SSR white paper: guidelines for utilization and performance of direct MR arthrography.

OBJECTIVE: Direct magnetic resonance arthrography (dMRA) is often considered the most accurate imaging modality for the evaluation of intra-articular structures, but utilization and performance vary widely without consensus. The purpose of this white paper is to develop consensus recommendations on behalf of the Society of Skeletal Radiology (SSR) based on published literature and expert opinion. MATERIALS AND METHODS: The Standards and Guidelines Committee of the SSR identified guidelines for utilization and performance of dMRA as an important topic for study and invited all SSR members with expertise and interest to volunteer for the white paper panel. This panel was tasked with determining an outline, reviewing the relevant literature, preparing a written document summarizing the issues and controversies, and providing recommendations. RESULTS: Twelve SSR members with expertise in dMRA formed the ad hoc white paper authorship committee. The published literature on dMRA was reviewed and summarized, focusing on clinical indications, technical considerations, safety, imaging protocols, complications, controversies, and gaps in knowledge. Recommendations for the utilization and performance of dMRA in the shoulder, elbow, wrist, hip, knee, and ankle/foot regions were developed in group consensus. CONCLUSION: Although direct MR arthrography has been previously used for a wide variety of clinical indications, the authorship panel recommends more selective application of this minimally invasive procedure. At present, direct MR arthrography remains an important procedure in the armamentarium of the musculoskeletal radiologist and is especially valuable when conventional MRI is indeterminant or results are discrepant with clinical evaluation.

Distal Radioulnar Joint: Normal Anatomy, Imaging of Common Disorders, and Injury Classification.

The distal radioulnar joint (DRUJ) is the distal articulation between the radius and ulna, acting as a major weight-bearing joint at the wrist and distributing forces across the forearm bones. The articulating surfaces are the radial sigmoid notch and ulnar head, while the ulnar fovea serves as a critical attachment site for multiple capsuloligamentous structures. The DRUJ is an inherently unstable joint, relying heavily on intrinsic and extrinsic soft-tissue stabilizers. The triangular fibrocartilage complex (TFCC) is the chief stabilizer, composed of the central disk, distal radioulnar ligaments, ulnocarpal ligaments, extensor carpi ulnaris tendon subsheath, and ulnomeniscal homologue. TFCC lesions are traditionally classified into traumatic or degenerative on the basis of the Palmer classification. The novel Atzei classification is promising, correlating clinical, radiologic, and arthroscopic findings while providing a therapeutic algorithm. The interosseous membrane and pronator quadratus are extrinsic stabilizers that offer a minor contribution to the joint's stability in conjunction with the joints of the wrist and elbow. Traumatic and overuse or degenerative disorders are the most common causes of DRUJ dysfunction, although inflammatory and developmental abnormalities also occur. Radiography and CT are used to evaluate the integrity of the osseous constituents and joint alignment. US is a useful screening tool for synovitis in the setting of TFCC tears and offers dynamic capabilities for detecting tendon instability. MRI allows simultaneous osseous and soft-tissue evaluation and is not operator dependent. Arthrographic CT or MRI provides a more detailed assessment of the TFCC, which aids in treatment and surgical decision making. The authors review the pertinent anatomy and imaging considerations and illustrate common disorders affecting the DRUJ. Online supplemental material is available for this article. © RSNA, 2022.

Mammary-type myofibroblastoma of the thigh mimicking liposarcoma.

Myofibroblastoma is a rare tumor that was originally described in the breast but has since been found in extra-mammary locations, where it been renamed mammary-type myofibroblastoma (MTM). We describe a case of MTM occurring in the anterior compartment of the thigh, which was initially interpreted as a possible a liposarcoma on MRI. Two subsequent biopsy samples and eventual excision revealed the tumor to have the characteristic pathology of MTM. This benign tumor, albeit rare, needs to be considered in the imaging differential diagnosis of fat containing deep soft tissue masses of the extremity.

Subperiosteal chondromyxoid fibroma: a rare case involving the humeral diaphysis.

Initially described, in 1948, as a tumor that could be mistaken with chondrosarcoma at histopathology, chondromyxoid fibroma is now a well-recognized entity. Surface-type chondromyxoid fibroma, however, remains an extremely rare occurrence. We present a case of a 55-year-old woman, who experienced right arm pain for 5 years. After unsuccessful treatment for presumed thoracic outlet syndrome, MRI revealed a large mass abutting the anteromedial cortex of the distal humeral diaphysis in a subperiosteal location. Further characterization was made with radiography, CT, and bone scan, which were followed by ultrasound-guided biopsy. Although histopathologic features were suggestive of chondromyxoid fibroma, the diagnosis remained somewhat uncertain initially due to the very unusual location involving the diaphysis of the humerus. Surgical resection was performed, and subsequent histopathologic analysis confirmed the diagnosis of chondromyxoid fibroma. Despite being a rare entity, surface-type chondromyxoid fibroma would need to be considered in the differential when dealing with expansile surface diaphyseal lesions.

The prevalence and characteristics of osseous erosions associated with parameniscal cysts on knee MRI.

OBJECTIVES: To determine the prevalence and characteristics of erosions associated with parameniscal cysts (PMCs) and to evaluate the profile of the associated meniscal tears MATERIALS AND METHODS: PACS database was reviewed for knee MRI scans performed over a 5-year period identifying those with PMCs in patients aged 18 years and above. The scans with PMCs were evaluated for the presence of associated osseous erosions. These erosions and PMCs were then analyzed. RESULTS: The search revealed 6773 knee MRI examinations, of which 555 had confirmed PMCs. There were 7 PMC-associated erosions for a prevalence of 1.3% (95% CI 0.6, 2.6). All erosions involved the proximal tibia. Three of 7 erosions had underlying marrow edema, and 4 out of 7 had an overhanging margin. The mean dimension of all PMCs was 13 mm (SD = 11). The mean dimension of PMCs associated with erosions was 38 mm (SD = 22), while that of PMCs without erosions was 12 mm (SD = 10) (P < 0.001, Wilcoxon rank sum test). Ninety-three percent (95% CI 90.5, 94.8) of PMCs had associated meniscal tears, most commonly of the horizontal type (57%). All PMCs with underlying erosions were associated with meniscal tears, most commonly complex type tears (5/7). CONCLUSION: Erosions can rarely be associated with contiguous parameniscal cysts (PMCs). These cysts are significantly larger compared with those without underlying erosions.

Accessory anterolateral talar facet: analysis of the morphologic features on MRI.

PURPOSE: To analyze the morphologic features of accessory anterolateral talar facet (AALTF) on MRI that can assist in detecting this entity, identify any associated structural changes and also define its MRI prevalence. METHODS: Two radiologists retrospectively evaluated 140 ankle MRI scans for the presence of AALTF, complimentary anterior calcaneal extension facet and angle of Gissane measurement. One observer evaluated the scans for other structural details including AALTF length, cartilage thickness, bone marrow edema, hind foot coalition and talar beaking. RESULTS: There was a good inter-observer agreement for the detection of AALTF on MRI (Kappa = 0.64). AALTF was present in 33 out of 140 (23.6%) scans. There was no significant difference in the prevalence of AALTF between male and female subjects (P = 0.71). No significant difference in age between those with and those without AALTF (P = 0.96). Angle of Gissane was significantly smaller in ankles with AALTF (P = 0.0367, observer 1 and 0.0003, observer 2). AALTF had a mean length of 7 mm and was covered with cartilage in 25/33 (75.8%) with mean cartilage thickness of 1.4 mm. Complimentary cartilage covered anterior calcaneal facet was demonstrated in 10/33 (30.3%) and had a mean cartilage thickness of 2.5 mm. Talar beaking was more prevalent in ankles with AALTF showing an anterior calcaneal extension facet than those without the latter feature (P = 0.02). CONCLUSION: AALTF is a frequently observed feature on ankle MRI, with good inter-observer reliability for its detection. When present, it is often opposed by a cartilage covered anterior calcaneal extension facet, which can be associated with talar beaking.

2018 Frank Stinchfield Award: Spinopelvic Hypermobility Is Associated With an Inferior Outcome After THA: Examining the Effect of Spinal Arthrodesis.

BACKGROUND: Many patients undergo both THA and spinal arthrodesis, and those patients may not fare as well as those who undergo one procedure but not the other. The mechanisms of how spinal arthrodesis affects patient function after THA remain unclear. QUESTIONS/PURPOSES: The aims of our study were to (1) determine how patient-reported outcome measures (PROMs), including the Oxford hip score as well as dislocations and complications compare after THA between patients with and without spinal arthrodesis; (2) characterize sagittal pelvic changes in these patients that occur when moving between different functional positions and test for differences between patients with and without spinal arthrodesis; and (3) assess whether differences in sagittal pelvic dynamics are associated with PROMs, complications, and dislocations after THA. METHODS: In this case-control study, we identified 42 patients (60 hips) who had undergone both THA and spinal arthrodesis between 2002 and 2016 and who were available for followup at a minimum of 12 months (mean, 6 ± 5 years) after the later of the two procedures. These cases were case-control-matched for age, gender, and body mass index with 42 patients (60 hips) who underwent only THA and had no known spinal pathology. All patients completed PROMs, including the Oxford hip score, and underwent four radiographs of the pelvis and spinopelvic complex in three positions (supine, standing, and deep-seated). Cup orientation and various spinopelvic parameters, including pelvic tilt and pelvic-femoral angle, were measured. The difference in pelvic tilt between standing and seated allowed for patient classification based on spinopelvic mobility into normal (± 10°-30°), stiff (< ± 10°) or hypermobile (> ± 30°) groups. RESULTS: Compared with the THA-only group, the THA-spinal arthrodesis group had inferior PROMs (Oxford hip score, 33 ± 10 versus 43 ± 6; p < 0.001) and more surgery-related complications (such as dislocation, loosening, periprosthetic fracture or infection, psoas irritation) (12 versus 3; p = 0.013), especially dislocation (5 versus 0; p = 0.023). We detected no difference in change of pelvic tilt between supine and standing positions between the groups. When standing, patients undergoing THA-spinal arthrodesis had greater pelvic tilt (25° ± 11° versus 17° ± 8°; p < 0.001) and the hip was more extended (193° ± 22° versus 185° ± 30°; p = 0.012). We found that patients undergoing THA-spinal arthrodesis were more likely to have spinopelvic hypermobility (12 of 42 versus three of 42; odds ratio, 5.2; p = 0.02) with anterior tilting of the pelvis. Of all biomechanical parameters, only spinopelvic hypermobility was associated with inferior PROMs (Oxford hip score, 35 ± 9 versus 40 ± 7 in normal mobility; p = 0.049) and was also present in dislocating hips that underwent revision despite acceptable cup orientation. CONCLUSIONS: In patients with spinal arthrodesis who have undergone THA, spinopelvic hypermobility is associated with inferior outcomes, including hip instability. Spinopelvic hypermobility should be routinely assessed because these patients may have a narrow zone of optimum cup orientation that would require new technology to define and assist the surgeon in obtaining it.Level of Evidence Level III, therapeutic study.

Development of RAD-Score: A Tool to Assess the Procedural Competence of Diagnostic Radiology Residents.

OBJECTIVE: The purpose of this study is to develop a tool to assess the procedural competence of radiology trainees, with sources of evidence gathered from five categories to support the construct validity of tool: content, response process, internal structure, relations to other variables, and consequences. SUBJECTS AND METHODS: A pilot form for assessing procedural competence among radiology residents, known as the RAD-Score tool, was developed by evaluating published literature and using a modified Delphi procedure involving a group of local content experts. The pilot version of the tool was tested by seven radiology department faculty members who evaluated procedures performed by 25 residents at one institution between October 2014 and June 2015. Residents were evaluated while performing multiple procedures in both clinical and simulation settings. The main outcome measure was the percentage of residents who were considered ready to perform procedures independently, with testing conducted to determine differences between levels of training. RESULTS: A total of 105 forms (for 52 procedures performed in a clinical setting and 53 procedures performed in a simulation setting) were collected for a variety of procedures (eight vascular or interventional, 42 body, 12 musculoskeletal, 23 chest, and 20 breast procedures). A statistically significant difference was noted in the percentage of trainees who were rated as being ready to perform a procedure independently (in postgraduate year [PGY] 2, 12% of residents; in PGY3, 61%; in PGY4, 85%; and in PGY5, 88%; p < 0.05); this difference persisted in the clinical and simulation settings. User feedback and psychometric analysis were used to create a final version of the form. CONCLUSION: This prospective study describes the successful development of a tool for assessing the procedural competence of radiology trainees with high levels of construct validity in multiple domains. Implementation of the tool in the radiology residency curriculum is planned and can play an instrumental role in the transition to competency-based radiology training.

Magnetic Resonance Imaging in Patients With Mechanical Low Back Pain Using a Novel Rapid-Acquisition Three-Dimensional SPACE Sequence at 1.5-T: A Pilot Study Comparing Lumbar Stenosis Assessment With Routine Two-Dimensional Magnetic Resonance Sequences.

PURPOSE: To minimize the burden of overutilisation of lumbar spine magnetic resonance imaging (MRI) on a resource-constrained public healthcare system, it may be helpful to image some patients with mechanical low-back pain (LBP) using a simplified rapid MRI screening protocol at 1.5-T. A rapid-acquisition 3-dimensional (3D) SPACE (Sampling Perfection with Application-optimized Contrasts using different flip angle Evolution) sequence can demonstrate common etiologies of LBP. We compared lumbar spinal canal stenosis (LSCS) and neural foraminal stenosis (LNFS) assessment on 3D SPACE against conventional 2-dimensional (2D) MRI. METHODS: We prospectively performed 3D SPACE and 2D spin-echo MRI sequences (axial or sagittal T1-weighted or T2-weighted) at 1.5-T in 20 patients. Two blinded readers assessed levels L3-4, L4-5 and L5-S1 using: 1) morphologic grading systems, 2) global impression on the presence or absence of clinically significant stenosis (n = 60 disc levels for LSCS, n = 120 foramina for LNFS). Reliability statistics were calculated. RESULTS: Acquisition time was ∼5 minutes for SPACE and ∼20 minutes for 2D MRI sequences. Interobserver agreement of LSCS was substantial to near perfect on both sequences (morphologic grading: kappa [k] = 0.71 SPACE, k = 0.69 T2-weighted; global impression: k = 0.85 SPACE, k = 0.78 T2-weighted). LNFS assessment had superior interobserver reliability using SPACE than T1-weighted (k = 0.54 vs 0.37). Intersequence agreement of findings between SPACE and 2D MRI was substantial to near perfect by global impression (LSCS: k = 0.78 Reader 1, k = 0.85 Reader 2; LNFS: k = 0.63 Reader 1, k = 0.66 Reader 2). CONCLUSIONS: 3D SPACE was acquired in one-quarter the time as the conventional 2D MRI protocol, had excellent agreement with 2D MRI for stenosis assessment, and had interobserver reliability superior to 2D MRI. These results justify future work to explore the role of 3D SPACE in a rapid MRI screening protocol at 1.5-T for mechanical LBP.

Disease-specific definitions of new bone formation on spine radiographs: a systematic literature review.

Objectives: We aimed to explore the radiographic definitions of types of New Bone formation (NBF) by focusing on the terminology, description and location of the findings. Methods: Three systematic literature reviews were conducted in parallel to identify the radiographic spinal NBF definitions for spondyloarthritis (SpA), Diffuse Idiopathic Skeletal Hyperostosis (DISH) and Osteorathritis (OA). Study characteristics and definitions were extracted independently by two reviewers. Definitions were analysed and collated based on whether they were unique, modified or established from previous research. Results: We identified 33 studies that indicated a definition for the NBF in SpA, 10 for DISH and 7 for spinal OA. In SpA, the variations in syndesmophytes included the description as well as the subtypes and locations. The differentiation of syndesmophytes from osteophytes were included in 12 articles, based on the origin and the angle of the NBF and associated findings. The definitions of DISH varied in the number of vertebrae, level and laterality. For OA, five articles indicated that osteophytes arose from the anterior or lateral aspects of the vertebral bodies, and two studies required a size cut-off. Discussion: Our ultimate aim is to create formal NBF definitions for SpA, DISH and OA guided by an atlas, through a Delphi exercise with international experts. The improved ability to differentiate these conditions radiographically will not only allow the clinicians to accurately approach patients but also will help the researchers to better classify patient phenotypes and focus on accurate radiographic outcomes.

Frequently missed findings in acute ankle injury.

Most acute ankle injuries involve the lateral ligament complex. There are several other structures that can be injured during acute ankle trauma and therefore can be responsible for the patient's acute presentation or for continuing pain. Some of these injuries are less common than others and thus can be more frequently missed during the initial patient presentation. Continued pain and disability following acute ankle trauma that is not responding to routine conservative treatment should alert the clinician and the radiologist for the possibility of injuries other than the common lateral ligament sprain. In this article we describe those injuries that are often overlooked during acute ankle assessment. These include the less common ankle ligaments injuries, fractures, and tendon-related abnormalities.

Accuracy of a Patient-Specific Total Ankle Arthroplasty Instrumentation.

BACKGROUND: Total ankle arthroplasty (TAA) is a preferred surgical option for end-stage ankle osteoarthritis; however, it is a demanding procedure with a higher historical rate of revision compared with ankle fusion. Patient-specific instrumentation (PSI) has been introduced to optimize prosthesis alignment and theoretically overall improve TAA outcomes. The goal of this study is to report on the experience and surgical outcomes of one implant with specific evaluation of the accuracy and reproducibility of the system with respect to prosthesis alignment and prediction of implant size. METHODS: A retrospective, multicentered study involving 4 foot and ankle fellowship-trained orthopaedic surgeon's patients undergoing TAA between January 1, 2015, and December 31, 2018, using the PROPHECY PSI system. RESULTS: 80 TAA procedures were performed. On average the postoperative tibial component alignment was 89.9 (range, 86.1-96.5) degrees in the coronal plane, with a mean sagittal alignment of 88.1 (range, 81.3-96.7) degrees. The mean deviation from neutral sagittal alignment improved from 4.9 ± 3.9 degrees preoperatively to 2.7 ± 1.7 degrees postoperatively, whereas the mean coronal alignment improved from 3.3 ± 2.5 degrees to 1.3 ± 1.1 degrees. The PSI software correctly determined the tibial implant size in 70 patients (89%). Prediction of talar implant sizing was less accurate than the tibial component, with 56 patients (71%) using the predicted sized implant. The overall implant survival at a mean follow-up of 45 months (range, 27-76) was 97.5%. CONCLUSION: We found that this PSI system accurately and reliably assisted in implant total ankle prosthesis positioning within a clinically acceptable margin and without significant outliers. Prediction of implant size was not as accurate as component orientation. LEVEL OF EVIDENCE: Level III, retrospective study.

The association of infrapatellar fat pad oedema with patellar maltracking: a case-control study.

OBJECTIVE: To look for any association between oedema in the superolateral portion of the infrapatellar fat pad and patellar maltracking. MATERIALS AND METHODS: We compared two groups of knee MRI with regard to five patellar maltracking parameters. The first group included 100 knees with evidence of oedema in the superolateral aspect of the infrapatellar fat pad (the study group). The second group included another 100 knee MRI that had a normal infrapatellar fat pad (the control group). The five patellar maltracking parameters assessed were the trochlear depth, tibial tuberosity-trochlear groove distance (TTTG), patellar translation, patellofemoral angle (PFA) and the Insall-Salvati index. RESULTS: There was a statistically significant difference in the Insall-Salvati index, patellar translation and PFA between the two groups (p value of <0.001, <0.001 and 0.004 respectively, Student's t test). There was a higher prevalence of patella alta, lateral patellar displacement (LPD) and lateral patellar tilt in the study group (p value of <0.001, <0.001 and 0.011 respectively, Fisher's exact test). Sixty out of 100 knees in the study group had at least one abnormal patellar maltracking parameter in comparison to 16 out of 100 knees in the control group (p < 0.001, Fisher's exact test). CONCLUSION: Oedema in the superolateral portion of Hoffa's fat pad, the MRI feature of fat pad impingement, is associated with patellar maltracking.