Back pain is very common. Assessment is demanding and knowledge of red flags is essential to identify malignancy, infection, serious neurological pathology and fracture within the spine.
A simple system based on 'look, feel, move and specialised testing' is required for a proper evaluation.
Despite this, it can be difficult to assess patients attending clinic with low back pain and often no discernable cause can be identified. There is no gold standard available with which to compare the specificity and sensitivity of examination.
Assessment of the spine commences by eliciting the history of pain; its duration and radiation, and any aggravating or relieving factors.
The identification of metastatic spinal disease is not unusual as the index presentation for malignancy.A new onset of severe unremitting pain, especially at night, with a past history of malignancy is clearly worrying. Infection may be present in the immunocompromised patient or very young. The presence of sciatica or leg pain radiating below the knee or neurogenic claudication (limitation of walking due to leg pain) could suggest a neurological cause of pain. Loss of sensation when wiping the perineum and an insensate bladder producing painless urinary incontinence suggests cauda equina syndrome.
The inspection should begin with an assessment of the patient's gait as they enter the room. This allows a rapid appreciation of any weakness in the legs and deformity within the spine.
Complete exposure of the back is essential and enables the doctor to inspect the spine initially for the appearance of skin lesions, typical of neurofibromatosis, and the hairy dimple in the midline, suggestive of neural dysraphism. Spinal balance in the sagittal plane is viewed from behind. The head, the nape of the neck, the prominent kyphotic part of the thoracic spine, the most lordotic part of the lumbar spine and the natal cleft should all be in a straight line. Asking the patient to turn to the side will then allow an appreciation of the coronal balance. The ear, the acromion, the highest point of the iliac crest, the prominence of the greater trochanter, the knee and ankle should be in a straight line.
The palpation of the spine should be performed with the patient standing. Each spinous process should be palpated in turn noting any localised tenderness or deformity, with the examination continuing to the coccyx.
With the patient standing, forward flexion and extension can be assessed by instructing the patient to lean forward with straight knees in an attempt to touch the floor and then to straighten and arch the back. This could be quantified by measuring the increase of length between two fixed points in the lumbar spine or by noting the distance between the finger tips and the floor.
An effective neurological examination may be completed by asking the patient to squat to the floor then rise and by testing tip-toe and heel walking. This is not appropriate for frail patients.
Further assess the patient seated on the couch with their legs hanging by the side, before asking the patient to adopt the supine position. Motor power examined by flexion and extension of the great toe, ankle, knee and hip should be determined and graded according to the Medical Research Council grading scale for muscle power (0 = no muscle contraction visible, 5 = full and normal power against resistance).
The American Spinal Injury Association impairment scale allows assessment of a single nerve root by a single movement and is simple and user friendly.
Straight leg raising and the presence of nerve root irritation should be documented. Active and passive straight leg raising should be undertaken.
In the passive mode the examiner lifts a single limb keeping the knee straight. This movement causes traction on the lower lumbar nerve roots, pulling them caudally. Any pain that occurs below the knee is significant. The examiner then reduces the flexion at the hip by decreasing the angle of elevation by 10 deg.
This should hopefully relax any taut structures in the hip or sacroiliac joint. The ankle is then dorsiflexed to note whether this reproduces the patient's symptoms below the knee.
Reproduction of the patient's pain can then be considered to be neural in origin.
Crossed straight leg raising involves pain occurring in the symptomatic leg when the contralateral leg is lifted for a straight leg raising test.
The crossed straight leg raising test may identify disc prolapse (Photograph: SPL)
This is specific for a prolapsed intervertebral lumbar disc but is not sensitive, as not all patients with disc prolapse experience pain in a crossed straight leg test. The patient is then asked to lie in the lateral recumbent position for the femoral nerve stretch test. The hip is placed in 15 degs of flexion. The knee is then bent backwards. If the procedure provokes pain in the anterior thigh of the patient, then it is considered positive.
A back examination can be daunting, but a logical and systematic approach can help differentiate serious pathology from simple mechanical problems.
- Mr Lipscombe is an orthopaedic registrar in Aintree, and Dr Bunstone is a GP principal in Cheshire