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Introduction

Mechanical back pain (aka non-specific back pack, sometimes previously termed lumbago) is a term used to describe musculoskeletal lower back pain. It is extremely common, with about 80% of those in Western Society experiencing it at some point in their lives. It is particularly common in those working in manual labour industries. It accounts for more days of sick leave than any other disorder.

It is the most common cause of lower back pain, but care must be taken to rule out more serious differentials when presented with this very common complaint.

It is also a common cause of chronic pain.

It can be:
  • Acute – <4 weeks duration
  • Subacute – 4-8 weeks duration
  • Chronic – >12 weeks duration

Risk factors

For chronic lower back pain with no apparent cause
  • Smoking
  • Low socioeconomic status
  • Poor working conditions
  • Cardiorespiratroy disease
  • Large number of children (for men too!)
  • Psychological disorders (inc. anxiety and depression)
  • Long periods of sitting (e.g. at a desk) at work are NOT significant

Psychological factors – yellow flags – these are a set of risk factors for chronic back pain based on psychological beliefs. Patients who exhibit these beliefs are more likely to suffer from chronic back pain:

  • Activity, exercise and pain are harmful
  • Extended rest will help symptoms
  • Problems at work
  • Time of work / compensation due to injury
  • Overprotective family
  • Lack of social support
  • Unrealistic treatment expectations – e.g. does not attend all physio sessions, does not perform home exercises

Pathology

  • Due to damage to the muscles / soft tissues of the lower back, as a result of posture, physical activity, lifting etc.
  • Thought to most commonly be due to disorders of the facet joints of the spine which then in turn cause damage to the surrounding tissue
  • There is a cycle of muscle spasm >> pain >> spasm >> pain
Lumbar Vertebrae

Lumbar Vertebrae

Presentation

  • Lower back pain
  • Worse on movement (typically bending / twisting movements)
  • Relieved by rest and at night
  • There may or may not be a a history of a specific injury – e.g. lifting or twisting, recent gardening etc
  • Patient generally well (no fevers or weight loss)

Investigations

Are usually unnecessary it is typically a clinical diagnosis.

Differentials

Differentials are broad and I highly recommend reading the lower back pain article for an overview of assessing lower back pain.

Differentials include:

Management

Usually self limiting. Without intervention:

  • 50% will resolve within 3 weeks
  • 90% will will resolve within 6 weeks

The crux of advice is to encourage patients to maintain normal activities as much as possible. Bed rest should be avoided and may worse pain  and prolong recovery.

Lifestyle advice

  • Continue normal activities to the best of your ability – this will not exacerbate the pain, and in fact, has better long-term outcomes than prescribed lateral bending exercises +/- physiotherapy.
    • Pain is not a sign of damage – try to address the “yellow flag” factors
    • Encourage frequent short walks, maintaining an upright posture, avoiding slouching
    • Gradually increase levels of activity as pain subsides
  • Regular simple analgesia – paracetamol 1g QID
  • Techniques for lifting, standing from sitting/lying
  • Heat – e.g. hot water bottle, heat pads may relieve pain and decrease spasm
  • Swimming – can also be useful as a muscle conditioning exercise
  • Physiotherapy may be useful if there is easy access to services

Analgesiais useful to prevent the muscle spasm >> back pain cycle.

  • Paracetomol should be used at the start – then move up the analgesic ladder (add NSAID – ibuprofen or diclofennac if this is not effective)
  • Opioids may be required in some patients at the start, to bring pain under control

Further medications – if muscle spasm is particularly troublesome, antidepressants (particularly TCAs) may be useful. Diazepam has been used traditionally as a ‘muscle relaxant’ but the evidence for its efficacy is extremely poor, and is should be avoided, especially due to risk of addiction, drowsiness and other side effects.

Physiotherapy may be useful in the acute stages to decrease muscle spasm (and subsequent pain), and is useful in the longer term to improve muscle conditioning and reduce the chances of future flare-ups

  • Most guidelines suggest physiotherapist referral after 6 weeks if pain has not resolved

Preventative measures

  • Muscle conditioning exercises – such as as (swimming, push-ups, planking, other core strengthening exercises, and teaching proper lifting techniques)
  • Weight loss – consider dietician referral and counselling on weight loss techniques

Additional therapies – many patients may consult a chiropractor or osteopath for manipulation / massage but this is no more effective than other methods of rehabilitation

In my own practice I tend to avoid the recommendation of chrioparactors and osteopaths. They usually fill the same medical need as physiotherapists, and there are many excellent chiropractic and osteopathic practitioners out there, however, their training is typically not as “scientific” as that of a physiotherapist and there are some who also peddle pseudoscientific, homeopathic or downright unscientific practices and beliefs. If a patient already has a good relationship with one of these practitioners, and has had good results, I tend not to go against their preferences, but if a patient is looking for advice on who to see, I would generally recommend a physiotherapist over a chiropractor or osteopath.

Specialist referral

  • Typically to rheumatology, chronic pain team or sports physician
  • Consider in cases that persist longer than 12 weeks, despite usual conservative management
  • Some patient may response to cortico steroid injection at the nerve shear or epidurally. This can be arranged by a rheumatologist or interventional radiologist

Surgery

  • Spinal fusion – in this technique, two lumbar vertebrae are fused. It is thought that some of the pain in mechanical back injury is due to movement of the lumbar vertebrae over eachother, and that by fusing vertebrae you reduce the possibility of this occurring. However, result are, again, no better than proper conservative techniques. Usually reserved for patients with persist, disabling chronic pain.

Lower back pain in pregnancy

  • 50-60% of women will experience lower back pain during pregnancy
  • It typically occurs in the third trimester, as a result of the baby’s weight, and altered posture of the mother
  • It may also be possible that hormonal changes during pregnancy that increase flexibility of the pelvis, also act on ligaments in the back, increasing their elasticity, resulting in back pain.

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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