title: Modular Polyethylene Inserts for Total Knee Arthroplasty: Can Surgeons Detect 1-mm Thickness Increments?
abstract: Some manufacturers have introduced polyethylene (PE) inserts in 1-mm increment thickness options to allow for finer adjustments in total knee arthroplasty kinematics.
  
  
  
  Two surgeons with extensive experience performed 88 total knee arthroplasties using implants with 1-mm PE inserts. After trial components were inserted and the optimal PE thickness was selected, the insert was removed and a trial insert size was randomly chosen from opaque envelopes (1-mm smaller, same size, and 1-mm larger). The knee was re-examined and the surgeon determined which size PE had been placed.
  
  
  
  Surgeons reliably determined insert thicknesses in 62.5% (55 of 88; P = .050) of trials. Surgeons were not able to accurately detect 1-mm incremental changes of trial PE implants on a consistent basis.
  
  
  
  The potential clinical usefulness of this concept should be further evaluated.
authors.affiliation: Rothman Institute at Thomas Jefferson University Hospital, Philadelphia, Pennsylvania.
authors.forename: Joanne Y
authors.initials: JY
authors.lastname: Yoo
authors.affiliation: Rothman Institute at Thomas Jefferson University Hospital, Philadelphia, Pennsylvania.
authors.forename: Jenny
authors.initials: J
authors.lastname: Cai
authors.affiliation: Rothman Institute at Thomas Jefferson University Hospital, Philadelphia, Pennsylvania.
authors.forename: Antonia F
authors.initials: AF
authors.lastname: Chen
authors.affiliation: Rothman Institute at Thomas Jefferson University Hospital, Philadelphia, Pennsylvania.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Austin
authors.affiliation: Rothman Institute at Thomas Jefferson University Hospital, Philadelphia, Pennsylvania.
authors.forename: Peter F
authors.initials: PF
authors.lastname: Sharkey
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D001672:Biocompatible Materials; D002983:Clinical Competence; D003071:Cognition; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D000072161:Orthopedic Surgeons / Q000523:psychology / Q000592:standards; D020959:Polyethylene; D011474:Prosthesis Design; D011475:Prosthesis Failure
chemical_list: D001672:Biocompatible Materials; D020959:Polyethylene
keywords: 1-mm thickness; optimal polyethylene thickness; polyethylene inserts; randomized controlled trial; total knee arthroplasty; trial insert size