Adult spinal deformity patients with spinal cord stimulators and intrathecal drug delivery devices do not have greater chronic opioid use after surgery

Authors: Alexandra C. Dionne, Kurt Holuba, Riley Sevensky, Justin L. Reyes, Roy Miller, Fthimnir M. Hassan, Josephine R. Coury, Joseph M. Lombardi, Lawrence G. Lenke, Zeeshan M. Sardar

Abstract

Objective:

The objective of the study was to determine if adult spinal deformity (ASD) patients with spinal cord stimulators (SCS) or intrathecal drug delivery devices (IDDD) have more chronic opioid consumption or worse surgical outcomes than a matched cohort.

Methodology:

We conducted a retrospective matched comparison of implanted (SCS [n = 11] or IDDD [n = 3]) and nonimplanted ASD patients (n = 40) who underwent corrective spine surgery at a single center. We evaluated their intraoperative characteristics, long-term postoperative complications, radiographic correction, and chronic opioid use, measured as use on more than 50% of days for >6 months pre-or postoperative and total morphine mg equivalents (MME) and MME per dose.

Results:

We found no difference in the rate of chronic opioid use between the implanted and nonimplanted ASD 6 m 50% (n = 7) versus 40% (n = 16), 71% (10) versus 45% (18), 6 m 64.3% (9) versus 32.5% (13), final follow-up (FFU): 64.3% (9) versus 37.5% (15), P > 0.05. Similarly, there was no difference in total MME: 6 m 101.3 ± 177.8 versus 37.3 ± 89.4, 68.2 ± 77.8 versus 45.3 ± 129.9, 6 m 59.8 ± 83.1 versus 20.8 ± 46.9, FFU: 51.2 ± 68.7 versus 31.1 ± 55.5, P > 0.05 for all. Implanted patients had higher OR time (implanted: 734.9 [103.4] vs. 637.2 [147.8] min, P = 0.0272), intraoperative blood requirement (2.1 [1.6] µ pRBCs vs. 1.1 [1.5] µ, P = 0.0500), and rate of dural tears (42.9% (6/14) vs. 15% (6/40).

Conclusion:

This study indicates that implanted ASD patients are not at increased risk for chronic opioid use and do not have worse postoperative compilation rates than nonimplanted patients.

INTRODUCTION

It is well established that prolonged use of opioid medication can have negative physical and social effects. This risk is particularly relevant in spine surgery patients, 20%–60% of whom are on chronic opioids before surgery.[12345] Multiple studies have shown that chronic opioid use before elective spine surgery is associated with prolonged postoperative use,[356] which in turn correlates with higher reoperation rates, longer hospital and ICU stays, lower return to work rates, increased 2-year postoperative disability, and worse patient-reported outcomes (PROs) including physical function and pain interference.[15678910] These potential negative effects are especially concerning in adult spinal deformity (ASD) patients, who have malalignment or abnormal curvature of the spine and whose surgeries are more complex,[1112] are associated with more sustained opioid use,[13] and have been increasing in incidence.[14]

Given the risks of chronic opioid use, implanted devices such as spinal cord stimulators (SCS) and intrathecal drug delivery devices (IDDD) are increasingly being used as alternative treatments for chronic pain,[15] with a global market now in the billions.[16] SCSs send electrical stimulation directly onto the dorsal epidural space to counteract pain signals, while IDDDs deliver medication (opioid or nonopioid) into the intrathecal or epidural space. Various studies have looked at their effect on chronic opioid use in patients with prior failed back surgery, with conflicting results.[171819] However, these studies focused on a prior history of back surgery, and very little is known about opioid use in patients with SCSs or IDDDs who go on to have subsequent spine surgery after implantation.[20] It has been suggested in a small cohort study that they have worse outcomes and higher opioid use than nonimplanted ASD peers.[21] Given the higher risk of chronic pain and the fact that, according to a recent large-scale review of medicare patients, 15.5% of SCS patients will nevertheless have spine surgery within 3 years of initial implantation,[22] further research into opioid use in this population is warranted.

In this study, we evaluate the chronic opioid use and surgical outcomes of patients with an SCS or IDDD, hereafter referred to as the implanted group, who went on to have subsequent spine deformity surgery and compare them with a cohort of nonimplanted ASD patients.

METHODOLOGY

Matching

Inclusion criteria for the implanted cohort were adult patients who had an SCS or IDDD implanted before an elective deformity spine surgery with >5 instrumented levels at a single center and at least 6 months follow-up. We did not exclude patients whose implant was removed before the time of their subsequent deformity surgery. The controls came from a database of more than 600 nonimplanted ASD patients who also had elective surgery with >5 instrumented levels at the same center. The size of the control database allowed us to match on a wide number of variables with a 1 matching ratio (implanted:nonimplanted) so as to increase the statistical power of our comparison. Using SPSS IBM SPSS Statistics 28 (Armonk, NY, United States of America), we matched based on age (±5 years), gender, and number of instrumented levels (±2 levels, minimum 5).

Outcomes

Basic demographics (such as age and gender), past mental health history, and implant and intraoperative data were collected, as were perioperative and long-term complications. The following radiographic parameters were Pelvic incidence (PI), L1-S1 lumbar lordosis (LL), and sagittal vertical axis (SVA).

Defining opioid use

Many studies have defined “chronic” opioid use as use on most days for more than 90 days,[46] the threshold at which it has been shown that the risk of developing an opioid use disorder increases.[232425] However, there is still a great deal of variability regarding this definition,[2026] with other studies specifying use in both the subacute (3–6 months) and chronic (>6 months) preoperative period,[35] use for more than 6 months,[7] or above a minimum total morphine mg equivalents (MME) per year.[2] Given the disparity in medical charting within 3 months in our patient cohort, we use 6 months as our cutoff for defining chronic opioid use.

Opioid use was determined based on the medical chart, patient reports, and presence of active prescription data and recorded at 6 months preoperative, admission, 6 months postoperative, and final follow-up (FFU). The percentage of patients “taking” versus “not taking” at each time point was recorded. Chronic opioid use was defined as sustained opioid use (>50% of days) for >6 months preoperative or >6 months postoperative. Opioid use is often standardized using MME per day, which includes all the opioid doses a patient takes in a given day. We calculated the total MME based on the prescribed dosing as recorded in the medical record. However, given the lack of patient-reported data about actual opioid consumption, this was a potentially misleading measurement. To mitigate the effect of differential reporting, we also reported the MME per dose, assuming one dose of each prescription per day as a standardization method.

Statistical analysis

Student’s t-test, mixed ANOVA, Chi-square analyses, and Cochran’s Q test were conducted on SPSS IBM SPSS Statistics 28 (Armonk, NY, United States of America) and R.

RESULTS

Patient characteristics

Fourteen implanted patients (11 SCS, 3 IDDD) were compared against 40 nonimplanted patients. They were matched by age (average 59.4 vs. 56.3), gender (Male: Female 6 vs. 17), and number of instrumented levels [average 14.9 vs. 14.8, Table 1]. In terms of mental health and psychiatric baseline, implanted patients were overall not significantly different than nonimplanted patients in terms of depression, anxiety, chronic pain, insomnia, tobacco use, and other substance use (P > 0.05). 100% of the implanted patients had a history of any spine surgery at other centers prior to implantation, and 78.6% had a history of prior fusion compared to 52.5% with prior fusions in the control group (P > 0.05). In the implanted cohort, 50% (7/14) still had their SCS/IDDD present at their first deformity surgery at our center and in the other 50%, it had already been removed [Table 1]. Reasons for explantation included minimal response (4), infection (1), implant failure (1), and unknown (1). The implants were present for an average of 4.67 years. Compared to the nonimplanted group, the implanted group had similar preoperative PI (57.69 ± 17.01 vs. 83.8 ± 58.26, P > 0.05), less LL (−15.89 ± 40.18 vs. −35.99 ± 16.74, P = 0.0117), and higher SVA [11.84 ± 9.26 vs. 5.89 ± 8.7, P = 0.0300, Table 1].

Surgical outcomes

Intraoperatively, the implanted group had longer anesthesia time than the nonimplanted group (734.9 ± 103.4 vs. 637.2 ± 147.8 min, P = 0.0272), received more pRBCs (2.1 ± 1.6 vs. 1.1 ± 1.5 µ, P = 0.0500), and experienced more dural tears [42.9% (6/14) vs. 15% (6/40), P = 0.0309, Table 2]. They had equivalent (P > 0.05) length of stay (LOS, 8.7 ± 3.9 vs. 8.2 ± 3.7 days), estimated blood loss (EBL, 1957.1 ± 1142.2 vs. 1664.4 ± 1162.6 ml), cell saver given (CS, 653.5 ± 477.4 vs. 513.2 ± 385.9 ml), and percent of cases in which a three-column osteotomy was performed [28.6% vs. 17.5%, Table 2]. There was no difference (P > 0.05) in perioperative complications, including surgical site infection (SSI, 7.1% vs. 0%), new postoperative motor deficit (7.1% vs. 0%), acute spinal cord injury (SCI, 0% vs. 0%), postoperative CSF leaks (7.1% vs. 0%), DVTs (0% vs. 0%), or in long-term complications, such as proximal junctional kyphosis (PJK, 14.3% vs. 20%), distal junctional kyphosis, (DJK, 0% vs. 0%), pseudarthrosis (14.3% vs. 7.5%), rod fracture (14.3% vs. 20%), or screw loosening [7.1% vs. 5%, Table 3]. The average time of FFU was 3.1 ± 2.4 vs. 2.6 ± 1.7 years [P = 0.4321, Table 3]. Readmission (within 90 days) and reoperation rates were similar in both groups [14.3% vs. 12.5% and 35.7% vs. 40%, respectively, P > 0.05, Table 3]. Reasons for reoperation (implanted) included persistent malalignment (3), persistent R grip weakness (1), and wound dehiscence/postoperative CSF leak (1). Reasons for reoperation (nonimplanted) included rod fractures (5), pseudarthrosis (3), persistent malalignment (5), retroperitoneal hematoma (1), vertebral fracture (1), prominent instrumentation (1), and persistent pain (2). Postoperatively, LL and SVA were equivalent (−35.5 ± 17.9 vs. −38.2 ± 14.0 and 2.3 ± 4.0 vs. 3.2 ± 6.9 cm, respectively), with a greater LL percent correction for the implanted group [59.6% ± 88.6% vs. 4.4% ± 52.6%, P = 0.0092, Table 2].

Opioid use

Although the implanted group trended towards higher rates of opioid use at all 4 time points, there were no significant differences 6 m 50% (n = 7) versus 40% (16), 71% (10) versus. 45% (18), 6 m 64.3% (9) versus 32.5% (13), FFU: 64.3% (9) versus 37.5% (15), P > 0.05 [Table 4 and Figure 1]. The same was true for Total MME: 6 m 101.3 ± 177.8 versus 37.3 ± 89.4, 68.2 ± 77.8 versus 45.3 ± 129.9, 6 m 59.8 ± 83.1 versus 20.8 ± 46.9, FFU: 51.2 ± 68.7 versus 31.1 ± 55.5, P > 0.05 [Table 4], and for MME/ 6 m 33.9 ± 49.2 versus 21.1 ± 58.2, 55.1 ± 85.6 versus 20.4 ± 59.8, 6 m 18.3 ± 19.2 versus 11.1 ± 39.6, FFU: 19.7 ± 25.8 versus 8.9 ± 15.7, P > 0.05 [Table 4]. In both groups, the opioid use rate, the total MME, and the MME/dose remained the same between the 6 m postoperative and FFU time points, indicating that opioid use on average continued years after surgery [Figures 2 and 3].

Representative cases

Cases representative of an implanted and non-implanted patient with pre-and postoperative imaging, surgical outcomes.

DISCUSSION

This retrospective, matched cohort study of complex ASD patients found that those with prior SCS or IDDD implantation did not have higher rates of chronic (>6 m pre-or postoperative) opioid use, total MME, or greater MME per dose. Opioid use in both groups was highest on admission and then decreased slightly postoperatively but remained above preoperative levels. Implanted patients were found to be similar to nonimplanted patients in terms of mental health diagnoses and substance use history, but inherently different in terms of clinical course, with higher rates of prior spinal fusion. Implanted patients experienced longer anesthesia time, received more blood, and had more dural tears, but otherwise had equivalent perioperative and long-term complication rates, including readmission and reoperation. Implanted patients started off with significantly less LL and higher SVA, which was equalized in both groups postoperatively. Both a low LL, indicating a flat back, and a high SVA could be causes of increased pain in the implanted group. As all the devices were implanted at other centers, we could not determine their alignment preimplantation.

While the rate of opioid use, the total MME, and the MME per dose of the implanted group were not significantly higher than the nonimplanted group at any of the four time points collected, there are two trends present in the data which are worth noting. The first is that the implanted rate of opioid use was consistently 10%–25% points higher, and the MME per dose was consistently 12–35 points higher than the nonimplanted group, which could indicate a significant trend that would emerge in a larger cohort. The second is that in both groups the amount of opioid use was higher 6 months after surgery than 6 months before, and it continued at roughly the same levels between the 6-month postoperative and the FFU timepoint, on average 2–3 years later. This further highlights the risk that ASD patients, implanted or not, are at for chronic postoperative opioid use that extends well past the 90-day window.

Our findings roughly correlate with the only other study to our knowledge that has looked at opioid use in ASD patients with and without an implanted device. Daniels et al. found that patients with an SCS or intrathecal medication pump (IPT, another term for IDDDs) had worse PROs, including the Oswestry Disability Index and SRS-22r pain scores, for up to 2 years postoperatively, but had comparable total complication rates and magnitude of improvement. They also found that implanted patients had significantly higher narcotic use at baseline and 2 years postoperative.[21]

Finally, although the focus of this study was opioid use and surgical complications, we observed that the implants in our study group had a roughly 50% failure rate, given that 7 out of 14 of them had been removed by the time of surgery, at least 4 of them for minimal pain response. This is higher than the failure rate seen in some other studies,[19] and despite high rates of mechanical complications SCSs and IDDDs have largely been deemed medically safe.[2728] However, the failure rate we observed, along with the fact that 50% of our implanted patients were still on chronic opioid therapy after device implantation [Figure 1] adds to the ongoing debate regarding the efficacy of these devices for chronic back pain relief in deformity cases.[16]

The limitations of the paper can largely be attributed to its retrospective nature and small sample size. While age, gender, and number of instrumented levels were matched between groups, mental health history and substance use patterns were also found to be similar between groups at baseline, suggesting nondistinct initial populations. Despite this, the history of preoperative fusion and radiographic parameters differed, likely due to inherent variation in the preoperative anatomy and clinical course of those patients eventually requiring SCS or IDDD. Despite this, all patients included endorsed chronic back pain and underwent similarly complex and invasive spinal surgical intervention (≥5 instrumented levels). We were unable to collect sufficient opioid use data on every patient at each time point [as evidenced by the “unknown” percentage in Figure 1]. The years in which the operations of many of the patients in this study occurred were not covered by the New York State Prescription Monitoring Program Registry (PMP), necessitating our reliance on chart notes and patient reporting in the medical record, which may have been incomplete or introduced bias. As such, given this reliance on prescription data rather than patient-reported use, specific values in dosing analyses should not be strictly interpreted. Similarly, the PRO and pain score data available on retrospective review were sparse, and insufficient to perform a robust analysis. As such, we broadly infer that, among included patients, opioid dosing was informed by real-time clinical course and pain complaints, and adjusted accordingly by the primary provider.

CONCLUSION

ASD patients with SCS or IDDD do not appear to have higher rates of chronic opioid use or MME per dose compared to nonimplanted, matched cohorts. Although they have a slightly worse intraoperative course, including longer anesthesia time, blood transfusion requirement, and rate of dural tears, their long-term complication rates are not significantly different. Larger-scale studies are necessary to confirm these findings.

Conflicts of interest

There are no conflicts of interest.