9.06 Acute Lumbar Strain (“Mechanical” Low Back Pain, Sacroiliac Dysfunction)

agk’s Library of Common Simple Emergencies

Presentation

Suddenly or gradually after lifting, sneezing, bending, or other movement the patient develops a steady pain in one or both sides of the lower back. At times, this pain can be severe and incapacitating. It is usually better on lying down, worse with movement, and will perhaps radiate around the abdomen or down the thigh, but no farther. There is insufficient trauma to suspect bony injury (e.g., a fall or direct blow); and no evidence of systemic disease which would make bony pathology likely (e.g., osteoporosis, metastatic carcinoma, multiple myeloma). On physical examination, there may be spasm (i.e., contraction which does not relax, even when the patient is supine or when the opposing muscle groups contract, as with walking in place) in the paraspinous muscles; but there is no point tenderness over the spinous processes of lumbar vertebrae and no nerve root signs such as pain or paresthesia in dermatomes below the knee (especially with straight leg raising), foot weakness, or loss of the ankle jerk. There may be point tenderness to firm palpation or percussion over the sacroiliac joint, especially if the pain is on that side.

What to do:

• Perform a complete history and physical examination of the abdomen, back, and legs, looking for alternative causes for the back pain.
• Consider plain x rays of the lumbosacral spine of those who have suffered injury sufficient to cause bony injury, patients under the age of 20 or over 50 who have had pain more than a month, and patients who are on long term corticosteroid medication or have a history of cancer.
• Order an erythrocyte sedimentation rate (ESR) on patients with a history of cancer or intravenous drug abuse or signs or symptoms of underlying systemic disease (e.g., unexplained weight loss, fatigue, night sweats, fever, lymphadenopathy, and back pain at night or unrelieved by bed rest).
• For point tenderness over a sacroiliac joint with no neurologic findings to suggest nerve root compression, try an intraarticular injection of a local anesthetic mixed with a corticosteroid. Improvement of pain is both diagnostic and therapeutic. Draw up 10 mL of 0.5% bupivacaine (Marcaine, Sensorcaine) mixed with 1 mL (40 mg) of methylprednisolone (DepoMedrol) or 1-2 mL (6-12 mg) of betamethasone (Celestone, Soluspan). Using a 1.5" 25 gauge needle and sterile technique, inject deeply into the sacroiliac joint at the point of maximal tenderness or into the dimple immediately lateral to the sacrum. When the needle is in the joint there should be a free flow of medication from the syringe without causing soft tissue swelling. During the injection, the patient may feel a brief increase of pain, followed by dramatic relief in 5-20 minutes which is usually permanent.
• For point tenderness of the lumbosacral muscles, inject 10-20 mL of 0.25-0.5% bupivicaine (Marcaine, Sensorcaine) deeply into the points of maximal tenderness of the erector spinae and quadratus lumborum muscles, using a 1.5-3.5" 25 gauge needle. Quickly puncture the sin, drive the needle into the muscle belly and inject the anesthetic, slowly advancing or withdrawing, fanning out the medication. Often one fan block can reduce symptoms by 95% after injection and yield a 75% permanent reduction of painful spasms. Following injection, teach stretching exercises.
• For severe pain that cannot be relieved by injections of local anesthetic, it may be necessary to provide the patient with one to two days of bed rest, although the majority of patients with acute low back pain recover more rapidly with continuing ordinary activities within the limits permitted by their pain than with bed rest or back-mobilizing exercises.
• Consider disk herniation when leg pain overshadows the back pain. Back pain may subside as leg pain worsens. Look for weakness of ankle or great toe dorsiflexion and sensory changes over the medial dorsal foot with compression of the fifth lumbar nerve root or weak plantarflexion, diminished ankle reflex and paresthesias of the lateral foot with the first sacral root. Raise each leg thirty degrees from the horizontal and consider the test positive for nerve root compression if it produces pain down the leg along a nerve root distribution rather than pain in the back, increased by dorsiflexion of the ankle and relieved by plantarflexion. Ipsilateral straight leg raising is a moderatively sensitive but not a specific test – a herniated intervertebral disk is more strongly indicated when radicular pain is reproduced in one leg by raising the opposite leg. Prescribe short term bed rest and non-steroidal anti-inflammatory analgesics and arrange for general medical, orthopedic or neurosurgical referral. Some consultants recommend short term corticosteroid treatment such as prednisone 50 mg qd x5 days. The patient shound try four to six weeks of conservative treatment before submitting to an operation on the herniated disk. Eighty per cent of patients with sciatica recover with or without surgery. The rare cauda equina syndrome is the only complication of lumbar disk herniation that calls for emergent surgical referral. It occurs when a massive extrusion of disk nucleus compresses the caudal sac containing lumbar and sacral nerve roots, producing bilateral radicular leg pain or weakness, bladder or bowel dysfunction, perineal or perianal anesthesia, decreased rectal sphincter tone in 60-80% and urinary retention in 90%.
• Prescribe a short course of anti-inflammatory analgesics (aspirin, ibuprofen, naprosyn) for patients who are not already taking NSAIDs. Because gastric bleeding and renal insufficiency are common with long-term use of NSAIDs, consider substituting acetaminophen or salsalate.
• Prescribe ice to the acutely injured area, 20 minutes per hour for the first day . (This therapy is unconventional, but works as well as it does for any other musculoskeletal injury.)
• Refer patients with uncomplicated back pain to their primary care provider for follow up care in three to seven days. Reassure them that back pain is seldom disabling and that it usually resolves with their return to normal activity. Tell them that cigarette smoking, sedentary activity and obesity are risk factors for back pain. Teach them to avoid twisting and bending when lifting and show them how to lift with the back vertical, using thigh muscles and holding heavy objects close to the chest, to avoid re-injury.

What not to do:

• Do not be eager to use narcotic pain medicines. The sensation of pain from an acute musculoskeletal injury reminds the patient not to use the damaged part and exacerbate the injury, but instead to keep it at rest and speed healing. Narcotics are also apt to make the patient constipated, and straining at stool can be especially uncomfortable with a back injury.
• Do not be too eager to use anti-spasm medicines. Many have sedative or anticholinergic side effects.
• Do not apply lumbar traction. It has not been proven any better than placebo for releiving back pain.

Discussion

Low back pain is a common and sometimes chronic problem which accounts for an enormous amount of disability and time lost from work. The approach discussed above is geared only to the management of acute injuries and flareups, from which most people recover on their own, only about 10% developing chronic problems. With acute pain, reassurance plus limited medication may be the most useful intervention.

History and physical examination are essential to rule out serious pathologic conditions which can present as low back pain but which require quite different treatment – aortic aneurysm, pyelonephritis, pancreatitis, pelvic inflammatory disease, ectopic pregnancy, retroperitoneal or epidural abscess.

The standard five-view x ray study of the lumbosacral spine may entail 500 mrem and only 1 in 2500 lumbar spine plain films of adults below age 50 show an unexpected abnormality. In fact, many radiographic anomalies such as spina bifida occulta, single-disk narrowing, spondylosis, facet joint abnormalities and several congenital anomalies are equally common in symptomatic and asymptomatic individuals. It is estimated that the gonadal dose of radiation absorbed from a five-view lumbosacral series is equivalent to that from six years of daily anterioposterior and lateral chest films. The World Health Organization now recommends that oblique views be reserved for problems remaining after review of AP and lateral films. For simple cases of low back pain, even with radicular findings, both CT and MRI are overly sensitive and often reveal anatomic abnormalities that have no clinical significance.

While adults are more apt to have disk abnormalities, muscle strain and degenerative changes associated with low back pain, athletically active adolescents are more likely to have posterior element derangements like stress fractures of the pars interarticularis. Early recognition of this spondylolysis and treatment by bracing and limitation of activity may prevent nonunion, persistant pain and disability.

Malingering and drug seeking are major psychological components to consider in patients who have frequent ED visits for back pain and whose responses seem overly dramatic of otherwise inappropriate. These patients may move around with little difficulty when they do not know they are being observed. They may complain of generalized superfician tenderness when you lightly pinch the skin over the affected lumbar area. If you are suspicious that the patient's pain is psychosomatic or nonorganic you can use the axial loading test, in which you gently press down on the head of the standing patient. This should not cause significant musculoskeletal back pain. You can also perform the rotation test, in which the patient stands with his arms at his sides. Hold his wrists next to his hips and turn his body from side to side, passively rotating his shoulders, trunk and pelvis as a unit. This maneuver creates the illusion that you are testing spinal rotation, but in fact you have not altered the spinal axis and any complainst of back pain should be suspect.

References:

• Deyo RA, Diehl AK, Rosenthal M: How many days of bed rest for acute low back pain? N Eng J Med 1986;315:1064-1070.
• Deyo RA, Rainville J, Kent DL: What can the history and physical examination tell us about low back pain? J Am Med Assoc 1992;268:760-765.
• Malmivaara A, Hakkinen U, Aro T et al: The treatment of acute low back pain: bed rest, exercise, or ordinary activity? N Eng J Med 1995;332:351-355.
• Carey TS, Garrett J, Jackman A et al: The outcomes and costs of care for acute low back pain among patients seen by primary care practitioners, chiropracters and orthopedic surgeons. N Eng J Med 1995;333:913-917.
• Elam KC, Cherkin DC, Deyo RA: How emergency physicians approach low back pain: choosing costly options. J Emerg Med 1995;13:143-150.

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