Femoral cartilage damage occurs at the zone of femoral head necrosis and can be accurately detected on traction MR arthrography of the hip in patients undergoing joint preserving hip surgery

Radial Planes in Hip Magnetic Resonance Imaging: Techniques, Applications, and Perspectives

The hip cartilage and labrum, as the main targets of femoroacetabular impingement, sports-related or traumatic damage, as well as congenital and developmental abnormalities, have attracted increasing attention with the development of magnetic resonance imaging (MRI) and hip arthroscopy. MRI is a commonly used imaging modality to noninvasively visualize the hip cartilage and labral lesions. However, conventional orthogonal MRI planes encounter unique challenges given the ball-and-socket configuration of the hip joint, its anatomically abducted and anteverted orientation, and the thin, closely apposed cartilage enveloping the femoral head and acetabulum. Advancements in hip MRI's radial plane, which is acquired through the center of the hip joint, offer a solution. This technology provides true cross-sectional images of the cartilage and labrum perpendicular to the curvature of the joint, thereby mitigating the partial-volume-averaging effects. The integration of 3.0-Tesla high field strength and three-dimensional (3D) acquisition techniques further enhances the capabilities of the radial plane. This combination yields a high signal-to-noise ratio, high spatial resolution, high contrast between intraarticular structures, while minimizing partial-volume-averaging effects. Such improvements potentially facilitate the comprehensive detection of even minor chondral and labral lesions. The capability for multiplanar reconstruction from a single 3D volumetric acquisition further strengthens the usefulness of the radial plane by aiding in precise localization of hip cartilage and labral lesions, in line with hip arthroscopy findings. These advancements have the potential to standardize MRI evaluations and radiographic reporting systems for hip cartilage and labrum, offering precise guidance for hip arthroscopy. This article presents a comprehensive review of radial plane technology applied to the hip MRI, and discusses the morphological assessment and localization of hip cartilage and labral lesions utilizing this advanced imaging technique. EVIDENCE LEVEL: 5 TECHNICAL EFFICACY: Stage 2.

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.

Morphological assessment of cartilage and osteoarthritis in clinical practice and research: Intermediate-weighted fat-suppressed sequences and beyond

Magnetic resonance imaging (MRI) is widely regarded as the primary modality for the morphological assessment of cartilage and all other joint tissues involved in osteoarthritis. 2D fast spin echo fat-suppressed intermediate-weighted (FSE FS IW) sequences with a TE between 30 and 40ms have stood the test of time and are considered the cornerstone of MRI protocols for clinical practice and trials. These sequences offer a good balance between sensitivity and specificity and provide appropriate contrast and signal within the cartilage as well as between cartilage, articular fluid, and subchondral bone. Additionally, FS IW sequences enable the evaluation of menisci, ligaments, synovitis/effusion, and bone marrow edema-like signal changes. This review article provides a rationale for the use of FSE FS IW sequences in the morphological assessment of cartilage and osteoarthritis, along with a brief overview of other clinically available sequences for this indication. Additionally, the article highlights ongoing research efforts aimed at improving FSE FS IW sequences through 3D acquisitions with enhanced resolution, shortened examination times, and exploring the potential benefits of different magnetic field strengths. While most of the literature on cartilage imaging focuses on the knee, the concepts presented here are applicable to all joints. KEY POINTS: 1. MRI is currently considered the modality of reference for a "whole-joint" morphological assessment of osteoarthritis. 2. Fat-suppressed intermediate-weighted sequences remain the keystone of MRI protocols for the assessment of cartilage morphology, as well as other structures involved in osteoarthritis. 3. Trends for further development in the field of cartilage and joint imaging include 3D FSE imaging, faster acquisition including AI-based acceleration, and synthetic imaging providing multi-contrast sequences.

Hip Magnetic Resonance Arthrography Using Normal Saline Is Less Accurate Than Using a Gadolinium-Based Contrast Agent

PURPOSE

To evaluate the diagnostic performance of hip magnetic resonance (MR) arthrography with a gadolinium-based contrast agent (GBCA) or normal saline (NS) for intra-articular pathologies.

METHODS

This retrospective study was approved by the institutional review board of our hospital, and the requirement for informed consent was waived. The study included 37 consecutive patients (38 hips; 21 right hips; 24 males; mean age, 33 years) who underwent GBCA-hip MR arthrography from July 2011 to January 2020 and 30 consecutive patients (30 hips; 20 right hips; 21 males; mean age, 40 years) who underwent NS-hip MR arthrography from January 2018 to June 2020. All images were evaluated twice independently by two radiologists blinded to the arthroscopic findings for the presence of labral tears, cartilage abnormalities, or ligamentum teres tears. Intrareader and interreader reliabilities were determined by kappa values (k) using the chi-squared test, and diagnostic performance was evaluated based on the arthroscopic findings. A P value less than .05 was considered to indicate statistical significance.

RESULTS

Intra-reader reliability in the detection of intra-articular pathologies ranged from moderate to almost perfect (k = 0.510-0.840) and inter-reader reliability ranged from moderate to substantial (k = 0.441-0.695) for GBCA- and NS-hip MR arthrography. The diagnostic accuracy of GBCA- and NS-hip MR arthrography was as follows: 81.6-92.1% and 66.7-73.3% for labral tears, respectively; 68.4-86.8% and 63.3-70.0% for cartilage abnormality, respectively; and 68.4-76.3% and 50.0-56.7% for ligamentum teres tears, respectively.

CONCLUSION

NS-hip MR arthrography may be less accurate than GBCA-hip MR arthrography. LEVEL OF EVIDENCE: Level II of development of diagnostic criteria (consecutive patients with consistently applied reference standard and blinding).

A Deep Learning Method for Quantification of Femoral Head Necrosis Based on Routine Hip MRI for Improved Surgical Decision Making

(1) Background: To evaluate the performance of a deep learning model to automatically segment femoral head necrosis (FHN) based on a standard 2D MRI sequence compared to manual segmentations for 3D quantification of FHN. (2) Methods: Twenty-six patients (thirty hips) with avascular necrosis underwent preoperative MR arthrography including a coronal 2D PD-w sequence and a 3D T1 VIBE sequence. Manual ground truth segmentations of the necrotic and unaffected bone were then performed by an expert reader to train a self-configuring nnU-Net model. Testing of the network performance was performed using a 5-fold cross-validation and Dice coefficients were calculated. In addition, performance across the three segmentations were compared using six parameters: volume of necrosis, volume of unaffected bone, percent of necrotic bone volume, surface of necrotic bone, unaffected femoral head surface, and percent of necrotic femoral head surface area. (3) Results: Comparison between the manual 3D and manual 2D segmentations as well as 2D with the automatic model yielded significant, strong correlations (Rp > 0.9) across all six parameters of necrosis. Dice coefficients between manual- and automated 2D segmentations of necrotic- and unaffected bone were 75 ± 15% and 91 ± 5%, respectively. None of the six parameters of FHN differed between the manual and automated 2D segmentations and showed strong correlations (Rp > 0.9). Necrotic volume and surface area showed significant differences (all p < 0.05) between early and advanced ARCO grading as opposed to the modified Kerboul angle, which was comparable between both groups (p > 0.05). (4) Conclusions: Our deep learning model to automatically segment femoral necrosis based on a routine hip MRI was highly accurate. Coupled with improved quantification for volume and surface area, as opposed to 2D angles, staging and course of treatment can become better tailored to patients with varying degrees of AVN.

Less in-toeing after femoral derotation osteotomy in adult patients with increased femoral version and posterior hip impingement compared to patients with femoral retroversion

In-toeing of the foot was associated with high femoral version (FV), while Out-toeing was associated with femoral-retroversion. Therefore, we report on (i) foot-progression-angle (FPA), (ii) prevalence of In-toeing and Out-toeing, and (iii) clinical outcome of patients treated with femoral-derotation-osteotomy (FDO). We performed a retrospective analysis involving 20 patients (20 hips) treated with unilateral FDO (2017–18). Of them, 14 patients had increased FV, 6 patients had femoral-retroversion. Follow-up time was mean 1 ± 1 years. All patients had minimal 1-year follow-up and the mean age was 29 ± 8 years. Patients with increased FV (FV > 35°) presented with positive posterior-impingement-test and mean FV was 49 ± 11° (Murphy method). Six patients with femoral-retroversion (FV < 10°) had positive anterior impingement test and mean FV of 5 ± 4°. Instrumented gait analysis was performed preoperatively and at follow-up using the Gaitrite system to measure FPA and was compared to a control group of 18 healthy asymptomatic volunteers (36 feet, mean age 29 ± 6 years). (i) Mean FPA increased significantly (P = 0.006) from preoperative 1.3 ± 7° to 4.5 ± 6° at follow-up for patients with increased FV and was not significantly different compared to the control group (4.0 ± 4.5°). (ii) In-toeing decreased from preoperatively (five patients) to follow-up (two patients) for patients with increased FV. Out-toeing decreased from preoperatively (two patients) to follow-up (no patient) for patients with femoral-retroversion. (iii) Subjective-hip-value of all patients increased significantly (P < 0.001) from preoperative 21 to 78 points at follow-up. WOMAC was 12 ± 8 points at follow-up. Patients with increased FV that underwent FDO walked with less In-toeing. FDO has the potential to reduce In-toeing and Out-toeing and to improve subjective satisfaction at follow-up.