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  • Is preoperative genicular radiofrequency ablation effective for reducing pain following total knee arthroplasty? A pilot randomized clinical trial

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Original research
Is preoperative genicular radiofrequency ablation effective for reducing pain following total knee arthroplasty? A pilot randomized clinical trial
  1. Puneet Mishra1,
  2. David Edwards1,
  3. Marc Huntoon2,
  4. Christopher Sobey1,
  5. Gregory Polkowski3,
  6. John Corey1,
  7. Kelly Louise Mishra1,
  8. Andrew Shinar3,
  9. Stephen Engstrom3,
  10. Cassandra Palmer4 and
  11. Stephen Bruehl1
  1. 1 Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
  2. 2 Anesthesiology, Virginia Commonwealth University School of Medicine, Richmond, Virginia, USA
  3. 3 Orthopedic Surgery, Vanderbilt University Medical Center, Nashville, Tennessee, USA
  4. 4 University of Illinois College of Medicine at Peoria, Peoria, Illinois, USA
  1. Correspondence to Dr Puneet Mishra, Anesthesiology, Vanderbilt University Medical Center, Nashville, USA; puneet.mishra{at}vumc.org

Abstract

Background and objective Although total knee arthroplasty (TKA) is an effective treatment for severe knee osteoarthritis (OA), a subset of patients experience significant postoperative pain and dissatisfaction. Several clinical trials support the analgesic benefits of genicular nerve radiofrequency ablation (GN-RFA) for non-operative knee OA, but only one prior trial has examined the effects of this intervention given preoperatively on postoperative outcomes following TKA, showing no analgesic benefit of cooled GN-RFA. The current study evaluated whether conventional thermal GN-RFA performed preoperatively resulted in significant improvements in pain and function following TKA.

Methods This was a single-center, prospective, randomized, sham-controlled, double-blinded pilot trial in which patients received either conventional GN-RFA (n=30) or sham (n=30) between 2 and 4 weeks prior to their TKA. Baseline measures were obtained preprocedurally on the day of intervention, with follow-up outcomes obtained preoperatively on the day of surgery, and at 2 and 6 weeks postoperatively.

Results Patients receiving GN-RFA showed no significant improvements relative to sham controls in the primary outcome, pain intensity at rest at 6-week follow-up. Secondary outcomes, including pain with ambulation and physical function, also showed no significant differences between groups at any follow-up assessment.

Conclusions Conventional GN-RFA of the superior lateral, superior medial, and inferior medial genicular nerves when performed prior to TKA did not provide clinically significant pain relief or improvement in functional status at 2 or 6 weeks postoperatively.

Trial registration number NCT02947321.

  • analgesia
  • pain
  • postoperative
  • pain management
  • chronic pain

Data availability statement

Data are available upon reasonable request. All deidentified participant data are in a REDCap database.

https://doi.org/10.1136/rapm-2021-102501

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    Introduction

    Although, total knee arthroplasty (TKA) is a common and effective treatment for severe knee osteoarthritis (OA), up to 20% of patients are not satisfied with outcomes post-TKA.1 A primary contributing factor to this dissatisfaction is pain, with as many as 44% of patients reporting persistent postsurgical pain (PPSP) at 3–4 years postoperatively.2 Prior findings that more intense preoperative and acute postoperative pain are predictive of developing PPSP, possibly via increased central sensitization, suggest that interventions that enhance perioperative pain control may reduce risk of PPSP following TKA.3–5

    Over the past decade, clinical trials have demonstrated the analgesic benefits of genicular nerve radiofrequency ablation (GN-RFA) in patients with non-surgical knee OA pain.6–9 Only one prior study has examined preoperative GN-RFA in TKA patients, using cooled RFA, with results showing no benefit on postoperative pain or functional outcomes.10 There are no randomized clinical trials (RCTs) to date examining postoperative analgesic benefits of preoperative conventional GN-RFA in TKA patients.

    This pilot study evaluated the efficacy of conventional GN-RFA for improving postoperative pain outcomes and functional status in patients undergoing TKA. Our primary hypothesis was that preoperative GN-RFA (compared with sham RFA) would significantly reduce pre-TKA pain intensity, and possibly via reduced central sensitization, result in significant improvements in postoperative knee pain and function.5

    Methods

    Design

    This study was a single-center, prospective, randomized, sham-controlled, double-blinded (patients and evaluators) trial for patients undergoing TKA. Patients were recruited between 26 February 2018 and 21 August 2019.

    Sample

    The sample consisted of 60 patients scheduled to undergo TKA. Inclusion criteria were: (1) age 45–79 years; (2) surgical candidate for TKA secondary to OA; and (3) radiologically confirmed diagnosis of tibiofemoral OA (Kellgren-Lawrence grade 2–4). Exclusion criteria were: (1) worst knee pain intensity on day of baseline evaluation <4/10; (2) current use of opioids>100 mg/day of morphine milligram equivalents; (3) infectious etiology (over RFA insertion site or systemic); (4) involved in a workers’ compensation claim; (5) history of adverse reaction to local anesthetic or contrast; (6) history of intra-articular injection in the last 6 weeks with steroids or hyaluronic acids; (7) prior TKA; (8) prior open knee surgery or ligament reconstruction; (9) prior RFA of knee joint; (10) connective tissue disease affecting the knee; (11) sciatic pain; (12) pacemaker; (13) pregnancy; (14) severe medical disease (serious neurological disorders, serious psychiatric disorders, suicidal, or homicidal ideation); and (15) body mass index (BMI)>50. An a priori power analysis indicated that with alpha=0.05, a sample size of 30 per group would provide at least 0.80 power for detecting a reduction of 2 scale points on the 11-point pain intensity numeric rating scale used for the primary outcome.

    Procedure

    Patients were identified through the Vanderbilt Orthopedic Clinic. Patients were presented with a summary of the study via a phone call, and if expressing interest, underwent initial eligibility screening. Potentially qualified patients interested in participating in the study were scheduled for a baseline visit at the Vanderbilt Interventional Pain Clinic 2–4 weeks prior to their planned TKA. At that time, patients provided written informed consent, and were rescreened for eligibility, including a urine pregnancy test for females of childbearing potential (≤60 years old). Patients then completed a baseline packet of outcome measures and were randomized to one of two study arms via a 1:1 computer generated block randomization (randomly determined block size of 2 or 4): RFA (conventional thermal GN-RFA) or sham (RFA needles placed in proper location without neurotomy).

    Once randomized, patients were brought into the fluoroscopy suite. While lying supine, patients were prepped and draped. Under fluoroscopy, the target locations based on bony landmarks of the superior lateral (SL), superior medial (SM), and inferior medial (IM) branches of the genicular nerve were determined. Patients were sedated with midazolam (up to 2 mg) and fentanyl (up to 100 μg). The skin was anesthetized with 2 mL of 2% lidocaine at each of the needle insertion sites (total of 3). Next, the RFA needles (Abbott Laboratories, 20-gage, 10 cm length, 15 mm activated tips) were placed in the proper location under fluoroscopic guidance. In the anterior–posterior fluoroscopic view, the SL, SM, and IM branches were identified at the junction of the lateral distal femoral shaft and lateral condyle, medial distal femoral shaft and medial condyle, and medial proximal tibial shaft and medial condyle, respectively. In the lateral fluoroscopic view, the needles were positioned at the 2/3 depth of the femur (SL and SM) or tibia (IM).

    Both sensory and motor testing were performed to ensure proper needle placement in reference to the genicular nerve branches. Up to this point, the procedural technique was identical for both the RFA and sham control groups. Next, for the RFA group only, 2 mL of 2% lidocaine was injected into each of the three needles before the RFA probes were connected to the RFA generator and the generator was activated. Two cycles of 90 s each at 2 Hz were conducted at 80°C, with the needle retracted to 1/3 the depth of the femoral and tibial shaft for the second cycle. For the sham control group, an empty syringe was connected to each needle to mimic the action of injecting local. Unknown to sham patients, the RFA probes for this group were not connected to the RFA generator (no neurotomy), although the generator was activated. Patients were monitored for 30 min postprocedurally and were then discharged.

    Within 2–4 weeks following the study intervention, patients underwent their TKA. All patients received a protocolized regimen of medications perioperatively (see online supplemental materials).

    Supplemental material

    Measures

    Outcome measures were completed by patients prior to the intervention at the baseline visit described above, preoperatively on the day of the TKA procedure, and at 2 and 6 weeks postoperatively. The primary outcome measure was knee pain intensity at rest at the 6-week follow-up. Pain intensity at rest at the remaining follow-ups and pain intensity with ambulation were secondary pain outcomes. Both pain outcomes were composite scores (on a 0–10 scale) based on the mean of ratings of best, worst, and average pain in the past 24 hours using an 11-point numerical rating scale format (anchors of “no pain” and “worst possible pain”). Functional status (secondary outcome) was assessed using the Patient Reported Outcome Measurement Information System (PROMIS) Physical Function Short Form 8a scale (V.1.0), a well-validated measure of physical function. Raw scores were converted to T scores (reflecting a population mean of 50 and SD of 10) based on recommended PROMIS scoring guidelines, with lower scores indicating greater functional limitations.11 12

    Statistical analysis

    All analyses were conducted using SPSS for Windows V.26. Prior to analyses, change scores were separately derived for the differences between each outcome at baseline and the respective outcome on the day of surgery (DOS) and at 2-week and 6-week follow-up. Larger positive change values indicated greater improvement for each. Outcomes were normally distributed (Kolmogorov-Smirnov test, p’s>0.19). Analyses of patient characteristics and baseline outcome measures across intervention groups used χ2 tests (categorical measures) or between-subject t-tests (continuous measures). Intervention outcome data were analyzed using a series of between-subject t-tests, with multiple imputation used to address missing data. In each analysis, intervention group (RFA vs sham) was the independent variable and changes in outcomes from baseline to each follow-up were the dependent variables. The primary outcome was changes in pain at rest at the 6-week follow-up. For the pain at rest and pain with ambulation outcomes, n=3 cases were missing 2-week follow-up data and n=3 were missing 6-week follow-up data. For the PROMIS Physical Function measure, n=11 cases were missing 2-week follow-up data and n=8 were missing 6-week follow-up data.

    Given the sex imbalance between the groups despite randomization, we also conducted post-hoc secondary analyses to test for sex differences in primary and secondary outcomes between RFA and sham groups. These analyses used an analysis of variance approach, with models including the main effects of intervention group (group) and sex, and the group × sex interaction. A two-tailed probability value of p<0.05 was used as the criterion for significance in all analyses.

    Results

    Baseline characteristics

    Table 1 summarizes baseline characteristics across intervention groups. Despite randomization, RFA group participants were younger, had higher BMI, and were less often female. Both groups had statistically similar, moderate intensity pain at rest and pain with ambulation at baseline. Both groups also showed similar, clinically meaningful functional limitations on the PROMIS Physical Function measure at baseline.

    View this table:
    Table 1

    Baseline sample characteristics by intervention group

    Intervention effects on outcomes

    Unadjusted means for composite pain intensity at rest across the full trial period are summarized graphically by intervention group in figure 1. Analyses of the primary outcome (changes in pain at rest from pre-RFA baseline to the 6-week follow-up) revealed no significant differences between the RFA and sham groups (p=0.67). Secondary analyses of changes in pain at rest from baseline to DOS (p=0.45) and the 2-week follow-up (p=0.90) also did not reveal any significant effect of the RFA intervention relative to sham RFA.

    Figure 1
    Figure 1

    Unadjusted means for the primary composite pain intensity at rest outcome across the full trial period. This figure shows the composite pain score at rest for both the radiofrequency ablation (RFA) group and the sham group at baseline, on the day of surgery, and at the 2 and 6-week follow-up.

    Unadjusted mean values for the secondary measures of pain with ambulation and PROMIS Physical Function are presented in table 2. Analyses of the pain with ambulation secondary outcome failed to reveal any significant differences between the RFA and sham groups in changes from pre-RFA baseline to DOS (p=0.42), 2-week follow-up (p=0.71), or 6-week follow-up (p=0.59). Similarly, changes in the PROMIS Physical Function secondary outcome did not differ significantly between RFA and sham groups at 2-week follow-up (p=0.39) or 6-week follow-up (p=0.06).

    View this table:
    Table 2

    Unadjusted means (SD) for secondary outcomes across the trial

    Post-hoc exploratory analyses of possible gender differences in intervention responses did not reveal significant group × sex interactions for changes in pain at rest from baseline to DOS (p=0.64), or 2-week (p=0.74) or 6-week follow-up (primary outcome; p=0.71). Sex also did not significantly moderate intervention effects for changes in pain with ambulation from baseline to DOS (p=0.65), 2-week follow-up (p=0.84)), or 6-week follow-up (p=0.42). While men and women did not differ significantly in effects of RFA on improvements in physical function at 6-week follow-up (p=0.24), they did differ significantly at 2-week follow-up (F(1,45)=29.94, p=0.016). Estimated marginal means revealed that sham males improved (mean=4.6, SE=2.07), whereas RFA males worsened slightly (mean=−2.3, SE=1.52). In contrast, sham females worsened slightly (mean=−1.2, SE=1.33), while RFA females remained unchanged (mean=0.1, SE=1.58).

    Discussion

    This study evaluated whether a pre-TKA GN-RFA could provide significant pain relief and improve functional outcomes following TKA. Results of this study demonstrated that pre-TKA GN-RFA of the SL, SM, and IM genicular nerves did not improve pain at rest at 6-week follow-up, the primary outcome. Furthermore, no relative benefit of GN-RFA over sham RFA was observed for any secondary pain or functional outcome at any point in the trial. Post-hoc exploration of whether sex moderated the effects of the intervention failed to reveal significant benefits of GN-RFA in terms of pain or function for males or females.

    This is only the second study to examine the possible efficacy of preoperative GN-RFA for reducing postoperative pain and improving functional outcomes in TKA patients. Walega et al previously evaluated the efficacy of preoperative cooled GN-RFA13 in TKA patients, while the current study used conventional thermal GN-RFA. Despite these differing intervention techniques, both studies similarly found no appreciable benefit for TKA patients receiving GN-RFA preoperatively.13

    In the current work, we note that the effect size assumptions used in the a priori power analysis may have been overly optimistic. As a result, the study was underpowered to detect intervention effects, if present, of a smaller magnitude. However, given the total absence of even a trend for GN-RFA efficacy in any outcome, it appears very unlikely that increased statistical power would have changed the overall negative pattern of findings.

    Negative results of the current work and the prior similar TKA study are somewhat surprising in the broader context of several studies that have shown GN-RFA to be an effective treatment modality for non-operative patients with OA-related knee pain.6–9 In an RCT, Choi et al demonstrated that patients receiving conventional GN-RFA for chronic knee OA experienced significant improvements in pain and overall satisfaction compared with a sham group at 1, 4, and 12-week follow-up.6 Using an alternative cooled GN-RFA approach, Davis et al compared RFA to intra-articular steroid (IAS) knee injection in a multicenter RCT. At 6 months, the cooled GN-RFA group had a significant improvement in pain and global perceived effect.7 Similarly, in an RCT of conventional GN-RFA versus IAS knee injections, Sarı et al found that GN-RFA was associated with significant reductions in pain and improvement in function relative to IAS at 1-month follow-up.8 Lastly, Chen et al explored the efficacy of cooled GN-RFA versus intra-articular knee hyaluronic acid injection for chronic knee pain. This multicenter RCT found that the cooled GN-RFA group experienced significantly greater improvement in pain and function at 6 months.9 Thus, there is consistent high-quality evidence for an analgesic benefit of GN-RFA in non-operative knee pain patients.

    In contrast to these positive findings, all current evidence regarding potential benefits of preoperative GN-RFA on post-TKA pain and function is uniformly negative. There are several possible reasons for these discrepancies. First, post-TKA patients may experience pain that is different in location and nature than the baseline chronic OA pain for which GN-RFA appears to be effective. Post-TKA pain can manifest in the inferolateral or posterior aspects of the knee, and were not covered in this study due to risk of neural or vascular damage.10

    Another possible explanation for the discrepant results above relates to differences in clinical procedure. Both our study and similar work by Walega et al did not employ a diagnostic GN block prior to conducting the RFA procedure.13 Even though there is evidence that diagnostic GN blocks do not improve the rate of GN-RFA treatment success, it is still often performed in standard practice due to local coverage determinations of numerous insurance carriers.14 Importantly, the studies conducted by Choi et al., Davis et al, and Chen et al all included diagnostic GN blocks.6 7 9 Therefore, it is possible that by not excluding patients displaying less than 50% relief with diagnostic blocks from our study sample, the number of non-responders in the GN-RFA arm was greatly increased, and any clinical benefits were diluted.

    A final potential driver of negative findings for GN-RFA in TKA patients relates to the GN-RFA technique itself. There is growing debate in the literature about the most accurate location and number of GN that RFA should target. Our study was designed based on the Choi et al trial with GN-RFA performed at three locations using traditional landmarks.6 However, since our study began enrollment, there have been numerous articles discussing revised landmarks to improve accuracy.15–18 It is now suggested that the traditional GN-RFA lesion locations (SM, SL and IM) are likely inadequate and that up to ten distinct RFA lesions may be necessary to achieve maximum likelihood of efficacy.19 20 Lastly, using larger electrode sizes with cooled RFA has also been shown to more successful than conventional RFA due to an increased area of ablation.20 In a broader context, this corresponds with recent guidelines for the lumbar spine, which state that larger lesions may improve outcomes.21

    This study did not demonstrate any beneficial effect of preoperative GN-RFA on post-TKA pain and functional status. Future studies with GN-RFA in this setting should incorporate these updated techniques, which may enhance efficacy.

    Data availability statement

    Data are available upon reasonable request. All deidentified participant data are in a REDCap database.

    Ethics statements

    Ethics approval

    The protocol was institutional review board approved, and written informed consent was obtained for each patient. This study adheres to Consolidated Standards of Reporting Clinical Trials guidelines.

    Acknowledgments

    We would like to acknowledge the Vanderbilt Perioperative Clinical Research Institute for their time and contributions to this study. We would like to express gratitude to our study coordinators Denise De la Torre and Douglas Luckett for their diligence and hard work throughout this trial.

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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 @SobeyChris

    • Contributors PM, DE, MH, CS, GP, JC, AS, SE, and SB all contributed to study design, data collection, results analysis, and writing and editing of the manuscript. CP contributed to data collection and manuscript review. KLM contributed to study design, and manuscript writing and editing.

    • Funding This investigator-initiated clinical trial was funded by a grant from Abbott/St. Jude Medical. The study was also supported in part by National Institutes of Health grant R01AG048915 (SB).

    • Competing interests None declared.

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