. Screw length of the plate was predetermined using validated simple algorithms only in the navigation group to facilitate the operation. The acceptable range of the postoperative coronal alignment was defined as 2°-6° of the mechanical tibiofemoral angle (mTFA) and 55%-70% of the weight loading line coordinate (WLL). The proportion of the coronal alignment outlier, posterior tibial slope change, fluoroscopy time and operative time were compared.
  
  
  RESULTS
  The coronal alignment outliers were fewer in the navigation group, but the differences were not significant (mTFA outlier 18% vs. 30%, p = 0.326; WLL outlier 20% vs. 30%, p = 0.519). Tibial slope was maintained in the navigation group (+0.3°, p = 0.732), whereas increased in the conventional group (+3°, p < 0.001). The fluoroscopy time was shorter in the navigation group (10.4 seconds vs. 24.8 seconds, p < 0.001). The operative time was comparable in both groups (41.3 minutes vs. 39.2 minutes, p = 0.232).
  
  
  CONCLUSIONS
  The use of navigation can improve tibial slope maintenance and reduce radiation exposure in MOWHTO, without considerable extension of operative time by optimising the surgical technique.
  
  
  METHODS
  Level III, retrospective comparative study.
authors.affiliation: Joint Reconstruction Center, Seoul National University Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do, 463-707, Republic of Korea. orthonyg@gmail.com.
authors.forename: Young Gon
authors.initials: YG
authors.lastname: Na
authors.affiliation: Joint Reconstruction Center, Seoul National University Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do, 463-707, Republic of Korea. eomsh22@hanmail.net.
authors.forename: Sang Hwa
authors.initials: SH
authors.lastname: Eom
authors.affiliation: Joint Reconstruction Center, Seoul National University Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do, 463-707, Republic of Korea. eclipse36@naver.com.
authors.forename: Seok Jin
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Joint Reconstruction Center, Seoul National University Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do, 463-707, Republic of Korea. moonjongchang@gmail.com.
authors.forename: Moon Jong
authors.initials: MJ
authors.lastname: Chang
authors.affiliation: Joint Reconstruction Center, Seoul National University Bundang Hospital, 166 Gumi-ro, Bundang-gu, Seongnam-si, Gyeonggi-do, 463-707, Republic of Korea. osktk@snubh.org.|Department of Orthopaedic Surgery, Seoul National University College of Medicine, Seoul, Republic of Korea. osktk@snubh.org.
authors.forename: Tae Kyun
authors.initials: TK
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D001860:Bone Plates; D001863:Bone Screws; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D061646:Operative Time; D020370:Osteoarthritis, Knee / Q000601:surgery; D010027:Osteotomy / Q000379:methods*; D011184:Postoperative Period; D000069079:Radiation Exposure / Q000517:prevention & control*; D012189:Retrospective Studies; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013977:Tibia / Q000601:surgery*
keywords: Computer-assisted surgery; Navigation; Osteoarthritis, knee; Osteotomy; Tibia