title: Surface Damage Is Not Reduced With Highly Crosslinked Polyethylene Tibial Inserts at Short-term.
abstract: BACKGROUND
  Highly crosslinked ultrahigh-molecular-weight polyethylene (XLPE) has been shown to reduce wear in hip arthroplasty, but the advantages over conventional polyethylene (PE) in total knee arthroplasty (TKA), if any, remain unclear.
  
  
  OBJECTIVE
  Do differences exist in (1) surface damage as measured by damage score and percent area affected; and (2) extent and location of dimensional changes between XLPE and conventional PE observed on retrieved TKA tibial inserts?
  
  
  METHODS
  In this study of components retrieved at the time of revision surgery, we matched 44 XLPE to 44 conventional PE inserts from four manufacturers; the matching approach considered implant design (exact match), insert size (exact match), and length of implantation (matched ± 6 months). Surface damage on the articular surfaces was subjectively graded and digitally mapped to determine the percent damaged area of each damage mode. Three-dimensional changes that had occurred as a result of implantation were determined by comparing laser scans of the retrieved inserts with size-matched pristine inserts.
  
  
  RESULTS
  The differences of damage scores and percent damaged areas between the matched XLPE and conventional PE inserts were not large enough to be clinically significant with low corresponding levels of statistical significance (scores: 42 ± 13; 95% confidence interval [CI], 38-46 versus 45 ± 13; 95% CI, 41-49; p = 0.4; percent areas: 54% ± 38%; 95% CI, 44%-64% versus 54% ± 32%; 95% CI, 42%-65%; p = 0.9). However, XLPE inserts showed greater articular surface dimensional changes with high significance (root mean square of the distance: 0.16 ± 0.06 mm; 95% CI, 0.13-0.18 mm versus 0.14 ± 0.05 mm; 95% CI, 0.11-0.16 mm; p = 0.03). Within the same design, deviation patterns were consistent between the two materials; however, as expected, the location of the dimensional changes differed among designs: the negative deviations on the plateaus were centrally located in Zimmer PS inserts, were located on the perimeter in Smith & Nephew PS inserts, and were across the entire surface in DePuy PS inserts.
  
  
  CONCLUSIONS
  We found no difference in surface damage between matched XLPE and conventional PE inserts of the same designs. However, increased dimensional changes in TKAs with XLPE may reflect larger contact areas and potentially explain improved performance of XLPE in published simulator studies.
  
  
  CONCLUSIONS
  The lack of meaningful differences between the two polyethylene materials suggests caution in adopting a new, more expensive bearing material over another material that has a long track record of excellent behavior. A possible advantage is the greater dimensional changes, which could be the result of the lower creep resistance of XLPE, but this advantage awaits long-term results.
authors.affiliation: Department of Biomechanics, Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA. liut@hss.edu.|Department of Orthopaedics, China-Japan Union Hospital of Jilin University, Changchun, Jilin, China. liut@hss.edu.
authors.forename: Tong
authors.initials: T
authors.lastname: Liu
authors.affiliation: Department of Biomechanics, Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA.
authors.forename: Christina
authors.initials: C
authors.lastname: Esposito
authors.affiliation: Department of Biomechanics, Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA.
authors.forename: Marcella
authors.initials: M
authors.lastname: Elpers
authors.affiliation: Department of Biomechanics, Hospital for Special Surgery, 535 East 70th Street, New York, NY, 10021, USA.
authors.forename: Timothy
authors.initials: T
authors.lastname: Wright
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D020878:Device Removal; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D007719:Knee Joint / Q000503:physiopathology / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D016555:Matched-Pair Analysis; D008875:Middle Aged; D020959:Polyethylene / Q000737:chemistry*; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation; D012189:Retrospective Studies; D013314:Stress, Mechanical; D013499:Surface Properties; D013977:Tibia / Q000503:physiopathology / Q000601:surgery*; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D020959:Polyethylene