Monday, 7 October 2013

Back Pain

HAP2 on back pain and CAP3 include more than you think they might. Life threatening and abdominal causes of back pain are covered elsewhere. Here are some links on general back pain, cauda equina, spinal cord compression and osteoporosis.

Enlighten Me
Back pain module  
Back pain in a young person -
I've gone numb down there
Paediatric Back Pain
Not what I was expecting

BMJ Learning
Metastatic Spinal Cord Compression
Back Examination
Cord Compression
Back Pain

Back Pain

Low back pain: pain between the lower costal margin and gluteal folds, which may be accompanied by leg pain.
Back pain is common and has a huge socio-economic cost, and can be life threatening for the patient. We should not use the bio-medical model of injury (emphasis on looking for pathological lesion that causes back pain) as this is likely to cause over-investigation.

5% of people have a diagnosable condition
<1% have a serious medical condition
Most resolves in 6-8 weeks

History and examination should cover red flags, yellow flags, and nerve root problems.

Red Flags: for possible serious spinal pathology when assessing back pain:
  • non-mechanical pain
  • past history carcinoma, steroids, HIV
  • generally unwell
  • unexplained weight loss
  • widespread neurological symptom or signs
  • structural deformity
  • thoracic pain
  • Age <20 years or >55 years has also been considered a red flag, but it should be borne in mind that non-specific back pain is not uncommon in these age groups. Significant trauma may raise the possibility of vertebral fracture.
Yellow Flags:  risk factors for developing and or maintaining long-term pain and disability
- Belief that pain and activity is harmful
- Belief that pain will persist
- Sickness, avoidant and excessive safety behaviours (like extended rest, guarded movements)
- Low or negative moods, anger, distress, social withdrawal
- Treatment that does not fit with best practice
- Claims and compensation for pain-related disability
- Problems with work, sickness absence, low job satisfaction
- Overprotective family or lack of support
- Placing responsibility on others to get them better (external locus of control)

Indicators for nerve root problems:
- Unilateral leg pain and low back pain
- Radiates to foot or toes
- Numbness or paraesthesia in same distribution
- Straight leg raising test induces more leg pain
- Localised neurology (limited to one nerve root)

Sacroiliac joints: Lie supine and apply firm downward pressure over both sides of the pelvis

Straight leg raise test: suggestive of nerve root pain.
    Ask the patient to lie flat on their back
    Raise the patient's leg and ask them to tell you when they feel pain in thigh, buttock, and calf
        The leg must be completely straight
        The test is positive if pain occurs with the leg at an angle of less than 70°
    It is normal to experience pain with the leg at an angle of 80-90° with the bed.

Sciatic stretch test:
    Dorsiflex the foot with the leg still raised
        The test is positive if the patient experiences further discomfort in the thigh, buttock, and calf
    The pain should be relieved by bending the knee.

You should repeat both tests on the unaffected leg. You should suspect a prolapsed intervertebral disc in patients who experience pain in the affected leg when you raise the unaffected leg. You should make an urgent referral in these patients because they are at risk of developing cauda equina syndrome.

The leg must be raised 30° above the bed. Below this angle the sciatic nerve is not stretched. You should consider an alternative diagnosis such as arthritis in patients who experience pain with the leg below a 30° angle.

Femoral Stretch Test:

Imaging is unlikely to be helpful, even MRISs. In asymptomatic people, MRIs show:
- Bulging discs in 20% to 79%
- Herniated discs in 9% to 76%
- Degenerative discs in 46% to 91%.

50% of patients with sciatica will recover from the acute attack within 6 weeks. Over a third of back pain cases will have accompanying leg pain, true nerve root pain has a prevalence of around 4%, and "surgically important" root pain is as low as 2%.

Cauda Equina

Spinal Cord Compression
3-5% of patients with cancer develop bone metastasis. If they have a high risk cancer this rises to 20%. Mets may occur years after the primary cancer diagnosis.
Only about 1/2 of patients with SCC will have a high risk cancer. 20-25% have no existing cancer diagnosis.
17% of patients have lesions at two or more levels so the entire scan should be MRId. Spinal cord compression often occurs in the last year of life.

    Back pain (95% of patients), radiating (in 37%) or localised (15%).
    Spinal pain aggravated by straining (for example, when coughing)
    Nocturnal spinal pain which interferes with sleep.
    Limb weakness (87% of patients)
    Paraplegia (18%) 
    Painless urinary retention

Patients who have primarily compression of the posterior cord may lose proprioception, and so have difficulty walking, but may have normal muscle power on assessment.
Symptoms and/or signs of spinal cord compression may become more obvious if you load the patient's spine, eg by getting them to carefully stand and walk - providing they do not have significant movement related spinal pain

Plain x-rays need up to 50% bone loss before lesions become visible.
CT  may show supplemental information
MRI is the main imaging modality

Radiotherapy will help a tumour
Nurse patients flat wit neutral spinal alignment, log roll, and use a bed pan.
16mg dexamethasone

Think about prophylaxis before the patient gets a fracture. The FRAX score is very useful. 

Alendronate is the first line treatment. Alendronate can cause dyspepsia, but we shouldn't start at PPI because it’s not an acid related dyspepsia. There is  evidence to suggest that PPIs and H2RAs actually increase the risk of fracture.

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