T2-weighted MRI radiomics in high-grade intramedullary osteosarcoma: predictive accuracy in assessing histologic response to chemotherapy, overall survival, and disease-free survival.

OBJECTIVE: To analyze radiomic features obtained from pre-treatment T2-weighted MRI acquisitions in patients with histologically proven intramedullary high-grade osteosarcomas and assess the accuracy of radiomic modelling as predictive biomarker of tumor necrosis following neoadjuvant chemotherapy (NAC), overall survival (OS), and disease-free survival (DFS). MATERIALS AND METHODS: Pre-treatment MRI exams in 105 consecutive patients who underwent NAC and resection of high-grade intramedullary osteosarcoma were evaluated. Histologic necrosis following NAC, and clinical outcome-survival data was collected for each case. Radiomic features were extracted from segmentations performed by two readers, with poorly reproducible features excluded from further analysis. Cox proportional hazard model and Spearman correlation with multivariable modelling were used for assessing relationships of radiomics features with OS, DFS, and histologic tumor necrosis. RESULTS: Study included 74 males, 31 females (mean 32.5yrs, range 15-77 years). Histologic assessment of tumor necrosis following NAC was available in 104 cases, with good response (≥ 90% necrosis) in 41, and poor response in 63. Fifty-three of 105 patients were alive at follow-up (median 40 months, range: 2-213 months). Median OS was 89 months. Excluding 14 patients with metastases at presentation, median DFS was 19 months. Eleven radiomics features were employed in final radiomics model predicting histologic tumor necrosis (mean AUC 0.708 ± 0.046). Thirteen radiomic features were used in model predicting OS (mean concordance index 0.741 ± 0.011), and 12 features retained in predicting DFS (mean concordance index 0.745 ± 0.010). CONCLUSIONS: T2-weighted MRI radiomic models demonstrate promising results as potential prognostic biomarkers of prospective tumor response to neoadjuvant chemotherapy and prediction of clinical outcomes in conventional osteosarcoma.

Bone Tumors: Imaging Features of Common and Rare Benign Entities.

Benign primary bone tumors are far more common than their malignant counterpart and are encountered in everyday practice. Imaging plays a crucial role in recognition of the nonaggressive nature of these lesions, determining the need for further imaging or follow-up. This article reviews the clinical, demographic, and radiological features of some of the more common entities classified as benign or intermediate (locally aggressive) according to the World Health Organization classification of bone tumors.

Preoperative Magnetic Resonance Imaging Accurately Detects the Arthroscopic Comma Sign in Subscapularis Tears.

PURPOSE: To assess the accuracy and reliability of routine preoperative magnetic resonance imaging (MRI) in the detection of the comma sign compared with the gold standard of arthroscopic findings. METHODS AND MATERIALS: Preoperative MRI exams in consecutive patients undergoing arthroscopic subscapularis tendon repair, over a 5-year time frame, were retrospectively reviewed for full-thickness tears of the subscapularis and supraspinatus tendons, fatty atrophy of the subscapularis and supraspinatus muscles, and status of the long head of the biceps tendon. Each case was also evaluated for presence or absence of a comma sign on MRI. Surgical findings served as the diagnostic standard of reference in determination of a comma sign. RESULTS: The study cohort included 45 male and 10 female patients (mean age, 56; range, 32-80 years). A comma sign was present at arthroscopy in 19 patients (34.5%). Interclass and intrarater correlation showed 100% agreement in preoperative assessment of a comma sign on MRI. MRI showed an overall accuracy of 83.6% in diagnosis of a comma sign (sensitivity, 63.2%; specificity, 94.4%; positive predictive value, 85.7%; negative predictive value, 82.9%; positive likelihood ratio, 11.37; negative likelihood ratio, 0.39). No statistically significant association was observed between an arthroscopic comma sign and patient demographics or MRI findings of full-thickness rotator cuff tears, muscle fatty atrophy, or long head of the biceps tendon pathology. CONCLUSIONS: MR imaging illustrates excellent reliability and good specificity and accuracy in detection of the arthroscopic comma sign in the setting of subscapularis tendon tearing. Detection of a comma sign on MRI may be important preoperative planning information in the arthroscopic management of patients with subscapularis tendon tears. LEVEL OF EVIDENCE: Level IV, retrospective diagnostic study.

Imaging features of gluteal in vitro fertilization injection granulomas, with delayed clinical presentation simulating soft tissue sarcoma.

OBJECTIVES: To review the clinical and imaging findings of patients with remote history of intramuscular (IM) in vitro fertilization (IVF) gluteal injections, presenting with signs and symptoms of a possible gluteal soft tissue sarcoma. METHODS AND METHODS: Retrospective review of consecutive patients with a history of prior IVF therapy referred for MRI evaluation of a gluteal soft tissue mass was performed. Six patients were reviewed, with 5 patients meeting study inclusion criteria. Imaging exams (ultrasound n = 3, MRI n = 5) were assessed for lesion location, morphology, and intrinsic imaging characteristics. One case proceeded to percutaneous biopsy with histopathologic correlation. RESULTS: Average patient age was 43 years (range 38-50). Mean time interval between IVF IM injections and MRI was 5.7 years (range 2.2-13 years). Clinical findings included palpable gluteal mass (5/5) and local pain (4/5). Ultrasound showed heterogeneous subcutaneous lesions with varying complex cystic/solid internal echogenicity. On MRI, each case illustrated an irregularly marginated lesion, mean maximal dimension 3.5 cm (range 1.5-5.9 cm), within the deep gluteal subcutaneous fat composed of solitary (1/5) or multifocal (4/5) lobules demonstrating internal areas of high T1 and homogeneous low T2 fat suppressed signal with surrounding peripheral reticular high T2 signal. Correlative histological assessment showed central areas with features of fat necrosis and a peripheral inflammatory rim. CONCLUSIONS: In the setting of prior IVF therapy, imaging features of an irregularly marginated, deep subcutaneous gluteal lesion with inflammatory soft tissue changes surrounding solitary or multifocal areas of loculated fat signal may be seen as an inflammatory response to previous inadvertent subcutaneous injection(s).

Gluteus minimus tendon: MR imaging features and patterns of tendon tearing.

PURPOSE: To highlight the spectrum of pathology and patterns of gluteus minimus tendon tearing observed on MR imaging of the hip. METHODS AND MATERIALS: Retrospective review of consecutive hip MRI exams with findings of gluteus minimus tendon (GMin) pathology. A total of 194 exams in 178 patients (148 female, mean age 61) were reviewed. MRI exams are assessed for GMin: tendinopathy, partial, or complete tendon tears. GMin muscular fatty atrophy, enthesopathic cortical irregularities of the greater trochanter (GT), and peri-trochanteric edema or bursal fluid collections were assessed in all cases. In all cases of complete GMin tendon tearing, position and relationship of GMin tendon were assessed relative to its normal insertion site and adjacent soft tissues. RESULTS: Clinical indications for MR imaging included hip pain (n = 151), and weakness or altered gait (n = 13). Insertional GMin tendinopathy was seen in 72, partial tearing in 81, and complete tendon tearing in 40 cases. Complete tendon tearing without proximal retraction was observed in 38/40 cases with soft tissue continuity visualized between distal tendon fibers and the proximal vastus lateralis muscle. Peri-trochanteric bursal fluid (n = 61), osseous irregularities of the GT (n = 118), and fatty atrophy GMin (n = 102) were statistically associated with partial or complete GMin tendon tearing (p < 0.001). CONCLUSIONS: The spectrum of GMin tendon pathology observed on MR imaging ranges from tendinopathy to complete tears. The majority of complete distal GMin tendon tears from the greater trochanter show continuity of distal tendon fibers with the proximal vastus lateralis, distally tethering and limiting proximal tendon retraction.

Bone Marrow Mesenchymal Stromal Cell Treatment in Patients with Osteoarthritis Results in Overall Improvement in Pain and Symptoms and Reduces Synovial Inflammation.

Patients with late-stage Kellgren-Lawrence knee osteoarthritis received a single intra-articular injection of 1, 10, or 50 million bone marrow mesenchymal stromal cells (BM-MSCs) in a phase I/IIa trial to assess safety and efficacy using a broad toolset of analytical methods. Besides safety, outcomes included patient-reported outcome measures (PROMs): Knee Injury and Osteoarthritis Outcome Score (KOOS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC); contrast-enhanced magnetic resonance imaging (MRI) for cartilage morphology (Whole Organ MRI Scores [WORMS]), collagen content (T2 scores), and synovitis; and inflammation and cartilage turnover biomarkers, all over 12 months. BM-MSCs were characterized by a panel of anti-inflammatory markers to predict clinical efficacy. There were no serious adverse events, although four patients had minor, transient adverse events. There were significant overall improvements in KOOS pain, symptoms, quality of life, and WOMAC stiffness relative to baseline; the 50 million dose achieved clinically relevant improvements across most PROMs. WORMS and T2 scores did not change relative to baseline. However, cartilage catabolic biomarkers and MRI synovitis were significantly lower at higher doses. Pro-inflammatory monocytes/macrophages and interleukin 12 levels decreased in the synovial fluid after MSC injection. The panel of BM-MSC anti-inflammatory markers was strongly predictive of PROMs over 12 months. Autologous BM-MSCs are safe and result in significant improvements in PROMs at 12 months. Our analytical tools provide important insights into BM-MSC dosing and BM-MSC reduction of synovial inflammation and cartilage degradation and provide a highly predictive donor selection criterion that will be critical in translating MSC therapy for osteoarthritis. Stem Cells Translational Medicine 2019;8:746&757.

Imaging of Athletic Injuries of Knee Ligaments and Menisci: Sports Imaging Series.

Acute knee injuries are a common source of morbidity in athletes and if overlooked may result in chronic functional impairment. Magnetic resonance (MR) imaging of the knee has become the most commonly performed musculoskeletal MR examination and is an indispensable tool in the appropriate management of the injured athlete. Meniscal and ligamentous tearing are the most frequent indications for surgical intervention in sports injuries and an understanding of the anatomy, biomechanics, mechanisms of injury, and patterns of injury are all critical to accurate diagnosis and appropriate management. These will be discussed in reference to meniscal tears and injuries of the cruciate ligaments as well as injuries of the posterolateral and posteromedial corners of the knee. (©) RSNA, 2016.

Diffusion tensor imaging of peripheral nerves.

Diffusion tensor imaging (DTI) is a powerful MR imaging technique that can be used to probe the microstructural environment of highly anisotropic tissues such as peripheral nerves. DTI has been used predominantly in the central nervous system, and its application in the peripheral nervous system does pose some challenges related to imaging artifacts, the small caliber of peripheral nerves, and low water proton density. However advances in MRI hardware and software have made it possible to use the technique in the peripheral nervous system and to obtain functional data relating to the effect of pathologic processes on peripheral nerves. This article reviews the imaging principles behind DTI and examines the literature regarding its application in assessing peripheral nerves.

Anterior cruciate ligament reconstruction: MR imaging signs of anterior knee laxity in the presence of an intact graft.

PURPOSE: To determine the accuracy of secondary magnetic resonance (MR) imaging signs of anterior cruciate ligament (ACL) insufficiency in predicting clinical anterior translational knee laxity, in the presence of an intact graft, after ACL reconstruction. MATERIALS AND METHODS: Institutional review board approval was obtained, and the requirement to obtain informed consent was waived. Fifty-two patients with ACL reconstruction and no injury to the contralateral knee were included. Three patients with visible ACL graft tears at MR imaging were excluded. All patients underwent MR imaging of the affected knee, functional assessment with use of the International Knee Documentation Committee (IKDC) score, and arthrometric testing of both the affected and uninjured knee. A side-to-side difference of more than 3 mm at 133 N was considered to be indicative of knee laxity. Two radiologists independently evaluated all MR images for seven signs of anterior knee laxity. The sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) were calculated for each MR imaging sign. RESULTS: Ten patients demonstrated knee laxity at arthrometric testing. Patients with knee laxity at arthrometric testing had significantly lower IKDC scores (P < .03). Sensitivities for all signs were low (0%-50%). Anterior translation of the tibia of more than 7 mm, a posterior cruciate ligament (PCL) angle of less than 100°, and a PCL curvature ratio of more than 0.39 demonstrated high specificity (range, 82%-90%). Uncovering of the posterior horn of the lateral meniscus and the posterior femoral line had a specificity of 97%-100% and a sensitivity of 0%. All signs had a low PPV and high NPV for laxity. All MR imaging signs demonstrated near-perfect interobserver agreement. CONCLUSION: Although MR imaging signs of knee laxity in the presence of an intact ACL graft have a high specificity, the low PPV means that MR imaging is of little value in predicting anterior knee laxity as demonstrated with mechanical testing.

Massive localised lymphoedema: clinical presentation and MR imaging characteristics.

Three morbidly obese women were referred to us with suspected soft-tissue sarcomas. All lesions arose from the medial subcutaneous tissues of the thigh, and were shown to represent massive localised lymphoedema (MLL), a rare condition occurring in morbidly obese adults. MR imaging typically demonstrates a sharply demarcated, pedunculated mass consisting of fat partitioned by fibrous septae surrounded by a thickened dermis. There is oedema both within the mass and tracking along the subcutaneous septae in a "lace-like" fashion outwards from the pedicle, outlining large lobules of fat. Minimal enhancement is observed within the dermis of the lesion following intravenous gadolinium administration. Obesity is a growing problem that is likely to result in an increase in the prevalence of this condition; therefore, familiarity with the radiological appearance is important in establishing a correct diagnosis in this condition that may mimic a soft-tissue sarcoma.

Musculoskeletal sonopathology and ultrasound-guided regional anesthesia.

The use of real-time ultrasound guidance has revolutionized the practice of regional anesthesia. Ultrasound is rapidly becoming the technique of choice for nerve blockade due to increased success rates, faster onset, and potentially improved safety. In the course of ultrasound-guided regional anesthesia, unexpected pathology may be encountered. Such anomalous or pathological findings may alter the choice of nerve block and occasionally affect surgical management. This case series presents a variety of musculoskeletal conditions that may be encountered during ultrasound-guided regional anesthesia practice.

Clinical sonopathology for the regional anesthesiologist: part 2: bone, viscera, subcutaneous tissue, and foreign bodies.

The use of ultrasound to facilitate regional anesthesia is an evolving area of clinical, education, and research interests. As our community's experience grows, it has become evident that anesthesiologists performing "routine" ultrasound-guided blocks may very well be confronted with atypical or even pathologic anatomy. As an educational resource for anesthesiologists, the following articles present examples of common sonopathology that may be encountered during ultrasound-guided regional anesthesia. This present article describes sonopathology related to bone, viscera, and subcutaneous tissue.

Clinical sonopathology for the regional anesthesiologist: part 1: vascular and neural.

The use of ultrasound to facilitate regional anesthesia is an evolving area of clinical, education, and research interests. As our community's experience grows, it has become evident that anesthesiologists performing "routine" ultrasound-guided blocks may very well be confronted with atypical or even pathologic anatomy. As an educational resource for anesthesiologists, the following articles present examples of common sonopathology that may be encountered during ultrasound-guided regional anesthesia. This present article describes sonopathology related to blood vessels and nerves.

Anterior cruciate ligament reconstruction by using bioabsorbable femoral cross pins: MR imaging findings at follow-up and comparison with clinical findings.

PURPOSE: To determine the frequency of imaging findings and complications related to bioabsorbable femoral cross pins at follow-up magnetic resonance (MR) imaging studies after anterior cruciate ligament (ACL) reconstruction and compare these MR imaging findings with clinical evaluation findings. MATERIALS AND METHODS: The institutional review board approved this retrospective study, and informed consent was waived. Follow-up MR imaging studies (average, 26 months after surgery) in 218 patients with prior ACL reconstruction were retrospectively reviewed. Cross-pin fracture, posterior transcortical breach, migration, resorption, and lateral prominence of cross pins, as well as the cross-pin angle relative to the transepicondylar line, were investigated on MR images. The clinical evaluation included Lachman, anterior drawer, and pivot shift tests, as well as assessment for joint tenderness. RESULTS: Fracture, posterior transcortical breach, migration, and lateral prominence of cross pins were excluded from analysis when at least one cross pin was completely resorbed (n = 16 patients). Forty-five fractured cross pins were seen in 35 (17%) of 202 patients. The posterior femoral cortex was breached in 57 (28%) of 202 patients. Migration of fractured pin fragments occurred in 12 (6%) of 202 patients. There was a significant relationship between fractures and posterior breach of cross pins (P = .001), as well as between cross-pin angles and fractures (P = .002). Both cross pins were completely resorbed in 12 (6%) of 218 patients (average time since surgery, 53 months; range, 8-92 months). No significant association was found between any MR imaging finding related to cross pins and clinical test findings. CONCLUSION: Fracture and posterior transcortical breach of bioabsorbable femoral cross pins, commonly seen at follow-up MR imaging studies, do not correlate with clinical findings of joint instability or pain. Posteriorly angulated cross pins and posterior transcortical breach are significantly associated with cross-pin fractures.

Magnetic resonance imaging features of osseous manifestations of early acquired syphilis.

We report the case of a 64-year-old man who initially presented with a maculopapular rash followed several weeks later by bilateral shin pain and infiltrative cutaneous lesions over the lower legs. The plain radiographs were not contributory, and the patient was referred for a whole-body bone scan, which demonstrated multifocal osseous lesions, including such lesions in the lower legs, skull and facial bones. Magnetic resonance imaging (MRI) demonstrated numerous small tibial and fibular nodular lesions involving the medullary cavity and the cortex. A diagnosis of acquired syphilis was made, based on skin biopsy. Results of serological testing were consistent with recent infection. The patient was treated with intramuscular injection of penicillin, and follow-up MRI demonstrated gradual resolution of the osseous lesions. Bone involvement is a relatively rare manifestation of early acquired syphilis. Although the plain radiographic features of the bony changes in acquired syphilis are well documented, there have been no reports of the magnetic resonance imaging findings in the appendicular skeleton.

Comparison of 1.0-T extremity MR and 1.5-T conventional high-field-Strength MR in patients with rheumatoid arthritis.

PURPOSE: To prospectively determine the comparability of 1.0-T extremity magnetic resonance (MR) imaging and 1.5-T conventional MR for the evaluation of the hand and wrist in assessment of patients with rheumatoid arthritis (RA). MATERIALS AND METHODS: Institutional ethics approval and written informed consent were obtained. Thirty-two patients (30 women, two men; mean age, 52 years) with RA twice underwent MR of either the most symptomatic hand (n = 21) or wrist (n = 11), once performed with a 1.0-T extremity MR system and once with a 1.5-T conventional MR system. The MR examinations were independently assessed by two radiologists blinded to imaging platform and patient clinical information for erosions, synovitis, and bone marrow edema (BME), according to the Rheumatoid Arthritis MR Imaging Score (RAMRIS). One radiologist reevaluated all cases a second time to determine the intraobserver variability for each system. Patient comfort was assessed with a questionnaire. Intraclass correlation coefficients (ICCs) and smallest detectable differences (SDDs) were measured. RESULTS: ICCs for intermachine agreement were 0.97-0.99 for erosions, 0.88-0.97 for synovitis, and 0.98-0.99 for BME for both readers. The SDDs between the two systems, expressed as a percentage of the maximum score, ranged from 3.3% to 12.2% for erosions, from 7.4% to 14.8% for synovitis, and from 5% to 9.9% for BME for both readers. ICCs for interreader agreement ranged from 0.69 to 0.99 and for intrareader agreement, from 0.88 to 0.99. There were substantial differences in the subjective patient assessment of confinement, system noise, and difficulty with immobilization, and 95.8% of patients preferred examinations performed with extremity MR. CONCLUSION: The 1.0-T extremity MR system demonstrates synovial and osseous changes in RA equally as well as a 1.5-T conventional MR system and is preferred by patients.

Accessory muscles: anatomy, symptoms, and radiologic evaluation.

A wide array of supernumerary and accessory musculature has been described in the anatomic, surgical, and radiology literature. In the vast majority of cases, accessory muscles are asymptomatic and represent incidental findings at surgery or imaging. In some cases, however, accessory muscles may produce clinical symptoms. These symptoms may be related to a palpable swelling or may be the result of mass effect on neurovascular structures, typically in fibro-osseous tunnels. In cases in which an obvious cause for such symptoms is not evident, recognition and careful evaluation of accessory muscles may aid in diagnosis and treatment.

Magnetic resonance imaging of joint replacements.

An increasing number of joint replacements are being performed annually. Complications of joint arthroplasty are diverse and may involve the hardware as well as osseous and soft tissue components. Although modalities such as conventional radiography and scintigraphy remain the mainstay of radiological investigation, in some cases these traditional methods of imaging may be negative or underestimate the extent of disease. Magnetic resonance imaging (MRI) has been considered of limited benefit following arthroplasty because of severe image degradation caused by metallic components. However, with modification of pulse sequences, artifact reduction and improved visualization of periprosthetic tissues are achievable, enabling a comprehensive assessment of articular and nonarticular pathologies. The common artifacts in the presence of orthopedic hardware, optimization of pulse sequences to minimize metal-related artifacts, and the clinical uses of MRI following joint replacement, particularly with regard to total hip arthroplasty, total knee arthroplasty, and shoulder arthroplasty, are reviewed.