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.

39. V-shaped caudal dura

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.

43. SACRAL MENINGOCELE

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.

55. mmohi63@yahoo.com
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