Study: Chiropractic Spinal Manipulation Reduces Tramadol Prescription for Radicular Low Back Pain

STUDY TITLE:

Chiropractic spinal manipulation and likelihood of tramadol prescription in adults with radicular low back pain: a retrospective cohort study using US data

AUTHORS:

Trager R, Cupler Z, Srinivasan R, et al.

AUTHOR’S AFFILIATIONS:

Connor Whole Health, University Hospitals Cleveland Medical Center, Cleveland; Department of Family Medicine and Community health, Case Western Reserve University School of Medicine, Cleveland; Department o Biostatistics and Bioinformatics Clinical Research Training Program, Duke University School of Medicine

PUBLICATION INFORMATION:

BMJ Open 2024 May 1; 14:e078105.

BACKGROUND INFORMATION:

Tramadol is an atypical, synthetic opioid that is often prescribed for low back pain. Previous studies have found that individuals with low back pain receiving spinal manipulation are less likely to be prescribed an opioid (1, 2). However, no study has specifically focused specifically on the use of tramadol.  

Tramadol stimulates opioid receptors and inhibits norepinephrine and serotonin reuptake (3). As a result of the overuse of opioids in the United States and elsewhere, tramadol may be prescribed in place of stronger potency opioids as it is often perceived as a safer alternative, with fewer and less severe adverse events (4). Several major clinical practice guidelines for low back pain do not provide recommendations for or against tramadol prescription. 

Considering the recent increase in tramadol prescribing for low back pain, the current study aimed to examine the association between receipt of spinal manipulation and tramadol prescription among adults with a new diagnosis of radicular low back pain. The authors hypothesized that adults receiving spinal manipulation would have a reduced likelihood of tramadol prescription relative to those receiving non-chiropractic medical care over a 1-year follow-up period.

PERTINENT RESULTS:

Following propensity score matching there were 1171 patients in each cohort with an average age of 35 years. After matching, no variables were significantly different between the cohorts at baseline. 

Overall, the proportion of patients who received a tramadol prescription during the 1 year following the diagnosis of radicular low back pain was lower in the spinal manipulation cohort compared to the usual care cohort. After propensity score matching, 1.3% of the spinal manipulation cohort had received a tramadol prescription, compared with 4% of the usual medical care cohort, yielding a risk ratio of 0.32 (in other words, a 68% risk reduction in those receiving chiropractic SMT!).

In the sensitivity analysis, the cumulative incidence graph suggested that the incidence of tramadol prescription in the usual medical care cohort increased relative to the SMT cohort early during follow-up, and the cumulative incidence curves did not converge during or at the end of the 1-year follow-up (suggesting that the significant difference in prescription incidence was maintained).

CLINICAL APPLICATION & CONCLUSIONS:

This is the first study to examine the association between chiropractic spinal manipulation and tramadol prescription. The results suggest that adults initially receiving spinal manipulation for a new diagnosis of radicular low back pain have a reduced likelihood of receiving a tramadol prescription over a 1 year follow-up. Both cohorts demonstrated similar utilization of usual medical care such as NSAIDs, physical therapy and lumbar spine imaging, and therefore the cohorts differed only in their receipt of spinal manipulation (which further strengthen these results). 

Although the spinal manipulation cohort had a small absolute reduction in tramadol prescription – about 3% – the potential clinical impact of such a reduction cannot be ignored. Potential adverse effects of tramadol use include addiction, physical dependence or long-term use. Therefore, a longer duration follow-up study that investigates these outcomes is warranted. 

This study found similar results as previous studies showing that patients receiving spinal manipulation for radicular low back pain were less likely to receive an opioid, benzodiazepine or gabapentin prescription. Future research should be conducted to corroborate these findings through a prospective study to minimize potential confounding variables.

STUDY METHODS:

The authors performed a retrospective cohort study. Due to the prescribing of tramadol increasing over the past decade, data was used from January 1, 2017 to November 9, 2023. The study data included deidentified, aggregated, electronic health records from 115 million patients seeking care across 80 academic healthcare institutions. 

Patients aged 18-50 were included who were suffering from a first occurring incident of radicular low back pain. Only radicular low back pain was included as tramadol is more often prescribed for this subset of low back pain (5, 6). Furthermore, the age bracket up to 50 was selected as radicular low back pain for this age group is more likely to result from a lumbar disc herniation compared to older patients more likely suffering from lumbar stenosis. 

Patients with radicular low back pain were included by requiring the presence of at least one of the several diagnostic codes describing lumbar or sacral radiculopathy or sciatica. Diagnoses describing disc degeneration or displacement were not included as this could cause localized low back pain without radicular symptoms. 

Patients were divided into two cohorts, depending on whether they did or did not receive spinal manipulation on the index date of their radicular low back pain diagnosis. Patients not receiving spinal manipulation on the index date of diagnosis formed the usual medical care cohort. For this study, usual medical care was considered to be any range of medical services such as medications, interventional procedures, surgery, health care encounters, physical therapy, or exercise.

Patients were excluded if they were prescribed opioids at baseline as only opioid-naïve patients were part of the new user design. As well, patients were excluded if they were prescribed any opioids within the preceding year or were suffering from serious pathology, had undergone previous lumbar surgery, had scoliosis, spondylolisthesis, lumbosacral plexopathy, myelopathy, fibromyalgia or multiple sclerosis. 

Tramadol prescriptions were identified by occurrence of its RxNorm code over a 1-year follow-up after the index date of the radicular low back pain diagnosis. As radicular low back pain typically improves over the course of 3 months to a year, a 1-year follow-up was considered clinically relevant. 

Propensity score matching was used to reduce bias, balancing confounding variables between cohorts associated with tramadol prescription (7). Confounders with a negative or positive association with tramadol prescription were selected. To help account for any potential patient preference of prescription medications in the spinal manipulation cohort, the authors controlled for receipt of any prescriptions in the year preceding the index date. Based on the available literature, covariates with a positive or negative association included antidepressants, asthma, demographics, medication prescription in the preceding year, gastrointestinal disorders, radiographs, and social determinants of health. 

A required sample size of 396 patients was calculated. The risk ratio for tramadol prescription was derived by dividing the risk in the spinal manipulation cohort by the risk in the usual medical care cohort. To provide better insight regarding the timing of prescriptions over follow-up, the authors conducted a post-hoc sensitivity analysis to graph the cumulative incidence of tramadol prescription per cohort. To examine the proportion and risk ratio of various treatments during follow-up, the authors added secondary outcomes of spinal manipulation in the usual medical care cohort and markers of usual medical care in both cohorts including physical therapy evaluations, non-steroidal anti-inflammatory drugs and a composite outcome of lumbar spine imaging. Risk ratio point estimates less than 0.73 and greater than 1.38 were used to represent meaningful between cohort differences.

STUDY STRENGTHS / WEAKNESSES:

Strengths:

The methodology used for this study was rigorous and well described (and has been utilized in a number of previously published studies).
This is the first study to provide an understanding of the association between SMT and tramadol prescriptions using a large, real-world database.

Weaknesses:

There may be unmeasured confounding variables and some variables such as income and education level may not have been sufficiently represented in the data set.
The database contains medical record data, but the authors did not have access to detailed patient charts to directly validate the results due to the deidentified, aggregated nature of the dataset sourced from multiple healthcare organizations. As a result, the authors may have misclassified patients according to having a new diagnosis of radicular low back pain.
Variables included in propensity score matching could have been incorrect or missing.
The study findings may not be generalizable to other practice settings or other countries outside of the USA as there may be different drug scheduling status for tramadol, prescription guidelines, or management strategies for low back pain.