title: The Mediolateral Excursion of the Meniscal Bearing during Flexion and Extension of the Knee after Medial Mobile-Bearing Unicompartmental Knee Arthroplasty.
abstract: This mediolateral excursion of the bearing during knee motion is supposed to be caused by external rotation of the tibia during knee extension. However, to our knowledge, there is no published clinical evidence supporting these hypotheses. The current study aimed to evaluate the mediolateral excursion of the bearing during flexion-extension motion of the knee after medial unicompartmental knee arthroplasty (UKA). In 52 knees, varus/valgus (F-VarVal) or rotational position (F-Rot) of the femoral component and relative location of the bearing were measured with the standing anteroposterior and modified axial view, respectively. We adopted the modified axial radiographs that are simple to assess the bearing position in the flexed knee. The modified axial view showed excellent inter- and intraobserver agreements. F-Rot in the modified axial view and CT showed a high agreement in terms of validity (r = 0.98;p< 0.0001). On average, the bearing showed more medial position in extension than flexion of the knee. No correlation was found between the femoral component positions (F-VarVal and F-Rot) and mediolateral bearing excursion (p= 0.68 and 0.80, respectively). In conclusion, coronal location of bearing according to flexion-extension of the knee is not influenced by the coronal and axial alignment of the femoral component. With simple radiographic method, more medial position of the bearing according to flexion-extension of the knee. Our method could be used to assess axial rotation of the femoral component and spin-out phenomenon of the bearing following the medial UKA.
authors.affiliation: Department of Orthopaedic Surgery, Seoul Barunsesang Hospital, Seoul, The Republic of Korea.
authors.forename: Seung-Yup
authors.initials: SY
authors.lastname: Lee
authors.affiliation: Department of Orthopaedic Surgery, Korea University Guro Hospital, Seoul, The Republic of Korea.
authors.forename: Ji-Hoon
authors.initials: JH
authors.lastname: Bae
authors.affiliation: Department of Orthopaedic Surgery, Barunsesang Hospital Ringgold Standard Institution, Seongnam, Gyeonggi-do, The Republic of Korea.
authors.forename: Dong-Won
authors.initials: DW
authors.lastname: Suh
authors.affiliation: Department of Orthopaedic Surgery, Korea University Guro Hospital, Seoul, The Republic of Korea.
authors.forename: Han-Ju
authors.initials: HJ
authors.lastname: Kim
authors.affiliation: Department of Orthopaedic Surgery, Seoul Barunsesang Hospital, Seoul, The Republic of Korea.
authors.forename: Hong-Chul
authors.initials: HC
authors.lastname: Lim
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D001696:Biomechanical Phenomena; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008592:Menisci, Tibial / Q000503:physiopathology*; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery*; D010020:Osteonecrosis / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D011187:Posture; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D012399:Rotation; D013977:Tibia / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery