Anatomy of spine for spinal anaesthesia

spinal anaesthesia

1. ANATOMY OF VERTEBRAL COLUMN, SPINAL CORD, EPIDURAL AND SUBARACHNOID SPACE ZIKRULLAH

2. INTRODUCTION The bony vertebral column provides Structural support Protection of the spinal cord and nerves Provides Mobility

3. The Vertebral Column 33 vertebrae 7 Cervical 12 Thoracic 5 Lumbar 5 Sacral (fused) 4 Coccygeal (usually )

4. Cervical Vertebrae (C 1 – C 7 ) First cervical vertebrae(C 1 ) = Atlas(BODY ABSENT) The 1 st cervical vertebrae has unique articulations that allow it to articulate to the base of the skull and the 2 nd cervical vertebrae. Second cervical vertebrae (C 2 ) = Axis Vertebrae C 3 - C 6 are similar Transverse foramina in each cervical vertebra C 7 has the vertebra prominens

5. Thoracic Vertebrae (T 1 - T 12 ) T1 – T12 Larger than cervical vertebrae Large Spinous Processes Articulations for ribs are present

6. Lumbar Vertebrae (L 1 - L 5 ) L1-L5 Massive block-like body Long hatchet shaped spinous process bulkiest

7. Sacrum (5 fused) Coccyx (3-5 fused) Sacral vertebrae are fused into one bone. In most individuals the lamina portion of S4 and S5 do not fuse. This allows for the formation of the sacral hiatus. This ‘anatomical fact’ becomes important for the administration of caudal anesthesia.

8. Individual Vertebrae Anatomy

9. Each vertebra consists of a pedicle, transverse process, superior and inferior articular processes, and a spinous process. Each vertebra is connected to the next by intervertebral discs. There are 2 superior and inferior articular processes (synovial joints) on each vertebra that allows for articulation. Pedicles contain a notch superiorly and inferiorly to allow the spinal nerve root to exit the vertebral column.

10. Vertebral Anatomy- Side View Superior Articular Process Spinous Process Inferior Articular Process

11. Vertebral Anatomy- Top View Spinous Process Lamina Transverse Process Vertebral Body Spinal Canal

12. Intervertebral Foramina Spinal Nerve Root s The intervertebral discs make up one fourth of the spinal column's length. There are no discs between the Atlas (C1), Axis (C2), and Coccyx. Discs are not vascular and therefore depend on the end plates for diffusion of needed nutrients. Each pair of spinal nerves passes through a pair of intervertebral foramina located between two successive vertebrae Intervertebral Disc

13. The Bony Boundaries of the Spinal Canal Posterior Boundary: Spinous Process and Laminae Anterior Boundary: Vertebral Body Lateral Boundary: Transverse process, pedicle

14. Angle of Transverse Process and Size of Interlaminar Spaces

15. Thoracic Vertebrae Lumbar Vertebrae Angle of transverse process will affect how the needle is orientated for epidural anesthesia or analgesia. With flexion the spinous process in the lumbar region is almost horizontal. In the thoracic region the spinous process is angled in a slight caudal angle.

16. Interlaminar spaces are larger in the lower lumbar region. If an anesthesia provider finds it challenging at one level , moving down one level may provide a larger space. INTERLAMINAR SPACES L 2 L 5

17. Ligaments that support the vertebral column Ventral side: Anterior and posterior longitudinal ligaments Dorsal side : Important since these are the structures our needle will pass through!

18. Ligaments pierced during spinal anaesthesia Dorsal ligaments transversed during neuraxial blockade. With experience the anesthesia provider will be able to identify anatomical structures by “feel”.

19. It is posterior to the epidural space Extends from the foramen magnum to the sacral hiatus It is not one continuous ligament but composed of right and left ligamenta flava which meet in the middle Ligamentum Flavum

20. May or may not be fused in the middle Varies in respect to thickness, distance to dura , skin to surface distance, and varies with the area of the vertebral canal Ligamentum Flavum

21. Site Skin to ligament (cm) Thickness (mm) Cervical - 1.5 -3.0 Thoracic - 3.0 – 5.0 Lumbar 3.0 – 8.0 5.0 – 6.0 Caudal variable 2.0 – 6.0 Characteristics of ligamentum flavum

22. Lamina and spinous processes Interspinous ligament Supraspinous ligament which extends from the occipital protuberance to the coccyx and functions to join the vertebral spines together Posterior to the Ligamentum Flavum

23. Anatomical Considerations of the Spinal Cord

24. Spinal Cord Extends from foramen magnum to second lumbar vertebra Segmented Cervical Thoracic Lumbar Sacral Gives rise to 31 pairs of spinal nerves Not uniform in diameter throughout length

25. There are 31 segments in the spinal cord: 8 cervical (C1 - C8) 12 Thoracic (T1 - T12) 5 Lumbar (L1 - L5) 5 Sacral (S1 - S5) 1 Coccygeal General Organization

26. The spinal cord is located within the vertebral column General Organization

27. Each cord segment has a corresponding vertebra of the same name (e.g., C3). Spinal nerves enter/exit underneath their corresponding vertebral segment. General Organization

28. General organization The spinal cord is with two enlargements-cervical and lumbar The cervical enlargement supplies nerves to the pectoral girdle and upper limbs The lumbar enlargement supplies nerves to the pelvis and lower limbs. Cervical enlargement C5 - T1 Lumbar enlargement L2 - S3

29. Termination of Spinal Cord In adults usually ends at L1. Infants L3 There are anatomical deformity For most adults it is generally safe to place a spinal needle below L2 unless there is a known anatomic variation. Be careful where you place your needle!

30. Anterior and posterior nerve roots join each other and exit intervertebral foramina forming spinal nerves from C1-S5. At the Cervical level- nerve root a rises above the foramina resulting in 8 cervical spinal nerves but only 7 cervical vertebrae. At the Thoracic level- exit below the foramina. At the Lumbar level - form cauda equina and course down the spinal canal. Dural sheath covers the nerve roots for a small distance after they exit. Spinal Nerve Roots

31. Vary in size and structure from patient to patient Dorsal (posterior) roots are responsible for somatic and visceral sensation. Anterior (ventral) roots are responsible for motor and autonomic outflow. Dorsal roots (sensory), though larger, are blocked easier due to a large surface area being exposed to local anesthetic solution Spinal Nerve Roots

32. Dorsal and Ventral roots Dorsal root Ventral root Spinal nerve

33. Blood Supply to the Spinal Cord Anterior Spinal Artery Posterior Spinal Artery A single anterior spinal artery. Formed by the vertebral artery at the base of the skull. It supplies 2/3rds of the anterior spinal cord. Paired posterior arteries Formed by posterior cerebellar arteries and travel down the dorsal surface of the spinal cord just medial to the dorsal nerve roots. They supply 1/3 rd of the posterior cord. Additional blood flow is received by the anterior and posterior spinal arteries from the intercostal and lumbar arteries.

34. Blood Supply to Spinal Cord

35. Artery of Adamkiewicz Radicular artery arising from the aorta. It is large and unilateral ( found on the left side ). It supplies the lower anterior 2/3rds of the spinal cord. Injury results in anterior spinal artery syndrome.

36. Surrounding Membranes

37. Membranes that surround the spinal cord Dura Mater Outer most layer & fibrous Ends at approx S2, where it fuses with filum terminale Arachnoid Middle layer & non-vascular Have principal anatomic barrier for drugs Pia Mater Inner most layer & vascular Also give rise to Dentate ligament 38

38. An extension of the pia mater to the spinal cord that attaches to the periosteum of the coccyx. Filum Terminale

39. Epidural Space Anatomy

40. Potential space between the ligamentum flavum and duramater Extends from the formen magnum to the sacral hiatus It is segmented and not uniform in distribution The epidural space surrounds the dura mater anteriorly , laterally, and most importantly to us posteriorly . Epidural Space

41. Epidural Anatomy Safest point of entry is midline lumbar Spread of epidural anaesthesia parallels spinal anaesthesia Widest at Level L2 (5-6mm) Narrowest at Level C5 (1-1.5mm) 43

42. Cranially – foramen magnum Caudally – sacrococcygeal ligament covering the sacral hiatus Anterior - posterior longitudinal ligament Posterior- ligamentum flavum & lamina Lateral - pedicles and intervertebral ligaments The Boundaries of Epidural Space

43. Fat Areolar tissue Nerves Lymphatics Blood vessels including the Bateson’s venous plexus { valveless veins} Contents

44. With age, the adipose tissue in the epidural space decreases as does the intervertebral foramina size. A dorsomedian band in the midline of the epidural space, presence of septa, presence of a midline epidural fat pad may be associated with unilateral anaesthesia with epidural block .

45. Anatomy of subarachnoid space

46. Space between the arachnoid mater and piamater Contents: CSF Spinal nerve roots Trabecular network Blood vessels Sub Arachnoid space

47. It is in direct communication with the Brain Stem via the foramen magnum. Terminate in the conus medullaris at the sacral hiatus. In effect the subarachnoid space extends from the cerebral ventricles down to S2.

48. Cerebral Spinal Fluid (CSF)

49. Clear fluid ( 99% water ) that fills the subarachnoid space Provides mechanical and immunological protection to Brain, Spinal cord and Thecal sac Total volume in adults is 120-160 ml Volume found in the subarachnoid space is 25-35 ml Produced at a rate of 600 ml per 24 hour period & replacing itself 3-4 times( aprox 6hr) CSF

50. Reabsorbed into the blood stream by arachnoid villi and granulations Specific gravity is between 1.003-1.008 (this will play a crucial role in the baracity of local anesthetic that one chooses) CSF conti ……

51. Palpation of Spinous Process Generally are palpable to help identify the midline

52. In the cervical and lumbar areas the spinous processes are nearly horizontal so with flexion we would only need to angle the needle slightly cephalad Spinous Processes If unable to palpate the spinous process one can look at the upper crease of the buttocks and line up the midline as long as there is no scoliosis or other deformities of the spine

53. In the thoracic area the spinous processes are slanted in a caudal direction and so we need to angle the needle more cephalad Spinous Processes….

54. C2 is the first palpable vertebrae C7 is the most prominent cervical vertebrae With the patients arms at the side the inferior angle of the scapula generally corresponds with T7 Locating prominent cervical and thoracic vertebrae

55. Knowing these landmarks it is important for the administration of thoracic epidurals It is helpful to counts up and down to help ensure we are placing the thoracic epidural in the appropriate area for postoperative analgesia Importance of these Landmarks

56. A line drawn between the highest points of both iliac crests will yield either the body of L4 or the L4-L5 interspace . Tuffier’s Line

57. Anatomical variations Abnormal conditions (tethered cord) Inaccurate vertebral level assessment Cephalad angulation of the needle Performing a dural puncture at an high vertebral level Spinal cord damage :causes

58. Spinal flexion confers NO protection against spinal cord damage when performing a spinal anesthesia (especially at higher levels) THANK YOU