Introduction

Lower back pain is a very common presentation to general practice and emergency departments

  • Lower back pain for at least 5% of all general practice presentations
  • 80% of people will have one or more episode of lower back pain in their life

The most common cause is not serious, and commonly referred to as “mechanical back pain“. The refers to pain that is thought to originate from the lumbar spine facet joints and / or their associated ligaments and muscular attachments. It is typically brief and self-limiting.

It is important to differentiate these vast majority of presentations from the more serious causes of lower back pain.

The individual causes of lower back pain are considered mainly in their own individual almostadoctor articles (linked where relevant). Here we mainly discuss the principles of assessing lumbar back pain.

Epidemiology

  • 5% of all presentations to general practice
    • At least 70% of cases are “mechanical bak pain” (also termed “non-specific back pain” or sometimes”musculoskeletal back pain”)
    • 10% of cases are “spondylosis” which includes osteoarthritis and degenerative back diseases
    • The spondyloarthritides (inflammatory causes such as ankylosing spondylitis and psoriatic arthritis) are commonly misdaignosed, but account for only about 2% of cases
  • 80-90% of people will experience at least one episode in their life
  • 50% of cases will recover within 2 weeks
  • 90% of cases will recover within 6 weeks
  • 50% of cases are recurrent
  • about 5-7% of patients will develop chronic pain as a result
  • Average age of presentation is 45, most cases present in patents between 30 – 60

Aetiology

Causes of back pain and their frequency:

A diagnostic approach

Red flags for back pain

Consider urgent investigation (perhaps via the emergency department) for anyone presenting with:

  • Trauma
  • Fever
  • History of cancer
  • Lower limb neurological symptoms, particualrly
    • Saddle anaesthesia
    • Urinary retention
    • Faecal incontinence
  • Age <20 or >50
  • Pain at rest when lying flat
  • Pain that wakes the patient at night
  • Weight loss
  • History of IV drug use
  • Anticoagulant use (causing haemorrhage around nerve roots)
  • Steroid use (leading to osteoporosis and crush fractures)
  • Pain duration >1 month

Yellow flags

The term “yellow flags” refers to factors in the patient’s history and circumstances that increase the likelihood of the pain becoming a chronic pain problem. They are typically social and psychological factors. They include:

  • Belief that the pain is harmful and activity should be avoided
  • Compensation issues around an injury
  • Failure to return to work
  • Treatment refusal
  • Poor response to treatment
  • Atypical examination findings

In my personal practice I am also wary of patients who “reel off” previous specific imaging findings as the cause of their back pain, e.g. “I’ve got L2/L3 and L4/L5 facet joint arthropathy, and an L4/L5 disc prolapse”

History

  • Timing of the pain
    • Pain worse at rest and relieved by activity is associated with inflammatory back pain such as ankylosing spondylitis or psoriasis
    • Pain that wakes the patient at night is also suggestive of more serious causes
    • Pain received by rest and lying flat is typically related to mechanical back pain
    • Constant pain day and night is associated with infection or malignancy
  • Stiffness
    • Significant morning stiffness, or stiffness after rest is associated with inflammatory causes
  • Activity
    • Relieves pain – inflammatory
    • Aggravates pain – mechanical
  • Pain intensity
    • Worse in the morning – inflammatory
    • Worse in the evening or after activity – mechanical
  • Sitting
    • Aggravates pain – often mechanical with a disc cause
    • Relieves pain form standing – consider spondylisthesis
  • Pattern
    • Acute episodes, lasting days to weeks, with pain-free or vastly improved symptoms in between – mechanical
    • Insidious onset, pain on waking in the morning, morning stiffness – inflammatory
  • Location

Examination

“Look, feel, move”, then special tests

  • Inspect the lower back. Look for
    • Asymmetry
    • Swelling
    • Erythema
  • Palpate the spines processes, checking for tenderness
    • Typically mechanical back pain has minimal mid-line tenderness
    • Include the sacrum and coccyx
  • Palpate the parspinous area bilaterally
    • Muscular causes will often have soft tissue tenderness in this area
    • Often non-tender in mechanical back pain
  • Movements
    • (Forward) flexion
    • Extension
    • Lateral movements
    • Rotation of the lumbar spin is limited and not particularly useful to assess
    • Assess if any of these movement elicit the pain
  • Special tests
    • Straight leg raise – the patient is passive. With the patient lying on their back on the couch, raise the leg whilst keeping it straight. A positive test is elicited when shooting pains are felt down the back of the leg. Indicative of sciatica
  • Neurological examination
    • Perform a neurological examination of the lower limb IF there are any symptoms in the buttocks or legs
    • In the absence of these symptoms, it may not be necessary
    • The aim of neurological examination is to assess for neurological deficit which might be indicative of cause equine syndrome
  • Pattern of nerve root involvement (if sciatica)
    • L3
      • Motor – knee extension
      • Sensory – anterior thigh
      • Reflex – knee jerk
    • L4
      • Motor – foot inversion (resisted)
      • Sensation – medial aspect of foot including big toe
      • Reflexes – knee jerk
    • L5
      • Motor – resisted extension of big toe
      • Sensation – dorsal of foot over middle 3 toes
      • Reflexes – None
    • S1
      • Motor – resisted eversion of foot
      • Sensation – Little toe plus sole of foot
      • Reflexes – ankle jerk
    • Single root affected – likely a disc prolapse, multiple nerve roots affected – suspect more sinister cause (e.g. neoplasm)

Investigation

  • Most cases do not require investigation
    • Be very cautious that imaging (particularly CT and MRI) will frequently report multiple anatomical abnormalities (ranging from disc prolapse and facet joint arthroapthy to non specific “degenerative changes” which can be of dubious clinical significance, and are unlikely to change management. I always warn my patients of this before requesting any imaging, and explain to them the specific abnormality that I am looking for before the scan.
  • Consider investigations in:
    • Presence of red flags at presentation
    • Patients with >6 weeks of pain

Choice of investigation

Consider screening tests in patients with non-specific symptoms. A lumbar back pain screen might typically include:

  • Plan x-rays (or CT scan)
  • Urine dipstick
  • Bloods
    • FBC
    • CRP
    • ESR
    • Alk Phos
  • PSA (men >50)

Consider specific investigations in certain presentations:

  • HLA-B27
    • Ankylosing spondylitis suspected
  • Serum electrophoresis
    • Myeloma
  • PSA
    • Prostate cancer
  • Blood culture
    • Discitis
  • Bone scan
    • Malignancy
  • Peripheral artery angiogram
    • Peripheral artery disease
  • MRI
    • Discitis
    • Pre-operative planning in significant canal stenosis or other surgically treatable cause

 

References

  • Murtagh’s General Practice. 6th Ed. (2015) John Murtagh, Jill Rosenblatt
  • Oxford Handbook of General Practice. 3rd Ed. (2010) Simon, C., Everitt, H., van Drop, F.
  • Beers, MH., Porter RS., Jones, TV., Kaplan JL., Berkwits, M. The Merck Manual of Diagnosis and Therapy

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