Lumbar spine

The lumbar spine is another part of the anatomy which can be best examined initially with the patient standing up. Expo­sure is important and the back must be visible as far down as the natal cleft. The key to the examination of the lumbar spine is a full examination of the lower limbs. Irritation of nerves in the spine can mimic problems in the lower limb. Whenever you see a patient with problems in the lower limb, keep in the back of your mind that this problem could be referred from the spine.

Look

Skin

Look for hairy tufts and dimples at the base of the spine which may indicate an underlying spina bifida.

Soft tissue

Look at the muscles on each side of the spine. If they are very prominent they may be in spasm.

Bone

The lumbar spine should have a smooth concavity (lumbar lordosis). Loss of lordosis and flattening of the buttocks go with muscle spasm (Fig. 20.22). If the spine is curved laterally (scoliosis) then there are three common causes. The legs may be unequal in length (postural scoliosis). This scoliosis will disappear when the patient sits down. Secondly, there may be a fixed scoliosis in the thoracic spine, with a compensatory scoliosis in the lumbar region below it. Thirdly, there may be spasm in the muscles around the lumbar spine caused by pain

Feel

Skin

Sensation. Test sensation in both legs. Sensory loss is most likely to be detectable distally, so simply compare touch on the lateral and medial side of both feet. If this is abnormal, then continue to a full neurological examination. Test for any loss of sensation in the perineal area if the patient complains of sudden onset of pain and numbness in both legs (caudaequina syndrome).

Soft tissue

Feel the muscles on each side of the spine for spasm.

Bone

Trace the line of the spine with your fingers, checking for scoliosis.

Feel the spine of the L5 and the S1 vertebrae. A step between the two may indicate a spondylolisthesis.

Move

Active

Flexion/extension. Place the tip of your thumb over the T12—L1 junction, and the tip of your index finger of the same hand over the lumbosacral junction. Ask the patient to reach forward to try to touch their toes. Note the distance that your thumb and tip of finger separate as the patient bends forward (Fig. 20.23). This distance is a measure of lumbar flexibility.

Note also how far the tips of the patient’s fingers can reach down their legs when they bend forwards. The distance that they can reach is an indication of total spinal flexibility combined with hip flexibility.

Most patients cannot touch their toes, but some hypermobile patients can put the palms of their hands on the floor. Flexibility depends on fitness, age, gender and overall body mobility, and varies enormously between individuals.

Lateral deviation. Ask the patient to slide first one hand and then the other down the side of their thigh, bending laterally. The spine should bend smoothly from top to bottom. Total mobility can be recorded by noting the distance that each hand can move down the side of that thigh (Fig. 20.24).

Rotation. Stand behind the patient and hold their pelvis still with both hands. Ask the patient to twist round and look over their shoulder, first in one direction and then the other. Note the angle that the shoulder girdle can form with the pelvis (Fig. 20.24).

For these last three tests record whether any of the manoeuvres are limited by pain, and if so where.

  Passive

The Lasegue or straight leg raise test. This test can be painful and so should only be performed slowly while watching the patient’s face at all times. The test should be abandoned if pain becomes severe. It is a test of sciatic nerve irritability and relies on the fact that when the straight leg is flexed fully at the hip the roots of the sciatic nerve move as much as 2 cm through the vertebral foraminae. If the nerve is compressed and/or inflamed this movement will cause pain.

Pick up the leg least affected by the pain and gently bend the hip and the knee until both joints are fully flexed. Note the range of movement of both hip and knee.

Gradually straighten the knee, while allowing the hip to extend only as much as the patient feels is necessary for comfort. All patients will get some discomfort in the back of the thigh during this manoeuvre as the hamstring muscles are put on full stretch. While keeping the knee straight, let the hip drop 100 into extension so that any pain from tight hamstrings is relieved. Then take the foot and dorsiflex the ankle fully. This stretches the sciatic nerve. Pain in the back radiating down the full length of the leg indicates sciatic nerve irritation (Fig. 20.25).

The test should then be repeated with the opposite leg.

Resisted

 

Extensor hallucis longus is served purely by lumbar nerve root 5 (L5). It can be tested by comparing resisted extension of the tip of the big toes. Stand at the feet of the patient and press down on the big toenails of each patient while asking them to resist this pressure. If one distal phalanx drops into flexion easily compared with the other toe despite the best efforts of the patient, there is likely to be an L5 lesion (Fig. 20.7).

Testing for motor weakness

L5 is the commonest nerve root to he affected by a prolapsed intervertebral disc and is the only nerve root which is com­pletely responsible for serving one muscle (the extensor hallucis longus) and so is easy to test. The simplest test for compromise of L4 motor function is loss of the knee reflex and weakness in the quadriceps (demonstrated in the section on ‘The knee’). The ankle reflex is lost in S1 damage, but beware; it is commonly missing in elderly patients even without nerve root damage.