It is well known that patients suffering from diabetes have higher levels of operative risks and surgical complications. Patients with diabetes are considered to be in an immunocompromised state with significantly higher incidence of infection including cystitis, cellulitis, and postoperative wound infection when compared to matched controls [29, 30]. The increased risk of complication associated with diabetes is related to both glycemic influence on immune function along with the long-term effects of hyperglycemia on microvasculature and collagen formation with a subsequent tendency toward impaired wound healing [30].

While no studies specific to neuromodulation have been performed examining complication rates associated with hyperglycemia, multiple studies have demonstrated that diabetes is an independent factor predicting postoperative infection risk. After controlling for all other factors, Golden et al. found that patients with mean blood glucose values >200 mg/dl within 36 h of surgery were at significantly greater risk of postoperative infection. Compared to the lowest quartile blood sugars, patients in each subsequent blood sugar quartile demonstrated increasing rates of infection [30]. Tight glycemic control during the immediate preoperative and ensuing 36 h postoperative period was highly recommended as a modifiable risk factor to reduce the rate of infection and wound-related complications. As the rate of diabetes increases, more patients are expected to seek out neuromodulation for treatment of diabetes-related morbidities such as peripheral polyneuropathy and peripheral vascular disease. When considering neurostimulation, the presence of controlled diabetes represents a consideration rather than a contraindication for neuromodulation therapies, and patients should be educated regarding risks of postoperative hyperglycemia with implementation of aggressive glycemic control interventions.

Active smoking has been identified as an independent risk factor contributing to the development of low back pain, and the incidence of tobacco use is generally greater in the patients with chronic pain [31]. Therefore, there is likely a higher incidence of smoking in patients being considered for neuromodulation therapy. Multiple randomized controlled and prospective cohort studies have demonstrated that smoking results in impaired wound healing in “clean” skin wounds. These same studies have identified that a short period of smoking abstinence reduces the risk of wound infection back to the levels of nonsmoker controls. The use of nicotine replacement therapies such as a nicotine patch has not been demonstrated to increase the rate of surgical site infection (SSI) [32]. Smoking cessation for a period of at least 3 weeks prior to surgery has been found to significantly reduce the risk of postoperative impaired wound healing as well as infection for head and neck surgery. In a randomized controlled study evaluating the effect of smoking cessation on complications related to hip and knee surgery, Moller identified significant reductions in wound-related complications, cardiovascular complications, and secondary surgery with preoperative smoking cessation for a period of 6–8 weeks with an overall complication rate of 18 % in the smoking cessation intervention group versus 52 % in the control group [33]. The beneficial effects of smoking cessation are only maintained with complete abstinence from smoking. While no studies exist specifically evaluating the effect of tobacco use on neuromodulation therapies, similar deleterious effects on neuromodulation implants can be extrapolated based on a number of studies evaluating a diversity of operative interventions [32–34]. While active tobacco use is not an absolute contraindication to neuromodulation therapy, it represents an independent risk factor for wound-related complications. As such, potential neuromodulation candidates should be educated regarding the deleterious effects of smoking on wound healing, and counseled accordingly based on the presence of concomitant risk factors such as diabetes, immunocompromise as well as obesity. All patients should be strongly encouraged to quit smoking altogether or at a minimum abstain from tobacco for a minimum of 3 weeks prior to surgery.

A number of studies have demonstrated a link between obesity and a proinflammatory state [35]. Obesity has been reported to be a risk factor for neurostimulation-related complications including SSI [2]. Obesity has not been shown to be an independent risk factor for accidental dural puncture during epidural anesthesia [36]. Obesity has been linked to a greater complication rate in adults undergoing spinal deformity correction surgery with a higher incidence of major complication as well as SSI [37]. Given the nature of neuromodulation procedures, access to the epidural space may be more difficult in obese individuals with longer operative times which in turn may be linked to greater risk of complication and infection. As such, obese patients should be counseled regarding the potentially elevated risk of major complication as well as infection. Whenever possible weight loss should be encouraged to reduce not only surgical risks but also the multitude of other risks associated with obesity. In obese individuals a goal for successful outcome following neuromodulation should be an increase in activity levels, which may lead to secondary weight loss. Therefore, while not a contraindication, obesity represents another consideration which should be weighed in accordance with other risk factors.

Morbid obesity and malnutrition are often two co-occurring, potentially modifiable risk factors for surgical intervention. Poor nutritional status has been associated with greater risk of serious adverse event following orthopedic surgery [38, 39]. Modifying preoperative risks related to morbid obesity may take longer and prove more difficult than those associated with preoperative malnutrition. Malnutrition as measured by low albumin levels (<3.5 g/dl) has been demonstrated to be associated with greater risk of major perioperative complication when compared to morbid obesity in a large cohort study of patients undergoing total knee arthroplasty. Malnutrition has been associated with increased risk of major complication including mortality, superficial and deep infection, prolonged ventilator time, pneumonia, and renal insufficiency/failure [39]. Preoperative assessment for hypoalbuminemia with appropriate supplementation may be a reasonable consideration for neuromodulation candidates who are at greater risk for malnutrition, particularly if other surgical risk factors are present.

Staphylococcus aureus is the most common pathogen associated with SSI and is responsible for approximately 25 % of nosocomial infections in the USA. Community studies indicate that 25–30 % of the population at any point in time may be colonized with S. aureus in the anterior nares [40–42]. Patients colonized with S. aureus may have a two- to tenfold greater risk of developing an SSI [43]. The overall infection risk associated with SCS implantation has been reported to range from 3.4 to 4.6 % which is significant considering the elective nature of the therapy, particularly when compared to lower incidence identified in the pacemaker literature [2, 4, 44].

In a large randomized, controlled study, preoperative screening for S. aureus and subsequent intranasal application of mupirocin ointment to colonized individuals did not reduce the risk of SSI, but was shown to significantly reduce the incidence of nosocomial infection [40]. As such, assessment for S. aureus colonization and subsequent treatment with mupirocin nasal ointment and chlorhexidine soap may reduce overall infection risk and should be a consideration prior to operative intervention.

Failed back surgery syndrome is a leading indication in the USA for neuromodulation therapies. When large midline incisions are employed for prior lumbar surgeries or during SCS/PNS lead or IPG revision surgery, it may be necessary to operate at the site of a prior incision. In a large retrospective analysis of predictive factors for complications following general surgery, operating through a prior incision was identified in 32 % of patients with postoperative wound infection [45]. Operating at the site of a previous incision may predispose to infection as a result of decreased vascularity in scar tissue. Operating through a previous incision may also be associated with more complicated procedures necessitating longer surgical times which in turn is also associated with greater infection risk [45]. When possible, neuromodulators should avoid operating through prior incision sites and should give consideration to utilizing alternate IPG sites for revision surgery, particularly in patients with a history of infection or multiple risk factors.

As the number of patients undergoing neurostimulation therapy for chronic pain increases, a growing number of case studies have been reported in the literature examining the use of SCS during pregnancy. Women of child-bearing age may have the highest incidence of complex regional pain syndrome (CRPS) [46] for which SCS has been demonstrated as an effective form of treatment [47]. Many of these women rely on SCS to maintain functional lives and reduce or avoid the burden of opioid or anticonvulsant medications which may pose risk to the developing fetus [48]. As a result of chronic pain and medication reliance, many women are not even able to consider the possibility of pregnancy until after successful treatment with neurostimulation therapies.