title: Inconsistencies between navigation data and radiographs in total knee arthroplasty are system-dependent and affect coronal alignment.
abstract: BACKGROUND
  Few studies have compared the effect of different computer navigation systems on postoperative alignment in patients who have had total knee arthroplasty (TKA). We examined 2 computed tomography (CT)-free computer navigation systems by comparing the accuracy of intraoperative measurements to postoperative alignment.
  
  
  METHODS
  Patients underwent unilateral TKA performed by a single surgeon using 1 of 2 CT-free navigation systems. We compared final intraoperative tibial and femoral coronal angles and mechanical axis with the same angles measured on standing postoperative radiographs.
  
  
  RESULTS
  Groups of 31 and 50 patients underwent TKA with the 2 systems, respectively. We noted a significant difference in the coronal tibial implant angle (1.29º ± 1.35º) and in the mechanical axis (1.59º ± 2.36º) for one navigation system (both p < 0.001), while only the coronal tibial implant angle showed a significant difference (1.17º ± 1.65º, p < 0.001) for the second system. The number of radiographic outliers also significantly differed. A significantly higher proportion (32%; p < 0.01) of patients in the second cohort exhibited unacceptable malalignment compared with the first cohort (24%).
  
  
  CONCLUSIONS
  Navigation systems for TKA continue to increase in sophistication and popularity. Owing to the significant difference in the proportion of alignment outliers in the 2 navigation systems tested in this study, orthopedic surgeons should not consider all TKA navigation systems equivalent. Additional investigations are needed to compare the accuracy of a variety of CT-free and CT-based navigation systems and to confirm our finding that accuracy is system-dependent.
authors.affiliation: The Division of Orthopaedic Surgery, McGill University, Montréal, Que.
authors.forename: Alberto
authors.initials: A
authors.lastname: Carli
authors.affiliation: The Division of Orthopaedic Surgery, McGill University, Montréal, Que.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Aoude
authors.affiliation: The Division of Orthopaedic Surgery, Lady Davis Institute for Medical Research-Jewish General Hospital, McGill University, Montréal, Que.
authors.forename: Avishai
authors.initials: A
authors.lastname: Reuven
authors.affiliation: The Division of Orthopaedic Surgery, McGill University, Montréal, Que.
authors.forename: Bogdan
authors.initials: B
authors.lastname: Matache
authors.affiliation: The Division of Orthopaedic Surgery, Lady Davis Institute for Medical Research-Jewish General Hospital, McGill University, Montréal, Que.
authors.forename: John
authors.initials: J
authors.lastname: Antoniou
authors.affiliation: The Division of Orthopaedic Surgery, Lady Davis Institute for Medical Research-Jewish General Hospital, McGill University, Montréal, Que.
authors.forename: David J
authors.initials: DJ
authors.lastname: Zukor
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D004867:Equipment Design; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D016343:Monitoring, Intraoperative / Q000295:instrumentation*; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000601:surgery*; D015641:Radiography, Interventional / Q000379:methods*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D025321:Surgery, Computer-Assisted / Q000379:methods*