I’ve had back pain since I was 16 years old. It’s one of the reasons I became a physiotherapist, and it's something I’m passionate about as a resident family medicine physician.
Despite all the knowledge we have about back pain in medicine, we’re just not very good at treating it. We order inappropriate tests, scare our patients with medical jargon, and overcomplicate a normal human experience.
Eighty percent of people will experience low back pain in their lives. If you get it once, you have a pretty good chance of getting it again. So, as healthcare providers, we need to avoid pathologizing low back pain, and help patients to manage their own pain.
In the next few posts, I’m going to go through my strategies for the initial assessment of acute low back pain. I used this series from the Lancet and this article from CMAJ as my main references.
But first, a couple of caveats:
This post is geared towards acute low back pain (meaning it's been going on for less than 2-4 weeks.)
It only applies in outpatient primary care; working in a more acute setting changes the pre-test probability for serious pathology, which necessitates a different approach.
Part 1: Identify concerning causes of low back pain
In this post, we’re going to go through a quick way of weeding out serious pathology and non-spinal causes of low back pain. Reassurance is a mainstay of treatment for most low back pain, and in order to reassure, we need to be confident that the patient doesn’t have a sinister source of pain.
Less than 1% of people who see a primary care provider about low back pain will have serious pathology. For instance, many primary care providers won't see cauda equina syndrome in their careers.
(That said, I saw this condition once as a physiotherapist. I sent my patient to the ED where they had emergency neurosurgery. Phew!)
However, we need to screen for conditions that require immediate attention or further workup. That’s why I start by scanning the chart.
1. Scan the chart for risk factors
I scan the chart quickly for things that may increase the pre-test probability for serious pathology or non-spinal causes of back pain. I look for:
IV drug use, which increases the risk of spinal infections
Risk factors for tuberculosis, which can manifest as spinal infection
Personal history of cancer, especially breast, prostate or lung cancer, as these tend to metastasize to bone
Risk factors for an abdominal aortic aneurysm
Known kidney stones, hip disease, osteoporosis, or endometriosis
2. Tailor your questions based on your chart review
Most people with low back pain have a red flag. As the Lancet article highlights:
“Nearly all recommended individual red flags are uninformative and do not substantially change post-test probabilities of a serious abnormality.”
Before I see a patient, I like to write down which red flags or symptoms I want to ask about so that I don’t blindly run through the full list of red flags with every person.
For example, if my chart review revealed that a patient had a history of using IV drugs, I would ask about fever and chills. And if they had a kidney stone in the past, I’d ask about urinary symptoms.
3. Ask about trauma
Don’t forget to ask specifically about any kind of trauma. People might forget that they fell a couple days before the back pain started. This is especially important in people with known osteoporosis or risk factors for osteoporosis.
Consider getting an x-ray for anyone at risk for osteoporosis who experienced minimal trauma, like a fall from standing, or for younger people who had a higher impact trauma, like a fall off a ladder.
But be careful – an x-ray is to assess for fracture. Outside of bony pathology, x-rays can’t diagnose the cause of low back pain.
4. Do a focussed physical exam
In a 10-15-minute appointment, I’m trying to focus my physical exam on what will change my management. In low back pain, I have 5 things I want to assess in every patient, and 5 things that I may check based on a patient’s history.
Here are the five main components of my low back exam:
Spine inspection – look for SEADS, which stands for swelling, erythema, muscle atrophy, deformity, and skin changes
Gait – assess for neurologic gait patterns and foot drop
Reflexes – patellar, Achilles, and Babinski; you’re looking for upper or lower motor neuron problems
Power – I do this by testing heel walking, toe walking, and then the rest of the lower extremity key muscles in sitting
Lumbar spine range of motion – I test this in standing. If it’s limited in a certain direction, it adds support for a mechanical cause of back pain.
And here are the additional things I might check:
Abdomen – assess for pulsatile masses
Digital rectal exam – for patients who present with cauda equina symptoms (fecal incontinence, urinary retention, saddle anesthesia, bilateral leg weakness); get consent and ideally a chaperone, and test for rectal tone and saddle numbness
Temperature – check for fever if you suspect infection
Straight leg raise – use if a patient has leg symptoms, as a positive test helps diagnose radiculopathy. Note: the test is only positive if it reproduces their symptoms.
Light touch sensation – use if a patient reports paresthesia
5. Include a differential diagnosis
Early in residency, my preceptor advised that I document what diagnoses I considered in my assessment. This could look like the following for a 65-year-old with recurrent low back pain and no red flags:
Provisional diagnosis: nonspecific low back pain
Ddx: considered AAA but no pulsatile masses, no symptoms of cauda equina
This is a useful practice for two reasons: First, it helps show others your thought process. Second, it forces you to consider alternative diagnoses. This is especially important because 90-95% of the time, the diagnosis is going to be nonspecific low back pain. You’ll see it so often that you might miss that one person out of ten who has something else going on (aka availability bias).
6. Have a plan for follow up
Lastly, the beauty of primary care is that you can follow a patient's progress over time. Some causes of low back pain only reveal themselves after multiple assessments; it may take a few visits to figure out that a patient has a rare but serious cause of pain.
When I was a physiotherapist, I saw a 25-year-old with a few weeks of spontaneous low back pain. He had no red flags, and his only physical exam finding was that his range of motion was restricted in all directions.
I gave him my usual spiel about the natural history of low back pain: most flares get better in a couple weeks on their own, and almost all flares will be significantly better in 6 weeks.
For my patient, his pain was getting worse as the weeks went by. I asked him to see his family doctor since this wasn't fitting with mechanical low back pain. Long story short, he was diagnosed with ankylosing spondylitis.
So, in healthcare in general, make sure you provide patients with a good follow up plan.
In this post, I went through how to identify cause for concern when someone presents to a primary care clinic with acute low back pain. In the second installment of this series, I’ll go through more about diagnosing acute low back pain once you’ve ruled out the bad stuff.
Until then, stay well friends.
Dr. Kuhnow
This post is meant for educational purposes only, and doesn’t replace advice from your qualified healthcare professional.
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