title: Accuracy of computer-assisted total knee arthroplasty related to extra-articular tibial deformities.
abstract: OBJECTIVE
  To compare the accuracy of postoperative mechanical alignment in computer-assisted total knee arthroplasties (CAS-TKA) related to various degrees of extra-articular tibial deformity.
  
  
  METHODS
  We performed CAS-TKA on 30 knee models in which extra-articular proximal tibial deformities were preset to have malalignments ranging from 30° of varus to 30° of valgus. The knees were assigned to two groups, designated Group A (knees with ≤ 15° preoperative malalignment) and Group B (knees with > 15° preoperative malalignment), and the postoperative mechanical alignment in the two groups was compared using a computer-assisted surgery (CAS) system. Resected bone pieces from the distal femurs and proximal tibias were measured with a digital Vernier caliper and the results compared with the CAS calculations to evaluate the execution accuracy of the bone resection.
  
  
  RESULTS
  There was no outlier in either group when a ± 3° deviation from neutral mechanical alignment was set as the acceptance criterion. Interestingly, Group B showed significantly more outliers when the acceptance criterion was a deviation of ± 2° (26.67%, p = 0.0317) or ± 1° (6.67%, p = 0.0007) from neutral alignment. There was no statistical difference between the groups in terms of the execution accuracy of the bone resection.
  
  
  CONCLUSIONS
  The CAS-TKA approach provided significantly less alignment accuracy in tibia with greater preoperative frontal deformity, despite there being no outliers beyond ± 3°.
authors.affiliation: Department of Orthopaedics, Faculty of Medicine, Chulalongkorn University , Bangkok , Thailand.
authors.forename: Saran
authors.initials: S
authors.lastname: Tantavisut
authors.forename: Aree
authors.initials: A
authors.lastname: Tanavalee
authors.forename: Srihatach
authors.initials: S
authors.lastname: Ngarmukos
authors.forename: Pongsak
authors.initials: P
authors.lastname: Yuktanandana
authors.forename: Vajara
authors.initials: V
authors.lastname: Wilairatana
authors.forename: Yongsak
authors.initials: Y
authors.lastname: Wangroongsub
mesh_terms: D019645:Arthroplasty, Replacement, Knee; D017760:Bone Malalignment / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery*; D006801:Humans; D007719:Knee Joint / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D008954:Models, Biological; D016059:Range of Motion, Articular; D015203:Reproducibility of Results; D025321:Surgery, Computer-Assisted; D013977:Tibia / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery