Abstract
Background.
There is limited research on the long-term effectiveness of epidural steroid injections (ESI) in older adults despite the high prevalence of back and leg pain in this age group. We tested the hypotheses that older adults undergoing ESI, compared to patients not receiving ESI: 1) have worse pain, disability and quality of life (“outcomes”) pre-ESI, 2) have improved outcomes after ESI, and 3) have improved outcomes due to a specific ESI effect.
Methods.
We prospectively studied patients ≥65 years old presenting to primary care with new episodes of back pain in three US healthcare systems (BOLD registry). Outcomes were leg and back pain intensity, disability and quality of life, assessed at baseline and 3-, 6-, 12- and 24-month follow-ups. We categorized participants as: 1) ESI within 6 months from the index visit (n=295); 2) no ESI within 6 months (n=4,809); 3) no ESI within 6 months, propensity-score matched to group 1 (n=483). We analyzed the data using linear regression and Generalized Estimating Equations.
Results.
Pain intensity, disability and quality of life at baseline were significantly worse at baseline in ESI patients (group 1) than in group 2. The improvement from baseline to 24 months in all outcomes was statistically significant for group 1. However, no statistically significant differences were observed between outcome trajectories for the propensity-score matched groups 1 and 3.
Conclusions.
Older adults treated with ESI have long-term improvement. However, the improvement is unlikely the result of a specific ESI effect.
INTRODUCTION
Epidural steroid injections (ESI) are commonly performed to treat lumbar radicular pain, with or without back pain. Among 52,347,000 Medicare patients, nearly 2.2 million epidural injections have been performed in 2018 (Manchikanti et al., 2020). Systematic reviews and meta-analyses have shown short- to intermediate-term efficacy (Pinto et al., 2012; Chou et al., 2015; Bhatia et al., 2016; Sharma et al., 2017; Oliveira et al., 2020). Back pain prevalence increases with age, peaks at the ages of 80 to 89 years (Wu et al., 2020), and often has a substantial negative impact on function, mood and quality of life in older adults (Docking et al., 2011). However, most clinical trials and systematic reviews of ESI have not focused on older patient populations.
The Back pain Outcomes using Longitudinal Data (BOLD) project was designed to describe the natural history of back pain among older adults and prospectively evaluate interventions for patients 65 and older with new episodes of care for back pain, defined as having no visit for back pain in the prior six months (Jarvik et al., 2012). Considering the globally aging of the population, the high prevalence of pain in older adults with substantial impact on their quality of life, and the high use of ESI, there is a need for studying the long-term effectiveness of ESI specifically in older adults.
In the current study, we used BOLD data to examine the long-term effectiveness of ESI in a large sample of older adults with new episodes of care for back pain, with or without leg pain. We compared the 24-month trajectories of pain, disability and quality of life in older adults with a new episode of care for back pain treated with versus without ESI in the first 6 months of the enrolment visit. We tested the hypotheses that: 1) patients with ESI would have worse pain, disability and quality of life at baseline compared with patients who did not have ESI within the same time period after the enrolment visit, 2) patients undergoing ESI would have improved pain, disability and quality of life over 24 months compared with patients without ESI in the same time periods, and 3) improvement in pain, disability and quality of life would be due to a specific ESI effect.
METHODS
The methodology of establishing the BOLD back pain registry and the methods of data collection is described in detail in the study protocol (Jarvik et al., 2012).
Participants and setting
We recruited patients from three integrated health care systems: Kaiser Permanente Northern California (KPNC), Henry Ford Health System (HFHS), and Harvard Vanguard Medical Associates (HVMA Boston). The Comparative Effectiveness, Cost and Outcomes Research Center (CECORC) and the Center for Biomedical Statistics (CBS) at the University of Washington (UW) served as the Data Coordinating Center (DCC).
The Institutional review Boards (IRBs) at all participating institutions (UW, KPNC, HFHS and HVMA Boston) reviewed and approved the study. The procedures followed were in accordance with the Helsinki Declaration of 1975, as revised in 1983. Informed consent was obtained from all patients, who were offered a $10 gift card or check for each completed interview (baseline and 3-, 6-, 12- and 24-month follow-ups).
Patients were identified at primary care clinics, urgent care clinics, and emergency care settings. Patients ≥65 years old with visits in the previous 3 weeks associated with an International Classification of Diseases (ICD-9) diagnosis code indicating back pain, with or without leg pain, were considered for enrollment (see study protocol for the list of codes (Jarvik et al., 2012)). The research staff contacted potential participants by either telephone, email, mail or in person, and informed them about the study using a standardized script. Exclusion criteria were having health care encounters for back pain within the previous six months, previous contact for registry participation, prior lumbar spine surgery, developmental spine deformity, inflammatory spondyloarthropathy, spinal malignancy or infection, history of cancer within past five years excluding non-melanomatous skin cancer, history of human immunodeficiency virus (HIV) within the past five years, unavailability of telephone, planning on leaving the Health System within the next 12 months, inability to understand English, and severe mental impairment that would interfere with answering questions.
From 2010 to 2013, 5,239 patients were enrolled. For this analysis, we excluded those with a procedure other than ESI during the first 6 months (n = 51) and without electronic health record data available (n = 84). We refer to the first enrolment visit as the “index visit,” which occurred either in person or by phone. The index visit was a dedicated research visit and separate from the clinical encounter. We categorized participants into three groups for the purposes of the present study: 1) patients who received ESI within six months from the index visit (n=295); 2) all patients with no ESI, lumbar surgery, other injection, or radiofrequency ablation within six months (n = 4,809); 3) a subset of group two with no ESI or lumbar procedure within six months, propensity-score matched to the ESI group for baseline sociodemographic characteristics, recruitment site, pain, function, psychological characteristics, quality of life, smoking status, and Quan Comorbidity Score (n=483). Receipt of ESI and other procedures was determined using CPT codes from electronic health record data.
Routes of ESI were transforaminal (needle placed in the epidural space through an intervertebral foramen) (Bhatia et al., 2016) or interlaminar (needle placed in the epidural space through the space between the laminae of two adjacent vertebrae) (Ghai et al., 2013).
Measures
Methods of data collection
Diagnosis (ICD-9) codes in the prior 12 months, receipt of ≥1 opioid prescription in the 12 months before the index visit, route of ESI (interlaminar or transforaminal) and Quan Comorbidity Score were derived from the electronic health records (EHR). All other variables were assessed by mailed questionnaires or phone interviews, based on patient preference.
Baseline measures
Baseline measures were recorded within three weeks of the index vist. Sociodemographic characteristics included: age, sex, ethnicity, race, marital status, and education.
Measure in the domains of pain were duration of pain, intensity of leg and back pain, ICD-9 back pain diagnosis codes in the prior 12 months, and opioid prescriptions filled in the 12 months before the index visit. Patients were asked to indicate the duration of back or leg pain (sciatica) as less than one month, 1–3 months, 3–6 months, 6–12 months, 1–5 years and more than five years. Using a Numerical Rating Scale (NRS) (Dworkin et al., 2005), we asked patients to rate separately their average leg and back pain within the past seven days, with 0 = no pain and 10 = worst pain imaginable.
We assessed back-related disability using the Roland-Morris Disability Questionnaire (RMDQ) (Roland and Morris, 1983). We had previously modified the questionnaire to add “or leg (sciatica)” to the words “back pain” in the items (Jarvik et al., 2012).
Depression and anxiety were assessed separately using the Patient Health Questionnaire-4 Depression and Anxiety Screen (PHQ-4) (Kroenke et al., 2003). Expectation for recovery was evaluated by asking patients to use a 0–10 scale to rate their confidence that their pain would be completely resolved or much better in 3 months (0 = no confidence in recovery; 10 = complete confidence in recovery).
We evaluated quality of life using the EuroQol-5D (EQ-5D) (Nemeth, 2006), which consists of five dimensions (mobility, self-care, usual activities, pain/discomfort, and anxiety/depression). Other health characteristics included smoking status and Quan Comorbidity Score, computed using ICD-9 codes over the 12 months prior to the index visit.
Outcomes
The outcomes to compare patients who had ESI to those who did not were intensity of leg and back pain, RMDQ and EQ-5D as described under “Baseline measures.” The outcomes were assessed at baseline, and three, six, 12 and 24 months after baseline.
Statistical analysis
Descriptive statistics were used to summarize the baseline characteristics of patients who received ESI and all other patients who did not receive ESI or other lumbar procedures within 6 months after the index visit. To test the hypothesis that patients with ESI would have worse pain, disability and quality of life at baseline compared with patients who did not have ESI within the same time period after the index visit, mean baseline scores of the two groups were compared using linear regression. These estimates were adjusted for age, sex, race, education, marital status, recruitment site, and back pain duration.
To test the hypothesis that patients undergoing ESI would have improved pain, disability and quality of life over 24 months compared with patients without ESI in the same time periods, we estimated longitudinal outcomes of those with an ESI within the first 6 months versus the non-ESI, unmatched group using Generalized Estimating Equations (GEE) with a Gaussian distribution and unstructured correlation structure. This descriptive analysis compares unadjusted trajectories of each group, so all timepoints (baseline, 3, 6, 12 and 24 months) were included and an interaction for ESI/time was also included to model differences in change over time.
To test the hypothesis that improvement in pain, disability and quality of life would be due to a specific ESI effect, we compared the ESI group with the propensity score-matched no-ESI group with a two-step process. First, we created the propensity score. We used a logistic regression model containing all baseline variables specified above for predicting use of any ESI within 6 months. We then matched up to two controls to every case based on propensity score within a caliper of 0.1. Adequacy of the matching process was assessed by inspecting the distributions of the propensity scores for each group, standardized percentage bias, and common support (Austin, 2011). Baseline characteristics of the matched groups were compared using t-tests or Chi-square tests, as appropriate. Second, we compared post-treatment outcomes (6, 12, and 24 months) using GEE models with a Gaussian distribution and unstructured correlation structure. Additional covariates in the GEE model with these matched groups included time of post-treatment outcomes (baseline and 3 month timepoints were not included since ESI was ascertained from 0-6 months), an ESI-time interaction term, age, sex, race, Hispanic ethnicity, education, Quan Comorbidity Score, index diagnosis, recruitment site, any prior opioid prescription, and baseline scores for: leg pain NRS, back pain NRS, back/leg pain duration, RMQD, EQ-5D, positive anxiety screen, positive depression screen, and expectation for recovery.
Statistical analyses were performed using Stata IC 16.1 (College Station, TX), USA. P<0.05 with a two-tailed test was considered as statistically significant.
RESULTS
Baseline characteristics of patients treated with and without ESI
The baseline characteristics and data completeness for patients who did vs did not undergo ESI within six months after the index visit are shown in Table 1. Of the 295 patients in the ESI group, 158 (53.6%) underwent only interlaminar injections, 115 (39.0%) only transforaminal injections, and 22 (7.5%) both within the first six months. Most patients receiving ESI had their first injection within 3 months (n=217, 74%), while 78 (26%) did not receive their first injection until between 3 and 6 months.
Table 1.
Baseline characteristics of patients who received epidural steroid injections (ESI) and patients who did not receive ESI or other lumbar procedure within 6 months after a first episode of low back pain.
| ESI (N = 295) | No procedure (N = 4,809) | |||
|---|---|---|---|---|
|
| ||||
| Mean or N | SD or % | Mean or N | SD or % | |
| Sociodemographic characteristics | ||||
| Age (years) (mean and SD) | 74.1 | 6.8 | 73.8 | 6.9 |
| Sex (N and % Female) | 188 | 63.7 | 3221 | 64.9 |
| Ethnicity: Hispanic (N and %) | 14 | 4.8 | 288 | 6.0 |
| Race (N and %) | ||||
| Black | 43 | 14.6 | 735 | 15.3 |
| White | 220 | 74.6 | 3,516 | 73.1 |
| Asian | 10 | 3.4 | 183 | 3.8 |
| Other | 18 | 6.1 | 322 | 6.7 |
| No answer / missing | 4.0 | 1 | 53 | 1.1 |
| Education (N and %) | ||||
| High school or less | 91 | 30.1 | 1,444 | 30.0 |
| Less than 4 years of college | 94 | 31.9 | 1,349 | 28.1 |
| At least college graduate | 110 | 37.3 | 2,001 | 41.6 |
| No answer / missing | 0 | 0.0 | 15 | 0.3 |
| Marital Status | ||||
| Married or lives with partner | 2912 | 60.6 | 177 | 60.0 |
| Separated or divorced | 800 | 16.6 | 46 | 15.6 |
| Widowed | 15 | 0.3 | 0 | 0.0 |
| No answer/missing | ||||
|
| ||||
| Pain and Function | ||||
| Pain duration (N and %) | ||||
| < 1 Month | 85 | 28.8 | 1,626 | 33.8 |
| 1-3 Months | 69 | 23.4 | 922 | 19.2 |
| 3-6 Months | 26 | 8.8 | 310 | 6.5 |
| 6-12 Months | 21 | 7.1 | 282 | 5.9 |
| 1-5 Years | 49 | 16.6 | 708 | 14.7 |
| 5+ Years | 45 | 15.3 | 958 | 19.9 |
| No answer / missing | 0 | 0.0 | 3 | 0.1 |
| Back pain intensity (NRS) (mean and SD) | 6.1 | 2.8 | 5.0 | 2.8 |
| Leg pain present (N and %) | 256 | 86.8 | 2962 | 61.6 |
| Leg pain intensity (NRS) (mean and SD) | 5.8 | 3.2 | 3.3 | 3.3 |
| Opioid prescription prior 12-months (N and %) | 63 | 21.4 | 649 | 13.5 |
| Index diagnosis code (N and %) | ||||
| Axial pain | 103 | 34.9 | 2,312 | 48.1 |
| Back and leg pain | 118 | 40.0 | 777 | 16.2 |
| Lumbar spinal stenosis | 22 | 7.5 | 89 | 1.9 |
| Compression fracture | 0 | 0 | 8 | 0.2 |
| Other | 52 | 17.6 | 1,623 | 33.8 |
| Functional status (RMDQ) (mean and SD) | 13.0 | 5.7 | 9.3 | 6.4 |
|
| ||||
| Psychological characteristics and Quality of life | ||||
| Expectation for recovery (mean and SD) | 5.8 | 3.5 | 5.4 | 3.7 |
| Positive depression screen (N and %) | 38 | 12.9 | 388 | 8.1 |
| Positive anxiety screen (N and %) | 51 | 17.3 | 580 | 12.1 |
| EQ5D (mean and SD) | 0.66 | 0.20 | 0.76 | 0.17 |
|
| ||||
| General health | ||||
| Current smoker (N and %) | 20 | 6.8 | 291 | 6.1 |
| Quan Comorbidity Score (median, interquartile range) | ||||
| 0 | 173 | 58.6 | 2,873 | 59.7 |
| 1 | 66 | 22.4 | 796 | 16.6 |
| 2 | 25 | 8.5 | 413 | 8.6 |
| 3+ | 30 | 10.2 | 602 | 12.5 |
| NA | 1 | 0.3 | 125 | 2.6 |
EQ5D: EuroQol-5D. N: number of patients. NRS: Numerical rating score (0 = no pain, 10 = worst pain imaginable). SD: standard deviation. RMDQ: Roland-Morris Disability Questionnaire.
Thirty-seven patients in the no ESI group have missing opioid data
Patients with ESI during 6 months after index visit had worse pain, disability and quality of life at baseline compared with patients who did not have ESI within the same time period (Table 2).
Table 2.
Adjusted* difference in mean baseline outcome scores for those who received epidural steroid injections (ESI) and patients who did not receive ESI or other lumbar procedure within 6 months after a first episode of low back pain.
| Outcome | β | 95% Confidence Interval | P-value | |
|---|---|---|---|---|
| Leg pain intensity (NRS) | 2.4 | 2.0 | 2.8 | <0.001 |
| Back pain intensity (NRS) | 1.1 | 0.8 | 1.5 | <0.001 |
| Functional Status (RMDQ) | 3.4 | 2.7 | 4.0 | <0.001 |
| EQ-5D | −0.091 | −0.115 | −0.068 | <0.001 |
Adjusted for age, sex, race, education, marital status, site, and back pain duration.
NRS: Numerical rating score (0 = no pain, 10 = worst pain imaginable). RMDQ: Roland-Morris Disability Questionnaire. EQ5D: EuroQol-5D (0-100 scale).
Trajectories of patients treated with and without ESI (unmatched)
The unadjusted trajectories of leg and back pain intensity, RMDQ and EQ-5D in patients treated with and without ESI (unmatched) are presented in Supplementary Table 1 and illustrated in Fig. 1. For all outcomes, there were statistically significant differences between groups and significant improvement over time. For example, leg pain changed from 5.8 (95% CI: 5.4, 6.1) at baseline to 3.6 (95% CI: 3.2, 4.0) at 12-months among those with an ESI, while it changed from 3.3 (95% CI: 3.2, 3.4) to 2.9 (95% CI: 2.8, 3.0) for those without an ESI. For the EQ-5D, the treatment by time interaction was non-significant (p =0.0647).
Figure 1.
Trajectories of pain, disability and quality of life over 24 months in patients who received ESI (n = 295) and all other unmatched patients who did not receive ESI or lumbar procedures (n = 4,809). Error bars are 95% confidence intervals. ESI within first 6 months (yes/no) was the predictor; time (baseline, 3, 6, 12 and 24 months) and the interaction ESI/time were covariates.
Leg pain: difference between groups, p<0.0001; change over time, p<0.0001; treatment by time interaction, p<0.0001. Back pain: difference between groups, p<0.0001; change over time, p<0.0001; treatment by time interaction, p=0.0081. Disability: difference between groups, p<0.0001; change over time, p<0.0001; treatment by time interaction, p=0.0007. Quality of life: difference between groups, p<0.0001; change over time, p<0.0001; treatment by time interaction, p=0.0647.
Trajectories of patients treated with and without ESI (matched)
Table 3 presents the baseline characteristics of patients who received ESI and of propensity score-matched patients who did not receive ESI or other lumbar procedures within six months after the index visit. There was no statistically significant difference between the groups at baseline.
Table 3.
Baseline characteristics of patients who received ESI (n = 285) and propensity score matched patients who did not receive ESI or lumbar procedures (n = 483). Of the 295 ESI patients, 10 could not be matched.
| ESI (N = 285) | No procedure (N = 483) | P value | |||
|---|---|---|---|---|---|
|
| |||||
| Mean or N | SD or % | Mean or N | SD or % | ||
| Sociodemographic characteristics | |||||
| Age (years) (mean and SD) | 74.1 | 6.9 | 74.5 | 7.2 | 0.53 |
| Sex (N and % Female) | 181 | 63.51 | 288 | 59.63 | 0.29 |
| Ethnicity (N and % Hispanic) | 14 | 4.91 | 25 | 5.18 | 0.87 |
| Race (N and %) | 0.66 | ||||
| Black | 216 | 75.8 | 346 | 71.6 | |
| White | 43 | 15.1 | 85 | 17.6 | |
| Asian | 9 | 3.2 | 19 | 3.9 | |
| Other | 17 | 6.0 | 33 | 6.8 | |
| Education (N and %) | 0.97 | ||||
| High school or less | 88 | 30.9 | 149 | 30.9 | |
| Less than 4 years of college | 92 | 32.3 | 152 | 31.5 | |
| At least four-year college graduate | 105 | 36.8 | 182 | 37.7 | |
|
| |||||
| Pain and Function | |||||
| Pain duration (N and %) | 0.96 | ||||
| < 1 Month | 79 | 27.7 | 131 | 27.1 | |
| 1-3 Months | 67 | 23.5 | 119 | 24.6 | |
| 3-6 Months | 26 | 9.1 | 51 | 10.6 | |
| 6-12 Months | 20 | 7.0 | 37 | 7.7 | |
| 1-5 Years | 48 | 16.8 | 78 | 16.2 | |
| 5+ Years | 45 | 15.8 | 67 | 13.9 | |
| Back pain intensity (NRS) (mean and SD) | 6.1 | 2.9 | 5.9 | 2.6 | 0.36 |
| Leg pain present (N and %) | 248 | 87.0 | 408 | 84.5 | 0.33 |
| Leg pain intensity (NRS) (mean and SD) | 5.8 | 3.2 | 5.6 | 3.2 | 0.28 |
| Opioid prescription prior 12-months (N and %) | 61 | 21.4 | 99 | 20.5 | 0.77 |
| Index diagnosis code (N and %) | 0.46 | ||||
| Axial pain | 97 | 34.0 | 186 | 38.5 | |
| Back and leg pain | 114 | 40.0 | 177 | 36.7 | |
| Lumbar spinal stenosis | 22 | 7.7 | 28 | 5.8 | |
| Other | 52 | 18.3 | 92 | 19.1 | |
| Functional status (RMDQ) (mean and SD) | 12.9 | 5.7 | 12.5 | 5.7 | 0.43 |
|
| |||||
| Psychological characteristics and Quality of life | |||||
| Expectation for recovery (mean and SD) | 5.8 | 3.5 | 5.8 | 3.5 | 0.76 |
| Positive depression screen (N and %) | 36 | 12.6 | 54 | 11.2 | 0.55 |
| Positive anxiety screen (N and %) | 47 | 16.5 | 79 | 16.4 | 0.96 |
| EQ5D (mean and SD) | 0.67 | 0.19 | 0.69 | 0.19 | 0.17 |
|
| |||||
| General health | |||||
| Smoking status (N and %) | 0.58 | ||||
| Smoker or quit < 1 year ago | 19 | 6.7 | 34 | 7.0 | |
| Opioid Prescription prior 12-months (N and %) | 61 | 21.4 | 99 | 20.5 | 0.77 |
| Quan Comorbidity Score (N and %) | 0.35 | ||||
| 0 | 166 | 58.3 | 293 | 60.7 | |
| 1 | 66 | 23.2 | 88 | 18.2 | |
| 2 | 23 | 8.07 | 39 | 8.1 | |
| 3 or more | 30 | 10.5 | 63 | 13.0 | |
EQ5D: EuroQol-5D. N: number of patients. NRS: Numerical rating score (0 = no pain, 10 = worst pain imaginable). SD: standard deviation. RMDQ: Roland-Morris Disability Questionnaire.
The post-treatment trajectories of leg and back pain intensity, RMDQ and EQ-5D in the two groups are presented in the Supplementary Table 2 and illustrated in Fig. 2. For all of the 4 outcomes, no statistically significant difference between the ESI and the non-ESI propensity-score matched group, and no treatment by time interaction, were observed.
Figure 2.
Trajectories of pain, disability and quality of life over 24 months in patients who received ESI (n = 285) and propensity score matched patients who did not receive ESI or lumbar procedures (n = 483). Of the 295 ESI patients, 10 could not be matched. Error bars are 95% confidence intervals. To create the propensity score we used a model containing variables in the domains of sociodemographic characteristics, pain, function, psychosocial characteristics, quality of life, and health-related factors. Covariates in the Generalized Estimating Equations model include assessment time (6, 12 and 24 months), interaction ESI-time, recruitment site, and variables in the domains of sociodemographic characteristics, pain, function, psychosocial characteristics, quality of life, and health-related factors.
Leg pain: difference between groups, p=0.267; treatment by time interaction, p=0.387. Back pain: difference between groups, p=0.612; treatment by time interaction, p=0.212. Disability: difference between groups, p=0.557; treatment by time interaction, p=0.151. Quality of life: difference between groups, p=0.184; treatment by time interaction, p=0.917.
DISCUSSION AND CONLUSIONS
Main findings
Pain, disability and quality of life at baseline were substantially worse in patients who were treated with ESI in the first six months after an initial visit in a new episode of care for back pain than in patients not receiving ESI. Trajectories of leg pain, back pain and disability decreased over 24 months more in patients treated with ESI than in non-ESI patients. However, the propensity-score matched analysis revealed that patients with similar baseline characteristics have similar outcomes regardless of whether ESI was provided, indicating that the improvement in the clinical course of patients treated with ESI is unlikely the result of a specific effect of the treatment.
Baseline characteristics of patients treated with and without ESI
Patients with ESI during 6 months after index visit had worse pain, disability and quality of life at baseline compared with patients who did not have ESI within the same time period (Table 2). These differences may reflect the preference of clinicians to offer an invasive treatment to patients with high levels of pain, poor functional status, and poor quality of life, while treating patients in a less severe condition with non-invasive therapies.
The BOLD study included patients with back pain, with or without leg pain. This explains why most patients who received an ESI had an index diagnosis of axial pain or a combination of back and leg pain (Table 1). On average, back pain seems to be as relevant as leg pain in this cohort, as documented by the pain intensity. While ESI is recommended for the treatment of radicular pain (Chou et al., 2007; NICE, 2016), 13.2% of patients receiving an ESI did not have leg pain (Table 1). The rationale for performing ESI in the absence of leg pain is unclear.
Trajectories in patients treated with and without ESI
The trajectories of pain, disability and quality of life improved over 24 months in both patients who received ESI and patients who did not receive ESI or lumbar procedures (Supplementary Supplementary Table 1 and Fig. 1). The ESI group had worse scores on the outcome measures at baseline, but their improvement was more marked and the difference from the non-ESI group decreased over time. However, the two trajectories did not overlap for any outcome, indicating that the ESI group represents a more challenging patient population with a less-favorable prognosis.
When the ESI group was propensity-score matched to a group of patients according to baseline characteristics, no difference in the trajectories of outcomes was observed (Fig. 2). This indicates that while the group of patients undergoing ESI improved over 24 months (Fig. 1), the improvement was unlikely the result of a specific effect of the ESI. Natural history, regression to the mean and placebo effects are possible explanations for the improvement. Both patients treated with and without ESI may have improved thanks to a favorable course of the condition, rather than because of the treatments received (van der Gaag et al., 2019). They may have sought medical care when most syptomatic, and may have then spontaneously improved independent of the treatment received (regression to the mean).
Strengths and limitations
This study addressed the need for a large prospective comparative study on ESI focusing on older adults. The recruitment at three different health care systems, primary care clinics, urgent care clinics and emergency care settings, the large sample size and the pragmatic nature of the study are strengths in terms of generalizability of the findings. The 24-month follow-up period provides unique information on the long-term effects of ESI in multiple domains, including pain, function and quality of life.
Lack of randomization and blinding limit the ability to evaluate fully the comparative effectiveness of ESI vs. non-ESI, although the propensity score matching reduces the likelihood of bias associated with lack of randomization. Our propensity-score matched approach is not a substitute for randomized controlled trials. However, to the best of our knowledge, randomized controlled trials with long-term follow-up are not available for this patient population. As the BOLD study was designed to reflect real-world clinical practice, treatments and techniques were not standardized, which may have introduced uncontrolled sources of variability. We did not obtain data on some clinical variables, such as use of soluble vs. particulate steroid, or doses administered. Although unlikely, we cannot rule out that different medications or doses would produce different results. We included in the ESI group patients who received the treatment within six months after the index visit. This was done to reflect clinical practice, whereby ESI is performed at different times for different reasons, such as prolonged trials of conservative treatments or delayed access to care. However, because of this approach we could not include the three-month follow-up in the propensity-score trajectory analysis, preventing the evaluation of the shorter-term specific effect of ESI.
Implications
Despite common use, the practice of ESI remains the subject of debate. Systematic reviews and meta-analyses have shown short- to middle-term efficacy for radicular pain (Pinto et al., 2012; Chou et al., 2015; Bhatia et al., 2016; Sharma et al., 2017; Oliveira et al., 2020). The present study showed long-term improvements after ESI, but these improvements were likely due to reasons other than the ESI treatment.
Our results and previous evidence raise questions regarding the balance of benefits and risks. Short- or middle-term benefits may be valuable in patients with high levels of pain, disability and pain-related distress. However, a recent systematic review and meta-analysis focusing on the clinical relevance of ESI effectiveness found that only 4 of 17 studies detected clinically relevant effects, and the certainty of the evidence was either low or very low (de Bruijn et al., 2021). In a large study in the Medicare population, the rate (95% CI) of serious spinal adverse events probably associated with lumbar ESI was estimated 5.1 (2.3 to 11.0) per one million (Eworuke et al., 2021). In addition to procedural complications, it is important to consider side effects that may result from systemic absorption of steroids and consequent cortisol suppression (Friedly et al., 2018).
The results of our study suggest that older adults with new episodes of care for back and leg pain are unlikely to experience long-term benefits from ESI. Health care professionals may consider informing patients that they can improve in the long term, independent of the use of ESI. The evidence base for the practice of ESI in older adults would greatly benefit from randomized controlled trials that would determine the efficacy, the comparative effectiveness, and the value of ESI as complement to multidisciplinary care.
Supplementary Material
Significance.
In this large, two-year, prospective study in older adults with a new episode of low back pain, back pain, leg pain, disability and quality of life improved after epidural steroid injections; however, propensity-score matching revealed that the improvement was unlikely the result of a specific effect of the injections, indicating that epidural steroids are unlikely to provide long-term benefits in older adults with new episodes of back and leg pain.
Funding.
Supported by the University of Washington Clinical Learning, Evidence And Research (CLEAR) Center for Musculoskeletal Research. CLEAR is supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS) of the National Institutes of Health (Award Number P30AR072572). The study was also supported by the Agency for Healthcare Research and Quality (AHRQ) (1R01HS01922201 and 1R01HS022972-01).
Footnotes
Conflict of interest: None for any author.
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