Bipolar Sealer may Decrease Pain and Opioid Consumption after Primary Total Knee Arthroplasty - A Preliminary Trial

Keywords

Arthroplasty; Pain Ccore; Narcotic Consumption; Bipolar Sealer; Monopolar Electrocautery.

Abstract

Background: Bipolar sealer technology provides a continuous saline flow effectively maintaining tissue temperatures below 100°C and theoretically leading to decreased charring of soft tissue. We investigate whether this results in less pain and reduced narcotic consumption in patients following Total Knee Arthroplasty (TKA).

Methods: A retrospective review of prospectively collected data of 100 primary unilateral TKAs were divided into two historical cohorts. Each Cohort consisted of 50 consecutive patients before and after switching from a monopolar Bovie to the bipolar sealer. All other perioperative variables such as multimodal protocols, no use of tourniquet, surgical technique or perioperative mobilization were identical. All patients were discharged the next day 24 hours within surgery. Pain measurements using a Visual Analog Scale (VAS) and narcotic consumption were retracted from the longitudinal medical records and analyzed for the day of surgery, day of discharge and in total.

Results: Bipolar sealer patients reported significantly lower pain scores and narcotic usage. Day of surgery pain levels were comparatively reduced from a VAS of 4.1 to 2.7 (p < .05) and day of discharge pain levels were reduced from 4.5 to 3.1 (p < .0001), reductions of 33% and 31% respectively. Total ME administered was reduced from 35.9 mg to 26.2mg (p < .05). The preclinical characteristics of each patient cohort were not associated with the pain outcomes nor ME consumption.

Conclusion: Our preliminary trial revealed a significant reduction in pain levels and narcotic consumption in patients following unilateral TKAs with bipolar sealing technology compared to the use of the standard Bovie. This study suggests that this technology may decrease pain and narcotic consumption in patients using the exact same perioperative management. The future will show whether the increased cost of this technology will lead to a more widespread use.

Citation

Carrera CX, Kim ES, Barry K, Kobayashi A, Fitz W et al. (2025) Bipolar Sealer may Decrease Pain and Opioid Consumption after Primary Total Knee Arthroplasty - A Preliminary Trial. SM J Orthop 8: 6.

INTRODUCTION

Inadequate pain control is one of the most common reasons for delay of discharge in the fast-track primary Total Knee Arthroplasty (TKA) setting [1]. As a result, optimization of perioperative analgesia is one of the main pillars of an efficient fast-track arthroplasty program. The strategies employed to that end include the administration of multimodal systemic analgesic agents, local infiltration analgesia, and peripheral nerve blocks [2].

Bipolar sealing technology can reduce intraoperative bleeding and postoperative blood transfusion in multiple surgical subspecialties, including spine, intracranial tumor, intraabdominal, orthopaedic oncology, as well as total hip and knee arthroplasty [3-10]. The thermal energy from the bipolar electrosurgical generator leads to shrinkage of the collagen fibers within the walls of the blood vessels, with subsequent vessel contraction and ultimately bleeding cessation. The combined saline pump allows for a continuous flow of saline to cool the tissue surface, effectively keeping the surface temperature below 100°C. In contrast, the temperatures generated using standard monopolar electrocautery exceed 300°C, which results in a higher incidence of tissue charring and necrosis [11]. Theoretically, less tissue charring and necrosis translate to a decreased pro-inflammatory effect and ultimately reduced postoperative pain response.

To date, the preponderance of the literature on bipolar sealing technology in comparison to monopolar electrocautery has been centered on differences in intraoperative hemostatic efficacy and postoperative transfusion rates [9,12,13]. To our knowledge, there are no published studies comparing bipolar sealer versus monopolar electrocautery for differences in patient-reported pain scores or opioid consumption in the postoperative TKA setting.

The objective of the current study was to investigate whether bipolar sealer use leads improved postoperative pain control as assess by Visual Analog Scale (VAS) and opioid consumption as measured by Morphine Milligram Equivalents (MME) among TKA patients. We hypothesized that the impact would be most relevant during the initial postoperative period and therefore focused on patients who discharged within 24 hours after TKA.

MATERIAL AND METHODS

Patient Population

After institutional review board approval (2023P002094), prospectively collected data of TKA patients from a single institution were retrospectively reviewed. All patients underwent primary unilateral total knee arthroplasty and prior to March 28th, 2022 all patients used monopolar electrocautery. Patients over 18 years of age undergoing TKA were included if their primary indication was osteoarthritis. Patients with chronic pain syndromes, metabolic bone disorders, or rheumatic joint diseases were excluded. All patients had spinal anaesthesia using between 0.5 and 1.5mg of mepivacaine. Patients were all discharged within 24 hours of surgery. All patients underwent custom total knee arthroplasty (ConforMis Billerica, Massachusetts, USA). All patellae were resurfaced, all patients had a minimally invasive medial trivector approach, and all patients were done without a tourniquet.

All patients received 1g of Tranexamic Acid (TXA) at the time of skin incision and a second dose at the time of wound closure. All implants were placed using an individual alignment philosophy without any soft tissue adjustments or ligament releases. No lateral or any other releases were performed in any case. All implants were cemented and a pericapsular injection was injected after the arthrotomy was completed (49.25ml of 0.5% Ropivacain, 0.5mg of Epinephrine, 80mcg Clonidine and 30mg of Ketorolac in 100ml of NaCl). All knees were soaked in 0.35% Betadine solution during cement polymerization and irrigated with a total of 2L of warm 0.9% NaCl. Wound closure was performed using #2 Stratifix, for the arthrotomy, interrupted 2-0 Monocryl subcutaneously and running 3-0 Monocryl (Ethicon, Bridgewater NJ, USA) for the skin. All incisions were covered using a closed silver ion dressing (Mepilex, Moelnyke Peachtree Corners, GA, USA). All patients were mobilized after spinal anesthesia resolved. Procedures were performed with either conventional monopolar electrocautery device (ValleyLab™ electrosurgical pencil, Medtronic, Minneapolis, MN, USA) or bipolar electrosurgical radiofrequency device combined with continuous saline flow (Aquamantys™, Medtronic, Minneapolis, MN, USA). The team caring for the patient in the recovery room was blinded to whether monopolar electrocautery or bipolar sealer was used intraoperatively.

A standardized postoperative multimodal pain management protocol was administered, consisting of nonsteroidal anti-inflammatory drugs (meloxicam 7.5mg every 12 hours, acetaminophen 975mg every 6 hours, gabapentin 300mg every 8 hours (100mg every 8 hours in those over 75 years old), one dose of subcutaneous toradol 7.5mg, as well as one dose of tramadol 50-100mg and 10mg of dexamethasone prior to discharge. Subcutaneous hydromorphone 0.5 to 1mg was given as needed for severe breakthrough pain in the recovery room. Prophylactic antiemetics were administered consisting of ondansetron 4mg parenterally every 8 hour and metoclopramide 10mg parenterally every 8 hour as needed.

Study Outcomes

We aimed to understand the impact of bipolar sealer on pain control in the postoperative period. Since previous literature has shown that measuring opioid consumption post-discharge can be subject to inaccurate reporting [14], our study focused on pain control in the recovery phase prior to discharge. To further control for the possibility that recovery room length of stay may be a confounder to opoiod consumption, the study data was divided into two cohorts. Patients were either discharged the same day (SDD cohort) or stayed overnight but discharged before 24 hours (Overnight cohort). In both cohorts, outcomes were compared between 50 patients chosen at random who underwent surgery with monopolar electrocautery versus bipolar sealer.

The primary outcome measure was the difference in mean VAS pain level measurements between those who underwent TKA using monopolar electrocautery versus bipolar sealer. VAS pain levels were assessed at separate time points by nurses in the recovery room and documented in the electronic medical record (Epic, Madison, WI, USA). VAS pain scales were generally recorded every four hours while the patient was in the recovery room. All VAS pain scores were averaged to calculate the mean VAS pain level for each patient. The secondary outcome measure was the difference in opoid consumption in the recovery room. Using medication administration data from the electronic medical record, the total MME in the recovery room prior to discharge was calculated for each patient.

Statiscal Analysis

Statistical analysis was conducted using SAS software 9.4 (SAS Institute, Cary, NC, USA). Demographic and clinical characteristics were summarized using descriptive statistics. Comparisons of baseline characteristics was conducted using independent t-tests and chi-square tests. Outcome measures were reported with mean and standard deviation. Mean VAS pain scores and opioid consumption were compared using independent t-tests and Wilcoxon signed-rank tests. The adjusted and unadjusted associations between pain scores and opioid consumption and demographic, clinical characteristics and treatments were evaluated with a linear mixed model. For statistical significance, a p-value of less than 0.05 was considered significant.

RESULTS

Baseline demographics for both the SDD and Overnight cohort are presented in Table 1. Within both cohorts, patient baseline characteristics of cases with bipolar sealer versus monopolar electrocautery were similar.

Table 1: Preoperative characteristics of bipolar sealer and monopolar sealer (Bovie) patient cohorts. Age, gender distribution, preoperative pain scores.

Below not Updated

Both cohorts contained 50 patients of similar ages, gender distribution, BMIs, and preoperative pain scores (Table 1). Bipolar sealer patients reported significantly lower pain scores and narcotic usage than monopolar sealer patients (Table 2). DOS pain levels were reduced by 33%, from 4.1 (95% CI 3.9-4.7) to 2.7(95% CI 2.6-3.2) (p < .0001) (Figure 1).

Figure 1: Comparison of DOS and DOD pain scores between bipolar sealer and monopolar sealer (Bovie) patients.

Table 2: T-test comparison of VAS pain scores and MEQ administered between bipolar sealer and monopolar sealer (Bovie) patients.

Total pain levels were reduced by 31%, from 4.5 (95% CI 4.0-5.1) to 3.1 (95% CI 2.7-3.6) (p < .0001). The total morphine equivalents (ME) administered were reduced by 27%, from 35.9 (95% CI 29.1-42.8) to 26.2 (95% CI 19.7-32.8) (p < .05) (Figure 2).

Figure 2: Comparison of DOS and DOD pain scores between bipolar sealer and monopolar sealer (Bovie) patients.

The preclinical characteristics of the patient cohort were not associated with the pain outcomes (Table 3). Between genders, there was no significant difference between the mean pain scores (p-value: 0.0735). Male patients had a mean pain score of 3.32 with 95% CI of 2.91-3.73 and female patients had a mean pain score of 3.84 with 95% CI of 3.47-4.20. There was also no significant difference in pain scores between the patient cohorts of ages =70 (p-value: 0.5941). The mean pain score of patients of age =70 was 3.68 with a 95% CI of 3.30-4.07. Between three patient cohorts grouped by BMI, there was also no significant difference in pain scores (p-value: 0.7981). The mean pain score for patients with BMI 35 was 3.79 with a 95% CI of 3.16-4.41.

Table 3: Association of preclinical characteristics and pain outcomes.

There was no significant difference in mean pain scores between patients who did and did not use non-opioid analgesics (p-value: 0.0919) (Table 4). Patients who used non-opioid analgesics had a mean pain score of 3.38 with a 95% CI of 3.00-3.76, while patients who did not use non opioid analgesics had a mean pain score of 3.8 with a 95% CI of 3.46-4.23. As for MEQ opioid use, patients who received opioids of at least 10 MEQ reported significantly greater pain scores than patients who received opioids of less than 10 MEQ (p-value: 0.0319). Patients who received at least 10 MEQ of opioids had a mean pain score of 3.78 with a 95% CI of 3.47-4.08. Patients who received less than 10 MEQ of opioids had a mean pain score of 3.05 with a 95% CI of 2.47-3.62. Patients who received the bipolar sealer in arthroplasty procedure reported significantly less pain than those who received the Bovie monopolar sealer. Bipolar sealer patients reported a mean pain score of 2.95 with a 95% CI of 2.57-3.34. Bovie patients reported a mean pain score of 4.26 with a 95% CI of 3.88-4.65.

Table 4: Association of treatment factors and pain scores.

We show pairwise comparisons of pain scores between bipolar sealer and monopolar sealer patients in (Table 5). Notably, among patients who received ≥10 MEQ of opioids, the bipolar sealer cohort had a significantly lower mean pain score than the Bovie cohort (p-value < 0.0001). The bipolar sealer patients had a mean pain score of 3.07 with a 95% CI of 2.61-3.54, and the Bovie patients had a mean pain score of 4.44 with a 95% CI of 4.03-4.85.

Table 5: Pairwise comparisons of pain scores across treatment groups.

DISCUSSION

Bipolar sealer technology in TKA patients holds great potential for reducing postoperative pain levels and narcotic consumption. In addition to reported lower rates of post-operative bleeding [9,14,15], our preliminary trial suggests this technology has additional benefits in improved pain control. In our retrospective reviewed study of prospectively collected data, we found that among primary TKA patients, those treated with bipolar sealer had significantly less reported pain scores and narcotic use in the post-operative period compared to those treated with monopolar electrocautery. The presumed mechanism for reduced pain among patients using bipolar sealer is that the decreased amount of necrosis and charring leads to less inflammation and scar tissue and therefore less post-operative pain.

Patients who had TKA procedures using bipolar sealer had 33% reduction in DOS pain and 31% reduction in DOD pain with an absolute difference in reported pain score of 1.31. This difference in reported pain approached the minimal clinically important difference of 1.5 commonly used for arthroplasty studies [16]. However, it is worth noting that a MCID of 1.5 is not necessarily the only gold standard [17,18]. The lower reported pain scores also translated into less post-operative narcotic use with approximately 23% reduction in ME on the DOS (14.1mg vs 18.2mg) and 31% reduction in ME on the DOD (12.2mg vs 17.8mg) (Table 2).

The reduction of pain and narcotic consumption observed in the present study is notable, particularly when compared with other commonly accepted post-operative pain therapies. For example, in a study looking at the effect of Non-Steroidal Anti-Inflammatory Medications (NSAIDs), parecoxib achieved similar relative reductions in ME (approximately 35%) and reported pain scores (approximately 30%) among TKA patients [15]. In another study assessing use of gabapentin by TKA patients, those who received Gabapentin peri-operatively saw a reduction of approximately 30% in ME [19]. The similarities in reduction of pain and narcotic use despite the fact that all patients received NSAIDs as well as Gabapentin suggest that bipolar sealer technology could be a viable component of a multi-modal pain reduction plan among TKA patients in addition to our current multimodal pain protocols. This may lead to earlier mobilization and potentially shorter post-operative recovery period.

The ME administered on DOS in this study for the electrocautery group (18.2mg) was similar to other studies that have employed a multimodal pain regimen for TKA. For example, the ME on DOS was 17.0mg in a study using peri-articular bupivacaine/morphine/ketorolac along with a mixed narcotic and non-narcotic post-operative regimen [20]. In another study, the ME on DOS was 16.8mg for those receiving bupivacaine spinal anesthesia along with a regional block and a mixed narcotic and non-narcotic post-operatively [21]. Of note, the addition of intra-thecal morphine in the latter study decreased the DOS ME to 10.5mg [21]. The decreased opioid consumption seen in this study on the DOS after use of the bipolar sealer was of a similar magnitude as this study involving intra-thecal morphine.

A pairwise comparison further interrogated the relationship between pain across cohorts and MEQ use. Those patients in the bipolar sealer group who received more then 10mg MEQ had a significant reduction in pain scores. These results further support that the reduction in pain observed with the bipolar sealer may be additive to the benefit from pain medication. The lower opioid requirement after use of the bipolar sealer has multiple benefits that potentially could outweigh the higher cost of the device. The incremental increased cost of the bipolar sealer is $493 per case, but even so, a study of spinal fusion cases found the device to be cost-effective due to savings in transfusion-related costs [22]. Even without transfusion-related cost savings, the bipolar sealer could be cost effective. Reductions in ME have been linked to lower cost of care through decreased side effects such as respiratory depression and post-operative nausea leading to lower nursing-related costs as well as length of stay in both the post-anesthesia care unit and the hospital overall [23]. While cost-effectiveness of the bipolar sealer among total knee arthroplasty patients was not a primary focus of the present study, it warrants further investigation.

The results of this study should be interpreted in the context of its limitations. The current study is from a single academic institution and is retrospective in nature. This can limit external validity as well as introduce unmeasured bias. The two groups within the study were similar and the only notable difference between the two groups was the use of bipolar sealer versus monopolar electrocautery. A larger, multi-institutional study, ideally prospective and randomized in nature, would certainly be warranted as a future study based on the promising initial results seen in this study. Another limitation of the study is that the sample size was relatively small. However, other studies that studied post-operative pain management in TKA patients have been similar size to this study [15]. Our hope would be that larger studies using bipoloar sealer will continue to confirm the positive results on post-operative pain control. Finally, our study did not assess the direct physiologic mechanism of pain control among patients with bipolar sealer technology, so it is possible that the underlying mechanism is different than the postulated decrease in necrosis and scarring leading to less pain. Another benefit that has been shown in other studies with bipolar sealer technology is the lower rate of bleeding and transfusion needed post-operatively, however it is unclear how this would translate into lower pain scores and reduced narcotic use. In the present study, we cannot comment on blood transfusions or blood loss since neither group received any blood transfusions or neither group had any post-op CBCs drawn. Another limitation of this study is that these results are very limited to patients who stay overnight but are discharged within 24 hours. So, we cannot comment on same day discharge patients or patients who stay longer than 24 hours and further investigation is required. While it is impossible to tell with certainty, we believe the proposed mechanism for how bipolar sealer technology results in less post-operative pain is reasonable.

The results of our preliminary trial demonstrate that use of bipolar sealer in primary TKA patients may decrease post-operative pain and narcotic usage. Further studies are certainly warranted to expand upon the results presented here and to determine whether the use of this technology should be incorporated as a regular part of multi-modal TKA protocols. We believe that bipolar sealer technology use holds significant promise in continuing to meet the needs of the expanding TKA patient population reducing pain and opioid consumption.

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