title: Reliability of computer-assisted surgery as an intraoperative ruler in navigated high tibial osteotomy.
abstract: BACKGROUND
  Computer-assisted surgery (CAS) can act as an intraoperative ruler in high tibial osteotomy (HTO) to visualize continuously the leg during surgery.
  
  
  OBJECTIVE
  The aim of the study is to evaluate the accuracy of CAS with respect to preoperative planning and postoperative deviation from the planned leg axis in HTO. In addition, the influence of surgeon experience as well as operation time and perioperative complications are analyzed.
  
  
  METHODS
  A prospective multicenter study case series with follow-up at 6 weeks was performed in six centers. Medial open-wedge HTO with Tomofix(®) was done using computer assisted navigation technique with the Brainlab VV Osteotomy 1.0 module.
  
  
  RESULTS
  Fifty-one patients with medial gonarthritis were treated with navigated HTO. The follow-up rate was 98%. The majority of HTO-CAS patients fell within the tolerated limit of ±3° for leg axis deviation, however, seven patients were reported with deviations outside of this range: three patients had deviations of >3°-4.5° and four patients >4.5°, respectively. Eight intraoperative complications were documented, partially resulting from technical problems associated with the navigation system. During the 6-week follow-up period, three postoperative complications were experienced, all not associated with navigation technology.
  
  
  CONCLUSIONS
  In about 85% of cases, a perfect result in terms of deviation of the planned mechanical leg axis could be achieved. Computer assistance in HTO proved to be a helpful tool regarding intraoperative control of leg axis.
  
  
  METHODS
  Level I, High quality prospective study (all patients were enrolled at the same preoperative planning point with ≥80% follow-up of enrolled patients).
authors.affiliation: Department for Orthopaedic Trauma, Ulm University, Steínhövelstrasse 9, 89075, Ulm, Germany. florian.gebhard@uniklinik-ulm.de
authors.forename: Florian
authors.initials: F
authors.lastname: Gebhard
authors.forename: Christian
authors.initials: C
authors.lastname: Krettek
authors.forename: Tobias
authors.initials: T
authors.lastname: Hüfner
authors.forename: Paul A
authors.initials: PA
authors.lastname: Grützner
authors.forename: Ulrich
authors.initials: U
authors.lastname: Stöckle
authors.forename: Andreas B
authors.initials: AB
authors.lastname: Imhoff
authors.forename: Stephan
authors.initials: S
authors.lastname: Lorenz
authors.forename: Jan
authors.initials: J
authors.lastname: Ljungqvist
authors.forename: Peter
authors.initials: P
authors.lastname: Keppler
mesh_terms: D000328:Adult; D001860:Bone Plates; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery*; D010027:Osteotomy / Q000379:methods*; D011446:Prospective Studies; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted / Q000379:methods*; D013977:Tibia / Q000601:surgery*; D016896:Treatment Outcome