title: Lack of axial rotation in mobile-bearing knee designs.
abstract: It has often been assumed rotational kinematics are improved with mobile-bearing TKA designs as the terms mobile-bearing and rotating platform imply. We tested this assumption by assessing the in vivo axial rotation magnitudes and patterns of 527 knees implanted with 12 different mobile-bearing TKA designs. Implants were grouped and compared by type--posterior stabilized (PS), posterior cruciate retaining (PCR), and posterior cruciate sacrificing (PCS)--and by specific design. We hypothesized all three mobile-bearing types (PS, PCR, and PCS) would achieve greater than 10 degrees average axial rotation and we would find no differences in axial rotation between types. Only 14% of PS knees, 3% of PCS knees, and 17% of PCR knees attained greater than 10 degrees axial rotation when measured from 0 degrees to 90 degrees . The percentage of PCS knees with greater than 10 degrees axial rotation was less compared with the other two groups. Axial rotation averaged 4.3 degrees , 2.5 degrees , and 3.8 degrees for the PS, PCS, and PCR knees, respectively. Incidences of reverse rotation were observed in 17% of PS knees, 32% of PCS knees, and 28% of PCR knees. Compared with the PCS group, the PS group achieved greater average axial rotation and had a lower percentage of knees displaying incidences of reverse rotation. The data refuted the hypotheses.
authors.affiliation: Grant Medical Center, Columbus, OH, USA. rwasiel2@ohiohealth.com
authors.forename: Ray C
authors.initials: RC
authors.lastname: Wasielewski
authors.forename: Richard D
authors.initials: RD
authors.lastname: Komistek
authors.forename: Sumesh M
authors.initials: SM
authors.lastname: Zingde
authors.forename: Kate C
authors.initials: KC
authors.lastname: Sheridan
authors.forename: Mohamed R
authors.initials: MR
authors.lastname: Mahfouz
mesh_terms: D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000209:etiology / Q000503:physiopathology*; D007719:Knee Joint / Q000503:physiopathology* / Q000601:surgery; D020370:Osteoarthritis, Knee / Q000601:surgery; D011379:Prognosis; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology*