title: Analysis of Impingement between Patella Bone and Bearing Post in Cruciate-Substituting High-Flexion Total Knee Arthroplasty.
abstract: BACKGROUND
  We investigated the causes of impingement between the patella bone and the bearing post during high flexion in cruciate-substituting total knee arthroplasty and proposed a treatment strategy.
  
  
  METHODS
  This prospective cohort study included 218 cases that had undergone cruciate-substituting total knee arthroplasty from February 2014 to January 2015; a single surgeon performed the operation using the same method without patellar resurfacing in all patients.
  
  
  RESULTS
  In these patients, the occurrence of impingement was determined by performing more than 120° high knee flexion after inserting a bearing perioperatively. The incidence of impingement was significantly associated with bearing design, femoral implant size, patella bone length, and patella inferior pole angle (p < 0.05). The impingement was resolved by resection of the lower articular side of the patella bone.
  
  
  CONCLUSIONS
  In the cruciate-substituting high-flexion total knee arthroplasty, impingement between the patella bone and bearing post was more common in patients with mobile bearing, small-size femoral component, and a long patella or a large inferior pole angle. In cases of intraoperative impingement between the patella bone and the bearing post, resection in the lower portion of the patella prevented impingement of the bearing with soft tissue or the patella by widening the space between the patella and the bearing post, which in turn prevented postoperative reduction in range of motion.
authors.affiliation: Department of Orthopaedic Surgery, Sun Medical Center, Daejeon, Korea.
authors.forename: Jegyun
authors.initials: J
authors.lastname: Chon
authors.affiliation: Department of Orthopaedic Surgery, Sun Medical Center, Daejeon, Korea.
authors.forename: Bongju
authors.initials: B
authors.lastname: Lee
authors.affiliation: Department of Orthopaedic Surgery, Sun Medical Center, Daejeon, Korea.
authors.forename: Sangyeop
authors.initials: S
authors.lastname: Shin
authors.affiliation: Department of Orthopaedic Surgery, Sun Medical Center, Daejeon, Korea.
authors.forename: Gunil
authors.initials: G
authors.lastname: Jang
authors.affiliation: Department of Orthopaedic Surgery, Sun Medical Center, Daejeon, Korea.
authors.forename: Taehyeon
authors.initials: T
authors.lastname: Jeon
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007720:Knee Prosthesis / Q000009:adverse effects / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D010329:Patella / Q000503:physiopathology*; D011183:Postoperative Complications / Q000453:epidemiology / Q000503:physiopathology; D011446:Prospective Studies; D011474:Prosthesis Design; D016059:Range of Motion, Articular / Q000502:physiology
keywords: Bearing post; High flexion; Impingement; Patella; Total knee arthroplasty