SPINE Volume 40, Number 22, pp 1775–1784 ß 2015 Wolters Kluwer Health, Inc. All rights reserved
OCCUPATIONAL HEALTH/ERGONOMICS
Chronic Opioid Therapy After Lumbar Fusion Surgery for Degenerative Disc Disease in a Workers’ Compensation Setting Joshua T. Anderson, BS, Arnold R. Haas, BS, BA,y Rick Percy, PhD,y Stephen T. Woods, MD,y Uri M. Ahn, MD,z and Nicholas U. Ahn, MD
Study Design. Retrospective cohort study. Objective. To evaluate prescription opioid use after lumbar fusion for degenerative disc disease in a workers’ compensation (WC) setting. Summary of Background Data. Use of opioids for treating chronic low back pain has increased greatly. Few studies have evaluated risk factors for chronic opioid therapy (COT) among the clinically-distinct WC population. Methods. We used ‘‘Current Procedural Terminology’’ and ‘‘International Classification of Diseases, Ninth Revision’’ codes to identify 1002 Ohio WC subjects who underwent lumbar fusion for degenerative disc disease from 1993 to 2013. Postoperative COT was defined as being supplied with opioid analgesics for greater than 1 year after the 6-week acute period after fusion. 575 subjects fit these criteria, forming the COT group. The remaining 427 subjects formed a temporary opioid group. To identify prognostic factors associated with COT after fusion, we used a multivariate logistic regression analysis. Results. Returning to work was negatively associated with COT (P < 0.001; odds ratio [OR] 0.38). COT before fusion (P < 0.001; OR 6.15), failed back syndrome (P < 0.001; OR 3.40), additional surgery (P < 0.001; OR 2.84), clinically diagnosed depression (P < 0.001; OR 2.34), and extended work loss before fusion
From the University Hospitals Case Medical Center Department of Orthopaedics, Case Western Reserve University School of Medicine, Cleveland, OH; yOhio Bureau of Workers’ Compensation, Columbus, OH; and zNew Hampshire NeuroSpine Institute, Bedford, NH. Acknowledgment date: March 11, 2015. First revision date: May 20, 2015. Acceptance date: July 6, 2015. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. Relevant financial activities outside the submitted work: consultancy, expert testimony, payment for lectures, patents, royalties, stocks, grants, travel/ accommodations/meeting expenses. Address correspondence and reprint requests to Joshua T. Anderson, BS, University Hospitals Case Medical Center Department of Orthopaedics, Case Western Reserve University School of Medicine, 11100 Euclid Avenue, Cleveland, OH 44106; E-mail: [email protected] DOI: 10.1097/BRS.0000000000001054 Spine
(P ¼ 0.038; OR 1.61) were positively associated with COT. The rates of postoperative COT associated with these factors were 27.8%, 79.6%, 85.0%, 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 COT. Within 3 years after fusion, the COT group was supplied with an average of 1083.4 days of opioids and 49.0 opioid prescriptions, 86.2% of which were Schedule II. The COT group had an 11.0% return to work rate, $27,952 higher medical costs per subject, 43.5% rate of psychiatric comorbidity, 16.7% rate of failed back syndrome, and 27.7% rate of additional lumbar surgery. Conclusion. The majority of the study population was on COT after fusion. COT was associated with considerably worse outcomes. The poor outcomes of this study could suggest a more limited role for discogenic fusion among WC patients. Key words: workers’ compensation, lumbar fusion, lumbar arthrodesis, degenerative disc disease, discogenic low back pain, chronic low back pain, opioid use, narcotic use, clinical outcomes, chronic opioid therapy, opioid dependence, return to work, prognostic factors, predictors, work loss. Level of Evidence: 3 Spine 2015;40:1775-1784
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se of opioid analgesics for the treatment of noncancer pain has increased substantially during the past decade.1,2 This is especially true for Schedule II opioids for chronic low back pain (LBP). It is a growing public health concern that has been associated with high rates of substance abuse disorders, narcotic-related hospital admissions, and overdose deaths.1,3–6 Chronic, high-dose opioids may also lead to abnormal pain sensitivity, that is,. opioid-induced hyperalgesia.4 A recently updated Cochrane review by Chaparro et al reported that some support exists for the effectiveness of opioids for LBP in the short term, that the literature generally does not support opioids as being more effective than other groups of analgesics for chronic LBP, and that no information exists from randomized controlled trials (RCTs) supporting the efficacy and safety of opioids if used for more than 4 months.7 www.spinejournal.com
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OCCUPATIONAL HEALTH/ERGONOMICS Their review consisted of 15 RCTs published between 2000 and 2012, totaling 5540 participants, with the longest trial lasting 15 weeks.8 For primary outcome measures, included RCTs must have reported: pain intensity, function, global improvement, and/or proportion of patients reporting 30% or 50% pain relief. Compared with placebo, there is low-to-moderate-quality evidence that tramadol and strong opioids improve both pain and functional outcomes. They also reported very low-quality evidence that transdermal buprenorphine is better than placebo at improving pain and functional outcomes. Compared with other drugs, the review reported very low-quality evidence that tramadol is better than celecoxib in reducing pain and very lowquality evidence that nortriptyline or flupirtine has no difference in pain outcomes or functional status compared with opioids. Their study is consistent with another recent review by Kuijpers et al.9 However, both reviews highlighted the need for higher quality RCTs and more RCTs to better assess long-term opioid therapy for chronic LBP.7,9 Furthermore, lumbar fusion surgery for degenerative disc disease (DDD) and discogenic LBP also referred to as discogenic fusion, has been associated with variable clinical outcomes, particularly when compared with fusion for more definable instability, such as spondylolisthesis.10–18 Some RCTs have reported significant improvement in Oswestry Disability Index (ODI) after discogenic fusion, but upon pooling data in a meta-analysis, Bydon et al recently reported no significant difference compared with nonoperative therapy.18 DDD and discogenic LBP are estimated to now be the most common indications for lumbar fusion in the United States, as rates of discogenic fusion have increased approximately 220% since 1990.15,19 Workers’ compensation (WC) subjects tend to have worse lumbar fusion outcomes than the general population.14,20–27 Gum et al21 and Carreon et al23 published case-controlled studies comparing lumbar fusion outcomes at 2 years between WC patients and noncompensated controls. Gum reported significantly less improvement in ODI score (5.5 vs. 15.2) and back (0.9 vs. 2.5) and leg pain (0.9 vs. 2.2) scores in the WC group.21 Carreon reported significantly less improvement in mean ODI (4.9 vs. 13.3) and Short Form 36 Health Survey, Physical Component Summary (SF-36 PCS) scores (1.3 vs. 3.9) among WC subjects. Both studies reported significantly lower rates of substantial clinical benefit among WC patients in leg and back pain scores21 and ODI and SF-36 PCS.23 Additionally, studies of WC subjects from several states report return to work (RTW) rates ranging from 26% to 36%, reoperation rates from 22% to 27%, and high rates of chronic opioid use after fusion.14,16,24–28 The prevalence of opioid use among the entire WC population is approximately 32%.29 Receiving opioids early for acute LBP in a WC setting has been associated with higher rates of disability, surgery, and chronic opioid therapy (COT).30–32 Relatively few studies evaluate risk factors for worse lumbar fusion outcomes and opioid dependence within this clinically-distinct population.14,16,24,28,33,34 Therefore, the 1776
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objectives of our study were to evaluate opioid analgesic use within a large WC population who underwent discogenic lumbar fusion, to compare postoperative outcomes between those who ended up on COT after discogenic fusion and those who did not, and to identify predictive factors associated with postoperative chronic opioid dependence. We hypothesized that subjects requiring chronic opioid analgesia after fusion will also be associated with worse clinical outcomes.
MATERIALS AND METHODS This is a retrospective observational study consisting of 1002 WC subjects from the Ohio Bureau of Workers’ Compensation (BWC) who underwent lumbar fusion for DDD and discogenic LBP. We initially used ‘‘International Classification of Diseases, Ninth Revision’’ (ICD-9) codes to identify 14,640 subjects from the Ohio BWC’s administrative database who were diagnosed with lumbar disorders after workplace injury from 1993 to 2013. We next used ‘‘Current Procedural Terminology’’ codes and a previously published coding schema to identify subjects with lumbar fusion and characterize each surgery.14,28 We centered our study and all outcome measures around each subject’s index fusion surgery after workplace injury, because subjects may have undergone multiple fusion surgeries while receiving WC. Next, we excluded 13,638 subjects from the initial 14,640 identified who did not undergo lumbar fusion, underwent fusion for an indication other than DDD and discogenic LBP, underwent a fusion approach different than anterior, posterior, or 3608, or had fewer than 3 years of follow-up after fusion. We included subjects who only underwent these fusion approaches to help eliminate heterogeneity within the population. We also excluded those with prior lumbar surgery while on WC, a smoking history, or failed back syndrome, because these factors have been reported to negatively influence fusion outcomes.13,24,35–38 We identified lumbar comorbidities and failed back syndrome using ICD-9 codes, smoking history with ICD-9 codes and use of prescription smoking deterrents, and prior lumbar surgery using Current Procedural Terminology codes. See Table 1 for the coding used to identify our study population. 1002 subjects fit our study design, and thus comprised the final discogenic fusion cohort. The primary outcome of this study was if subjects required COT after fusion. Specifically, we defined postoperative COT as being supplied opioid analgesics for more than 1 year after the immediate 6-week postoperative period. Using prescription opioid data and the number of days each prescription was written for, we identified 575 subjects on postoperative COT, thus forming the COT group. The remaining 427 subjects formed the temporary opioid therapy (TOT) group. See Figure 1 for our subject selection flow chart. In addition to days supplied, we also determined the total morphine equivalents, average daily morphine equivalents, number of opioid prescriptions filled, and percent of prescriptions that were Schedule II opioids for all subjects, both within 1 year before index fusion and between the end of the 6-week acute November 2015
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OCCUPATIONAL HEALTH/ERGONOMICS TABLE 1. Coding Used for Study Population Fusion Technique
CPT Code
Posterior lumbar fusion (PLF) Single level 22612 Multilevel 22612 þ 22614 Posterior lumbar interbody fusion (PLIF) Single level 22630 or 22633 Multilevel 22630 or 22633 þ 22632 or 22634 Anterior lumbar interbody fusion (ALIF) Single level 22558 Multilevel 22558 þ 22585 Lumbar Comorbidity ICD-9 Code Degenerative disc disease 722.52, 722.73, or 722.93 Disc herniation 722.10 Spondylosis 721.3 Lumbar sprain 847.2 Radiculopathy 724.4 or 729.2 CPT indicates Current Procedural Terminology; ICD-9, International Classification of Diseases, Ninth Revision.
postoperative period and 3 years after index fusion. We defined preoperative COT as being supplied with more than 120 days of opioid analgesics within the 1-year period before fusion. Furthermore, we obtained data on each subject’s age at fusion, sex, preoperative time out of work, use of physical therapy, chiropractic care, psychotherapy, and approximated income. Exact income values were unavailable to us, so we correlated each subject’s zip code of residence to a mean per capita income value based upon the 2010 US Census. We determined preoperative rates of lumbar discography, legal representation, obesity, being older than 50 at fusion, being out of work greater than 12 weeks, and psychiatric and lumbar comorbidities. Additionally, we measured a number of secondary outcomes within 3 years
Chronic Opioid Therapy and Workers’ Compensation Anderson et al
after fusion. These included: RTW status, total days out of work, medical costs paid by the Ohio BWC, new onset psychiatric disorder(s), psychotherapy use, and rates of failed back syndrome, pseudoarthrosis, permanent partial and total disability benefit payments, all-cause mortality, and additional lumbar surgery. To identify prognostic factors associated with postoperative COT, we used a multivariate logistic regression analysis. The dependent variable was whether or not subjects were on COT after fusion. With our analysis, we adjusted for a number of important covariates, all at once. We did not use a stepwise regression model. We adjusted for the following binary variables: RTW status after fusion, if a subject was diagnosed with failed back syndrome after fusion, if a subject underwent additional lumbar surgeries after fusion, if subjects were out of work more than 12 weeks before fusion, multi versus single level fusion, concurrent decompression with fusion, if a subject was receiving permanent disability payments either before or after fusion, age more than 50 at fusion, obese, sex, per capita income above the population’s 50th percentile, if a subject underwent evaluation with discography preoperatively, presence of individual psychiatric and lumbar comorbidities, if the number of physical therapy sessions used was greater than the population’s 50th percentile, if the number of chiropractic sessions used was greater than the population’s 50th percentile, if subjects were on COT before fusion, if mean preoperative daily morphine equivalents were greater than 50, and if subjects had legal representation. We adjusted for the following categorical variables: lumbar fusion approach, instrumentation, and graft type. We compared secondary outcomes and baseline population characteristics between the COT and TOT groups using x2 tests for binary and categorical variables and t tests for continuous variables. P 0.05 was considered statistically significant. For all analyses, we used Statgraphics Centurion XVI software (Statpoint Technologies, Inc.; Warrenton, VA).
Figure 1. We used International Classification of Diseases, Ninth Revision (ICD-9) and Current Procedural Terminology (CPT) codes to identify our discogenic fusion cohort. DDD indicates degenerative disc disease; LBP, low back pain. Spine
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OCCUPATIONAL HEALTH/ERGONOMICS RESULTS Table 2 contains data on important preoperative population characteristics between the COT and TOT groups. Within the year before fusion, subjects in the COT group were supplied with opioid analgesics for 186.5 22.4 more days (P < 0.001) and filled 8.3 1.2 more opioid prescriptions (P < 0.001), which equated to 12,000.8 2176.9 additional morphine equivalents (P < 0.001) and a 7.8 7.4 morphine equivalent higher daily opioid load (P ¼ 0.038). On average, 79.9% of prescription opioids written for subjects in the COT group were Schedule II opioids, compared with 63.2% among the TOT group (P < 0.001). The COT group had a 44.3% higher rate of COT before fusion (P < 0.001) and a 10.2% higher rate of daily opioid loads greater than 50 morphine equivalents (P < 0.001). Additionally, before fusion, subjects in the COT group were out of work 190.7 76.6 more days (P < 0.001) and had a 5.9% higher rate of psychiatric disorders (P < 0.001), chiefly depression (P ¼ 0.002), a 13.3% higher rate of being out of work greater than 12 weeks (P < 0.001), 5.4% higher rate of psychotherapy use (P ¼ 0.006), 10.1% higher rate of undergoing discography (P ¼ 0.002), 7.3% lower rate of using chiropractic care (P ¼ 0.019), 6.5% higher rate of legal representation (P ¼ 0.010), and a 3.8% higher rate of spondylosis (P ¼ 0.018). Table 3 includes data pertaining to each subject’s fusion surgery. The COT and TOT groups only differed significantly in rates of different fusion approaches (P ¼ 0.049). Notably, the COT group underwent a 5.0% lower rate of posterior lumbar fusion and 5.9% higher rate of posterior lumbar fusion plus interbody fusion. Table 4 contains data on all predictive factors associated with postoperative COT from the regression model as well as postoperative opioid analgesic use associated with each variable. 57.4% (575/1002) of all subjects ended up on COT after the immediate 6-week postoperative period after fusion. The ability to RTW within 2 years of fusion was negatively associated with COT (P < 0.001; odds ratio [OR] 0.38). COT before fusion (P < 0.001; OR 6.15), failed back syndrome (P < 0.001; OR 3.40), additional surgery (P < 0.001; OR 2.84), clinically diagnosed depression, either before or after fusion (P < 0.001; OR 2.34), and prolonged time out of work before fusion (P ¼ 0.038; OR 1.61) were all positively associated with COT. The lowest rate of COT was seen among those who were able to RTW at 27.8%, with the highest seen among those with failed back syndrome at 85.0%. The strongest predictor of postoperative COT was preoperative COT. Subjects with positive factors were on opioid analgesics not only longer, but also with higher daily opioid loads and higher rates of Schedule II opioids. If subjects associated with any positive factor were removed, the COT rate decreases to only 10.7% (8/75). However, 92.5% of subjects had 1 or more positive factors. Figure 2 demonstrates the rates of postoperative COT associated with each predictive factor and rates of COT if subjects associated with each factor were removed. 1778
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Figure 3 and Figure 4 illustrate the impact preoperative duration of opioid use and preoperative net opioid load had on rates of postoperative COT. After receiving more than 60 days of opioids, subjects were associated with increasingly higher rates of postoperative COT (P < 0.001). 87.1% of subjects who received more than 240 days of opioids within the year before fusion ended up on COT postoperatively and were 16.01 times more likely to end up on postoperative COT than those who received fewer than 7 days of opioids preoperatively. Similarly, as total preoperative opioid load increased above 5000, so did postoperative rates of COT. 90.4% of subjects supplied with more than 25,000 morphine equivalents before fusion ended up on COT after fusion. Subjects receiving more than 25,000 morphine equivalents through opioid prescriptions before fusion were also 15.69 times more likely to end up on COT after fusion compared with subjects who received fewer than 5000 morphine equivalents before fusion. Table 5 includes data on all outcome measures and compares them between the COT and TOT groups. Not surprisingly, those who ended up on COT after fusion experienced considerably worse outcomes after fusion. Regarding opioid analgesia from 6 weeks to 3 years after fusion, subjects on COT were, on average, supplied with 985.1 50.8 additional days of opioids (P < 0.001) and filled 41.4 2.4 more opioid prescriptions (P < 0.001), which equated to 78,043.0 8879.5 additional morphine equivalents (P < 0.001) with a 24.4 7.5 morphine equivalent higher daily opioid load (P < 0.001). On average, 86.2% of prescription opioids written for subjects in the COT group after fusion were Schedule II, compared with 69.9% in the TOT group (P < 0.001). Compared with the rates before fusion, these rates increased 6.3% and 6.7% after fusion among the COT and TOT groups, respectively. Daily opioid loads and rates of Schedule II opioids increased after fusion between both groups. However, this increase was much more pronounced in the COT group, especially daily opioid load. Within 3 years after fusion, the COT group was also out of work 197.4 37.3 additional days (P < 0.001), cost the Ohio BWC $27,962.5 $4624.4 more per subject (P < 0.001), and had a 27.4% lower RTW rate (P < 0.001), 20.0% higher rate of new onset psychiatric disorder(s) (P < 0.001), 12.7% higher rate of failed back syndrome (P < 0.001), 7.4% higher rate of total permanent disability payments (P ¼ 0.002), and a 16.2% higher rate of additional lumbar surgery after fusion (P < 0.001). Postoperative rates of psychotherapy use increased 26.4% (P < 0.001) and 11.0% (P < 0.001) compared with those before fusion in the COT and TOT groups, respectively. The COT (P < 0.001) and TOT (P ¼ 0.023) groups used 7.1 2.5 and 2.3 2.0 more psychotherapy sessions after fusion compared with before. Also, the COT group underwent a 24.8% higher rate of first-time psychological diagnostic examination after fusion than before (P < 0.001). These data suggest worsening psychiatric health after fusion as well as a potential impact for better screening and treatment of psychiatric disease before performing lumbar fusion among WC patients. November 2015
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OCCUPATIONAL HEALTH/ERGONOMICS
Chronic Opioid Therapy and Workers’ Compensation Anderson et al
TABLE 2. Preoperative Population Characteristics Characteristic
COT Group
TOT Group
No. of subjects Age at index fusion, mean SD Subjects over 50 at index fusion, no. (%) Sex Male, no. (%) Female, no. (%) Days out of work BIF, mean SD Subjects out of work >12 wk, no. (%) Psychiatric history, no. (%) Depression, no. (%) Anxiety, no. (%) Adjustment reaction, no. (%) Psychological diagnostic examination, no. (%) Psychotherapy use, no. (%) Number of sessions, mean SD Permanent disability benefits, no. (%) Permanent partial, no. (%) Permanent total, no. (%) Lumbar discography, no. (%) Physical therapy, no. (%) Mean number of sessions, mean SD Chiropractic care, no. (%) Mean number of sessions, mean SD Legal representation, no. (%) Opioid analgesic use within 1 yr BIF Days suppliedy, mean SD Subjects supplied for >120 d, no. (%) Net MEQs supplied, mean SD Mean daily MEQs, mean SD >50 MEQs per day, no. (%) No. of prescriptions filled, mean SD Avg.% of Rx Schedule IIz, mean SD Lumbar comorbidity Disc herniation, no. (%) Radiculopathy, no. (%) Spondylosis, no. (%) Lumbar sprain, no. (%)
575 44.5 8.4 132 (23.0%)
427 44.4 8.9 117 (27.4%)
383 (66.6%) 192 (33.4%) 672.1 640.1 517 (89.9%) 72 (12.5%) 65 (11.3%) 8 (1.4%) 6 (1.0%) 74 (12.9%)
279 (65.3%) 148 (34.7%) 481.4 568.2 327 (76.6%) 28 (6.6%) 24 (5.6%) 1 (0.2%) 4 (0.9%) 39 (9.1%)
OCCUPATIONAL HEALTH/ERGONOMICS
Chronic Opioid Therapy After Lumbar Fusion Surgery for Degenerative Disc Disease in a Workers’ Compensation Setting Joshua T. Anderson, BS, Arnold R. Haas, BS, BA,y Rick Percy, PhD,y Stephen T. Woods, MD,y Uri M. Ahn, MD,z and Nicholas U. Ahn, MD
Study Design. Retrospective cohort study. Objective. To evaluate prescription opioid use after lumbar fusion for degenerative disc disease in a workers’ compensation (WC) setting. Summary of Background Data. Use of opioids for treating chronic low back pain has increased greatly. Few studies have evaluated risk factors for chronic opioid therapy (COT) among the clinically-distinct WC population. Methods. We used ‘‘Current Procedural Terminology’’ and ‘‘International Classification of Diseases, Ninth Revision’’ codes to identify 1002 Ohio WC subjects who underwent lumbar fusion for degenerative disc disease from 1993 to 2013. Postoperative COT was defined as being supplied with opioid analgesics for greater than 1 year after the 6-week acute period after fusion. 575 subjects fit these criteria, forming the COT group. The remaining 427 subjects formed a temporary opioid group. To identify prognostic factors associated with COT after fusion, we used a multivariate logistic regression analysis. Results. Returning to work was negatively associated with COT (P < 0.001; odds ratio [OR] 0.38). COT before fusion (P < 0.001; OR 6.15), failed back syndrome (P < 0.001; OR 3.40), additional surgery (P < 0.001; OR 2.84), clinically diagnosed depression (P < 0.001; OR 2.34), and extended work loss before fusion
From the University Hospitals Case Medical Center Department of Orthopaedics, Case Western Reserve University School of Medicine, Cleveland, OH; yOhio Bureau of Workers’ Compensation, Columbus, OH; and zNew Hampshire NeuroSpine Institute, Bedford, NH. Acknowledgment date: March 11, 2015. First revision date: May 20, 2015. Acceptance date: July 6, 2015. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. Relevant financial activities outside the submitted work: consultancy, expert testimony, payment for lectures, patents, royalties, stocks, grants, travel/ accommodations/meeting expenses. Address correspondence and reprint requests to Joshua T. Anderson, BS, University Hospitals Case Medical Center Department of Orthopaedics, Case Western Reserve University School of Medicine, 11100 Euclid Avenue, Cleveland, OH 44106; E-mail: [email protected] DOI: 10.1097/BRS.0000000000001054 Spine
(P ¼ 0.038; OR 1.61) were positively associated with COT. The rates of postoperative COT associated with these factors were 27.8%, 79.6%, 85.0%, 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 COT. Within 3 years after fusion, the COT group was supplied with an average of 1083.4 days of opioids and 49.0 opioid prescriptions, 86.2% of which were Schedule II. The COT group had an 11.0% return to work rate, $27,952 higher medical costs per subject, 43.5% rate of psychiatric comorbidity, 16.7% rate of failed back syndrome, and 27.7% rate of additional lumbar surgery. Conclusion. The majority of the study population was on COT after fusion. COT was associated with considerably worse outcomes. The poor outcomes of this study could suggest a more limited role for discogenic fusion among WC patients. Key words: workers’ compensation, lumbar fusion, lumbar arthrodesis, degenerative disc disease, discogenic low back pain, chronic low back pain, opioid use, narcotic use, clinical outcomes, chronic opioid therapy, opioid dependence, return to work, prognostic factors, predictors, work loss. Level of Evidence: 3 Spine 2015;40:1775-1784
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se of opioid analgesics for the treatment of noncancer pain has increased substantially during the past decade.1,2 This is especially true for Schedule II opioids for chronic low back pain (LBP). It is a growing public health concern that has been associated with high rates of substance abuse disorders, narcotic-related hospital admissions, and overdose deaths.1,3–6 Chronic, high-dose opioids may also lead to abnormal pain sensitivity, that is,. opioid-induced hyperalgesia.4 A recently updated Cochrane review by Chaparro et al reported that some support exists for the effectiveness of opioids for LBP in the short term, that the literature generally does not support opioids as being more effective than other groups of analgesics for chronic LBP, and that no information exists from randomized controlled trials (RCTs) supporting the efficacy and safety of opioids if used for more than 4 months.7 www.spinejournal.com
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Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
OCCUPATIONAL HEALTH/ERGONOMICS Their review consisted of 15 RCTs published between 2000 and 2012, totaling 5540 participants, with the longest trial lasting 15 weeks.8 For primary outcome measures, included RCTs must have reported: pain intensity, function, global improvement, and/or proportion of patients reporting 30% or 50% pain relief. Compared with placebo, there is low-to-moderate-quality evidence that tramadol and strong opioids improve both pain and functional outcomes. They also reported very low-quality evidence that transdermal buprenorphine is better than placebo at improving pain and functional outcomes. Compared with other drugs, the review reported very low-quality evidence that tramadol is better than celecoxib in reducing pain and very lowquality evidence that nortriptyline or flupirtine has no difference in pain outcomes or functional status compared with opioids. Their study is consistent with another recent review by Kuijpers et al.9 However, both reviews highlighted the need for higher quality RCTs and more RCTs to better assess long-term opioid therapy for chronic LBP.7,9 Furthermore, lumbar fusion surgery for degenerative disc disease (DDD) and discogenic LBP also referred to as discogenic fusion, has been associated with variable clinical outcomes, particularly when compared with fusion for more definable instability, such as spondylolisthesis.10–18 Some RCTs have reported significant improvement in Oswestry Disability Index (ODI) after discogenic fusion, but upon pooling data in a meta-analysis, Bydon et al recently reported no significant difference compared with nonoperative therapy.18 DDD and discogenic LBP are estimated to now be the most common indications for lumbar fusion in the United States, as rates of discogenic fusion have increased approximately 220% since 1990.15,19 Workers’ compensation (WC) subjects tend to have worse lumbar fusion outcomes than the general population.14,20–27 Gum et al21 and Carreon et al23 published case-controlled studies comparing lumbar fusion outcomes at 2 years between WC patients and noncompensated controls. Gum reported significantly less improvement in ODI score (5.5 vs. 15.2) and back (0.9 vs. 2.5) and leg pain (0.9 vs. 2.2) scores in the WC group.21 Carreon reported significantly less improvement in mean ODI (4.9 vs. 13.3) and Short Form 36 Health Survey, Physical Component Summary (SF-36 PCS) scores (1.3 vs. 3.9) among WC subjects. Both studies reported significantly lower rates of substantial clinical benefit among WC patients in leg and back pain scores21 and ODI and SF-36 PCS.23 Additionally, studies of WC subjects from several states report return to work (RTW) rates ranging from 26% to 36%, reoperation rates from 22% to 27%, and high rates of chronic opioid use after fusion.14,16,24–28 The prevalence of opioid use among the entire WC population is approximately 32%.29 Receiving opioids early for acute LBP in a WC setting has been associated with higher rates of disability, surgery, and chronic opioid therapy (COT).30–32 Relatively few studies evaluate risk factors for worse lumbar fusion outcomes and opioid dependence within this clinically-distinct population.14,16,24,28,33,34 Therefore, the 1776
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objectives of our study were to evaluate opioid analgesic use within a large WC population who underwent discogenic lumbar fusion, to compare postoperative outcomes between those who ended up on COT after discogenic fusion and those who did not, and to identify predictive factors associated with postoperative chronic opioid dependence. We hypothesized that subjects requiring chronic opioid analgesia after fusion will also be associated with worse clinical outcomes.
MATERIALS AND METHODS This is a retrospective observational study consisting of 1002 WC subjects from the Ohio Bureau of Workers’ Compensation (BWC) who underwent lumbar fusion for DDD and discogenic LBP. We initially used ‘‘International Classification of Diseases, Ninth Revision’’ (ICD-9) codes to identify 14,640 subjects from the Ohio BWC’s administrative database who were diagnosed with lumbar disorders after workplace injury from 1993 to 2013. We next used ‘‘Current Procedural Terminology’’ codes and a previously published coding schema to identify subjects with lumbar fusion and characterize each surgery.14,28 We centered our study and all outcome measures around each subject’s index fusion surgery after workplace injury, because subjects may have undergone multiple fusion surgeries while receiving WC. Next, we excluded 13,638 subjects from the initial 14,640 identified who did not undergo lumbar fusion, underwent fusion for an indication other than DDD and discogenic LBP, underwent a fusion approach different than anterior, posterior, or 3608, or had fewer than 3 years of follow-up after fusion. We included subjects who only underwent these fusion approaches to help eliminate heterogeneity within the population. We also excluded those with prior lumbar surgery while on WC, a smoking history, or failed back syndrome, because these factors have been reported to negatively influence fusion outcomes.13,24,35–38 We identified lumbar comorbidities and failed back syndrome using ICD-9 codes, smoking history with ICD-9 codes and use of prescription smoking deterrents, and prior lumbar surgery using Current Procedural Terminology codes. See Table 1 for the coding used to identify our study population. 1002 subjects fit our study design, and thus comprised the final discogenic fusion cohort. The primary outcome of this study was if subjects required COT after fusion. Specifically, we defined postoperative COT as being supplied opioid analgesics for more than 1 year after the immediate 6-week postoperative period. Using prescription opioid data and the number of days each prescription was written for, we identified 575 subjects on postoperative COT, thus forming the COT group. The remaining 427 subjects formed the temporary opioid therapy (TOT) group. See Figure 1 for our subject selection flow chart. In addition to days supplied, we also determined the total morphine equivalents, average daily morphine equivalents, number of opioid prescriptions filled, and percent of prescriptions that were Schedule II opioids for all subjects, both within 1 year before index fusion and between the end of the 6-week acute November 2015
Copyright © 2015 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
OCCUPATIONAL HEALTH/ERGONOMICS TABLE 1. Coding Used for Study Population Fusion Technique
CPT Code
Posterior lumbar fusion (PLF) Single level 22612 Multilevel 22612 þ 22614 Posterior lumbar interbody fusion (PLIF) Single level 22630 or 22633 Multilevel 22630 or 22633 þ 22632 or 22634 Anterior lumbar interbody fusion (ALIF) Single level 22558 Multilevel 22558 þ 22585 Lumbar Comorbidity ICD-9 Code Degenerative disc disease 722.52, 722.73, or 722.93 Disc herniation 722.10 Spondylosis 721.3 Lumbar sprain 847.2 Radiculopathy 724.4 or 729.2 CPT indicates Current Procedural Terminology; ICD-9, International Classification of Diseases, Ninth Revision.
postoperative period and 3 years after index fusion. We defined preoperative COT as being supplied with more than 120 days of opioid analgesics within the 1-year period before fusion. Furthermore, we obtained data on each subject’s age at fusion, sex, preoperative time out of work, use of physical therapy, chiropractic care, psychotherapy, and approximated income. Exact income values were unavailable to us, so we correlated each subject’s zip code of residence to a mean per capita income value based upon the 2010 US Census. We determined preoperative rates of lumbar discography, legal representation, obesity, being older than 50 at fusion, being out of work greater than 12 weeks, and psychiatric and lumbar comorbidities. Additionally, we measured a number of secondary outcomes within 3 years
Chronic Opioid Therapy and Workers’ Compensation Anderson et al
after fusion. These included: RTW status, total days out of work, medical costs paid by the Ohio BWC, new onset psychiatric disorder(s), psychotherapy use, and rates of failed back syndrome, pseudoarthrosis, permanent partial and total disability benefit payments, all-cause mortality, and additional lumbar surgery. To identify prognostic factors associated with postoperative COT, we used a multivariate logistic regression analysis. The dependent variable was whether or not subjects were on COT after fusion. With our analysis, we adjusted for a number of important covariates, all at once. We did not use a stepwise regression model. We adjusted for the following binary variables: RTW status after fusion, if a subject was diagnosed with failed back syndrome after fusion, if a subject underwent additional lumbar surgeries after fusion, if subjects were out of work more than 12 weeks before fusion, multi versus single level fusion, concurrent decompression with fusion, if a subject was receiving permanent disability payments either before or after fusion, age more than 50 at fusion, obese, sex, per capita income above the population’s 50th percentile, if a subject underwent evaluation with discography preoperatively, presence of individual psychiatric and lumbar comorbidities, if the number of physical therapy sessions used was greater than the population’s 50th percentile, if the number of chiropractic sessions used was greater than the population’s 50th percentile, if subjects were on COT before fusion, if mean preoperative daily morphine equivalents were greater than 50, and if subjects had legal representation. We adjusted for the following categorical variables: lumbar fusion approach, instrumentation, and graft type. We compared secondary outcomes and baseline population characteristics between the COT and TOT groups using x2 tests for binary and categorical variables and t tests for continuous variables. P 0.05 was considered statistically significant. For all analyses, we used Statgraphics Centurion XVI software (Statpoint Technologies, Inc.; Warrenton, VA).
Figure 1. We used International Classification of Diseases, Ninth Revision (ICD-9) and Current Procedural Terminology (CPT) codes to identify our discogenic fusion cohort. DDD indicates degenerative disc disease; LBP, low back pain. Spine
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OCCUPATIONAL HEALTH/ERGONOMICS RESULTS Table 2 contains data on important preoperative population characteristics between the COT and TOT groups. Within the year before fusion, subjects in the COT group were supplied with opioid analgesics for 186.5 22.4 more days (P < 0.001) and filled 8.3 1.2 more opioid prescriptions (P < 0.001), which equated to 12,000.8 2176.9 additional morphine equivalents (P < 0.001) and a 7.8 7.4 morphine equivalent higher daily opioid load (P ¼ 0.038). On average, 79.9% of prescription opioids written for subjects in the COT group were Schedule II opioids, compared with 63.2% among the TOT group (P < 0.001). The COT group had a 44.3% higher rate of COT before fusion (P < 0.001) and a 10.2% higher rate of daily opioid loads greater than 50 morphine equivalents (P < 0.001). Additionally, before fusion, subjects in the COT group were out of work 190.7 76.6 more days (P < 0.001) and had a 5.9% higher rate of psychiatric disorders (P < 0.001), chiefly depression (P ¼ 0.002), a 13.3% higher rate of being out of work greater than 12 weeks (P < 0.001), 5.4% higher rate of psychotherapy use (P ¼ 0.006), 10.1% higher rate of undergoing discography (P ¼ 0.002), 7.3% lower rate of using chiropractic care (P ¼ 0.019), 6.5% higher rate of legal representation (P ¼ 0.010), and a 3.8% higher rate of spondylosis (P ¼ 0.018). Table 3 includes data pertaining to each subject’s fusion surgery. The COT and TOT groups only differed significantly in rates of different fusion approaches (P ¼ 0.049). Notably, the COT group underwent a 5.0% lower rate of posterior lumbar fusion and 5.9% higher rate of posterior lumbar fusion plus interbody fusion. Table 4 contains data on all predictive factors associated with postoperative COT from the regression model as well as postoperative opioid analgesic use associated with each variable. 57.4% (575/1002) of all subjects ended up on COT after the immediate 6-week postoperative period after fusion. The ability to RTW within 2 years of fusion was negatively associated with COT (P < 0.001; odds ratio [OR] 0.38). COT before fusion (P < 0.001; OR 6.15), failed back syndrome (P < 0.001; OR 3.40), additional surgery (P < 0.001; OR 2.84), clinically diagnosed depression, either before or after fusion (P < 0.001; OR 2.34), and prolonged time out of work before fusion (P ¼ 0.038; OR 1.61) were all positively associated with COT. The lowest rate of COT was seen among those who were able to RTW at 27.8%, with the highest seen among those with failed back syndrome at 85.0%. The strongest predictor of postoperative COT was preoperative COT. Subjects with positive factors were on opioid analgesics not only longer, but also with higher daily opioid loads and higher rates of Schedule II opioids. If subjects associated with any positive factor were removed, the COT rate decreases to only 10.7% (8/75). However, 92.5% of subjects had 1 or more positive factors. Figure 2 demonstrates the rates of postoperative COT associated with each predictive factor and rates of COT if subjects associated with each factor were removed. 1778
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Chronic Opioid Therapy and Workers’ Compensation Anderson et al
Figure 3 and Figure 4 illustrate the impact preoperative duration of opioid use and preoperative net opioid load had on rates of postoperative COT. After receiving more than 60 days of opioids, subjects were associated with increasingly higher rates of postoperative COT (P < 0.001). 87.1% of subjects who received more than 240 days of opioids within the year before fusion ended up on COT postoperatively and were 16.01 times more likely to end up on postoperative COT than those who received fewer than 7 days of opioids preoperatively. Similarly, as total preoperative opioid load increased above 5000, so did postoperative rates of COT. 90.4% of subjects supplied with more than 25,000 morphine equivalents before fusion ended up on COT after fusion. Subjects receiving more than 25,000 morphine equivalents through opioid prescriptions before fusion were also 15.69 times more likely to end up on COT after fusion compared with subjects who received fewer than 5000 morphine equivalents before fusion. Table 5 includes data on all outcome measures and compares them between the COT and TOT groups. Not surprisingly, those who ended up on COT after fusion experienced considerably worse outcomes after fusion. Regarding opioid analgesia from 6 weeks to 3 years after fusion, subjects on COT were, on average, supplied with 985.1 50.8 additional days of opioids (P < 0.001) and filled 41.4 2.4 more opioid prescriptions (P < 0.001), which equated to 78,043.0 8879.5 additional morphine equivalents (P < 0.001) with a 24.4 7.5 morphine equivalent higher daily opioid load (P < 0.001). On average, 86.2% of prescription opioids written for subjects in the COT group after fusion were Schedule II, compared with 69.9% in the TOT group (P < 0.001). Compared with the rates before fusion, these rates increased 6.3% and 6.7% after fusion among the COT and TOT groups, respectively. Daily opioid loads and rates of Schedule II opioids increased after fusion between both groups. However, this increase was much more pronounced in the COT group, especially daily opioid load. Within 3 years after fusion, the COT group was also out of work 197.4 37.3 additional days (P < 0.001), cost the Ohio BWC $27,962.5 $4624.4 more per subject (P < 0.001), and had a 27.4% lower RTW rate (P < 0.001), 20.0% higher rate of new onset psychiatric disorder(s) (P < 0.001), 12.7% higher rate of failed back syndrome (P < 0.001), 7.4% higher rate of total permanent disability payments (P ¼ 0.002), and a 16.2% higher rate of additional lumbar surgery after fusion (P < 0.001). Postoperative rates of psychotherapy use increased 26.4% (P < 0.001) and 11.0% (P < 0.001) compared with those before fusion in the COT and TOT groups, respectively. The COT (P < 0.001) and TOT (P ¼ 0.023) groups used 7.1 2.5 and 2.3 2.0 more psychotherapy sessions after fusion compared with before. Also, the COT group underwent a 24.8% higher rate of first-time psychological diagnostic examination after fusion than before (P < 0.001). These data suggest worsening psychiatric health after fusion as well as a potential impact for better screening and treatment of psychiatric disease before performing lumbar fusion among WC patients. November 2015
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OCCUPATIONAL HEALTH/ERGONOMICS
Chronic Opioid Therapy and Workers’ Compensation Anderson et al
TABLE 2. Preoperative Population Characteristics Characteristic
COT Group
TOT Group
No. of subjects Age at index fusion, mean SD Subjects over 50 at index fusion, no. (%) Sex Male, no. (%) Female, no. (%) Days out of work BIF, mean SD Subjects out of work >12 wk, no. (%) Psychiatric history, no. (%) Depression, no. (%) Anxiety, no. (%) Adjustment reaction, no. (%) Psychological diagnostic examination, no. (%) Psychotherapy use, no. (%) Number of sessions, mean SD Permanent disability benefits, no. (%) Permanent partial, no. (%) Permanent total, no. (%) Lumbar discography, no. (%) Physical therapy, no. (%) Mean number of sessions, mean SD Chiropractic care, no. (%) Mean number of sessions, mean SD Legal representation, no. (%) Opioid analgesic use within 1 yr BIF Days suppliedy, mean SD Subjects supplied for >120 d, no. (%) Net MEQs supplied, mean SD Mean daily MEQs, mean SD >50 MEQs per day, no. (%) No. of prescriptions filled, mean SD Avg.% of Rx Schedule IIz, mean SD Lumbar comorbidity Disc herniation, no. (%) Radiculopathy, no. (%) Spondylosis, no. (%) Lumbar sprain, no. (%)
575 44.5 8.4 132 (23.0%)
427 44.4 8.9 117 (27.4%)
383 (66.6%) 192 (33.4%) 672.1 640.1 517 (89.9%) 72 (12.5%) 65 (11.3%) 8 (1.4%) 6 (1.0%) 74 (12.9%)
279 (65.3%) 148 (34.7%) 481.4 568.2 327 (76.6%) 28 (6.6%) 24 (5.6%) 1 (0.2%) 4 (0.9%) 39 (9.1%)
