Low back pain: clinical examination is key

IN my work as a GP, I have often in the course of the week come across patients with low back pain. The second most common complaint in doctors' practices globally is low back pain. If you want to know what No 1 is, it's a cough or cold. Pain is real to all patients but it can be subjective. On a good day, there is less pain; on a bad day, there is more pain. If one wins the lottery there may be no pain!

Hence to the doctor what is important is the examination. When we examine a patient with low back pain, we are looking for a slipped disc. This usually triggers a pinched nerve that triggers a pain that shoots from the lower back through the thigh to the leg and into the foot. This pain that comes from a pinched nerve is called sciatica.

We will ask the patient to lie down on the examination couch and raise his straightened leg up to 90 degrees. We call this test "straight leg raising". If there is sciatica, we will trigger it at a lower angle than 90 degrees.

The next thing we do is to test the reflexes of his knees and ankles with a tendon hammer. If the reflexes are absent, it can indicate where the problem may lie in the lumbar spine.

You may have heard of the lumbar vertebra and there are five of them. They are named L1, L2, L3 to L5 and the tail bone or sacrum starts at S1 and ends in S4. Most of the problems we see in the lumbar sacral spine occurs at L4 to S1. If the knee reflex is intact, it means that L2 to L4 are fine. If the ankle reflex is normal, it means that S1 is fine. We are missing the critical L5 and we use power to test that. The test we use is the power of the big toe. If the big toe is at full strength pointing upwards, it means that L5 is fine.

Hence where pain is subjective, the straight leg raising test, the reflexes and the power of the big toes can tell us that most of the lumbar sacral spine is normal. What is the role of imaging then? We do an X-ray to make sure the vertebra are fine. An MRI scan may be useful if we find an absent reflex or weakness. We tend not to do the MRI scan for pain unless the pain has been present for eight weeks or more. This is because most low back pain will resolve itself within eight weeks.

The MRI scan has beautiful pictures that can convince most patients to go for surgery. There are studies where patients are taken off the streets and given an MRI scan. They found slipped discs in the majority of these asymptomatic patients but these people are perfectly fine. Hence the clinical examination is still paramount to contextualise what we see in the scan.

We would usually send the patient for physiotherapy and prescribe anti-inflammatory medication for pain with muscle relaxants to resolve spasm. Some patients are sent for physiotherapy without an MRI scan but if the physiotherapist is unhappy with progress of the patient, they will send the patient back to us to order an MRI scan.

Some patients choose to use alternative therapies from chiropractor to osteopaths to Traditional Chinese Medicine practitioners. Medical practitioners do not work with such alternative medical practitioners but I notice that patient satisfaction may be quite high with these alternative therapies.

If the patient is not well after a course of therapy, we will send the patient for a surgical opinion. We usually emphasise to the patient that an operation in the presence of persistent sciatica, absent reflex or weakness of muscles may be useful. Remember that these matters are not life and death but all about quality of life. Hence we have to balance the risk of the surgery versus the quality of life.

Quality of life to most patients involves how much pain they have to bear with. Pain can be continuous, can be present at rest and can be nocturnal, disturbing the patient's sleep.

Intensity of pain is difficult to quantify. We have many pain scores but it is challenging for doctors to assess how intense the pain is for the patient. We do fortunately have medication to relieve pain. These includes pain-killers or anti-inflammatories called NSAIDs.

We often have to prescribe accompanying medicine to protect the patient from gastritis. Another drug we use is a coxib - this is a class of anti-inflammatory medication that is useful; most doctors like etoricoxib.

We also use paracetamol that is combined with codeine. Unfortunately, this can also cause nausea and vomiting as a side-effect. We can also escalate the pain relief to opiate analgesics such as tramadol. Other adjuncts we use are pregabalin that is useful if the pain is nerve-related.

Finally, we would still prefer to send a patient for surgery if the patient does not only have pain symptoms but also have impairment of reflexes, loss of strength or numbness that correspond to a part of the body known to be supplied by a particular nerve root.

Surgery for pain is more likely to have a poorer outcome; surgery to address a clinical sign or symptom is far likely to have a better outcome.

This series is produced on alternate Saturdays in collaboration with Singapore Medical Specialists Centre.