CT of the musculoskeletal system: what is left is the days of MRI?

Musculoskeletal Computed Tomography: How to Add Value When Reporting Adult Upper Limb Trauma

ABSTRACT

There is increasing reliance on computed tomography to evaluate fractures and dislocations following routine evaluation with plain radiography, critical in preoperative planning; computed tomography can provide multiplanar reformats and 3-dimensional volume-rendered imaging, providing a better global assessment for the orthopedic surgeon. The radiologist plays a critical role in appropriately reformatting the raw axial images to illustrate best the findings that will help determine further management. In addition, the radiologist must succinctly report the pertinent findings that will have the most significant bearing on treatment, assisting the surgeon in deciding between nonoperative and operative management. The radiologist should also carefully review imaging to look for ancillary findings in the setting of trauma beyond the bones and joints, including the lungs and rib cage when visualized.In this review article, we will systematically describe key features for fractures of the scapula, proximal humerus, distal humerus, radial head and neck, olecranon, coronoid process through a case-based approach, and distal radius. Although there are numerous detailed classification systems for each of these fractures, we aim to focus on the core descriptors that underpin these classification systems. The goal is to provide the radiologist with a checklist of critical structures they must assess and findings that they should mention in their report, emphasizing those descriptors that influence patient management.

Non-ionic CT contrast solutions rapidly alter bovine cartilage and meniscus mechanics

OBJECTIVE

To evaluate effects of a common CT contrast agent (iohexol) on the mechanical behaviors of cartilage and meniscus.

METHODS

Indentation responses of juvenile bovine cartilage and meniscus were monitored following exposure to undiluted contrast agent (100% CA), 50% CA/water, 50% CA/Phosphate Buffered Saline (PBS) or PBS alone, and during re-equilibration in PBS. The normalized peak force (Fpk¯), effective osmotic strain (εosm), and normalized effective contact modulus (Ec¯) were calculated for every cycle, with time constants determined for both exposure and recovery via mono- or biexponential fits to Fpk¯.

RESULTS

All cartilage CA groups exhibited long-term increases in Fpk¯ following exposure, although the hyperosmolal 100% CA and 50% CA/PBS groups showed an initial transient decrease. Meniscus presented opposing trends, with decreasing Fpk¯ for all CA groups. Re-equilibration in PBS for 1hr after exposure to 100% CA produced recovery to baseline Fpk¯ in cartilage but not in meniscus, and extended tests indicated that meniscus required ∼2.5 h to recover halfway. Ec¯ increased with CA exposure time for cartilage but decreased for meniscus, suggesting an increased effective stiffness for cartilage and decreased stiffness for meniscus. Long-term changes to εosm in both tissues were consistent with changes in Ec¯.

CONCLUSION

Exposure to iohexol solutions affected joint tissues differentially, with increased cartilage stiffness, likely relating to competing hyperosmotic and hypotonic interactions with tissue fixed charges, and decreased meniscus stiffness, likely dominated by hyperosmolarity. These altered tissue mechanics could allow non-physiological deformation during ambulatory weight-bearing, resulting in an increased risk of tissue or cell damage.

ACR Appropriateness Criteria® Acutely Limping Child Up To Age 5

Imaging plays in important role in the evaluation of the acutely limping child. The decision-making process about initial imaging must consider the level of suspicion for infection and whether symptoms can be localized. The appropriateness of specific imaging examinations in the acutely limping child to age 5 years is discussed with attention in each clinical scenario to the role of radiography, ultrasound, nuclear medicine, computed tomography, and magnetic resonance imaging. Common causes of limping such as toddler's fracture, septic arthritis, transient synovitis, and osteomyelitis are discussed. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

CT of facial fracture fixation: an experimental study of artefact reducing methods

OBJECTIVES

This study aimed to determine the optimal post-operative CT imaging method that enables best visualization of facial bony structures in the vicinity of osteosynthesis material.

METHODS

Conducted at Töölö Hospital (Helsinki, Finland), this study relied on scanning a phantom with CBCT, 64-slice CT and high-definition multislice CT with dual-energy scan (providing monochromatic images of 70-, 100-, 120- and 140-keV energy levels) and iterative reconstruction (IR) methods. Two radiologists assessed the image quality, and the assessments were analyzed. In addition, a physicist performed a semi-quantitative analysis of the metal-induced artefacts.

RESULTS

The three subjects most easily assessed were the loose screw and both the bone structure and the fracture further away from the screw and the plate. Soft tissues adjacent to the screw and the plate remained more difficult for assessment. Both image interpreters agreed that the artefacts disturbed their assessments under dual energy. Metal artefacts disturbed the least under multislice CT with IR [adaptive statistical iterative reconstruction (ASiR) and VEO]. Neither interpreter found metal suppression helpful in CBCT.

CONCLUSIONS

CBCT with or without a metal artefact reduction algorithm was not optimal for post-operative facial imaging compared with multislice CT with IR. Multislice CT with ASiR filtering offered good image quality performance with fast image volume reconstruction, representing the current sweet spot in post-operative maxillofacial imaging.

Total ankle arthroplasty: optimizing computed tomography imaging protocol

OBJECTIVE

To evaluate parameters and positioning when imaging total ankle prostheses on computed tomography (CT).

MATERIALS AND METHODS

An ankle prosthesis implanted into a pig's knee joint underwent 16 different CT imaging protocols. Four defects were drilled around prosthesis components simulating periprosthetic osteolytic lesions. The specimen with the implant was imaged in four different orientations with the tibial stem parallel to the table and at 25, 45, and 90° angles to it. The protocol consisted of scanning at 100, 120, and 140 kVp in every position with a pitch of 1.2. The scanning at 120 kVp in every position was repeated with a pitch of 1.0.

RESULTS

CT proved to be a reliable imaging modality when studying periprosthetic lesions adjacent to the ankle prosthesis when the tibial stem alignment was parallel to the table. When imaging at higher angles, metal artifacts distorted the image, making the analysis of periprosthetic bone structure unreliable. There were no statistically significant differences between different tube voltages or pitch in volume measurements of the osteolytic lesions.

CONCLUSIONS

CT is a reliable imaging method to evaluate periprosthetic bone structure around ankle prostheses when orientation of the prosthesis and acquisition parameters is optimized.

[Computed tomography and magnetic resonance imaging for painful spinal column: contributions and controversies]

The use of tomographic imaging techniques, computed tomography (CT) and magnetic resonance imaging (MRI), to complement or replace plain-film radiography in the study of spine pain is becoming more and more common. The aim of this paper is to provide a general review of the CT and MRI manifestations of the wide spectrum of lesions that can cause pain in the spinal column. This spectrum includes degenerative disease, malalignment, tumors, inflammatory processes, and infectious processes. Precise knowledge and accurate reporting of the findings at CT and MRI are fundamental for clinical decision making in patients with spine pain.

Soft-tissue masses and masslike conditions: what does CT add to diagnosis and management?

OBJECTIVE

Although MRI is the technique of choice for evaluating most soft-tissue masses, CT often provides valuable complementary information. Specifically, there are distinguishing CT characteristics that can suggest a specific diagnosis, including the lesion's mineralization pattern, density, pattern of adjacent bone involvement, and degree and pattern of vascularity.

CONCLUSION

This article provides an overview of the CT evaluation of soft-tissue masses, emphasizing a differential diagnosis based on these CT features.