Inactivation of spinal cord stimulator implanted pulse generators after elective surgery: an under-recognized problem

Abstract

Study design

We retrospectively analyzed a database of implanted pulse generators (IPGs) for spinal cord stimulation (SCS) implanted by a single surgeon (NDT). We additionally report a series of five illustrative patient cases.

Objectives

The electronics of SCS IPGs are susceptible to damage when implanted patients undergo surgery. Some SCSs have a dedicated surgery mode, while others recommend turning the SCS off to protect it from damage. IPG inactivation may require resetting or replacement surgery. We aimed to explore the prevalence of this real-world problem which has not been studied.

Setting

Pittsburgh, Pennsylvania.

Methods

Using a single surgeon SCS database, we identified cases of IPG inactivation after a non-SCS surgery and analyzed the management. We then reviewed the charts of five illustrative cases.

Results

Among 490 SCS IPG implantations between 2016-2022, 15 (3%) of the 490 patients’ IPGs became inactivated after another non-SCS surgery. 12 (80%) required surgical IPG replacement, while 3 (20%) were able to have their IPG function restored non-operatively. In cases analyzed thus far, surgery mode was often not activated prior to surgery.

Conclusion

SCS IPG inactivation by surgery is not a rare problem and is presumably engendered by monopolar electrocautery. Premature IPG replacement surgery carries risks and reduces the cost-effectiveness of SCS. Awareness of this problem may prompt more preventative measures to be taken by surgeons, patients, and caretakers, and encourage technological advances to render IPGs less vulnerable to surgical tools. Further research is needed to determine what quality improvement measures could prevent electrical damage to IPGs.

Introduction

Spinal cord stimulation (SCS) is an available treatment for several painful conditions, including chronic intractable back and leg pain, complex regional pain syndrome (CRPS), persistent spinal pain syndrome (PSPS), painful diabetic neuropathy (PDN), and refractory angina [1–5]. The stimulation apparatus consists of electrodes on a lead and an implanted pulse generator (IPG). Leads are placed in the dorsal spinal epidural space either percutaneously or via laminectomy, and are typically connected by wiring to an IPG, which is the software and power source for the SCS.

Since their debut, SCSs and IPGs have seen several technological advancements. A variety of brands, charging methods, lead shapes, and stimulation waveforms are now available. Despite these advances, SCSs and their IPGs continue to be vulnerable to complications such as lead failure, lead migration, and IPG failure. While hardware complications involving leads are well reported in the literature, there is little available information regarding premature inactivation of IPGs [6–8]. Each manufacturer provides a recommendation for when the patient undergoes surgery. Some devices have a dedicated ‘surgery mode’ that can be turned on prior to a procedure to protect against damage, and others recommend that the SCS should be turned off during surgery. Despite these recommendations, we have observed that IPGs are still sometimes electrically damaged in surgery. Electrocautery tools have the potential to compromise the integrity of IPGs.

Methods

Using a prospective SCS database for cases performed by a single surgeon, we identified the number of patients with IPG inactivation after a non-SCS surgery using one particular SCS manufacturer. We analyzed the outcome of IPG inactivation as to whether operative or non-operative treatment was required to re-activate or re-boot the SCS in these patients. We present 4 illustrative cases . This protocol was determined to be of exempt status by the Institutional Review Board of Allegheny Health Network with a waiver of informed consent and HIPAA authorization.

Results

490 SCS IPGs of a single manufacturer were implanted by a single surgeon between 2016-2022. Among these IPGs, 15 (3%) became inactivated after the patient underwent another non-SCS surgery. Three of these IPGs (20%) were able to be re-activated with nonoperative reprogramming while the other 12 (80%) required surgical IPG replacement. No patient that underwent IPG replacement surgery suffered a surgical complication. Four illustrative cases are summarized in Table 1.

Table 1.

Illustrative Cases.

Case	Patient Age	Patient Sex	IPG location	Surgery Leading to Inactivation	Was surgery mode used?
1	64	Male	Right buttock	Laparoscopic hiatal hernia repair with Nissen fundoplication	Yes
2	63	Male	Right buttock	Left shoulder arthroplasty	IPG turned off instead of surgery mode
3	75	Male	Right buttock	Left shoulder arthroplasty	No
4	60	Female	Right buttock	Right Sacroiliac Joint Fusion	No

Case 1:

A 64-year-old man with history of lumbar laminectomy and peripheral polyneuropathy underwent SCS implantation with IPG placement in the right buttock and reported 80% relief of his chronic low back and leg pain with no complications. Two years later, he underwent a laparoscopic hiatal hernia repair with Nissen fundoplication. Prior to the surgery, he had engaged the protective surgery mode feature of his SCS device. However, after the surgery, his IPG failed to function and was unable to be re-booted. The IPG was surgically replaced one month after the hernia repair.

Case 2:

A 63-year-old man with history of multiple lumbar surgeries and sustained low back and lower extremity pain unresponsive to conservative therapy underwent SCS implantation with IPG placement in the right buttock. The SCS provided 100% coverage of his back and lower extremity pain. Four years later, he underwent a left shoulder replacement surgery at an outside institution. He later presented to us reporting that his SCS system had not been functional since the shoulder replacement and he had called the manufacturer helpline and confirmed that the IPG was no longer working. Prior to his operation, he had reportedly turned the SCS system off rather than into the dedicated surgery mode. The IPG functionality could not be re-booted and the patient underwent surgical IPG replacement.

Case 3:

A 75-year-old man with history of low back pain and bilateral peripheral neuropathy of the lower extremities underwent SCS implantation with IPG placement in the right buttock with reported 80–90% reduction of pain and no complications. One year later, he underwent a left reverse total shoulder arthroplasty. He presented to the neurosurgery clinic reporting that he was not able to activate his SCS after the surgery and was unsure if it was still functioning. He reportedly did not activate the protective surgery mode prior to the operation. It was determined that his IPG had been inactivated and it was replaced. Two months had passed between the shoulder arthroplasty and IPG replacement.

Case 4:

A 60-year-old woman with history of lumbar fusion and chronic back and leg pain underwent SCS implantation with IPG placement in the right buttock. Two and a half years later, she underwent right minimally invasive sacroiliac joint fusion. She presented to the neurosurgery clinic reporting that the SCS system had not functioned since her sacroiliac fusion, and she had not enabled surgery mode prior to the operation. Her IPG was replaced two months after the sacroiliac joint fusion.

Discussion

While each SCS IPG manufacturer may provide their own instructions for perioperative protection of the device, there are few universally applicable, evidence-based guidelines in place. Common suggestions among system manuals include reducing stimulation to the lowest level and turning the device off prior to surgery, and using bipolar rather than monopolar electrocautery when possible [9]. Some IPGs, including those investigated in this series, have a dedicated “surgery mode” programming option that can be enabled preoperatively. Nonetheless, the 15 affected patients in this series indicate postoperative IPG inactivation continues to occur in some cases despite these protective measures.

Much of the existing literature on protecting implanted electronic hardware from electromagnetic interference (EMI) is in reference to implantable cardioverter-defibrillators (ICDs). A retrospective study by von Olshausen et al. observed 145 episodes of EMI among 2940 ICD patients, with roughly two-thirds of these incidents occurring in hospital environments, nearly all of which were attributed to electrocautery [10]. In 2011, Suresh et al. noted that altering device programming had the potential to suppress EMI, and in 2021, Terada et al. devised a modified algorithm for selecting the right intraoperative pacemaker mode [11, 12]. Intraoperative magnet use and abstinence from any intervention at all have also been evaluated as potential alternatives to preoperative device reprogramming depending on surgery location and type of electrocautery used [13].

In contrast, there is a dearth of literature on the complication of SCS IPG inactivation by surgery. While an inactivated SCS IPG may not subject patients to the same adverse events as a malfunctioned ICD IPG, it may still burden patients with loss of pain coverage which can be detrimental to their quality of life during the period before replacement. As demonstrated in the third and fourth illustrated cases, time without coverage can may last months. The costs and risks of IPG surgical replacement are significant. Each IPG replacement surgery exposes the patient to risks including infection and device-related pain [14]. Furthermore, North, et al. report an estimated base case value for IPG replacement of $26,757 [15]. While SCS patients can expect to require IPG replacement eventually, premature IPG inactivation and replacement has the potential to greatly reduce the cost-effectiveness of SCS and increase the risk of IPG-replacement complications.

Efforts to reduce the prevalence of this complication must take into consideration that in some cases, such as cases 2, 3, and 4 reported in this series, the IPG is not placed in the dedicated surgery mode preoperatively. This responsibility should be shared among patients, physicians, and device manufacturers. We recommend that implanting physicians spend more time educating patients about SCS protection during surgery.

Still, as suggested in case 1, IPG inactivation during surgery may still occur when surgery mode has been engaged. We recommend that surgeons use bipolar instead of monopolar electrocautery when possible but this can be difficult to avoid in some procedures. In cases 2 and 3, IPG inactivation occurred despite the surgical locations at the left shoulder being anatomically distant from the SCS system. Surgeons of all disciplines should be aware that there are specific precautions for implanted electrical devices such as SCS and that these devices may be damaged by surgery even if not in close proximity to the area of surgery.

Given the multitude of factors contributing to IPG inactivation by surgery, further technological development of IPGs to increase electrical durability is necessary. Even with improved education and awareness of IPG vulnerabilities and precautions, there will likely still be cases where precautions were not taken and SCS IPGs will be irreversibly damaged by another surgery. Industry efforts to design less vulnerable IPG models are necessary and perhaps remote programming could be performed to provide protections of IPGs for patients prior to surgery. Our study has several limitations including its retrospective nature and inclusion of results from a single manufacturer of SCS technology. The study is also limited by recall bias as we could not completely confirm whether patients correctly activated the protective surgery mode prior to undergoing surgery.

Conclusion

Premature SCS IPG inactivation from surgery is not a rare problem and is presumably engendered by monopolar electrocautery. This may lead to the inconvenience of loss of months of pain relief from an SCS as well as the need for re-booting or at worst IPG replacement surgery. Although not a life-threatening complication, SCS inactivation in our experience often requires replacement IPG surgery and this not only places patients at increased risk but also reduces the cost-effectiveness of expensive SCS surgery. Awareness of this problem may prompt more preventative measures to be taken by surgeons, patients, and caretakers, and may encourage technological advances to render IPGs less vulnerable to inactivation by surgical tools such as electrocautery. The responsibility of protecting SCS IPGs is shared by industry, physicians, and patients, and more research is needed to determine what quality improvement measures could be taken to prevent electrical damage to SPS hardware during routine surgery.

Author contributions

JNN acquired and analyzed the database findings and patients charts, prepared and formatted the manuscript. NE assisted with preparation and editing of the manuscript. RB assisted with preparation and editing of the manuscript. MP provided clinical insight and helped conceptualize the investigation. NDT is the senior author and helped conceptualize the investigation and contributed to manuscript editing and formatting.

Data availability

Data are available from the corresponding author on reasonable request.

Competing interests

NDT is on the surgeon advisory board at Boston Scientific and is a consultant for Abbot Neuromodulation.

Ethical approval

Conducted in accordance with the Allegheny Health Network Institutional Review Board, IRB #2022-250.

Supplementary information

The online version contains supplementary material available at 10.1038/s41394-023-00591-5.