ABC ofRheumatology

LOW BACK PAIN

J R Jenner, M Barry

Radiation of pain after injection of 0.1-0.3 ml 6%hypertronic saline into sacrospinal muscle (yellow)and multifidus muscle (red). Note similarity todistribution of sciatic pain.

Low back pain is a major and increasing cause of disability in theUnited Kingdom. In 1993, 1 1% of the population reported that theiractivities had been restricted by back pain within the past four weeks.Satisfactory treatment of low back pain depends on an accuratediagnosis, but finding the cause for low back pain is often not possiblebecause of difficulties in localising the source of the pain.

In 1938 it was shown that many structures in the lumbar spine,when irritated, give rise to pain with very similar distributions. Despitetechnological advances the identification of an exact source of pain oran exact pathological diagnosis often remains elusive. It is importantfor doctors and patients to understand that the diagnosis of low backpain therefore depends on identifying some clinical syndromes on thebasis of a patient's history and examination, with appropriateinvestigations to exclude serious pathology and support the clinicaldiagnosis. If this principle is misunderstood the result can be amisleading diagnosis and inappropriate treatment.

Back pain syndromes

Clinical feature of back pain due to mechanicalcauseHistory ofpain ExaminationSudden onset Asymmetrical lumbar movementsPrevious recurrent episodes Asymmetrical straight leg raise orUnilateral symptoms Femoral stretch testEased by rest Uniradicular neurological signs

Functional distribution of lumbar nerve rootsNerve root Muscle weakness Reflex changes SensationL2 Hip flexion Front of thigh

Hip adductionL3 Knee extension Knee Inner kneeL4 Knee extension Knee Inner shin

Foot dorsiflexionL5 Foot inversion Outer shin

Great toe dorsiflexion Dorsum of footKnee flexion

Si Foot plantar flexion Ankle Lateral border ofKnee flexion foot and sole

Mechanical back pain or prolapsed lumbar discIt is vital to distinguish mechanical causes

of back pain from other causes as patientswith mechanical causes are likely to respondto physical forms of treatment. The symptomsand signs of mechanical back pain differconsiderably from those associated with backpain caused by underlying systemic disease.Most acute episodes of low back pain arise

in the triad of joints that allow one vertebra toarticulate with another (that is, theintervertebral disc anteriorly and the two facetjoints posteriorly). The commonest primarypathology is degeneration of the nucleuspulposus in the lumbar disc. The disc itself isoften not the source of pain; this may arise inother structures, such as the facet joints or themany surrounding ligaments, that come understress as a result of the disc pathology. It isimportant that doctors explain this to patientsso that they understand why just removingtheir disc will not always cure the pain.True sciatica, with pain and numbness in

the distribution of a single lumbar nerve root,may be accompanied by sensory, motor, orreflex changes and is most commonly causedby a posterolateral protrusion of a discimpinging on the nerve root.

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Clinical feature of back pain due to systemic causeHistory ofpainGradual onset and progressiveSymmetrical or alternating distributionWorse with restDisturbs sleepMorning stiffness for over 30 minutes

ExaminationStiff or rigid spineSymmetrical restriction of lumbarmovements

Symmetrical restriction of straightleg raising

Multiradicular neurological signs

Common predisposing factors for postural back painPostural faultFlat lordosis

Exaggerated lordosisScoliosis

CauseSeating-car seats, low sofas and armchairsBeds-old, soft bedsHousehold tasks-ironing, vacuuming, low work

surfacesBending-gardening, poor lifting techniqueFootwear-high heeled shoesUnequal leg length-congenital, old leg fracture,

running on cambered roads

Systemic back painAs well as back pain, there may be

associated systemic features such as weightloss, pyrexia, and general malaise.Examination should include the testicles andprostate in male patients and the breasts infemale patients as tumours in the sex organsmetastasise preferentially to the skeleton.

Ankylosing spondylitisThis can be difficult to distinguish from

mechanical pain, especially in the early stages.However, morning stiffness for more than 30minutes, pain that alternates from side to sideof the lumbar spine (a symptom rarelyreported in any other cause of back pain),sternocostal pain, and chest expansion of lessthan 5 cm suggest ankylosing spondylitis.Education, anti-inflammatory drugs, andexercise are the mainstays of treatment.

Special and lateral recess stenosisSpinal stenosis is common in people aged

over 60 and is often not considered in thediagnosis of back and leg pain. It is caused bya narrowing of the spinal canal orintervertebral foramen resulting fromdegenerative disease. The symptoms shouldbe compared with those of peripheral vasculardisease (in this condition the pain eases whena patient stands still and upright). Computedtomography is the investigation of choice. Insevere cases surgery may be required todecompress the stenotic area.

Postural painBad posture is probably the commonest

cause of persistent back pain. The spinedepends for its strength on maintaining aseries of arches. Sitting and leaning forwardtend to flatten the arch or lordosis, whilewearing high heels tends to exaggerate thearch (hydcerlordosis or sway back).

Ideal posture for working at a computer terminal.

Unequal leg length is easily overlooked; 2% of the normal adultpopulation have differences in leg length of at least 2 cm, and suchpeople are more prone to back pain. This can be diagnosed in thesurgery by placing wooden blocks of different thicknesses under theshort leg and checking the pelvic level visually. Up to a third of patientswith back pain and differences in leg length of more than 2 cm willgain relief with a heel raise.

Advice on correcting bad postural habits may be difficult for apatient to accept and may need to be reinforced through programmessuch as a back school.

Referred painPathology in organs in the posterior part of the abdominal cavity

may refer pain to the back-for example, aortic aneurysm or enlargedlymph nodes. Examination of the abdomen is vital for exclusion ofthese diagnoses.

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Clinical feature of back pain due to spinal stenosisHistory ofpain ExaminationLeg pain on walking Stiff spineNeurogenic claudication Normal straight leg raisingEased by leaning forward or sitting Normal peripheral pulses

but not standing still Nerve root signs appear lateAt ages over 60

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Psychological aspects

TendernessAxial loadingSimulated rotationStraight leg raising

Loss of sensationLoss of powerGeneral response

Physical diseaseLocalisedNo lumbar painNo lumbar painLimited despite

distractionDermatomalMyotomalAppropriate pain

Abnormal illness behaviourSuperficial, widespread, non-anatomicalLumbar painLumbar painImproves with distraction

RegionalRegional, jerky, giving wayOvert pain response

Some patients' symptoms seem to beexaggerated and disproportionate to thephysical signs. A history of involvement inmedicolegal proceedings may be obtained.While the possibility of missed pathologymust always be borne in mind, examinationmay reveal inappropriate physical signs.

because of back pain.

Investigations

Radiographic evidence of disc infectionor vertebral collapse occurs late in thecourse of a disease, and blood tests areprobably a better initial screen forsystemic disease

Computed tomogram showing malignantinfiltration of lower thoracic vertebra.

If a patient has been offwork for many months the prognosis ispoor; the longer people are off work with low back pain the less likelythey are to work again. The reasons for this are unclear but have asmuch to do with psychological processes as organic pathology. Theconcept of learned illness behaviour is popular and may explain thepersistence of symptoms of chronic unremitting back pain in patientsin whom an organic cause cannot be found. This syndrome probablyhas links with other syndromes such as fibromyalgia and chronicfatigue syndrome.

Blood testsA blood count, erythrocyte, sedimentation rate, and biochemical

screen (calcium, phosphate, and alkaline phosphate) should beperformed when a systemic cause for back pain is suspected. Testingfor prostate specific antigen is useful if prostatic malignancy issuspected.

Radiological investigationPlain radiographs of the lumbar spine are rarely helpful, particularly

when taken early in the course of an episode of back pain, and shouldbe performed only if systemic disease is suspected.

Bone scans are helpful in cases of suspected malignancy and may beabnormal in metabolic bone disease and ankylosing spondylitis.

Other imaging techniquesThese should be performed only when initial conservative treatment

has failed and surgery is being considered.Computed tomography is the method of choice for showing bony

abnormalities such as bone destruction due to malignancy, infection,or spinal canal stenosis. It can also help in revealing lesions of discsand other soft tissue.

Magnetic resonance imaging is still not widely available but is theinvestigation of choice for showing lesions of soft tissues, includinglumbar disc lesions and tumours.

Radiculography was until recently the standard method forinvestigating lumbar disc lesions. It is now used only when the level ofthe lesion is uncertain and magnetic resonance imaging is not available.

Discography is a specialist investigation and may help to identifypatients who would benefit from surgical fusion of the spine.

ElectromyographyA segmental electromyograph may help to confirm the presence of

nerve root degeneration if radiological evidence of abnormal anatomyis not conclusive.

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Symptoms and signs of chronic low back pain inpatients with physical disease and abnormal illnessbehaviour

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TreatmentTreatment should be given early, with the aim of stopping the

problem from becoming chronic.

Bed rest should be kept to a minimum,and early mobilisation should beencouraged

pain.

The sources of the data presented in illustrations are asfollows: J H Kellgren, Clin Sci 1939;4:35-46 for the diagramof radiation of pain; G Wadell et al, Spine 1983;9:209-13 forthe box of symptoms and signs of physical illness andabnormal illness behaviour; G Wadell Spine 1987;12:632-44for the graph of return to work after time off because of backpain; and J A Mathews et al, BrJ Rheumatol 1987;26:416-23for the graph of effect of manipulation on acute back pain.

J R Jenner is consultant in rheumatology andrehabilitation at Department of Rheumatology,Addenbrooke's NHS Trust, Cambridge, andM Barry isconsultant rheumatologist at Department ofRheumatology, James Connolly Memorial Hospital,Dublin, Republic of Ireland.The ABC of Rheumatology is edited by Michael L

Snaith, senior lecturer in rheumatology at Nether EdgeHospital, Sheffield.

Bed restBed rest has been the main treatment for all forms of acute back

pain for many years, with recommendations varying from a few days toover six weeks. The few satisfactory trials that have been publishedsuggest that bed rest for two or three days has the same or greaterbenefit than longer periods of rest and that shorter bed rest leads to anearlier return to work. Slightly longer periods of rest may be justifiedfor sciatica.

Treatment of low back painPatient education and exercise-Reassuring patients, giving them

appropriate information, and advising them on posture and exerciseprogrammes are important. These measures are most effective whengiven as part of a structured programme such as a back school.

Back schools are effective for treating acute back pain. The conceptof back schools was developed in Sweden and is based on a series offour sessions, each lasting an hour. Treatment is in groups so thatseveral patients may be treated in one session by a single therapist withno need for specialist facilities. Patients can also benefit from talkingwith fellow sufferers.

Manipulation has been the subject of many studies, with conflictingresults. Manipulation seems to be effective in the first three weeks afterthe start of acute back pain and gives quicker relief of pain, but afterthree weeks it may have little advantage over natural recovery. Themost effective method is unknown, but physiotherapists, chiropractors,and osteopaths, who use a variety of techniques, all seem effective.Manipulation should not be used with patients with sciatica andevidence of nerve root entrapment as it may make the root lesionworse.

Treatment of sciaticaTraction-Continuous or intermittent traction remains a popular

treatment for patients suffering from sciatica, though recent studieshave not consistently confirmed its benefit.

Epidural injections of local anaesthetic and depot preparations ofcorticosteroid may speed recovery from sciatica. Both the caudal andlumbar routes ae used. Depot corticosteroid preparations are notlicensed for use in the epidural space, but serious adverse reactions arerare.

Interventional treatments-For patients with symptoms of sciaticalasting more than six weeks despite conservative treatment and inwhom the prescence of a disc protrusion is confirmed, surgical orchemical removal of the nucleus of the disc should be considered. Thesuccess rates for these techniques are 70-80% at one year aftertreatment, but the rates tend to fall with time, particularly for somesurgical techniques.

Chronic low back painOnce back pain has been established for more than a year the

prognosis is poor. Lesions that might be amenable to surgery, such asdisc protrusion or spondylolysis, must be excluded. Patients may bereferred to a pain clinic for local injections of corticosteroid orcryotherapy to facet joints or sclerosant injections into ligaments, butthe success of these procedures for chronic pain is low.The main aim of treatment should be to help patients to come to

terms with their pain and to accept that they can do much themselvesto relieve their symptoms. This can be achieved with help fromintensive rehabilitation programmes or "schools for bravery," whichare available in specialist centres. Treatment, carried out either on aday case basis or as an intensive three to four week inpatientprogramme, combined physical and psychological approaches tomanaging back pain.

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Elements of a back schoolSession 1-Principles of anatomy of the spineSession 2-Applied body mechanics and

postureSession 3-ErgonomicsSession 4-Relaxation techniques and

exercises

Interventional techniques fortreating sciaticaChemonucleolysis-intradiscal injection of

proteolytic enzymePercutaneous discectomy-by automated

nucleotome or laserMicrodiscectomyConventional discectomy

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