Spine

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Chapter 14 Spine

Methods of imaging the spine

Many of the earlier imaging methods are now only of historical interest (e.g. conventional tomography, epidurography, epidural venography):

1. Plain films. These are widely available, but with low sensitivity. They are of questionable value in chronic back pain because of the prevalence of degenerative changes in both symptomatic and asymptomatic individuals of all ages beyond the second decade. They are, however, useful in suspected spinal injury, spinal deformity and post-operative assessment.

2. Myelography/radiculography. This is used when MRI is contraindicated or unacceptable to the patient. It is usually followed by CT for detailed assessment of abnormalities (CT myelography).

3. Discography. Advocates still regard it as the only technique able to verify the presence and source of discogenic pain.

4. Facet joint arthrography. Facet joint pain origin can be confirmed if it is abolished after diagnostic injection of local anaesthetic, and treated by steroid instillation. The radiological appearances of the arthrogram are not helpful for the most part except in showing a communication with a synovial cyst. Vertical and contralateral facet joint communications can arise in the presence of pars interarticularis defects.

5. Arteriography. This is used for further study of vascular malformations shown by other methods, usually MRI, and for assessment for potential embolotherapy. It is not appropriate for the primary diagnosis of spinal vascular malformations. It may be used for pre-operative embolization of vascular vertebral tumours (e.g. renal metastasis).

6. Radionuclide imaging. This is largely performed for suspected vertebral metastases and to exclude an occult painful bone lesion (e.g. osteoid osteoma) using a technetium scintigraphic agent, for which it is a sensitive and cost-effective technique.

7. Computed tomography (CT). CT provides optimal detail of vertebral structures and is particularly useful in spinal trauma, spondylolysis, vertebral tumours, spinal deformity and post-operative states, especially if multidetector CT (MDCT) is available.

8. Magnetic resonance imaging (MRI). This is the preferred technique for virtually all spinal pathology. It is the only technique that directly images the spinal cord and nerve roots. MRI with intravenous (i.v.) gadolinium-DTPA is indicated in spinal infection, tumours and post-operative assessment.

9. Ultrasound (US). Is of use as an intra-operative method, and has uses in the infant spine.

IMAGING APPROACH TO BACK PAIN AND SCIATICA

There are a variety of ways to image the spine, many of which are expensive. The role of the radiologist is to ensure that diagnostic algorithms are selected for diagnostic accuracy, clinical relevance and cost-effectiveness. Each diagnostic imaging procedure has a different degree of sensitivity and specificity when applied to a particular diagnostic problem. A combination of imaging techniques can be used in a complementary way to enhance diagnostic accuracy. The appropriate use of the available methods of investigating the spine is essential, requiring a sensible sequence and timing of the procedures to ensure cost-effectiveness, maximal diagnostic accuracy and clinical effectiveness with minimum discomfort to the patient.

The philosophy underlying the management of low back pain and sciatica encompasses the following fundamental points:

1. Radiological investigation is essential if surgery is proposed.

2. Radiological findings should be compatible with the clinical picture before surgery can be advised.

3. It is vital for the surgeon and radiologist to identify those patients who will and who will not benefit from surgery.

4. In those patients judged to be in need of surgical intervention, success is very dependent on precise identification of the site, nature and extent of disease by the radiologist.

5. The demonstration of degenerative disease of the spine by non-invasive methods cannot be assumed to be the cause of the patient’s symptoms, as similar changes are often seen in asymptomatic individuals.

The need for radiological investigation of the lumbosacral spine is based on the results of a thorough clinical examination. A useful and basic preliminary step, which will avoid unnecessary investigations, is to determine whether the predominant symptom is back pain or leg pain. Leg pain extending to the foot is indicative of nerve root compression and imaging needs to be directed towards the demonstration of a compressive lesion, typically disc prolapse. This is most commonly seen at the L4/5 or L5/S1 levels (90–95%), and MRI should be employed as the primary mode of imaging. If the predominant symptom is back pain with or without proximal lower limb radiation, then invasive techniques may be required, including discography and facet joint arthrography. The presence of degenerative disc and facet disease demonstrated by plain films, CT or MRI has no direct correlation with the incidence of clinical symptomatology. The annulus fibrosus of the intervertebral disc and the facet joints are richly innervated, and only direct injection can assess them as a potential pain source. However, unless there are therapeutic implications there is no indication to go to these lengths, as many patients can be managed by physiotherapy and mild analgesics.

CONVENTIONAL RADIOGRAPHY

Routine radiographic evaluation at the initial assessment of a patient with acute low back pain does not usually provide clinically useful information. Eighty-five per cent of such patients will return to work within 2 months having received only conservative therapy, indicating the potential for non-contributory imaging. Despite the known limitations of radiographs, it is often helpful to obtain routine radiographs of the lumbar spine before another investigation is requested. The role of conventional radiographs can be summarized in the following points:

1. They assist in the diagnosis of conditions that can mimic mechanical or discogenic pain, e.g. infection, spondylolysis, ankylosing spondylitis and bone tumours, though in most circumstances ^{99 m}Tc scintigraphy, CT and MRI are more sensitive.

2. They serve as a technical aid to survey the vertebral column and spinal canal prior to myelography, CT or MRI, particularly in the sense of providing basic anatomical data regarding segmentation. Failure to do this may lead to errors in interpreting correctly the vertebral level of abnormalities prior to surgery.

3. Correlation of CT or MRI data with radiographic appearances is often helpful in interpretation.

COMPUTED TOMOGRAPHY AND MAGNETIC RESONANCE IMAGING OF THE SPINE

CT and MRI have replaced myelography as the primary method for investigating suspected disc prolapse. High-quality axial imaging by CT is an accurate means of demonstrating disc herniation, but in practice many studies are less than optimal due to obesity, scoliosis and beam-hardening effects due to dense bone sclerosis. For these reasons, and because of better contrast resolution, MRI is the preferred technique and CT is only employed when MRI cannot be used. MRI alone has the capacity to show the morphology of the intervertebral disc, and can show ageing changes, typically dehydration, in the nucleus pulposus. It provides sagittal sections, which have major advantages for the demonstration of the spinal cord and cauda equina, vertebral alignment, stenosis of the spinal canal, and for showing the neural foramina. Far lateral disc herniation cannot be shown by myelography, but is readily demonstrated by CT or MRI. CT may be preferred to MRI where there is a suspected spinal injury, in the assessment of primary spinal tumours of bony origin, and in the study of spondylolysis and Paget’s disease. MRI in spinal stenosis provides all the required information showing all the relevant levels on a single image, the degree of narrowing at each level and the secondary effects such as the distension of the vertebral venous plexus. The relative contributions of bone, osteophyte, ligament or disc, while better evaluated by CT, are relatively unimportant in the management decisions. Furthermore, MRI will show conditions which may mimic spinal stenosis such as prolapsed thoracic disc, ependymoma of the conus medullaris and dural arteriovenous fistula.

In addition to the diagnosis of prolapsed intervertebral disc, CT and MRI differentiate the contained disc, where the herniated portion remains in continuity with the main body of the disc, from the sequestrated disc where there is a free migratory disc fragment. This distinction may be crucial in the choice of conservative or surgical therapy, and of percutaneous rather than open surgical techniques. MRI studies have shown that even massive extruded disc lesions can resolve naturally with time, without intervention. Despite the presence of nerve root compression, a disc prolapse can be entirely asymptomatic. Gadolinium enhancement of compressed lumbar nerve roots is seen in symptomatic disc prolapse with a specificity of 95.9%.¹

Finally, in the decision as to whether to choose CT or MRI it should be remembered that lumbar spine CT delivers a substantial radiation dose, which is important, particularly in younger patients.

The main remaining uses of myelography are in patients with claustrophobia or otherwise not suitable for MRI. There are advocates for the use of CT myelography in the investigation of MRI negative cervical radiculopathy. Myelography also allows a dynamic assessment of the spinal canal in instances of spinal stenosis and instability. The use of a special MR compatible spinal harness that provides axial loading, and the availability of open and upright MR scanners also provide non-invasive dynamic MR imaging capability.

The problems of the ‘post-laminectomy’ patient or ‘failed back surgery syndrome’ are well known. Accurate pre-operative assessment should limit the number of cases resulting from inappropriate surgery and surgery at the wrong level. The investigation of the post-operative lumbar spine is difficult, and re-operation has a poor outcome in many cases. Although the investigation of the post-operative lumbar spine is difficult, it is vital to make the distinction between residual or recurrent disc prolapse at the operated level and epidural fibrosis, in order to minimize the risk of a negative re-exploration. The best available technique is gadolinium-enhanced MRI.

Arachnoiditis is a cause of post-operative symptoms and its features are shown on myelography, CT myelography and MRI. In the past, many cases were caused by the use of myodil (Pantopaque) as a myelographic contrast medium. It is likely that the use of myodil as an intrathecal contrast agent caused arachnoiditis in most cases, but this became symptomatic in only a minority. The potentiating effects of blood in the CSF, particularly as a result of surgery, have been evident in many cases. New cases of arachnoiditis are now rarely seen, but there is residue of chronic disease still presenting from time to time.

Conclusions

MRI has revolutionized the imaging of spinal disease. Advantages include non-invasiveness, multiple imaging planes and lack of radiation exposure. Its superior soft tissue contrast enables the distinction of nucleus pulposus from annulus fibrosus of the healthy disc and enables the early diagnosis of degenerative changes. However, up to 35% of asymptomatic individuals less than 40 years of age have significant intervertebral disc disease at one or more levels on MRI images. Correlation with the clinical evidence is, therefore, essential before any relevance is attached to their presence and surgery is undertaken. As MRI is, at present, not as accurate as discography in the diagnosis and delineation of annular disease, and in diagnosing the pain source, there has been a resurgence of interest in discography. MRI should be used as a predictor of the causative levels contributing to the back pain with discography having a significant role in the investigation of discogenic pain prior to surgical fusion.²

References

1 Tyrrell P.N., Cassar-Pullicino V.N., McCall I.W. Gadolinium-DTPA enhancement of symptomatic nerve roots in MRI of the lumbar spine. Eur. Radiol.. 1998;8(1):116-122.

2 Cassar-Pullicino V.N. MRI of the ageing and herniating intervertebral disc. Eur. J. Radiol.. 1998;27(3):214-228.

Further reading

Boden S., Davis D.O., Dina T.S., et al. Abnormal magnetic resonance scans of the lumbar spine in asymptomatic subjects. J. Bone Joint Surg. Am.. 1990;72(3):403-408.

Butt W.P. Radiology for back pain. Clin. Radiol.. 1989;40(1):6-10.

Cribb G.L., Jaffray D.C., Cassar-Pullicino V.N. Observations on the natural history of massive lumbar disc herniation. J. Bone Joint Surg. Br.. 2007;89(6):782-784.

Du Boulay G.H., Hawkes S., Lee C.C., et al. Comparing the cost of spinal MR with conventional myelography and radiculography. Neuroradiology. 1990;32(2):124-136.

Horton W.C., Daftari T.K. Which disc as visualized by magnetic resonance imaging is actually a source of pain? A correlation between magnetic resonance imaging and discography. Spine. 1992;17(6Suppl):S164-S171.

Hueftle M.G., Modic M.T., Ross J.S., et al. Lumbar spine: post-operative MR imaging with gadolinium-DTPA. Radiology. 1988;167(3):817-824.

Myelography and Radiculography

CONTRAST MEDIA

Historically, the contrast media that have been used for myelography include gas (CO₂, air), lipiodol, abrodil, myodil, (Pantopaque, iodophenylate), meglumine iothalamate (Conray), meglumine iocarmate (Dimer X), metrizamide (Amipaque), iopamidol (Niopam), iohexol (Omnipaque) and iotrolan (Isovist). The early oil-based media were diagnostically poor and led to arachnoiditis. The early water-soluble media were very toxic and also led to arachnoiditis, and the first intrathecal contrast medium with acceptably low toxicity was metrizamide, a non-ionic dimer. Iohexol and iopamidol are non-ionic monomers licensed for intrathecal use and the ones most commonly used currently.

CERVICAL MYELOGRAPHY

This may be performed by introduction of contrast medium into the thecal sac by lumbar puncture and then run up to the cervical spine, or by direct cervical puncture at C1/2.

LUMBAR RADICULOGRAPHY

This may be performed by injection of contrast medium into the lumbar thecal sac. If for any reason lumbar puncture is not possible, e.g. because of lumbar spine deformity or arachnoiditis, it is possible to introduce the contrast medium from above by cervical injection. Dilution of the contrast as it passes downwards is a major disadvantage.

Indications

Suspected lumbar root or cauda equina compression, spinal stenosis and conus medullaris lesions in patients who are unable or unwilling to undergo MRI.

Contraindications

Lumbar puncture is potentially hazardous in the presence of raised intracranial pressure. It may be difficult to achieve satisfactory intrathecal injection in patients who have had a recent lumbar puncture, since subdural CSF accumulates temporarily, and this space may be entered rather than the subarachnoid space. Accordingly an interval of 1 week or so is advisable.

Contrast medium

The contrast medium is the same as that used for cervical myelography. The maximum dose is again the equivalent of 3 g of iodine, and may be given as 10 ml of contrast medium of 300 mg ml⁻¹ concentration, or 12.5 ml of 240 mg ml⁻¹.

Equipment

Tilting fluoroscopic table.

Patient preparation

As for cervical myelography.

Preliminary radiographs

AP and lateral projections of the region under study are taken. Preliminary examination of radiographs is helpful to assess the anatomy of the spine, in order to facilitate the lumbar puncture, and to assist in interpretation of the images. It is important to draw the surgeon’s attention to any question of ambiguous segmentation, either lumbarization or sacralization. There is a potential danger of operating at the wrong level if this is not made absolutely clear in the report. A clear description of any anomaly is required, together with a statement of how the vertebrae have been numbered in the report.

Technique

1. The lumbar thecal sac is punctured at L2/3, L3/4 or L4/5. The higher levels tend to be away from the most common sites of disc herniation and stenosis, and puncture may, therefore, be easier.

2. Lumbar puncture can technically be performed in the lateral decubitus position, in the sitting position, or even in the prone position. In the prone position the needle is guided under fluoroscopy, usually at the L2/L3 interspinous space with the patient lying on a folded pillow. This is important, because in the prone position the spinous processes are approximated due to lordosis, rendering puncture more difficult. In addition, spinal extension produces a relatively narrow thecal sac. The sitting position allows easy lumbar puncture, but is unsatisfactory for two reasons. First, the injected contrast medium drops through a large volume of CSF to accumulate in the sacral sac and becomes diluted as it descends. Second, patients may faint in this position, a complication that can be very dangerous, since the radiologist is on the wrong side of the table to help in preventing the patient from coming to any harm.

3. If lumbar puncture is carried out in the lateral decubitus position (described below) moderate spinal flexion is desirable, but there is no need for the extreme flexion sometimes demanded of the patient. A small pillow is placed under the dependent lumbar angle to keep the spine straight. The relevant interspace is one or two spinous processes above the plane of the iliac crest (L4/L5). If the spinous process cannot be felt, lateral fluoroscopy may help.

4. In obese patients the apparent soft-tissue midline gravitates below the spinal midline. The midline position may be verified while introducing local anaesthetic (1% lidocaine) into the skin and subcutaneous tissue, though there is no need to infiltrate the interspinous ligament. A 22G spinal needle should be used. It should be introduced with only a 10–15 ° cranial angulation. The passage of the needle through the interspinous ligament has a very characteristic sensation of moderate smooth resistance. Lack of resistance implies passage in the fatty tissues lateral to the midline, and a gritty sensation means impingement on the bone of the spinous process.

5. There is a tendency in inexperienced operators to introduce the needle at too steep a cranial angle, which a casual inspection of the spinous process anatomy can show to be incorrect. While traversing the interspinous ligament, the bevel should be in the coronal plane to avoid deflection to one side or the other, but once well established in the ligament may be turned to penetrate the thecal sac parallel to its long axis.

6. There is a characteristic sudden loss of resistance as the needle enters the thecal sac, and at this time the stilette should be withdrawn to verify CSF flow out of the needle. In the prone position suction using a 2-ml syringe may be necessary to obtain CSF. It should then be reintroduced and the needle advanced about 2 mm to ensure that the whole of the bevel has entered the thecal sac. A flexible connector is attached, taking care not to disturb the needle position.

7. Most difficulties are technical, arising from non-midline positioning of the needle, but in the presence of canal stenosis it may be difficult to find a position among the crowded roots where good CSF flow will take place. In most cases, radiologists will prefer to observe the entry of contrast medium into the thecal sac on the fluoroscopic screen, and this is especially important if there has been any difficulty in achieving a good needle position.

8. After the contrast medium has been injected, the patient turns to lie prone, and a series of films is obtained. Before taking films ensure that the relevant segment of the spinal canal is adequately filled with contrast medium. This usually requires some degree of feet down tilt of the table, and a footrest should be in place to support the patient.

Radiographic views

1. AP and oblique views are obtained. (About 25 ° of obliquity is usual, but tailored in the individual case to profile the exit sleeves of the nerve roots of the cauda equina.)

2. A lateral view with a horizontal beam is useful, but further laterals in the erect or semi-erect position on flexion and extension are very useful, adding a dynamic dimension to the study.

3. Some radiologists advocate lateral decubitus frontal oblique views, to allow full entry of contrast medium into the dependent root sleeves of the whole lumbar and lower thoracic thecal sac. When turning patients from one side to the other ensure that they turn through the prone position, as turning supine will produce irretrievable contrast medium dilution.

At this stage the study will be complete as far as the question of root compression is concerned. The films should be carefully reviewed at this stage to ensure that all areas are fully covered, as the next manoeuvre will make any return to this area impossible. If the study is good, the patient should be screened in the lateral decubitus position, and tilted level or slightly head down until the contrast medium flows up to lie across the thoraco-lumbar junction. The patient may then be turned to lie supine and films of the conus and lower thoracic area obtained in the AP projection.

Additional technique

Post-myelographic MDCT is helpful for good visualization of the conus and cause of root compression and should routinely be done after myelography.

THORACIC MYELOGRAPHY

If the thoracic spine is the primary region of interest the lumbar puncture injection is made with the patient lying on one side, with the head of the table lowered and the patient’s head supported on a bolster or pad to prevent contrast medium from running up into the head. If an obstruction to flow is anticipated, about half the volume of contrast medium may be injected and observed as it flows upwards. If an obstruction is encountered, the contrast medium is allowed to accumulate against it, and the remainder of the contrast medium is then injected slowly (this may cause some discomfort or pain and patience must be used). This manoeuvre will, in some cases, cause a little of the contrast medium to flow past the obstructing lesion and demonstrate its superior extent. If there is no obstruction, the full volume is injected. When the injection is complete, lateral radiographs may be taken and the patient then turned to lie supine. Further AP views are then taken.

CERVICAL MYELOGRAPHY BY LUMBAR INJECTION

The technique proceeds as for thoracic myelography, but the patient remains in the lateral decubitus position until the contrast medium has entered the neck. With the head raised on a pad or bolster contrast will not flow past the foramen magnum. When all the contrast has reached the neck the patient is turned to lie prone, and the study then completed as for a cervical injection study.

CT MYELOGRAPHY

CT myelography (CTM) should be delayed for up to 4 h after injection to allow dilution of the contrast medium. A very high concentration may cause difficulty in resolving the cervical nerve roots. Turning the patient a few times prior to CT ensures even distribution and reduces layering effects. In studying the spinal cord a delay is not required though, again, good mixing of the CSF with contrast medium is essential. The superior contrast resolution of CT allows the definition of very dilute contrast medium, e.g. beyond a spinal block, thus avoiding the need for a cervical puncture. Nerve root exit foramina may be studied by CTM in both the lumbar and cervical region, and it has been shown to be a sensitive technique, though it fails to demonstrate far lateral disc lesions. Delayed CTM is needed in suspected syringomyelia.

PAEDIATRIC MYELOGRAPHY

A few points need to be borne in mind when carrying out myelography in the paediatric age group:

1. General anaesthetic is essential for all children aged 6 years or younger, and for many children up to the age of 12 years.

2. Lumbar puncture in cases of spinal dysraphism carries the risk of damaging a low-lying cord due to tethering. The thecal sac is usually wide in these conditions and the needle should be placed laterally in the thecal sac. In addition, as low a puncture as possible will minimize the risk, though in practice spinal cord injury is very uncommon or masked by the neurologic deficit already present.

3. In dysraphism, the frequent association of cerebellar tonsillar herniation precludes lateral C1/2 puncture.

Aftercare

Most patients may be discharged home after being allowed to rest for a few hours after the study. The practice of automatic hospitalization for myelography can no longer be justified in the light of improved contrast media with very low rates of serious morbidity. The patient may remain ambulant. A good fluid intake is generally advised though its value is unproven.

Complications

1. Headache occurs in about 25% of cases, slightly more frequent in females

2. Nausea and vomiting in about 5%

3. Subdural injection of contrast medium. This occurs when only part of the needle bevel is within the subarachnoid space. Contrast medium initially remains loculated near the end of the needle, but can track freely in the subdural space to simulate intrathecal flow. When in doubt, the injection should be stopped, and AP and lateral views obtained with the needle in situ. The temptation of interpreting such an examination should be resisted and the patient re-booked

4. Extradural injection of contrast medium outlines the nerve roots well beyond the exit foramina

5. Intramedullary injection of contrast medium. This is a complication of lateral cervical puncture or in a low-lying spinal cord, and is recognized as a slit-like collection of contrast medium in the spinal canal. Small collections are without clinical significance.

LUMBAR DISCOGRAPHY

Aims

There is strong evidence to support the role of discography in identifying patients with lumbar discogenic pain, but only moderate and limited supportive evidence in cervical and thoracic discogenic pain:

1. To opacify the disc with contrast medium injected into the nucleus pulposus in order to demonstrate degeneration and herniation.

2. To provoke and reproduce the pain for which the patient is being investigated and to assess its response to anaesthetic injection.

Indications

Given the present status of MRI, any request for discography must be considered with great care, as it is a painful procedure and not without risk. If infection occurs the disc will be permanently damaged. The indications are:

1. suspected discogenic pain without radicular signs

2. confirmation of normal discs above or below a proposed surgical fusion.

Contraindications

1. None absolute (except allergy to iodine)

2. Any local or distant sepsis will add to the risk of infective discitis

3. Patient not a surgical candidate due to comorbidity.

Contrast medium

Nonionic contrast media such as iopamidol or iohexol. A normal disc will usually allow up to 1.0 ml to be injected.

Equipment

1. Radiographic equipment as for myelography. Biplane screening is essential to ensure correct needle positioning.

2. Discography needles – a set of two needles are used for each level:

a Outer needle, 21G, 12.5 cm

b Inner needle, 26G, 15.8 cm.

Patient preparation

The procedure and its aim are explained to the patient. It is important (1) that patients are asked to describe what pain they experience and (2) that patients should not be told that they may get symptomatic pain. This precaution reduces the chance of obtaining a programmed response from the patient. No other preparation is needed. The procedure is done under local anaesthesia. Pre-medication and analgesia may alter the patient’s subjective response to discography, diminishing its efficacy and usefulness. Diazepam may, however, be required in very anxious patients. Some authors recommend broad-spectrum antibiotic cover (e.g. cephalosporins) given immediately before the examination to minimize the risk of infection.

Preliminary radiographs

AP and lateral films should be available or obtained.

Technique

1. There are two possible needle approaches:

a The posterior approach, which traverses the spinal canal

b The lateral oblique extradural approach, which avoids puncture of the dura and the vulnerable part of the posterior annulus. This is the preferred approach and can be carried out with the patient in the prone or left lateral decubitus position. The left lateral decubitus position is preferred, with the patient’s head resting on a pillow and a pad placed in the lumbar angle to maintain a straight spine. Moderate spinal flexion is useful, especially at L5/S1.

2. Full aseptic technique is mandatory; there should be no compromise on this point. The operator and any assistant should be gowned, masked, capped and gloved, and the patient should be draped. The level to be examined is determined by fluoroscopy, and the skin is anaesthetized, usually a hand’s breadth from the spinous processes.

3. The outer 21G needle is then directed towards the posterior aspect of the disc under intermittent fluoroscopic control, at an angle of 45–60 ° to the vertical. An additional caudal tilt may be necessary for the L5/S1 level. This needle should reach but not traverse the annulus fibrosus. This point is recognized by a distinct feeling of resistance when the outer fibres are encountered. The 26G needle is then introduced through the 21G needle and the entry of its tip into the nucleus pulposus confirmed in two planes with the aid of the image intensifier prior to contrast medium injection.

4. Contrast medium is injected slowly using a 1-ml syringe. This is done under intermittent fluoroscopic control, while the pain response, the disc volume and its radiographic morphology are monitored. The resistance to flow will gradually increase in a normal disc during the 0.5–1.0-ml stage.

Radiographic views

1. AP and lateral films are obtained at each level examined.

2. At the end of the procedure after needle removal, AP and lateral films are taken in the standing position.

3. Films in flexion and extension may be useful.

Computed tomography post discogram

Thin-section CT slices aid in optimizing morphological grading of disc abnormalities, with particular reference to the status of the annulus and the degree and extent of annular tears.

Patient interrogation

Normal discs and some abnormal discs are asymptomatic. In the symptomatic abnormal discs, the pattern and distribution of pain are noted, together with any similarity to the usual symptomatology. At each symptomatic level local anaesthetic (bupivacaine hydrochloride 0.5%) may be injected to test its efficacy in producing symptomatic relief.

Aftercare

Simple analgesia may be required and overnight admission is usually advised to ensure adequate pain control.

Complications

1. Discitis is the most important complication. Pain with or without pyrexia after a few days indicates this development. Narrowing of the disc space with a variable degree of end-plate sclerosis is seen after a few weeks. Most cases are due to low-grade infection and require treatment with antibiotics.

2. With the transdural approach, post-lumbar puncture headache and/or vomiting may occur.

Further reading

Buenaventura R.M., Shah R.V., Patel V., et al. Systematic review of discography as a diagnostic test for spinal pain: an update. Pain Physician. 2007;10(1):147-164.

Colhoun E., McCall I.W., Williams L., et al. Provocation discography as a guide to planning operations on the spine. J. Bone. Joint. Surg. Br.. 1988;70(2):267-271.

McCulloch J.A., Waddell G. Lateral lumbar discography. Br. J. Radiol.. 1978;51(607):498-502.

Tehranzadeh J. Discography 2000. Radiol. Clin. North Am.. 1998;36(3):463-495.

Intradiscal Therapy

The ability to carry out successful discography will enable the radiologist, with the cooperation of interested clinicians, to carry out therapeutic procedures such as mechanical percutaneous disc removal, laser therapy and intradiscal electrothermal therapy (IDET). While each has advocates, none is widely utilized, and the practice of such methods should be subject to very strict selection criteria and rigorous audit of the outcomes.

FACET JOINT ARTHROGRAPHY

Indications

This is performed for diagnostic and therapeutic purposes, primarily at the lumbar level. Intra-articular injection is the only effective means for assessing the facet joints as a source of back pain. The only indication, therefore, is suspected pain of facet joint origin. Such pain may strongly resemble radicular pain, and patients have often been managed on this basis over a long period of time without success.

Affected facets are usually degenerate as visualized on plain radiographs, CT or MRI. The facet joint capsule is richly innervated by the dorsal ramus of the lumbar spinal nerves. The procedure is valid in that many patients with degenerate facets do not have facet joint pain, and the role of the facet joint in the back pain of the individual patient cannot, therefore, be determined without facet joint injection. The arthrogram is not, therefore, a study of pathological anatomy; the visualization of the joint is important only to verify the needle position. Having visualized the joint, local anaesthetic can be injected to judge the patient’s response. In cases obtaining good relief of symptoms, further management will then consist either of a programme of regular steroid injection therapy, cryolysis, radiofrequency or spinal fusion to prevent facet movement.

Equipment

1. As for myelography

2. A 22G spinal needle is appropriate for the study.

Contrast medium

Non-ionic contrast medium 0.1–0.2 ml should be used.

Technique

1. This is an outpatient procedure which involves the simultaneous injection of both joints at each level to be studied. More than one level should not be examined in each session to avoid diagnostic confusion. Needle placement can be done using fluoroscopy or CT guidance.

2. Using fluoroscopy the joint space is profiled by slowly rotating the patient from a prone position into a prone oblique orientation with the relevant side raised.

3. Sterile procedures are required.

4. The spinal needle is inserted and advanced perpendicularly to the facet joint, under fluoroscopic control. Caudal needle angulation is sometimes needed if the iliac crest overlies the L5/S1 facet joints. Alternatively the needles can be placed by simultaneous advancement into the joints using CT guidance.

5. In the majority of cases a noticeable ‘give’ indicates that the capsule is penetrated.

6. Contrast medium injection confirms correct needle placement by demonstrating immediate opacification of a superior and inferior recess.

7. Correct needle placement is documented showing intra-articular injection. The arthrographic appearances are not of any diagnostic consequence.

8. For diagnostic purposes up to 1 ml of 0.5% bupivacaine hydrochloride (Marcaine) is injected in the facet joint and the response over the ensuing 24-h period documented. For therapeutic injection, 0.5 ml of 0.5% Marcaine mixed with 0.5 ml of Depo-Medrone (methylprednisolone 40 mg ml⁻¹) is injected after arthrography.

Further reading

Fairbank J.C., Park W.M., McCall I.W., et al. Apophyseal injection of local anaesthetic as a diagnostic aid in primary low back syndromes. Spine. 1981;6:598-605.

McCall I.W., Park W.M., O’Brien J.P. Induced pain referral from posterior lumbar elements in normal subjects. Spine. 1979;4(5):441-446.

Maldague B., Mathurin P., Malghem J. Facet joint arthrography in lumbar spondylolysis. Radiology. 1981;140(1):29-36.

Mooney V., Robertson J. The facet syndrome. Clin. Orthop. Relat. Res.. 1976;115:149-156.

Percutaneous Vertebral Biopsy

The percutaneous approach to obtaining a representative sample of tissue for diagnosis prior to therapy is both easy and safe, avoiding the morbidity associated with open surgery. It has a success rate of around 90%. Accurate lesion localization prior to and during the procedure is required. Vertebral body lesions may be biopsied under either CT or fluoroscopic control. Small lesions, especially those located in the posterior neural arch, are best biopsied under CT control. A preliminary CT scan is helpful, whatever method is finally chosen to control the procedure.

Indications

Suspected vertebral or disc infection and vertebral neoplasia. Note that the presence of a more accessible lesion in the appendicular skeleton should be sought by radionuclide bone scanning, before vertebral biopsy is undertaken.

Contraindications

1. Biopsy should not be attempted under any circumstances in the presence of abnormal and uncorrected bleeding or clotting time or if there is a low platelet count.

2. Lesions suspected of being highly vascular, e.g. aneurysmal bone cyst or renal tumour metastasis are relatively dangerous, and a fine-needle aspiration should be used instead of a trephine needle for these cases.

Equipment

Numerous types of biopsy needle are available. The commonest type used is the Jamshidi set. A trephine needle with an internal diameter of 2 mm or more is required, minimizing histological distortion and reducing sampling error without increasing the complication rate. Specimen quality is higher with the Jamshidi type.

Patient preparation

Sedation/analgesia and, where necessary, general anaesthesia are required, preferably administered and monitored by an anaesthetist.

Technique

1. For a fluoroscopy-guided procedure the lateral decubitus position is used. For CT control the prone position is preferable.

2. The skin entry point distance from the mid-line is about 8 cm for the lumbar region and 5 cm in the thoracic region.

3. The aim of the procedure is to enter the vertebral body at about 4 o’clock or 8 o’clock (visualizing the body with the spinous process at 6 o’clock). Local anaesthetic may be injected via a 21G spinal needle to allow deep infiltration of the soft tissues into close proximity to the periosteum.

4. The biopsy needle is advanced at between 30 and 45 ° to the sagittal plane in the thoracic and lumbar spine, respectively.

5. When the biopsy needle impinges on the cortex of the vertebral body its position is confirmed fluoroscopically in both AP and lateral planes, or on a single CT section. The trocar and cannula are then advanced through the cortex and the trocar is then withdrawn.

6. Using alternate clockwise and anticlockwise rotation the biopsy cannula is advanced approximately 1 cm.

7. By twisting the needle firmly several times in the same direction the specimen is severed.

8. At least two cores of bone may be obtained by withdrawing the needle back to the cortex, angulating and re-entering the vertebral body.

9. The needle is then withdrawn while simultaneous suction is applied by a syringe attached to the hub.

10. To remove the specimen, the plunger is inserted at the sharp end of the needle and the tissue is pushed out. Any blood clot should be included as part of the specimen.

11. In suspected infection the end-plate rather than the disc is biopsied. Most cases are due to osteomyelitis extending to the disc space. If there is a para-vertebral abscess, aspiration and culture of its contents is preferable to vertebral biopsy.

Aftercare

1. Overnight stay with routine nursing observation and analgesia if needed.

2. The approach to a thoracic lesion should be extra-pleural, but if any doubt exists, a chest X-ray should be obtained after the procedure, as there is a small risk of pneumothorax or haemothorax.

Complications

These are rare, but there are potential risks to nearby structures in poorly controlled procedures, including the lung and pleura, aorta, nerve roots and spinal cord. Local bleeding is an occasional problem.

Further reading

Babu N.V., Titus V.T., Chittaranjan S., et al. Computed tomographically guided biopsy of the spine. Spine. 1994;19(21):2436-2442.

Shaltot A., Michell P.A., Betts J.A., et al. Jamshidi needle biopsy of bone lesions. Clin. Radiol.. 1982;33:193-196.

Stoker D.J., Kissin C.M. Percutaneous vertebral biopsy: a review of 135 cases. Clin. Radiol.. 1985;36:569-577.

Tehranzadeh J., Tao C., Browning C.A. Percutaneous needle biopsy of the spine. Acta Radiol.. 2007;48(8):860-868.

Bone Augmentation Techniques

The vertebral bodies can collapse in osteoporosis and metastatic disease. The injection of small amounts of bone cement directly into the vertebral body (vertebroplasty) strengthens the vertebral body and is successful in control of spinal pain. Pre-procedure radiographs and an MRI scan are obtained, while a spinal surgeon is on standby should any complications require surgical intervention. Multiple levels can be treated in this manner with placement of the needle in the vertebral body using either a transpedicular approach or a posterolateral approach. Careful aseptic technique and fluoroscopic/CT guidance during cement injection is essential to avoid cement migration into the canal and/or veins. An allied technique (kyphoplasty) in addition partially restores vertebral body height in osteoporotic vertebral fractures.

Further reading

Burton A.W., Rhines L.D.&E., Mendel E. Vertebroplasty and kyphoplasty: a comprehensive review. Neurosurg. Focus. 2005;18(3):e1.

Hide I.G., Gangi A. Percutaneous vertebroplasty: history, technique and current perspectives. Clin. Radiol.. 2004;59(6):461-467.

Nerve Root Blocks

LUMBAR SPINE

This is undertaken in difficult diagnostic cases, usually in the presence of multilevel pathology, especially in post-operative situations. If the injected local anaesthetic in the perineural space abolishes the patient’s symptoms it is concluded that pain is originating from the injected nerve root. Therapeutic instillation of local anaesthetic with steroid (e.g. triamcinolone, betamethasone [Celestone Soluspan]) has proved successful as a means of treating sciatica in patients with disc prolapse, especially in a foraminal location. It is crucial that a review of the MRI images takes place before the procedure is carried out to ensure that the correct level and side are in accordance with the patient’s symptoms. The objective is to place the needle outside the nerve root sleeve so that the injected substances diffuse between the disc prolapse and the compressed nerve. Reduction of the inflammatory response induced by the herniated disc can be slow and improvement of symptoms can take up to 8–12 weeks.

The accurate placement of the tip of a spinal needle is confirmed by the injection of a small amount of contrast medium. This is important to avoid injection in one of the lumbar vessels as, rarely, paraplegia presumed to be due to inadvertent intra-arterial injection has been reported. This risk needs to be communicated in the informed consent with the patient prior to the procedure.

Under local anaesthetic control, the needle is advanced using fluoroscopic or CT guidance, to a point inferior and lateral to the ipsilateral pedicle. The extra-foraminal nerve roots are outlined by contrast medium and for diagnostic purposes a small amount of 0.5% bupivacaine is instilled as a means of assessing the correct level responsible for the patient’s sciatica.

CERVICAL SPINE

Perineural root sleeve therapy can also be used in cervical radiculopathy. Correct needle placement using CT and fluoroscopy is very important, utilizing contrast medium injection for confirmation prior to the therapeutic injection of lidocaine (bupivacaine is not used in the cervical spine) and steroid. There is a real risk of inadvertent vascular injection, particularly in the vertebral artery. CT fluoroscopic guidance at the required foraminal level is used to ensure the needle traverses in a horizontal or slightly downward course posterior to the carotid and jugular vessels. The needle tip is aimed towards the outer rim of the posterior bone outline of the foramen so as to avoid the vertebral vessels and the nerve root.

Further reading

Blankenbaker D.G., De Smet A.A., Stanczak J.D., et al. Lumbar radiculopathy: treatment with selective lumbar nerve blocks. Comparison of effectiveness of triamcinolone and betamethasone injectable suspensions. Radiology. 2005;237(2):738-741.

Herron L.D. Selective nerve root block in patient selection for lumbar surgery: surgical results. J. Spinal Disord.. 1989;2(2):75-79.

Schellhas K.P., Pollei S.R., Johnson B.A., et al. Selective cervical nerve root blockade: experience with a safe and reliable technique using an anterolateral approach for needle placement. Am. J. Neuroradiol.. 2007;28(10):1909-1914.

Wagner A.L. Selective lumbar nerve root blocks with CT fluoroscopic guidance: technique, results, procedure time, and radiation dose. Am. J. Neuroradiol.. 2004;25(9):1592-1594.

Wagner A.L. CT fluoroscopic-guided cervical nerve root blocks. Am. J. Neuroradiol.. 2005;26(1):43-44.

Weiner B.K., Fraser R.D. Foraminal injection for lateral lumbar disc herniation. J. Bone Joint Surg. Br.. 1997;79(5):804-807.

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