title: Computer navigation for revision of unicompartmental knee replacements to total knee replacements: the results of a case-control study of forty six knees comparing computer navigated and conventional surgery.
abstract: OBJECTIVE
  The revision of unicompartmental knee replacements (UKRs) to total knee replacements (TKRs) using computer navigation is a little-known technique. The principal objective of this study was to analyse the radiological position of implants in revision of UKR to TKR comparing the results of surgery aided by computer navigation (CAS) with conventional surgery (CS). Our hypothesis was that computer navigation would improve the position of the implants.
  
  
  METHODS
  This is a retrospective single surgeon series. Forty-six patients (46 knees) with an average age 73 ± eight years (53-93) between January 1995 and December 2014 were included. The two groups were made up of 23 patients each and are comparable in terms of age, sex, side of surgery, age of the UKR, cause of failure and HKA angle before surgery. All patients were reviewed by two independent observers.
  
  
  RESULTS
  In the CAS group, the average hip-knee-ankle (HKA) angle was 179.2 ± 2.2° (175-184°). The average medial tibial mechanical angle (TMA) was 88.4 ± 1.6° (84-90°) and the medial femoral mechanical angle (FMA) was 91 ± 2° (87- 94°). The tibial slope was 88.7 ± 1.1° (87-90°). In the CS group, the average HKA angle was 179.9 ± 1.9° (175-183°), the TMA was on average 89.1 ± 1.3° (87-93°) and the FMA was 90.6 ± 1.5° (87-93°). The tibial slope was 87.8 ± 4.9° (85-95°). There was no statistically significant difference between the two groups on any of the radiological parameters studied.
  
  
  CONCLUSIONS
  Our radiological target of a post-operative HKA angle of 180 ± 3° was obtained in 87.5% of cases in the CS group and 92.4% of cases in the CAS group. This slight difference in favour of the computer-assisted group was not statistically significant, and we cannot therefore confirm our initial hypothesis, at least in the hands of an experienced surgeon. However, the quality of the results in the CAS group suggest that this technique could provide precious assistance to less experienced surgeons performing this surgery.
authors.affiliation: Department of Orthopaedic Surgery and Sport Traumatology, Grenoble South Teaching Hospital, 38130, Échirolles, France, DSaragaglia@chu-grenoble.fr.
authors.forename: Dominique
authors.initials: D
authors.lastname: Saragaglia
authors.forename: Jérémy
authors.initials: J
authors.lastname: Cognault
authors.forename: Ramsay
authors.initials: R
authors.lastname: Refaie
authors.forename: Brice
authors.initials: B
authors.lastname: Rubens-Duval
authors.forename: Roch
authors.initials: R
authors.lastname: Mader
authors.forename: René Christopher
authors.initials: RC
authors.lastname: Rouchy
authors.forename: Stephane
authors.initials: S
authors.lastname: Plaweski
authors.forename: Régis
authors.initials: R
authors.lastname: Pailhé
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D016022:Case-Control Studies; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000601:surgery; D008297:Male; D008875:Middle Aged; D011859:Radiography; D012086:Reoperation; D012189:Retrospective Studies; D025321:Surgery, Computer-Assisted; D013977:Tibia / Q000000981:diagnostic imaging / Q000601:surgery