Hospital Medicine

Back pain

Back pain

I. Problem / Condition.

Back pain is a challenging condition for hospitalists to treat given the usual chronicity of the disease and the episodic nature of care that is inherent with our specialty. Further, while back pain is extremely common, it rarely is a diagnosis that warrants hospitalization. However, the practitioner must recognize when, back pain represents a true neurologic emergency mandating urgent medical and surgical intervention. Back pain may also be a symptom related to a more serious systemic medical diagnosis that will need further inpatient or outpatient diagnostic work-up.

Back pain is an extremely common problem with a prevalence of 30% in developed countries. Low back pain is the second most frequent reason for patients to visit their primary care physicians and accounts for approximately 3% of all visits to the emergency room. These patients undergo imaging 45% of the time (30% have plain radiographs and 10% have computed tomography or magnetic resonance imaging as of 2006).

For most patients, back pain is a self-limiting disease of which 90% recover without sequelae. Ten percent of patients will develop chronic back pain (variably defined as more than 2 months of symptoms). Risk factors for chronic back pain are broad and include physiologic factors such as: female sex, advanced age, obesity; lifestyle factors such as: sedentary lifestyle, physically strenuous work, tobacco abuse; and psychological factors including job dissatisfaction, worker’s compensation insurance, anxiety, and depression.

While most patients will be discharged directly from the emergency room (ER), a subset of patients will need to be admitted.

There are five broad indications for inpatient admission which include the following

⦁ Cauda equina syndrome, indicated by one or more of the following: bowel dysfunction, bladder dysfunction, saddle anesthesia, bilateral lower extremity neurologic abnormality⦁ Progressive or severe neurologic deficit⦁ Spine fracture with damage to the vertebral column or spinal cord⦁ Severe pain or functional deficit that cannot be treated as an outpatient⦁ Surgery for mass, neoplasm, epidural abscess, aortic dissection, or osteomyelitis.

II. Diagnostic Approach.

A. What is the differential diagnosis for this problem?

The differential diagnosis for back pain includes three distinct categories: mechanical, systemic non-mechanical and referred pain.

Mechanical causes include idiopathic muscular skeletal back pain, spondylosis (degenerative osteoarthritis of the joints between spinal vertebra and neural foraminae), compression fractures, spinal stenosis, traumatic fractures, disk herniation of the nucleus pulposus, and congenital alignment disorders which include most commonly kyphosis, scoliosis and spondylolisthesis.

Systemic non-mechanical causes include malignancy, infectious conditions such as vertebral discitis and osteomyelitis, inflammatory spondyloarthropathy which include ankylosing spondylitis, psoriatic spondylitis, Reiter's syndrome, and inflammatory bowel disease. Other less common causes include osteochondrosis (Scheuermann’s disease) and Paget’s disease of the bone.

Referred pain is the broadest and non-specific category. It includes but is not limited to aortic abdominal aneurysm, pelvic disease (prostatitis, endometriosis, pelvic inflammatory disease), renal disease (nephrolithiasis, pyelonephritis, perinephric abscess), and gastrointestinal disease (pancreatitis, cholecystitis, peptic or duodenal ulcer).

B. Describe a diagnostic approach / method to the patient with this problem.

The diagnosis of acute back pain divides the disease into two categories: back pain with suspected nerve root involvement and back pain that exists without the presence of sciatica. This differential should be made with close attention to whether the pain is likely to be related to a systemic or non-systemic medical condition.

Nerve root involvement is usually associated with sciatica, defined as a sharp or burning pain that radiates down the posterior or lateral aspect of the leg. Nerve root involvement may also be described as radicular, which is defined as impairment of a specific nerve root resulting in neuropathy. Typically, pain that radiates below the knee is more apt to represent true pathologic radiculopathy. The pain is often described by the patient as dull and aching and may be associated with numbness or tingling. Sciatica, if due to impingement is typically aggravated by maneuvers that increase pressure on the spinal cord such as coughing, sneezing and certain load bearing exercises including the Valsalva maneuver.

In the absence of sciatica, the patient can generally be discharged directly from the ER because the etiology is likely to be musculoskeletal. This diagnosis is affirmed in patients who are young (less than 50), without a history of cancer and without signs or symptoms of systemic disease. In these patients there is little value in imaging studies, but plain films may be considered. A C-reactive protein (CRP), or erythrocyte sedimentation rate (ESR), may be ordered if there is concern that an inflammatory or malignant process is ongoing. Age greater than 50, coupled with systemic signs or symptoms such as weight loss, fevers and hematuria, would increase the probability of such systemic involvement. In these cases, there is an indication for further imaging.

If sciatica is present, the hospitalist must consider more urgent diagnosis if the following present: urinary retention, bilateral sciatica, saddle anesthesia or bilateral motor findings. This would suggest cauda equina syndrome, a disorder caused by a herniated disc or impinging tumor. When this diagnosis is suspected, immediate imaging by magnetic resonance imaging (MRI) or computed tomography (CT) is mandated in conjunction with an emergent neurosurgical consult.

If radiculopathy is present without bilateral findings or bowel or bladder incontinence, then the hospitalist should perform plain films and consider an ESR / CRP if there is suspicion of osteomyelitis or discitis. If these findings are normal, a more conservative approach should be considered for at least 1 month. This will require close coordination of follow-up with the primary care physician. However, if an inflammatory marker is positive or the neurologic symptoms are progressing, the hospitalist should move directly to CT or MRI imaging of the spine.

1. Historical information important in the diagnosis of this problem.

The history should focus on the nature of the pain as well factors that worsen or alleviate it. Most specifically all patients should be asked if they have focal neurologic deficit with attention to its chronicity.

A hospitalist should be aware of the commonly accepted “red flags” that are suggestive of a serious underlying cause of low back pain. Questions concerning the possibility of malignancy include a prior history of cancer, age > 70, unexplained weight loss, the absence of relief when lying flat, or pain > 4-6 weeks in duration despite standard therapy.

The patient should be asked questions that might suggest the possibility of discitis or osteomyelitis including a history of IVDA, unexplained fever, recent infections including bacteremia, immunosuppression, skin or soft tissue infections, or a urinary tract infection (UTI).

Questions that were specific to the possibility of compression fractures would include advanced age with mild trauma, significant trauma in the younger patient and osteoporosis, particularly in the presence of chronic glucocorticoids usage.

It is common for hospitalists to treat patients with back pain who have opioid dependency or other non-organic causes of exaggerated back pain. In these cases, the physician should use questions aimed at exposing symptoms which suggest nonorganic pain. These would include pain at the tip of the tailbone, whole-leg pain or weakness in a global distribution, sudden give-way weakness of the leg, absence of periods without any relief of pain, previous failure or intolerance of multiple treatment regimens, and frequent visits to urgent centers or hospitals in the past.

2. Physical Examination maneuvers that are likely to be useful in diagnosing the cause of this problem.

A basic physical examination should include inspection of the back for alignment, curvature, range of motion, and also include palpitation for bony and soft tissue tenderness. Bony vertebrae tenderness is not specific but is sensitive in assessing for spinal infection. Soft tissue tenderness is poorly reproducible and is of limited value in diagnosis.

An essential maneuver is the straight leg test which is used to diagnosis radiculopathy. It is performed with the patient in the supine position. The patient's extended leg is raised with the ankle dorsiflexed. The test is positive when sciatica is reproduced between 30 and 70 degrees. It is 91% sensitive and 26% specific. The crossed straight leg raising test is performed by raising the unaffected leg and is positive when sciatica occurs in the affected leg. It is 29% sensitive and 88% specific.

Neurologic testing in suspected disc herniation should focus on the L5 and S1 nerve root region given that the vast majority of impingement will occur in this distribution. L5 testing should evaluate the strength of the ankle and great toe in dorsiflexion. Sensation for L5 should assess for numbness in the medial foot and between the first and second toe.

Diminished ankle reflexes, calf strength and sensation of the posterior calf and lateral side of the foot are localized to a S1 compression. As ankle reflexes diminish with age it is important to compare both the affected and unaffected ankle as unilateral absence of reflex is more specific in the elderly population.

Waddell and colleagues published the gold standard examination techniques utilized to unmask nonorganic back pain and they include the following: superficial tenderness over the lumbar region to light touch, non-anatomic tenderness, exacerbation of pain by applying a few pounds of pressure with the hands to the top of the head, exacerbation of pain by simulated rotation of the spine, inability to sit up straight from a supine position, intolerance of the straight-leg-raising test, and non-anatomic distribution of sensory changes.

3. Laboratory, radiographic and other tests that are likely to be useful in diagnosing the cause of this problem.

For the diagnosis of back pain there are limited useful laboratory tests unless an underlying systemic or infectious cause is suspected. More specifically, if the diagnosis of vertebral abscess, discitis or osteomyelitis is considered, the testing should include a complete blood count (CBC), ESR or CRP and blood cultures.

Various studies cite the sensitivity for ESR and C-reactive protein for osteomyelitis to be between 70% and 95%. A CBC is not sensitive for this condition. An ESR and CRP may be useful if the back pain is > 4 weeks duration and the diagnosis of systemic malignancy is considered. If a connective tissue disorder is suspected, then the appropriate serum antibodies and a rheumatoid factor would be indicated. Urinalysis and urine culture should be part of the diagnostic work-up if referred pain from renal colic or pyelonephritis is being ruled out.

Imaging for back pain includes either plain films, CT or MRI, and less commonly myelogram. It is unusual for a patient to be admitted to a hospital without at least one of these modalities being performed in the ER. The utility of these tests is questionable in the absence of signs of symptoms of a more serious underlying systemic condition. Some guidelines allow that older patients should not wait 4 to 6 weeks for imaging, in contrast to younger adults, however, a recent study does not suggest better outcomes with early imaging at one year.

A meta-analysis of patients who underwent radiographic imaging for the diagnosis of acute or subacute back pain without serious indications of underlying systemic condition did not demonstrate improved outcomes at up to 3 months or at 6-9 months.

Numerous studies have shown that approximately a quarter of asymptomatic patients will be found to have radiographic findings such as disc herniation, spinal stenosis or degenerative arthritis. Further, even when symptoms are consistent with the radiographic results, there is limited evidence that suggest these findings will correlate with clinical outcomes.

Plain X-rays can provide evidence of infection, trauma, malignancy, spondylolisthesis, and degenerative changes. They are not useful at demonstrating anatomical changes in the spinal cord. In patients <50 years of age without history or trauma or signs or symptoms of system disease there is no indication for plain X-ray. For patients >50 years of age or those with findings suggestive of systemic disease, plain X-ray with an ESR or CRP is appropriate.

MRI is the best test for diagnosing pathologic conditions because of its enhanced resolution. It is highly specific and sensitive for detecting spinal metastases and spine infections. The addition of gadolinium is helpful in distinguishing scar from disc in patients who have had previous surgery. Gadolinium is contraindicated in patients with renal dysfunction as defined by a glomerular filtration rate (GFR) less than 30mL/min or those currently on hemodialysis because of the risk of a serious condition known as nephrogenic systemic fibrosis (NSF).

CT is the preferred test for demonstrating bone abnormalities such as fractures, congenital abnormalities, spondylolisthesis, degenerative changes, and sacroiliac joint disease.

CT-myelography, which is an invasive procedure, may have use when MRI studies are inconclusive in patients with previous surgery or multi-level radiculopathy, or if there exists a contraindication to MRI (cardiac pacemaker or other metal object). In most other instances MRI has replaced CT-myelography as the diagnostic test of choice.

C. Criteria for Diagnosing Each Diagnosis in the Method Above.

Listed below are the more common or emergent causes of back pain a hospitalist may encounter with attention to basic criteria utilized to make the diagnosis.

EMERGENT/URGENT

Cauda equina syndrome

Suspicion is raised based on a history of bowel or bladder dysfunction, bilateral sciatica or saddle anesthesia. The primary cause is metastatic tumor. The physical exam may validate the history with findings of anal sphincter weakness and focal neurologic deficits. The diagnosis is confirmed with CT or MRI imaging.

Vertebral discitis or osteomyelitis

Key findings may include fever, pain that is insidious in onset, local tenderness to the spine, elevated ESR or CRP, and positive blood cultures. MRI is the most sensitive radiographic technique.

NON-EMERGENT

Musculoskeletal sprain or strain

This is a diagnosis of exclusion made by ruling out more serious systemic disease that should not require hospitalization in most instances.

Herniated nucleus pulposus (HNP)

Patients present with acute lumbar radiculopathy and back pain due to the rupture of the nucleus pulposus into the intervebral space. MRI will demonstrate disk protrusion, nerve root impingement or thecal sac compression. If there is acute neurologic deficit, urgent neurosurgical evaluation is required.

Spinal stenosis

Hospitalists who admit elderly patients with radicular pain should be particularly attuned to the diagnosis of spinal stenosis. This is a mechanical disease process that may involve the spinal canal, nerve roots or intervertebral foramina. The patient generally has a subacute history of lumbar back pain and sciatica. Less commonly they may have ambulatory induced pain (“neurogenic claudication”) which can be difficult to differentiate from. The most common and pathognomonic finding is relief of pain with sitting or other spinal flexion.

Compression fractures

This is a diagnosis found in the advanced age population, particularly those with long-term corticosteroid use. While the patient may be asymptomatic, with the disease being identified as an incidental finding on X-ray, some patients do report acute onset of back pain during traumatic activities. Generally, the exam will not demonstrate neurologic deficit.

D. Over-utilized or “Wasted” Diagnostic Tests Associated with the Evaluation of This Problem.

See above.

III. Management while the Diagnostic Process is Proceeding.

A. Management of back pain.

Management of lower back pain is etiology-specific and, in the absence of a neurologic emergency, is usually accomplished with outpatient-based treatment. Treatment of non-emergency back pain should generally be conservative.

Patients generally do not benefit from bed rest so increased mobility should be recommended (Grade 1A). A physical therapy referral is often recommended. Local treatment with either ice or heat is sometimes efficacious. First-line medications include acetaminophen and NSAIDs (Grade 2B). Muscle relaxants have not been proven to be more efficacious than placebo but are often prescribed (2C). Opioids are often prescribed for severe pain and may be infrequently indicated in acute severe pain but the risk of dependence and the limited efficacy over other medications must be considered. A brief overview follows.

EMERGENT/URGENT

Cauda equina syndrome

The hospitalist should initiate corticosteroids in all patients although there is debate as to whether low dose is as efficacious as high dose. Further treatment may include surgery and external beam radiation therapy (RT) as directed by a multidisciplinary team led by a neurosurgeon and radiation oncologist. Median survival for non-ambulatory patients is approximately 6 months and for those who regain ambulatory function median survival is 1 year.

Vertebral discitis or osteomyelitis

No randomized trials exist to direct the optimal antibiotic regimens for vertebral osteomyelitis. Staphylococcus aureus is the most common cause of pyogenic vertebral osteomyelitis followed by E. coli. After spinal surgery, iatrogenic causes include Coagulase-negative staphylococci and Propionibacterium acnes. Treatment should be chosen based on the identified microorganism and its susceptibility.

While prompt administration of antibiotics is essential, especially for those who are hospitalized with neurological compromise or signs of SIRs or sepsis, it is essential to obtain blood cultures and often bone biopsy to direct treatment. If antibiotics are needed emergently, empiric therapy usually includes vancomycin and a beta-lactam.

In most cases a hospitalist should seek infectious disease consultation to assist in managing this condition. Surgery is needed in a minority of cases but neurosurgical consultation should be sought if there is progression of the disease despite antimicrobial treatment, threatened or actual cord compression, or associated epidural abscess.

NON-EMERGENT

Musculoskeletal sprain or strain

Hospitalists should facilitate the prompt discharge of patients who were admitted for this condition. Standard medications include: NSAIDS, acetaminophen or opioids. Prescriptions for opioids should be used cautiously as studies do not suggest significantly different efficacy to NSAIDs or acetaminophen. Adjunct therapy may include muscle relaxants in selected populations. Some patients should be referred to outpatient physical therapy.

Herniated nucleus pulposus

Unless evidence of cauda equina syndrome exists, these patients can be treated conservatively with prompt referral to their primary care physician for further management. First-line therapy is NSAIDs or acetaminophen. Those with prominent radicular pain or severe back pain may need adjunctive therapy with oral opioids, corticosteroids, anticonvulsants (gabapentin or pregabalin) and muscle relaxants. For patients > 2 weeks of pain who do not get significant response to the aforementioned treatment, lumbar epidural corticosteroid injection can be considered (Grade 2B).

Spinal stenosis

Physical therapy is the mainstay of treatment and a consultation should be obtained in all admitted patients. Bed rest should be avoided, but patients should be advised to avoid bending, lifting or load bearing until the pain has improved. Usual pharmaceutical therapy includes acetaminophen or NSAIDs. If acutely there is no relief of pain, a short course of low-dose systemic steroids may provide benefit.

Epidural corticosteroid injections may provide benefit, particularly in patients suffering from radicular pain, although more recent evidence suggests the addition of steroids to lidocaine offered minimal or no short-term benefit compare to lidocaine alone. Surgery is rarely indicated acutely but may be needed if conservative therapy provides no relief after 3 to 6 months. Most patients will need referral as an outpatient to a neurosurgeon if they do not respond to conservative treatment and are surgical candidates. The North American Spine Society provides an evidenced-base review of treatment options.

Compression fractures

Treatment depends on the extent of the fracture. Normally the fracture only involves the anterior spinal column and does not compromise the stability of the spine. In these cases, limited bed rest and analgesia, followed by early mobilization, potentially with orthosis, is indicated. Treatment of any underlying osteoporosis is also indicated. Surgical intervention (vertebroplasty, kyphoplasty or open surgical reconstruction) is generally not needed unless the middle and/or the posterior columns are also involved, or there is >30° kyphosis or severe chronic pain despite medical management.

However, there remains much controversy concerning the efficacy of surgical treatment. Two randomized trials that focused on patients with acute vertebral fractures demonstrated improved physical function and reduced pain in patients undergoing vertebroplasty or kyphoplasty. However, the comparison arm of both studies was usual care, rather than a sham procedure, so the potential of placebo bias existed. Another two randomized double-blinded trials did not show a difference in functional disability, pain, or quality of life between sham procedures and vertebroplasty.

Both vertebroplasty and kyphoplasty procedures are done under fluoroscopy and local anesthesia with the patient in the prone position, although sometimes kyphoplasty is accomplished under general anesthesia. Vertebroplasty utilizes cement that is injected directly into the fractured vertebra. In kyphoplasty, a balloon catheter is inflated into the fractured vertebra restoring its shape. Cement can then be injected under lower pressure than in a vertebroplasty.

B. Common Pitfalls and Side-Effects of Management of this Clinical Problem.

The most common and serious pitfall in the management of back pain is to miss a serious condition such as cauda equina syndrome, malignancy, fracture, or infection. Given the vast majority of back pain is far less serious, it is easy to underdiagnose these conditions unless a systemic approach is undertaken with each patient.

The history is used to risk-stratify patients. A history of trauma, age >50 and the use of chronic steroids is useful in identifying fracture. Systemic signs of infection, age >50, persistent pain even at rest, and an immunocompromised state may indicate discitis. Historical clues for malignancy are age >50, weight loss, pain worse at night, and pain >six weeks in duration. The pathognomonic sign of cauda equina syndrome is loss of bowel or bladder control as well as bilateral leg numbness and weakness.

A complete physical exam is crucial and is discussed above. The neurologic exam should include sensory to touch and pin-prick, motor examination, reflexes, and gait. A rectal exam is essential for patients in which cauda equina is being considered.

Side effects are usually related to medications. Perhaps the most common potentially preventable side effect is constipation for patients who are treated with opioids. These patients should always be given a bowel regimen including a laxative. The potential for dependency should be a concern for a hospitalist. When a patient is discharged, it is recommended that a conservative dose of opioids is prescribed, generally without a refill, with the patient being referred back to primary care for close follow-up.

IV. What's the evidence?

Friedman, BW, Chilstrom, M, Bijur, PE, Gallagher, EJ. "Diagnostic Testing and Treatment of Low Back Pain in United States Emergency Departments: A National Perspective". Spine. vol. 35. pp. E1406-E1411.

Waddell, G, Bircher, M, Finlayson, D, Main, CJ. "Symptoms and signs: Physical disease or illness behavior". BMJ (Clin Res Ed). vol. 289. 1984. pp. 739-741.

van Tulder, MW, Scholten, RJ, Koes, BW, Deyo, RA. "Non-steroidal anti-inflammatory drugs for low back pain". Cochrane Database Syst Rev. vol. 2. 2000. pp. CD000396.

Watters, WC, Baisden, J, Gilbert, TJ. "North American Spine Society. Degenerative lumbar spinal stenosis: an evidence-based clinical guideline for the diagnosis and treatment of degenerative lumbar spinal stenosis". Spine J. vol. 8. 2008. pp. 305-310.

Chandrasekar, PH. "Low-back pain and intravenous drug abusers". Arch Intern Med. vol. 150. 1990. pp. 1125.

Chou, R, Fu, R, Carrino, JA, Deyo, RA. "Imaging strategies for low-back pain: systematic review and meta-analysis". Lancet. vol. 373. 2009. pp. 463-72.

Lateef, H, Deepak, P. "What is the role of imaging in acute low back pain". Ann Intern Med. vol. 137. 2002. pp. 586-97.

"Practice parameters: Magnetic resonance imaging in the evaluation of low back syndrome (summary statement)". Neurology. vol. 44. 1994. pp. 767-770.

Ensrud, KE, Schousboe, T. "Vertebral Fractures. N Engl ". Med. vol. 364. 2011. pp. 1634-1642.

Jeffrey, J. "Association of Early Imaging for Back Pain with Clinical Outcomes in Older Adults". JAMA. vol. 313. 2015. pp. 1143-1153.

Friedly, J. "A Randomized Trial of Epidural Glucocorticoids Injections for Spinal Stenosis". N Eng J Med. vol. 371. 2014. pp. 11-21.

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