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Chronic mechanical back pain:
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Earn Category I CME credit by reading this article and the associated article and successfully completing the post-test. Successful completion is defined as a cumulative score of at least 70% correct. This material has been reviewed and is approved for 1 hour of clinical Category I (Preapproved) CME credit by the AAPA. The term of approval is for 1 year from the publication date of July 2004. |
Learning objectives
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Sixty-five percent to 80% of Americans have an episode of low back pain at some time in their lives.1 Although most cases resolve quickly, 40% recur and 5% result in a residual disability after 1 year.2 Management of chronic back pain—pain that persists longer than 12 weeks—is the subject of this article.
Using precision diagnostic blocks in chronic back pain that did not respond to conservative treatment, researchers isolated facet joint pain in 40% of cases, discogenic pain in 26%, segmental dural or nerve root pain in 13%, and sacroiliac (SI) joint pain in 2%.1 This article describes successful treatments of these common causes of chronic back pain after conservative measures have failed (see Figure 1).
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Foremost in the evaluation of low back pain is to rule out cancer, infection, or a neurologic or medical emergency. A workup for neoplasm is justified in a patient who is older than 50 years or younger than 20 years, or who has a history of cancer, constitutional symptoms, or pain that is worse at night or in the supine position. A history of bladder or bowel incontinence, reflex deficits, or weakness in extremities warrants MRI to rule out a neurologic emergency such as cauda equina syndrome and the need for possible urgent surgery for nerve decompression. Complaints of fever and chills and a history of IV drug abuse, immune suppression, corticosteroid use, or recent urinary tract infection suggest an infectious process. Referred visceral pain, such as from an abdominal aortic aneurysm, also needs to be investigated.
Onset, duration, frequency, location, radiation, quality, intensity, and aggravating and alleviating factors of the pain should be evaluated. The patient's medical, family, and social histories should be reviewed, including past pain complaints, involvement in motor vehicle crashes, injuries, and disorders such as arthritis, fibromyalgia, or systemic lupus erythematosus. The social history should include the patient's occupational history, education, environmental information, and history of substance abuse. A family history of pain problems, degenerative disorders, familial disorders, substance abuse, and psychological disorders is also important.
During the physical exam, observe the patient's gait and attempts to walk heel-to-toe and to mount the exam table; abnormalities in these areas may point to neurologic deficits, indicating the need for imaging studies. Inspect the skin for rashes or lesions; painful vesicles or scars in a dermatomal pattern may indicate acute shingles or postherpetic neuralgia. Tests for active and passive range of motion of the lumbar spine and hips should be performed. Palpate the area of pain for muscle spasm and for tenderness over the facets and SI joint. Evaluate reflexes and sensation, and have the patient perform a straight leg raise. Perform flexion, abduction, extension, and rotation (FABER) maneuvers.
After a comprehensive physical examination has ruled out those problems that would require acute intervention or further investigation, treatment directed toward mechanical back pain may be initiated. When conservative treatment fails, other interventions may be appropriate; to implement these, it is important to learn the source of the pain.
Mechanical low back pain is caused by inflammation due to injury to the spine's ligaments, muscles, facets, or SI joint. Although muscle strains can be self-limiting, conservative therapies such as rest, ice, a muscle relaxant, an NSAID, and physical therapy may be beneficial. Pain that persists despite conservative treatment should be reevaluated.
Facets—the synovial joints between the vertebrae—provide structural support to the posterior aspects of the spine and contribute to its flexibility. Ligaments around the facet joint combine with the synovium to form the joint capsule. Often the facet joint complex contributes to back pain. Facet arthropathy may be caused by a combination of aging, pressure overload of the joints caused by narrowing disks, and injury. Lumbar facet pain typically presents in a bandlike distribution across the low back, although it can radiate to the posterior or anterior thigh or groin. Pain is typically exacerbated by activity, standing or sitting for long periods of time, and lumbar extension. The patient may find standing in a forward-flexed posture comfortable. Pressure on the involved facet joints during the physical exam will cause discomfort, which will be exacerbated with a hyperextension maneuver.
The SI joint connects the sacrum and the ileum and is covered by both hyaline and fibrocartilage. This joint is not very flexible, moving only 2 to 4 mm. SI joint pain can be caused by injury, inflammation, or excessive motion due to abnormalities in the joint. This type of pain is particularly common in women who have given birth and whose SI joint has been disrupted by hormonal changes and mechanical forces. It is also common among patients who participate in ice skating, golf, and bowling because of the repetitive torsional forces involved in those sports. SI joint inflammation can also be caused by rheumatologic disorders such as Reiter's syndrome, ankylosing spondylosis, and psoriatic arthritis.
Common symptoms of an SI joint problem are pain in the low back, buttock, or thigh; sciatica-like pain; and difficulty sitting for long periods. To evaluate for SI joint pain on the physical exam, perform Gaenslen's test and FABER, and observe for Patrick's sign (pain with external hip rotation). Distraction and compression tests may also be performed.
If conservative treatments such as those described above for muscle strains fail to resolve facet or SI joint inflammation, an anesthetic block or denervation may provide lasting relief. An anesthetic agent, such as bupivacaine, is combined with a corticosteroid and injected directly into the facet or SI joint with the aid of fluoroscopy; the local anesthetic interrupts the pain-spasm cycle, and the corticosteroid reduces inflammation.3
A medial branch block may also be used to treat facet pain. The medial branch of the dorsal primary ramus of the spinal nerve supplies the facet joint, the supraspinal ligament, and the interspinal ligaments. Branches from the adjacent spinal nerve and the spinal nerve above supply each joint. Complete denervation of any facet requires blockade of two levels. A facet or SI joint injection is considered successful when a patient's pain is reduced by half. One study of patients with facet pain found that all who received a series of three medial branch blocks had significant relief for up to 3 months, 82% for up to 6 months, and 21% for up to 12 months.4 Contraindications to facet or SI joint injections include bacterial infection, pregnancy, bleeding diathesis, and anticoagulant therapy. Precautions should be taken in the presence of diabetes or a prosthetic heart valve.
A joint injection that provides only short-term relief may be considered diagnostic of either SI or facet joint pain, for which radio-frequency neuroablation or other types of rhizotomy may be tried.
Radio-frequency ablation offers greater precision than cryoneurolysis and chemical neurolysis by using relatively small-caliber probes. Although the patient's pain may increase for 5 to 7 days after the procedure, relief is typically noted within 2 to 3 weeks and may last for several months. One study showed that 60% of patients had at least 90% relief 12 months postprocedure, and 87% of patients had at least 60% relief.5
Surgery (fusion and laminectomy procedures) or an implantable spinal cord stimulator may be considered if denervation procedures do not provide lasting relief to patients with pain originating in the SI or a facet joint.
A tear in the annulus of an intervertebral disk and direct pressure to the nerve roots exiting the spinal canal are also common causes of low back pain. Annular tears tend to cause pain that refers to the buttock but rarely follows dermatomal or myotomal patterns. Diskography, a diagnostic procedure used to determine the origin of pain in the spine, is necessary to confirm an annular tear. (This test should not be used to diagnose disk herniation; CT or MRI is appropriate in that instance.) Diskography is useful in evaluating persistent, severe symptoms when other diagnostic tests have failed to determine a cause and in assessing persistent pain following a fusion or laminectomy. It involves performing a CT scan to track radiopaque dye that has been injected into a disk under fluoroscopy. The CT tracks the dye distribution, revealing any annular tears, disk bulges, or changes in the nucleus. Diskography may reveal an abnormality on a disk that appeared normal on MRI.6
After diskography confirms the pathology, intradiscal electrothermal therapy (IDET) can be performed on the troublesome disk or disks. In this procedure, a needle is inserted into the disk under fluoroscopy, and a wire is threaded along the inner wall of the annulus and across the entire posterior wall. The wire is then heated, breaking down the collagen fibers and causing them to clump, which reinforces the disk. A patient who has undergone IDET must wear a special back brace for several weeks and undergo physical therapy to learn proper mechanics and to strengthen muscles in the back. Studies have shown a statistically significant positive effect on patient self-reported pain levels, overall disability, and physical functioning.7-9
Pressure on a nerve root may be caused by a herniated nucleus pulposus or by epidural scarring from a prior laminectomy. Lumbar radiculopathy is pain that occurs in a dermatomal distribution determined by the affected nerve root. Other causes of direct nerve root compression are vascular compromise, inflammation, and biochemical influences.10 Radicular pain can occur in the buttock, hip, thigh, groin, calf, and foot; patients describe this pain as shooting, stabbing, shocking, tingling, and electric. Pain is usually reproduced by the straight-leg-raise maneuver, and sensation may be affected.
In addition to nerve root compression, other causes of radicular pain include radiculitis, a benign, usually self-limiting inflammation of the nerve root; a bulging or herniated disk; and epidural fibrosis, scar formation from previous back surgery. Estimates are that 5% to 40% of lumbar surgeries result in persistent low back pain, termed failed back surgery syndrome.11 Peridural fibrosis is thought to be responsible for as many as 25% of cases of failed back surgery syndrome.12
In addition to NSAIDs and muscle relaxants, membrane stabilizing agents (anticonvulsants) may be effective for radicular symptoms. Gabapentin (Neurontin) is frequently used because of its tolerable side effects and apparent clinical utility for refractory pain. Physical therapy may be appropriate in radicular pain without progressive neurologic deficits.
Patients whose radicular pain does not respond to the above treatments are candidates for an epidural steroid injection. These injections may be performed under fluoroscopy using a transforaminal approach, a procedure that is known as a selective nerve root block. Selective nerve root blocks may be considered diagnostic as well as therapeutic, helping to confirm that a specific nerve is involved in the patient's pain. To perform the block, a corticosteroid, which may be mixed with an anesthetic agent, is given via an epidural injection. More than one injection may be needed before improvement is noted. In one study, patients with symptomatic lumbar disk herniations who were candidates for diskectomy were treated with an epidural injection.13 After an average follow-up of 1.5 years, 77% had a successful resolution or a significant decrease in symptoms. Two other studies demonstrated similar relief with fluoroscopically guided transforaminal epidural steroid injections. In one study, epidural injections resulted in 84% success after 1.4 years, compared with 48% for trigger point injections.14 Another study that evaluated patients with unilateral radicular pain that did not respond to physical therapy, anti-inflammatories, or analgesics reported a successful outcome in 75% of patients who had undergone transforaminal epidural injections after 1 year.15
Adhesiolysis can be used when epidural scarring is the cause of radicular pain in patients who have undergone lumbar surgery. The procedure involves first injecting radiopaque dye through a catheter inserted into the epidural space from a caudal approach. Imaging often reveals fibrosis. Volumetric irrigation with hypertonic saline, hyaluronidase, a steroid, or a combination of any of these three is then performed. Other studies have shown moderate short-term and long-term effectiveness with repeat procedures.1
In the United States, the primary indications for spinal cord stimulation are failed back surgery syndrome and complex regional pain syndromes, while in Europe this procedure is used mainly to treat chronic intractable angina and pain and disability due to peripheral vascular disease.16 A set of electrodes is placed in the epidural space and connected to a pulse generator that is implanted in the upper buttock. Low levels of electrical impulses replace pain signals to the brain with a tingling sensation. Before permanent placement, patients should undergo psychological screening and a trial stimulator.
Oral opioid therapy is gaining acceptance in the treatment of chronic, nonmalignant pain when other modalities fail or are contraindicated. Opioids, typically morphine, may also be delivered via an intrathecal pump, a modality that may be considered when oral agents provide insufficient relief or when sedation and confusion are problematic.17 An intrathecal pump delivers the drug directly to the spinal fluid, allowing lower doses to be used than when opioids are taken orally.18 The procedure involves placement in the thecal sac of a catheter, which is tunneled subcutaneously to a pump implanted in the lower abdomen. Programmable pumps deliver the drug in different dosages at different times of day.
Medications other than morphine are currently under investigation for use in the intrathecal route. The advantages of the intrathecal pump for pain control are that more powerful analgesia is delivered using a lower dosage; relief is more consistent; somnolence, mental clouding, constipation, and euphoria are reduced; and manipulation for abusive purposes is very difficult.
When conservative treatment fails, techniques such as facet blocks, SI blocks, radio-frequency neuroablation, epidurals, selective nerve root blocks, IDET, spinal cord stimulation, and intrathecal drug administration may allow the patient to resume normal activities of daily living.
Acknowledgment
The author appreciates the help of Richard Rauck, MD, and W. Joseph Martin, DO, in the development of this article.
REFERENCES
1. Manchikanti L, Staats PS, Singh V, et al. Evidence-based practice guidelines for interventional techniques in the management of chronic spinal pain. Pain Physician. January 2003;6:3-81.
2. Abraham I. Low back pain management. Clinical Advisor. September 2000:35-49.
3. Byrod G, Otani K, Brisby H, et al. Methylprednisolone reduces the early vascular permeability increase in spinal nerve roots induced by epidural nucleus pulposus application. J Orthop Res. 2000;18:983-987.
4. Manchikanti L, Pampati V, Bakhit CE, et al. Effectiveness of lumbar facet joint nerve blocks in chronic low back pain: a randomized clinical trial. Pain Physician. 2001;4(1):101-117.
5. Dreyfuss P, Halbrook B, Pauza K, et al. Efficacy and validity of radiofrequency neurotomy for chronic lumbar zygapophysial joint pain. Spine. 2000;25:1270-1277.
6. Horton WC, Daftari TK. 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(6 suppl):S164-S171.
7. Saal JS, Saal JA. Management of chronic discogenic low back pain with a thermal intradiscal catheter. A preliminary report. Spine. 2000;25:382-388.
8. Karesek M, Bogduk N. Twelve-month follow-up of a controlled trial of intradiscal thermal anuloplasty for back pain due to internal disc disruption. Spine. 2000;25:2601-2607.
9. Derby R, Eek B, Chen Y, et al. Intradiscal electrothermal annuloplasty (IDET): a novel approach for treating chronic discogenic back pain. Neuromodulation. 2000;3(2):82-88.
10. Wheeler AH, Murrey DB. Chronic lumbar spine and radicular pain: pathophysiology and treatment. Curr Pain Headache Rep. April 2002;6:97-105.
11. Manchikanti L, Singh V. Epidural lysis of adhesions and myeloscopy. Curr Pain Headache Rep. 2002;6:427-435.
12. Gasinski P, Radek M, Jozwiak J, Lyczak P. Peridural fibrosis in lumbar disc surgery—pathogenesis, clinical problems and prophylactic attempts [in Polish]. Neurol Neurochir Pol. 2000;34:983-993.
13. Wang JC, Lin E, Brodke DS, Youssef JA. Epidural injections for the treatment of symptomatic lumbar herniated discs. J Spinal Disord Tech. August 2002;15:269-272.
14. Vad VB, Bhat AL, Lutz GE, Cammisa F. Transforaminal epidural steroid injections in lumbosacral radiculopathy: a prospective randomized study. Spine. January 2002;27:11-16.
15. Botwin KP, Gruber RD, Bouchlas CG, et al. Fluoroscopically guided lumbar transformational epidural steroid injections in degenerative lumbar stenosis: an outcome study. Am J Phys Med Rehabil. 2002;81:898-905.
16. North RB, Wetzel FT. Spinal cord stimulation for chronic pain of spinal origin: a valuable long-term solution. Spine. 2002;27:2584-2591.
17. Lamer TJ. Treatment of cancer-related pain: when orally administered medications fail. Mayo Clin Proc. 1994;69:473-480.
18. Wang JK, Nauss LA, Thomas JE. Pain relief by intrathecally applied morphine in man. Anesthesiology. February 1979;50:149-151.
Valery Mora. Chronic mechanical back pain: Strategies for intervention. JAAPA July 2004;17:12-16.
Copyright © 2004, Advanstar Medical Economics Healthcare Communications at Montvale, NJ 07645-1742. All rights reserved.
