title: No difference in range of motion between ultracongruent and posterior stabilized design in total knee arthroplasty: a randomized controlled trial.
abstract: OBJECTIVE
  The use of an ultracongruent (UC) insert with a standard femoral component for substitution of the posterior cruciate ligament (PCL) is a bone-preserving and therefore interesting alternative to the established box and cam mechanism of posterior stabilized (PS) total knee arthroplasty (TKA). This study investigated range of motion (ROM), stability and patient-reported outcome (PRO) in UC and PS TKA. We hypothesized better knee flexion with the PS design but no difference in stability and PRO between UC and PS TKA.
  
  
  METHODS
  A randomized controlled study was performed. One hundred and twenty-seven patients were included, 63 with an UC and 64 with a PS TKA (Columbus, Aesculap, Tuttlingen, Germany). Intraoperative stability and range of motion was measured with the use of a navigation system. Patients were assessed before surgery, 3 months and 1 year postoperatively.
  
  
  RESULTS
  There was no difference in ROM between both groups, neither intraoperatively nor at follow-up. There was 5 mm less sagittal translation at 90° of knee flexion (p < 0.001) and more posterior femoral rollback during knee flexion in the PS TKA. Axial rotation between extension and knee flexion was reduced by both designs. UC TKA was 7 min faster (p = 0.001). At the one-year follow-up, the Knee Society Score was similar in both groups, the Oxford Knee Score demonstrated better results in the UC TKA group (p = 0.048).
  
  
  CONCLUSIONS
  Increased intraoperative sagittal translation and reduced posterior femoral rollback during knee flexion of UC TKA seem to have no negative influence on short-term clinical outcome. Therefore, UC TKA seems to be a practical alternative to the established PS TKA for substitution of the PCL. This might be especially interesting for surgeons who do not always substitute the PCL.
  
  
  METHODS
  I.
authors.affiliation: University Center of Orthopaedics and Traumatology, University Medicine Carl Gustav Carus Dresden, TU Dresden, Fetscherst. 74, 01307, Dresden, Germany. Joerg.Luetzner@uniklinikum-dresden.de.
authors.forename: Jörg
authors.identifier: http://orcid.org/0000-0002-7162-828X
authors.initials: J
authors.lastname: Lützner
authors.affiliation: University Center of Orthopaedics and Traumatology, University Medicine Carl Gustav Carus Dresden, TU Dresden, Fetscherst. 74, 01307, Dresden, Germany.
authors.forename: Franziska
authors.initials: F
authors.lastname: Beyer
authors.affiliation: Forum Gesundheit Dresden MVZ, Dresden, Germany.
authors.forename: Julian
authors.initials: J
authors.lastname: Dexel
authors.affiliation: University Center of Orthopaedics and Traumatology, University Medicine Carl Gustav Carus Dresden, TU Dresden, Fetscherst. 74, 01307, Dresden, Germany.
authors.forename: Hagen
authors.initials: H
authors.lastname: Fritzsche
authors.affiliation: University Center of Orthopaedics and Traumatology, University Medicine Carl Gustav Carus Dresden, TU Dresden, Fetscherst. 74, 01307, Dresden, Germany.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Lützner
authors.affiliation: St. Vincentus-Kliniken, Karlsruhe, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Kirschner
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation / Q000379:methods; D005260:Female; D005269:Femur / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery*; D016119:Posterior Cruciate Ligament / Q000601:surgery; D011474:Prosthesis Design; D016059:Range of Motion, Articular; D012399:Rotation
keywords: Deep dished insert; Range of motion; Results; Stability; TKA; TKR; Ultracongruent insert