Diagnostic Yield of Multidetector Computed Tomography in Patients with Acute Spondylodiscitis

A novel scoring system concept for de novo spinal infection treatment, the Spinal Infection Treatment Evaluation Score (SITE Score): a proof-of-concept study

OBJECTIVE

De novo infections of the spine are an increasing healthcare problem. The decision for nonsurgical or surgical treatment is often made case by case on the basis of physician experience, specialty, or practice affiliation rather than evidence-based medicine. To create a more systematic foundation for surgical assessments of de novo spinal infections, the authors applied a formal validation process toward developing a spinal infection scoring system using principles gained from other spine severity scoring systems like the Spine Instability Neoplastic Score, Thoracolumbar Injury Classification and Severity Score, and AO Spine classification of thoracolumbar injuries. They utilized an expert panel and literature reviews to develop a severity scale called the "Spinal Infection Treatment Evaluation Score" (SITE Score).

METHODS

The authors conducted an evidence-based process of combining literature reviews, extracting key elements from previous scoring systems, and obtaining iterative expert panel input while following a formal Delphi process. The resulting basic SITE scoring system was tested on selected de novo spinal infection cases and serially refined by an international multidisciplinary expert panel. Intra- and interobserver reliabilities were calculated using the intraclass correlation coefficient (ICC) and Fleiss' and Cohen's kappa, respectively. A receiver operating characteristic analysis was performed for cutoff value analysis. The predictive validity was assessed through cross-tabulation analysis.

RESULTS

The conceptual SITE scoring system combines the key variables of neurological symptoms, infection location, radiological variables for instability and impingement of neural elements, pain, and patient comorbidities. Ten patients formed the first cohort of de novo spinal infections, which was used to validate the conceptual scoring system. A second cohort of 30 patients with de novo spinal infections, including the 10 patients from the first cohort, was utilized to validate the SITE Score. Mean scores of 6.73 ± 1.5 and 6.90 ± 3.61 were found in the first and second cohorts, respectively. The ICCs for the total score were 0.989 (95% CI 0.975-0.997, p < 0.01) in the first round of scoring system validation, 0.992 (95% CI 0.981-0.998, p < 0.01) in the second round, and 0.961 (95% CI 0.929-0.980, p < 0.01) in the third round. The mean intraobserver reliability was 0.851 ± 0.089 in the third validation round. The SITE Score yielded a sensitivity of 97.77% ± 3.87% and a specificity of 95.53% ± 3.87% in the last validation round for the panel treatment decision.

CONCLUSIONS

The SITE scoring concept showed statistically meaningful reliability parameters. Hopefully, this effort will provide a foundation for a future evidence-based decision aid for treating de novo spinal infections. The SITE Score showed promising inter- and intraobserver reliability. It could serve as a helpful tool to guide physicians' therapeutic decisions in managing de novo spinal infections and help in comparison studies to better understand disease severity and outcomes.

Spinal disorders mimicking infection

Spinal infections are very commonly encountered by radiologists in their routine clinical practice. In case of typical MRI features, the diagnosis is relatively easy to interpret, all the more so if the clinical and laboratory findings are in agreement with the radiological findings. In many cases, the radiologist is able to make the right diagnosis, thereby avoiding a disco-vertebral biopsy, which is technically challenging and associated with a risk of negative results. However, several diseases mimic similar patterns, such as degenerative changes (Modic) and crystal-induced discopathy. Differentiation between these diagnoses relies on imaging changes in endplate contours as well as in disc signal. This review sought to illustrate the imaging pattern of spinal diseases mimicking an infection and to define characteristic MRI and CT patterns allowing to distinguish between these different disco-vertebral disorders. The contribution of advanced techniques, such as DWI and dual-energy CT (DECT) is also discussed.

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.

Vertebral Bone Marrow and Endplate Assessment on MR Imaging for the Differentiation of Modic Type 1 Endplate Changes and Infectious Spondylodiscitis

On magnetic resonance (MR) imaging, Modic type 1 (MT1) endplate changes and infectious spondylodiscitis share similar findings. Therefore, this study investigated vertebral bone marrow and endplate changes to enable their differentiation. The lumbar spine MR examinations of 91 adult patients were retrospectively included: 39 with MT1; 19 with early spondylodiscitis without abscess; and 33 with advanced spondylodiscitis with abscess. The assessment included percentage of bone marrow edema on sagittal short tau inversion recovery images, and the signal ratio of edema to unaffected bone and endplate contour (normal; irregular, yet intact; blurred; destructive) on sagittal unenhanced T1-weighted images. Differences were tested for statistical significance by Chi-square test and mixed model analysis of variance. The MR diagnostic accuracy in differentiating MT1 and spondylodiscitis was assessed by cross-tabulation and receiver-operating characteristic analysis. The endplate contours, edema extents, and T1-signal ratios of MT1 (extent, 31.96%; ratio, 0.83) were significantly different (p < 0.001) from early spondylodiscitis (56.42%; 0.60), and advanced spondylodiscitis (91.84%; 0.61). The highest diagnostic accuracy (sensitivity, 94.87%; specificity, 94.23%; accuracy, 94.51%) in identifying MT1 was provided by an irregular, yet intact endplate contour. This may be a useful MR feature for the differentiation between MT1 and spondylodiscitis, particularly in its early stage.

Computed tomography imaging characteristics help to differentiate pyogenic spondylitis from brucellar spondylitis

PURPOSE

Both pyogenic spondylitis (PS) and brucellar spondylitis (BS) can cause deformities and permanent neurologic deficits without prompt diagnosis and treatment. However, differential diagnosis is challenging. The aim of this study was to compare the computed tomography (CT) imaging features of PS with those of BS.

METHODS

Thirty-two patients with PS and 44 with BS were enrolled in the study. CT images were obtained in all cases. Data on bone destruction and formation, vertebral wall destruction, and osteosclerotic changes were collected and compared using the Chi-square test or t test. A P value < 0.01 was considered statistically significant. Positive predictive values (PPV) for detecting PS or BS were reported.

RESULTS

Involvement of the lumbar vertebrae and multiple spinal levels was more common in the BS group than in the PS group. Bone destruction was significantly greater in the PS group than in the BS group (30.8 vs 18.0%; t = 3.920, P = 0.000), with more extensive destruction of the vertebral body (35.8 vs 12.5%, χ² = 12.672, P = 0.002, PPV = 63.16%). In the BS group, there was more osteosclerosis around erosions (70.5 vs 43.3%, χ² = 11.59, P = 0.001, PPV = 67.74%) and fan-shaped osteosclerosis (27.3 vs 19.4%, χ² = 18.556, P = 0.006, PPV = 64.86%), more bone formation around the vertebra (77.2 vs 34.3%, χ² = 33.608, P = 0.000, PPV = 76.83%), more bone formation under the anterior longitudinal ligament (63.6 vs 19.4%, χ² = 30.133, P = 0.000, PPV = 76.09%), more longer anterior bone formation (3.55 vs 0.78 mm, t = 3.997, P = 0.000), and more anterior and closed-bone formation with local erosion (42.0 vs 9.0%, χ² = 74.243, P = 0.000, PPV = 74.36%).

CONCLUSIONS

CT images have unique advantages of revealing the morphology of erosions, osteosclerosis, and bone formation around the vertebra and help to differentiate PS from BS. These slides can be retrieved under Electronic Supplementary Material.

[Acute abdomen - a practical approach]

CLINICAL PROBLEM

Acute abdomen describes a critical clinical condition which includes a heterogeneous group of clinical presentations. Several diseases require immediate surgical treatment. Therefore, fast radiological assessment is demanded.

STANDARD RADIOLOGICAL METHODS

Stable patients presenting at the emergency department with acute abdominal pain require an abdominal x‑ray, an ultrasound examination and/or a computed tomography (CT) scan, depending on the location and character of their pain. These standard radiological methods provide a quick differentiation between simple and complicated pathologies. Unstable patients should undergo immediate CT and, if positive, be sent directly to surgery.

METHODICAL INNOVATIONS AND ASSESSMENT

The ongoing technical developments in the field of computed tomography allow a quick and detailed characterization of pathologic conditions of the abdominal organs. A structured approach, based on the analysis of typical radiological signs and patterns, combined with the evaluation of extra-abdominal findings helps to assign the observed imaging findings to specific diseases.

RECOMMENDATION

A systematic 4‑point approach for structured analysis of specific and nonspecific imaging features and common pitfalls aids to choose the correct radiological method and help to narrow the broad spectrum of potential differential diagnoses.

Value of standard radiographs, computed tomography, and magnetic resonance imaging of the lumbar spine in detection of intraoperatively confirmed pedicle screw loosening-a prospective clinical trial

BACKGROUND CONTEXT

Pedicle screw loosening is common after spinal fusion and can be associated with pseudoarthrosis and pain. With suspicion of screw loosening on standard radiographs, CT is currently considered the advanced imaging modality of choice. MRI with new metal artifact reduction techniques holds potential to be sensitive in detection of screw loosening. The sensitivity and specificity of either of the imaging modalities are yet clear.

PURPOSE

To evaluate the sensitivity and specificity of three different image modalities (standard radiographs, CT, and MRI) for detection of pedicle screw loosening.

STUDY DESIGN/SETTING

Cross-sectional diagnostic study.

PATIENT SAMPLE

Forty-one patients (159 pedicle screws) undergoing revision surgeries after lumbar spinal fusion between August 2014 and April 2017 with preoperative radiographs, CT, and MRI with spinal metal artifact reduction (STIR WARP and TSE high bandwidth sequences).

OUTCOME MEASURES

Sensitivity and specificity in detection of screw loosening for each imaging modality.

METHODS

Screw torque force was measured intraoperatively and compared with preoperative screw loosening signs such as peri-screw edema in MRI and peri-screw osteolysis in CT and radiographs. A torque force of less than 60 Ncm was used to define a screw as loosened.

RESULTS

Sensitivity and specificity in detection of screw loosening was 43.9% and 92.1% for MRI, 64.8% and 96.7% for CT, and 54.2% and 83.5% for standard radiographs, respectively.

CONCLUSIONS

Despite improvement of MRI with metal artifact reduction MRI technique, CT remains the modality of choice. Even so, CT fails to detect all loosened pedicle screws.