title: Predictors of flexion using the rotating concave-convex total knee arthroplasty: preoperative range of motion is not the only determinant.
abstract: OBJECTIVE
  The range of motion achieved after a total knee arthroplasty (TKA) affects many daily activities and overall patients' satisfaction. This study aims to define the determinants affecting post-operative midterm active flexion according to a specific cruciate-sacrificing prosthesis, the rotating concave-convex (ROCC(®)) TKA.
  
  
  METHODS
  Four hundred and eighty-four consecutive patients (584 TKAs) were prospectively followed. After baseline patient demographics and anatomical characteristics, clinical and radiological post-operative assessments were periodically recorded. The rotational alignment of the femoral component was additionally reported for 120 patients. Eligibility for final inclusion was a minimum of 5-year follow-up. Univariate analyses followed by a multivariate model were fitted to determine the independent predictors of midterm active knee flexion.
  
  
  RESULTS
  Thirty-four TKA (5.8%) were excluded for a secondary surgery before their 50 years, 69 patients died (11.8%), and 21 (3.6%) were lost to follow-up. Overall, 460 TKAs were included. The post-operative mean knee flexion angle was measured at 127.7° ± 9.3°. Significant factors affecting final flexion under univariate analyses were the patient height and body mass index, the absence of previous surgery, a depressive state, the preoperative flexion angle, a preoperative flexion contracture, a patellar residual subluxation, the reconstructed patellar height, and the rotation of the femoral component. The multivariate model confirmed the patient's height, a depression, the preoperative flexion angle, a patellar residual subluxation, and the patellar height as statistically significant determinants.
  
  
  CONCLUSIONS
  Aside from the preoperative flexion angle, numerous predictors of flexion, both patient- and procedure-related were identified. Surgeons should take these into account both when adequately informing their patient before surgery and when performing the arthroplasty itself.
  
  
  METHODS
  Prognostic, Level II.
authors.affiliation: Service de chirurgie orthopédique et traumatologique, Hôpital Cochin, APHP, Université René Descartes, 27 rue du Faubourg Saint-Jacques, 75679, Paris Cedex 14, France, jeangast@gmail.com.
authors.forename: Jean
authors.initials: J
authors.lastname: Langlois
authors.forename: Anaïs
authors.initials: A
authors.lastname: Charles-Nelson
authors.forename: Sandrine
authors.initials: S
authors.lastname: Katsahian
authors.forename: Julien
authors.initials: J
authors.lastname: Beldame
authors.forename: Benjamin
authors.initials: B
authors.lastname: Lefebvre
authors.forename: Michel
authors.initials: M
authors.lastname: Bercovy
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D001827:Body Height; D003863:Depression / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D015999:Multivariate Analysis; D020370:Osteoarthritis, Knee / Q000601:surgery; D050177:Overweight / Q000453:epidemiology; D010329:Patella / Q000033:anatomy & histology; D063868:Patient Outcome Assessment; D011446:Prospective Studies; D016059:Range of Motion, Articular