title: Joint line changes and outcomes in constrained versus unconstrained total knee arthroplasty for the type II valgus knee.
abstract: OBJECTIVE
  The objective of this study was to compare the outcome of constrained and unconstrained primary total knee arthroplasty (TKA) in the management of the valgus deformity.
  
  
  METHODS
  This is a retrospective review of patients with type II valgus knee who underwent primary TKA from 1999 to 2011. There were fifty patients in Group 1 who underwent varus-valgus constrained TKA. They were matched with another fifty patients in Group 2 who underwent unconstrained TKA.
  
  
  RESULTS
  The mean joint line shift was significantly higher in Group 1 (+8 mm, SD 6 mm) than in Group 2 (+2 mm, SD 3 mm) (p = 0.03). At 2 years, there was no difference in anterior-posterior stability and mediolateral stability according to the Knee Society Score, and patients in Group 2 reported significantly better mean function score of 66.2 (SD 9.3) (mean 48, SD 7.1 in Group 1) (p = 0.002). Two patients (6 %) in Group 1 underwent revision surgery--one for a broken central peg and the other for aseptic loosening. Three patients (2 %) in Group 2 underwent revision surgery--two for global instability and one for poly wear. The estimated survivorship time was 8.3 years for constrained TKA and 12.0 for unconstrained TKA.
  
  
  CONCLUSIONS
  Constrained TKA was associated with more significant joint line changes for the management of valgus arthritic knee, when compared with unconstrained TKA.
  
  
  METHODS
  Retrospective study, Level III.
authors: Department of Orthopaedic Surgery, Singapore General Hospital, 1 Outram Road, Singapore, 169608, Singapore, pangheenee@hotmail.com.
authors: Hee-Nee
authors: HN
authors: Pang
authors: Seng-Jin
authors: SJ
authors: Yeo
authors: Hwei-Chi
authors: HC
authors: Chong
authors: Pak-Lin
authors: PL
authors: Chin
authors: Shi-Lu
authors: SL
authors: Chia
authors: Ngai-Nung
authors: NN
authors: Lo
mesh_terms: D000368:Aged; D001172:Arthritis, Rheumatoid / Q000150:complications / Q000473:pathology / Q000601:surgery*; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation / Q000379:methods*; D060751:Bone Retroversion / Q000150:complications / Q000473:pathology / Q000601:surgery*; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D007593:Joint Instability / Q000209:etiology; D007719:Knee Joint / Q000473:pathology* / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000150:complications / Q000473:pathology / Q000601:surgery*; D011183:Postoperative Complications; D020127:Recovery of Function; D012086:Reoperation; D012189:Retrospective Studies; D016896:Treatment Outcome