title: Sonography of polyethylene liners used in total knee arthroplasty.
abstract: OBJECTIVE
  We investigated the ability of sonography to reveal the polyethylene liner used in total knee arthroplasty with the hopes of establishing a possible relationship between the sonographic measurement of the actual thickness of the polyethylene liner and the estimated thickness based on conventional radiography.
  
  
  METHODS
  Twenty-four consecutive patients who were referred for Doppler screening for deep venous thrombosis after total knee arthroplasty were evaluated. The polyethylene liner was identified on sonography, and three measurements were obtained from four locations: anteromedial joint line (just medial to the midline incision), along the medial joint line, anterolateral joint line (just lateral to the midline incision), and along the lateral joint line. These sonographic measurements were compared with radiographic measurements of the radiolucent polyethylene liner and with the manufacturers' stated size of the polyethylene liner. Linear regression analyses were then performed.
  
  
  RESULTS
  The polyethylene liner is seen on sonography as a strong linear echogenic interface with posterior acoustic shadowing. Linear regression analyses showed a high correlation (r = 0.8) between the sonographic measurements and the radiographic measurements. A relatively poor correlation (r = 0.2) was noted between the manufacturers' stated size of the liner and the sonographic measurements.
  
  
  CONCLUSIONS
  We found that the polyethylene liner used in total knee arthroplasty can be clearly identified during sonographic evaluation of the knee. We also found a high correlation between the longitudinal measurement of the polyethylene liner with the thickness of the radiolucent polyethylene as measured on conventional radiographs. We propose that sonography could potentially be a useful noninvasive imaging modality to screen for subtle cases of polyethylene wear.
authors.affiliation: Department of Radiology and Imaging, Hospital for Special Surgery, 535 E. 70th Street, New York, NY 10021, USA.
authors.forename: Carolyn M
authors.initials: CM
authors.lastname: Sofka
authors.forename: Ronald S
authors.initials: RS
authors.lastname: Adler
authors.forename: Richard
authors.initials: R
authors.lastname: Laskin
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D020959:Polyethylene; D011474:Prosthesis Design; D014463:Ultrasonography
chemical_list: D020959:Polyethylene