title: Mobile-bearing knees reduce rotational asymmetric wear.
abstract: Polyethylene wear of bearing components is the most common long-term complication in total knee arthroplasty. One would anticipate differing kinematics would generate different wear patterns (including wear type, degree, and symmetry) on the articulating surface of mobile-bearing and fixed-bearing inserts. Because mobile-bearing designs facilitate movement of the insert relative to the tray when the knee rotates, we hypothesized mobile-bearing designs would reduce the incidence of rotational asymmetric wear. We examined 51 worn tibial inserts, including 15 from mobile-bearing rotating-platform posterior-cruciate-sacrificing dished prostheses and 36 from fixed-bearing posterior-cruciate-retaining flat prostheses, which were retrieved at revision surgery with an average implantation time of 115 months. We divided wear types into low-grade wear (burnishing, abrasion, and cold flow) and high-grade wear (scratching, pitting, metal embedding, and delamination) to assess wear degree of polyethylene. To assess symmetry of wear, the insert surface was divided into medial and lateral sides and each side was further divided into three equal zones along the anteroposterior direction. Low-grade wear was more common in mobile-bearing knees, whereas high-grade wear was more common in fixed-bearing knees. We identified no internal/external rotational asymmetric wear or anteroposterior asymmetric wear in mobile-bearing knees.
authors.affiliation: Biomechanics Research Laboratory, Department of Biomedical Research, Mackay Memorial Hospital, Taipei, Taiwan.
authors.forename: Fang-Yuan
authors.initials: FY
authors.lastname: Ho
authors.forename: Hon-Ming
authors.initials: HM
authors.lastname: Ma
authors.forename: Jiann-Jong
authors.initials: JJ
authors.lastname: Liau
authors.forename: Chuan-Ren
authors.initials: CR
authors.lastname: Yeh
authors.forename: Chun-Hsiung
authors.initials: CH
authors.lastname: Huang
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D005260:Female; D006801:Humans; D007720:Knee Prosthesis; D008297:Male; D008422:Materials Testing; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000601:surgery; D020959:Polyethylene / Q000032:analysis*; D011183:Postoperative Complications; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation; D012399:Rotation; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D020959:Polyethylene