Pedicle Screw Fluid Sign: An Indication on Magnetic Resonance Imaging of a Deep Infection After Posterior Spinal Instrumentation

Does local vancomycin powder impregnated with autogenous bone graft and bone substitute decrease the risk of deep surgical site infection in degenerative lumbar spine fusion surgery?—An ambispective study

Background

Deep surgical site infection (DSSI) is one of the most challenging complications in lumbar fusion surgery. Few investigations examined the effect of vancomycin powder mixed with autogenic bone graft (ABG) and bone substitutes on preventing DSSI in degenerative lumbar fusion surgeries as well as any interference with bony fusion. The aim of the study was to investigate the effects of ABG along with bone substitutes as a local vancomycin delivery system on preventing DSSI in lumbar instrumented fusion and compared with those who did not use vancomycin powder.

Methods

From January, 2015 through December, 2015, a one-year prospective study using vancomycin powder mixed with ABG and bone substitute for degenerative lumbar fusion surgeries as vancomycin (V) group, 1 gm vancomycin for 2 and 3-level, and 2 gm for more than 3-level instrumentation. From December, 2013 through December 2014, patients received degenerative lumbar fusion surgeries without using vancomycin before the vancomycin protocol were retrospectively enrolled as non-vancomycin (NV) group. Vancomycin concentration was checked at post-operative days 1 and 3 for both the serum and drainage. Patients’ demographic data, microbiology reports, fusion status and functional outcomes were evaluated.

Results

One hundred and ten patients were enrolled prospectively in the V group, and 86 for the NV group. After an average 41 months follow-up (range, 36–54), 3 patients (3.48%) developed postoperative DSSIs in the NV group, thereby requiring revision surgeries and parenteral antibiotics treatment versus no DSSIs (0%, 0/100) in the V group. (p = 0.048). The postoperative serum vancomycin levels were undetectable and no vancomycin related side effects was encountered. The mean vancomycin concentration of drainage at postoperative days 1 and 3 were 517.96 ± 174.4 and 220.14 ± 102.3 μg/mL, respectively. At final follow-up, there was no statistical difference observed in terms of clinical and radiologic outcomes.

Conclusions

Our vancomycin protocol may reduce the incidence of DSSI in degenerative lumbar fusion surgery without affecting bony fusion.

Level of Evidence

Level III ambispective comparative study.

ACR Appropriateness Criteria® Suspected Spine Infection

Spine infection is both a clinical and diagnostic imaging challenge due to its relatively indolent and nonspecific clinical presentation. The diagnosis of spine infection is based upon a combination of clinical suspicion, imaging evaluation and, when possible, microbiologic confirmation performed from blood cultures or image-guided percutaneous or open spine biopsy. With respect to the imaging evaluation of suspected spine infection, MRI without and with contrast of the affected spine segment is the initial diagnostic test of choice. As noncontrast MRI of the spine is often used in the evaluation of back or neck pain not responding to conservative medical management, it may show findings that are suggestive of infection, hence this procedure may also be considered in the evaluation of suspected spine infection. Nuclear medicine studies, including skeletal scintigraphy, gallium scan, and FDG-PET/CT, may be helpful in equivocal or select cases. Similarly, radiography and CT may be appropriate for assessing overall spinal stability, spine alignment, osseous integrity and, when present, the status of spine instrumentation or spine implants. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Strategies for the Prevention and Treatment of Surgical Site Infection in the Lumbar Spine

Surgical site infection (SSI) following spine surgery can be devastating for both the patient and the surgeon. It leads to significant morbidity and associated health care costs, from readmissions, reoperations, and subsequent poor clinical outcomes. Complications associated with SSI following spine surgery include pseudarthrosis, neurological deterioration, sepsis, and death. Its management can be very challenging. The diagnosis of SSI involves the interpretation of combined clinical, laboratory, and occasionally radiologic findings. Most infections can be treated with an appropriate course of antibiotics and bracing if required. Surgical intervention is usually reserved for infections resistant to medical management, the need for open biopsy/culture, evolving spinal instability or deformity, and neurologic deficit or deterioration. A thorough knowledge of associated risk factors is required and patients should be stratified for risk preoperatively. The multifaceted approach of risk stratification, early diagnosis and effective treatment, is essential for successful prevention and effective treatment and crucial for a satisfactory outcome.

Lymphocyte Count at 4 Days Postoperatively: A Reliable Screening Marker for Surgical Site Infection After Posterior Lumbar Decompression Surgery

STUDY DESIGN

Case-control study.

OBJECTIVE

To identify laboratory markers for surgical site infection (SSI) in posterior lumbar decompression surgery, which are not affected by operative factors, and to determine the diagnostic cutoffs of these markers.

SUMMARY OF BACKGROUND DATA

Numerous laboratory markers are used for the early detection of SSI; however, these markers may be affected by operative factors.

METHODS

The study included 182 participants. They were divided into an SSI group (patients who developed deep SSI; n = 8) and a no-SSI group (n = 174). We reviewed data on the C-reactive protein level and total white blood cell count and differential count before posterior lumbar decompression surgery and 1 and 4 days postoperatively. We determined which markers differed significantly between the groups and identified the markers that were not affected by operative factors (operative time, intraoperative blood loss, and number of operative segments) in the no-SSI group. We then determined the diagnostic cutoffs of these unaffected markers using receiver operating characteristic curves.

RESULTS

We identified the lymphocyte percentage at 4 days postoperatively (cutoff, <19.4%; sensitivity, 80.0%; specificity, 62.5%; area under the curve, 0.78) and lymphocyte count at 4 days postoperatively (cutoff, <1010/μL; sensitivity, 93.7%; specificity, 62.5%; area under the curve, 0.78) as reliable markers.

CONCLUSION

Lymphocyte percentage and count at 4 days postoperatively are reliable markers for SSI after posterior lumbar decompression surgery. Lymphocyte count at 4 days postoperatively can be considered as a superior marker for screening because it has a high sensitivity and can be measured early.

LEVEL OF EVIDENCE

4.

Pedicle screw loosening is correlated to chronic subclinical deep implant infection: a retrospective database analysis

PURPOSE

Spinal fusion is used for treatment of spinal deformities, degeneration, infection, malignancy, and trauma. Reduction of motion enables osseous fusion and permanent stabilization of segments, compromised by loosening of the pedicle screws (PS). Deep implant infection, biomechanical, and chemical mechanisms are suspected reasons for loosening of PS. Study objective was to investigate the frequency and impact of deep implant infection on PS loosening.

METHODS

Intraoperative infection screening from wound and explanted material sonication was performed during revision surgeries following dorsal stabilization. Case history events and factors, which might promote implant infections, were included in this retrospective survey.

RESULTS

110 cases of spinal metal explantation were included. In 29.1% of revision cases, infection screening identified a germ, most commonly Staphylococcus (53.1%) and Propionibacterium (40.6%) genus. Patients screened positive had a significant higher number of previous spinal operations and radiologic loosening of screws. Patients revised for adjacent segment failure had a significantly lower rate of positive infection screening than patients revised for directly implant associated reasons. Removal of implants that revealed positive screening effected significant pain relief.

CONCLUSIONS

Chronic implant infection seems to play a role in PS loosening and ongoing pain, causing revision surgery after spinal fusion. Screw loosening and multiple prior spinal operations should be suspicious for implant infection after spinal fusion when it comes to revision surgery. These slides can be retrieved under Electronic Supplementary Material.

White Blood Cell Count and C-Reactive Protein Variations After Posterior Surgery With Intraoperative Radiotherapy for Spinal Metastasis

STUDY DESIGN

Retrospective case series.

OBJECTIVE

To evaluate the feasibility of blood test parameters [white blood cell (WBC) count and C-reactive protein (CRP)] for predicting and diagnosing postoperative infection after posterior surgery with intraoperative radiotherapy (IORT) for spinal metastasis.

SUMMARY OF BACKGROUND DATA

Posterior surgery with IORT is effective for treating spinal metastasis, as we previously reported. However, the procedure requires that the patient be transferred from the operating room to the irradiation room. In addition, the patient's general status is often poor, and the risk of postoperative infection is high.

MATERIALS AND METHODS

A total of 279 patients who underwent IORT for the treatment of spinal metastasis between August 2004 and June 2013 were included in this study. The WBC count (/10 μL) and CRP level (mg/dL) were recorded in all patients preoperatively and on alternative days for up to 7 days after surgery. We assessed the development of surgical-site infection (SSI) for up to 1 month after surgery.

RESULTS

SSI occurred in 41 patients (14.7%). The preoperative WBC count and CRP level did not differ between the infected and noninfected patients. The WBC counts on postoperative day (POD) 1 and POD 7 and the CRP levels on POD 7 were significantly higher in the infected patients (8.8 vs. 10.0, P=0.04; 6.1 vs. 8.8, P=0.002; 3.89 vs. 9.50, P<0.001). A receiver-operating characteristic curve analysis of the WBC count and CRP level for detecting SSI showed cutoff values of 9.6 (WBC count, POD 1), 6.5 (WBC count, POD 7), and 5.0 (CRP level, POD 7).

CONCLUSIONS

A high WBC count and CRP level on POD 7 may be used to predict or detect SSI. In particular, a CRP level of 5.0 mg/dL on POD 7 strongly suggests the future development of SSI (sensitivity: 78%, specificity: 74%).