All patients must have had backache at some time in their lives. Check with them how this episode differs from any others, as this may reveal signs of sinister causes such as infection, fracture, tumour or critical nerve damage. The warning signs in the history and examination are called ‘red flags’ and are designed to alert you to sinister pathology. ‘Yellow flags’ are features that suggest that a psychological approach to the management of the backache will be more useful than a standard organic one (see figure opposite).

Exposure

The cervical spine can only be seen if the patient’s hair is well out of the way. The bottom of the spine can be hidden by the top of the trousers. In trauma it is critical that the whole spine is examined, but the patient must be turned carefully (log-rolled) to avoid causing any further damage to the spinal cord in patients who may have an unstable fracture dislocation of the spine.

Look

Check for the normal curves of the spine and that there are no lateral curves. A hairy dimple at the base of the spine (hidden by the top of the pants) may indicate a partial failure of closure of the spinal canal (spina bifida occulta) which can trap nerve roots. If there is a lateral curve of the spine and it vanishes when the patient sits on the couch, then the curve is probably caused by unequal leg lengths. If the curve gets worse as the patient bends forward (producing a rib-hump) then it is likely to be an idiopathic scoliosis.

Feel

The spine can be felt through its length posteriorly. A full abdominal examination is important because back pain can be the presenting sign of many non-orthopaedic problems. Sensory loss as a result of a spine problem will be most likely in the legs or in the perineum (see section on central discs, page 33).

Move

Examination of spinal movement is best performed with the patient standing whenever possible.

• Flexion of the spine can be checked by asking the patient to touch their toes. The examiner should have the tip of their thumb on the top of the lumbar spine and the index finger on the lumbosacral junction, so that the actual movement of the spine (not just flexion of the hips) can be recorded.
  
• Lateral deviation can be tested by asking the patient to slide the flats of their hands down their thighs.
  
• Rotation can be checked by holding the patient’s pelvis still and then asking them to bend and look over their shoulders.

Straight leg raise test

Pain in the back commonly radiates down the leg and so can be difficult to distinguish from pain arising from the hip and knee. The straight leg raise test is designed to do this.

• The patient lies on their back and first the hip is flexed up with the knee flexed too. If there is no pain during this manoeuvre then it is unlikely that any pain is arising from the hip or knee.
  
• The knee is then straightened and most patients will then experience pain in the back of the thigh as the hamstring muscles tighten.
  
• The leg is then gently extended until the hamstrings are relaxed and the patient is again pain-free. At this point the ankle is firmly dorsiflexed. If this reproduces the back pain running down the leg, it is assumed that the sciatic nerve roots are trapped as they leave the spinal canal, and the test is recorded as positive.

Reflexes and muscle power

The decision as to whether a nerve root is trapped is a critical one to the success of spine surgery. Sensory and motor loss at the same nerve level, confirmed by imaging evidence of entrapment of that root as it exits the spinal canal, is a very good prognosticator for the success of surgery. The knee reflex is mainly served by the L4 nerve root, while the muscle extensor hallucis longus is exclusively supplied by the L5 nerve root. The ankle reflex is mainly mediated through the S1 nerve root. These tests are therefore useful for defining the level of a lesion.