Can gas and infection coexist in the intervertebral disc? A retrospective analysis of percutaneously biopsied suspected discitis-osteomyelitis cases.

OBJECTIVES: To retrospectively evaluate the correlation between intradiscal gas and infection in patients percutaneously biopsied for suspected discitis-osteomyelitis. MATERIALS AND METHODS: We retrospectively reviewed all CT-guided discitis-osteomyelitis biopsies performed between 2002 and 2022. Two independent trained musculoskeletal radiologists evaluated for presence of gas on CT and/or MRI within 1 week of the biopsy. Disagreements were resolved by a third musculoskeletal radiologist. CT was considered the gold standard for the detection of intradiscal gas. Pathology, microbiology, and imaging and clinical follow-up were used as the gold standard for presence of infection. Interrater agreement on CT and MRI, sensitivity, and positive predictive value were calculated, using the presence of gas as an indicator (test positive) for "no infection." RESULTS: There were 284 biopsies in 275 subjects (mean age 58 ± 1.0 (range 4-99) years; 101 (37%) females and 174 (63%) males). Of the biopsies, 12 (4%) were cervical, 80 (28%) were thoracic, 192 (68%) were lumbar, and 200 (70%) were considered true discitis-osteomyelitis based on pathology, imaging, and clinical follow-up. Interrater agreement was excellent for CT (kappa = 0.83) and poor for MRI (kappa = - 0.021). The presence of gas had a 94% specificity and 76% negative predictive value for the absence of infection. CONCLUSION: CT is the preferred method for detecting intradiscal gas. The presence of gas means that discitis-osteomyelitis is unlikely. If intradiscal gas is present in the setting of discitis-osteomyelitis, the gas bubbles tend to be smaller and fewer in number.

Posterior capsule edema in adhesive capsulitis: comparison with established non-contrast MRI findings and multivariable analysis.

OBJECTIVES: To evaluate posterior glenohumeral capsule edema compared to other MRI findings in adhesive capsulitis (AC). METHODS: This study was approved by the local Institutional Review Board and it is HIPAA compliant. A retrospective search identified subjects who received fluoroscopically guided intra-articular corticosteroid injections for AC and had an MRI within 6 months prior to injection. The study group was compared with an age-, sex-, and side-matched control group who underwent the same procedures but did not have AC. MRIs were evaluated for edema of posterior capsule, anterior capsule, axillary pouch, coracohumeral ligament (CHL) and rotator interval (RI), thickness of axillary pouch and CHL, thickness of anterior capsule, RI and subcoracoid fat replacement, and teres minor atrophy and edema. Multivariable analysis was performed. RESULTS: A total of 57 subjects with AC and 57 matched controls were studied: mean age 52 ± 7 (range 31-71) years, 37 female and 20 male, 22 right and 35 left. Posterior capsule edema was more common in the AC group vs. control group (66.7 vs 17.5%, p < 0.001). Multivariable analysis showed posterior capsule edema, CHL edema, and axillary pouch (glenoid) thickness (optimum cutoff = 4 mm) were significant independent predictors of AC. Simplified analysis using these three variables had an area under the curve of 0.860 (95%CI: 0.792-0.928). With all three variables present, the sensitivity and specificity for AC were 32% and 98%, respectively. CONCLUSIONS: Posterior joint capsule edema may be helpful to confirm AC. Posterior capsule edema, CHL edema, and axillary pouch (glenoid) thickness produce a strong model for distinguishing AC from controls. CLINICAL RELEVANCE STATEMENT: Edema involving the posterior shoulder joint capsule is an imaging marker of capsulitis and is useful in differentiating patients with adhesive capsulitis from those without in conjunction with other proven MRI findings. KEY POINTS: • Posterior capsule edema has a sensitivity of 66.7% and a specificity of 82.5% for the detection of adhesive capsulitis. • Posterior capsule edema, coracohumeral ligament (CHL) edema, and axillary pouch (glenoid) thickness were significant independent predictors of adhesive capsulitis, and combining these variables together produces a very strong model for distinguishing cases from controls (AUC = 0.860). • Optimal cutoff values for CHL, axillary pouch (humeral), axillary pouch (glenoid), and axillary pouch (total) thickness were 2.5, 2.6, 4, and 6.3 mm, respectively.

A novel core biopsy needle with shorter dead space for percutaneous image-guided musculoskeletal biopsies - how does it compare with an established core biopsy needle?

PURPOSE: To compare diagnostic yield and utility of a novel core biopsy needle (NCBN) with shortened tip dead space for percutaneous musculoskeletal biopsies with an established core biopsy needle (ECBN). METHODS: This study was IRB approved and HIPAA compliant. All percutaneous biopsies using an NCBN performed between July 2020 and August 2021 were retrospectively reviewed. Data on patient demographics, biopsy technique, biopsy needle, and histopathology were collated. RESULTS: Thirty-six patients were included in this study, 16 (44%) undergoing biopsy with both an NCBN and an ECBN, and 20 (56%) with an NCBN only. All 36 NCBN biopsies were 16 gauge. Fifteen (94%) of the ECBN biopsies were 14 gauge, and 1 (6%) was 16 gauge. Thirty-four (94%) of the NCBN and 15 (94%) of the ECBN biopsies were diagnostic. No adverse events were identified. CONCLUSION: Both the NCBN and ECBN have high diagnostic rates. No adverse events were identified. NCBN could be considered for biopsy of lesions limited by anatomic location or near adjacent critical structures.

Prevalence of Paget's disease of bone: review of consecutive abdominopelvic CT scans and literature.

BACKGROUND: Previous studies suggest an overall decrease of Paget's disease of bone (PDB) prevalence. However, a large number of asymptomatic patients make previously reported prevalence likely underrepresented. PURPOSE: To evaluate the prevalence of PDB in our patient population. MATERIAL AND METHODS: We retrospectively identified 1295 (mean age = 59 years; age range = 18-98 years) consecutive abdominopelvic computed tomography (CT) scans over a 15-day period in 2014. Abdominopelvic CT images were reviewed to assess for the presence of PDB in the lower thoracic spine, lumbar spine, pelvis, or proximal femora. This prevalence was compared with prevalence reported in earlier literature using Fisher's exact test. RESULTS: Of the included patients, 5/1295 (0.39%) patients had imaging findings of PDB on abdominopelvic CT. Those five patients were all aged ≥55 years and had pelvic bone involvement, with one patient having additional involvement of multiple lower thoracic vertebral bodies. In our studied cohort, 812/1295 (62.7%) patients were aged ≥55 years, which corresponds to a prevalence of 0.62% (5/812) of PDB in patients aged ≥55 years. When accounting for fact that bones of the pelvis are involved in 40%-91% of patients with PDB, the prevalence is estimated at 0.43%-0.98% in the total adult population and estimated at 0.68%-1.55% in older adults. The prevalence was greater than two studies before 1960, and less than some studies during 1960-2019. CONCLUSION: We found that the prevalence of PDB on abdominopelvic CTs was 0.39% of all adult patients with an increase after the age of 55 years.

Discitis-osteomyelitis: optimizing results of percutaneous sampling.

Vertebral discitis-osteomyelitis is an infection of the spine that involves the intervertebral disc and the adjacent vertebral body but may also extend into the paraspinal and epidural soft tissues. If blood cultures and other culture data fail to identify a causative microorganism, percutaneous sampling is indicated to help guide targeted antimicrobial therapy. Despite limited supporting evidence, withholding antimicrobial therapy for up to 2 weeks is recommended to maximize microbiological yield, although literature supporting this recommendation is limited. During the procedure, technical factors that may improve yield include targeting of paraspinal fluid collections or soft tissue abnormalities for sampling, acquiring multiple core samples if possible, and use of larger gauge needles when available. Repeat sampling may be indicated if initial percutaneous biopsy is negative but should be performed no sooner than 72 h after the initial percutaneous biopsy to ensure adequate time for culture results to return.

Lisfranc injury: Refined diagnostic methodology using weightbearing and non-weightbearing radiographs.

BACKGROUND: To compare diagnostic parameters for Lisfranc instability on WB and NWB radiographs and to assess the inter-observer reliability of a standardized diagnostic protocol. PATIENTS AND METHODS: Patients who had undergone surgical treatment for subtle, purely ligamentous Lisfranc injury with both WB and NWB post-injury, pre-surgery films (n = 26) were included in this multicentre, retrospective comparative study. Also included was a control group (n = 26) of patients with isolated fifth metatarsal avulsion fractures who similarly had both WB and NWB films. Multiple midfoot distance and alignment measurements were used to evaluate the Lisfranc joint on both WB and NWB views. To evaluate interobserver reliability, measurements were made by two independent observers across a cohort subset. RESULTS: When comparing the NWB views between groups, only C1M2 (medial cuneiform- second metatarsal) distance was found to be significantly larger (∆ = 1.35 mm, p <0.001) for Lisfranc injuries. Most notably, C2M2 (Intermediate cuneiform - second metatarsal) step off-caused by lateral translation of the second metatarsal base-was not significantly different (∆ = 0.39 mm, p = 0.101) between Lisfranc patients and controls. On WB views, Lisfranc patients had significantly larger changes to C1M2 distance and C2M2 step-off as compared to controls (∆ = 2.97 mm, p <0.001 and ∆ =  1.98 mm, p <0.001 respectively). M1M2 (first to second intermetatarsal) distance was not significantly different between patients and controls in WB films. Within the cohort of ligamentous Lisfranc patients, C1M2 distance and C2M2 step-off were significantly larger in WB when compared to NWB films (∆ =  1.77 mm, p <0.001 and ∆ =  1.58 mm, p <0.001 respectively). For these parameters, inter-observer reliability scores (ICC) of >0. 90 were found when interpreting WB radiographs and ICC's ranging between 0.61 and 0.80 were found when interpreting NWB radiographs. CONCLUSION: Using WB imaging for diagnosing subtle Lisfranc instability reveals larger diastasis in the tarsometatarsal joint and has a higher interobserver reliability compared to NWB imaging. Clinical concern for subtle or occult Lisfranc instability in any patient should therefore trigger WB radiographic assessment since such injuries may be missed on NWB views.

Contribution of positron emission tomography/magnetic resonance imaging in musculoskeletal malignancies.

Positron emission tomography/computed tomography (PET/CT) is a promising hybrid imaging technique for evaluating musculoskeletal malignancies. Both technologies, independently are useful for evaluating this type of tumors. PET/MR has great potential combining metabolic and functional imaging PET with soft tissue contrast and multiparametric sequences of MR. In this paper we review the existing literature and discuss the different protocols, new available radiotracers to conclude with the scarce evidence available the most useful/probable indications of the PET MR for the for musculoskeletal malignancies.

Observer agreement in the choice of lumbar spine injection for pain management.

BACKGROUND AND PURPOSE: Lumbar spine MRI can help guide the choice of corticosteroid injection in pain management. We investigated whether patient-reported symptom information from a questionnaire could improve agreement in the choice of type, level, and side of injection. MATERIALS AND METHODS: In this prospective observational study, 120 patients (median age 64, 70 men) were recruited from patients referred for pain management. After informed consent, they completed electronic questionnaires that obtained symptom information for later use during MRI reviews. In 3 research arms, 6 radiologists chose injections that would ideally deliver corticosteroid to the presumed sources of pain in (1) MRI studies reviewed with symptom information from questionnaires, (2) MRI studies reviewed without symptom information, and (3) MRI reports. Blinded to questionnaire results, radiologists providing clinical care and interviewing patients chose ideal therapeutic injections to establish reference standards. Injections were categorized by type, level, and side and compared using percent agreement and kappa statistics. Interreading agreement was analyzed. RESULTS: Compared to the reference standard, kappa agreements for injection types, levels, and sides were almost perfect when MRIs were reviewed knowing symptoms (0.85-0.93), fair without symptoms (0.23-0.35) (all P < .001) and fair in MRI reports (0.24-0.36) (all P < .001). Interreading kappa agreements were almost perfect knowing symptoms (0.82-0.90), but only moderate without symptoms (0.42-0.49) (all P < .001). CONCLUSIONS: Radiologists reviewing lumbar spine MRI converged on the type, level, and side of ideal therapeutic injection whether they obtained symptom information from direct patient interview or electronic questionnaire. Observer agreement was significantly lower without symptom information.

An international expert opinion statement on the utility of PET/MR for imaging of skeletal metastases.

BACKGROUND: MR is an important imaging modality for evaluating musculoskeletal malignancies owing to its high soft tissue contrast and its ability to acquire multiparametric information. PET provides quantitative molecular and physiologic information and is a critical tool in the diagnosis and staging of several malignancies. PET/MR, which can take advantage of its constituent modalities, is uniquely suited for evaluating skeletal metastases. We reviewed the current evidence of PET/MR in assessing for skeletal metastases and provided recommendations for its use. METHODS: We searched for the peer reviewed literature related to the usage of PET/MR in the settings of osseous metastases. In addition, expert opinions, practices, and protocols of major research institutions performing research on PET/MR of skeletal metastases were considered. RESULTS: Peer-reviewed published literature was included. Nuclear medicine and radiology experts, including those from 13 major PET/MR centers, shared the gained expertise on PET/MR use for evaluating skeletal metastases and contributed to a consensus expert opinion statement. [18F]-FDG and non [18F]-FDG PET/MR may provide key advantages over PET/CT in the evaluation for osseous metastases in several primary malignancies. CONCLUSION: PET/MR should be considered for staging of malignancies where there is a high likelihood of osseous metastatic disease based on the characteristics of the primary malignancy, hight clinical suspicious and in case, where the presence of osseous metastases will have an impact on patient management. Appropriate choice of tumor-specific radiopharmaceuticals, as well as stringent adherence to PET and MR protocols, should be employed.

Impact of Patient-Reported Symptom Information on Agreement in the MRI Diagnosis of Presumptive Lumbar Spine Pain Generator.

BACKGROUND. Lumbar spine MRI is associated with a high prevalence of interpretive errors by radiologists. Treating physicians can obtain symptom information, correlate symptoms with MRI findings, and distinguish presumptive pain generators from incidental abnormalities. OBJECTIVE. The purpose of this study was to capture symptom information using a patient questionnaire, review lumbar spine MRI examinations with and without symptom information, diagnose pain generators, and compare MRI diagnoses with clinical reference diagnoses. METHODS. In this prospective study, 120 participants (70 men and 50 women; median age, 64 years; interquartile range, 49.5-74 years) were recruited from patients referred for lumbar spine injections between February and June 2019. Participants completed electronic questionnaires regarding their symptoms before receiving the injections. For three research arms, six radiologists diagnosed pain generators in MRI studies reviewed with symptom information from questionnaires, MRI studies reviewed without symptom information, and MRI reports. Interreading agreement was analyzed. Blinded to the questionnaire results, the radiologists who performed injections obtained patient histories, correlated symptoms with MRI findings, and diagnosed presumptive pain generators. These diagnoses served as clinical reference standards. Pain generators were categorized by type, level, and side and were compared using kappa statistics. Diagnostic certainty was recorded using numeric values (0-100) and was compared using Wilcoxon rank-sum test RESULTS. When compared with the reference standard, agreement for the type, level, and side of pain generator was almost perfect in MRI examinations reviewed with symptom information (κ = 0.82-0.90), fair to moderate in MRI examinations reviewed without symptom information (κ = 0.28-0.51) (all p < .001), and fair to moderate in MRI reports (κ = 0.27-0.45) (all p < .001). Interreading agreement was almost perfect when MRI examinations were reviewed with symptom information (κ = 0.82-0.90) but was only moderate without symptom information (κ = 0.42-0.56) (all p < .001). Diagnostic certainty levels were highest for radiologists performing injections (mean [± SD], 90.0 ± 9.9) and were significantly higher for MRI review with symptom information versus without symptom information (means for reading 1, 84.6 ± 13.1 vs 62.9 ± 20.7; p < .001). CONCLUSION. In lumbar spine MRI, presumptive pain generators diagnosed using symptom information from electronic questionnaires showed almost perfect agreement with pain generators diagnosed using symptom information from direct patient interviews. CLINICAL IMPACT. Patient-reported symptom information from a brief questionnaire can be correlated with MRI findings to distinguish presumptive pain generators from incidental abnormalities.

Symptomatic COVID-19 infections in outpatient image-guided corticosteroid injection patients during the lockdown phase.

BACKGROUND: Musculoskeletal pain is a debilitating problem treated with image-guided corticosteroid injections. During the COVID-19 pandemic, multiple societies issued caution statements because of the unknown effect of corticosteroids on the patient's immune system. The purpose is to determine if image-guided corticosteroid injections administered during the COVID-19 lockdown phase were associated with a higher infection rate compared to the general population. MATERIALS AND METHODS: In a prospective study, patients undergoing image-guided corticosteroid injections for pain management during the lockdown phase between April 15 and May 22, 2020, were enrolled. One month after the injection, patients were surveyed by telephone for any COVID-19-related symptoms, and the electronic medical record (EMR) was reviewed for symptoms and test results. RESULTS: Seventy-one subjects were recruited, 31 (44%) females, 40 (56%) males, ages 58 ± 17 (20-92) years. Follow-up was available in 66 (93%) of subjects, 60 (91%) by phone survey and EMR, 6 (9%) by EMR only, 45 ± 22 (19-83) days after injection. One (1/66, 1.52%; 95% CI 0.04-8.2%) 25-year-old male subject developed symptomatic infection 19 days after a tibiotalar injection. The prevalence of COVID-19 cases in the state of Massachusetts was 0.91% (62,726/6,892,503) during the study period. There was no significant difference in the rate of occurrence of new cases of COVID-19 infection between the corticosteroid injection group and the general population (p = 0.44). CONCLUSION: Image-guided corticosteroid injections for pain management performed during the lockdown phase of the COVID-19 pandemic were not associated with a higher infection rate compared to the general population.

Best Practices: CT-Guided Percutaneous Sampling of Vertebral Discitis-Osteomyelitis and Technical Factors Maximizing Biopsy Yield.

Vertebral discitis-osteomyelitis is an infection of the intervertebral disk and vertebral bodies that may extend to adjacent paraspinal and epidural soft tissues. Its incidence is increasing, likely because of improved treatments and increased life expectancy for patients with predisposing chronic disease and increased rates of IV drug use and intravascular intervention. Because blood cultures are frequently negative in patients with vertebral discitis-osteomyelitis, biopsy is often indicated to identify a causative microorganism for targeted antimicrobial therapy. The reported yield of CT-guided percutaneous sampling is 31-91%, which is lower than the reported yield of open biopsy of 76-91%. However, the less invasive approach may be favored given its relative safety and low cost. If paravertebral fluid collections are present, CT-guided aspiration should be performed. If aspiration is unsuccessful or no paravertebral fluid collections are present, CT-guided percutaneous biopsy should be performed, considering technical factors (e.g., anatomic approach, needle selection, and needle angulation) that may improve microbiologic yield. Although antimicrobial therapy should be withheld for 1-2 weeks before biopsy if clinically feasible, biopsy may still be performed without stopping antimicrobial therapy if needed. Because of the importance of targeted antimicrobial therapy, repeat biopsy should be considered after 72 hours if initial biopsy does not identify a pathogen.

Hip abductor tears in ischiofemoral impingement.

PURPOSE: Ischiofemoral impingement (IFI) is associated with abnormalities of the quadratus femoris muscle and narrowing of the ischiofemoral (IF) and quadratus femoris (QF) spaces. The hip abductors play an important role in pelvic stability and abductor tears might play a role in the pathophysiology of IFI. The purpose of our study was to assess the association between hip abductor tears and IFI on MRI. MATERIALS AND METHODS: The study was IRB approved and HIPAA compliant. Inclusion criteria were MRI findings of IFI (narrowing of the IF space ≤ 15 mm or QF space ≤ 10 mm with associated ipsilateral quadratus femoris edema or fatty infiltration/atrophy). Two MSK radiologists assessed hip/pelvic MRIs and integrity of the tensor fascia lata, gluteus medius, and minimus tendons. IFI and control groups were compared with a two-tailed Student t test or chi-squared test. RESULTS: We identified 140 patients with MRI findings of IFI (mean age 56 ± 13 years, 130 f, 10 m) and 140 controls of similar age and sex. Patients with IFI had a higher prevalence of gluteus medius/minimus partial tears (37 vs 21, p = 0.02) and full-thickness tears (24 vs 21, p = 0.03). Patients with IFI had a higher prevalence and higher grade of gluteal muscle atrophy compared with controls (p < 0.03). There were no tears of the tensor fascia lata in either group. CONCLUSION: Patients with IFI had a higher prevalence of abductor tears and abductor muscle atrophy compared with matched controls. This suggests that abductor tears might play a role in the pathophysiology of IFI.

CT-guided discitis-osteomyelitis biopsies: needle gauge and microbiology results.

PURPOSE: To compare the microbiology results and needle gauge for CT-guided biopsies of suspected discitis-osteomyelitis. METHODS: All CT-guided biopsies performed for suspected discitis-osteomyelitis at our institution between 2002 and 2019 were reviewed. Biopsy location, needle type and gauge, microbiology, pathology, and clinical and imaging follow-up were obtained through chart review. Yield, sensitivity, specificity, and accuracy were calculated. A pairwise analysis of different needle gauges was also performed with calculations of odds ratios. Naïve Bayes predictive modeling was performed. RESULTS: 241 (age: 59 ± 18 years; 88 [35%] F, 162 [65%] M) biopsies were performed. There were 3 (1%) 11 gauge (G), and 13 (5%) 12-G biopsies; 23 (10%) 13-G biopsies; 75 (31%) 14-G biopsies; and 90 (37%) 16-G, 33 (14%) 18-G, and 4 (2%) 20 G biopsies. True disease status (presence of infection) was determined via either pathology findings (205, 86%) or clinical and imaging follow-up (36, 14%). The most common true positive pathogen was Staphylococcus aureus (31, 33%). Overall biopsy yield, sensitivity, specificity, and accuracy were 39%, 56%, 89%, and 66%, respectively. Pooled biopsy yield, sensitivity, specificity, and accuracy was 56%, 69%, 71%, and 69% for 11-13-G needles and 36%, 53%, 91%, and 65% for 14-20-G needles, respectively, with an odds ratio between the two groups of 2.29 (P = 0.021). Pooled biopsy yield, sensitivity, specificity, and accuracy was 48%, 63%, 85%, and 68% for 11-14-G needles and 32%, 49%, 91%, and 64% for 16-20-G needles, respectively, with an odds ratio between the two groups of 2.02 (P = 0.0086). CONCLUSION: The use of a larger inner bore diameter/lower gauge biopsy needle may increase the likelihood of culturing the causative microorganism for CT-guided biopsies of discitis-osteomyelitis.

Capsular Injury and Inflammation.

The capsular and ligamentous structures of the glenohumeral joint are important for stability of the shoulder. These structures are best evaluated by MR imaging. Familiarity with normal and abnormal appearance of the capsular structures of the shoulder is important to ensure that important pathology is not overlooked. Injury to the capsular structures can occur in the setting of trauma and most commonly involves the inferior glenohumeral ligament and axillary pouch. Adhesive capsulitis is a common inflammatory condition with characteristic imaging features that should be considered in the absence of alternative diagnoses.

Fluoroscopically guided lumbar spine interlaminar and transforaminal epidural injections: inadvertent intravascular injection.

BACKGROUND: Inadvertent intravascular injection is a rare but catastrophic complication of lumbar epidural injections. PURPOSE: To determine risk factors for inadvertent intravascular injection in fluoroscopically guided lumbar spine epidural injections. MATERIAL AND METHODS: A total of 212 patients who presented for lumbar interlaminar or transforaminal injection were prospectively enrolled. Patient demographics, history of surgery, injection side, site and approach, and volume of contrast injected were recorded. RESULTS: There were 89 (42%) interlaminar and 123 (58%) transforaminal injections. For 36 (17%) patients, there had been surgery at the injected or adjacent lumbar level. There were 25 (12%) inadvertent intravascular injections, with an incidence of 2/93 (2%) for interlaminar and 23/119 (19%) for transforaminal injections. The patients with inadvertent intravascular injection were older (P = 0.017) and had prior surgery at or adjacent to the level of injection (P < 0.0001). Transforaminal approach had a higher intravasation rate than interlaminar injections, both when comparing the entire cohort (P = 0.0001) and only patients without prior surgery (P = 0.01). In multivariable logistic regression analysis, transforaminal injections (odds ratio [OR] 9.77, 95% confidence interval [CI] 2.14-44.6, P = 0.003) and prior surgery at or adjacent to the level of injection (OR 5.71, 95% CI 2.15-15.15, P < 0.001) were independently associated with increased risk of inadvertent intravascular injections. CONCLUSION: Inadvertent intravascular injection occurred in 12% of our lumbar injection cohort and is more common with transforaminal injections, in older patients, and with prior lumbar surgery at or adjacent to the level of injection.

MRI and clinical features of acute fungal discitis/osteomyelitis.

OBJECTIVES: To compare imaging and clinical features of fungal and Staphylococcus aureus discitis-osteomyelitis (DO) for patients presenting for CT-guided biopsies. METHODS: Our study was IRB-approved and HIPAA-compliant. A group of 11 fungal DO (FG) with MRI within 7 days of the biopsy and a control group (CG) of 19 Staphylococcus aureus DO were evaluated. Imaging findings (focal vs diffuse paravertebral soft tissue abnormality, partial vs complete involvement of the disc/endplate), biopsy location, pathology, duration of back pain, immune status, history of intravenous drug, history of prior infection, current antibiotic treatment, and history of invasive intervention. Differences were assessed using the Fisher exact test and Kruskal-Wallis test. Naïve Bayes predictive modeling was performed. RESULTS: The most common fungal organisms were Candida species (9/11, 82%). The FG was more likely to have focal soft tissue abnormality (p = 0.040) and partial disc/endplate involvement (p = 0.053). The clinical predictors for fungal DO, in order of importance, back pain for 10 or more weeks, current antibiotic use for 1 week or more, and current intravenous drug use. History of invasive instrumentation within 1 year was more predictive of Staphylococcus aureus DO. CONCLUSION: MRI features (focal partial soft tissue abnormality and partial involvement of the disc/endplate) in combination with clinical features may help to predict fungal species as a causative organism for DO. KEY POINTS: • MRI features of discitis-osteomyelitis (focal partial soft tissue abnormality and partial involvement of the disc/endplate) in combination with clinical features may help to predict fungal species as a causative organism for DO.

Does MR arthrography cause intracranial gadolinium deposition?

PURPOSE: To determine (i) whether intra-articular gadolinium from MR arthrography (MRA) results in gadolinium deposition in the brain and (ii) whether there is a correlation between intra-articular gadolinium dose and intracranial gadolinium deposition. MATERIALS AND METHODS: This retrospective study was institutional review board (IRB) approved and HIPAA compliant. The study group included consecutive adult patients who had undergone MRA of the hip or shoulder and subsequent MRI of the brain. None of the patients had a history of intravenous gadolinium exposure. A control group of patients of similar age and sex who were never exposed to gadolinium and had brain MRIs available was included. Signal intensities (SI) of four brain regions: pons, dentate nuclei (DN), globus pallidi (GP), and thalamus (Thal) normalized to cerebrospinal fluid (CSF) and expressed in SI ratios were measured on T1-weighted non-contrast MR images. Groups were compared using the student's t test. Linear correlation analysis of gadolinium dose and brain SI ratios was performed, and Pearson correlation coefficients (r) are reported. RESULTS: We identified 109 patients (mean age 44 ± 14 years, 54% men) who had undergone MRA and 149 controls of similar age and sex distribution. There was no significant difference in mean SI ratios of the brain regions between patients and controls: pons/CSF (p = 0.7), DN/CSF (p = 0.4), GP/CSF (p > 0.99), Thal/CSF (p = 0.3). Within the MRA group, gadolinium dose was not associated with SI ratios (p > 0.2). CONCLUSION: Our study found no MR evidence of intracranial gadolinium deposition following MRA. In addition, there was no association between intra-articular gadolinium dose and SI ratios in commonly affected regions of the brain.

Value of response to anesthetic injection during hip MR arthrography to differentiate between intra- and extra-articular pathology.

PURPOSE: To determine the value of anesthetic injection during hip MR arthrography (anesthetic MRA) to differentiate between intra- and extra-articular pathology in patients with hip pain. MATERIALS AND METHODS: This retrospective study was IRB-approved and HIPAA-compliant. We included 75 consecutive adult patients (46 women, mean age 38 ± 13 years) who were referred for MRA. All patients underwent a focused hip examination including active flexion, passive flexion, and passive flexion with internal and external rotation, immediately prior to injection. Anesthetic MRA was performed following fluoroscopically guided intra-articular injection of contrast mixed with anesthetic. Following the injection, the hip examination was repeated, and the pain response was recorded. Clinical records, including response to corticosteroid injections, physical therapy notes, and operative reports were reviewed for verification of intra- and extra-articular pathology as the source of hip pain (gold standard). The positive (PPV) and negative predictive values (NPP) of anesthetic MRA to differentiate between intra- and extra-articular pathology were calculated. RESULTS: On MRI, 41 patients had only intra-articular and 5 patients only extra-articular pathology, while 29 patients had both, intra- and extra-articular pathology. Forty-three patients had pain relief and 32 patients had no pain relief after anesthetic injection. PPV of anesthetic MRA to detect intra-articular pathology was 91% and NPV was 67%. CONCLUSION: Anesthetic MRA can be used as an adjunct to define the origin of hip pain. A positive response suggests intra-articular pathology which can be helpful to localize the source of pain in equivocal cases where both intra- and extra-articular pathology are evident on MRI.

CT-guided discitis-osteomyelitis biopsies with negative microbiology: how many days should we wait before repeating the biopsy?

PURPOSE: To determine the number of days to positive CT-guided biopsy sample culture in patients with discitis-osteomyelitis. METHODS: Our study was IRB approved and HIPAA compliant. All CT-guided biopsies performed for acute discitis-osteomyelitis with positive microbiology between 2002 and 2018 were reviewed. Microbiological organism and days to positive biopsy were documented. Mean, median, skew, and standard deviation were calculated. The proportion of positive cultures that become positive after each day has elapsed was also calculated. RESULTS: There were 96 true positive cultures, with 64 (67%) male and 32 (33%) female, ages 57 ± 18 (range 19-87) years. Overall, including all culture results, the mean number of days to positive culture was 2.9 ± 3.5 days. The median number of days was 2, with a positive skew of 2.9. At days 1, 2, 3, 4, and 5, 48%, 68%, 78%, 85%, and 89%, respectively, of biopsy samples had a positive microbiology culture. CONCLUSION: Approximately three-quarters of discitis-osteomyelitis pathogens will be identified by biopsy sample culture by 3 days after CT-guided biopsy. This finding should be considered if planning for a repeat biopsy in the setting of a negative microbiology culture.