ANATOMY OF SPINE Dr Pankaj N Surange MBBS, MD, FIPP Interventional Pain and Spine specialist
Anatomical Planes A-P X-ray of a scoliotic spine in the coronal plane. The CORONAL PLANE , also called the FRONTAL PLANE , is a vertical cut that divides the body into front and back sections. Physicians look at the coronal plane when they view an A-P (anterior-posterior) x-ray of the spine to evaluate scoliosis.
Anatomical Planes Lateral X-ray of a kyphotic spine in the sagittal plane. The SAGITTAL or MEDIAN PLANE is a vertical cut that divides the body into left and right sections. The sagittal view is seen by surgeons on a lateral x-ray of the spine.
Anatomical Planes CT Scan of a thoracic vertebra in the axial plane. The AXIAL or TRANSVERSE PLANE is a horizontal cut that divides the body into upper and lower sections. To best view the axial plane of the spine, surgeons will often obtain a CT scan with axial cuts.
spinal cord and nerve roots
Functions of the Spine
Flexibility of motion in six degrees of freedom
Functions of the Spine Left and Right Side Bending Flexion and Extension Left and Right Rotation
Structural support and balance for upright posture
The spine is the axle bearing the load of the head, shoulders and thorax. The upper body weight is then distributed to the lower extremities through the sacrum and pelvis.
This reduces the amount of work required by the spinal muscles and can eliminate muscle fatigue and back pain.
Functions of the Spine
To achieve these functions, the spine must have:
Resistance to axial loading forces, accomplished by:
Kyphotic and lordotic sagittal plane curves
Increased mass of each vertebra from C1 to the sacrum
Cortical bone : dense, outer shell of the vertebra
Types of Bone Tissue Detail of Cortical Bone Haversian System Detail of Cancellous Bone
Cancellous bone : inner, spongy bone
Vertebral Structures Vertebral Body Pedicle Lamina Superior Articular Process Spinous Process Transverse Process Vertebral Foramen
Vertebral Structures Superior Articular Process Inferior Articular Process Zygapophyseal Joint (Facet Joint) Pars
Slight Notch Deep Notch Intervertebral Foramen
through which the spinal nerve roots leave the spinal cord
Anterior 1/3 of the pedicles
Posterior 2/3 of the pedicles
The Atlas (C1) Transverse Process Transverse Foramen Anterior Tubercle Articular Facet for Dens Lateral Mass Lamina Posterior Tubercle Superior Articular Facet Superior View
The Axis (C2) Odontoid Process (Dens) Body Transverse Process Inferior Articular Facet Superior Articular Facet Anterior View Posterior View Lateral Mass Spinous Process
Lower Cervical Vertebrae
C3 to C7
May be referred to as the subaxial region
Disc at every level
Vertebral structures are similar
Lower Cervical Vertebrae C3 - C7 Transverse Process Body Sulcus for Spinal Nerve Lateral Mass Lamina Pedicle Superior Articular Facet Vertebral Foramen Bifid Spinous Process Transverse Foramen Axial View
Lower Cervical Vertebrae C3 - C7 Sulcus for Spinal Nerve Uncinate Process Uncovertebral Joint (Joint of Luschka) Anterior View The vertebral bodies of the subaxial cervical spine have upward projections on the lateral margins called UNCINATE PROCESSES . These processes articulate with the level above to form the UNCOVERTEBRAL JOINT . These are also called JOINTS OF LUSCHKA .
Vertebra Prominens (C7) Spinous Process Axial View C7 is referred to as the VERTEBRA PROMINENS because it has a longer and larger spinous process than the other cervical vertebrae. This spinous process is not usually bifid.
Body - progressive increase in mass from T1 to T12
Allows compressive, tensile, and rotational motion
Largest avascular structures in the body
Outer portion of the disc
Great tensile strength
Made up of lamellae
Layers of collagen fibers
Arranged obliquely 30°
Reversed contiguous layers
High water content
Resists axial forces
Intervertebral discs have no significant vascular structures.
They receive their blood supply by diffusion through the vertebral body endplates.
A network of vessels located centrally in the endplate allows nutrients to diffuse into the nucleus pulposus and annulus fibrosus.
Occipitocervical Joint Occipital Condyles Foramen Magnum articulate with C1 superior facets
Atlantoaxial Joint C1 C2 Dens Zygapophyseal joints JOINT between the atlas (C1) and the axis (C2); has a range of motion in the transverse plane for rotation. The DENS of C2 acts as a pivot point for the rotation of C1. The articulating surfaces of the two vertebrae form ZYGAPOPHYSEAL (FACET) JOINTS that allow flexion-extension, side bending, and rotational movements.
The Facet Joints Also called ZYGAPOPHYSEAL JOINTS . The facet joints are formed by the articular processes of adjacent vertebrae. The inferior articular process of a vertebra articulates with the superior articular process of the vertebra below. These are synovial gliding joints Facet joints are oriented in different planes depending on their anatomic location.
Uncovertebral Joints Uncovertebral Joint The bony elevations on the superior lateral margins of the cervical vertebrae are called UNCINATE PROCESSES . The uncovertebral joints are not true joints These joints articulate with the inferior, lateral aspect of the vertebra above to form the UNCOVERTEBRAL JOINTS , also known as the JOINTS OF LUSCHKA . These are fibrous joints Uncinate Process
Costovertebral Joints The T2-T9 thoracic vertebra have facets superiorly and inferiorly at the posterior aspect of the vertebral body that form the COSTOVERTEBRAL joints. Costovertebral joints Rib Costotransverse joints Axial View In the thoracic spine, the RIBS articulate with the vertebrae at both the body and the transverse processes. At all thoracic levels there is a facet where the rib articulates with the transverse process. These are called the COSTOTRANSVERSE joints. The T1 and T10-T12 vertebral bodies have only one costal facet. Rib
Sacroiliac Joint Sacroiliac Ligaments Sacrum Ilium The superior lateral surface on either side of the sacrum articulates with the inner aspects of the pelvis. This area forms the capsular, synovial SACROILIAC JOINT . In some cases the sacroiliac joint is a hidden source of back pain .
Extending from the axis (C2) anteriorly to the sacrum.
Is broader at the level of each vertebral body than at the level of the discs where the fibers adhere to the annulus fibrosus.
Attaches to each vertebral body superiorly and inferiorly at the levels of the end plates.
Anterior Longitudinal Ligament (ALL)
Lower Cervical, Thoracic, and Lumbar Ligaments Intertransverse ligaments Costal ligaments The INTERTRANSVERSE LIGAMENTS extend from the inferior surface of the entire length of the transverse process to the superior surface of the adjacent transverse process. The COSTAL LIGAMENTS connect the heads of the ribs to the vertebrae.
Lower Cervical, Thoracic, and Lumbar Ligaments Posterior longitudinal ligament
POSTERIOR LONGITUDINAL LIGAMENT (PLL)
Is weaker than the ALL.
It runs from the axis (C2) caudally to the sacrum.
The PLL is narrow at the levels of the vertebrae, but the fibers extend laterally at the disc levels. These fibers may help to contain herniated disc material.
Like the ALL, the PLL is attached to the vertebra at the superior and inferior margins, and to the annular fibers of the intervertebral disc.
Lower Cervical, Thoracic, and Lumbar Ligaments Interspinous ligament Ligamentum nuchae The INTERSPINOUS LIGAMENT connects each adjacent spinous process. In the cervical spine the interspinous ligament becomes part of the LIGAMENTUM NUCHAE , that extends cranially to insert into the occiput.
The SUPRASPINOUS LIGAMENT is a very strong band connecting the tips of contiguous spinous processes. It extends from C7 to the sacrum.
Lower Cervical, Thoracic, and Lumbar Ligaments Supraspinous ligament Ligamentum nuchae Above C7 these fibers are part of the LIGAMENTUM NUCHAE.
Lower Cervical, Thoracic, and Lumbar Ligaments Ligamentum flavum LIGAMENTUM FLAVUM Also called the YELLOW LIGAMENT Consists of elastic fibers oriented vertically that extend from the anterior inferior surface of the lamina above to the superior posterior surface of the lamina below. The ligamentum flavum tends to thicken as it progresses down the spine, beginning at the axis (C2) and extending to the sacrum.
The ILIOLUMBAR LIGAMENTS extend from the transverse processes of L4 and L5 to the iliac crest.
Lumbosacral Ligaments Anterior View Lumbosacral ligaments The LUMBOSACRAL LIGAMENT is a thick, fibrous band that extends from the anterior, inferior aspect of the transverse process of L5 to the lateral surface of the sacrum.
Sacroiliac Ligaments Short sacroiliac ligaments Posterior View Long sacroiliac ligaments
The SACROILIAC LIGAMENTS are as follows:
short sacroiliac ligaments: composed of horizontal fibers extending from the sacrum to the posterior part of the iliac bone
long sacroiliac ligaments: composed of fibers extending vertically from the sacrum to the posterior superior iliac spine
Posterior Spinal Muscle Groups
The superficial posterior muscles are collectively called the ERECTOR SPINAE , comprising three groups:
Posterior Spinal Muscle Groups
The middle, or intermediate, muscle group of the spine is called the SEMISPINALIS GROUP :
Posterior Spinal Muscle Groups
Intertransversarii attachments between spinous processes
The deep muscle layer consists of the following groups:
Arteries of the Cranial and Cervical Region Foramen lacerum Vertebral artery Carotid artery Two VERTEBRAL ARTERIES , one located on each side the cervical vertebrae. These arteries are branches of the right and left subclavian vs. that exit from aorta. They ascend through the transverse foramen of C6 through C1,entering the skull through the foramen magnum where they join together to form the BASILAR ARTERY. Anterior to the cervical vertebrae are the CAROTID ARTERIES , which ascend through the FORAMEN LACERUM and join with the vertebral arteries to form the CIRCLE OF WILLIS .
Arteries of the Cranial and Cervical Region Vertebral arteries Basilar artery Circle of Willis Internal carotid arteries
Arteries of the Thoracic and Lumbosacral Regions Vertebral artery Aortic arch Ascending aorta Descending aorta Thoracic segmental arteries Abdominal aorta Bifurcation of the aorta Lumbar segmental arteries External iliac artery (left & right) Internal iliac artery (left & right) Femoral artery (left & right)
At each vertebral level from T4 to the sacrum, a pair of SEGMENTAL ARTERIES branches posteriorly from the aorta to supply blood to the vertebral body, posterior elements, spinal cord, and costal structures.
Veins of the Cervical and Thoracic Region The most important venous structures in the cervical spine are the internal and external JUGULAR VEINS . The internal jugular veins follow a path similar to the carotid arteries. They should always be considered during any anterior cervical spine procedure. External jugular Anterior jugular Internal jugular
Veins of the Thoracic and Lumbar Region Internal jugular Superior vena cava Azygos vein Thoracic segmental veins Hemiazygos vein Lumbar segmental veins Inferior vena cava Common iliac veins
Batson’s Plexus The AZYGOS SYSTEM is a large network of veins draining blood from the intestines and other abdominal organs back to the heart. The segmental veins drain into the azygos vein located on the right side of the abdomen, or into the hemiazygos vein located on the left side. The azygos system also communicates with a valveless venous network known as BATSON’S PLEXUS . When the vena cava is partially or totally occluded, Batson’s plexus provides an alternate route for blood return to the heart. The vessels of Batson’s plexus may be referred to as epidural veins Batson’s plexus
Batson’s Plexus Because of the azygos system, patient positioning is very important in posterior lumbar spine surgery. The patient’s abdomen should always hang free and without abdominal pressure. An increase in pressure will diminish flow through the azygos system and the vena cava. This results in an increase of venous flow into Batson’s plexus with a corresponding increase of blood loss . Batson’s plexus
Spinal Nerve Structures
Contained in epidural space
Network of sensory and motor nerves
Firm, cord-like structure
Extends from foramen magnum to L1
Terminates at the conus medularis
The cauda equina begins below L1
Filum terminale extends from conus medularis to the coccyx
Conus medularis Cauda equina
Meninges Dura mater Subdural space Arachnoid layer Subarachnoid space: filled with CSF Pia mater Within the spinal canal, the spinal cord is surrounded by the EPIDURAL SPACE, filled with fatty tissue, veins, and arteries. The fatty tissue acts as a shock absorber. The spinal cord is covered by MENINGES which has three layers.
Spinal Nerve Topography
31 pairs of spinal nerves
Spinal Nerves Spinal cord Epidural space Dura mater and Arachnoid layers Subarachnoid space Dorsal root Ventral root Dorsal root ganglion Peripheral nerve
Autonomic Nervous System Independent of voluntary control. Controls glandular and cardiac function and smooth muscle such as that found in the digestive tract. There are two components: sympathetic parasympathetic The control centers of both systems are located outside the spinal cord in structures called GANGLIA .
Autonomic Nervous System The SYMPATHETIC NERVOUS SYSTEM consists of a series of ganglia extending from the skull to the coccyx, lying on each side of the vertebral bodies. These aligned ganglia look like a chain at each side of the spine and are often referred to as the sympathetic nerve chain. Injury to the sympathetic nerve chain in the lumbar spine may result in genitourinary problems for the patient . Each sympathetic ganglion has fibers that join to the adjacent spinal nerve. The PARASYMPATHETIC NERVOUS SYSTEM has ganglia located close to the organs they control.