title: Migration of the instantaneous axis of motion during axial rotation in lumbar segments and role of the zygapophysial joints.
abstract: The biomechanical role of the zygapophysial joints was investigated for axial rotations of lumbar segments by recording the positions of the instantaneous helical axis (IHA) against the axial rotational angle and by relating these IHA-positions to anatomical landmarks. Cyclically varying pure axial moments were applied to 3 L1/L2, 7 L3/L4 and 3 L4/L5 segments. There were 800 segment positions per cycle taken by a custom-made high precision 3D-position measuring system. In intact segments IHA-migration reached from one zygapophysial joint to the other IHA-paths came up to 10-60 mm within small angular intervals (±1 deg). After removing the right joints, IHA-migration remained comparable with that of intact segments only for segment positions rotated to the right. Rotation to the left, however, approximately yielded stationary IHA-positions as found after resection of both joints. Hence, IHA-migration is determined by the joints already for small rotational angles. Each type of segment showed a typical pattern of IHA-migration.
authors.affiliation: Department of Trauma Surgery, Georg-August-University, Göttingen, Germany. martin.wachowski@web.de
authors.forename: Martin Michael
authors.initials: MM
authors.lastname: Wachowski
authors.forename: Thelonius
authors.initials: T
authors.lastname: Hawellek
authors.forename: Jan
authors.initials: J
authors.lastname: Hubert
authors.forename: Andrea
authors.initials: A
authors.lastname: Lehmann
authors.forename: Michael
authors.initials: M
authors.lastname: Mansour
authors.forename: Clemens
authors.initials: C
authors.lastname: Dumont
authors.forename: Jochen
authors.initials: J
authors.lastname: Dörner
authors.forename: Björn Werner
authors.initials: BW
authors.lastname: Raab
authors.forename: Dietmar
authors.initials: D
authors.lastname: Kubein-Meesenburg
authors.forename: Hans
authors.initials: H
authors.lastname: Nägerl
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena / Q000502:physiology; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology*; D008875:Middle Aged; D008954:Models, Biological; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation; D021801:Zygapophyseal Joint / Q000502:physiology*