Discussion

In this literature review, we found that MIS is associated with decreased rates of SSI across many different surgical procedures and among a wide variety of patient populations. SSIs are serious healthcare-associated infections with a high burden of morbidity and mortality, as well as a substantial financial cost. ^{Reference Calderwood, Anderson and Bratzler9} Numerous patient and procedural risk factors have been associated with increased risk of SSI among patients undergoing surgery, with the SHEA SSI Prevention Guideline recommending corresponding antimicrobial and procedural interventions to reduce these risks. ^{Reference Calderwood, Anderson and Bratzler9} This guideline noted that MIS procedures may be associated with a lower risk of infection but called for additional data to guide further recommendations.

MIS procedures are distinguished from open procedures by method of access, method of exposure, and extent of operative trauma. ^{Reference Varela, Wilson and Nguyen16} Patients undergoing MIS procedures are thought to have a decreased risk for SSI compared to those undergoing open procedures due to smaller surgical incisions, decreased tissue trauma and contamination, and elimination of surgical retraction. ^{Reference Varela, Wilson and Nguyen16} Furthermore, SSIs occurring after MIS may be less severe given a smaller surgical site leading to a smaller affected anatomic area. Compared to those undergoing open surgeries, patients undergoing MIS experience less local tissue trauma, less systemic stress, decreased impairment of immediate postoperative pulmonary function, and improved immunologic response, all of which contribute to improved outcomes. ^{Reference Nguyen, Lee and Goldman38–Reference Whelan, Franklin and Holubar42}

However, the benefits of MIS may be overstated given several potential sources of bias. First, sicker patients or those undergoing more complex surgical procedures may be more likely to undergo open surgery instead of MIS ^{Reference Zhao and Gu43} ; therefore, there may be a selection bias for patients who are healthier at baseline and those with less complex surgical needs to be more likely to undergo MIS compared to open surgery. Randomized controlled trials (RCTs) minimize the impact of confounding factors; however, in this literature review, we only identified 4 RCTs, with mixed results and relatively small sample sizes. Additional well-designed RCTs are warranted for further investigation into the relationship between surgical approach and risk of SSI. Notably, many of the studies identified were retrospective, and therefore prone to selection and recall bias. Second, because performing MIS requires additional, specialized training on the part of surgeons, improved outcomes in MIS may be partly due to improved technical expertise and experience among surgeons performing MIS compared to those performing open surgical procedures. Finally, MIS procedures may be more likely to occur at more highly resourced referral centers, which may have more SSI prevention interventions in place than smaller, community centers.

In conclusion, MIS has many advantages over open surgery, including decreased risk of SSIs in addition to improved cosmesis, decreased pain, and shorter hospital length of stay. ^{Reference Zhao and Gu43} As a result, MIS may contribute to decreased morbidity, mortality, and costs compared to open surgery. However, the projected benefits may be due in part to a bias for healthier or less surgically complex patients to be more likely to be selected for MIS instead of open surgery. MIS may not be appropriate for all patients or all procedures, but should be considered, when feasible, to reduce the risk of SSI.