Risk factors for explantation due to infection after sacral neuromodulation: a multicenter retrospective case-control study

Background: Sacral neuromodulation is an effective therapy for overactive bladder, urinary retention, and fecal incontinence. Infection after sacral neurostimulation is costly and burdensome. Determining optimal perioperative management strategies to reduce the risk of infection is important to reduce this burden. Objective: We sought to identify risk factors associated with sacral neurostimulator infection requiring explantation, to estimate the incidence of infection requiring explantation, and identify associated microbial pathogens. Study Design: This is a multicenter retrospective case-control study of sacral neuromodulation procedures completed from Jan. 1, 2004, through Dec. 31, 2014. We identified all sacral neuromodulation implantable pulse generator implants as well as explants due to infection at 8 participating institutions. Cases were patients who required implantable pulse generator explantation for infection during the review period. Cases were included if age ≥18 years old, follow-up data were available ≥30 days after implantable pulse generator implant, and the implant was performed at the institution performing the explant. Two controls were matched to each case. These controls were the patients who had an implantable pulse generator implanted by the same surgeon immediately preceding and immediately following the identified case who met inclusion criteria. Controls were included if age ≥18 years old, no infection after implantable pulse generator implant, follow-up data were available ≥180 days after implant, and no explant for any reason <180 days from implant. Controls may have had an explant for reasons other than infection at >180 days after implant. Fisher exact test (for categorical variables) and Student t test (for continuous variables) were used to test the strength of the association between infection and patient and surgery characteristics. Significant variables were then considered in a multivariable logistic regression model to determine risk factors independently associated with infection. Results: Over a 10-year period at 8 academic institutions, 1930 sacral neuromodulator implants were performed by 17 surgeons. In all, 38 cases requiring device explant for infection and 72 corresponding controls were identified. The incidence of infection requiring explant was 1.97%. Hematoma formation (13% cases, 0% controls; P =.004) and pocket depth of ≥3 cm (21% cases, 0% controls; P =.031) were independently associated with an increased risk of infection requiring explant. On multivariable regression analysis controlling for significant variables, both hematoma formation (P =.006) and pocket depth ≥3 cm (P =.020, odds ratio 3.26; 95% confidence interval, 1.20–8.89) remained significantly associated with infection requiring explant. Of the 38 cases requiring explant, 32 had cultures collected and 24 had positive cultures. All 5 cases with a hematoma had a positive culture (100%). Of the 4 cases with a pocket depth ≥3 cm, 2 had positive cultures, 1 had negative cultures, and 1 had a missing culture result. The most common organism identified was methicillin-resistant Staphylococcus aureus (38%). Conclusion: Infection after sacral neuromodulation requiring device explant is low. The most common infectious pathogen identified was methicillin-resistant S aureus. Demographic and health characteristics did not predict risk of explant due to infection, however, having a postoperative hematoma or a deep pocket ≥3 cm significantly increased the risk of explant due to infection. These findings highlight the importance of meticulous hemostasis as well as ensuring the pocket depth is <3 cm at the time of device implant.