title: [Change in the joint line after total knee arthroplasty].
abstract: OBJECTIVE
  To investigate the change in joint line after knee arthroplasty.
  
  
  METHODS
  A total of 43 patients had 25 primary cruciate-retaining total knee replacements (Link Gemini MKII) and 25 rotational knee replacements (Link Endo-Model Rotational Knee System) sacrificing collateral ligaments and cruciate ligaments. Lateral radiographs were made both preoperatively and postoperatively. The change in the relative position of the joint line preoperatively and postoperatively was defined as the difference between the perpendicular distance from the weight-bearing surface of the tibial plateau to the tibial tubercle of the natural tibia (JL) and perpendicular distance from the weight-bearing surface of the prosthetic tibial component to the tibial tubercle (JL'). This distance was JL'-JL. The statistical differences between 2 groups were analyzed.
  
  
  RESULTS
  The distance of JL'-JL was 2.0 mm (-1.3 - 7.2 mm) in 22 patients with Gemini replacement, whereas the distance was 3.1 mm (-1.5 - 12.3 mm) in the other patients with rotational knee system. The difference was significant.
  
  
  CONCLUSIONS
  If the collateral ligaments and cruciate ligaments are removed during the knee replacement operations, the prosthetic joint line is likely to be malpositioned proximally. The fibular styloid and medial or lateral epicondylar reference points can be used to determine proper position of the joint line during operation.
authors.affiliation: Department of Orthopaedics, the First Hospital of Peking University, Beijing 100034, China. jointline@263.net
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Tian-yue
authors.initials: TY
authors.lastname: Zhu
authors.forename: Wei-bing
authors.initials: WB
authors.lastname: Chai
authors.forename: Hong-zhang
authors.initials: HZ
authors.lastname: Lu
authors.forename: Zhen-ning
authors.initials: ZN
authors.lastname: Liu
mesh_terms: D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000209:etiology / Q000517:prevention & control; D016896:Treatment Outcome