Surgical Approach Is a Risk Factor for Infection in Spinal Surgery
Use of a minimally invasive approach to spinal surgery is linked to lower risk for infection compared with traditional open surgery, according to a retrospective case-control analysis in the June issue of Clinical Orthopaedics and Related Research.
“From our study, we found that the minimally invasive surgery (MIS) approach was associated with a lower risk of infection than observed in patients treated with open spinal surgery,” said lead author Gerard Ee, MD, MBBS, MRCS, surgeon, Singapore General Hospital. “This was true for patients under-going MIS transforaminal lumbar interbody fusion for spondylolisthesis, laminectomy, laminotomy for spinal stenosis, or discectomy for a prolapsed intervertebral disc. We also have found diabetes, obesity, and number of intervertebral levels operated on to be the other significant independent risk factors for postoperative SSI,” Dr. Ee said.
“We hope that surgeons will be willing to use an MIS approach in treating their patients due to the lower rate of infection,” Dr. Ee said. “Moreover, patients who are at increased risk of developing a surgical site infection due to the risk factors establish could be a better candidate for choosing a MIS technique to mitigate this risk,” he added.
“This recent study adds to the growing body of literature suggesting that less invasive surgery is associated with less risk of infection,” commented Matthew J. McGirt, MD, neurosurgeon at Carolina Neurosurgery and Spine Associates, Charlotte, NC, and Adjunct Associate Professor at the University of North Carolina, Chapel Hill. “This physiologically makes sense. MIS absolutely would be expected to be associated with a lower risk for infection given that this approach has less open time, less exposure of tissue to potential contaminants, less blood loss, less tissue healing, and less devascularization than open surgery,” Dr. McGirt said.
Retrospective Case-Control Design
The researchers analyzed medical records of 2,229 patients who underwent open or MIS transforaminal lumbar interbody fusion for spondylolisthesis, laminectomy, laminotomy for spinal stenosis, or discectomy for a prolapsed intervertebral disc at a single institution between 2004 and 2010. A total of 27 cases of surgical site infection (SSI) were identified and matched with 162 randomly selected control patients without SSI.
Patients who received MIS had a significantly lower incidence of SSI (18.5% vs. 81.5%; P=0.004). Multivariate logistic regression analysis showed the following four risk factors for infection: open spinal surgery vs. MIS (OR, 5.77; P=0.048), diabetes (OR, 4.70; P=0.018), number of intervertebral levels operated on (OR, 3.49; P=0.001), and body mass index (OR, 1.18; P=0.010).
Staphylococcus aureus was the most common pathogen identified among patients with positive cultures (12 of 21 patients; 52.4%), and was methicillin resistant in four of these patients. Other pathogens identified included Staphylococcus lugdunensis, Enterobacter species, Proteus mirabilis, Escherichia coli, Acinetobacter baumannii, Klebsiella, and Morganella, Morganii.
Steep Learning Curve with Minimally Invasive Approach
“Although the MIS approach has been shown in our study to lower the effect of surgical site infection, … MIS surgery is technically challenging and associated with a steep learning curve, longer operating time, and increased complications may occur during its initial implementation,” Dr. Ee said. The authors also noted a wide confidence interval in the association between the MIS approach and the risk for infection and called for large, multicenter, comparative studies to validate the findings.
Dr. McGirt noted that “infection is just one metric of quality. Just because MIS may be associated with better infection outcomes, it is important not to extrapolate that finding to all outcomes. This study doesn’t speak to the effectiveness of care, the durability of care, or the overall safety of care. This purely looks at a very selective domain, which is infection.”
Dr. McGirt added the reduced risk for infection with MIS “is more likely to be reproducible in higher infection risk cases. So bigger cases (ie, more levels, the larger surgery that is being converted from open to MIS), have the greatest chance to realize this infection benefit. It still remains unclear whether smaller open cases (one-level decompressions and fusions) when transitioning to MIS will carry the same infection reduction.”