title: Surgical accuracy in high tibial osteotomy: coronal equivalence of computer navigation and gap measurement.
abstract: OBJECTIVE
  Medial opening wedge high tibial osteotomy (MOW HTO) is now a successful operation with a range of indications, requiring an individualised approach to the choice of intended correction. This manuscript introduces the concept of surgical accuracy as the absolute deviation of the achieved correction from the intended correction, where small values represent greater accuracy. Surgical accuracy is compared in a randomised controlled trial (RCT) between gap measurement and computer navigation groups.
  
  
  METHODS
  This was a prospective RCT conducted over 3 years of 120 consecutive patients with varus malalignment and medial compartment osteoarthritis, who underwent MOW HTO. All procedures were planned with digital software. Patients were randomly assigned into gap measurement or computer navigation groups. Coronal plane alignment was judged using the mechanical tibiofemoral angle (mTFA), before and after surgery. Absolute (positive) values were calculated for surgical accuracy in each individual case.
  
  
  RESULTS
  There was no significant difference in the mean intended correction between groups. The achieved mTFA revealed a small under-correction in both groups. This was attributed to a failure to account for saw blade thickness (gap measurement) and over-compensation for weight bearing (computer navigation). Surgical accuracy was 1.7° ± 1.2° (gap measurement) compared to 2.1° ± 1.4° (computer navigation) without statistical significance. The difference in tibial slope increases of 2.7° ± 3.9° (gap measurement) and 2.1° ± 3.9° (computer navigation) had statistical significance (P < 0.001) but magnitude (0.6°) without clinical relevance.
  
  
  CONCLUSIONS
  Surgical accuracy as described here is a new way to judge achieved alignment following knee osteotomy for individual cases. This work is clinically relevant because coronal surgical accuracy was not superior in either group. Therefore, the increased expense and surgical time associated with navigated MOW HTO is not supported, because meticulously conducted gap measurement yields equivalent surgical accuracy.
  
  
  METHODS
  I.
authors.affiliation: Department of Traumatology and Reconstructive Surgery, BG Traumacenter Tübingen, University of Tübingen, Schnarrenbergstr. 95, Tübingen, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Schröter
authors.affiliation: Department of Traumatology and Reconstructive Surgery, BG Traumacenter Tübingen, University of Tübingen, Schnarrenbergstr. 95, Tübingen, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Ihle
authors.affiliation: Department of Orthopaedics, Queen Elizabeth Hospital, Gateshead, UK. davidelson@yahoo.com.
authors.forename: D W
authors.initials: DW
authors.lastname: Elson
authors.affiliation: Department of Traumatology and Reconstructive Surgery, BG Traumacenter Tübingen, University of Tübingen, Schnarrenbergstr. 95, Tübingen, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Döbele
authors.affiliation: Department of Traumatology and Reconstructive Surgery, BG Traumacenter Tübingen, University of Tübingen, Schnarrenbergstr. 95, Tübingen, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Stöckle
authors.affiliation: Department of Traumatology and Reconstructive Surgery, BG Traumacenter Tübingen, University of Tübingen, Schnarrenbergstr. 95, Tübingen, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Ateschrang
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000601:surgery; D008297:Male; D008875:Middle Aged; D061646:Operative Time; D020370:Osteoarthritis, Knee / Q000601:surgery; D010027:Osteotomy / Q000379:methods* / Q000592:standards*; D011446:Prospective Studies; D025321:Surgery, Computer-Assisted / Q000592:standards*; D013977:Tibia / Q000601:surgery*; D016474:Weight-Bearing
keywords: Computer navigation; Gap measurement; High tibial osteotomy; Knee osteotomy; Medial compartment osteoarthritis; Surgical accuracy