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OBJECTIVES: To evaluate a dynamic half-Fourier acquired single turbo spin echo (HASTE) sequence following anterior cervical discectomy and fusion (ACDF) at the junctional level for adjacent segment degeneration comparing dynamic listhesis to radiographs and assessing dynamic cord contact and deformity during flexion-extension METHODS: Patients with ACDF referred for cervical spine MRI underwent a kinematic flexion-extension sagittal 2D HASTE sequence in addition to routine sequences. Images were independently reviewed by three radiologists for static/dynamic listhesis, and compared to flexion-extension radiographs. Blinded assessment of the HASTE sequence was performed for cord contact/deformity between neutral, flexion, and extension, to evaluate concordance between readers and inter-modality agreement. Inter-reader agreement for dynamic listhesis and impingement grade and inter-modality agreement for dynamic listhesis on MRI and radiographs was assessed using the kappa coefficient and percentage concordance. RESULTS: A total of 28 patients, mean age 60.2 years, were included. Mean HASTE acquisition time was 42 s. 14.3% demonstrated high grade dynamic stenosis (> grade 4) at the adjacent segment. There was substantial agreement for dynamic cord impingement with 70.2% concordance (kappa = 0.62). Concordance across readers for dynamic listhesis using HASTE was 81.0% (68/84) (kappa = 0.16) compared with 71.4% (60/84) (kappa = 0.40) for radiographs. Inter-modality agreement between flexion-extension radiographs and MRI assessment for dynamic listhesis across the readers was moderate (kappa = 0.41; 95% confidence interval: 0.16 to 0.67). CONCLUSIONS: A sagittal flexion-extension HASTE cine sequence provides substantial agreement between readers for dynamic cord deformity and moderate agreement between radiographs and MRI for dynamic listhesis. CLINICAL RELEVANCE STATEMENT: Degeneration of the adjacent segment with instability and myelopathy is one of the most common causes of pain and neurological deterioration requiring re-operation following cervical fusion surgery. KEY POINTS: • A real-time kinematic 2D sagittal HASTE flexion-extension sequence can be used to assess for dynamic listhesis, cervical cord, contact and deformity. • The additional kinematic cine sequence was well tolerated and the mean acquisition time for the 2D HASTE sequence was 42 s (range 31-44 s). • A sagittal flexion-extension HASTE cine sequence provides substantial agreement between readers for dynamic cord deformity and moderate agreement between radiographs and MRI for dynamic listhesis.

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Ultrasound visualization affords proceduralists versatile and accurate guidance for a variety of percutaneous, minimally invasive procedures in the musculoskeletal system including joint (intra-articular) injections or aspirations, intra-bursal injections, peritendinous, and perineural injections. A variety of percutaneous procedures are traditionally performed blindly, but may be more easily or more accurately performed with the real-time assistance of ultrasound guidance. Other procedures are only possible utilizing image-guidance, due to the required precision of the injection because of delicate local anatomy or depth of the injection; ultrasound is a safe, portable, and widespread modality that can be used to assist the proceduralist in localizing the needle tip in such cases, to ensure safe and accurate delivery of the medication, most frequently a solution of steroid and anesthetic. This review aims to provide a foundational approach to ultrasound-guided procedures in the musculoskeletal system, offering tips and tricks that can be employed in many different procedures including intra-articular, juxta-articular, and perineural injections for a multitude of clinical scenarios. Technical considerations regarding ultrasound transducer selection, sonographic technique, as well as common indications, contraindications, and complications of these procedures, are presented. Additionally, a variety of pharmacologic considerations for proceduralists contemplating ultrasound-guided injections are discussed.

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BACKGROUND: Detection of rotator cuff tears, a common cause of shoulder disability, can be time-consuming and subject to reader variability. Deep learning (DL) has the potential to increase radiologist accuracy and consistency. PURPOSE: The aim of this study was to develop a prototype DL model for detection and classification of rotator cuff tears on shoulder magnetic resonance imaging into no tear, partial-thickness tear, or full-thickness tear. MATERIALS AND METHODS: This Health Insurance Portability and Accountability Act-compliant, institutional review board-approved study included a total of 11,925 noncontrast shoulder magnetic resonance imaging scans from 2 institutions, with 11,405 for development and 520 dedicated for final testing. A DL ensemble algorithm was developed that used 4 series as input from each examination: fluid-sensitive sequences in 3 planes and a sagittal oblique T1-weighted sequence. Radiology reports served as ground truth for training with categories of no tear, partial tear, or full-thickness tear. A multireader study was conducted for the test set ground truth, which was determined by the majority vote of 3 readers per case. The ensemble comprised 4 parallel 3D ResNet50 convolutional neural network architectures trained via transfer learning and then adapted to the targeted domain. The final tear-type prediction was determined as the class with the highest probability, after averaging the class probabilities of the 4 individual models. RESULTS: The AUC overall for supraspinatus, infraspinatus, and subscapularis tendon tears was 0.93, 0.89, and 0.90, respectively. The model performed best for full-thickness supraspinatus, infraspinatus, and subscapularis tears with AUCs of 0.98, 0.99, and 0.95, respectively. Multisequence input demonstrated higher AUCs than single-sequence input for infraspinatus and subscapularis tendon tears, whereas coronal oblique fluid-sensitive and multisequence input showed similar AUCs for supraspinatus tendon tears. Model accuracy for tear types and overall accuracy were similar to that of the clinical readers. CONCLUSIONS: Deep learning diagnosis of rotator cuff tears is feasible with excellent diagnostic performance, particularly for full-thickness tears, with model accuracy similar to subspecialty-trained musculoskeletal radiologists.

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Background MRI is a powerful diagnostic tool with a long acquisition time. Recently, deep learning (DL) methods have provided accelerated high-quality image reconstructions from undersampled data, but it is unclear if DL image reconstruction can be reliably translated to everyday clinical practice. Purpose To determine the diagnostic equivalence of prospectively accelerated DL-reconstructed knee MRI compared with conventional accelerated MRI for evaluating internal derangement of the knee in a clinical setting. Materials and Methods A DL reconstruction model was trained with images from 298 clinical 3-T knee examinations. In a prospective analysis, patients clinically referred for knee MRI underwent a conventional accelerated knee MRI protocol at 3 T followed by an accelerated DL protocol between January 2020 and February 2021. The equivalence of the DL reconstruction of the images relative to the conventional images for the detection of an abnormality was assessed in terms of interchangeability. Each examination was reviewed by six musculoskeletal radiologists. Analyses pertaining to the detection of meniscal or ligament tears and bone marrow or cartilage abnormalities were based on four-point ordinal scores for the likelihood of an abnormality. Additionally, the protocols were compared with use of four-point ordinal scores for each aspect of image quality: overall image quality, presence of artifacts, sharpness, and signal-to-noise ratio. Results A total of 170 participants (mean age ± SD, 45 years ± 16; 76 men) were evaluated. The DL-reconstructed images were determined to be of diagnostic equivalence with the conventional images for detection of abnormalities. The overall image quality score, averaged over six readers, was significantly better (P < .001) for the DL than for the conventional images. Conclusion In a clinical setting, deep learning reconstruction enabled a nearly twofold reduction in scan time for a knee MRI and was diagnostically equivalent with the conventional protocol. © RSNA, 2023 Supplemental material is available for this article. See also the editorial by Roemer in this issue.

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OBJECTIVE: To evaluate imaging features of soft tissue metastases, technical factors associated with diagnostic yield of image-guided biopsy, and clinical impact of biopsy results on patient outcomes. MATERIALS AND METHODS: A total of 1605 image-guided soft tissue biopsies were retrospectively identified from December 2010 to December 2020. Included lesions were histologically proven musculoskeletal soft tissue metastases. Lesions were excluded if intraabdominal, intrathoracic, retroperitoneal, associated with osseous lesions or surgical scar implants or arising from skin or lymph nodes. Image guidance modality, needle size, number of cores, and lesion location, size, and depth from skin were recorded. Patient demographics, malignancy history, biopsy-driven changes in management, and survival rate after biopsy were collected. RESULTS: Forty-six patients met the inclusion criteria with a biopsy diagnostic yield of 44/46 (95.7%). Metastases were most commonly located truncal (82.6%, p < 0.001) and intramuscular (78.3%, p < 0.001). A total of 37/46 (80.4%) biopsies were US-guided. And 9/46 (19.6%) were CT-guided. There was no significant difference in the number of cores or mean needle gauge between diagnostic and nondiagnostic biopsies. At time of review, 23 (50%) patients were deceased, with a mean survival of 13.5 months after biopsy. The majority (71.7%) of patients had a known primary malignancy at time of biopsy, most commonly lung (24.2%) and breast (24.2%). Overall survival showed no association with anatomic location (p > 0.83) or tissue type (p > 0.34). The most common biopsy-driven outcome was initiation of chemotherapy, immunotherapy, and/or radiotherapy (52.2%). CONCLUSION: Image-guided biopsy for soft tissue metastases has high diagnostic yield and commonly influences clinical management. Metastases were most commonly intramuscular in the trunk and are associated with poor prognosis.

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OBJECTIVE: This study aimed to investigate patient-specific, lesion-related, and technical factors that potentially influence diagnostic yield of computed tomography (CT)-guided biopsies of bone lesions. METHODS: Computed tomography-guided bone lesion biopsies performed over a 2-year period were retrospectively reviewed, including image review and electronic medical records for pathology reports and clinical follow-up. Lesions were tabulated by prebiopsy CT and magnetic resonance imaging features. Patients with nondiagnostic biopsies were assessed for presumptive clinical diagnosis and management. RESULTS: Nondiagnostic pathology results were obtained in 31 of 156 cases (19.87%), among which diagnoses were confirmed by other tissue sampling in 9; clinical follow-up of up to 2 years yielded no diagnosis in 10 and presumptive diagnoses in 12. The nondiagnostic biopsy rate of long bone lesions was higher than that of other bone lesions (odds ratio, 3.46; 95% confidence interval, 1.32-9.09). There were no significant differences in patient American Society of Anesthesiologists class, mean body mass index, sedation method, number of cores, or needle gauge between diagnostic and nondiagnostic biopsy cohorts. Diagnostic yield was not significantly different between occult, lytic, or sclerotic lesions. There was no difference in diagnostic yield regarding presence of cortical break, gadolinium enhancement, or lesion depth. Magnetic resonance imaging was obtained before biopsy in significantly more nondiagnostic cases compared with diagnostic cases ( P = 0.027). CONCLUSIONS: Computed tomography-guided biopsies had a nondiagnostic rate of 19.87%, and lesions in the long bones of the extremities were disproportionately common among this group. There was no significant association between biopsy results and several patient-specific, lesion-related, and technical factors.

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OBJECTIVES: To determine the incidence of infectious complications following ultrasound-guided musculoskeletal interventions performed with a disinfected uncovered ultrasound transducer footprint. METHODS: Electronic medical records of all patients who underwent an ultrasound-guided musculoskeletal procedure (including injection, calcific lavage, or ganglion cyst aspiration) performed by any of the 14 interventional musculoskeletal radiologists at our institution between January 2013 and December 2018 were retrospectively reviewed to identify procedure site infections. Biopsies and joint aspirations were excluded. The procedures were performed using a disinfected uncovered transducer footprint. First, an automated chart review identified cases with (1) positive answers to the nurse's post-procedure call, (2) an International Classification of Diseases (ICD) diagnostic code related to a musculoskeletal infection, or (3) an antibiotic prescription within 30 days post-procedure. Then, these cases were manually reviewed for evidence of procedure site infection. RESULTS: In total, 6511 procedures were included. The automated chart review identified 3 procedures (2 patients) in which post-procedural fever was reported during the nurse's post-procedure call, 33 procedures (28 patients) with an ICD code for a musculoskeletal infection, and 220 procedures (216 patients) with an antibiotic prescription within 30 post-procedural days. The manual chart review of these patients revealed no cases of confirmed infection and 1 case (0.015%) of possible site infection. CONCLUSIONS: The incidence of infectious complications after an ultrasound-guided musculoskeletal procedure performed with an uncovered transducer footprint is extremely low. This information allows radiologists to counsel their patients more precisely when obtaining informed consent. KEY POINTS: • Infectious complications after ultrasound-guided musculoskeletal procedures performed with a disinfected uncovered transducer footprint are extremely rare.

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Real-time dynamic magnetic resonance imaging (MRI) in the musculoskeletal system touts the ability to perceive in vivo joint kinematics, which is particularly attractive for diagnosing dynamic pathologies such as joint instability or impingement syndromes.The clinical utility of dynamic MRI in the musculoskeletal system is wide ranging, from patellofemoral kinematics to imaging of the hip in femoroacetabular impingement and also dynamic spine imaging. Patellofemoral instability is an ideal diagnostic target, as knee flexion and extension are easily performed in an MRI scanner, and dynamic measurements have been correlated to clinical and static radiologic parameters of instability. Proving the clinical utility of this MRI technique requires rigorous technical standardization and definition of normal patellofemoral motion parameters. Validated imaging methods and rigorously defined normal range data are required to light the path forward, and the video format of dynamic MRI is also ideal for advancing patient-centered care, improving patient literacy on their condition, and offering a potential catalyst for shared decision-making between surgeons and their patients.

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A variety of foot and ankle pathologies can impair patient's daily activities, ultimately requiring surgical management. However, with improvements in image-guided intervention, the joints, soft tissues, and osseous structures may be accessible using various percutaneous techniques as a potential alternative therapeutic tool, avoiding the need for surgery with its associated risks and morbidity. This article discusses the potential range of image-guided interventional treatments. Injections, aspiration, biopsies, cryoablation, and radiofrequency ablation are described. Newer novel treatments are also covered. Finally, the common pathologies of Morton's neuroma, Achilles tendinopathy, and plantar fasciitis are addressed.

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PURPOSE: The purpose of this study was to evaluate the mid-term results of posterior medial meniscal root tear (PMMRT) repair through assessment of functional outcome scores and magnetic resonance imaging (MRI). METHODS: This was a single-center, retrospective study evaluating patients that had undergone a PMMRT. This was a follow-up to a previously published 2-year outcome study (all original patients were invited to participate). Clinical outcomes included pre- and postoperative International Knee Documentation Committee (IKDC) and Lysholm scores. Root healing, meniscal extrusion, and cartilage degeneration via International Cartilage Repair Society Scale (ICRS) grades were assessed on MRI by two musculoskeletal fellowship-trained radiologists. RESULTS: 10 of the original study's 18 patients were able to participate. Mean age and BMI was 48.4 ± 12.0 years and 29.5 ± 4.5, respectively, with mean follow-up 65.5 ± 8.3 months (range 52.0-75.8) (60% female). The IKDC significantly increased from 43 ± 13 preoperatively to 75 ± 16 at 5-year follow-up (p < 0.001). There was no significant change in IKDC score between 2-year and 5-year follow-up [75 ± 16 vs 73 ± 20, (n.s)]. The Lysholm also significantly increased between preoperative and 5-year follow-up (49 ± 7 vs 84 ± 11, p < 0.001). There was no significant change between Lysholm score at 2-year and 5-year follow-up [84.0 ± 11 vs 82 ± 13, (n.s)]. Mean extrusion did not significantly change from the preoperative state to 5-year follow-up [4.80 mm ± 1.9 vs 5.0 mm ± 2.5, (n.s.)]. Extrusion also did not significantly change between 2-and 5-year follow-up [6.1 ± 3.2 mm vs 5.0 mm ± 2.5, (n.s.)]. No patients with > 3 mm of extrusion on preoperative MRI had < 3 mm of extrusion on postoperative MRI. Both medial femoral condyle and medial tibial plateau ICRS grades significantly increased from preoperative to 2-year follow-up (p = 0.038, p = 0.023, respectively). Medial femoral condyle and medial tibial plateau ICRS grades again significantly increased between 2-year and 5-year follow-up (p = 0.014, p = 0.034). CONCLUSION: Patients treated with the transtibial suture pullout technique with two locking cinch sutures had maintenance of clinical outcome improvements at 5-year follow-up. However, extrusion was widely prevalent, with worsening progression of femoral and tibial chondral disease. LEVEL OF EVIDENCE: Level 4.

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BACKGROUND: There is a paucity of literature describing MRI patterns of high ankle sprains in pediatric patients. Radiologists should understand MRI patterns of these injuries in both adults and children. OBJECTIVE: To describe normal MRI appearance of pediatric syndesmotic ligaments and compare MRI patterns of high ankle sprains in children versus adults. MATERIALS AND METHODS: We reviewed consecutive ankle MRIs performed over 3 years and divided them into three cohorts: a normal pediatric (≤16 years) cohort, and pediatric and adult cohorts with acute/subacute ankle syndesmosis injuries. Our retrospective review assessed interobserver agreement (Cohen kappa coefficient) and normal pediatric syndesmotic anatomy. We compared patterns of high ankle sprains (Fisher exact test) including ligament tears, periosteal stripping, avulsions and fractures. RESULTS: Of the 582 ankle MRIs, we included 25 in the normal pediatric cohort, 20 in the pediatric injury cohort and 23 in the adult injury cohort. The anterior and posterior tibiofibular ligaments all attached to cortex or cartilaginous precursor, while the interosseous ligament/membrane complex attached to the fibrous periosteum in 22/25 (88%) normal pediatric cases. Tibial periosteal stripping at the interosseous ligament/membrane complex attachment occurred in 7/20 (35%) pediatric and 1/23 (4%) adult injury cases (P=0.02). No other statistically significant differences were found. Interobserver agreement ranged from kappa=0.46 to kappa=0.82 (ligament tears), 0.38 to 0.45 (avulsions) and 0.69 to 0.77 (periosteal stripping). CONCLUSION: The normal interosseous ligament/membrane complex typically attaches to fibrous periosteum rather than bony cortex. Tibial periosteal stripping, usually without tibial fracture, is significantly more common among pediatric high ankle sprains. MRI patterns of high ankle sprains are otherwise not significantly different between children and adults.

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BACKGROUND. Tearing of the superior peroneal retinaculum is a known cause of peroneal tendon subluxation-dislocation. However, with the exception of cortical avulsions at the fibular attachment, superior peroneal retinaculum injury and subsequent peroneal tendon subluxation-dislocation are typically radiographically occult. OBJECTIVE. The purpose of this study was to evaluate the previously undescribed association between radiographic fibular tip periostitis and MRI evidence of peroneal tendon subluxation-dislocation in patients with hindfoot valgus. METHODS. Thirty-five patients with radiographic fibular tip periostitis and 35 ageand sex-matched individuals without periostitis were selected from among 220 consecutively registered patients with hindfoot valgus who had undergone both ankle radiography and MRI. Studies were retrospectively assessed by two musculoskeletal radiologists in consensus and by two additional blinded radiologists independently for the presence of peroneal tendon subluxation-dislocation, presence of subfibular impingement, and hindfoot valgus angle measurements. Interobserver agreement and accuracy, sensitivity, and specificity in the detection of fibular periostitis, peroneal tendon subluxation-dislocation, and subfibular impingement were calculated, and Fischer exact, Mann-Whitney, kappa coefficient, and intraclass correlation tests were performed. RESULTS. Both the consensus and the two independent interpretations showed that the frequency of peroneal tendon subluxation-dislocation was significantly greater in the group with periostitis (62.9%, 65.7%, and 85.7%) than in the group without periostitis (5.7%, 0%, and 14.3%) (p < .001). The finding of periostitis was specific and highly sensitive for predicting peroneal tendon subluxation-dislocation. The frequency of subfibular impingement was also statistically higher in the group with periostitis than in the group without it (p < .001). The hindfoot valgus angle was statistically larger in the group with periostitis than in the control group (p = .01-.002) and among patients with versus those without peroneal tendon subluxation-dislocation (p = .002 to p < .001). The blinded readers had substantial or almost perfect agreement on all imaging interpretations (concordance rate, 82.9-95.7%; κ = 0.66-0.91). CONCLUSION. The radiographic finding of fibular tip periostitis in patients with hindfoot valgus can be a predictor of peroneal tendon subluxation-dislocation and may also suggest advanced hindfoot valgus and subfibular impingement. These radiographic associations should be recognized by the radiologist, and MRI may be recommended as clinically indicated. CLINICAL IMPACT. Chronic undiagnosed peroneal tendon subluxation-dislocation can be a persistent cause of lateral ankle pain, leading to further degeneration and the possibility of complete peroneal tendon tears. Distal fibular periostitis in patients with hindfoot valgus can be a reliable radiographic indicator of this entity and may suggest the presence of subfibular impingement.

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BACKGROUND: Half-Fourier acquisition single-shot turbo spin-echo (HASTE), continuous radial gradient-echo (GRE), and True FISP allow real-time dynamic assessment of the spine. PURPOSE: To evaluate the feasibility of adding dynamic sequences to routine spine magnetic resonance imaging (MRI) for assessment of spondylolisthesis. MATERIAL AND METHODS: Retrospective review was performed of patients referred for dynamic MRI of the cervical or lumbar spine between January 2017 and 2018 who had flexion-extension radiographs within two months of MRI. Exclusion criteria were: incomplete imaging; spinal hardware; and inability to tolerate dynamic examination. Blinded, independent review by two board-certified musculoskeletal radiologists was performed to assess for spondylolisthesis (>3 mm translation); consensus review of dynamic radiographs served as the gold standard. Cervical spinal cord effacement was assessed. Inter-reader agreement and radiographic concordance was calculated for each sequence. RESULTS: Twenty-one patients were included (8 men, 13 women; mean age 47.9 ± 16.5 years). Five had MRI of the cervical spine and 16 had MRI of the lumbar spine. Mean acquisition time was 18.4 ± 1.7 min with dynamic sequences in the range of 58-77 s. HASTE and True FISP had the highest inter-reader reproducibility (κ = 0.88). Reproducibility was better for the lumbar spine (κ = 0.94) than the cervical spine (κ = 0.28). Sensitivity of sequences for spondylolisthesis was in the range of 68.8%-78.6%. All three sequences had high accuracy levels: ≥90.5% averaged across the cervical and lumbar spine. Cervical cord effacement was observed during dynamic MRI in two cases (100% agreement). CONCLUSION: Real-time dynamic MRI sequences added to spine MRI protocols provide reliable and accurate assessment of cervical and lumbar spine spondylolisthesis during flexion and extension.

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BACKGROUND. Literature on glenohumeral dislocations has focused on younger patient populations because of high recurrence rates. However, the spectrum of injuries sustained in younger versus older patient populations is reported to be quite different. OBJECTIVE. The purpose of this article is to describe MRI findings and management of anterior shoulder instability in the aging (≥ 60 years) population. METHODS. Shoulder MRI examinations of anterior glenohumeral dislocations in patients 40 years old and older were subdivided into groups younger than 60 years old or 60 years old and older and reviewed by two musculoskeletal radiologists for a Hill-Sachs lesion, other fracture, glenoid injury, capsulolabral injury, rotator cuff tear, muscle atrophy, and axillary nerve injury. Fischer exact test and logistic regression was evaluated for significant differences between cohorts, and interreader agreement was assessed. Surgical management was recorded, if available. RESULTS. A total of 104 shoulder MRI examinations (age range, 40-79 years; mean age, 58.3 years; 52 women, 52 men) were reviewed (54 examinations < 60 years; 50 examinations ≥ 60 years). Acute high-grade or full-thickness supraspinatus (64.0% vs 37.0%; p = .001), infraspinatus (28.0% vs 14.8%; p = .03), and subscapularis (22.0% vs 3.7%; p = .003) tears were more common in the group 60 years old and older. Hill-Sachs lesions were more common in the younger group (81.5% vs 62.0%; p = .046). Greater tuberosity fractures were seen in 15.4% of the overall cohort, coracoid fractures in 4.8%, and acute axillary nerve injuries in 9.6%. Interreader concordance was 88.5-89.4% for rotator cuff tears and 89.4-97.1% for osseous injury. In the group younger than 60 years old, 11 of 37 subjects (29.7%) had rotator cuff repair and 11 of 37 (29.7%) had labral repair, whereas 17 of 36 (47.2%) of the older group underwent rotator cuff repair, six of 36 (16.7%) underwent reverse shoulder arthroplasty, and six of 36 (16.7%) underwent labral repair. CONCLUSION. Radiologists should have a high index of suspicion for acute rotator cuff tears in anterior shoulder instability, especially in aging populations. Greater tuberosity or coracoid fractures and axillary nerve injury occur across all ages, whereas Hill-Sachs injuries are more common in younger patients. CLINICAL IMPACT. Acute high-grade or full-thickness rotator cuff tears are seen with higher frequency in older populations after anterior glenohumeral dislocation. Osseous and nerve injuries are important causes of patient morbidity that if not carefully sought out may be overlooked by the interpreting radiologist on routine imaging.

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Normal skeletal development in the pediatric ankle is dynamic and often produces variable imaging appearances that are subject to misinterpretation. Radiologists must understand the underlying developmental phenomena, such as endochondral and membranous ossification and physeal fusion, and be familiar with their common and uncommon imaging manifestations unique to the pediatric ankle. This is especially true as the use of MRI in the evaluation of musculoskeletal trauma expands among younger populations. The authors focus on MRI evaluation of the skeletally maturing pediatric ankle and present pearls for accurately distinguishing normal findings and imaging pitfalls from true pathologic findings. The normal but often variable imaging findings of preossification, secondary ossification, and multiple ossification centers, as well as the range of bone marrow signal intensities that can be visualized within ossification centers, are described, along with tips to help differentiate these from true pathologic findings such as contusion, fracture, or tumor. The authors also review dynamic periosteal and physeal contributions to bone growth to highlight helpful distinguishing features and avoid misdiagnosis of common subperiosteal and periphyseal abnormalities. For example, the normal trilaminar appearance of the immature cortex and periosteum should not be mistaken for periosteal reaction, traumatic stripping, or subperiosteal hematoma. In addition, the physis can have several confusing but normal appearances, including normal physeal undulations (eg, Kump bump) or focal periphyseal edema, which should not be mistaken for pathologic findings such as physeal fracture, infection, or bar. ©RSNA, 2020.

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PURPOSE: To assess the utility of a 2D dynamic HASTE sequence in assessment of cervical spine flexion-extension, specifically (1) comparing dynamic spondylolisthesis to radiographs and (2) assessing dynamic contact upon or deformity of the cord. METHODS: Patients with a dynamic flexion-extension sagittal 2D HASTE sequence in addition to routine cervical spine sequences were identified. Static and dynamic listhesis was first determined on flexion-extension radiographs reviewed in consensus. Blinded assessment of the dynamic HASTE sequence was independently performed by 2 radiologists for (1) listhesis and translation during flexion-extension and (2) dynamic spinal cord impingement (cord contact or deformity between neutral, flexion and extension). RESULTS: 32 scans in 32 patients (9 males, 23 females) met inclusion criteria acquired on 1.5 T (n = 15) and 3 T (n = 17) scanners. The mean acquisition time was 51.8 s (range 20-95 seconds). Dynamic translation was seen in 14 patients on flexion-extension radiographs compared to 12 (reader 1) and 13 (reader 2) patients on HASTE, with 90.6 % agreement (K = 0.83; p = 0.789). In all cases dynamic listhesis was ≤3 mm translation with one patient showing dynamic listhesis in the range 4-6 mm. Four cases (13 %) demonstrated deformity of the cord between flexion-extension, not present in the neutral position. For cord impingement there was strong inter-reader agreement (K = 0.93) and the paired sample Wilcoxon signed rank test found no significant difference between the impingement scores of the two readers (p = 0.787). CONCLUSIONS: A sagittal dynamic flexion-extension HASTE sequence provides a rapid addition to standard MRI cervical spine protocols, which may useful for assessment of dynamic spondylolisthesis and cord deformity.

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Ultrasound-guided hookwire localization was initially introduced to facilitate the excision of nonpalpable breast lesions by guiding surgical exploration, thereby reducing operative time and morbidity. The same technique has since found utility in a range of other applications outside breast and can be useful within the musculoskeletal system. Despite this, there remains limited literature with respect to its technical aspects and practical utility. We describe our technique and a series of preoperative ultrasound-guided wire localizations in the musculoskeletal system to assist surgical excision of 4 soft tissue masses.

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OBJECTIVE. Deep learning (DL) image reconstruction has the potential to disrupt the current state of MRI by significantly decreasing the time required for MRI examinations. Our goal was to use DL to accelerate MRI to allow a 5-minute comprehensive examination of the knee without compromising image quality or diagnostic accuracy. MATERIALS AND METHODS. A DL model for image reconstruction using a variational network was optimized. The model was trained using dedicated multisequence training, in which a single reconstruction model was trained with data from multiple sequences with different contrast and orientations. After training, data from 108 patients were retrospectively undersampled in a manner that would correspond with a net 3.49-fold acceleration of fully sampled data acquisition and a 1.88-fold acceleration compared with our standard twofold accelerated parallel acquisition. An interchangeability study was performed, in which the ability of six readers to detect internal derangement of the knee was compared for clinical and DL-accelerated images. RESULTS. We found a high degree of interchangeability between standard and DL-accelerated images. In particular, results showed that interchanging the sequences would produce discordant clinical opinions no more than 4% of the time for any feature evaluated. Moreover, the accelerated sequence was judged by all six readers to have better quality than the clinical sequence. CONCLUSION. An optimized DL model allowed acceleration of knee images that performed interchangeably with standard images for detection of internal derangement of the knee. Importantly, readers preferred the quality of accelerated images to that of standard clinical images.

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RATIONALE AND OBJECTIVES: The medial plantar proper digital nerve, also called Joplin's nerve, arises from the medial plantar nerve, courses along the medial hallux metatarsophalangeal joint, and can be a source of neuropathic pain due to various etiologies, following acute injury including bunion surgery and repetitive microtrauma. We describe our clinical experience with diagnostic ultrasound assessment of Joplin's neuropathy and technique for ultrasound-guided therapeutic intervention including both injection and cryoablation over a 6-year period. MATERIALS AND METHODS: Retrospective review of all diagnostic studies performed for Joplin's neuropathy and therapeutic Joplin's nerve ultrasound-guided injections and cryoablations between 2012 and 2018 was performed. Indications for therapeutic injection and cryoablation, were recorded. Studies were assessed for sonographic abnormalities related to the nerve and perineural soft tissues. Post-treatment outcomes including immediate pain scores, clinical follow-up, and periprocedural complications were documented. RESULTS: Twenty-four ultrasound-guided procedures were performed, including 15 perineural injections and nine cryoablations. With respect to sonographic abnormalities, nerve thickening (33%) and perineural hypoechoic scar tissue (27%) were the most common findings. The mean pain severity score prior to the therapeutic injection was 6.4/10 (range 4-10) and 0.25/10 (range 0-2) following the procedure; mean follow-up was 26.2 months (range 3-63 months). All of the cryoablation patients experienced sustained pain relief with a mean length follow-up of 3.75 months (range 0.2-10 months). CONCLUSION: Therapeutic injection of Joplin's nerve is a safe and easily performed procedure under ultrasound guidance, with high rates of immediate symptom improvement. For those experiencing a relapse or recurrent symptoms, cryoablation offers an effective secondary potential treatment option.

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