title: Comparative study of intraoperative knee flexion with three different TKR designs.
abstract: BACKGROUND
  Substantial flexion after total knee arthroplasty (TKA) is required for certain categories of patients who wish to squat or kneel in their daily life. Many factors influence this postoperative flexion, including the prosthesis design. It is therefore valuable to in vivo analyze these factors on three knee prosthesis designs through a study of their intraoperative flexion.
  
  
  OBJECTIVE
  The posterior-stabilized (PS) knee prostheses provide better intraoperative flexion than the ultracongruent (UC) model. Of the currently available PS models, the high-flexion ones have better intraoperative flexion than standard models. Our main focus endpoint was the intraoperative flexion achieved, before soft-tissues closure, during TKA surgical procedure.
  
  
  METHODS
  This was a controlled study. Seventy-two osteoarthritic knees requiring TKA were included to compare three selected prosthesis models: the SAL ultracongruent and two PS models (the standard LPS and the LPS Flex). This was a single-operator study, with patients divided into three homogenous, comparable groups, in which intraoperative measurement of flexion was performed using computer-assisted navigation. Statistical analysis allowed comparison of the three models.
  
  
  RESULTS
  Intraoperatively, after prosthesis implantation, before soft-tissues closure, the mean flexion of the LPS-Flex was 134 degrees versus 124 degrees for the SAL (p=0.0004); the mean flexion of the standard LPS model was 130 degrees versus 124 degrees for the SAL (p=0.14); the PS Flex model showed no significant difference (p=0.26) in flexion (134 degrees) compared to the standard model (130 degrees). The SAL ultracongruent model seemed to be a factor reducing the intraoperative flexion by 8 degrees compared to the PS models (p<10(-4)).
  
  
  CONCLUSIONS
  In this study, the PS designs (standard or Flex) provided better intraoperative flexion than the SAL ultracongruent design. However, the LPS Prosthesis did not demonstrate superiority over the standard LPS Prosthesis.
  
  
  METHODS
  Level III, low-power prospective study.
authors.affiliation: Department of Orthopaedics, André-Mignot-Versailles Hospital Center, 78150 Le Chesnay, France. aw0@free.fr
authors.forename: A
authors.initials: A
authors.lastname: Wajsfisz
authors.forename: D
authors.initials: D
authors.lastname: Biau
authors.forename: P
authors.initials: P
authors.lastname: Boisrenoult
authors.forename: P
authors.initials: P
authors.lastname: Beaufils
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D005260:Female; D006801:Humans; D007720:Knee Prosthesis; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery*; D011446:Prospective Studies; D011474:Prosthesis Design; D016059:Range of Motion, Articular / Q000502:physiology; D018709:Statistics, Nonparametric; D016896:Treatment Outcome