Modern Discography
By Francisco A. Naveira, M.D.
Introduction
ÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝ Five spinal-related pathologies are associated with syndromes involving low-back and leg pain. The five are: facet syndrome; sacroiliac joint syndrome; discogenic syndrome; central spinal stenosis; and foraminal stenosis. All may present with a common symptom complex of low-back, buttock, trochanteric, and posterior thigh pain. Most of them may also be mechanically related to radiculopathies. The spectrum of disc disease includes disc herniation, acquired spinal stenosis, myelopathy, chemical or mechanical radiculopathy, and internal disc derangement. Specific details from history, physical, and radiographic examination may allow separation of these entities, but proof of diagnosis requires data from response to treatment, facet and nerve injection, myelography, discography, nerve conduction testing, and computerized tomography (CT) or Magnetic Resonance scanning.
Discography can be performed at the cervical, thoracic, lumbar, and sacral levels. Although the basic elements of discography are the same at any level, the discogram technique and safety issues will vary with the area tested. The bulk of information available is related to cervical and lumbar discography. Crucial elements, such as Discomanometry, remain better understood at the lumbar level. Cervical, thoracic, and sacral discography should be left for discographers with 5-10 years of experience with the lumbar techniques. For the purpose of this review, we will concentrate only on Lumbar Discography.
True discography consists of several steps or elements, all of which are essential for the interpretation of the study and successful outcomes. These steps or elements must be carefully documented, and include:
1. Preoperative evaluation, which in turn should include
a. VAS at its worse and prior to study
b. Location of pain (may include a pain drawing)
c. Aggravating factors
d. Alleviating factors
e. Duration of pain
f. Onset of pain (Sudden vs. Gradual)
g. Neurological exam
h. Evaluation of prior films or neurological studies (EMG/PNCV)
i. Allergies
2.
Preoperative
laboratories
a.
Coagulation
parameters
b.
ESR
c.
WBC
3. Discogram: actual injection of radiological contrasts into the disc. There are two types:
a. Provocative discogram
b. Analgesic discogram
4. Discomanometry: monitoring and recording of the intradiscal pressures, during crucial events, related to the study.
a. Quantitative vs. simple discomanometry
b. Opening pressure
c. ìPressure sensationî pressure
d. ìPain sensationî pressure
e. Leakage pressure
5. Post-discogram fluoroscopic films
a. A-P
b. Lateral
c. Obliques
d. Cephalocaudad
6.
7.
Interpretation
a. Interpretation of contrast spread:
i.Real-time discogram
ii.Annulogram
iii.Nucleogram
iv.Epidurogram
b.
Intraoperative
vs. Post-discogram pain evaluation: Analgesic vs. Provocative
8.
Decision
making process
The discographer should have ample knowledge of the spinal anatomy, with
emphasis on the neuroanatomy and disc anatomy.
These physicians
should be capable of identifying and managing any complications that may arise
from the procedure. Discograms should not be performed by physicians unwilling
to follow up with the patient, since essential information can be lost or
omitted.
Historical background
ÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝ The
first disc injection was performed in
Some of the controversy started in 1968, when Holt questioned the validity of the pain response to injection. He reported a 37% false-positive rate among asymptomatic prison inmate volunteers[10]. Holtís study, as many others, had several methodological flaws, some of which were pointed out by Simmons in 1988[11]. Some of these flaws included:
ß All of his subjects were prisoners.
ß He used a highly irritating contrast medium.
ß He did not include positive pain response as criteria for positive injection.
ß Criteria for a positive result were based primarily on radiological images.
ß He excluded 23% of injected discs due to technical difficulties in performing the procedure.
ß Performed a significant number of annular injections, known to be very painful.
The idea that discography was most valuable in the evaluation of patients with pain and no definite herniation was reported in a study of a large series of cases evaluated by Wiley et. al., in 1968[12]. In 1970, Henry Crock introduced the concept of an internal disc disruption syndrome with back pain as its primary symptom[13]. It was also around this time that new and safer non-ionic contrast material was developed for myelography[14]. This allowed for these radiological techniques to become safer. The addition of post-discogram CT evaluation in 1984, significantly improved the technique to image the intradiscal architecture[15]. Measurement of intradiscal pressure is not a new concept. As early as 1959, studies such as those by Nachemson have attempted to record intradiscal pressures[16]. By 1975, Nachemson had already established a clear relationship between spine position and loading, to the pressure mechanics of the discs[17].
Over the years, the procedure has
undergone considerable changes to keep up with developing treatment modalities.
It has also been subjected to intense scrutiny and controversy. As new
orthopedic and neurosurgical technology emerges, the discography technique will
also have to evolve to answer yet more questions about the area of pathology.
Advances in the field of disc anatomy, algology, histology, physiology,
chemistry, and pathophysiology, have helped our understanding of this complex
structure. Such new understandings will continue to affect the way discography
is performed and interpreted.
The lumbar disc
Structural Anatomy
Each lumbar
intervertebral disc consists of three basic components: the central nucleus pulposus, the surrounding annulus fibrosus, and the upper and
lower vertebral end-plates.
Microanatomy
Nucleus Pulposus ñ It is a semi-fluid mass with a consistency similar to toothpaste. The mixture of proteoglycans, aggregates, and collagen is collectively referred to as the nuclear matrix. Embryology: It is a remnant of the notochord. Histology:
… Water: 70-90% (Varies with age)[18],[19],[20] The water is mainly contained in the proteoglycans.
… Proteoglycans: 65% of nuclear dry weight. They exist in units or aggregates, with only 25% in the aggregate form18,19.
o The water-binding capacity is mainly dependent on the chondroitin sulphate concentration.[21]
… Collagen: 15-20% of nuclear dry weight, mostly Type II (some Type III)18,[22]
… Cartilage cells: Located close to the end-plates, they are responsible for proteoglycan and collagen synthesis.[23],21
Annulus Fibrosus ñ Consists of 10 to 20 sheets[24] of highly ordered collagen fiber layers that surround the nucleus, called lamellae. They are thicker in the anterior and lateral portion of the annulus, with the posterior portion being thinner[25]. Histology:
… Water: 60-70% of its weight18,19,20.
… Collagen: 50-60% of its dry weight[26],18, mostly Type I.
… Proteoglycans: 20% of its dry weight18. (50-60% are in aggregate form[27])
… Elastic fibers: 10% of its dry weight[28].
Vertebral end-plates ñ Each of the two end-plates is a layer of cartilage 0.6-1 mm thick[29],[30]. Histology:
… Hyaline cartilage: towards vertebral body (mostly found in younger discs).
…
Fibrocartilage: towards the nucleus
pulposus (mostly found in older discs).
Functional Anatomy
Metabolism ñ The disc contains enzymes that synthesize its matrix. It also contains other enzymes such as collagenase, elastase and other proteinases, that break it down[31],[32]. The balance between the degradation and synthesis is controlled by proteinase inhibitors31. Nicotine can inhibit the synthesis of proteoglycans and type II collagen, thereby affecting this balance[33].
Weight-bearing ñ A 40 kg load is accompanied by a 0.5 mm radial expansion and a 1 mm vertical compression of the intervertebral disc.[34] It is the water content of the disc that makes the nucleus a turgid body that resists compression. Therefore, water content is of critical importance to the disc. Because water content is a function of proteoglycan content, anything that affects the proteoglycans will, in turn, affect the other.
Movement ñ These include: distraction, sliding, bending or rocking, and twisting.
Spacer ñ A normal disc maintains the distance between vertebral bodies. Disc degeneration or removal will decrease this distance, thereby causing the cephalo-caudad diameter of the neural foramen to be decreased. This anatomical change may cause significant neural foraminal stenosis and nerve root impingement. This disc degeneration will shift some of the weight-bearing from the anterior (intervertebral discs) to the posterior (zygapophysial / facet joints) elements of the spine. This will, in turn, cause degeneration and hypertrophy of the facet joints, leading to a chronic facet syndrome. Zygapophysial joint hypertrophy causes a decrease in the antero-posterior diameter of the neural foramen. This decrease in diameter will lead to foraminal stenosis and further nerve root impingement.
Creep - Defined as the time dependent
part of the intervertebral disc deformation that accompanies the application of
a load[35].
Blood and Nutrient
Supply
No major arterial branches. The
only vessels that supply the discs are small branches of the metaphysical arteries,
which anastomose over the outer surface of the annulus and supply only the
outermost fibers23. Nutrition is therefore dependent on diffusion
from the vessels in the outer annulus, and from the capillary plexus to the
vertebral end-plates. Although diffusion is the principal mechanism to get
nutrients into the disc[36],[37],
compression of the disc tends to squeeze water out. When this compression is
released, water returns, carrying nutrients with it[38].
Neuroanatomy
Two kinds of innervation are present in the lumbar spine: one depends on the somatic nervous system and the other on the sympathetic nervous system. The sympathetic nerves are the sinu-vertebral nerves and the rami communicantes which innervate the intervertebral disc, the ventral surface of the dura mater, the longitudinal dorsal ligament and the longitudinal ventral ligament. In a healthy intervertebral disc, the outer third of the annulus contains a variety of free and complex nerve endings[39]. Most nerve endings are located in the lateral portions of the disc, with lesser concentrations in the posterior aspect, and the least located in the anterior portion of the disc39,[40],[41]. These nerve endings are supplied by branches of the lumbar ventral rami, the grey rami communicantes, and the lumbar sinuvertebral nerves[42],[43]. Each disc is innervated by the lumbar sinuvertebral nerves at its respective level and from the disc level above. There is no significant difference between endplate and annulus innervation densities. The endplate innervation is concentrated centrally adjoining the nucleus. The richest area of innervation is in the perianular connective tissue[44]. Innervation is as follows:
Lumbar ventral rami ñ Posterolateral corner of each disc.
Grey rami communicantes - Posterolateral corner and lateral aspect of each disc, and the anterior longitudinal ligament. Sympathetic nerves are likely involved in the proprioception of the spinal column[45].
Sinuvertebral nerves ñ Posterior
longitudinal ligament, and most of the disc. This nerve is implicated in
diffuse low back pain because of its pathway and its sympathetic component.
This nerve cannot directly reach a somatic element at each level of the lumbar
spine, so must first reach the L2 spinal ganglion[46]. Discogenic pain is mediated by the
sinu-vertebral nerves, and through the rami communicantes reaches the L2 spinal
ganglion. Anatomical and clinical features reinforce this hypothesis46.
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A transverse section through the vertebral canal and intervertebral foramina to demonstrate the relations of the lumbar nerve roots. The roots are enclosed in their dural sleeve, which is surrounded by epidural fat in the intervertebral foramina. Radicular veins (RV) and radicular arteries (RA) run with the nerve roots. Anteriorly the roots are related to the intervertebral disc and posterior longitudinal ligament (PLL), separated from them by the sinuvertebral nerves (SVN), elements of the anterior internal vertebral venous plexus (AV), and the anterior spinal canal branches (ASCB) of the lumbar arteries (LA). Posteriorly, the roots are separated from the ligamentum flavum (LF) and zygapophysial joints (ZJ) by elements of the posterior internal vertebral venous plexus (PV), and epidural fat, which lodges in the recess between the ligamentum flavum of each side. |
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The nerve supply of a lumbar intervertebral disc depicted in a transverse view of the lumbar spine. Branches of the grey rami communicantes and the sinuvertebral nerves (SVN) are shown entering the disc and the anterior and posterior longitudinal ligaments (ALL, PLL). Branches from the sinuvertebral nerves also supply the anterior aspect of the dural sac and dural sleeve. |
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A sketch of the nerve
supply of the lumbar intervertebral discs outside the vertebral canal.
Laterally, the discs receive branches (1) from the grey rami communicantes of the
sympathetic trunk (ST). Posterolaterally, they receive branches
(2, 3) from the grey rami communicantes and the
ventral rami (VR) as they emerge from the intervertebral
foramina. The anterior longitudinal ligament (ALL) is innervated by
recurrent branches (4) from the grey rami. |
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Innervation of the
lumbar spine. A cross-sectional view incorporating the level of the vertebral
body (VB) and its periosteum (p) on the right and intervertebral
disc (IVD) on the left. PM ñ psoas major. QL ñ quadratus lumborum. |
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The Premise
The premise of discography is that reproduction of patientís
clinical symptoms during the injection identifies the disc as a source of pain.
The rationale
The rationale for its use is that the results can help
discriminate among the various structures that may be responsible for axial
pain.
Validity
MRI has been found to demonstrate an abnormal disk in approximately 22-28% of subjects without back pain or sciatica[47].Ý Other studies have shown 32% of asymptomatic subjects to have ìabnormalî lumbar spines and 47% of all the subjects who had experienced LBP to have ìnormalî lumbar spines[48]. Provocative discography is the only method that directly relates a radiographic image to the patientís pain.Ý A CT/discogram is considered as positive, only if significant pain and an abnormal image are present.Ý When these two portions of the test are taken into account in asymptomatic volunteers, the study results in 100% specificity[49].Ý Discography has been found to be more sensitive than MRI in detecting annular tears[50].Ý CT/discography has an overall accuracy of 87-94%[51].Ý Discography was not found to be sensitive to lesions in the middle or outer annulus that are not contiguous with the nucleus.Ý MRI, when compared to discography, is significantly better in demonstrating posterolateral lumbar disk herniations (100% versus 86%)51,[52].Ý Discography was found to be more sensitive than myelography in detecting lateral disk herniations, especially at the L5-S1 level51,[53].Ý It is recommended that MRI be used initially in the diagnosis of low back pain.Ý In terms of surgical outcome, it has been found that when a patient has both, a positive abnormal discographic image and a painful provocative injection, there is an 88% success rate in terms of a surgery while those patients that displayed a positive image but no symptomatic pain reproduction, the success rate is only 52%[54].Ý CT/discography can identify recurrent disk herniations not visualized by Gadolinium enhanced MRI.
Lumbar
discogenic pain and internal disk disruption are defined as lumbar spine pain
with or without referred pain, stemming from an intervertebral disk, caused by
internal disruption of the normal structural and biochemical integrity of the
symptomatic disk.Ý Discogenic pain occurs
in 39% of patients with severe chronic low back pain in whom the etiology has
not been well defined by less invasive diagnostic testing.
Internal
disk disruption was described as being different from symptomatic disk
herniation.Ý In the syndrome of internal
disk disruption, the primary symptom is back pain. Leg pain might be a
significant part of the problem, but back pain is the dominant complaint.
Provocative discography is required to establish this diagnosis. In symptomatic
disk herniations, the mass effect of herniated disk material compresses
neural elements causing a tissue reaction.Ý
Leg pain is the dominant complaint and is always greater than back pain
in the fully developed radicular syndrome. Ý
The most
commonly abnormal levels are L4-5 and L5-S1 in combination, followed by L5-S1
alone, followed by the combined 3 level degeneration at L3-4, L4-5, and L5-S1.
Indications
1.
The
primary indication for lumbar discography is chronic low-back pain with or
without radicular pain in the absence of MR imaging-documented neural
compression. Patients with persistent, severe back pain in whom other
diagnostic tests have failed to reveal the etiology.
2.
When
clinical findings suggest a level or a side different from that suggested by
diagnostic imaging. (To resolve diagnostic dilemmas.)
3.
Discography
should be performed only if the patient has failed conservative therapy, and
other diagnostic tests have not provided sufficient diagnostic information.
Generally, discography should be viewed as an invasive test to be used to seek
elusive pathology, when results from other tests are equivocal or inconsistent,
in a patient with symptoms severe enough to require surgical management.
4.
Not
indicated or necessary to confirm the unequivocal presence of herniated discs
that coincide with findings on clinical examination.
5.
Further
evaluation of demonstrably abnormal discs to help assess the extent of
pathology and/or correlation of the abnormality with clinical symptoms. Such
may include recurrent pain from a previously operated disc and lateral disc
herniation.
6.
To
determine if the adjacent disks to a proposed fusion segment are symptomatic
and to determine if these segments can tolerate the added stress of a nearby
fusion.
7.
Further
evaluation of abnormal disks or recurrent pain from a previously operated disk
and lateral disk herniation.
8.
Assessment
of failed surgery patients to determine if there is painful pseudoarthrosis or
a symptomatic disc in a posteriorly fused segment.
9.
To
determine if the patient is a candidate for IDET (Intradiscal Radiofrequency
Annuloplasty / Nucleoplasty).
10. Assessment of minimally invasive surgical
candidates confirmed a contained disk herniation or to investigate dye
distribution pattern prior to chemonucleolysis.
Anesthesia
It is recommended that short acting
medications be used, since it is absolutely necessary to have an awake and
responsive patient for questioning about reproduction of pain. If possible,
avoid Bezodiazepines or long acting narcotics that can confuse the interpretation
of the results. Intravenous sedation should be sufficient to keep the patient
comfortable in the required position, but not enough to make the patient
somnolent, disoriented, or uncooperative.
Antibiotic Coverage
…
Intravenous
cefazolin (2 gm) does diffuse into the human disc in detectable concentrations;
and a critical time relationship exists (15-80 minutes after a bolus
administration of cefazolin) for the optimal level of intradiscal antibiotics
to be achieved[55].
…
Prophylactic
role of cefazolin administered at the time of discography. Adding the
antibiotic to the intradiscal suspension or giving it intravenously 30 minutes
before intradiscal inoculation of bacteria prevented any radiographic,
macroscopic or histological signs of discitis; all the intervertebral disc
cultures were negative. The injected contrast contained cefazolin 1 mg per ml[56].
…
Intravenous
cefazolin or vancomycin given within 1 hour before surgery can effectively
prevent postoperative discitis[57].
…
Penicillin
(negatively charged) and gentamicin (positively charged) penetrated the
neutrally charged annulus fibrosus, but penicillin had less ability than
gentamicin to penetrate into the negatively charged nucleus pulposus. Data
suggest that penetration and distribution of antibiotics into avascular
intervertebral disc is significantly influenced by the charge of antibiotics[58].
…
Gentamicin
concentration in the rabbit nucleus pulposus does not peak until 2 hours after
an intravenous bolus of drug. If gentamicin penetrates human nucleus pulposus
in a similar fashion, this study could have implications for the timing of
administration of this agent for prophylaxis[59].
Contrast Material
You should always use a
water-soluble, nonirritating, non-ionic, preservative-free, hypoallergenic
contrast. We currently use Isovue 300M.Ý
An abnormal disk will usually accept two (2) or more ml of fluid
Pain Provocation hypothesis
1.ÝÝÝÝÝ The injection may increase intradiscal pressure which, in an abnormal disk, may stimulate nerve endings within the annular fibers of the disk, possible by stretching them.
2.ÝÝÝÝÝ The injection may result in some biochemical or neurochemical stimulation that causes pain.
3. An injection may increase pressure at the end plates or pressure may be transferred to the vertebral body throughout the end plate resulting in an increase in intravertebral pressure and therefore pain. This hypothesis is supported by studies reporting disk injection resulting in end plate deflection and increased specimen height.
4.
ÝAnother
hypothesis to explain the presence of pain from injection of a seemingly normal
disk is that pressure from the injection is transferred to an abnormal,
symptomatic adjacent disk and, thus, a positive pain response is elicited.
Acute-pain provocation mechanism (At the time of
injection)
…
Acute
Pain evaluation (Provocative Discography)
-
Positive
= pain above or equal to 6/10.
-
Location
of pain must be described. (Back pain, leg pain) Including the side (right,
left, center, bilateral) and the distribution (leg pain down to the bottom of
the foot, etc.)
…
Evidence
- Stimulation of nerve endings in the outer annulus[60],[61],[62]
- Painful endplate disruption[63]
- Increased pressure at the endplates or within the vertebral body[64]
- Increased Substance P and VIP in the dorsal root ganglia[65]
-
Transmission
of mechanical stimulation to the facet joints.
…
Problems
- With chronic pain central sensitization occurs, and dorsal horn activity no longer depends on peripheral tissue injury. A pure stimulus response relationship no longer exists. Both previously innocuous stimuli to the dorsal horn and stimuli from outside the original receptive field cause pain. Therefore, interpretation may be inaccurate.[66],[67]
- Psychological factors may affect results.[68]
-
Disc
tears and leakage may prevent increases in intradiscal pressure, adequate
enough to mimic even standing pressures.
Delayed-pain provocation mechanism (Hours after the
injection)
…
Evidence
-
Mechanism
of irritation and inflammation of neural structures by exposure to nuclear
material.
ß Inflammatory glycoprotein is responsible for chemical radiculitis.[69]
…
Peaks 3
weeks after acute injury to disc.
…
Prolonged
rest may be contraindicated because of the risk of formation of radicular
adhesions.
ß
Phospholipase
A2 (induced by cytokines, among others)[70]
ß
Leukotriene
B4 and Thromboxane B2. (non-contained disc herniations > contained disc
herniations)70
-
Pathophysiological
changes
ß
Tumor
necrosis factor (TNF)[71] (a
cytokine) causes:
…
Thrombus
formation
…
Intraneural
edema
…
Reduction
of nerve conduction velocity
… Dorsal root ganglia compartment syndrome[72]
…
Anti-TNF
include: pentoxifylline, etanercept, and infliximab.
ß
Thromboxane
A2 (TXA2) ñ induces not only potent platelet aggregation, but also blood vessel
contraction.[73]
ß
Leukotriene
B4 (LTB4) ñ a potent chemotactic agent, plays a role in inflammatory reactions
by recruiting neutrophils and lymphocytes.73
…
Problems
- Time delay: After the exposure of the dorsal root ganglia to the nuclear matrix, it may take 2.5 to 6 hours for the spontaneous neural activity to increase.[74]
-
At this
point, nobody is looking at this component of the test. Patients should be
asked to keep a diary about the post-procedure pain.
…
Other
postulated pain mechanisms and hypothesis
Post procedure
hematoma
Complications of discography
…
Post-dural-puncture
headaches (Spinal headaches)
…
Meningitis
…
Discitis
-
0-0.61%
- Incidence based on number of patients injected.
-
0-0.03%
- Incidence based on number of discs injected.
-
1.3-3%
using a single needle technique and 0.35-0.7% using a double needle technique,
and when prophylactic antibiotics are used, the incidence goes further than to
0.000%.
- There is experimental evidence that prophylactic antibiotics, both intravenous and intradiscal, can prevent discitis.[75],[76]
…
Intrathecal
hemorrhage
…
Arachnoiditis
…
Severe
reaction to accidental intradural injection
…
Damage
to the disc itself
ß Followed negative discogram patients for 10-20 years and found no additional abnormalities compared to those initially seen on the negative discogram.[77]
…
Nerve
damage
…
Urticaria
…
Post-injection
disc herniation
…
Retroperitoneal
hemorrhage
…
Nausea
(2%)
…
Convulsions
(4%)
…
Headaches
(10%)
…
Increased
pain (81%)
-
Hematomas
may cause significant pain and spasms.
-
Muscle
and skin transgression may also cause significant pain and spasms.
-
Displacement
and leakage of nuclear material during injection of contrast, may cause
irritation to neural structures, which may require LESI to solve.
-
Pay
attention to this pain and inquire whether or not it is different, similar, or
exactly the type of pain the patient normally experiences. It may help with the
diagnosis of the mechanism of the pain.
-
Consider
giving patients some Klonopin or Valium for spasms.
Recognizing and Treating Discitis:
… Signs and symptoms
- Worsening of pain 3 to 6 weeks after procedure.
- May not present with fever or elevated WBC count.
… Diagnostic Tests
- Check ESR, re-check in 24 hours if equivocal.
- Blood culture, direct aspirate / biopsy.
- Rule out other sources.
- MRI with and without contrast. (Gadolinium).
- Bone Scan
- WBC nuclear scan
… Treatment
- 6 to 8 weeks of IV antibiotics.
-
Discectomy.
Clinical Symptoms
Interestingly, there are some studies to clinically evaluate discogenic pain by using a "bony vibration stimulation".Ý An attempt should be made to determine whether or not the patient can feel pain by placing a tuning fork over the spinous processes. The main symptoms are:
1.
Internal disk
disruption - The primary symptom is
back pain.
2.ÝÝÝÝÝ Symptomatic
disk herniations - Leg pain is the dominant complaint and is always
greater than back pain in the fully developed radicular syndrome.
Procedure
Prophylactic antibiotics and/or antihistamines should be considered.Ý A double needle technique should always be used.Ý The injection should be performed with contrast as previously described.Ý (Water soluble, etc.). Accurate needle placement is required to avoid annular injections, which could produce false positive results. Injection against the vertebral end plate can also cause false positive response.
ÝPressure from the discography injection could
be transferred to an adjacent abnormal, symptomatic disk and thus, a positive
pain response could be elicited. Due to this, it is always a good idea to monitor
the pressure of the adjacent disks as contrast material is being injected and
the end point pressure tested.
The information recorded should include:
1.
The resistance to the injection.
(End-point)
2.
The amount of contrast injected.
(Maximum Volume)
3.
The volume at which the patient experienced pain.
(Pain Volume)
4.
The pattern of dye distribution.
(Diffuse, location of fissure, extravasation, herniations, Schmorl's node etc.).
5.
Pressure at which patient experienced a
"pressure sensation".
6.
Pressure at which the patient experienced
"Pain".
7. The pain response. (Location, character, distribution, intensity, and concordance or discordance with the patient's typical pain and pain pattern)
8.
Pain intensity is recorded on a 0-10 scale
Interpretation
Very careful attention should be paid to interpreting the pain response during the injection of each disk, including if the pain is similar to or exactly like the symptoms for which the patient seeks relief.Ý The location of the pain, and its intensity.Ý Discography should then be followed by actual CT scanning.
Pain at low pressures is most likely due to chemical irritation. .Ý Low resistance is generally associated with a tear throughout the outer annulus Pain at high pressures is possibly due to mechanical irritation, end-plate deflection, or stimulation of pressure receptors.
An intradiscal pressure of 60-70 pounds per square inch (400-500 kilopascals) is the maximum pressure that can be sustained by manual injection technique (thumb pressure on a 3.0 cc luer-lock syringe).Ý The normal intradiscal pressure of a supine patient is approximately 15-25 PSI.Ý Sitting or standing increases this normal pressure to approximately 80 PSI.
Generally, if a large volume of
contrast can be injected, the disc is degenerated or there is a fissure
extending through the outer annular wall.Ý
Injection pressure or resistance to injection should be noted.
Imaging Diagnosis of Lumbar Discs[78]:
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CT classification of Discography[79]:
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Type 1 the discogram is normal manometrically, volume metrically, radiographically, and produced no pain.Ý The CT discogram showed contrast to be centrally located in the axial and sagittal projections. |
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Type
2 is identical to type 1 except that
it is positive for reproduction of pain. Ý |
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Type
3 the annular tears lead to a radial
fissure.Ý This group is further
subdivided into Type 3a when the radial fissure is posterior, 3b when it
radiates posterolateral, and 3c when the fissure extends lateral to a line
drawn from the center of the disk tangential to the lateral border of the superior
articulating process. |
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Type 4 once the radial fissure reaches the periphery of the annulus fibrosus, nuclear material may protrude causing the outer annulus to bulge |
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Type
5 when the outer annular fibers
rupture, nuclear material may extrude beneath the posterior longitudinal
ligament and come in direct contact with either the dura or a nerve root. Ý |
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Type
6 when the extruded fragment is no
longer in continuity with the interspace it is said to beÝ sequestrated.Ý Manometrically, volumetrically, and
radiographically, the discograms are always abnormal.Ý Familiar pain may only be reproduced if
enough pressure is generated against the free fragment to cause stimulation
of the pain sensitive structures. Ý |
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Type 7 the end stage of this degeneration is internal disk disruption, in which multiple annular tears occur.Ý The discograms are abnormal manometrically, volumetrically, and familiar pain may or may not be reproduced.ÝÝ Radiographically, the contrast usually fills the entire interspace in a chaotic fashion.Ý The CT discograms show contrast extravasation throughout multiple annular tears. |
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Clinical classification:
1. No pain or pressure. (NP)
2. Pressure (P)
3. Pain dissimilar to clinical symptoms. (D)
4. Pain similar to clinical symptoms. (S) (Inconsistent)
5. Exact reproduction of symptoms. (ER) (Concordant)
6. Pain
intensity is recorded on a 0-10 scale
Contrast distribution[80]: (as
evaluated by Fluoroscopy )
|
Discogram Type |
Stage of Disk Degeneration |
|
ìCotton Ballî (CB) |
No
signs of degeneration, Soft white amorphous nucleus |
|
ìLobularî (L) |
Mature
disk with nucleus starting to degenerate into fibrous lumps. |
|
ìIrregularî (I) |
Degenerated
disk with fissures and clefts in the nucleus and inner annulus. |
|
ìFissuredî (F) |
Degenerated
disk with radio fissure leading to the outer edge of the annulus. |
|
ìRupturedî (R) |
Disk
has a complete radio fissure that allows injected fluid to escape.Ý Can be in any stage of degeneration. |
|
|
ìCotton Ballî |
|
|
|
|
ìLobularî |
|
|
|
|
|
ìIrregularî |
|
|
|
|
|
ìFissuredî |
|
|
|
|
|
ìRupturedî |
|
|
|
Discomanometry
ÝÝÝÝÝÝÝÝÝÝÝÝÝÝÝ Simple discomanometry is the manual
injection of fluid into the nucleus pulposus with continuous recording of the pressure
as a function of time. Quantitative
discomanometry is the automated injection of fluid at a constant flow rate,
recording both, the volume and pressure, as a function of time.
Interpretation:
1. Low resistance is generally associated with a tear throughout the outer annulus.
2. Pain at high pressures is possibly due to mechanical irritation, end-plate deflection, or stimulation of pressure receptors.
3. Intradiscal pressure of 60-70 pounds per square inch (PSI) is the maximum pressure that can be sustained by manual injection technique (thumb pressure on a 3.0 cc luer-lock syringe.)
4. Generally, if a large volume of contrast can be injected, the disc is degenerated or there is a fissure extending through the outer annular wall.
5. In general, degeneration of the intervertebral disc will cause a decrease in the mean intradiscal pressures.
6. Opening or intrinsic pressure is defined as the pressure at which the contrast starts to enter a disc.
7. Leakage pressure is defined as the pressure on the P-V curve, where a sudden change occurs in the curve inclination, whereby the volume increased substantially, while the pressure either stopped increasing, or changed minimally.
8. Chemical irritation is defined as pain at or below 15 PSI above opening pressure.
9. Mechanical irritation is defined as pain between 15 and 50 PSI above opening pressure.
10. Indeterminate discs are defined as having pain between 51 and 90 PSI above opening pressure.
11. Normal disc have no pain.
12. Annular disruption ñ leaking / protrusion / annular fissuring
13.
Kpa x 0.14504 = PSI
|
Intradiscal Pressure
Values for Different Positions and Exercises |
|
Position
|
Pressure
(PSI) |
|
Lying supine |
15 |
|
Lying on the side |
17 |
|
Lying prone |
16 |
|
Lying prone, extended back,
supporting on elbows |
36 |
|
Laughing heartily, lying laterally |
22 |
|
Sneezing, lying laterally |
55 |
|
Peaks by turning around |
102-116 |
|
Standing,
relaxed |
73 |
|
Standing, performing valsalva
maneuver |
133 |
|
Standing, bent forward |
160 |
|
Sitting relaxed, without backrest |
67 |
|
Sitting actively
straightening the back |
80 |
|
Sitting with maximum flexion |
120 |
|
Sitting bent forward with tight
supporting the elbows |
62 |
|
Sitting slouched into the chair |
39 |
|
Standing up from a chair |
160 |
|
Walking barefoot |
77-94 |
|
Walking with tennis shoes |
77-94 |
|
Jogging with hard street shoes |
51-138 |
|
Jogging with tennis shoes |
51-123 |
|
Climbing stairs, one at a time |
73-102 |
|
Climbing stairs, two at a time |
44-174 |
|
Walking down stairs, one stair at
a time |
55-87 |
|
Walking down stairs, two stairs at
a time |
44-131 |
|
Lifting 20Kg, bent over with round
back |
334 |
|
Lifting 20Kg, as taught in back
school |
247 |
|
Holding 20Kg close to the body |
160 |
|
Holding 20Kg, 60cm away from the
chest |
261 |
|
Pressure increase during night
(over a period of 7 hr.) |
15-36 |
Reference:
ìNew In Vivo Measurements of
Pressures in the Intervertebral Disc in Daily Lifeî Wilke et al. Spine Vol.24,
No 8, pp755-762, 1999.
|
Level |
Average Volume (ml) |
Volume Range (ml) |
|
L2-3 |
0.58 |
0.4
- 0.7 |
|
L3-4 |
1.06 |
0.4
- 2.6 |
|
L4-5 |
1.09 |
0.22
- 2.4 |
|
L5-S1 |
0.99 |
0.42
- 2.0 |
|
Transition |
0.40 |
NA |
|
Discogram Type |
Mean Injection Pressure (PSI) |
Mean Injection Volume (mL) |
|
1 |
34 |
0.62 |
|
2 |
28 |
0.71 |
|
3 |
26 |
1.20 |
|
4 |
17 |
1.54 |
|
5 |
19 |
More
than 2.0 |
Disk Classification
|
Intradiscal
Pressure |
Pain Response
Intensity |
Pain Response Category |
|
0-normal |
>80
PSI |
0 |
NA |
|
1-asymptomatic |
>50
PSI |
Pressure, discomfort
only |
NA |
|
1-asymptomatic |
>50
PSI |
Definite pain
(>5/10) |
Discordant |
|
2-indeterminate |
<50
PSI |
Definite pain
(>5/10) |
Discordant |
|
3-mechanical (strain) |
30-50
PSI |
Definite pain
(>5/10) |
Discordant |
|
4-chemical (sensitized) |
<30
PSI |
>5/10 |
Concordant |
Appendix A ñ Guidelines
Statement of purpose:
To provide
guidelines to assist the Pain Physician with the performance of a discogram
(discography).ÝÝ This is a diagnostic
procedure used to determine the extent of involvement of a vertebral disc as a
cause of the patientís pain.
Policy:
The following are Guidelines.
Exceptions to these guidelines are up to the discretion of each physician, and
shall be based on that physicianís evaluation of the case in question.
Only the trained pain
physician should do this and all pain blocks. The procedure will be done under
fluoroscopy. May be done in same day surgery facilities, or in clinic
facilities, if fluoroscopy and a sterile environment are available.
Equipment:
-
ìCrash
cartî must be available in the facility.
-
(2) two
10cc, luer-lock syringes
-
(1) one 3cc,
luer-lock syringe
-
25-G,
1.5-in, needle (1)
-
18-G
needle (1)
-
18-G,
3-inch, Quincke spinal needle (one per level to be done) (usually 3-4)
-
22-G,
7-inch, Quincke spinal needle (one per level to be done) (usually 3-4)
-
(1) one
pressure manometer syringe (The kind used in angioplasties)Ý ìBasix”î 25 Inflation Syringe Catalog No. IN3125
(Merit Medical 1-801-253-1600 or 1-800-356-3748) or s similar pressure-gauged
(manometer) 20-60 ml syringe (Merit Medical Digital Fluid Syringe KO5-L1-L5)
-
(2) two
10cc bottles of contrast, water-soluble, non-ionic, hypoallergenic,
myelogram-compatible dye/contrast. (20 ml)
Either Isovue 200M or 300M, or Omnipaque 180. If patient is allergic to
contrast, follow the ìProtocol for patients with Allergies to Radiological
Contrastî.
-
Betadine
prep or some other form of skin prep.
(Alcohol or Hibiclens)
-
Prep tray
-
(4) four
sterile towels
-
(1) pack
of sterile 4x4
-
(1-4) one
to four Band-Aids
-
Prophylactic
antibiotics (as ordered by physician): Gentamicin 120mg and Ancef 1gm IV, prior
to procedure. Vancomycin 1gm IV, if allergic to penicillin.
-
Fluoroscopy
machine (C-Arm)
-
Fluoroscopy
table (Chic table)
-
Sedation
(as ordered by physician): Versed (Midazolam) 2-4mg, Fentanyl 2cc and/or
propofol.
Medication:
-
Cipro’ (ciprofloxacin) 500 mg PO BID 24 hr prior to
procedure and 5 days after.
-
Rocephin’ (ceftriaxone) 1-2gm. IV before the procedure
-
Another
alternative is Ancef’ or Kefzol’ (cefazolin)
1-2gm. IV, before procedure.
-
Gentamicin
(Garamycin’) 100-200 mg IV
-
(1) one 20-30cc
bottle of 2% lidocaine
-
If the
patient is allergic to Penicillin, give Vancomycin 1gm. IV slowly before the
procedure.
-
Ancef’ or Kefzol’ (cefazolin) 5 mg/kg to mix with contrast, only if patient is not allergic to
penicillin.
Procedure:
1. Schedule patient in Special Procedure area.
2. Ascertain and document that the patient has a
driver, has not eaten 6 hours prior to procedure, and is not taking any blood
thinners.
3. Confirm that the patient is not taking any
blood thinners like Coumadin. If taking Coumadin, it most be stopped, with the
consent of the prescribing physician, at least four (4) days prior to
procedure.Ý ASA and ASA-containing
medications should be stopped eleven (11) days prior to the procedure.
4. Patient's Pain Clinic chart should be
available at Special Procedures.
5. Ascertain and document that female patients
are not pregnant. (Question patients about possibility)
6. The physician will review the procedure,
including the risks and possible complications, and answer any questions that
the patient or family may have, in the visit prior to the procedure day.
7. Have patient or guardian sign informed consent
form.
8. Obtain baseline vital signs, which should
include: BP, HR, RR, Temp, SaO2, and NAS-11(VAS).
9. Start an IV.
10. Place patient in position. Position:
prone for lumbar or thoracic disc and supine for cervical disc.
11. Prep: For lumbar disks, prep from the sacrum to the lower border of the
scapula. For cervical, prep from the mandible to the collarbone (clavicle).
Always prep wide.
12. The following laboratory should be ordered and
drawn prior to the procedure, if requested by physician: CBC (WBC and platelet
count), Sedimentation rate, bleeding time, PT/PTT, INR (as felt to be necessary
by physician), and pregnancy test for females in childbearing years. The procedure
should never be delayed waiting for these results, except for the pregnancy
test. Ideally they should have been drawn days prior to procedure.
13. A C-Arm will be required for fluoroscopy.
14. Schedule for IV sedation using Versed and
Fentanyl IV sedation.
15. Prophylactic antibiotics (as felt necessary by
physician).
Gentamycin 120 mg IV before the procedure.
Ancef and Kefzol 1-2gm. IV, before procedure.
(Except if allergic to penicillin)
16. If patient is not allergic to penicillin, mix 1gm
of powdered cefazolin (Ancef) in 10 ml of Omnipaque 180. This will give you a
concentration of 100mg/ml. Take 3 ml of this solution and mix it up to a total
volume of 20 ml of Omnipaque 180, in the Merit Medical Digital Fluid Syringe.
This will lead to a final concentration of 15 mg/ml.
17. If the patient is allergic to Penicillin, give
Vancomycin 1gm. IV slowly before the procedure.
18. Sedate the patient (as ordered by physician).
Maintain meaningful verbal contact at all times.
19. Assist physician as needed.
20. At completion of the procedure, have patient
return to supine position.
21. Discard contaminated needles and equipment.
22. Document in procedure form:
a. Name of procedure, physician, indications, date, and place where performed
(Hospital, Office)
b. Vitals signs every 15 minutes
c. Post-procedure NAS-11
d. Patientís Status after procedure (Patient tolerance)
e. Any untoward effects or complications
Ýf. Intradiscal pressures
g. Injected volume
h. Pain provocation and distribution pattern
i. End point
j. Morphologic distribution of radiological contrast
23. Observe patient for 10-15 minutes post
procedure.
24. Arrange with Radiology to have the patient
taken to the CT scanner immediately after the discogram injection, and then
back to Special Procedures Recovery for discharge, once the patient has met
discharge criteria.
25. Arrange for follow up appointment at the pain
center in 1-2 weeks.
26. If the patient continues to have significant
pain after the discogram, then schedule the patient for an evaluation and
possible epidural steroid injection, upon return to the pain clinic.
If the patient
develops pain and fever, then order a sed rate and CBC. If abnormal, consider
ordering a Bone Scan to rule out discitis.
Appendix B ñ Pressure
Manometry Syringe
25 ATM Inflation Devices
|
|
|
|
|
UNITED STATES |
Appendix C ñ Libman Test[81],[82],[83],[84]
Theory:
This test is designed to examine the
patient's tolerance to pain, as an individual.
Procedure:
The test consist of the following maneuver:
using the thumb of your right hand, pressure is placed for a few seconds over
the anterior portion of the mastoid process towards the area of the
styloid.Ý This maneuver will put pressure
over a portion of the greater auricular nerve.Ý
According to the degree of pain produced by this maneuver, the patient
will be classified in one of three categories Libman type 1 (hyposensitive),
Libman Type 2 (sensitive), or Libman Type 3 (hypersensitive).Ý The response is based on the facial and/or
verbal response of the subject to the question "what do you feel when I do
this?"Ý The following is a
description of each one of the expected reactions. Ý
Libman Type 1 (hyposensitive): These are the patients who experience no
pain.Ý Therefore as a consequence of this
you will see no facial expression resembling that of pain, and they might
vocalize that they are having no pain at all.Ý
It is believed that 20% of the population belongs to this group.Ý This is variable and depends on race (in the
Indian population up to 80% might be part of this group), and profession (70%
of boxers).
Libman Type 2 (sensitive): The patients in this group will experience
some pain but they will not manifest any facial expressions with it.Ý It is assumed that 40-50% of the population
will be part of this group.
Libman Type 3 (hypersensitive): These are the patients who will not only
complain of pain by vocalizing it but they will also express a facial grimace
compatible with pain.Ý This group
accounts for approximately 30-40% of the total population.Ý This is also influenced by the area where the
patient resides (with up to 80% of the urban population being part of this
group), as well as level of education (with up to 90% of the
"educated" patients being part of this group), etc. (Patients that
scream during local anesthetic infiltration of the skin.)
References