title: Radiolucent lines in low-contact-stress mobile-bearing total knee arthroplasty: a blinded and matched case control study.
abstract: BACKGROUND
  Low-contact-stress (LCS) mobile-bearing total knee arthroplasty (TKA) (Johnson & Johnson, New Brunswick, NJ; previously: DePuy, Warsawa, USA) provides excellent functional results and wear rates in long-term follow-up analyses. Radiological analysis shows radiolucent lines (RLL) appearing immediately or two years after primary implantation, indicative of poor seat. Investigations proved RLL to be more frequent in uncemented TKA, resulting in a consensus to cement the tibial plateau, but their association with clinical findings and patients discomfort and knee pain is still unknown.
  
  
  METHODS
  553 patients with 566 low-contact-stress (LCS) total knee prostheses were screened for continuous moderate knee pain. We compared tibial stress shielding classified by Ewald in patients suffering from pain with a matched, pain-free control group on blinded X-rays. We hypothesized a positive correlation between pain and radiolucency and higher frequency of such radiolucent lines in the most medial and most lateral zones of the tibial plateau.
  
  
  RESULTS
  Twenty-eight patients suffered from knee pain in total. Radiolucencies were detected in 27 of these cases and in six out of 28 matched controls without knee pain. We could demonstrate a significant correlation of knee pain and radiolucencies, which appeared significantly more frequently in the outermost zones of the tibial plateau.
  
  
  CONCLUSIONS
  Our findings suggest that radiolucent lines, representing poor implant seat, about the tibial plateau are associated with knee pain in LCS patients. Radiolucencies are observed more often in noncemented LCS, and cementing the tibial plateau might improve implant seat and reduce both radiolucent lines and associated knee pain.
authors.affiliation: Department of Orthopaedics, Ludwig-Maximilians-University Munich, Campus Grosshadern, Marchioninistrasse 15, 81377 Munich, Germany. patricksadoghi@gmx.at
authors.forename: Patrick
authors.initials: P
authors.lastname: Sadoghi
authors.forename: Andreas
authors.initials: A
authors.lastname: Leithner
authors.forename: Patrick
authors.initials: P
authors.lastname: Weber
authors.forename: Jörg
authors.initials: J
authors.lastname: Friesenbichler
authors.forename: Gerald
authors.initials: G
authors.lastname: Gruber
authors.forename: Norbert
authors.initials: N
authors.lastname: Kastner
authors.forename: Katrin
authors.initials: K
authors.lastname: Pohlmann
authors.forename: Volkmar
authors.initials: V
authors.lastname: Jansson
authors.forename: Bernd
authors.initials: B
authors.lastname: Wegener
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects* / Q000379:methods; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007720:Knee Prosthesis / Q000009:adverse effects*; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery*; D011475:Prosthesis Failure / Q000009:adverse effects / Q000209:etiology*; D011859:Radiography; D012189:Retrospective Studies; D012737:Sex Factors; D016037:Single-Blind Method; D013314:Stress, Mechanical