Acute low back pain: diagnosis and management

History taking

A comprehensive and thorough history is the first step to reaching a correct diagnosis for the patient’s complaints. General information related to the pain can first be elicited through questions, including the exact location of the pain on the back, onset, character, duration and time course, associations, exacerbating and relieving factors, and severity. It is important to then exclude any red flags of back pain from serious aetiologies, by asking for a history of cancer, unexplained weight loss, immunosuppression, intravenous drug use, symptoms of urinary tract infection, fever, history of significant trauma, urinary retention, and bladder and bowel incontinence.(1,5) The presence of these red flags warrants a further workup to rule out serious aetiologies of acute low back pain such as major intra-abdominal pathology, cauda equina syndrome, fractures and malignancy (Table I).(6)

Table I

Red flags for serious aetiologies in history taking.

Further history can then be obtained regarding the presence or absence of sciatica. The presence of radiation of pain often provides a clue to the aetiology of the back pain. Bilateral lower limb pain may point towards a central disc prolapse or a diagnosis of spinal stenosis. Unilateral lower limb pain in a dermatomal distribution implies compression, impingement or irritation of the nerve root. Pathologies at the L1–L3 nerve roots correspond to pain at the hips and thighs, while pathologies at the L4–S1 nerve root correspond to pain below the knees to the foot and ankle. More detailed localisation of motor and sensory loss may be attempted by consulting the American Spinal Injury Association chart, which maps specific muscular actions and dermatomes to the respective neurological levels.

The patient’s occupation, whether sedentary and deskbound or an active job that requires physical exertion, is also an important component of the history. Information such as recent heavy lifting or change in exercise regimen, prolonged sitting or poor ergonomics, or even a bad chair can provide a clue to the cause of the back pain. It is also important to check if the patient has any functional deficits resulting from the low back pain. With all the information at hand, the physician will then be able to formulate a treatment plan with regard to activity modification and improving workplace ergonomics for the patient, so as to relieve the low back pain and prevent recurrence.

Physical examination

A standard ‘look, feel, move and special tests’ system of evaluating the musculoskeletal system should be performed. Special tests include the straight leg raise test (Fig. 1). This is useful for identifying lumbosacral nerve root tension, usually due to lumbar discopathy and nerve root irritation. It is also important to conduct a thorough neurological examination, as the level of pathology in the spine can then be localised (Fig. 2).

Fig. 1

Illustrations of the straight leg raise test show (a) the patient’s leg raised (arrow), when the physician can observe for pain radiating down the leg to the buttock of the patient; and (b) the ‘bowstring’ sign (arrow), whereby bending the knee slightly relieves the pain, followed by a further reproduction of the pain upon applying pressure to the popliteal fossa to stretch the sciatic nerve again.

Fig. 2

Simplified pictorial diagram shows the neurological findings in low back pain and correlation to the affected nerve root.

Key red flags should be excluded (Table II). These include the presence of new neurological deficits such as saddle anaesthesia, loss of anal sphincter tone, major motor weakness in the lower limbs, the presence of fever and progressively worsening neurological findings persisting beyond a month.(1)

Table II

Red flags for serious aetiologies in physical examination.

In summary, notwithstanding the importance of red flags, in order to accurately diagnose and treat a patient with acute low back pain, the family physician needs to take a comprehensive history and perform a thorough physical examination, and not solely rely on a checklist of red flags.

Investigations

Imaging is generally not indicated for most patients with low back pain. However, in patients whose pain persists beyond six weeks or who have signs and symptoms indicating a serious underlying aetiology, it is necessary to perform diagnostic imaging.(7-10)

Plain radiography (i.e. X-ray) may be a useful screening tool for obvious pathologies but tends to have little diagnostic value, it has have low sensitivity and specificity.(11) If the radiographs are unremarkable but clinical suspicion is high for a serious pathology, it is appropriate to refer the patient to a specialist for further investigations with magnetic resonance (MR) imaging.(1) MR imaging allows for a detailed, three-dimensional view of the soft tissues and bones as compared to radiography. Computed tomography (CT) of the spine is indicated if there are contraindications to MR imaging. It is important to correlate the findings of CT and MR imaging with clinical findings, as false-positive results increase with age.(12) Blood tests such as full blood count, erythrocyte sedimentation rate and C-reactive protein level may be performed if infections or bone marrow neoplasms are suspected.

Treatment

Physical therapy

Patients should be encouraged to start physiotherapy early for the treatment of low back pain. Physiotherapist-directed home exercises are effective in relieving pain, reducing recurrence and improving overall function. These exercises are generally divided into movement exercises and strengthening exercises. Movement and stretching exercises, including the McKenzie method, help to restore movement and minimise stiffness, which in turn relieves back pain. Strengthening exercises help to improve core muscle stability, preventing further strain on the back and improving overall back stability. These exercise programmes are a cost-effective treatment for low back pain, increasing time intervals between episodes of back pain and reducing time off work.(16,17)

Simple stretches include the knee-to-chest stretch and lower back rotational stretch. In the knee-to-chest stretch, the patient is advised to lie supine on the floor and pull one knee towards the chest and hold it against the chest for five seconds before repeating with the other knee. In the lower back rotational stretch, the patient is advised to lie supine on the floor, keeping the shoulders firmly on the floor. Next, the patient needs to roll both bent knees to one side, holding the position for 5–10 seconds, before rolling both knees to the other side. Another simple method for relieving back pain is getting the patient to lie supine on the floor and placing a tennis ball between the back and the floor, particularly on the areas of the back where the muscles are tight. Simple side-to-side rolling actions can be performed, releasing the tight muscles and relieving the pain (Fig. 3).

Fig. 3

Illustration shows a tennis ball under the back.

Application of ice on the acute onset of low back pain may also provide short-term relief of pain and improvement of disability.(18) However, it may not be useful beyond early low back pain.

Other methods for pain relief include acupuncture,(19) the use of lumbar support,(20) massage(21) and chiropractic spinal manipulation.(22) These modes may produce short-term pain relief but are generally not supported by strong, high-quality evidence.

TAKE HOME MESSAGES

1. Accurate and comprehensive history taking and physical examination are needed to rule out serious causes of acute lower back pain, including cancers, fractures, infections and cauda equina syndrome.

2. Imaging is indicated in patients with acute lower back pain when red flags are present. It is also prudent to offer imaging to patients whose symptoms persist after six weeks of treatment.

3. Treatment goals can include pain relief, function improvement and minimisation of time off work.

4. Physiotherapy and exercise programmes are cost-effective treatments for reducing pain, recurrence and disability in patients with acute lower back pain.

5. Bed rest should not be recommended for patients with non-specific acute lower back pain, as it leads to various adverse effects including muscle deconditioning and joint stiffness.

6. Medications such as NSAIDs, acetaminophen and muscle relaxants are effective first-line treatments for pain relief in patients with acute lower back pain.

7. NSAIDs should be used at the lowest effective dose for the shortest possible period of time, with consideration and monitoring of risk factors such as presence of renal impairment and cardiovascular diseases.