INTRODUCTION
Deep brain stimulation (DBS) is a surgical intervention used to treat movement disorders like Parkinson’s disease, essential tremor, and dystonia, as well as some psychiatric disorders, and epilepsy. Although recent advancements in technology have extended the lifespan of implantable pulse generator (IPG), they typically require replacement every 3-5 years for non-rechargeable systems and 7-10 years for rechargeable models. As survival period following initial DBS surgery has improved dramtically, the number of individuals requiring IPG replacements is steadily increasing.
Unipolar electrocautery (BOVIE), frequently employed in surgery, is used to facilitate dissection procedures. However, its use in IPG replacement surgery is contraindicated due to the risk of energy transfer to the implanted system, potentially resulting in hardware damage, tissue injury, and serious complications [7,11]. Therefore, traditional tools such as scissors and knives have been predominantly utilized for replacement surgery to date. However, damage to the device can occur during this process, and in the worst case, the device system could become unusable. Consequently, this surgery takes a lot of time and places considerable stress on the surgeon. Additionally, in the event of equipment damage, both financial and human costs are incurred.
The PEAK PlasmaBladeTMX (PBX; Medtronic, Minneapolis, MN, USA) (Fig. 1 and Supplementary Video 1) is a novel surgical device that generates high-frequency pulses to induce electrical plasma along the edge of a thin (12.5 μm), almost entirely (99.5%) insulated electrode. Operating at substantially lower temperatures (40-170°C) compared to conventional unipolar electrocautery (200-350°C), PBX operates well below the melting temperature of neurostimulation electrodes (188°C) or intrathecal catheter coatings (200-210°C) [6]. When utilized with implantable cardiac electronic devices, including pacemakers and defibrillators, the risk of hardware or lead damage is notably minimized rendering its adoption increasingly prevalent [4]. IPG in DBS share a remarkably similar structure to cardiac electronic devices. Additionally, the safety of utilizing a PBX for replacing a DBS device has been documented by a British research group [13].
In this study, we aimed to confirm the safety and effectiveness of using PBX for DBS IPG replacement surgery, as well as to identify potential risk factors for complications associated with IPG replacement procedures.
MATERIALS AND METHODS
Patients
After obtaining institutional IRB approval of Severance hospital (1-2021-0063), a prospective study was conducted on patients requiring IPG replacement following DBS at a single institution (Severance Hospital) from July 2022 to August 2023. IPG replacement surgery was performed using PBX on 50 patients who obtained consent after receiving adequate explanation. These patients were followed up at an outpatient clinic at intervals of 1 day, 2 weeks, 1 month, 3 months, and 6 months after surgery to evaluate impedance abnormalities, surgical complications, and clinical status.
In parallel, the control group was established through a retrospective cohort consisting of 150 consecutive patients who had undergone IPG replacement surgery prior to July 2022. The patients were also checked for abnormal impedance, surgical complications, and clinical status up to 6 months after surgery. Surgeries in both the prospective and retrospective groups were performed by three surgeons : JWC, KWC, and SWH.
IPG replacement surgical procedure
All surgeries involved the replacement of the IPG into the subfascial space within chest wall below the clavicle. Both the target group (PBX group) and the control group (conventional method group; non-PBX group) underwent surgery under general anesthesia.
Evaluation
The age, sex, underlying diseases (hypertension, diabetes, use of antiplatelet or anticoagulant drugs), diagnosis that required DBS surgery, whether unilateral or bilateral surgery was performed, and the number of reoperations in the same area were compared between the two groups. Additionally, surgery time, impedance abnormalities, and surgical site complications (hematoma, dehiscence or delayed healing, and infection) were evaluated. Surgical time was defined as the duration from skin incision to closure.
Impedance was considered abnormal if it exceeded the cutoff value (3000 Ω) or if an open circuit occurred at any contact. Delayed wound healing was defined as a scenario where stitch removal was not feasible on the 9th day after surgery (the standard stitch removal date at our institution), necessitating stitch removal 2 weeks after surgery, or requiring additional wound management thereafter.
Statistical analysis
The statistical analysis was conducted using SPSS Statistics for Windows, version 26.0 (SPSS Inc., Chicago, IL, USA). Fisher’s exact test was used when the expected frequency of a nominal variable was 5 or less, and the chi-square test was used for higher frequencies to confirm statistical significance. Continuous variables were analyzed using the Student’s t-test for normal distributions or the Wilcoxon rank sum test for non-normal distributions.
A binary logistic regression analysis was performed to assess the factors affecting wound dehiscence and delayed healing. Variables such as PBX usage, age, gender, comorbidities, diagnosis, and the number of reoperations were included as independent variables. A receiver operating characteristic (ROC) curve was generated using probability values from the logistic regression analysis. Statistical significance was set at p<0.05.
RESULTS
Table 1 presents the basic demographics of the patient cohort analyzed in this study. The average age was 63.92 years in the PBX group and 61.65 years in the non-PBX group, with no statistical difference between the two groups (p=0.285). Regarding sex distribution, there were 28 males and 22 females in the PBX group, and 78 males and 72 females in the non-PBX group, with no statistical difference between the two groups (p=0.744). In terms of comorbidities, there was no statistically significant difference between the PBX and non-PBX groups regarding hypertension, diabetes, and previous use of antiplatelet agents or anticoagulants (18 vs. 45, 11 vs. 22, and 3 vs. 9, respectively; p=0.645, p=0.598, p=1.000, respectively).
In terms of diagnoses for which DBS was performed, the most common diagnosis in both groups was Parkinson’s disease (28 in the PBX group, 87 in the non-PBX group), followed by dystonia (13 in the PBX group, 29 in the non-PBX group), and essential tremor (six in the PBX group, 27 in non-PBX group). Statistical analysis revealed no significant difference between the two groups (p=0.599).
There were 12 patients in the PBX group and 36 patients in the non-PBX group underwent replacement surgery on both sides with no statistically significant difference observed (p=0.848).
Regarding the number of reoperations in the same area, the PBX group had 11 individuals vs. 36 individuals in the nonPBX group for two operations, 24 vs. 75 individuals for three operations, 12 vs. 33 individuals for four operations, 3 vs. 6 individuals for five times. Once again, no statistical difference was found (p=0.902).
Table 2 shows the surgical complications observed in both groups. In the PBX group, there was no significant change in impedance before and after surgery in any patient. There was also no significant change in impedance at the 6-month postsurgery checkup. In the non-PBX group, six patients showed electrode abnormalities within the normal impedance range before surgery, and this remained the same when measured 6 months after surgery.
In terms of surgery time, a statistically significant difference was noted between the two groups, with a median of 31 minutes in the PBX group and 33.5 minutes in the non-PBX group (p=0.005). Although impedance abnormalities occurred only in the non-PBX group, this disparity between the two groups was not statistically significant (p=0.334). Two of the six patients had issues with the electrodes they were using, requiring one patient to have their symptoms managed with alternative contacts, while another patient had to have all extensions replaced after reopening a previous scalp wound.
When examining complications related to surgical wounds, postoperative hematoma occurred in two patients in the PBX group and seven patients in the non-PBX group, but the difference was not statistically significant (p=0.677). Wound dehiscence or delayed wound healing manifested in three patients in the PBX group and 10 patients in the non-PBX group; however, this disparity did not reach statistical significance (p=1.000). Postoperative infection did not occur in the PBX group and occurred in two patients in the non-PBX group. However, there was no statistical difference (p=1.000). Overall wound-related complications showed no statistical difference between the PBX group and the non-PBX group, with five and 19 patients, respectively (p=0.249).
Table 3 integrates the two groups and categorizes them into those experiencing wound dehiscence and delayed healing, and those without such complications. PBX usage, age, gender, comorbidities, diagnosis, and number of reoperations were included as dependent variables. The results stem from binary logistic regression analysis with these independent variables. The significance probability according to the Hosmer test was 0.965, and the Negelkerke R2 (coefficient of determination) was 0.558. Other variables were not statistically significant, but diabetes mellitus was statistically significantly (p=0.012), with an odds ratio of 20.495.
Fig. 2 draws the ROC curve generated using the probability value of derived from the binary logistic regression analysis. The area under the ROC curve (AUC) was 0.962, with a standard error of 0.023 and a significance probability of 0.000.
DISCUSSION
IPG replacement surgery is not recognized as a major surgery, but as mentioned earlier, the frequency of surgery is increasing, making its importance greater than before. This study is also significant because, to the best of the authors’ knowledge, it is the first paper to prospectively and retrospectively analyze the usefulness of new surgical instruments and risk factors for surgical complications, specifically focusing on IPG replacement surgery.
The authors believe that the small sample size in the PBX group likely contributed to the lack of statistical significance. A reverse calculation, based on the observed incidence of abnormal impedance in the PBX group (0%, 0/50) and the non-PBX group (4%, 6/150), suggests that a statistically significant difference would only be observed if no adverse events occurred in approximately 4906 patients. This is attributable to the inherently low incidence of abnormal impedance, even with the conventional method. Nevertheless, despite the absence of statistical significance, the finding is noteworthy, as not a single patient in the PBX group exhibited an impedance abnormality. This suggests that the mechanism of the new device—operating at a temperature below the melting point of the neurostimulator—is effective, which is consistent with previous findings [13].
There was no statistically significant difference in the basic characteristics of the two groups (Table 1). Additionally, since all the surgeons involved had more than 2 years of experience performing this surgery, it can be presumed that there is no significant learning curve. Therefore, there are no major issues in comparing the surgical outcomes between the two groups (Table 2). However, it’s important to note that in the analysis of comorbidity, only the three most common and influential factors on postoperative wounds were considered. This limitation may affect the interpretation of the results.
Complications
In terms of surgery time, although non-parametric analysis was conducted due to the non-normal distribution of data in both groups, a statistically significant difference was observed (Table 2). As mentioned earlier, while no statistical difference was detected in impedance abnormalities, it is noteworthy that no impedance issues in the PBX group. Furthermore, consistent with the previous reports, we observed no issues when the PBX tip made direct contact with a non-isolated part of the hardware. Even in cases where dissection was necessary due to adhesion of the extension line to the fascia layer, the operator could perform dissection with confidence by using the PBX. This likely contributed to the reduction in surgery time.
Although there was no statistical difference between the prospective and the retrospective groups in the terms of postoperative wound-related complications, the PBX group appeared to have a lower complication rate. Despite the lack of a statistical difference, it may be inferred that this new surgical instrument does not lead to a higher incidence of surgical wound complications compared to traditional surgical methods.
Studies examining the use of PBX to other surgeries have reported similar findings. A report on PBX use in traumatic retinal detachment highlighted its advantages in dissolving dense fibrovascular hands, minimizing bleeding, and performing surgery without tractional tears [12]. Similarly, a study involving tonsillectomy reported an odds ratio of 1.20 (95% confidence interval, 0.52 to 2.72) for postoperative bleeding in the PBX group, indicating no significant difference in safety related to bleeding compared to traditional monopolar coagulators.
Although this study did not investigate cosmetic outcomes, a report indicated that cosmetic results in the group utilizing PBX during cesarean sections were significantly better than in the scalpel group [2]. Moreover, in a study involving canine mastectomies, a device similar to PBX showed a lower degree of necrosis due to thermal damage extending beyond 1000 μm [5]. Even when used in non-invasive blepharoplasty due to its mechanism of contracting the epidermis and dermis [3], it was reported that the surgery was performed without complications.
Regression analysis
When logistic regression analysis was performed, only diabetes history was found to have a significant effect on postoperative dehiscence and delayed healing (Table 3). A regression analysis of other complications such as hematoma, infection, and overall complications did not identify any significant coefficients. Fig. 2 shows that the AUC is 0.962, with a standard error of 0.023 and a significance probability of 0.000, indicatingthat the prediction performance through binary logistic regression analysis was excellent and statistically significant.
It is well-known that diabetes can lead to delayed wound healing [8]. In diabetic patients, various factors contribute to this delay, including stress, decreased oxygen supply, infection, reduced blood flow, impaired proliferation and migration rates, diminished growth factor production, impaired proliferation and migration of keratinocytes, and altered vascular endothelial mediators [9]. Although a more detailed analysis (e.g., whether blood sugar was controlled after surgery) was not included, Table 3 confirms that diabetes has adverse effects on surgical wounds in IPG replacement surgery.
Another noteworthy observation is that the number of reoperations was not related to complications, contrary to expectations. After IPG is implanted, it becomes encapsulated by fibrous tissue and biofilm over time [1], and IPG replacement carries a three-fold higher risk of infection compared to the initial surgery [10]. It could be easily assumed that the risk of complications such as infection would increase with the number of surgeries, but statistical analysis showed no significant difference between the first and subsequent reoperations.
Limitation
Limitations of this study include potential biases arising from the comparison between a prospective group and a retrospective control group. Additionally, since the study was not conducted as a blind test, inherent biases may have influenced the outcomes. The relatively small sample size also suggests that further large-scale studies are necessary to fully validate these findings.
CONCLUSION
This study provides valuable insights into the application of the PEAK PBX for DBS IPG replacement surgeries. Our findings suggest that PBX offers a safe and effective alternative to conventional techniques, with notable reductions in surgical duration and no observed impedance abnormalities. While wound complications did not significantly differ between groups, diabetes emerged as a significant predictor of adverse outcomes, underscoring the importance of preoperative risk assessment and tailored management strategies.
Further research involving larger cohorts and prospective designs is warranted to corroborate these findings and elucidate additional factors influencing surgical outcomes. Despite the limitations of this study, including the potential biases arising from comparing a prospective group with a retrospective control group, the results support the utility of PBX in DBS IPG replacements.
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