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So you want to beat natural history?

The natural history of any condition refers to how a condition will progress in an individual over time if they do not receive any treatment. We know that if we leave certain conditions untreated, they will progress to the point of serious harm, or death. While for other conditions, they are likely to completely resolve without any intervention whatsoever. In common musculoskeletal conditions, (like neck pain or low back pain) we typically expect to see rapid improvement over the first few weeks to months without any intervention (1,2). However, we have also seen that complete resolution (a score of 0 on a pain scale) was only seen in 43% and 36% of people with neck pain and low back pain respectively in studies like the HUNT trial (2). Other studies, like the 2008 inception cohort study from Henschke et al. found that 72% of individuals presenting to general practitioner’s, chiropractors, or physiotherapists had complete resolution of their pain at 1 year (3). While we do see rapid improvement early, it does appear like further improvement tapers off after an initial period of recovery.

Is a complete 0/10 pain score a reasonable and attainable goal? Can people be pain free when we measure pain at 3 months, but then have a flare up that leads to them being in pain at 12 months? Those separate discussions to be had, and rabbit holes I will not be venturing down. Instead, let’s discuss pain and recovery trajectories, and how our treatments may or may not enhance that process.

The curious case of low back pain natural history (Author’s note post article completion: Shockingly, this has turned into a discussion on low back pain, and not the broader discussion of musculoskeletal pain. I am nothing if not predictable.) First, I’d be remiss if I didn’t discuss the PACE trial (4). The PACE trial (paracetamol/acetaminophen for acute low-back pain) is one of the most impressive and interesting trials in the treatment of low back pain. 1652 patients with acute low back pain were recruited, and assigned to either a regimented prescription of paracetamol, paracetamol as needed, or a placebo. The patients were also provided with “guideline recommended advice to remain active and avoid bed rest, and reassurance of the favourable prognosis of acute low-back pain”(4). To cut to the chase, there was no difference between the 3 groups. But maybe even more interestingly was the recovery curve of the participants within the study. I’ve included the graph from the paper, and let’s all collectively ask the Lancet to not sue me over this, I am very poor (this blog isn’t for profit!)

The mean onset of pain of participants was 9.9 days. So if we add that onto the median time to recovery, it looks like it took between three and four weeks for half of individuals to have a complete resolution of their back pain. By the time we get to the three-month mark, over 80% of individuals across all three groups had completely recovered. In this study, the authors defined recovery as the first day having a pain intensity of 0 or 1 out of 10, that was sustained for seven days. Using the definition of sustained recovery even implies that people may have technically recovered even quicker (depending on your definition) than the already reasonably quick recoveries found in the study.


A very similar survival curve can be found in the 2007 study by Hancock et al, that aimed to determine if adding NSAIDs (diclofenac), spinal manipulative therapy or both to usual recommended care would improve recovery in low back pain (5). Patients once again had a mean duration of symptoms of about 9 days prior to enrollment, and the median time to recovery ranged from 13-16 days across the four groups (SMT + diclofenac, diclofenac + placebo SMT, double placebo, and SMT + placebo diclofenac). By the end of the trial (12 weeks), 99% of participants across all groups were either recovered, or censored (5).


We’ve now talked about a few specific interventions, but in the management of low back pain, we certainly know that a wide range of treatment options exist. Thankfully, I don’t have to find graphs for all of these interventions. Instead, I can show you the work done by Artus et al, who in 2010 published a systematic review of clinical trials looking at interventions for non-specific low back pain (6). Once again, I am begging “Rheumatology” to not sue me.

In the graph above, 104 treatment arms from 45 trials, featuring the main/index treatment (red), an active comparator (blue) or usual care/waiting list/placebo arms (green) is presented. To quote the authors, “Response lines for all three outcome measures followed a pattern of common trend of improvement in symptoms represented by a rapid early reduction in mean outcome scores within the first 6 weeks followed by a slower reduction thereafter proceeding to a plateau at 6 months”. From here we can begin to see a very repetitive pattern that is maintained across a wide variety of treatment arms, ranging from doing absolutely nothing, to lots of contact time and intervention. From here, it is possible to argue that the interventions we can offer may not uniquely affect pain trajectories much more than other treatments. I view this as a positive opportunity, as it affords both clinicians and individuals seeking care the option to pursue many different treatment avenues (at least hopefully among recommended options).


Perhaps contrary to popular belief, I don’t actually hold favoritism to any particular intervention. A couple years ago I probably would’ve tried to find a way to spin this as a positive for whatever intervention I thought was the newest best thing. Maybe there’s a lesson here about personal growth? However, I think it’s important that we discuss the limitations and application of all interventions that we are able to provide to individuals. In a letter to the editor following the publication of the aforementioned HUNT trial, Dr. Chris Maher discusses the management of acute low back pain in an aptly titled section called “Do our treatments offer much more than the passage of time” (7). Since I am the farthest thing from an expert, I’ve included the direct quote that inspired the topic of today’s blog:

“The authors raise an interesting point when they comment that the natural history observed in the HUNT study is pretty similar to the clinical course reported in treatment trials [13]. This raises the challenging notion that our treatments for spinal pain are not offering much more than the passage of time.”

So where does that leave us? An argument against myself, sort of.


We need more research! Non-specific low back pain is an honest title, but it objectively does not help us apply targeted or tailored management for a condition that is so variable across individuals. Do we have anything more specific currently? It does not really seem so, but I’m an optimist on this front. I think we have an incredible amount of brilliant people working on this topic and tackling it from all angles. Things unfortunately take time and money.


About 18 months ago, I told a patient that the goal of treatment was to beat natural history. In hindsight, I’m not sure that the interventions I’m currently able to provide can accelerate the course of recovery in something like acute low back pain. Now, I do not equate that to the idea that clinicians do not provide useful and beneficial care, but quite the opposite. I think what the above discussion provides is a starting ground to better understand the true shared decision-making process in the clinical setting. Furthermore, I hope that we can provide appropriate management plans to patients that help them achieve their desired goal without overselling the benefits of any one specific intervention, or numerous treatment sessions in the short-term management of acute low back pain. Like all things on this side of the universe, it’s a complicated and nuanced discussion. Hopefully, we continue to help and support people to the best of our abilities, while acknowledging the current limitations that we are forced to work with.













References


1. Koes BW, Van Tulder M, Thomas S. Diagnosis and treatment of low back pain. Bmj. 2006 Jun 15;332(7555):1430-4.

2. Vasseljen O, Woodhouse A, Bjørngaard JH, Leivseth L. Natural course of acute neck and low back pain in the general population: the HUNT study. PAIN®. 2013 Aug 1;154(8):1237-44.

3. Henschke N, Maher CG, Refshauge KM, Herbert RD, Cumming RG, Bleasel J, York J, Das A, McAuley JH. Prognosis in patients with recent onset low back pain in Australian primary care: inception cohort study. Bmj. 2008 Jul 7;337.

4. Williams CM, Maher CG, Latimer J, McLachlan AJ, Hancock MJ, Day RO, Lin CW. Efficacy of paracetamol for acute low-back pain: a double-blind, randomised controlled trial. The Lancet. 2014 Nov 1;384(9954):1586-96.

6. Artus M, van der Windt DA, Jordan KP, Hay EM. Low back pain symptoms show a similar pattern of improvement following a wide range of primary care treatments: a systematic review of randomized clinical trials. Rheumatology. 2010 Dec 1;49(12):2346-56.

7. Maher CG. Natural course of acute neck and low back pain in the general population: The HUNT study. Pain. 2013 Aug 1;154(8):1480-1.