Background
Mechanical low back pain is one of the most common patient complaints expressed to emergency physicians in the United States accounting for more than 6 million cases annually. Approximately two thirds of adults are affected by mechanical low back pain at some point in their lives, making it the second most common complaint in ambulatory medicine and the third most expensive disorder in terms of health care dollars spent surpassed only by cancer and heart disease.[1]
Low back pain reportedly occurs at least once in 85% of adults younger than 50 years, and 15-20% of Americans have at least one episode of back pain per year. Of these patients, only 20% can be given a precise pathoanatomic diagnosis. Low back pain affects men and women equally. The onset most frequently occurs in people aged 30-50 years. Low back pain is the most common and most expensive cause of work-related disability in the United States.[2] Smokers appear to have an increased incidence of back pain compared with nonsmokers. Furthermore, the incidence of current smoking and the association with low back pain is higher in adolescents than in adults.[3]
Pathophysiology
Many causes of mechanical low back pain exist. The most common causes are age-related degenerative disc and facet processes and muscle- or ligament-related injuries. Discussion in this article is limited to musculoskeletal causes. These can be divided into nerve root syndromes, musculoskeletal pain syndromes, and skeletal causes.
Nerve root syndromes
Classic nerve root syndrome is characterized by radicular pain arising from nerve root impingement due to herniated discs. A similar syndrome can also be produced by inflammation and irritation, which may explain why patients whose presentation is consistent with this diagnosis respond to conservative therapies.
Impingement pain tends to be sharp, well localized, and can be associated with paresthesia, whereas irritation pain tends to be dull, poorly localized, and without paresthesia. Impingement is associated with a positive straight leg raising sign (ie, shooting pain down contralateral leg with leg raising), while irritation is not. Neurologic deficits and pain radiation below the knee are rarely seen in irritation alone and are most commonly found with impingement.[4]
The cause of impingement syndrome is most commonly herniated discs, but it may also be caused by spinal stenosis, spinal degeneration, or cauda equina syndrome.
Herniated discs are produced as spinal discs degenerate. After growing thinner, the nucleus pulposus herniates out of the central cavity against a nerve root. Intervertebral discs begin to degenerate by the third decade of life, and herniated discs are found on autopsy in one third of adults older than 20 years. Only 3% of these, however, are symptomatic.[5] The most common locations for herniation are L4, L5, and S1.[6]
Spinal stenosis occurs when disc spaces decrease as intervertebral discs lose moisture and volume with age. Even minor trauma under these circumstances can cause inflammation or nerve root impingement, which can produce classic sciatica pain without disc rupture. The pain can often be bilateral.[7]
Spinal degeneration is caused by alterations in the hygroscopic quality of the nucleus pulposus. This process progresses to annular degeneration. Coupled with progressive posterior facet disease, this process leads to spinal canal or foraminal encroachment. These retrogressive and proliferative changes in the disc anteriorly and the joints posteriorly produce clinical symptoms and radiographic findings termed 3-joint complex degeneration. Spinal degeneration has 3 distinct stages, as follows:
- Dysfunction with complaints of pain only
- Instability with advanced degeneration, pseudospondylolisthesis, and neurologic abnormalities
- Stabilization with morning stiffness and with prolonged standing or walking, producing radicular pain
Cauda equina syndrome is produced by massive midline extrusion of nuclear material or tumor into the spinal canal, which compresses the caudal sac. The classic presentation is bilateral sciatica, with lower extremity bowel or bladder dysfunction present in 90% of patients. Urinary retention is initially observed and followed by overflow incontinence. Perineal or perianal anesthesia is present in 60-80% of patients.[8]
Musculoskeletal pain syndromes
Musculoskeletal pain syndromes that produce low back pain include myofascial pain syndromes and fibromyalgia.
Myofascial pain is characterized by pain and tenderness over localized areas (trigger points), loss of range of motion in the involved muscle groups, and pain radiating in a characteristic distribution but restricted to a peripheral nerve. Relief of pain is often reported when the involved muscle group is stretched.
Fibromyalgia results in pain and tenderness on palpation of 11 of 18 trigger points, one of which is the low back area, as classified by the American College of Rheumatology. Generalized stiffness, fatigue, and muscle ache are reported.
Other skeletal causes
Other skeletal causes of low back pain include osteomyelitis, sacroiliitis, and malignancy.
Osteomyelitis results from infectious processes involving the bones of the spine, while sacroiliitis results from inflammatory changes in the sacroiliac joints. This pain presents over the sacroiliac joints and radiates to the anterior and posterior thighs. This pain is usually worse at night and is exacerbated by prolonged sitting or standing.
Malignant tumors of the spine can be primary or metastatic. Most primary spinal tumors are found in patients younger than 30 years and usually involve the posterior vertebral elements. Metastatic tumors are found mostly in patients older than 50 years and tend to occur in the anterior aspects of the vertebral body.[9]
Epidemiology
Frequency
United States
Mechanical low back pain is one of the most common patient complaints expressed to emergency physicians in the United States accounting for more than 6 million cases annually.
Mortality/Morbidity
- Most etiologies of mechanical low back pain are not life threatening; however, significant morbidity is associated with chronic low back pain syndromes.
- A significant number of patients are unable to return to their normal daily routines or function in a productive work environment secondary to low back pain.[2]
- Most cases of back pain treated in the emergency department are not true emergencies, with the exception of cauda equina syndrome. Patients who have cauda equina syndrome must undergo surgical decompression as soon as possible or face permanent neurologic damage.
Race
No differences exist in incidence of back pain between racial groups.
Sex
Both male and female populations are affected; however, there is a tendency towards a higher incidence in male patients.
Age
Low back pain is a common complaint in adults of all ages, and it is becoming an increasing complaint in children and adolescents. A study following children from age 14 years into adulthood suggests that obesity in childhood, particularly in females, is a risk factor for later hospitalization for sciatica. This study also reported an increased risk of hospitalization for sciatica in males who smoked at a young age.[10]
Kinkade S. Evaluation and treatment of acute low back pain. Am Fam Physician. Apr 15, 2007;74(8):1181-8. [Medline].
Atlas SJ, Chang Y, Kammann E, Keller RB, Deyo RA, Singer DE. Long-term disability and return to work among patients who have a herniated lumbar disc: the effect of disability compensation. J Bone Joint Surg Am. Jan 2000;82(1):4-15. [Medline].
Shiri R, Karppinen J, Leino-Arjas P, Solovieva S, Viikari-Juntura E. The association between smoking and low back pain: a meta-analysis. Am J Med. Jan 2010;123(1):87.e7-35. [Medline].
Deyo RA, Rainville J, Kent DL. What can the history and physical examination tell us about low back pain?. JAMA. Aug 12 1992;268(6):760-5. [Medline].
Boden SD, Davis DO, Dina TS, Patronas NJ, Wiesel SW. Abnormal magnetic-resonance scans of the lumbar spine in asymptomatic subjects. A prospective investigation. J Bone Joint Surg Am. Mar 1990;72(3):403-8. [Medline].
Hadjipaviou AG, Tzermiadianos MN, Bogduk N, Zindrick MR. The pathophysiology of disc degeneration: a critical review. J Bone Joint Surg Br. Oct 2008;90(10):1261-70. [Medline].
van Tulder M, Koes B. Low back pain and sciatica (chronic). Clin Evid. Dec 2003;(10):1359-76. [Medline].
Deyo RA, Weinstein JN. Low back pain. N Engl J Med. Feb 1 2001;344(5):363-70. [Medline].
Borenstein D. Epidemiology, etiology, diagnostic evaluation, and treatment of low back pain. Curr Opin Rheumatol. Mar 1996;8(2):124-9. [Medline].
Rivinoja AE, Paananen MV, Taimela SP, Solovieva S, Okuloff A, Zitting P, et al. Sports, Smoking, and Overweight During Adolescence as Predictors of Sciatica in Adulthood: A 28-Year Follow-up Study of a Birth Cohort. Am J Epidemiol. Apr 15 2011;173(8):890-7. [Medline].
Marriott A, Newman NM, Gracovetsky SA, Richards MP, Asselin S. Improving the evaluation of benign low back pain. Spine. May 15 1999;24(10):952-60. [Medline].
van der Windt DA, Simons E, Riphagen II, Ammendolia C, Verhagen AP, Laslett M, et al. Physical examination for lumbar radiculopathy due to disc herniation in patients with low-back pain. Cochrane Database Syst Rev. Feb 17 2010;2:CD007431. [Medline].
Frank AO, De Souza LH, McAuley JH, Sharma V, Main CJ. A cross-sectional survey of the clinical and psychological features of low back pain and consequent work handicap: use of the Quebec Task Force classification. Int J Clin Pract. Dec 2000;54(10):639-44. [Medline].
de Schepper EI, Damen J, van Meurs JB, Ginai AZ, Popham M, Hofman A, et al. The association between lumbar disc degeneration and low back pain: the influence of age, gender, and individual radiographic features. Spine (Phila Pa 1976). Mar 1 2010;35(5):531-6. [Medline].
Lurie JD. What diagnostic tests are useful for low back pain?. Best Pract Res Clin Rheumatol. Aug 2005;19(4):557-75. [Medline].
Kuritzky L. Current management of acute musculoskeletal pain in the ambulatory care setting. Am J Ther. Nov-Dec 2008;Suppl 10:S7-11. [Medline].
van Tulder MW, Koes BW, Bouter LM. Conservative treatment of acute and chronic nonspecific low back pain. A systematic review of randomized controlled trials of the most common interventions. Spine. Sep 15 1997;22(18):2128-56. [Medline].
Cherkin D, Sherman KJ. Conceptualization and evaluation of an optimal healing environment for chronic low-back pain in primary care. J Altern Complement Med. 2004;10 Suppl 1:S171-8. [Medline].
Nelson L, Aspegren D, Bova C. The use of epidural steroid injection and manipulation on patients with chronic low back pain. J Manipulative Physiol Ther. May 1997;20(4):263-6. [Medline].
Moffett JK, Torgerson D, Bell-Syer S, Jackson D, Llewlyn-Phillips H, Farrin A, et al. Randomised controlled trial of exercise for low back pain: clinical outcomes, costs, and preferences. BMJ. Jul 31 1999;319(7205):279-83. [Medline].
[Best Evidence] Sertpoyraz F, Eyigor S, Karapolat H, Capaci K, Kirazli Y. Comparison of isokinetic exercise versus standard exercise training in patients with chronic low back pain: a randomized controlled study. Clin Rehabil. Mar 2009;23(3):238-47. [Medline].
[Guideline] Chou R, Loeser JD, Owens DK, Rosenquist RW, Atlas SJ, Baisden J. Interventional therapies, surgery, and interdisciplinary rehabilitation for low back pain: an evidence-based clinical practice guideline from the American Pain Society. Spine. May 1 2009;34(10):1066-77. [Medline].
FDA News Release. FDA clears Cymbalta to treat chronic musculoskeletal pain. Available at http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm232708.htm. Accessed November 5, 2010.
Rubinstein SM, van Middelkoop M, Assendelft WJ, de Boer MR, van Tulder MW. Spinal manipulative therapy for chronic low-back pain. Cochrane Database Syst Rev. Feb 16 2011;2:CD008112. [Medline].
Hill JC, Whitehurst DG, Lewis M, Bryan S, Dunn KM, Foster NE, et al. Comparison of stratified primary care management for low back pain with current best practice (STarT Back): a randomised controlled trial. Lancet. Oct 29 2011;378(9802):1560-71. [Medline].
Hodges P, van den Hoorn W, Dawson A, Cholewicki J. Changes in the mechanical properties of the trunk in low back pain may be associated with recurrence. J Biomech. Jan 5, 2009;42(1):61-6.
Lotz JC. The biomechanics of prevention and treatment for low back pain: 2nd international workshop. Clin Biomech (Bristol, Avon). Mar 1999;14(3):220-3. [Medline].
Coste J, Delecoeuillerie G, Cohen de Lara A, Le Parc JM, Paolaggi JB. Clinical course and prognostic factors in acute low back pain: an inception cohort study in primary care practice. BMJ. Feb 26 1994;308(6928):577-80. [Medline].
Croft PR, Macfarlane GJ, Papageorgiou AC, Thomas E, Silman AJ. Outcome of low back pain in general practice: a prospective study. BMJ. May 2 1998;316(7141):1356-9. [Medline].
Chou R, Shekelle P. Will this patient develop persistent disabling low back pain?. JAMA. Apr 7 2010;303(13):1295-302. [Medline].
Kaspiris A, Grivas TB, Zafiropoulou C, Vasiliadis E, Tsadira O. Nonspecific low back pain during childhood: a retrospective epidemiological study of risk factors. J Clin Rheumatol. Mar 2010;16(2):55-60. [Medline].
Harris IA, Young JM, Rae H, Jalaludin BB, Solomon MJ. Factors associated with back pain after physical injury: a survey of consecutive major trauma patients. Spine. Jun 15 2007;32(14):1561-5. [Medline].
Panjabi MM. Clinical spinal instability and low back pain. J Electromyogr Kinesiol. Aug 2003;13(4):371-9. [Medline].
Spector LR, Madigan L, Rhyne A, Darden B 2nd, Kim D. Cauda equina syndrome. J Am Acad Orthop Surg. Aug 2008;16(8):471-9. [Medline].
Tauney PJW, Siegel CB, LaBan MM. Thoracic and lumbar pain syndromes. In: Tintinalli, et al, eds. Emergency Medicine: A Comprehensive Study Guide. 4th ed. 2000:1866-1873.
van Poppel MN, Hooftman WE, Koes BW. An update of a systematic review of controlled clinical trials on the primary prevention of back pain at the workplace. Occup Med (Lond). Aug 2004;54(5):345-52. [Medline].
Walsh MJ. Evaluation of orthopedic testing of the low back for nonspecific lower back pain. J Manipulative Physiol Ther. May 1998;21(4):232-6. [Medline].
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