Lower Back Pain

Definition | Aetiology | Pathophysiology | Risk Factors | Signs and Symptoms | Investigations | Management | Red Flags | References

Definition

Lower back pain (LBP) refers to pain and discomfort localised to the lumbar region of the spine. It is a common condition, often self-limiting, but can also be a symptom of more serious underlying pathology.

Aetiology

Lower back pain can have various causes, including:

• Mechanical back pain: The most common cause, often due to muscle strain, ligament sprain, or degenerative changes in the spine.
• Herniated disc: A condition where the intervertebral disc protrudes and compresses nearby nerves.
• Spondylolisthesis: A condition where one vertebra slips over the one below it, often causing pain.
• Spinal stenosis: Narrowing of the spinal canal, which can compress the spinal cord or nerves.
• Osteoarthritis: Degenerative joint disease affecting the spine, leading to pain and stiffness.
• Inflammatory conditions: Such as ankylosing spondylitis, which can cause chronic back pain.
• Infections: Such as osteomyelitis or discitis, though these are less common.
• Neoplasms: Primary or metastatic cancer affecting the spine.

Pathophysiology

The pathophysiology of lower back pain involves:

• Mechanical factors: Strain or injury to the muscles, ligaments, or intervertebral discs can lead to inflammation and pain.
• Degenerative changes: Over time, the intervertebral discs and facet joints may degenerate, leading to reduced flexibility and pain.
• Nerve compression: Conditions such as herniated discs or spinal stenosis can compress the spinal nerves, leading to pain and neurological symptoms.
• Inflammation: Chronic inflammatory conditions can affect the spine, leading to persistent pain and stiffness.

Risk Factors

• Age, particularly over 50 years
• Occupation involving heavy lifting or prolonged sitting
• Obesity, which increases stress on the spine
• Poor posture, which can contribute to strain on the lower back
• Previous back injury or trauma
• Genetic predisposition to degenerative spine conditions
• Smoking, which can impair blood flow to spinal tissues

Signs and Symptoms

The signs and symptoms of lower back pain can vary based on the underlying cause:

• Mechanical back pain: Localised pain in the lower back, often exacerbated by movement or prolonged sitting.
• Radicular pain: Pain radiating down the leg (sciatica) due to nerve compression, commonly associated with a herniated disc.
• Stiffness: Reduced range of motion in the lower back, particularly after periods of inactivity.
• Neurological symptoms: Such as numbness, tingling, or weakness in the legs, which may indicate nerve involvement.
• Night pain: Pain that wakes the patient from sleep may be a red flag for more serious pathology.

Investigations

Specific investigations to assess lower back pain include:

• X-rays: Useful for assessing bony structures, such as detecting fractures, spondylolisthesis, or significant degenerative changes. If a patient has a history of cancer or presents with red flags, a lumbar spine X-ray in the anteroposterior (AP) and lateral views is appropriate.
• MRI: The imaging modality of choice for assessing soft tissue structures, including intervertebral discs, spinal cord, and nerve roots. MRI is particularly indicated in cases with red flags or persistent pain unresponsive to conservative treatment.
• CT scan: May be used if MRI is contraindicated, providing detailed images of the bony structures.
• Blood tests: Including inflammatory markers (CRP, ESR), and tumour markers if malignancy is suspected.
• Bone scan: May be indicated if there is suspicion of metastatic disease.

Management

Primary Care Management

• Conservative treatment: Initial management includes advice on activity modification, the use of heat or cold packs, and physical therapy to improve strength and flexibility.
• NSAIDs: Nonsteroidal anti-inflammatory drugs (e.g., ibuprofen, naproxen) for pain relief and inflammation control.
• Pain management: Use of analgesics or muscle relaxants to manage acute pain.
• Patient education: Providing information on posture, ergonomic modifications, and lifestyle changes to reduce strain on the spine.
• Referral to physiotherapy: For patients requiring structured exercise programs to manage pain and improve function.
• Referral for imaging: If red flags are present, such as a history of cancer, unexplained weight loss, night pain, or neurological deficits, an urgent MRI or X-ray (AP and lateral views) should be requested.

Specialist Management

• Referral to a spinal specialist: Indicated for persistent or severe symptoms, particularly if there is evidence of nerve compression or other neurological deficits.
• Epidural steroid injections: May be used to reduce inflammation and pain in cases of nerve root compression.
• Surgical intervention: Considered in cases of severe or progressive lower back pain, particularly when conservative management has failed, or in cases of significant neurological impairment.
• Management of underlying conditions: Addressing any specific underlying causes of lower back pain, such as osteoporosis, inflammatory arthritis, or malignancy.

Red Flags

Red flags in lower back pain are important indicators of potentially serious underlying conditions. These include:

• History of cancer: Lower back pain in a patient with a previous diagnosis of cancer should raise suspicion for metastatic disease. Urgent imaging (MRI or X-ray) is warranted.
• Unexplained weight loss: May indicate malignancy or systemic disease.
• Night pain: Pain that wakes the patient from sleep is concerning for malignancy or infection.
• Age over 50: Increased risk of malignancy, particularly if the patient has other red flags.
• Age over 50: Increased risk of malignancy, particularly if the patient has other red flags.
• Prolonged use of corticosteroids: Raises the suspicion of osteoporotic fractures, especially in older adults.
• Recent significant trauma: Particularly in older adults or those with osteoporosis, where even minor trauma can cause fractures.
• Neurological deficits: New or progressive neurological symptoms such as numbness, weakness, or bowel/bladder dysfunction may indicate spinal cord or nerve root compression.
• Infection signs: Fever, history of intravenous drug use, or recent infections may suggest spinal infections such as osteomyelitis or epidural abscess.

In the presence of any of these red flags, urgent referral for imaging and further specialist assessment is necessary. If malignancy is suspected, the imaging should include an X-ray of the lumbar spine to assess for any lytic lesions, fractures, or other bony abnormalities.

References

1. NHS (2024) Lower Back Pain. Available at: https://www.nhs.uk/conditions/back-pain/ (Accessed: 24 June 2024).
2. National Institute for Health and Care Excellence (2024) Low Back Pain and Sciatica in Over 16s: Assessment and Management. Available at: https://www.nice.org.uk/guidance/ng59 (Accessed: 24 June 2024).
3. British Medical Journal (2024) Assessment and Management of Lower Back Pain. Available at: https://www.bmj.com/content/350/bmj.h4200 (Accessed: 24 June 2024).
4. American Academy of Family Physicians (2024) Red Flags for Back Pain. Available at: https://www.aafp.org/afp/2018/1015/p495.html (Accessed: 24 June 2024).

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