Lumbar Strain

Definition

Lumbar strain is characterized by nonradiating low back pain associated with a mechanical stress or creating an abnormal position that puts the muscle beyond its limit.

Etiology

Lumbar strain may occur with physical stress (weight/torque) that is greater than the forces that can be supported by the muscular and ligamentous structures. Injury is more likely to occur if the lumbar spine is at a mechanically disadvantaged position, such as when rotated or fully flexed.

Epidemiology including risk factors and primary prevention

Low back pain (LBP) is the fifth most common reason for all physician visits. Up to one-quarter of the population will have low back pain in any given year. Greater than 90% of the population will experience at least one episode of back pain during their lifetime.¹ Lumbar strain is the cause of low back pain in 70% of cases, and is most common between age 20 and 50.²

Risk factors include repetitive or heavy lifting, prolonged abnormal position of the trunk (rotated, flexed, hyperextended), poor body mechanics or ergonomics, core weakness, and tight/weak hip girdle musculature (e.g., hamstrings, hip flexors).³

Patho-anatomy/physiology

Muscle pain due to lumbar strain may be due to:

• Muscle fiber tearing from indirect trauma, such as excessive stretch or tension.
• Muscle fatigue due to overuse. There may be a metabolic component due to an increased presence of lactic acid.
• Muscle spasm, which is associated with persistent muscle contraction. The reduction of blood flow with subsequent accumulation of metabolites may stimulate pain receptors in blood vessels. Muscle spasm can be a result of muscle fatigue or occur independently.
• Paraspinal muscles becoming deconditioned after injury. Decreased muscle mass results in decreased muscle power, with increased risk for persistent or recurrent muscle injury.³

Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)

• New onset/acute (onset to 4 weeks): Symptoms of axial low back pain present with an acute injury or event. Pain is usually most severe at the time of the injury, or within several hours.
• Subacute (4 weeks to 12 weeks): Most episodes of low back pain due to lumbar strain are self-limited. The majority of patients (75-90%) have significant improvement in pain and function within one month.
• Chronic (longer than 12 weeks): Up to one-third of patients report persistent back pain of at least moderate intensity one year after an acute episode.²

Specific secondary or associated conditions and complications

Chronic low back pain may develop with repeated lumbar strain injuries, or with failure to pursue appropriate therapies in the acute/subacute phase. Prolonged bed rest after injury may lead to cardiovascular and paraspinal muscle deconditioning. Additionally, failure to incorporate preventive measures to decrease the risk of re-injury could result in more serious or frequent future injuries.

History

Patients present with axial, non-radiating low back pain due to an inciting injury or event. Lower limb symptoms such as pain, numbness, tingling, or weakness are usually absent. Pain is usually worse with movement and better with rest. Screening questions for “red flags” exclude the suspicion for the presence of cancer or infection, fracture, cauda equina syndrome, inflammatory arthritis, or non-mechanical visceral disease. Psychosocial factors and emotional distress should also be assessed, as they are strong predictors of poor outcomes.⁴

Physical examination

Physical examination includes inspection of the lower back and extremities. In standing, a postural shift may be present. Lumbar range of motion may be limited and painful in any plane. There is typically tenderness over the lumbar paraspinal muscles or quadratus lumborum, with absence of spinous process tenderness. Straight leg raises may provoke axial back pain, but should not elicit radicular pain (therefore a negative test). Strength, reflex and sensory testing should be normal. Hip examination and special tests, including FABER’s (flexion/ abduction/ external rotation) and Gaenslen’s maneuver can help rule out other sources of pain. Advanced physical exam assessment may include evaluation of core strength such as ability to perform a plank or bridge exercise.

Functional assessment

Functional evaluation of lumbopelvic core strength can be assessed during the clinical exam through observation of trunk and hip control during single limb stance, presence of Trendelenburg gait, and assessment of ability to perform core exercises such as bridge, plank, and one leg step down.

Mobility and function may be impaired by pain. The Oswestry Low Back Pain Disability Index is a questionnaire that assesses the impact of low back pain on ten aspects of daily life (such as lifting, walking, self-care, and work).

On occasion, assessment of function relative to work demand is needed.  A Functional Capacity Evaluation (FCE) consists of a battery of standardized assessments that offers results in performance-based measures and offers predictive value about the individual’s return to work.

Laboratory studies

Lab studies are typically not indicated for lumbar strain. Erythrocyte sedimentation rate (ESR) and/or C-reactive protein (CRP) may be obtained to rule out infection or inflammatory arthritis when such suspicion exists.

Imaging

Imaging studies are not indicated for acute axial low back pain related to lumbar strain in the absence of red flags and provide no clinical benefit.  Plain lumbar x-rays are recommended in patients with history of osteoporosis, chronic steroid use, low velocity trauma, in an elderly individual or to evaluate a young patient for ankylosing spondylitis.⁵ In uncomplicated low back pain, lumbar CT and MRI were not found to lead to improved outcomes. In addition, they often identify radiographic abnormalities that may be present even in asymptomatic patients, and could lead to unnecessary interventions.⁶

Supplemental assessment tools

Any patient meeting high-risk criteria for having a vertebral injury should undergo CT as it provides a detailed analysis of fracture.⁵  Lumbar MRI should be considered for patients presenting with red flags raising suspicion for serious underlying conditions such as cauda equina syndrome, malignancy, or infection.⁵  Electrodiagnostic studies have no place unless there are neurological deficits identified.

Early predictions of outcomes

Risk factors for prolongation of back pain include previous back pain, depression, substance abuse, low socioeconomic status, work dissatisfaction, pending litigation, and prior disability compensation.⁷

Environmental

Environmental factors associated with lumbar strain include heavy and/or repetitive lifting or other physical activity, prolonged sitting, and poor ergonomic conditions.

Social role and social support system

When low back pain becomes a chronic condition, it can lead to loss of function, vocation, and recreation. Such disability can affect one’s role and interaction within the family and community, contributing to the development of depression.

Professional Issues

Early return to work, even with restrictions, is critical to good long-term outcomes and should be addressed at the initial and subsequent visits. Workers who miss six months of work have only a 50% chance of ever returning to their job; the chances decrease to less than 10% if time lost exceeds one year.⁷

Available or current treatment guidelines

Treatment of lumbar strain injury is predominantly symptomatic. The treatment goal is to control pain and inflammation, optimize return to function, and prevent disability. Bed rest should be limited to no more than two days to minimize work absenteeism and lower indirect medical costs without impacting clinical outcomes.⁸

A Joint Clinical Practice Guideline on LBP from the American College of Physicians (ACP) and the American Pain Society recommend clinicians provide patients with evidence-based information on LBP with regard to their expected course, advise patients to remain active, and provide information regarding effective self-care options.⁴ An updated Clinical Practice Guideline from the ACP provides a systematic review of noninterventional treatments in LBP⁹.

At different disease stages

Applying recommendations from the Joint Clinical Practice Guideline for management of LBP,^4,9 treatment stages include:

New Onset/Acute Stage (onset to 4 weeks):

• Treatment is directed at pain reduction, control of excessive inflammation and spasm, and prevention of deconditioning.
• Education includes:
  • instruction to avoid bed rest and resume normal (pain free) activities as soon as possible.
  • initiation of light cardiovascular training to improve blood flow to the back and promote healing as well as strengthen muscles in the abdomen and back.
  • utilization of self-care modalities, including local application of ice or heat which may lessen symptoms of pain and spasm.
• Control of pain through use of analgesics: non-steroidal anti-inflammatory medications (NSAIDs). Medication risks and benefits should be considered when making the recommendation.
• Muscle relaxants are an option for short-term relief of acute low back pain, but all are associated with central nervous system adverse effects (primarily sedation).
• For acute low back pain (duration < 4 weeks), spinal manipulation administered by providers with appropriate training is associated with potential modest short-term benefits.
• Strengthening exercises are less important in this stage of recovery.

Subacute (4-12 weeks):

• Treatment is directed toward progression to normal activity, including aerobic conditioning, incorporation of postural correction and flexibility exercises, and progression to normal physical activity, including sport-specific exercise. Physical therapy treatment should optimize core strengthening/muscular stability to improve strength and endurance, neuromuscular control, and proper load balance between trunk, pelvis and legs. Optimizing soft tissue flexibility with key muscles such as hamstrings, iliopsoas, gastrocnemius, hip rotators and quadriceps is recommended.
• Identification of patients at risk for prolonged work absence and disability is important. Multidisciplinary rehabilitation and functional restoration with a cognitive behavioral component can reduce work absenteeism due to low back pain in occupational settings.
• Cessation of prescribed medications used to treat acute LBP/strain should be attempted.

Chronic (> 12 weeks):

• Comprehensive treatment should include a biopsychosocial treatment approach due to the high frequency of depression and deconditioning in this population. Multidisciplinary rehabilitation is mildly superior to non-multidiscliplinary rehabilitation or general exercise for improving short- and long-term functional status (through up to 60 months). Additionally, cognitive behavioral therapy or mindfulness-based stress reduction have been shown to have moderate benefit in reduction of pain and improved function.
• NSAIDs have shown moderate benefit in chronic low back pain compared to placebo. There is a lower risk of adverse effect with cyclooxygenase-2 (COX-2) selective NSAIDs.
• Adjunctive medications such as duloxetine in patients with chronic pain can be tried. Tramadol may also be effective as a second-line analgesic option.
• Opioid analgesics can be used judiciously in patients with chronic low back pain who have severe, disabling pain that is not controlled with other treatments and only initiated after a discussion with the patient regarding known risks and realistic benefits.
• For chronic low back pain, moderately effective adjunct nonpharmacologic therapies include acupuncture, tai chi, exercise therapy, yoga, progressive relaxation, and spinal manipulation. The level of supporting evidence for different therapies varies from fair to good.⁹

Coordination of care

In chronic pain situations, care coordination with all of the treating providers, including physical therapists, occupational health nurses, athletic trainers, case managers and psychologists/social workers, can optimize a successful return to normal activities.

Patient & family education

Patient and family education regarding the natural history of the condition (favorable prognosis) is advised. Efforts should be made to address possible fear-avoidance behaviors, depression and anxiety, as soon as possible. Incorporation of psychology or social worker services is often helpful to achieve optimal patient and family education.

Emerging/unique Interventions

There are many outcome tools available for LBP.

Oswestry Low Back Pain Questionnaire is the most commonly used disease specific outcome instrument. This tool incorporates questions addressing the functional impact of LBP on ADLs. It is divided into ten sections and scored, with results ranging from 0% disability to 100% disability.¹⁰

Roland-Morris disability questionnaire (RMDQ) consists of 24 statements about activity limitations due to back pain. Patients answer “yes” or “no” to each statement. Each positive answer is worth one point, with scores ranging from 0 (no disability) to 24 (severely disabled).

The Numeric Rating scale (NRS) is used by patients to rate their pain on a 0-10 scale.

Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills

Clinicians should provide patients with evidence-based information on LBP with regard to their expected course, advise patients to remain active, and provide information regarding effective self-care options.

Most patients recover within the expected timeframe noted. However, patients presenting with and/or developing additional symptoms such as leg pain, numbness, tingling, weakness, or saddle paresthesias require further evaluation, as those are symptoms suggestive of lumbosacral radiculopathy.

Failure to improve (development of chronic pain) warrants evaluation for co-existent anxiety, depression and fear-avoidance behaviors.

Cutting edge concepts and practice

Emerging treatment concepts will likely include newer methods of therapeutic exercise interventions, use of web-based applications to optimize patient education and adherence to treatment regimens, and assessment of collaborative treatment approaches. Cross treatment with lesser studied treatments such as prolotherapy and platelet-rich plasma injections, based upon greater understanding of tissue healing principles, may become more prevalent in treatment of muscle strain injuries.

Gaps in the evidence-based knowledge

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