Acute Lower Back Pain

Back pain is common. It is estimated that 60-80% of the population have back pain at some time during their life with between 14-30% having some pain on the day of interview and 30-40% of people reporting some pain within the previous month.

Approximately 5-10% will have some degree of back trouble for long periods of their life, while 3-4% of the population aged 16-44 and 5-7% of those between 45 and 64 will report back problems as a chronic sickness [1].

Consequently, not only do emergency departments (EDs) see many patients presenting with acute back pain but they also see many with acute exacerbations of a chronic back problem and patients with back pain incidental to their presenting problem.

Emergency physicians must be able to differentiate serious from less serious causes of lower back pain. Most patients with serious causes will be referred to specialities for assessment and review, however the ED will manage less serious causes of back pain.

Epidemiology

Back pain tends to start between the late teens and the late forties or early fifties. It is more common in smokers and there seems to be an association between back pain and the inter-related factors of low social class, manual work and low educational achievement. There is a definite association between manual work and time off work because of back pain [2].

The lifetime incidence of true sciatica is much less (about 5.3% in men and 3.7% in women) [2].

History

As with any patient in pain, one should take a full history of the pain. The PQRST mnemonic may be useful:

• Provocative and Palliative factors
• Quality of pain
• Radiation
• Severity and Systemic Symptoms
• Timing

In particular, it is important to enquire for symptoms suggesting serious underlying pathology. These are known as Red Flags and are shown in Table 1:

Table 1: Red flag symptoms indication possible serious spinal pathology [3], [4]

Onset at age <20 or >55

Non-mechanical pain (i.e. unrelated to time or activity), especially if constant and worsening and pain at night

Thoracic pain

Previous history of carcinoma, steroids or HIV infection

Fever, night sweats, weight loss

Widespread neurological symptoms especially sphincter disturbance

Structural spinal deformity

Examination

The examination of a patient with lower back pain will focus primarily on the back but should also include:

• Neurological Examination
• Dermatomes
• Sacral Dermatomes (To assesses for herniation at the L4-S1 nerve roots)
• Nerve Roots with Knee Jerk and Ankle Jerk Tendon Reflexes
• Ability to straight leg raise
• Observations: heart rate, blood pressure, pulse oximetry and temperature

Neurological examination

Each muscle is normally supplied by more than one nerve root, though one nerve root may be dominant. The muscles to be tested for each nerve root are shown in Table 2:

Table 2: Myotomes in the lower limb

L2	Hip flexion
L3	Knee extension
L4	Ankle dorsiflexionBig toe dorsiflexion
L5	Foot inversion
S1	Ankle plantar flexion

If the patient has any loss of sensation or parasthaesiae, it is important to determine whether these are confined to one dermatome or whether they have a different (e.g. stocking) distribution. It is important to test sensation within each dermatome. These are shown in Fig 1:

Fig 1: Dermatomes in the lower limb

The neurological examination finishes with examination of the tendon reflexes. The nerve roots associated with each reflex are shown in Table 3:

Table 3: Nerve roots involved in the tendon reflexes

Reflex	Nerve roots
Knee jerk	L3, L4
Ankle jerk	S1, S2

While the patient is lying on their back for the neurological examination, it is a good time to test for the ability to straight leg raise. Many patients with back pain will have pain radiating to the buttock or leg but in true sciatica (the commonest nerve root lesions are L5 and S1), the pain radiates below the ankle. Some patients with nerve root problems only have pain in the leg and do not have back pain. Patients will have pain if the sciatic nerve is stretched. This occurs on straight leg raising. Dorsiflexion of the foot while the leg is raised will exacerbate the pain (sciatic stretch test).

In a nerve root lesion the patient will have parasthaesiae localised to the dermatome of the involved nerve root and will have altered sensation in the same dermatome. There will be muscle weakness in the corresponding myotome. Muscle weakness on one side with sensory changes on the other side or dissociated sensory changes (e.g. loss of light touch on one side and pain sensation on the other side) are serious signs indicating involvement of the spinal cord rather than a nerve root.

An L4/5 disc prolapse will tend to cause pressure on the L5 nerve root and an L5/S1 prolapse will cause pressure on the S1 nerve root.

It is essential to do a rectal examination and specifically test the sacral dermatomes sensation to assess for herniation at the L4-S1 nerve roots.

Consent the patient for a rectal examination, examine for rectal tone and the ability to contract the anal sphincter. Whilst performing the exam note any constipation or prostate enlargement (carcinoma of the prostate frequently metastasises to bone and may be a cause of back pain.)

Enquire about urinary symptoms as retention of urine or incontinence may indicate a central disc lesion.

With the patient lying on their side, test for sensation in the sacral dermatomes shown in Figure 2:

Fig 2: Sacral dermatomes

Some of the numerous causes of back pain are listed in Table 4. The most important issue for emergency physicians is to be able to differentiate serious from less serious causes and, in particular, to be able to recognise cauda equina compression.

Table 4: Causes of low back pain [3]

Structural	Mechanical or non-specific Facet joint arthritis or dysfunction Prolapsed intervertebral disc Annular tear of intervertebral disc Spondylolysis or spondylolisthesis Spinal stenosis
Neoplasm	Primary or secondary including multiple myeloma
Referred pain to spine from	Major viscera Retroperitoneal structures Aorta Hip
Infection	Discitis Osteomyelitis Paraspinal abscess
Inflammatory	Spondyloarthropathies Sacroiliitis or sacroiliac dysfunction
Metabolic	Osteoporotic vertebral collapse Pagets disease Osteomalacea Hyperparathyroidism

Cauda equina syndrome

Symptoms and signs of a cauda equina syndrome are:

• Acute low back pain (which may be superimposed on a history of chronic back problems)
• Radiation of pain to the legs (usually, but not always, bilateral)
• Lower limb weakness (frequently bilateral)
• Alteration of sacral and perineal sensation (usually, but not always, bilateral)
• Alteration of bladder and/or bowel habit leading to urinary retention and constipation

Not all patients will have all signs: the most sensitive are low back pain, perineal and sacral sensory loss and bladder disturbance [5]. It is possible to have bladder dysfunction in the presence of intact anal tone. It may be missed if it is not considered and examined for and this is most likely to occur in the patient who walks into the department. Have a low threshold for requesting an MRI. A cauda equina syndrome (or spinal cord compression) is a surgical emergency that needs to be operated on within 24 hours after the onset of bladder symptoms. By the time the patient gets to the ED, bladder symptoms may have been present for many hours.

Non traumatic compression fractures

In women older than 50 years of age, the lifetime risk of vertebral fracture is estimated to be about one in three (including asymptomatic fractures). It may be very difficult (or even impossible) to date a fracture on X-ray especially as a previous fracture may have been asymptomatic; if there is no significant past history and the patient presents with acute back pain, it seems reasonable to assume the fracture is new / recent [6].

Postmenopausal women with an initial fracture are at much greater risk of subsequent fractures [6].

Other things that should be considered in patients with compression fractures but no history of trauma are metastases and multiple myeloma.

Spondylolisthesis

Spondylolisthesis is a forward slippage of one vertebra on another. The most common sites are a spondylolisthesis of L5 on S1 and L4 on L5.

The usual cause of the L5/S1 spondylolisthesis is a defect of the pars inter-articularis of L5 which allows slippage of the body of L5. This may be congenital or traumatic and tends to occur in young people.

Slippage of L4 on L5 is usually degenerative.

Spondylolisthesis may sometimes be seen as an incidental finding and so its presence in a patient with back pain does not necessarily mean that it is the cause of the pain. A CT may be helpful in determining the exact cause of the spondylolisthesis and its age.

Infection

Spinal infection, including tuberculosis (TB) is an uncommon cause of back pain but must be considered. Bone and joint TB accounts for about 1015% of non-respiratory tuberculous disease, and about half of this is in the spine. Spinal TB must, particularly, be considered in ethnic minority groups. The most common presenting symptom is back pain and there may be spinal tenderness and kyphosis. It may present with a paraspinal abscess as loin swelling or as a psoas abscess with spasm and hip flexion. Neurological symptoms can occur. Systemic symptoms such as weight loss and night sweats can occur but is not common in bony TB. There is no evidence to preferentially recommend CT or MR scanning for these patients [7].

Malignancy

Patients with a history of malignancy may have non-specific back pain but metastasis should always be considered. The following symptoms and signs are suggestive of this:

• pain in the middle (thoracic) or upper (cervical) spine
• progressive lower (lumbar) spinal pain
• severe unremitting lower spinal pain
• spinal pain aggravated by straining (for example, at stool, or when coughing or sneezing)
• localised spinal tenderness
• nocturnal spinal pain preventing sleep

The investigation of choice is an MRI rather than plain X-rays.

No investigation is required for the vast majority of patients with non-specific back pain. Red flag symptoms or signs suggestive of cauda equina syndrome will mandate urgent MRI scanning.

Imaging of patients with non-specific back pain and no red flag symptoms or signs is unhelpful. Many patients with spinal pathology may have normal plain X-rays and, conversely, many patients with no back pain may have X-ray abnormalities (particularly degenerative disease). Similarly many patients with no back pain have abnormal MRI scans.

Blood tests may be useful if one suspects infection or metabolic problems but are not necessary as screening investigations for patients with no pointers to those problems.

In primary care, radiography of the lumbar spine in patients with back pain of more than six weeks duration improved patient satisfaction but did not improve outcome [8]. There is no published evidence on the value of X-rays in the acute setting but the inference is that there is no benefit [9].

Symptomatic treatment of acute musculoskeletal lower back pain

Analgesia. Patients in pain should be given analgesia. The Cochrane Collaboration found that non-steroidal anti-inflammatory drugs (NSAIDs) are slightly more effective for short term symptomatic relief in patients with acute back pain (without sciatica) when compared with placebo. However they comment than many of the studies are of poor quality and there are few data on long term results and side effects [10]. A further review found them to be valuable [11].

Muscle relaxants. Muscle relaxants are effective in the management of non-specific low back pain, but the adverse effects require that they be used with caution [12,13].

Patients should be advised to stay active. Although many people get some relief from low back pain by lying down, advice to rest in bed is less effective in reducing pain and improving an individuals ability to perform every day activities than advice to stay active [14,15].

Physiotherapy. While it has been argued that physiotherapy is of little value in back pain [16], the trial to which the author refers [17] compared routine physiotherapy with an assessment session and advice from a physiotherapist. A physiotherapist assessing and advising a patient is likely to spend much more time doing so than a doctor in the ED so this trial cannot say that referral to a physiotherapist is of no value. Another study has shown that manipulation followed by exercise was of benefit [18]. There is great diversity of patients in many of the trials and equal diversity among physiotherapists and the treatments they offer and so it is difficult to conclude definitively on the value of physiotherapy for any individual patient.

Other treatments that have been investigated for low back pain are:

• Traction. Studies have shown that traction (continuous or intermittent) as a single treatment for LBP was no more effective than placebo [19]
• Massage. While massage is of value for chronic back pain, there is still not enough evidence about massage for acute back pain[20,21]
• Antidepressants. Antidepressants are a common treatment for low-back pain. They are prescribed for three main reasons: to provide pain relief, help with sleep and reduce depression. However a Cochrane review could find no convincing evidence that antidepressants relieve back pain or depression more effectively than placebo. They did not result in any other apparent benefits in the treatment of back pain and they had side effects [22]. They may have a role in neurological pain in sciatica
• Local heat. There is moderate evidence that heat wrap therapy reduces pain and disability for patients with back pain that lasts for less than three months. The relief has only been shown to occur for a short time and the effect is relatively small. The addition of exercise to heat wrap therapy appears to provide additional benefit [23]
• Local cold. There is still not enough evidence about the effect of the application of cold for low-back pain of any duration [23]
• Individual patient education for low back pain. People with low-back pain who received an in-person patient education session lasting at least two hours in addition to their usual care had better outcomes than people who only received usual care. Shorter education sessions, or providing written information by itself without an in-person education session, did not seem to be effective [24]
• Spinal manipulative therapy. Spinal manipulation was more effective in reducing pain and improving the ability to perform everyday activities than sham therapy and therapies already known to be unhelpful. However, it was no more or less effective than medication for pain, physical therapy, exercises, back school or the care given by a general practitioner [25]
• Exercise therapy. In acute low-back pain, exercise therapy has not been shown to improve pain or function over no treatment or other conservative treatments. However it appears to be slightly effective at decreasing pain and improving function in adults with chronic low-back pain, particularly in healthcare populations. In subacute low-back pain there is some evidence that a graded activity program improves absenteeism outcomes, though evidence for other types of exercise is unclear [26,27]
• Lumbar supports. It is unclear whether lumbar supports are more effective than no or other interventions for treating low-back pain [28]
• Acupuncture. There is no evidence to support the use of this [29]
• Strong opiates (eg oramorph). There are no published trials looking at this [30]

Note that the above evidence largely relates to acute back pain. The results for chronic and subacute back pain may be different.

Treatment of Cauda Equina Syndrome

Cauda equina syndrome is a neurosurgical emergency and urgent referral by the emergency physician will be required once the diagnosis has been made on MRI scanning.

Treatment of sciatica

Epidural injection therapy is commonly used, relatively straightforward and safe. However its value has not been proven [31]. There is a suggestion that it may be of benefit to some patients with sciatica but most of the studies have been in patients with subacute or chronic pain.

Trials of surgery provide suggestive rather than conclusive results. Overall, surgical discectomy for carefully selected patients with sciatica due to a prolapsed lumbar disc appears to provide faster relief from the acute attack than non-surgical management. However, any positive or negative effects on the lifetime natural history of the underlying disc disease are unclear. Microdiscectomy gives broadly comparable results to standard discectomy. There is insufficient evidence on other surgical techniques to draw firm conclusions. Trials showed that discectomy produced better outcomes than chemonucleolysis, which in turn was better than placebo. For various reasons including concerns about safety, chemonucleolysis is not commonly used today to treat prolapsed disc [32].

A recent study has shown that discectomy gives more rapid relief of leg pain than conservative treatment and earlier return to normal activities but the differences between the groups were not statistically different by six months. There was no significant difference in back pain and surgery did not decrease the risk of an unsatisfactory outcome at two years. However 44% of patients allocated to the conservative arm of the trial eventually required surgery [33].

Treatment of vertebral compression fractures

Conventional treatment for vertebral compression fractures is not evidence-based and is focused on the alleviation of symptoms with analgesia medication. Spinal support may help the pain but patients also need to mobilize to regain back movement. The majority of patients become symptom free through these measures. Patients who continue to have pain should be followed up and have repeat lateral standing lumbar spine X-rays to ensure that they are not developing progressive deformity. Surgery may be considered in patients in whom there is continued vertebral collapse and severe pain. Patients with continuing severe pain may also be helped by less invasive procedures, including balloon kyphoplasty [34,35].

Osteoporosis will also need to be investigated and managed. Postmenopausal women with an initial fracture are at much greater risk of subsequent fractures [6] so this is very important and may help to prevent a future attendance with a hip fracture.

Treatment of metastatic disease

Patients with bone metastases and patients at high risk of developing bone metastases should be given information explaining what to do and who to contact if they develop symptoms of spinal metastases or spinal cord compression or if their symptoms progress while waiting for investigation.

Spinal cord compression is an oncological emergency and treatment should be started within 24 hours. Most patients will be given steroids and will need radiotherapy or surgery. Patients with a risk of spinal instability should be nursed flat in neutral alignment.

NICE has recommended (for England and Wales) that every center should have a coordinator for patients with spinal metastases and metastatic spinal cord compression, to whom such patients should be referred [38].

Follow up (if required) is not the role of the emergency physician but may be required by general practitioners, orthopaedic surgeons, spinal surgeons, geriatricians or rehabilitation teams. It is not possible to be prescriptive other than to say that it is the emergency physicians responsibility to recognise when follow-up is appropriate and make the necessary referral.

Prognosis clearly depends on the underlying cause of the back pain but for non-specific musculoskeletal pain, the prognosis is good.

One study has shown that following an episode of back pain 67% had returned to work within seven days and 84% within a month. However 70% have some pain on returning to work [2]. A systematic review has shown very similar figures: pain and disability decrease rapidly within a month (by a mean of 58% of initial levels) and continue to improve until about three months. 82% (95%CI 73-91%) return to work within a month and 93% (91-96%) within three months and a proportion have some of pain extending beyond three months. There is a 26% (19-34%) chance of recurrence within three months and 73% (59-88%) chance of recurrence within a year [36].

Predictors of a poor outcome (in a primary care study) [37] include:

Premorbid factors:

• Increasing age
• Female gender
• Previous history of back pain
• High levels of psychological distress
• Poor self-rated health
• Smoking
• Dissatisfaction with employment

Factors relating to back pain:

• Duration of symptoms
• Pain radiating to the leg
• Widespread pain
• Restriction in spinal mobility

Patients with sciatica return to work more slowly than those with acute back pain without sciatica but exact figures are not available [1].

• In any patient with back pain and urinary symptoms, consider cauda equina syndrome (though the absence of such symptoms does not exclude the diagnosis)
• Beware of back pain that does not sound musculoskeletal (e.g. it is not affected by movement or position). This may suggest sepsis, malignancy or an intra-abdominal cause for the pain (e.g. ruptured abdominal aortic aneurism (AAA) or retroperitoneal bowel perforation).

1. Clinical Standards Advisory Group Committee on Back Pain (Chair Rosen M). Back pain 1994 Pub HMSO London.
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6. NICE. Bisphosphonates (alendronate, etidronate, risedronate), selective oestrogen receptor modulators (raloxifene) and parathyroid hormone (teriparatide) for the secondary prevention of osteoporotic fragility fractures in postmenopausal women. Pub National Institute for Clinical Excellence 2005. View document
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11. Carley S. NSAIDS in acute low back pain. View topic
12. van Tulder MW, Touray T, Furlan AD, Solway S, Bouter LM. Muscle relaxants for non-specific low-back pain.Cochrane Database of Systematic Reviews 2003, Issue 3. Art. No.: CD004252. DOI: 10.1002/14651858.CD004252.View abstract
13. Carley S. Muscle relaxants for acute low back pain. View topic
14. Hagen KB, Hilde G, Jamtvedt G, Winnem M. Bed rest for acute low-back pain and sciatica. Cochrane Database of Systematic Reviews 2004, Issue 3. Art. No.: CD001254. DOI: 10.1002/14651858.CD001254.pub2 View abstract
15. Carley S. Bed rest for acute simple lower back pain. View topic
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17. Frost H, Lamb SE, Doll HA, Carver PT, Stewart-Brown S. Randomised controlled trial of physiotherapy compared with advice for low back pain. Br Med J 2004;329:708-11.
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20. Furlan AD, Brosseau L, Imamura M, Irvin E. Massage for low-back pain. Cochrane Database of Systematic Reviews2002, Issue 1. Art. No.: CD001929. DOI: 10.1002/14651858.CD001929. View abstract
21. Carley S. Massage therapy for acute low back pain. View topic
22. Urquhart DM, Hoving JL, Assendelft WWJJ, Roland M, van Tulder MW. Antidepressants for non-specific low back pain. Cochrane Database of Systematic Reviews 2008, Issue 1. Art. No.: CD001703. DOI: 10.1002/14651858.CD001703.pub3. View abstract
23. French SD, Cameron M, Walker BF, Reggars JW, Esterman AJ. Superficial heat or cold for low back pain. Cochrane Database of Systematic Reviews 2006, Issue 1. Art. No.: CD004750. DOI: 10.1002/14651858.CD004750.pub2. View abstract
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27. Carley S. Exercise for acute back pain. View topic
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29. Carley S. Acupuncture in acute back pain. View topic
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Further reading

Two further important documents:

• Lavy C, James A, Wilson-McDonald J, Fairbank J. Cauda equina syndrome. Br Med J. 2009;338:881-4.
• Low back pain: Early management of persistent non-specific low back pain Pub NICE 2009. View document