Elements of a general theory of joints. 7. Mechanical structures of the relative motion of adjacent vertebrae.
The mechanical structure of the relative motion of adjacent vertebrae is given by the interplay of the artt. zygapophysiales, the intervertebral disk and the ligaments, respectively. This structure will be described in the 3 main functional planes. Horizontal plane (parallel to the disk): The two artt. zygapophysiales structurally represent a force locked, kinematically contrained four-bar-chain (link quadrangle). It possesses but one degree of freedom. The intervertebral disk does not influence, therefore, the kinematic structure but the extent of the motion. Frontal-coronal plane: The four-bar-chain of the frontal plane seems to be inflexible. Lateral bending is only possible combined with a right or left handed axial rotation. Vertical-sagittal plane: The artt. zygapophysiales work as a single dimeric link chain. The momentary rotational center lies on the common normal of the two articular surfaces. Its position upon that is determined by the geometry of the applied force system according to the "reciprocal theorem of synarthroses". Solely one direction of translation is possible. A translation perpendicular to the intervertebral disk is impossible in the cervical and thoracic region.
Nägerl
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H
IV. Physikalisches Institut, Georg-August-Universität, Göttingen, Deutschland.
Kubein-Meesenburg
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D
Fanghänel
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J
D001696:Biomechanical Phenomena; D006801:Humans; D007403:Intervertebral Disc / Q000502:physiology*; D007596:Joints / Q000033:anatomy & histology / Q000502:physiology*; D008022:Ligaments / Q000502:physiology*; D008159:Lumbar Vertebrae / Q000502:physiology; D009068:Movement / Q000502:physiology*; D013131:Spine / Q000033:anatomy & histology / Q000502:physiology*