US for Traumatic Nerve Injury, Entrapment Neuropathy, and Imaging-guided Perineural Injection.

US is commonly performed to help diagnose traumatic peripheral nerve injury and entrapment neuropathy, particularly with superficial nerves, where higher spatial resolution provides an advantage over MRI. Other advantages of US include dynamic evaluation, easy contralateral comparison, fewer implant contraindications, less artifact from ferromagnetic debris, and facile needle guidance for perineural injections. The authors review peripheral nerve US for traumatic peripheral nerve injury with an emphasis on injury grading and entrapment neuropathy and describe best-practice techniques for US-guided perineural injections while highlighting specific techniques and indications. Online supplemental material is available for this article. ©RSNA, 2022.

Magnetic Resonance of Normal Variants of the Pediatric Knee.

Accurate diagnosis and management of pediatric patients undergoing magnetic resonance (MR) imaging necessitates familiarity with the normal changes of skeletal maturation and the spectrum of normal variation seen in children. This article reviews key patterns of normal bone and cartilage development. The most common and important variants of bone, cartilage, and soft tissue structures encountered on pediatric MR studies are discussed. Emphasis is placed on those variants that can be mistaken for pathology and those that may predispose to the development of symptoms.

Pre-treatment MRI of leukaemia and lymphoma in children: are there differences in marrow replacement patterns on T1-weighted images?

OBJECTIVES: To investigate the prevalence and distribution of specific marrow patterns on pre-treatment magnetic resonance imaging (MRI) examinations in children with leukaemia and lymphoma and with respect to the anatomic location. MATERIALS AND METHODS: This retrospective IRB-approved and HIPAA-compliant study included children with leukaemia or lymphoma who underwent pre-treatment MRI examinations over 18 years (between 1 January 1995 and 31 August 2013). Two radiologists blinded to the clinical diagnosis reviewed each study to determine the presence or absence of abnormal marrow signal and, when present, sub-categorised the pattern into diffuse, patchy, or focal abnormal marrow. Chi-square and Fisher's exact tests were used to compare marrow patterns between leukaemia and lymphoma. RESULTS: The study included 50 children (32 males and 18 females; mean age 9.5 ± 5.3 years) with 54 MRI examinations (27 leukaemia and 27 lymphoma) that included 26 spine and 28 non-spine studies. Marrow replacement was present on 43 (80%) studies, significantly more common with leukaemia than with lymphoma (p = 0.039). The diffuse replacement pattern was significantly more common with leukaemia when compared to lymphoma (p < 0.001) and the focal pattern was only observed with lymphoma. In the spine, the diffuse pattern was observed with lymphoma (3/14, 21%). All patients with leukaemia and MRI outside of the spine showed marrow involvement. CONCLUSION: Marrow replacement is common on MRI from children with leukaemia and lymphoma. A diffuse pattern was significantly associated with leukaemia on studies outside of the spine and a focal pattern was only observed with lymphoma, independently of the anatomic location. KEY POINTS: • Bone marrow replacement on pre-treatment MRI examinations in children with leukaemia and lymphoma was observed in 93% (25/27) and 67% (18/27), respectively. • Diffuse pattern of marrow replacement was significantly more common in leukaemia even though this pattern was also observed with lymphoma on the spine MRI studies. • Focal pattern of marrow replacement was present only with lymphoma and not with leukaemia regardless of the anatomic location.

Overuse Injuries of the Shoulder.

This article discusses the most common and important overuse injuries of the shoulder with attention to MR imaging and ultrasound findings. Pathologic conditions occurring in athletes and nonathletes are included, with review of relevant anatomy, predisposing factors, and treatment considerations. Specific overuse injuries involving the rotator cuff, long head of the biceps tendon, and subacromial-subdeltoid bursa are reviewed. Impingement syndromes of the shoulder, Little Leaguer's shoulder, and stress-induced distal clavicular osteolysis are also discussed.

Primary Rosai-Dorfman Disease of Bone: A Report of Two Cases.

Rosai-Dorfman disease (RDD), sometimes known as sinus histiocytosis with massive lymphadenopathy, is a rare histiocytic disorder that most commonly presents as painless, massive cervical lymphadenopathy in young adults. Extranodal disease can occur in up to 40% of patients but primary involvement of bone is rare. We present two cases of primary RDD of bone: one case of multifocal osseous RDD presenting as a painful lesion in the elbow, and one case of a solitary osseous lesion presenting as a painful lesion in the wrist.

Orthopaedic Fixation Devices Used in Children: A Radiologist's Guide.

Fractures are common in children with some requiring surgical reduction and fixation to maintain anatomical alignment. Although various surgical techniques and principles are shared between children and adults, certain unique considerations in children can influence the surgical approach and device selection. In particular, for skeletally immature children, it is of utmost importance to protect certain critical open growth plates because permanent injury can produce severe growth disturbances. The often robust healing response and potential limited patient compliance can also influence the treatment algorithm and decision making. Commonly encountered orthopaedic fixation devices, including screws, intramedullary devices, and plates, are reviewed with an emphasis on their mechanism and application in children. Additional miscellaneous devices that are commonly used to treat malalignment and guide bone growth including epiphysiodesis plates, proximal femur osteotomy plates, and spinal magnetic growing rods are also reviewed. The goal of this article is to provide a basic understanding of the principles and mechanisms of different types of pediatric orthopaedic devices and thereby improve the radiologist's diagnostic confidence and allow better anticipation of complications.

Sports and the Growing Musculoskeletal System: Sports Imaging Series.

Increased youth participation in sports has resulted in increased injury tolls due to shifts toward participation in competitive sports at earlier ages, increased training intensity and competition schedules, as well as specialization into one sport. The physiology of the growing musculoskeletal system makes the growing athlete particularly vulnerable to specific types of injuries. Radiologists must understand the differences between pediatric and adult athletes to recognize the particular injuries to which these young athletes are prone. Imaging and pertinent clinical details of major representative acute and overuse injuries characteristic to pediatric athletes will be discussed. © 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.

A biomechanical approach to interpreting magnetic resonance imaging of knee injuries.

This article discusses common injury mechanisms and the subsequent constellation of magnetic resonance (MR) imaging findings in the knee following trauma in the context of instability, as distinguished by the degree of knee flexion and tibial rotation at the time of initial injury, in addition to the direction and magnitude of the responsible force vectors. Using 3-dimensional imaging, common injury mechanisms are illustrated and correlated with MR imaging findings of the resulting osteochondral, ligamentous, meniscal, and musculotendinous lesions. The most common classification and grading systems for these individual lesions and their subsequent treatment implications are discussed.

Magnetic resonance imaging of the pediatric knee.

In pediatric patients, the high resolution and excellent soft-tissue contrast of magnetic resonance (MR) imaging allows for complete evaluation of osseous and soft-tissue structures around the knee joint, and its lack of ionizing radiation makes it a preferred modality for advanced imaging. Older children and adolescents are most commonly imaged to evaluate athletic and traumatic injuries, whereas in infants and school age children MR imaging is used to evaluate developmental conditions such as Blount disease or assess for causes of atraumatic pain such as infection or inflammatory arthritis. A thorough understanding of normal skeletal development is necessary to avoid misdiagnoses.

Imaging of traumatic injuries to the hip.

Traumatic injuries of the hip are an increasingly common cause of morbidity and mortality. These injuries can be grouped into fairly discrete patterns including femoral head fractures and hip dislocations, femoral neck fractures, greater trochanteric fractures, intertrochanteric fractures, subtrochanteric fractures, and soft tissue injuries. For each of these entities, specific features provide helpful diagnostic, prognostic, and therapeutic information. Femoral head fractures and hip dislocations commonly occur in combination. Fractures of the femoral head confer an increased risk of avascular necrosis of the femoral head. Rare variations of hip dislocations exist including an irreducible posterior dislocation and multiple varieties of anterior dislocation. Femoral neck fractures, which can occur in younger individuals during high-energy trauma and occur with far greater frequency in older osteoporotic individuals with low-energy trauma, are commonly encountered radiographically but can also be radiographically occult. Similarly, greater trochanter fractures have a high frequency of radiographically occult distal extension. As is the case with many other femur fracture types, intertrochanteric and subtrochanteric fractures are less stable and more prone to developing nonunion the more comminuted and extensive they are. All of these injury patterns are frequently encountered in the emergency setting. The ability to distinguish between different types of injury and the knowledge of key discriminating and prognostic features are a must for the interpreting radiologist.

Magnetic resonance imaging and arthroscopic appearance of the menisci of the knee.

The menisci are critical for normal function of the knee, providing shock absorption and load transmission that reduce stress on the articular cartilage. When torn, a meniscus may require surgery to restore function, reduce pain, and eliminate mechanical symptoms. Patterns of meniscal tears include longitudinal and bucket-handle, which are often reparable; and horizontal, radial, vertical flap, horizontal flap, and complex. Root tears are usually radial and occur in the posterior roots. When reviewing magnetic resonance images, one must be aware of normal variants and imaging pitfalls that may simulate pathology.

Percutaneous image-guided cryoablation of painful metastases involving bone: multicenter trial.

BACKGROUND: This study sought to describe the results of a single-arm multicenter clinical trial using image-guided percutaneous cryoablation for the palliation of painful metastatic tumors involving bone. METHODS: Over a 44-month period, 61 adult patients with 1 or 2 painful bone metastases with a score of 4 or more on a scale of 0 to 10 (≥4/10) worst pain in a 24-hour period who had failed or refused conventional treatment were treated with percutaneous image-guided cryoablation. Patient pain and quality of life was measured using the Brief Pain Inventory prior to treatment, 1 and 4 days after the procedure, weekly for 4 weeks, and every 2 weeks thereafter for a total of 6 months. Patient analgesic use was also recorded at these same follow-up intervals. Complications were monitored. Analysis of the primary endpoint was undertaken via paired comparison procedures. RESULTS: A total of 69 treated tumors ranged in size from 1 to 11 cm. Prior to cryoablation, the mean score for worst pain in a 24-hour period was 7.1/10 with a range of 4/10 to 10/10. At 1, 4, 8, and 24 weeks after treatment, the mean score for worst pain in a 24-hour period decreased to 5.1/10 (P < .0001), 4.0/10 (P < .0001), 3.6/10 (P < .0001), and 1.4/10 (P < .0001), respectively. One of 61 (2%) patients had a major complication with osteomyelitis at the site of ablation. CONCLUSIONS: Percutaneous cryoablation is a safe, effective, and durable method for palliation of pain due to metastatic disease involving bone.

Is there an association between superolateral Hoffa fat pad edema on MRI and clinical evidence of fat pad impingement?

OBJECTIVE: Patients with symptomatic Hoffa fat pad impingement often exhibit fat pad edema on MRI. We studied two patient groups to determine the association between MRI fat pad edema and clinical symptoms of Hoffa fat pad impingement. MATERIALS AND METHODS: We studied 34 consecutive patients with an MRI diagnosis of fat pad edema and no injury in the prior year (group 1) and 47 consecutive patients with a knee MRI examination and no injury in the prior year (group 2). Two sports medicine physicians reviewed the clinical records to confirm or exclude symptomatic fat pad impingement. Two musculoskeletal radiologists independently scored 12 Hoffa fat pad locations for the presence of edema, noting the epicenter. RESULTS: Seventeen of the 34 patients in group 1 had clinical symptoms of fat pad impingement, with all 34 having fat pad edema. There was no association between clinical fat pad impingement and fat pad edema in any specific location (p > 0.183), but patients with fat pad impingement had a greater number of regions of edema (p = 0.005, 0.026 for two observers). In group 2, all four patients with clinical fat pad impingement had MRI fat pad edema, but 38 of the 43 patients without clinical impingement had MRI fat edema; 11 of the 38 had edema centered in the superolateral fat pad. CONCLUSION: Edema is present on MRI in the superolateral region of Hoffa fat pad in patients with clinical fat pad impingement. However, such edema can also be present in patients without symptoms of fat pad impingement.

Upper extremity injuries in young athletes.

Injuries are becoming increasingly prevalent in pediatric athletes. Many of these injuries are diagnosed clinically and do not require imaging for diagnosis, but the sheer increase in numbers of injuries means that radiologists are evaluating more of them. Some injuries that young athletes sustain are simply due to trauma, such as falls, and may be experienced outside sports just as easily; however, others are peculiar to athletic activities. Many of the latter are chronic overuse injuries as opposed to acute injuries and have characteristic appearances. The types of injuries young athletes incur often change based on the stage of skeletal maturity of the patient, and it serves the radiologist well to keep in mind the typical appearances expected at different ages.

Evaluation of the menisci of the knee joint using three-dimensional isotropic resolution fast spin-echo imaging: diagnostic performance in 250 patients with surgical correlation.

OBJECTIVE: To compare the diagnostic performance of FSE-Cube, a three-dimensional isotropic resolution intermediate-weighted fast spin-echo sequence, with a routine magnetic resonance (MR) protocol at 3.0 T for detecting surgically confirmed meniscal tears of the knee joint in a large patient population. METHODS: FSE-Cube was added to a routine MR protocol performed at 3.0 T on 250 patients who underwent subsequent knee arthroscopy. Three radiologists independently used FSE-Cube during one review and the routine MR protocol during a second review to detect medial and lateral meniscal tears. Using arthroscopy as the reference standard, the sensitivity and specificity of FSE-Cube and the routine MR protocol for detecting meniscal tears were determined for all readers combined. McNemar's tests were used to compare diagnostic performance between FSE-Cube and the routine MR protocol. RESULTS: FSE-Cube and the routine MR protocol had similar sensitivity (95.5%/95.3% respectively, P = 0.94) and similar specificity (69.8%/74.0% respectively, P = 0.10) for detecting 156 medial meniscal tears. FSE-Cube had significantly lower sensitivity than the routine MR protocol (79.4%/85.0% respectively, P < 0.05) but similar specificity (83.9%/82.2% respectively, P = 0.37) for detecting 89 lateral mensical tears. For lateral meniscal tears, FSE-Cube had significantly lower sensitivity (P < 0.05) than the routine MR protocol for detecting 19 root tears but similar sensitivity (P = 0.17-1.00) for detecting all other tear locations and types. CONCLUSION: FSE-Cube had diagnostic performance similar to a routine MR protocol for detecting meniscal tears except for a significantly lower sensitivity for detecting lateral meniscal tears, which was mainly attributed to decreased ability to identify lateral meniscus root tears.

MR arthrography of the hip: comparison of IDEAL-SPGR volume sequence to standard MR sequences in the detection and grading of cartilage lesions.

PURPOSE: To compare the diagnostic performance of iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL)-spoiled gradient-recalled echo (SPGR) with that of standard magnetic resonance (MR) arthrography sequences for detecting and grading cartilage lesions within the hip joint during MR arthrography. MATERIALS AND METHODS: Following institutional review board approval, 67 consecutive hip MR arthrograms were retrospectively reviewed independently by three musculoskeletal radiologists and one musculoskeletal fellow. IDEAL-SPGR images and the two-dimensional images, the latter from the routine MR arthrography protocol, were evaluated at separate sittings to grade each articular surface of the hip joint. By using arthroscopy as the reference standard, the sensitivity and specificity of the two techniques for detecting and grading cartilage lesions were determined. The McNemar test was used to compare diagnostic performance. Interreader agreement was calculated using Fleiss κ values. RESULTS: For all readers and surfaces combined, the sensitivity and specificity for detecting cartilage lesions was 74% and 77%, respectively, for IDEAL-SPGR and 70% and 84%, respectively, for the routine MR arthrography protocol. IDEAL-SPGR had similar sensitivity (P = .12) to and significantly lower specificity (P < .001) than the routine MR arthrography protocol for depicting cartilage lesions. When analyzing the differences in sensitivity and specificity by reader, the two readers who had experience with IDEAL-SPGR had no significant difference in sensitivity and specificity for detecting cartilage lesions between the two sequences. For all readers and surfaces combined, IDEAL-SPGR had a higher accuracy in correctly grading cartilage lesion (P = .012-.013). Interobserver agreement for detecting cartilage lesions did not differ between the two techniques. CONCLUSION: IDEAL-SPGR had similar sensitivity and significantly lower specificity for detecting cartilage lesions and higher accuracy for grading cartilage lesions than did a routine MR arthrography protocol; the lower specificity of IDEAL-SPGR for detecting cartilage lesions was not seen in experienced readers.