Local and Systemic Side Effects of Corticosteroid Injections for Musculoskeletal Indications.

Corticosteroid injections can be associated with a range of potential side effects, which may be classified as local or systemic and further stratified as immediate or delayed in onset. Radiologists performing image-guided musculoskeletal injections should recognize the potential side effects of corticosteroid medication when counseling patients before injection and consider such side effects in planning individual injections. This Review summarizes the available evidence regarding the local and systemic side effects of corticosteroid injections performed for musculoskeletal indications. Local side effects include postinjection flare, skin hypopigmentation and atrophy, infection, tendon rupture, accelerated progression of osteoarthritis, and osseous injury. Systemic side effects include adrenal suppression or insufficiency, facial flushing, hypertension, hyperglycemia, and osteoporosis. Additional targeted counseling is warranted regarding side effects that are specific to certain patient populations (i.e., premenopausal women, patients with diabetes, athletes, and pediatric patients). Corticosteroid injections are contraindicated in the presence of superficial or deep infection, fracture, or a prosthetic joint. Guidelines on the frequency, duration, and maximal lifetime use of corticosteroid injections are currently lacking. Further research is needed regarding the long-term complications of continuous corticosteroid use, particularly with regard to osseous effects.

Comparison of MRI and arthroscopy findings for transitional zone cartilage damage in the acetabulum of the hip joint.

OBJECTIVE: To assess the performance of morphologic and hypointense signal changes on MRI to predict grades and types of acetabular cartilage damage in the chondrolabral transitional zone (TZ) of the hip identified at arthroscopy. MATERIALS AND METHODS: This retrospective single-center study reviewed conventional 3T MRI hip studies from individuals with symptomatic femoroacetabular impingement (FAI) and subsequent hip arthroscopy surgery within 6 months. Independent review was made by three radiologists for the presence of morphologic damage or a hypointense signal lesion in the TZ on MRI. Fleiss' kappa statistic was used to assess inter-reader agreement. The degree of TZ surfacing damage (modified Outerbridge grades 1-4) and presence of non-surfacing wave sign at arthroscopic surgery were collected. Relationship between sensitivity and lesion grade was examined. RESULTS: One hundred thirty-six MRI hip studies from 40 males and 74 females were included (mean age 28.5 years, age range 13-54 years). MRI morphologic lesions had a sensitivity of 64.9-71.6% and specificity of 48.4-67.7% for arthroscopic surfacing lesions, with greater sensitivity seen for higher grade lesions. Low sensitivity was seen for wave sign lesions (34.5-51.7%). MRI hypointense signal lesions had a sensitivity of 26.3-62% and specificity of 43.8-78.0% for any lesion. Inter-reader agreement was moderate for morphologic lesions (k = 0.601) and poor for hypointense signal lesions (k = 0.097). CONCLUSION: Morphologic cartilage damage in the TZ on MRI had moderate sensitivity for any cartilage lesion, better sensitivity for higher grade lesions, and poor sensitivity for wave sign lesions. The diagnostic value of hypointense signal lesions was uncertain.

Ultrasound-guided nerve block prior to biopsy of suspected neurogenic tumors: safety and feasibility in a pilot study.

OBJECTIVE: The aim of this study is to investigate the safety and feasibility of ultrasound-guided nerve block prior to biopsy of potentially neurogenic tumors. MATERIALS AND METHODS: A retrospective review of the medical record from June 2017 to June 2022 identified ultrasound-guided biopsies of potentially neurogenic tumors that were performed with a pre-procedural nerve block. Patient demographics, biopsy site, number of passes, needle gauge, use of sedation, pathology results, and procedural complications were recorded and summarized. RESULTS: The structured search found 16 patients that underwent biopsies of 18 potentially neurogenic tumors with the use of a pre-procedural nerve block at a variety of upper and lower extremity locations. Average patient age was 52 (range 18-78) and 9 patients (56%) were female. Of the 16 patients, 10 were performed without intravenous sedation. Three patients were unable to tolerate biopsy until a nerve block was used. All biopsies yielded a diagnostic sample with 13 of the tumors neurogenic in origin. One patient reported mild postprocedural pain which resolved with conservative treatment; no other complications were reported. CONCLUSION: Nerve block prior to ultrasound-guided biopsy of potentially neurogenic tumors is a safe and feasible technique. Further study is needed to determine the extent to which nerve block can decrease intra-procedural pain and reduce or eliminate the need for sedation during biopsy.

Detection of pediatric musculoskeletal pathology using the fluid-sensitive sequence.

BACKGROUND: Musculoskeletal complaints are common among children, and magnetic resonance (MR) is increasingly used to supplement the clinical assessment. The validation of a short triage protocol could reduce the number of unnecessary contrast-enhanced MR studies that sometimes also require the need for sedation. OBJECTIVE: To compare the diagnostic accuracy between fluid-sensitive sequence and contrast-enhanced MR study in the detection of musculoskeletal pathology in the pelvis and the appendicular skeleton in children older than 2 years. MATERIALS AND METHODS: We performed a retrospective review between Feb. 1, 2016, and Oct. 31, 2016, and identified 99 studies from 96 patients (48 boys and 48 girls; mean age ± standard deviation, 11.1±4.6 years) without syndromic deformity, recent trauma, a history of infectious or inflammatory arthropathy, prior instrumentation or incomplete records. Two radiologists reviewed each study twice, at least 1 month apart, first using only the fluid-sensitive sequences (triage study) and later using the contrast-enhanced study. Readers rated the presence or absence of pathology independently and generated final impressions in consensus. We used Cohen's kappa (κ) and percentage agreement to compare agreement between readers and between studies, respectively. RESULTS: Inter-reader agreement was overall higher for the contrast-enhanced studies (κ range = 0.91-1) than for the triage studies (κ range = 0.49-1). Percentage agreement between studies was high for the detection of pathology (97-100%) and for the impressions (93%). Clinical diagnoses were stress reaction or overuse in 31%, infection in 21%, space-occupying process in 17%, normal in 15%, inflammatory in 14%, and both inflammatory and overuse in 1%. The full study increased diagnostic confidence in five studies and accuracy in two but did not alter management. CONCLUSION: The fluid-sensitive sequence had a near-perfect percentage of agreement with the contrast-enhanced study in the detection of musculoskeletal pathology and could possibly be used to screen children who need a contrast-enhanced MR study.

Imaging of Kingella kingae musculoskeletal infections in children: a series of 5 cases.

PURPOSE: Kingella kingae musculoskeletal infections continue to be under-diagnosed and there remains a paucity of literature on its imaging features. The purpose of this manuscript is to review the imaging, clinical, and laboratory findings of microbiology-proven K. kingae infections. MATERIALS AND METHODS: A retrospective review of musculoskeletal infections between January 1, 2013 and Dec 31, 2016 yielded 134 patients from whom 5 patients had confirmed K. kingae infections (3 boys and 2 girls, mean age of 16 months, range 9-38 months). Picture archiving and communication system and electronic medical records were reviewed. RESULTS: At presentation, none of the patients had a fever and not all patients had abnormal inflammatory markers. Three patients had septic arthritis (2 knee and 1 sternomanubrial joints), one had epiphyseal osteomyelitis, and one had lumbar spondylodiscitis. The case of epiphyseal osteomyelitis of the distal humerus also had elbow joint involvement. A combination of radiography (n = 4), ultrasound (n = 2), and magnetic resonance (MR) imaging (n = 5) were performed. Prominent synovial thickening was observed for both knee and elbow joints and extensive regional myositis for all except for the patient with sternomanubrial joint infection. The diagnosis of K. kingae infection resulted in a change in the antibiotic regimen in 80% of the patients. CONCLUSION: Disproportionate synovial thickening, prominent peri-articular myositis, and/or characteristic sites of involvement demonstrating imaging features of infection or inflammation in a young child with mild infectious symptoms and elevated inflammatory markers should invoke the possibility of an underlying K. kingae infection.

US Evaluation of Juvenile Idiopathic Arthritis and Osteoarticular Infection.

Juvenile idiopathic arthritis (JIA) and osteoarticular infection can cause nonspecific articular and periarticular complaints in children. Although contrast material-enhanced magnetic resonance imaging is the reference standard imaging modality, musculoskeletal ultrasonography (US) is emerging as an important adjunct imaging modality that can provide valuable information relatively quickly without use of radiation or the need for sedation. However, diagnostic accuracy requires a systemic approach, familiarity with various US techniques, and an understanding of maturation-related changes. Specifically, the use of dynamic, Doppler, and/or multifocal US assessments can help confirm sites of disease, monitor therapy response, and guide interventions. In patients with JIA, ongoing synovial inflammation can lead to articular and periarticular changes, including synovitis, tenosynovitis, cartilage damage, bone changes, and enthesopathy. Although these findings can manifest in adult patients with rheumatoid arthritis, important differences and pitfalls exist because of the unique changes associated with an immature and maturing skeleton. In patients who are clinically suspected of having osteoarticular infection, the inability of US to evaluate the bone marrow decreases its sensitivity. Therefore, the US findings should be interpreted with caution because juxtacortical inflammation is suggestive, but neither sensitive nor specific, for underlying osteomyelitis. Similarly, the absence of a joint effusion makes septic arthritis extremely unlikely but not impossible. US findings of JIA and osteoarticular infection often overlap. Although certain clinical scenarios, laboratory findings, and imaging appearances can favor one diagnosis over the other, fluid analysis may still be required for definitive diagnosis and optimal treatment. US is the preferred modality for fluid aspiration and administering intra-articular corticosteroid therapy. © RSNA, 2017.

Fundamentals of Joint Injection.

OBJECTIVE: Using image guidance for joint access is a valuable fundamental skill. The purpose of this article is to review fluoroscopic and ultrasound-guided techniques and the medications used for injection into the glenohumeral, elbow, wrist, hip, knee, and ankle joints. CONCLUSION: Thorough understanding of basic injection principles, knowledge of the underlying anatomy, and consideration of the advantages and disadvantages of the imaging approaches should facilitate selection of the most appropriate technique for any clinical scenario.

Correlation Between Hip Arthroscopy Outcomes and Preoperative Anesthetic Hip Joint Injections, MR Arthrogram Imaging Findings, and Patient Demographic Characteristics.

OBJECTIVE: The purpose of this study is to determine whether the preoperative response to intraarticular hip anesthetic injection correlates with the outcome of hip arthroscopy. A secondary aim is to determine whether the outcome of arthroscopy correlates with intraarticular pathologic findings or patient demographic characteristics. MATERIALS AND METHODS: Ninety-three patients who underwent MR arthrography (MRA), preoperative injections of anesthetic into the hip joint (with pain scores documented), and subsequent hip arthroscopy (with a modified Harris Hip Score [mHHS] determined at 1 year after arthroscopy) were included in the study. MRA images and surgery reports were retrospectively reviewed to identify information about labral tear type and size and cartilage damage grade. The correlation between the response to hip anesthetic injection (defined as poor [0-30% improvement], moderate [31-60% improvement], or good [61-100% improvement]) and the surgical outcome (poor, fair, or good, as determined on the basis of the mHHS or the need for repeat surgery) was evaluated using the Fisher exact test. Univariate analysis (performed using the Fisher exact test) and multivariate analysis (performed using ANOVA) of correlations with age, sex, body mass index (BMI [weight in kilograms divided by the square of height in meters]), the interval between injection and surgery, labral tear type and size, and cartilage damage grade were also performed. RESULTS: Comparison of the response to preoperative hip anesthetic injection with the outcome of arthroscopy at 1 year indicated no statistically significant association (p = 0.59). The BMI of the patient, however, was statistically significantly associated with surgical outcome (p = 0.03), with a BMI of less than 25 denoting a higher likelihood of a good surgical outcome. No statistically significant correlations were noted in analyses of surgical outcomes and patient age (p = 0.31) and sex (p = 0.83); the interval between injection and surgery (p = 0.28); labral tear type, as determined by MRA (p = 0.34) and arthroscopy (p = 0.47); labral tear size, as determined by MRA (p = 0.34); and cartilage grade, as determined by MRA (p = 0.58) and arthroscopy (p = 0.26). CONCLUSION: No positive or negative correlation was noted between the response to preoperative hip anesthetic injection and the outcome at 1 year after hip arthroscopy. Only BMI was shown to correlate with the surgical outcome.

Unraveling the Posterolateral Corner of the Knee.

Although rare, posterolateral corner (PLC) injuries can result in sustained instability and failed cruciate ligament reconstruction if they are not diagnosed. The anatomy of the PLC was once thought to be perplexing and esoteric-in part because of the varying nomenclature applied to this region in the literature, which added unnecessary complexity. More recently, three major structures have been described as the primary stabilizers of the PLC on the basis of biomechanical study findings: the lateral collateral ligament, popliteus tendon, and popliteofibular ligament. An understanding of the anatomic relationships of these structures with each other and with the surrounding osseous structures is invaluable for improving the diagnostic accuracy of magnetic resonance (MR) imaging in the detection of PLC injuries and allowing a structured and systematic approach when interpreting the imaging findings. The majority of PLC injuries do not occur in isolation and are part of a more complex injury pattern that typically involves other vital supporting structures such as the cruciate ligaments, menisci, and medial ligamentous structures. Therefore, imaging has an ever-increasing role in the recognition of these injuries, as the clinical findings may be difficult to interpret adequately owing to synchronous injuries that dominate the physical examination findings. Furthermore, the diagnosis of acute high-grade PLC injuries is critical because early and aggressive treatment, for which surgical reconstruction is often required, leads to improved long-term outcomes and the prevention of persistent instability that would otherwise result in varus thrust gait, chronic pain, and accelerated cartilage damage. ©RSNA, 2016.

Rapid isotropic resolution cartilage assessment using radial alternating repetition time balanced steady-state free-precession imaging.

PURPOSE: To compare a balanced steady-state free-precession sequence with a radial k-space trajectory and alternating repetition time fat suppression (Radial-ATR) with other currently used fat-suppressed 3D sequences for evaluating the articular cartilage of the knee joint at 3.0T. MATERIALS AND METHODS: Radial-ATR, fast spin-echo (FSE-Cube), gradient recall-echo acquired in the steady-state (GRASS), and spoiled gradient recall-echo (SPGR) sequences with similar voxel volumes and identical scan times were performed at 3.0T on both knee joints of five volunteers. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) measurements were performed for all sequences using a double acquisition method and compared using Mann-Whitney Wilcoxon tests. Radial-ATR sequences with 0.3 mm and 0.4 mm isotropic resolution were also performed on the knee joints of seven volunteers and three patients with osteoarthritis. RESULTS: Average SNR values for cartilage, synovial fluid, and bone marrow were 54.7, 153.3, and 12.9, respectively, for Radial ATR, 30.8, 44.1, and 1.9, respectively, for FSE-Cube, 13.3, 46.9, and 3.3, respectively, for GRASS, and 19.1, 8.1, and 2.1, respectively, for SPGR. Average CNR values between cartilage and synovial fluid and between cartilage and bone marrow were 98.6 and 41.8, respectively, for VIPR-ATR, 13.4 and 28.8, respectively, for FSE-Cube, 33.6 and 10.0, respectively, for GRASS, and 11.0 and 16.9, respectively, for SPGR. Radial-ATR had significantly higher (P < 0.001) cartilage, synovial fluid, and bone marrow SNR and significantly higher (P < 0.01) CNR between cartilage and synovial fluid and between cartilage and bone marrow than FSE-Cube, GRASS, and SPGR. Radial-ATR provided excellent visualization of articular cartilage at high isotropic resolution with no image degradation due to off-resonance banding artifacts. CONCLUSION: Radial-ATR had superior SNR efficiency to other fat-suppressed 3D cartilage imaging sequences and produced high isotropic resolution images of the knee joint which could be used for evaluating articular cartilage at 3.0T.

MRI characteristics of healed and unhealed peripheral vertical meniscal tears.

OBJECTIVE: The objective of our study was to retrospectively compare the MRI characteristics of surgically confirmed healed and unhealed peripheral vertical meniscal tears. MATERIALS AND METHODS: The study group consisted of 64 patients with 86 peripheral vertical meniscal tears diagnosed on MRI who subsequently underwent knee surgery. The MRI examinations were retrospectively reviewed to assess the following tear characteristics: tear location relative to the meniscocapsular junction, tear width, tear length, tear extension through one or both surfaces, sequences on which tear was visualized, signal intensity of tear on T2-weighted imaging, and presence of low-signal-intensity strands bridging the tear on T2-weighted imaging. Multivariate logistic regression models were used to determine whether MRI characteristics could be used to distinguish between healed and unhealed tears at surgery. RESULTS: Tear location was the most significant characteristic (p<0.001) for distinguishing between healed and unhealed tears: 17 of 18 (94.4%) tears located at the meniscocapsular junction of the medial meniscus were healed and 15 of 68 (22.1%) tears not located at the meniscocapsular junction were healed. For tears not located at the meniscocapsular junction, MRI characteristics significantly associated with healed tears included a tear width of less than 2 mm (p=0.01), tear visualized only on intermediate-weighted imaging (p=0.01), tear showing intermediate or bright signal intensity on T2-weighted imaging (p=0.06), and low-signal-intensity strands bridging the tear on T2-weighted imaging (p<0.001). CONCLUSION: Most peripheral vertical tears at the meniscocapsular junction of the medial meniscus spontaneously heal. The MRI characteristics of tears not located at the meniscocapsular junction can help distinguish between healed and unhealed tears.

MR imaging-based diagnosis and classification of meniscal tears.

Magnetic resonance (MR) imaging is currently the modality of choice for detecting meniscal injuries and planning subsequent treatment. A thorough understanding of the imaging protocols, normal meniscal anatomy, surrounding anatomic structures, and anatomic variants and pitfalls is critical to ensure diagnostic accuracy and prevent unnecessary surgery. High-spatial-resolution imaging of the meniscus can be performed using fast spin-echo and three-dimensional MR imaging sequences. Normal anatomic structures that can mimic a tear include the meniscal ligament, meniscofemoral ligaments, popliteomeniscal fascicles, and meniscomeniscal ligament. Anatomic variants and pitfalls that can mimic a tear include discoid meniscus, meniscal flounce, a meniscal ossicle, and chondrocalcinosis. When a meniscal tear is identified, accurate description and classification of the tear pattern can guide the referring clinician in patient education and surgical planning. For example, longitudinal tears are often amenable to repair, whereas horizontal and radial tears may require partial meniscectomy. Tear patterns include horizontal, longitudinal, radial, root, complex, displaced, and bucket-handle tears. Occasionally, meniscal tears can be difficult to detect at imaging; however, secondary indirect signs, such as a parameniscal cyst, meniscal extrusion, or linear subchondral bone marrow edema, should increase the radiologist's suspicion for an underlying tear. Awareness of common diagnostic errors can ensure accurate diagnosis of meniscal tears. Online supplemental material is available for this article.

Snapping hip: imaging and treatment.

Snapping hip, or coxa saltans, presents as an audible or palpable snapping that occurs around the hip during movement and can be associated with or without pain. The prevalence of snapping hip is estimated to occur in up to 10% of the general population, but it is especially seen in athletes such as dancers, soccer players, weight lifters, and runners. Although the snapping sound can be readily heard, the diagnostic cause may be a clinical challenge. The causes of snapping hip have been divided into two distinct categories: extra-articular and intra-articular. Extra-articular snapping hip can be further subdivided into external and internal causes. Advances in imaging techniques have improved the diagnostic accuracy of the various causes of snapping hip, mainly by providing real-time imaging evaluation of moving structures during the snapping phase. Image-guided treatments have also been useful in the diagnostic work-up of snapping hip given the complexity and multitude of causes of hip pain. We discuss the common and uncommon causes of snapping hip, the advanced imaging techniques that now give us a better understanding of the underlying mechanism, and an image-guided diagnostic and therapeutic algorithm that helps to identify surgical candidates.

Performing fluoroscopically guided interlaminar lumbar epidural injections.

OBJECTIVE: The purpose of this video article is to provide a step-by-step guide for performing fluoroscopically guided interlaminar lumbar epidural injections, emphasizing the anatomy of the epidural space, anatomic landmarks to aid in needle placement, techniques, and ways of minimizing potential complications. CONCLUSION: Low back pain and radiculopathy afflict millions of people each year with enormous socioeconomic ramifications and individual disability. This condition has a prevalence of at least 13% and is the second most common symptom-related cause for office visits in the United States. Epidural injections have become the most commonly performed intervention in the management of chronic low back pain in the United States.

Performing thoracic transforaminal injections: a new technique.

PURPOSE: To evaluate a technique to perform fluoroscopically directed thoracic transforaminal epidural injections. MATERIALS AND METHODS: Institutional review board approval and a waiver of consent were obtained for this retrospective HIPAA-compliant study. Findings from 198 consecutively performed foraminal nerve blocks and foraminal epidural injections in the thoracic spine from June 27, 1997 to December 29, 2007 were retrospectively reviewed. This study was designed to evaluate a current technique and the experience with an approach that improves safety by decreasing the chance of inadvertent injury to nontargeted structures. Fluoroscopic spot views retained as part of a quality assurance program were available in all patients for review. RESULTS: By utilizing this technique, there was a single delayed pneumothorax that occurred because of deviation from the accepted technique. No other major complications occurred (which the authors defined as death, neurovascular injury, pneumothorax, and infection). Inadvertent puncture of the dura did not occur. Minor complications included vasovagal response and transient pain during the administration of injectate, which were resolved by the termination of the procedure. The ease of identifying the ribs fluoroscopically and utilizing the rib as a conduit into the foramen provided an advantage in patients with osteopenia, severe osteoarthritis, and scoliosis compared with previously described techniques. CONCLUSION: This study evaluated an innovative technique to perform fluoroscopically directed thoracic intraforaminal nerve blocks that showed few complications and anatomically avoided transgression of structures in the posterior mediastinum.

Musculoskeletal ultrasound: how to treat calcific tendinitis of the rotator cuff by ultrasound-guided single-needle lavage technique.

OBJECTIVE: The purpose of this video article is to illustrate the ultrasound appearance of calcium deposition in the rotator cuff and provide a detailed step-by-step protocol for performing the ultrasound-guided single-needle lavage technique for the treatment of calcific tendinitis with emphasis on patient positioning, necessary supplies, real-time lavage technique, and steroid injection into the subacromial subdeltoid bursa. CONCLUSION: Musculoskeletal ultrasound is well established as a safe, cost-effective imaging tool in diagnosing and treating common musculoskeletal disorders. Calcific tendinitis of the rotator cuff is a common disabling cause of shoulder pain. Although most cases are self-limiting, a subset of patients is refractory to conservative therapy and requires treatment intervention. Ultrasound-guided lavage is an effective and safe minimally-invasive treatment not readily offered in the United States as an alternative to surgery, perhaps because of the limited prevalence of musculoskeletal ultrasound programs and limited training. On completion of this video article, the participant should be able to develop an appropriate diagnostic and therapeutic algorithm for the treatment of calcific tendinitis of the rotator cuff using ultrasound.

Imaging acute trauma of the elbow.

Elbow injuries, both acute and chronic, continue to rise as both the young and elderly increase their participation in athletic activities. The role of imaging is to provide supportive data as to the cause of the patient's symptoms and to guide treatment options for the referring physician. Understanding the anatomy and biomechanics of this sophisticated joint, various injury patterns, and the implication of injury to the static and dynamic stabilizers will result in improvement in diagnostic accuracy. Each of these topics are discussed to provide a foundation and overview of key concepts necessary to understand common elbow injuries.

Musculoskeletal ultrasound: elbow imaging and procedures.

Elbow injuries, both acute and chronic sports-related cases, have increased over the last decade. With one in every four members of a household participating in sports, both clinics and radiology departments are seeing more patients with elbow pain. High-resolution ultrasound is well suited for evaluating the elbow. Ultrasound is growing in popularity and fast becoming another modality that the radiologist can use to help diagnose elbow pathology. With advancing transducer technology and accessibility, ultrasound offers focused and real-time high-resolution imaging of tendons, ligaments, and nerve structures. Its advantages include the use of safe nonionizing radiation, accessibility, and cost effectiveness. Another unique advantage is its ability for dynamic assessment of tendon and ligament structures such as in cases of partial tears of the medial ulnar collateral ligament or ulnar nerve dislocation. It is also easy to assess the contralateral side as a control. Ultrasound is also useful in therapeutic guided injections for its multiplanar capability and clear visualization of major vessels and nerves. We discuss the unique application of ultrasound in evaluating common elbow pathology and in advanced ultrasound-guided treatments such as dextrose prolotherapy and platelet-rich plasma.

Fluoroscopy-guided percutaneous needle aspiration of posterior epidural abscesses: a report of two cases.

Introduction: Spinal epidural abscesses are most commonly treated with surgical decompression and antibiotics or in specific instances managed medically with antibiotic therapy alone. Image-guided percutaneous aspiration as an alternative to surgery has only rarely been reported in the literature. Case presentation: We report two cases of successful fluoroscopy-guided needle aspiration of posterior epidural abscesses. Case 1 is a 48-year-old man who presented with several days of escalating back pain and constitutional symptoms with MRI showing a posterior epidural abscess at L2-L3 causing spinal stenosis. The patient remained neurologically intact. Percutaneous needle aspiration of the collection provided dramatic pain relief with the aspirate growing methicillin sensitive Staphylococcus aureus. The patient made a full recovery on antibiotic therapy. Case 2 is an 81-year-old man who presented with worsening upper back pain and was found to have osteomyelitis/discitis with a large posterior epidural abscess in the thoracic spine. Needle drainage was performed with the sample growing Bacteroides fragilis. This patient also responded successfully to nonsurgical management with full recovery after appropriate antibiotic therapy. Discussion: In carefully selected patients, image-guided needle aspiration of posterior epidural abscesses may be a viable and less invasive alternative to surgery.

Bone Mineral Density T-Scores Derived from CT Attenuation Numbers (Hounsfield Units): Clinical Utility and Correlation with Dual-energy X-ray Absorptiometry.

Background: Clinical computed tomography (CT) studies performed for other indications can be used to opportunistically assess vertebral bone without additional radiation or cost. Reference values for young women are needed to evaluate diagnostic accuracy and track changes in CT bone mineral density values across the lifespan. The purpose of this study was to determine reference values for lumbar trabecular CT attenuation (Hounsfield units [HU]) and determine the diagnostic accuracy of HU T-scores (T-scoreHU) for identifying individuals with osteoporosis. Methods: We performed a retrospective single-center cohort study of patients undergoing CT of the lumbar spine. Reference values for lumbar spine Hounsfield units were determined from a reference sample of 190 young women aged 20-30 years undergoing CT scan of the lumbar spine. A separate sample of 252 older subjects undergoing CT and dual-energy X-ray absorptiometry (DXA) within a 6-month period that served as a validation cohort. Osteoporosis was defined by T-scoreDXA ≤ -2.5. Reference values were determined for lumbar HU from L1 to L4 from the reference cohort (24.0 ± 2.9 years). T-scoreHU was calculated in the validation cohort (58.9 ± 7.5 yrs). Receiver operating characteristic (ROC) curves were used to assess sensitivity and specificity of T-scoreHU for this task. Results: Reference group HU ranged from 227 ± 42 at L3 to 236 ± 42 at L1 (P < 0.001). Validation group T-scoreDXA was -0.7 ± 1.5 and -0.9 ± 1.2 at lumbar and femoral sites respectively. Mean T-scoreHU was -2.3. T-scoreHU of -3.0, corresponding to 110 HU, was 48% sensitive and 91% specific for osteoporosis in the validation group. ROC area under the curve ranged from 0.825 to 0.853 depending on lumbar level assessed. Conclusions: Although lumbar trabecular HU T-scores are lower than DXA T-scores, thresholds can be selected to achieve high sensitivity and specificity when screening for osteoporosis. Patients with a lumbar T-scoreHU ≤ -3.0 should be referred for additional evaluation. Further research into HU T-scores and clinical correlates may also provide a tool to assess changes in vertebral bone and the relationship to fracture risk across the lifespan.