title: Range of motion and function are not affected by increased post constraint in patients undergoing posterior stabilized total knee arthroplasty.
abstract: BACKGROUND
  Constrained primary total knee arthroplasty (TKA) can provide stability in the face of incompetent collateral structures or irreconcilable flexion-extension imbalances. However, little is known about its effect on overall knee range of motion (ROM). This study determines whether TKA with increased constraint affects postoperative ROM.
  
  
  METHODS
  Patients undergoing primary TKA using either posterior stabilized (PS) or constrained condylar knee (CCK) inserts were match-paired based on body mass index, preoperative ROM, and direction and severity of the coronal deformity, yielding 68 pairs. ROM and Knee Society Score (KSS) were obtained preoperatively and at 6 weeks, 4 months, and 1 year.
  
  
  RESULTS
  When the 68 matched pairs were considered, all outcome variables related to ROM between the PS and CCK groups at each of the postoperative intervals were similar. Additionally, both the individual items and combined scores of the KSS were similar between groups at all time points.
  
  
  CONCLUSIONS
  We demonstrate that the use of increased constraint does not affect ROM, relief of pain, or function after TKA.
  
  
  METHODS
  Level III (retrospective case-controlled study, based on prospectively collected data).
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Special Surgery, 535 E. 70th Street, New York, NY 10021, United States.
authors.forename: Bryan R
authors.initials: BR
authors.lastname: King
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Special Surgery, 535 E. 70th Street, New York, NY 10021, United States. Electronic address: gladnickb@hss.edu.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Gladnick
authors.affiliation: Division of Biostatistics and Epidemiology, Hospital for Special Surgery, 535 E. 70th Street, New York, NY 10021, United States.
authors.forename: Yuo-yu
authors.initials: YY
authors.lastname: Lee
authors.affiliation: Division of Biostatistics and Epidemiology, Hospital for Special Surgery, 535 E. 70th Street, New York, NY 10021, United States.
authors.forename: Stephen
authors.initials: S
authors.lastname: Lyman
authors.affiliation: Department of Orthopaedic Surgery, Hospital for Special Surgery, 535 E. 70th Street, New York, NY 10021, United States.
authors.forename: Alejandro González
authors.initials: AG
authors.lastname: Della Valle
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation* / Q000379:methods; D005260:Female; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D016555:Matched-Pair Analysis; D008875:Middle Aged; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D012189:Retrospective Studies
keywords: Constrained condylar knee; Function; Pain relief; Range of motion; Total knee arthroplasty