and Uwe Spetzger1
Department of Neurosurgery, Klinikum Karlsruhe, Karlsruhe, Baden-Württemberg, Germany
The cervical spine has an exceptional position within spine surgery because of its filigree dimensions and its relations to numerous neurovascular structures. Knowledge of dimensions of vertebrae and discs is an essential precondition for surgical procedures with implantation of cages, prostheses or vertebral body replacements. Topographical anatomical relations are of great importance for the several surgical approaches.
The cervical spine is the most moveable and filigree part of the human spine. It is surrounded by numerous neurovascular structures: vertebral arteries, carotid arteries, nerve roots of the spinal cord and prevertebral ganglions. An overview over the dimensions of the seven cervical vertebrae as well as the medium heights of the cervical discs is given in Fig. 2.1 (Lang 1991).
Average height of cervical vertebrae and intervertebral discs
2.2 Vertebral Body, Intervertebral Disc and Uncinate Process
The cervical vertebrae 3–7 have a shape that is typical for the cervical spine (Fig. 2.2). The cervical vertebrae 1 and 2 (atlas and axis) have morphological and functional exceptional position because of their importance for movements of the head. The condyles of the squama occipitalis together with the cranial articular surfaces of the atlas form the atlanto-occipital joint (C0/C1) which is a big range of motion for flexion /extension . Atlas and axis form the atlantoaxial joint (C1/C2) which has a high degree of rotational ability. The functional level between axis and third cervical vertebra (C2/C3) enables a large amount of lateral flexion. The subaxial cervical spine from the third to the seventh vertebra shows a wide morphological homogeneity which reflects in the similar range of motion of the levels C3/C4 to C6/C7 (Table 3.1).
Anatomy of the cervical spine. Ventral view with the most relevant anatomical structures
A morphological special characteristic of the cervical spine is the uncinate process (Fig. 2.3) which is located at the cranial lateral aspects of the vertebral bodies. It limits rotational movements and provides integrity of the neuroforamen during lateral bending (Tubbs 2012). The upper uncinate processes a lateral orientation only, and the lower ones a dorsal orientation (Lang 1991).
Anatomy of the cervical spine. Lateral view with the most relevant anatomical structures
The intervertebral discs being deformable units fill the intervertebral spaces. Movements of vertebrae against each other base on an interaction of intervertebral discs and intervertebral joints (articulationes intervertebrales; see Sect. 2.3).
The intervertebral discs ensure the elasticity of the spinal column and work as a shock absorber (Lang 1991). The outer fibrous ring (anulus fibrosus) of the intervertebral disc surrounds the inner gel-like centre (nucleus pulposus) and consists of collagenous (90 %) and elastic (10 %) fibres (Fig. 2.2; Lang (1991).
2.3 Vertebral Arch and Facet Joints
The vertebral arches together with the segmental ligamenta flava form the dorsal limitation of the spinal canal and thus protect the spinal cord. The intervertebral joints (zygapophyseal joints) are often called facet joints in the clinical practice and are synovial joint between the superior articular process of one vertebra and the inferior articular process of the adjacent cranial vertebra (Fig. 2.3). The function of each pair of facet joints is the guidance and limitation of segmental motion (Frykholm 1969; Milne 1993).