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Original research
Risk of chronic opioid use after simultaneous versus staged bilateral knee arthroplasty
  1. Lauren Wilson1,
  2. Megan Fiasconaro1,
  3. Jiabin Liu1,2,
  4. Jashvant Poeran3,
  5. Lazaros Poultsides4 and
  6. Stavros G Memtsoudis1,2,5,6
  1. 1 Anesthesiology, Critical Care & Pain Management, Hospital for Special Surgery, New York City, New York, USA
  2. 2 Department of Anesthesiology, Weill Cornell Medicine, New York City, New York, USA
  3. 3 Institute for Healthcare Delivery Science, Department of Population Health Science & Policy, Icahn School of Medicine at Mount Sinai, New York City, New York, USA
  4. 4 Department of Orthopaedic Surgery, NYU Langone Medical Center, New York city, New York, USA
  5. 5 Department of Health Policy and Research, Weill Cornell Medical College, New York City, New York, USA
  6. 6 Department of Anesthesiology, Perioperative Medicine and Intensive Care Medicine, Paracelsus Medical University, Salzburg, Austria
  1. Correspondence to Dr Stavros G Memtsoudis, Anesthesiology, Critical Care & Pain Management, Hospital for Special Surgery, New York City, NY 10021, USA; memtsoudiss{at}hss.edu

Abstract

Background Several studies have identified excess risk associated with undergoing simultaneous (compared with unilateral or staged) bilateral total knee arthroplasty (BTKA). However, few have addressed subsequent chronic opioid use. Given the substantial morbidity and mortality associated with prolonged opioid use, we evaluated the incidence of postoperative chronic opioid use following simultaneous versus staged BTKA, based on the different timing strategies of staged procedures.

Methods In this retrospective cohort study, patients who underwent BTKA procedures (2012–2016; Truven Health MarketScan; n=14 407) were classified as having undergone simultaneous or staged BTKA (<3 months, 3–6 months or 6–12 months apart). Outcomes were postoperative chronic opioid use and oral morphine equivalents prescribed on discharge. Multivariable regression models measured associations between type/timing of BTKA and outcomes. ORs and 95% CIs were reported.

Results Unadjusted frequency of chronic opioid use did not differ between groups, (Simultaneous: 11.3%, staged <3 months: 10.7%, staged 3–6 months: 11.7%, staged >6 months: 10.2%; p=0.247). In an adjusted model, there was no significant difference in the odds of becoming chronic opioid users between staged and simultaneous BTKA (staged <3 months OR 1.03, 95% CI 0.88 to 1.21/staged 3–6 months OR 0.94, 95% CI 0.79 to 1.12/staged >6 months OR 0.96, 95% CI 0.82 to 1.13; p=0.755). Patients undergoing staged BTKAs <6 months apart (compared with simultaneous) were prescribed slightly greater oral morphine equivalents on hospital discharge (staged <3 months 6% increase, 95% CI 3% to 10%; staged 3–6 months 4%, 95% CI 1% to 8%; p=0.002).

Conclusion Although patients undergoing staged BTKA <6 months apart were prescribed greater quantities of opioids on discharge, there was no significant difference in the odds of postoperative chronic opioid use compared with simultaneous BTKA. The timing of BTKA procedures does not appear to influence the likelihood of postoperative chronic opioid dependence.

  • chronic pain
  • analgesics
  • opioid
  • pain
  • postoperative
  • outcomes

Data availability statement

Data may be obtained from a third party and are not publicly available. Data are available via an institutional agreement with Truven MarketScan.

https://doi.org/10.1136/rapm-2020-102060

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    Introduction

    Significant controversy persists regarding the timing of surgery in patients suffering from bilateral osteoarthritis of the knee. While potential benefits of a simultaneous bilateral total knee arthroplasty (BTKA) include a decreased overall length of hospital stay and decreased rehabilitation time,1–3 several studies have identified an excess risk of postoperative complications and mortality compared with unilateral or staged bilateral procedures.4–6 Staged procedures may have drawbacks as well, having been associated with greater risk of mechanical complications and infections.7

    While a considerable number of studies have evaluated differences in major complications following staged versus simultaneous BTKA,8 there is a paucity of research regarding differences in postoperative recovery and pain resolution in this area. Indeed, existing studies have primarily focused on staged BTKA, comparing differences in acute pain scores after the first and second knee, rather than differences between staged and simultaneous procedures.9 Given the association between prolonged opioid use and significant morbidity (eg, development of mental health disorders, respiratory failure, overdose, etc) and mortality,10 it is important to determine if there is an optimal treatment strategy to mitigate risk of opioid dependence. Simultaneous BTKA has been associated with longer hospital length of stay and a greater likelihood of discharge to a rehabilitation facility.8 Both of these have been identified as risk factors for persistent opioid use,11 therefore, we sought to determine if staged BTKA is associated with a lower relative likelihood of persistent postoperative opioid use.

    Using nationwide claims data, we evaluated the incidence of postoperative chronic opioid use, following simultaneous versus staged bilateral TKA, while also focusing on the timing differences of staged procedures.

    Study design, data source and study sample

    Patients undergoing simultaneous or staged BTKA from 2012 to 2016 were identified from the Truven Health MarketScan database (Copyright 2017 Truven Health Analytics, All Rights Reserved; access to the Truven dataset was limited to employees of Hospital for Special Surgery). This longitudinal database contains detailed inpatient, outpatient and pharmaceutical claims data for individuals with employer-sponsored health insurance. Over 150 employers contribute to the database in addition to 20 health plans that submit data directly.

    Simultaneous BTKA was defined as one inpatient visit with both primary and secondary procedure codes for total knee arthroplasty at one inpatient visit (International Classification of Diseases ninth Revision (ICD-9) procedure code 81.54 or 10th Revision (ICD-10) procedure codes 0SRC0XX, 0SRD0XX); staged BTKA was identified as a case with procedure codes for primary total knee arthroplasty at two separate inpatient visits within a year. Procedure codes for inpatient visits are listed in chronological order. Therefore, we restricted our simultaneous definition to two consecutive procedure codes for total knee arthroplasty to minimize the likelihood of misclassifying staged BTKA performed during the same hospital admission. Patients who were not continuously enrolled between procedures, for at least 1 year before their initial surgery, or at least 1 year after their second surgery were excluded (n=29 417) as well as patients with no pharmaceutical records (n=1283).

    In 2014 (the middle of our study period), an estimated 680 150 total knee arthroplasties were performed in the USA.12 Since it has been estimated that 6% of all total knee arthroplasties are bilateral,13 there were potentially 40 809 BTKAs performed in 2014. Our study sample captured 2870 BTKAs in 2014, theoretically representing approximately 7.0% of all BTKAs in the USA that year.

    Study variables: outcomes

    The primary outcomes of interest were postoperative chronic opioid use and daily oral morphine equivalents (OME) prescribed on discharge. For staged procedures, both outcomes were defined in respect to the date of the second procedure. Chronic opioid use was defined as filling 10 or more opioid prescriptions or prescriptions for at least 120 pills within the period from 90 days to 1 year after discharge based on the Consortium to Study Opioid Risks and Trends’ definition of long-term opioid use.14 15 Daily OME prescribed at discharge was calculated based on prescriptions filled for opioids on the day of or day after discharge. The main effect of interest was timing of BTKA: simultaneous versus staged. Patients undergoing staged BTKA were further categorized as <3 months apart, 3–6 months apart or 6–12 months apart.

    Study variables: covariates

    Additional covariates considered included opioid-, patient-related and procedure-related characteristics. Opioid-related covariates included preoperative history of opioid use (specifically whether or not patients filled any opioid prescriptions in the year prior to surgery; for staged procedures, this was defined based on the first surgery), and discharge prescriptions for non-opioid analgesics. Patient characteristics of interest included patient age, sex, Charlson-Deyo comorbidity index16 (categorized as 0, 1, 2, 3+), obesity, sleep apnea, region of the USA (Northeast, North Central, South, West), median household income (as a proxy for socioeconomic status) defined by linking Metropolitan Statistical Area with US Census data (<US$45 000, US$45 000–US$60 000, >US$60 000) and insurance plan type (comprehensive, exclusive provider organizations, health maintenance organizations, preferred provider organizations, consumer-driven health plans/high deductible health plans, point of service (POS) and POS w/capitation plans). Procedure-related covariates included peripheral nerve block use, year of procedure (in order to adjust for any potential changes in perioperative care or opioid prescribing over time), length of stay (days), and discharge status (home, home health service, transfer to other facility). We additionally adjusted for readmission within 6 months of surgery (for staged procedures this was based on the date of the second procedure), to control for any other complications or surgeries that may contribute to increased opioid consumption.

    Statistical analysis

    Descriptive analyzes were stratified by timing of BTKA. Categorical variables were reported as frequencies (%) and analyzed using χ2 tests, while continuous variables were reported as median (IQR) using Kruskal-Wallis tests. A multivariable logistic regression model was run for the binary outcome of chronic opioid use. A generalized linear model with a gamma distribution and log-link to account for the skewed distribution of the outcome was run for daily OME prescribed at discharge. The main effect, timing of bilateral TKA, was included in the models as well as all additional covariates of interest. Results with a p<0.05 were considered statistically significant. All analyzes were conducted using SAS V.9.4 (SAS Institute).

    Results

    Of 14 407 included BTKA procedures, 42.8% were simultaneous, 16.6% were staged <3 months apart, 20.4% staged 3–6 months apart and 20.3% staged 6–12 months apart. In unadjusted analyzes (table 1), patients undergoing staged BTKA appeared to be prescribed slightly greater quantities of OME on discharge (staged <3 months: median 50, IQR 0–96; staged 3–6 months: median 60, IQR 0–97.5/staged >6 months: median 60, IQR 0–93.8) compared with simultaneous BTKA (median 50, IQR 0–90); p<0.001. However, unadjusted chronic opioid use did not differ between groups, (staged <3 months: 10.7%, staged 3–6 months: 11.7%, staged >6 months: 10.2%, simultaneous: 11.3%; p=0.247). Patients undergoing simultaneous rather than staged BTKAs were more often those with a lower comorbidity burden, treated in hospitals in the South or those with a non-home discharge. Patients undergoing simultaneous procedures were significantly less likely to receive a peripheral nerve block (11.3% vs staged ~52.5%;<0.001) and significantly more likely to be readmitted within 6 months of surgery (14.1% vs staged ~7.5%; p<0.001).

    View this table:
    Table 1

    Study variables by timing of bilateral total knee arthroplasty

    Trend analyzes (figure 1) revealed that simultaneous BTKA became more common over time increasing from 45.2% of all bilateral procedures in 2012 to 54% in 2016 (p<0.001), while staging period became longer with fewer patients<3 months apart (from 22.3% in 2012 to 12.7% in 2016). There was no clear pattern in median OME prescribed on discharge, with fluctuations observed over time across all BTKA categories. Incidence of postoperative chronic opioid use decreased throughout the study period across all BTKA categories (p<0.001).

    Figure 1
    Figure 1

    Trends in bilateral total knee arthroplasty (BTKA) timing (A), daily oral morphine equivalents prescribed at discharge (B) and chronic opioid use (C).

    After adjustment for relevant covariates, there was no significant difference in the odds of becoming chronic opioid users between patients undergoing (any) staged compared with simultaneous BTKA procedures (table 2; staged <3 months OR 1.03, 95% CI 0.88 to 1.21/staged 3–6 months OR 0.94,95% CI 0.79 to 1.12/staged >6 months, OR 0.96 95% CI 0.82 to 1.13; p=0.755). Patients undergoing staged procedures up to 6 months apart were prescribed greater OME at discharge compared with simultaneous (staged <3 months 6% increase, 95% CI 3% to 10%; staged 3–6 months 4%, 95% CI 1% to 8%; p=0.002). There was no significant difference in total OME prescribed at discharge between procedures staged >6 months apart and simultaneous BTKA.

    View this table:
    Table 2

    Results from multivariable models measuring the association between bilateral total knee arthroplasty timing and outcomes

    Supplemental material

    Discussion

    Within this cohort of over 14 000 BTKA patients, the majority underwent staged procedures which were predominantly spaced more than 3 months apart. An increasing trend, however, was observed for simultaneous BTKA procedures. Patients undergoing staged BTKA less than 6 months apart were prescribed greater daily OME on discharge, however, this did not correspond with an increase in the odds of postoperative chronic opioid use. While incidence of chronic opioid use was relatively high among BTKA patients (11.1%), there was no significant difference between simultaneous and staged BTKA in the odds of chronic opioid use.

    As much of the literature suggests that a staged approach rather than simultaneous BTKA is associated with lower complication risk,5 6 it is not surprizing that the majority of patients within this cohort underwent staged procedures. Likewise, procedures staged at least 3 months apart have been associated with improved complication profiles17 and this was the most commonly observed spacing in our analysis, likely reflective of the tendency to balance the desire for expedient treatment and avoidance of excess risk. Limitations on insurance reimbursement for simultaneous procedures may have also contributed to the popularity of staged approaches.18 The trend of an increasing proportion of simultaneous BTKA procedures over time may be reflective of more recent reports suggesting that simultaneous BTKA is as safe as staged BTKA procedures among selective patient populations.8

    Patients undergoing staged procedures less than 6 months apart were prescribed greater quantities of opioids on discharge than those undergoing a simultaneous approach, but still experienced no difference in the odds of chronic opioid use. In a study of acute postoperative pain following staged bilateral TKA, the authors reported that pain after the second knee was significantly greater than after the first arthroplasty, particularly when procedures were less than 6 months apart.19 In this analysis, we were unable to distinguish if chronic opioid use was attributable to pain/discomfort following the first arthroplasty or the second. However, the higher doses of opioids prescribed to patients undergoing procedures staged less than 6 months apart may have been in response to the aforementioned propensity for pain following the second procedure. Likewise, this relative increase in dose may be a consequence of prescribing to simultaneously treat pain due to both the first and second knee. While the lack of an observed difference in chronic opioid use may indicate sufficient pain management, we cannot rule out the possibility that there is inherently no major difference in postoperative pain/recovery whether patients undergo simultaneous or staged procedures. Further study is needed to identify the true underlying mechanism driving this relationship or lack thereof.

    Interestingly, preoperative opioid use was more prevalent among patients undergoing staged BTKA less than 6 months apart compared with simultaneous. This difference in preoperative opioid exposure may have served as part of the treatment selection process when deciding between a staged vs simultaneous approach. A prior study found that TKA patients using opioids preoperatively and/or reporting greater preoperative pain had a greater likelihood of prolonged postoperative opioid use.20 However, in this sample, what we believe may be greater preoperative pain in staged bilateral patients did not translate into greater risk of chronic opioid use. In these instances, the staged approach appears to have been an effective pain mitigation strategy as opioid use ceased postoperatively in a more pronounced way when compared with simultaneous BTKA.

    A prior study found that simultaneous bilateral patients fair better than staged bilateral in regards to pain 5 years after surgery.21 In addition, a more recent study using Australian data also found better pain scores 1 year after simultaneous (compared with staged) BTKA.22 Future research is warranted to determine if the observed lack of differences in postoperative opioid use persists beyond 1-year follow-up. It is possible that disparities in postoperative pain arise further into the recovery period, with simultaneous bilateral patients experiencing improved long-term functionality and pain relief relative to staged bilateral patients.

    Due to its retrospective nature and our use of administrative/claims data, this study has a number of limitations. Two of the main limitations arising from this are a lack of detailed clinical information (potentially resulting in unmeasured confounding) and potential misclassification due to the use of administrative data. As with all pharmaceutical claims data we can only confirm that patients filled prescriptions, not if and how many pills they consumed. However, if patients are filling enough prescriptions to meet the criteria for chronic opioid use it is likely that they are actually taking the medications. Additionally, several studies have highlighted under-reporting of prescription fills in claims databases.23 There is the potential that patients were taking additional opioids beyond what we could measure resulting in an underestimate of the incidence of chronic opioid use. However, it is unlikely that this under-reporting would be dependent on the timing of BTKA. Likewise, we were dependent on opioid prescribing to identify potential instances of chronic pain; future studies using patient-reported pain scores may be beneficial to validate these findings. Second, we noticed variations in opioid prescription and chronic opioid use across different years (figure 1B,C), which are likely due to the opioid pandemic and changes in healthcare practice guidelines. Therefore, we included year as an independent variable to compensate for such changes. Additionally, we were dependent on duplicate procedure codes to identify instances of simultaneous bilateral TKA, there may be instances where procedure codes are reported twice in error or for billing purposes thus misclassifying unilateral procedures and overestimating the number of patients undergoing simultaneous procedures. However, this is unlikely and should occur rarely if at all. Further, it is possible that we failed to capture some simultaneous BTKA cases where procedure codes for the two knees were not recorded consecutively. Although, in these instances it would not be possible to distinguish between simultaneous and staged procedures performed during the same inpatient stay.

    The MarketScan database only captures patients with private health insurance and contains limited data from patients over 65. Since the majority of patients undergoing total knee arthroplasty procedures are 65 and over this study failed to capture a large proportion of the patient population. While we were able to capture approximately 7% of the population undergoing BTKAs in the USA, further study with a larger, more representative cohort is necessary to validate these findings. Additionally, with large national database analyzes nested models can assist in controlling for institution or surgeon-specific patterns of care. Unfortunately, in the MarketScan database, provider identifiers are missing for a large proportion of cases. While nesting is important, we feel that variables such as the type of BTKA approach and opioid prescription patterns may be highly institution or surgeon-specific and thus may address some of these concerns.

    In conclusion, these data suggest that while the development of persistent postoperative opioid use is a concern among BTKA patients and implementation of adequate pain management/support strategies is important in this population. However, the temporal spacing of bilateral procedures, whether simultaneous or staged, does not appear to play a role in this.

    Data availability statement

    Data may be obtained from a third party and are not publicly available. Data are available via an institutional agreement with Truven MarketScan.

    Ethics statements

    Ethics approval

    Approval for this retrospective cohort study was obtained from the Institutional Review Board at Hospital for Special Surgery (IRB #2017–0169).

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    Supplementary materials

    • Supplementary Data

      This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.

    Footnotes

    • Twitter @jbLiujb, @jashvant_p, @sgmemtsoudis

    • Contributors LW: This author helped in study design/planning, data analysis, interpretation of results, manuscript preparation and review. MF: This author helped in study design/planning, interpretation of results, manuscript preparation and review. JL: This author helped in study design/planning, interpretation of results and manuscript review. JP: This author helped in study design/planning, interpretation of results, manuscript preparation and review. LP: This author helped in study design/planning, interpretation of results and manuscript review. SGM: This author helped in study design/planning, interpretation of results, manuscript preparation and review.

    • Funding This study was funded internally by the Department of Anesthesiology, Critical Care & Pain Management, Hospital for Special Surgery.

    • Competing interests SGM is a director on the boards of the American Society of Regional Anesthesia and Pain Medicine (ASRA) and the Society of Anesthesia and Sleep Medicine (SASM). He is a one-time consultant for Sandoz and Teikoku and is currently on the medical advisory board of HATH. He has a pending US Patent application for a Multicatheter Infusion System. US-2017-0361063. He is the owner of SGM Consulting, LLC and coowner of FC Monmouth, LLC. None of the above relations influenced the conduct of the present study. All other authors declare no conflicts of interest.

    • Provenance and peer review Not commissioned; externally peer reviewed.

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