1) The lumbar spine is more open to ultrasound examination compared to the thoracic spine due to its anatomy. Key structures like the transverse processes and laminae can be reliably visualized. 2) There are three basic ultrasound probe orientations for lumbar spine sonography - parasagittal, parasagittal oblique, and transverse - each providing different views of spinal structures. 3) Parasagittal views provide visualization of the transverse processes, articular processes, and laminar structures. The parasagittal oblique view additionally shows the posterior and anterior spinal complexes. 4) The transverse view with the spinous process casts an acoustic shadow but can show the articular processes and transverse processes when

1. LUMBAR SPINE SONOANATOMY
B. Ashrafnejad MD
Fellowship in Pain Medicine

2. INTRODUCTION

3. Spinal column
• As a rule, deep structures or spaces in the spine may
only be reliably visualised ultrasonographically if
“acoustic windows” are present (or created!) and
used properly.
• Reliable visualisation of lumbar spine sonography is
closely associated with BMI and/or individually highly
different tissue properties that markedly influence
echogenicity

4. Lumbar Spine Anatomy

5. Compared to the thoracic spine
Lumbar spine anatomy reveals that this part of
the spine is more “open” to US examination

6. Transveres Process
“Transverse processes” (TP) are
regularly slim and long, pointing lateral
in essence.
The dorsal surface of TP face strictly posterior.
TPs are situated anterior to APs

7. Lumbar spine transverse process
• A rudimentary (very short and slender) TP is of
practical relevance, most frequently seen at L4.
• the lower margin reaches at least to the level of the
intervertebral disc (in projection).
• The dorsal border is thickened, often revealing an
extension at its caudal end
• The massiveness of its TP in L5

8. laminae
• The width of L1–L4 laminae is much less than of
vertebral bodies.
• Therefore, a considerable part of vertebral bodies and
dorsal aspects of intervertebral discs are seen in a
dorsal view.
• The laminae, do not overlap, and there is a distinct
interlaminar space

9. laminae
• A clear waist, all LAM are narrowest between
superior and inferior AP, at the so-called
interarticular part.
• This waist indicates the level and position of
lumbar dorsal root ganglia, DRG.

10. laminae
• The Laminae faces :
• posteriorly from L1 to L3
• posteriorly and slightly upwards in L4
• L5 Laminae looks more upwards

11. lumbar zygapophysial joints (LZJ)
• Inferior AP Are principally convex & Facing
laterally
• Superior AP are concave & facing medially
• This is why joint gaps are best seen in a
posterior view.

12. Spinous Process
The spinous processes are massive, rectangular
and sagittally orientated.

13. Lumbar Spine Anatomy
AP : articular process
open arrow heads : mamillary process
at superior AP and accessory processes
at root of costal process
SP : spinous process
black arrows point :zygapophysial
joints, LZJ
white ones :vertebral body
black arrowheads : waists of LAM

14. (a)Lateral view of Lumbar Spine and sacrum
(b) Postero-lateral view of Lumbar Spine
SP :spinous process.
AP: superior and inferior articular
process of L3 with “interarticular portion”
(asterisk) in between.
black arrows :transverse processes.
Black open arrow : joint gap of
LSJ (those of LZJ not visible!)
AS: articular surface

15. SONOANATOMY

16. Important Remind
Bony surfaces appear as hyperechoic (white) linear
structures
Dense acoustic shadowing (black) beneath that
completely obscures any deeper structures.

17. Connective tissue structures, such as ligaments
and fascial membranes, also are hyperechoic
wich acoustic impedance is less than bone,
so
deeper structures can still be imaged.
LF

18. Fat and fluid have very low acoustic
impedance
and are hypoechoic (dark).

19. preparation
• Position of choice: lateral decubitus or sitting
position (prone)
• Probe of choice: curved-array, low-frequency
(2–5 MHz) probe for wide field of view and
deeper penetration
• 2 basic planes: sagittal, transverse

21. There are three basic orientations of
the ultrasound probe and beam
• (1) Paramedian sagittal (PS), when the beam is
oriented in the sagittal plane of the spine lateral to
the median (midline) sagittal plane
• (2) Paramedian sagittal oblique (PS oblique), similar
to the PS plane except that the beam is now tilted
and aimed toward the median sagittal plane
• (3) Transverse, when the beam is orientated parallel
to the transverse or horizontal plane.

22. paramedian sagittal

23. paramedian sagittal oblique

24. Transverse

25. Ultrasound Scanning
Starting laterally in the
walk off medially over
until at midline
are reached.

26. Paramedian Sagital View
1

27. Transverse process view
• Place probe in a PS orientation 3–4 cm from
the midline.
• Transverse Process View

28. Transverse process view

29. Transverse process view
• Trident sign, represented by the finger-like
acoustic shadows of the transverse processes

30. Slide the probe medially toward the midline while maintaining
a PS orientation.
Arthicular process view

31. Articular Pricess ViewArthicular process view

32. • Rounded “humps” of the facet joints between
superior and inferior articular processes
Arthicular process view

33. Parmedian Sagital Laminar View

34. Parmedian Sagital Laminar View
• “Horse Head”/ “Sawtooth”
• The hyperechoic bone is not continuous, due to the interlaminar space.
• This space allows visualization of the posterior and anterior complexes.

35. Paramedian sagittal sonogram of the
L5/S1 interlaminar space

36. Paramedian sagittal sonogram of the
articular process of the facet joints

37. Paramedian sagital oblique view
2

38. Paramedian sagital oblique view
• Having obtained the PS articular process view, tilt the probe toward the
midline to obtain the PS oblique view.
• Additional small sliding and tilting movements of the probe may be
required to optimize the view.

39. Paramedian sagital oblique view
•“Sawtooth” appearance of the laminae
•Posterior complex (ligamentum flavum, epidural space and
posterior dura)
•Anterior complex (anterior dura, posterior longitudinal
ligament, vertebral body)

40. • Paramedian oblique sagittal sonogram of the lumbar spine at the L3/4 and L4/5
level.
• Note the hypoechoic epidural space (few millimeters wide) between the hyperechoic
ligamentum flavum and the posterior dura.
• The intrathecal space is the anechoic space between the posterior dura and the
anterior complex in the sonogram.
• The cauda equina nerve fibers are also seen as hyperechoic, longitudinal structures
within the thecal sac

41. Transverse View
4

42. Transverse Spinous Process View
• Rotate the probe 90 degrees into a transverse orientation and
slide it cephalad or caudad as required to obtain transverse
interlaminar views of the desired interspaces.
• The probe may have to be tilted in a cephalad direction to
optimize the view.

43. Transverse Spinous Process View
• A distinct midline shadow is cast by the spinous process
• Note the lamina are visible.
• But the anterior and posterior complexes are obscured

44. Transverse Spinous Process View
• L4 (SP) spinous process and L4 lamina (LM) are completely shadowing the L4
vertebral body (VB).
• Intrathecal space and the transverse process are not visible at this view.
• Exiting L4 nerve root is seen on the left (pin arrow).

45. Transverse sonogram of the lumbar
spine
Note the acoustic shadow of the spinous process which completely
obscures the spinal canal and the neuraxial structures.

46. Transverse Interlaminar view

47. Transverse Interlaminar view
“Flying Bat”
• The articular processes/facet joints (ADFJ) and transverse
process (TP) are visible.
• Tilting the probe will highlight the posterior and anterior
complexes (PC / AC)

48. Transverse Interlaminar view
• hypoechoic L5/S1 interspinous ligament (ISL)
• L5/S1 zygapophysial joints (curved arrows)
• the intrathecal space (IT)
• the S1 superior articular process (SAP)
• the sacral ala (SA)
• the iliac crest (IC).