Radiofrequency in Spine Practice : introductory concerns

1. Radiofrequency in Spine Practice
(Rhizolysis)
Introductory Concerns
Mohamed M. Mohi Eldin,
Professor of Neurosurgery,
Faculty of Medicine,
Cairo University
One-Day Spine Clinic 2nd workshop & hands-on
20-21 April 2016

2. Orientation Check..
Where is this needle ?!

3. Where is this needle ?!

4. Where is this needle ?!

5. Other Names
Radiofrequency Thermocoagulation
Radiofrequency Denervation
Radiofrequency Lesioning
Radiofrequency Neurotomy
Radiofrequency Ablation
Rhizolysis

6. Different Clinical Assessment
The unseen FACET joints
The forgotten SACROILIAC joint
Which level claimed in multilevel affection
False normal MRIs

7. Different Radiological Assessment

8. Neurosurgical Patient: Case Scenarios
Radiofrequency (RF)
part of the case scenarios

9. RF

10. GENERAL PRINCIPLES !!
Ready to answer all questions
Provide the patient with a clear explanation of
the risks and benefits

11. Written Consent
Honesty first

12. A form of Electrosurgery
RF thermocoagulation
Alternating current of
high frequency radio waves
passes from the electrode tip
within body tissue and
dissipates its energy as heat

13. Potential Mechanisms of
Pain Relief by Heating
Heating nerve tissue at 45 degrees Centigrade
causes irreversible neural blockade
Change the structure of the collagen fibers,
causing an increase in stability

14. RF Thermocoagulation
Indicated for pain
with constant and limited distribution
Interrupts nociceptive pathways in the treatment of chronic pain
Useful for nociceptive pain and some neuropathic pain
Diagnosis confirmed with diagnostic blocks first
Tendency for recurrence 1-2 years but can be repeated

15. Non-indications
Central pain
Spinal cord pathology
Serious Psychopathology

16. Diagnostic Injections
Diagnostic blocks are usually done before RFA
Blocks should usually be repeated
Due to false positive results (38%)
Diagnosis requires radiographically guided blocks provide
complete relief and are validated by a appropriate control test
that exclude false-positive responses

17. RF cannula
18‐gauge, 100 mm long
10 mm curved sharp tip

18. What is Radiofrequency Lesioning?
The use of high frequency electric current to
produce controlled thermocoagulation
(heat lesion)
Reduce symptoms for longer than
injection with local anaesthetic and steroid.

19. Radiofrequency Neurotomy
is a minimally invasive outpatient procedure
Aims at nerves of joints and not joints themselves
Nerves supplying affected joints stop transmitting pain
"shut off" the transmission of pain signals

20. Radiofrequency Ablation
• Therapeutic procedure
• Teflon-coated electrode
with an exposed tip is
inserted onto the target
nerve.
• High frequency
electrical current is
concentrated around
the exposed tip.
• The nerve is heated and
coagulated.

21. Radiofrequency
• Brief history of RF
• Physics of RF
• Clinical applications
• Guidelines
• Evidence for efficacy
21

22. 1931 Until 1980
large size probes (14-gauge)
1931 - Gasserian ganglion thermo-lesion,
1975 - RF lesioning of the medial branch for lumbar
facets (Shealy),
1977 - RF lesion of dorsal root ganglion (Uematsu),
cordotomies.

23. 1980 – 1995
Introduction of fine probes
medial branch (facet joints),
dorsal root ganglion,
sympathetic chain,
1991 - nucleus of the disc

24. 1996 to present
Era of research and evidence
Pulsed RF,
Cooled RF,
Development of computerized generators

25. 25
• Brief history of RF
• Physics of RF / Pulsed RF
• Clinical applications
• Guidelines
• Evidence for efficacy

26. Alternating Current and RF
AC frequency (f) is the number of cycles per
second (measured in Hz)
Household outlet has AC
60 Hz or 50 Hz
Radiofrequency Generator
460 kHz = 460,000 Hz
A microwave
500-1000 kHz

27. Principle of RF lesion
Involves passage of very high frequency current
(300 kHz) through 27 G thermocouple probe
High frequency alternating current
To & fro movements of charged ions
Electro-mechanical friction
Generation of heat due to this

28. stylet
Exposed tip = 5 mm
RF electrode

29. RF Current
Low energy, high frequency
(100,000-500,000 hz)
Cells become damaged at
42 to 45 degrees celsius.
RF lesions do not selectively destroy only nociceptive
afferents

30. RF Current
Electrical stimulation at 50 hz should sensory
stimulation at less than 1 V if electrode is
placed correctly.
Stimulation at 2 hz should evoke contraction of
ipsilateral paraspinal muscles below 2.5 V but
without limb contracture.

31. Ionic Heating Using RF Cannula
• RF energy is applied
• An electric field is established
around the electrode tip.
• Field oscillates with alternating RF
current causing movement of ions
in the tissue
• Ions move creating friction
• Friction heats surrounding tissue
• Hot tissue heats probe or electrode
by conduction
• Probe thermocouple located at the
tip, reads tissue temperature
Insulated
Introducer
Noninsulated
Tip

32. RF versus Electrocautery
The primary source of heat
is the tissue around the electrode tip,
rather than the electrode tip itself ,

33. Lesion characteristics
• Temperature
• Rate of thermal
equilibrium
• Local Tissue
characteristics-Impedance
• Radius of Electrode tip
and Configuration

34. Lesion Temperature
(determines size of lesion)
Temperature drops as radius
from tip increases
Neurodestruction occurs
when temp reaches > 45ºC
A small zone of reversible
damage surrounds lesion
With temperature of 60-100 there is induction of protein
coagulation, leading to cell death

35. Indications of Conventional RF
Cervical facet joint denervation Sacroiliac Joint denervation

36. Conventional RF
Lumber facet joint denervation

37. Conventional RF
Sensory testing:
0.4-0.6 V at 50 Hz
Motor testing:
1-2 V at 2 Hz
Lesion is carried at
80 -85 degree C for 60 – 90 sec.

38. Lesion size versus Lesion Time
CW: 20V, t= 0 sec
37˚C
40˚C
45˚C
60˚C
55˚C
50˚C
67˚C

39. CW: 20V, t=10 sec
37˚C
40˚C
45˚C
60˚C
55˚C
50˚C
67˚C

40. CW: 20V, t=20 sec
37˚C
40˚C
45˚C
60˚C
55˚C
50˚C
67˚C

41. CW: 20V, t=30 sec
37˚C
40˚C
45˚C
60˚C
55˚C
50˚C
67˚C

42. CW: 20V, t=40 sec
37˚C
40˚C
45˚C
60˚C
55˚C
50˚C
67˚C

43. CW: 20V, t=50 sec
37˚C
40˚C
45˚C
60˚C
55˚C
50˚C
67˚C

44. CW: 20V, t=60 sec
37˚C
40˚C
45˚C
60˚C
55˚C
50˚C
67˚C

45. CW: 20V, t=60 sec
50˚C Isotherm
37˚C
40˚C
45˚C
60˚C
55˚C
50˚C
67˚C |E|=2,750 V/m
|E|=17,000 V/m

46. Is Radiofrequency Ablation Safe?
Monitoring the catheter tip temp
adequately measures tissue temp
Proven to be safe and effective
Generally well-tolerated
with very few complications

47. RF Machine Includes 5
Temperature display
Impedance Monitor: Detecting entry into various mediums
Sensory Stimulation: confirms proximity to the target
Motor stimulation confirms a safe distance to motor fibers
Lesioning Module: continuous vs pulsed RF

48. Impedance
Proximity of electrode
To CSF present low impedance
pathway
To large blood vessel can
deviate the energy
(nonuniform impedance)
To bone can cause
discontinuity of heat due to
lower conductivity
A large increase for example
might suggest movement
from fluid to tissue

49. Neuropathic Pain is a contraindication
for Standard RF
Standard RF Pulsed RF
80 degrees C for 90 seconds 42 degrees for 120 seconds

50. In pulsed RF, the treatment effect is produced by
the electromagnetic field
It is not a thermal lesion.
Pulsed RF can treat peripheral nerves without
injuring them
Pulsed RF maximizes voltage whilst ensuring
that temperature does not exceed 42
Pulsed RF
50

51. Pulsed-RFA
Current is applied in
bursts of 20 ms with a silent time of 480 ms
Lower temp in pulsed-RFA
results in less tissue destruction
Unclear Mechanism of pulsed RFA:
- modulates pain processing mechanisms
-selectively disrupts small nerve fibers

52. Pulsed- RFA versus Standard RF
Shorter benefit of pain relief
(4 months compared to 12 months for RF)
Standard RF denervates surrounding muscle
eliminates the muscular component of pain
e.g. in lumbar facet syndrome

53. Conventional vs. Pulsed RF
• Heat producing lesion.
• Temp can go up-to 85
degree C
• nerves regenerated in
future
• Average pain-free period
up to (3-4) years
• Electrical field is producing
lesion.
• Temp. is not raised beyond 42
degree C
• nerve is repaired
• Average pain free period is 4-
24 months
In pulsed RF. Electrical field produces some punch in
the capacitor of small diameter nociceptive fibers.
Thereby signal transmission is stopped.

54. Indication of Pulse RF
• Stellate Ganglion
• Other Ganglion
• Brachial Plexopathy
• Suprascapular
• AS ROMANS’ DO
• Knee Neuropathic Pain
Stellate Ganglion RF

55. Cervical DRG lesioning

56. Lumber DRG lesioning

57. Lumber DRG lesioning

58. Lumber sympathetic block

59. Cooled RF
Advanced technology
For conditions difficult to treat with conventional RF
Utilizes a special radiofrequency probe
designed to produce a larger lesion size
therefore treat a larger area than with conventional RF

60. Cooled RF

61. Conventional RF
(Mono- or bipolar tip)
• more ovoid-shaped
• Heat localizes around the
electrode tip.
Cooled RF
(Bipolar tip)
• more spherical lesion
• The cooling of the active
bipolar tip will yield a larger
lesion
• increase lesion size by
affecting lesioning time,
temperature, fluid injection,
electrode tip site and spacing.
• With higher power delivery,
the neuroablative RF effect
occurs at a further distance
from the electrode tip.

62. Physics of Cooled RF

63. Physics of Cooled RF Lesions
Non-cooled
Cooled
Temperature
Distance
80° C
45° C
r
• Without cooling, the size of lesion is limited by the heat generated in
the tissue adjacent to the electrode
• Cooling the tissue adjacent to the electrode allows effective heating at
a greater distance

64. Physics of Cooled RF
Internal cooling and a
small active tip size
act to project the
lesion distally in a
controlled manner
Uniform lesions can
be produced in non-
homogeneous
tissue (e.g. grooves,
ligaments, fascia)
Standard 18G cannula
18 g cooled probe

65. Cooled RF
Larger lesions increase the probability of
capturing the nerve in the “sphere” of tissues
ablated.
Larger distal lesion projections, advantageous
when approaching the targeted nerve in a
conventional perpendicular approach.
Allow improved results, even if probes placed
imprecisely.

66. Cooled Radiofrequency Denervation
Procedures include
sacroiliac joint denervation
denervation of the facets joints
Isotherm Map Cooled RF and Standard RF
3.5 mm
10 mm

67. 67
• Brief history of RF
• Physics of RF
• Clinical applications
• Guidelines
• Evidence for efficacy

68. Clinical implications
Localization of the Target nerve
• Fluoroscopic guidance is mandatory
• Check impedance for the integrity of the
circuit (between 200 to 700)
• Sensory-Motor Dissociation
– Sensory stimulation at X
– No motor stimulation at 2X

69. Clinical implications
Confirmation of electrode placement !!!
• The use of preliminary electrical stimulation of
the medial branch nerve to verify electrode
placement is debatable.
– Sensory:- tightness, pressure or tingling
– Motor:- some throbbing
• Argue that adjusting the electrode position to
minimize the threshold for evoked activity
does not improve outcome

70. Clinical implications
Size matters !!!
• Larger cannula = larger area of lesion.

71. Probe orientation !!!
(Conventional RF)
If electrodes placed perpendicularly to nerve
may fail to or will coagulate the nerve minimally
The most reliable coagulation is done if the electrodes
are placed parallel to the nerve.

72. Lesion and heat
(Conventional RF)
Electrical field generation
and movement of
charged particles is
maximum at tip and
minimum around shaft.
Therefore
Heat lesion is maximum
around the shaft and
minimum at tip

73. Perpendicular & Oblique Placement
(Cooled RF)
Spherical lesion shape allows for
perpendicular or oblique probe
placement near the treatment site.

74. Clinical implications
Temperature !!!
Temperature between 45 and 80oC.

75. Clinical implications
Time of lesioning !!!
• Time of lesioning: not less then 60 seconds
but not more then 90 seconds.
• When the probe is in the correct place, RF
current is carried out for 65 seconds.
• Some argue its an unnecessary use of time

76. Clinical implications
Tissue impedance !!!
Tissue impedance:
(between 200 to 700)
high in dense tissues
low in liquids (blood, CSF, disc)

77. Anticipating Complications
RFA near bone or scar tissue may have a very irregular ablation
pattern from differences in impedance and conductivity
leading to complications. Pulsed RFA is more ideal in these
situations and less likely to lead to complications
Patients with pacemakers: cardiology consultation is needed to
convert the pacemaker to a fixed rate for the procedure
Patients with spinal cord stimulators:
adjustments are also needed with the settings (monopolar
needs to be changed to bipolar and off)

78. Clinical implications
After lesioning !!!
Local anaesthetic and steroid are injected after the
probe has been removed to relieve discomfort
following the procedure.
A dressing is applied to the injection site
Rest for several days
No driving for 3 days

79. Clinical implications
Repeat RFAs !!!
Frequency of success and durations of relief
remained consistent after each subsequent
radiofrequency ablation.
Mean duration of 10.5 months and successful
more than 85% of the time
This 10.5 months however, is shorter than
reported 1st time RFA relief

80. To Keep In Mind
Poor technique, producing poor outcomes
RFA significantly improves the pain and quality
of life in patients
However, it does not cure the (source) of pain.

81. Clinical implications
Complications
• Common
– Soreness / bruising at the injection site
– Temporary increase of pain (up to 10 days)
• Rare
– Headache
– Haematoma
– Infection at the injection site
– Allergic reaction
– New pain
– Worsening pain
• Very rare
– Convulsions (fits)
– Temporary or permanent disabling nerve damage
– Cardiac arrest (stopping of the heart)
• Due to the injected steroid:-
– Facial flushing for a few days
– Temporary alteration of usual menstrual cycle (females)
– Temporary increase in your sugar levels (diabetics).

82. 82
• Brief history of RF
• Physics of RF
• Clinical applications
• Guidelines
• Evidence for efficacy

83. Sedation
Feedback from patient during procedure is desirable
Reassurance and adequate local anesthesia usually
suffice
IF sedation required,
intravenous cannulation is necessary
Should be light and short acting

84. Making the Lesion
Adhere to local guidelines MI procedures
The surgical environment
Sterile technique and preparation

85. Anticoagulation
RF denervation considered a high-risk procedure for
bleeding
Benefits and risks should be considered on an
individual basis
Advice on withdrawal of anticoagulants should be
sought from other clinicians involved
This is important as abrupt withdrawal of
anticoagulants may risk serious thrombotic
episodes whereas the continued use carries an
increased risk of bleeding

86. Great deal of CAUTION
Patients requiring anticoagulation medication or with a known
bleeding diathesis
Avoid if
Prothrombin time (prolonged)
activated partial thromboplastin time
international normalized ratio (INR >1.2)
platelet level count (<100 000/ml)

87. Radiofrequency heat lesion
High success rate
Significantly reduces pain severity and frequency
for up to 1-2 years in 50% of patients
Low complication rate
Unfortunately the nerve can regenerate so pain
may come back
A repeat procedure is likely to be beneficial if
good response to the first.

88. RF versus Injections
Good response to diagnostic injections means RF offers
a realistic chance of good long term pain relief
Benefit may not be apparent before 2–3 weeks
Significant and longer lasting pain relief

89. RF versus Surgery
Pain relief for up to 2 years
Low complication and morbidity rates
Appreciable pain relief (FBS in about 50%)
Greater range of motion
Lower use of analgesics
Improved quality of life
Short recovery time

90. 90
• Brief history of RF
• Physics of RF
• Clinical applications
• Guidelines
• Evidence for efficacy

91. Randomized Controlled Trials
very limited
Very few RCT for Pulsed RF neurotomy
The indicated level of evidence for therapeutic facet joint
interventions is Level II- 1 or II-2 for facet joint nerve blocks,
Level II-2 or II-3 evidence for radiofrequency neurotomy

92. Conclusion
RFA is a useful minimally invasive option for
offering long-term pain relief, improving
quality of life in a significant proportion of
chronic pain patients.
Careful patient selection & thorough
knowledge about the proposed procedure
are mandatory

93. Thank You