Chronic opioid therapy diminishes lumbar fusion outcomes in workers’ compensation patients

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Extended opioid therapy following lumbar fusion surgery for US workers’ compensation patients is associated with worse outcomes, a new study has found. Published by Spine, the results add weight to the argument that the significant increase in opioid treatments in recent years has caused many secondary problems.

Few studies have evaluated risk factors for chronic opioid therapy among the clinically-distinct workers’ compensation population. The authors, led by Joshua T Anderson, Case Western Reserve University School of Medicine, Cleveland, USA, designed a retrospective cohort study to investigate the effects of opioid usage following lumbar fusion procedures to treat degenerative disc disease in workers’ compensation patients from 1993–2013.

The use of opioid analgesics for the treatment of pain has increased substantially over the past decade, something that is especially true for chronic low back pain. This over-prescription of opioids is a growing public health concern that has been associated with high rates of substance abuse disorders, hospital admissions, overdose deaths and pain over-sensitivity. Anderson et al note that the existing literature “does not support opioids as being more effective than other groups of analgesics for chronic low back pain, and that no information exists from randomised controlled trials supporting the efficacy and safety of opioids if used for more than four months.”

Furthermore, lumbar fusion surgery for degenerative disc disease and discogenic low back pain (discogenic fusion) has been associated with variable clinical outcomes, especially with workers’ compensation patients, who generally have worse outcomes than the general population. This means that postoperative long-term opioid therapy carries additional risks for this procedure and in this patient population. Anderson and colleagues note that the prevalence of opioid use among the entire workers’ compensation population is approximately 32%.

Using Current Procedural Terminology and ICD-9 codes, the study group identified Ohio workers’ compensation subjects who underwent lumbar fusion for degenerative disc disease in the specified timeframe. Postoperative chronic opioid therapy was defined as “being supplied with opioid analgesics for greater than one year after the six-week acute period following fusion”. The chronic opioid therapy group was formed of 575 subjects who fit these criteria, with the remaining 427 subjects forming a temporary opioid group. To identify prognostic factors associated with chronic opioid therapy after fusion, the authors conducted a multivariate logistic regression analysis.

Anderson et al report that returning to work was negatively associated with chronic opioid therapy (p<0.001; odds ratio 0.38). Opioid therapy before fusion (p<0.001; odds ratio 6.15), failed back syndrome (p<0.001; odds ratio 3.40), additional surgery (p<0.001; odds ratio 2.84), clinically-diagnosed depression (p<0.001; odds ratio 2.34), and extended work loss before fusion (p=0.038; odds ratio 1.61) were all positively associated with opioid therapy. The rates of postoperative opioid therapy associated with these factors were 27.8%, 79.6%, 85%, 76.4%, 77.1%, and 61.3%, respectively.

“Higher preoperative opioid load (p<0.001) and duration of use (p<0.001) were positively associated with higher postoperative rates of postoperative chronic opioid treatment,” the authors write. Within three years of fusion, the chronic opioid group was supplied with an average of 1,083.4 days of opioids and 49 opioid prescriptions, 86.2% of which were schedule II. The chronic opioid treatment group had an 11% return to work rate, US$27,952 higher medical costs (paid for by the Ohio Bureau of Workers’ Compensation) per subject, a 43.5% rate of psychiatric comorbidity, a 16.7% rate of failed back syndrome, and a 27.7% rate of additional lumbar surgery.

“The overall poor outcomes of this study could suggest a more limited role for discogenic fusion among patients receiving workers’ compensation,” propose the authors. “Future studies should be aimed at determining if discogenic fusion can improve function and quality of life in this clinically-distinct population.”

“We hope that our study provides some insight into opioid utilisation among the workers’ compensation population and which patients are more likely to end up on chronic opioid therapy after fusion,” conclude Anderson et al.