Anatomic basis of epiduroscopy
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This document discusses the anatomical basis of epiduroscopy, beginning with the structures of the sacral canal. It notes that the sacral hiatus and sacral canal exhibit wide anatomical variations that must be understood to perform epiduroscopy safely. Key landmarks for locating the hiatus are described, along with measurements of the hiatus, canal, and dural termination. Variations that can cause procedural difficulties are highlighted. The contents and compartments of the epidural space are outlined, along with age-related changes. Guidelines for selecting epiduroscopy equipment based on anatomical limitations are provided. Pathological changes like fibrosis are also described.
Anatomic basis of epiduroscopy
- 1. Anatomic basis of Epiduroscopy Mohamed Mohi Eldin Professor of Neurosurgery, Cairo University, Egypt 9th TURKMISS ISTANBUL, 08-10 April, 2016 Elmer Jose A. Meceda Fellow Academy of Filipino Neurosurgeons Good Doctor Teun Teun Hospital, Korea
- 2. The sacral canal Passage for MI diagnostic and therapeutic caudal procedures (Epiduroscopy)
- 3. Wide Anatomic Variations Procedures may be difficult or impossible To perform successful procedures Detailed anatomical variations must be thoroughly understood
- 4. Be careful where we place needles, catheters, instruments ! Entry into sacral canal should be safe
- 5. In most, the laminae of S4 - S5 do not fuse for the formation of the sacral hiatus Fused S1, S2, and S3 lamina Sacral Hiatus
- 6. Sacral hiatus • Triangular in shape • Termination of sacral canal • Covered by – Skin – Subcutaneous fat – Sacrococcygeal membrane
- 7. For successive Epiduroscopy 1. The sacral hiatus should be located 2. Equipment inserted in the hiatus 3. Equipment advanced along the sacral canal
- 8. Locating Sacral Hiatus (A constant challenge) Surrounding bony landmarks are usually taken into consideration
- 9. The Posterior Iliac Spines • Generally cross S2
- 10. Equilateral triangle For locating the hiatus formed by Intercrestal line (at level of S1 foramen) apex of hiatus
- 11. Equilateral triangle Equilateral in 45% Sides of triangle much shorter than base in 55% (apex of hiatus quite variable)
- 13. Median Sacral Crest cannot be ignored for locating hiatus in the absence of other bony landmarks. In 3.5% cases, crest is absent and cannot be considered as a landmark.
- 14. Distance between lower end of Median crest and apex of SH It ranged from 2.0 mm – 2.6 cm (average 12.35 mm) Most commonly (49%) 1 - 2 cm
- 15. Sacral cornua Covered by subcutaneous adipose tissue, it can only be palpated if of suitable size Bilaterally absent about 3% Bilaterally short about 7-21%
- 16. Intercornual distance Variable from 2.2–28 mm (average 10.2-17.5) About 21% less than 10 mm. This means that in 79% it is sufficient
- 17. Length of Sacral Hiatus Range from 4.30 to 69 mm Shorter than 10 mm in 12%
- 19. Causes of failures of caudal procedures (according to anatomical analysis) Bony abnormalities such as Absent hiatus (0.3%) Agenesis (1%) Bony septum (2.5%)
- 20. Absence of Sacral Hiatus Found in 0.3 - 7 %
- 21. Bony septum in the middle of the sacral canal (2.5 %) May lead to failure of the procedure
- 22. Shape of Sacral Hiatus Most common types (71%) provide enough room for introducing needle
- 23. Other less common Shapes (29%)
- 24. Variations in dorsal wall of sacral canal
- 25. Bony projection in lateral wall of hiatus (7 %) Explain occasional difficulty
- 26. Level of apex of Sacral Hiatus Against S4 in about 65% S2 in about 2.5% High apex = more precaution = short instruments Low apex = longer instruments
- 27. Distance between apex of SH and S2 (Mean mid-sagittal distance 7-40 mm) Thus, Needle should not be introduced more than 7 mm into sacral canal once the pop is felt
- 28. Shape of the sacral canal Sacral Canal ends in the sacral hiatus in combination with Sacrococcygeal ligament
- 30. Anteroposterior diameter at apex of Sacral Hiatus Needs to be sufficient to admit needle into sacral canal Ranged from 1.5 - 14 mm Less than 3 mm (8.7%) it is difficult to insert needle
- 31. Curvature of sacrum Both are not limiting factor for equipment manipulation
- 32. The Lumbosacral angle Consequences • The ‘Floating’ catheter in short, dorsal and blunt T-end. • The ‘Blocked’ catheter in long taper T-end with large L5 -S1 Disc
- 33. Maximum Curvature of sacrum (one of the important parameters ) At level of S2 in 25% At level of S3 in 60% At level of S4 in 15%
- 34. The level of maximum curvature of sacrum influence the angulation of needle insertion at S3 and at S4
- 35. Epidural Space Only a potential space not uniform in distribution kept open either by epiduroscope or by repeated injections of air or saline
- 36. Actual Epidural Space Dural sac ends between S1 and S3
- 37. Location of Dural (Thecal) end (T-end) The S1 and S2 vertebral bodies divided into 3 locations The most common location of the T-end were at S1C and S2A.
- 38. Shape of the T-end There were 2 types of shape Taper and Blunt.
- 40. Orientation of the T-end 3 types Dorsal, Neutral and Ventral
- 41. T- end Shape consequence a blunt shaped T-end will be more difficult to negotiate compared to a tapering T-end. It appears that it may be easier to puncture the dura in blunt shape T-end
- 42. Paramedian approach Pass a greater distance before contact with the dura mater Demonstrate a low risk of accidental dural puncture.
- 44. Contents of the Sacral Canal 1. Ventral Epidural Space (VES) 2. Filum terminale 3. Sacral and coccygeal nerves (the cauda equina) 4. Dorsal Epidural Space (Dorsomedian connective tissue band)
- 45. Baston venous plexus Sacral epidural veins ending at S4, but may extend throughout the canal They are at risk from catheter or needle puncture
- 46. Ventral Epidural Space (VES) The working compartment for Epiduroscopy A potential space can be distended or dilated with saline solution
- 47. Ventral Epidural Space (VES) contains loose areolar fat, meningovertebral ligament, epidural plexus of veins, lymphatics and sinuvertebral nerves.
- 48. Meningo-vertebral ligaments Separate VES into compartments of different sizes and shapes, some as fine as silk, some as thick as pasta, some even forming a sagittal septum, distributed as cobweb-like may contribute to catheter placement failure, catheter knotting within the epidural space
- 49. Age induced changes of the epidural space Fat tissue diminishes Intervertebral foramina size diminishes AP diameter of SH diminishes AP diameter of sacral canal decrease
- 50. Outer diameter of equipment according to anatomical limitations Smallest flexible fiber optic endoscope (0.9 mm) Video Guided Catheter (2.65 - 2.8 mm) These can be easily used in 85-95% of the cases.
- 51. Anatomy of Pathological Sacral Canal (Fibrous scarring) Area identified by • lack of agent diffusion • filling defects • direct vision after – canal distension with fluid – clearing with the Fogarty Pathological findings • scarring • connective strands • Hyperemia • inflammation
- 52. Two types of fibrosis Type I Mild fibrosis with transverse filmy strands. Type II Fibrotic adhesions with widespread septa and partial or total reduction of canal caliber
- 53. Fibrosis: Anatomical Appearance • Transparent Cotton-candy-like (80–75%) loosely adhered to dura • Organized fibrous structures of hard consistency adherent to the dura, intrinsic vascularization • Fibroid bridles with multiple cords (often foraminal) with inflammatory sites • Blind compartmentalization of the ES
- 54. Pathologic fibrous elements and hyperemic tissues • At S1 level in 80% of patients • At S3–S4 level in 5% of patients and is the reason for suspension of the procedure.