title: Intraoperative patellar tendon strain: predicting the range of knee flexion after total knee arthroplasty.
abstract: BACKGROUND
  The preoperative range of motion is an important factor that influences the range of motion after total knee arthroplasty. Because the length and tightness of the extensor mechanism are extracapsular elements with an influence on knee flexion, it is reasonable to assume that the tension of the knee extensor mechanism during surgery has a considerable impact on the postoperative range of motion. The purpose of this study was to determine the influence of the tightness of knee extensor mechanism on postoperative knee flexion.
  
  
  METHODS
  In 18 knees undergoing posterior-stabilized type total knee arthroplasty, we measured the longitudinal strain on the patellar tendon with all the components in position during passive knee flexion up to 135 degrees . The patellar tendon strains measured during surgery were compared with the preoperative maximum knee flexion angle and postoperative maximum knee flexion angle at 1 year.
  
  
  RESULTS
  There was a significant inverse correlation between the patellar tendon strain during surgery at 60 degrees (r = -0.54, P < 0.05), 90 degrees (r = -0.55, P < 0.05), or 135 degrees of flexion (r = -0.65, P < 0.05) and postoperative knee flexion.
  
  
  CONCLUSIONS
  The results indicated that subjects with high intraoperative patellar tendon strain during passive flexion of the knee had more restricted postoperative knee flexion. Therefore, the tightness of the knee extensor mechanism measured at total knee arthroplasty is a good predictor of maximum postoperative range of flexion.
authors.affiliation: Department of Orthopaedic Surgery, Faculty of Medicine, University of Toyama, 2630 Sugitani Toyama, Toyama, 930-0194, Japan.
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Gejo
authors.forename: Yuji
authors.initials: Y
authors.lastname: Morita
authors.forename: Isao
authors.initials: I
authors.lastname: Matsushita
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Sugimori
authors.forename: Hiroki
authors.initials: H
authors.lastname: Watanabe
authors.forename: Tomoatsu
authors.initials: T
authors.lastname: Kimura
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000534:rehabilitation*; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017847:Patellar Ligament / Q000502:physiology*; D011446:Prospective Studies; D016059:Range of Motion, Articular / Q000502:physiology*; D013718:Tensile Strength