To the best of our knowledge, this is the first study to clarify the incidence of SSIs after using the intraoperative O-arm/navigation system for spinal surgeries. Preoperative clinical status and use of instrumentation, but not intraoperative CT/navigation, was associated with SSIs after spinal surgeries.
The incidence of SSIs in spinal surgery varies widely, and a large database indicated an incidence of 0.72% for laminectomy with no risk factors to 8.7% for refusion of the spine in patients with three risk factors . In the Medicare population, Kurtz et al. reported the rate of SSIs in instrumented patients as 8.5% in primary fusions and 12.2% in refusions . In our SSI prevention protocol, the incidence of SSIs when either the C-arm, O-arm, or both were used togetheter were 7.3%, 4.7%, and 8.3%, respectively, and are similar to those reported in previous studies of instrumented spinal surgeries .
Several studies have identified risk factors for SSIs in spine surgery. A recent meta-analysis reported 13 risk factors that were statistically significant . Those that were modifiable through patient selection and optimization included ASA-PS of > 2 (OR, 2.27; 95% CI: 1.5–3.42), diabetes (OR, 2.04; 95% CI: 1.69–2.46), obesity (OR, 2.21; 95% CI: 1.55–2.93), BMI (OR, 0.25; 95% CI: 0.1–0.4), revision surgery (OR, 1.85; 95% CI: 1.46–2.34), smoking (OR, 1.17; 95% CI: 1.03–1.32), urinary tract infection (OR, 3.19; 95% CI: 1.68–6.06), hypertension (OR, 1.67; 95% CI: 1.26–2.22), CSF leak (OR, 3.22; 95% CI: 1.07–9.67), and dural tear (OR, 3.01; 95% CI: 1.6–5.66). Although age was not a significant factor, other studies have reported that older age was a significant risk factor independent of comorbidities. Additionally, patients with diabetes have been shown to have worse patient-reported outcomes for up to two years after spine surgery . In our study, patients with SSIs did not have diabetes, and diabetes was not a risk factor for SSI. These results raise the real possibility that stringent glycemic control may mitigate the risk of SSIs. Our study suggested the severity of neurological findings as JOA score were associated with SSIs. Therefore, we need to pay attention to prevent SSIs in patients with severe cervical spondylotic myelopathy and spinal cord injury. Moreover, a systematic review showed that 2 of the 6 studies found a statistically significant association between instrumentation and postoperative SSI . Therefore, the author concluded they could not rule out a possible association. Further analysis of the role instrumentation as independent risk factors for SSIs was beyond the scope of this initial study and will be explored in the future.
A common source of contamination in spine surgery is the use of a “C-arm” for intraoperative fluoroscopy. To maintain sterility, a sterile drape is placed over the portion of the machine that will be in close contact with the operating field. Biswas performed a prospective study to assess the sterility of C-arms at the end of 25 spine surgery cases . Five areas of the C-arm were cultured immediately after drape application and at the end of surgery. One location (4%) was culture positive after immediate draping. All drapes were cultured at the end of the procedure, and all areas were contaminated, with the upper areas of the C-arm being most frequently contaminated. The authors recommend that these regions need to be considered nonsterile. The use of intraoperative CT and navigation systems is unlikely to cause intraoperative contamination more than the use of intraoperative fluoroscopy. Since there was no significant difference in the incidence of SSIs between the use of C-arm and O-arm, SSIs may be more associated with factors other than with the surgical environment.
Our study has several limitations. First, in our protocol, surgical methods, type of instrumentation, surgeons, and the number of operating room staff were different between all the techniques. Second, the cultures of the C-arm and O-arm equipment were not examined before and after surgery. Therefore, the mechanisms underlying development of the SSIs remain unclear. Third, the reason for many deep SSI cases (70%) when only is used is unknown. Finally, our sample size for the C-arm group and the group where both images were used was too small.