Measures of Molecular Composition and Structure in Osteoarthritis

Comprehensive Study on Scoring and Grading Systems for Predicting the Severity of Knee Osteoarthritis

Knee Osteoarthritis (KOA) is a degenerative joint ailment characterized by cartilage loss, which can be seen using imaging modalities and converted into imaging features. The older population is the most affected by knee OA, which affects 16% of people worldwide who are 15 years of age and older. Due to cartilage tissue degradation, primary knee OA develops in older people. In contrast, joint overuse or trauma in younger people can cause secondary knee OA. Early identification of knee OA, according to research, may be a successful management tactic for the condition. Scoring scales and grading systems are important tools for the management of knee osteoarthritis as they allow clinicians to measure the progression of the disease's severity and provide suggestions on suitable treatment at identified stages. The comprehensive study reviews various subjective and objective knee evaluation scoring systems that effectively score and grade the KOA based on where defects or changes in articular cartilage occur. Recent studies reveal that AI-based approaches, such as that of DenseNet, integrating the concept of deep learning for scoring and grading the KOA, outperform various state-of-the-art methods in order to predict the KOA at an early stage.

Advancing drug delivery to articular cartilage: From single to multiple strategies

Articular cartilage (AC) injuries often lead to cartilage degeneration and may ultimately result in osteoarthritis (OA) due to the limited self-repair ability. To date, numerous intra-articular delivery systems carrying various therapeutic agents have been developed to improve therapeutic localization and retention, optimize controlled drug release profiles and target different pathological processes. Due to the complex and multifactorial characteristics of cartilage injury pathology and heterogeneity of the cartilage structure deposited within a dense matrix, delivery systems loaded with a single therapeutic agent are hindered from reaching multiple targets in a spatiotemporal matched manner and thus fail to mimic the natural processes of biosynthesis, compromising the goal of full cartilage regeneration. Emerging evidence highlights the importance of sequential delivery strategies targeting multiple pathological processes. In this review, we first summarize the current status and progress achieved in single-drug delivery strategies for the treatment of AC diseases. Subsequently, we focus mainly on advances in multiple drug delivery applications, including sequential release formulations targeting various pathological processes, synergistic targeting of the same pathological process, the spatial distribution in multiple tissues, and heterogeneous regeneration. We hope that this review will inspire the rational design of intra-articular drug delivery systems (DDSs) in the future.

Research progress of cartilage lubrication and biomimetic cartilage lubrication materials

Human joints move thousands of times a day. The articular cartilage plays a vital role in joints’ protection. If there is dysfunction in cartilage lubrication, cartilage cannot maintain its normal function. Eventually, the dysfunction may bring about osteoarthritis (OA). Extensive researches have shown that fluid film lubrication, boundary lubrication, and hydration lubrication are three discovered lubrication models at cartilage surface, and analyzing and simulating the mechanism of cartilage lubrication are fundamental to the treatment of OA. This essay concludes recent researches on the progress of cartilage lubrication and biomimetic cartilage, revealing the pathophysiology of cartilage lubrication and updating bio-inspired cartilage lubrication applications.

The relation between the biochemical composition of knee articular cartilage and quantitative MRI: a systematic review and meta-analysis

OBJECTIVE

Early and non-invasive detection of osteoarthritis (OA) is required to enable early treatment and monitoring of interventions. Some of the earliest signs of OA are the change in proteoglycan and collagen composition. The aim of this study is to establish the relations between quantitative magnetic resonance imaging (MRI) and biochemical concentration and organization in knee articular cartilage.

METHODS

A preregistered systematic literature review was performed using the databases PubMed and Embase. Papers were included if quantitative MRI and a biochemical assay or polarized light microscopy (PLM) was performed on knee articular cartilage, and a quantified correlation was described. The extracted correlations were pooled using a random effects model.

RESULTS

21 papers were identified. The strongest pooled correlation was found for delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) vs proteoglycan concentration (r = 0.59). T1ρ relaxation times are inversely correlated to proteoglycan concentration (r = -0.54). A weak correlation between T2 relaxation times and proteoglycans was found (r = -0.38). No correlation between T2 relaxation time and collagen concentration was found (r = -0.02). A heterogeneous set of correlations between T2 relaxation times and PLM were identified, including strong correlations to anisotropy.

CONCLUSION

DGEMRIC measures are significantly correlated to proteoglycan concentration. The needed contrast agent is however a disadvantage; the T1ρ sequence was found as a non-invasive alternative. Remarkably, no correlation was found between T2 relaxation times and collagen concentration. T2 relaxation times is related to organization, rather than concentration of collagen fibers.

PROSPERO ID

CRD42020168337.

High resolution T2∗ mapping in assessment of knee articular cartilage on 3T MRI

OBJECTIVE

To evaluate the spectrum of T2∗ values in healthy cartilage of young asymptomatic adults on high resolution 3T MRI.

METHODS

A total of 50 asymptomatic adult volunteers with age ranging from 18 to 35 years were enrolled for the study with the purpose of assessing T2∗ values in healthy cartilage without any degenerative changes. The articular cartilage was assessed on two sections, one each through the medial and lateral compartments. The cartilage was segmented into 8 regions through the tibio-femoral and patella-femoral joints. Further post processing was done using multiple ROI placement to delineate ROI areas for calculation of full thickness and zonal (superficial and deep) T2∗ values. Thus, a total of 1200 ROI areas (50 volunteers, 8 segments, and 3 areas for each segment) were assessed.

RESULTS

The results revealed a superior bulk T2∗ value of 29.2 ± 3.6 ms from the posterior medial femoral cartilage and 26.1 ± 3.1 ms from the patellar region. Intermediate values were obtained from posterior lateral femoral cartilage, central femoral cartilage, and trochlea. The tibial plateau cartilage had the lowest values - 19.6 ± 2.6 ms for the medial tibial plateau and 20.6 ± 2.8 ms for lateral tibial plateau. The study demonstrated substantial regional physiological variation existing in the T2∗ values across various regions of the knee joint, which could be attributed to varying amounts of shearing forces across the joint. No significant differences were noted in bulk T2∗ values between the two genders, with only the trochlear segment revealing significantly increased values in males (p = 0.007). All the cartilage segments revealed significantly increased T2∗ values in the superficial zone as compared to the deep zone.

CONCLUSION

There is a significant regional difference in the bulk T2∗ values of articular cartilage in a normal physiological state across various joint segments. A zonal gradient with increasing values from the deep to the superficial zone also exists. These findings can prove invaluable in assessing changes in T2∗ values occurring in diseased/degenerative cartilage.

An Expert-Supervised Registration Method for Multiparameter Description of the Knee Joint Using Serial Imaging

As knee osteoarthritis is a disease of the entire joint, our pathophysiological understanding could be improved by the characterization of the relationships among the knee components. Diverse quantitative parameters can be characterized using magnetic resonance imaging (MRI) and computed tomography (CT). However, a lack of methods for the coordinated measurement of multiple parameters hinders global analyses. This study aimed to design an expert-supervised registration method to facilitate multiparameter description using complementary image sets obtained by serial imaging. The method is based on three-dimensional tissue models positioned in the image sets of interest using manually placed attraction points. Two datasets, with 10 knees CT-scanned twice and 10 knees imaged by CT and MRI were used to assess the method when registering the distal femur and proximal tibia. The median interoperator registration errors, quantified using the mean absolute distance and Dice index, were ≤0.45 mm and ≥0.96 unit, respectively. These values differed by less than 0.1 mm and 0.005 units compared to the errors obtained with gold standard methods. In conclusion, an expert-supervised registration method was introduced. Its capacity to register the distal femur and proximal tibia supports further developments for multiparameter description of healthy and osteoarthritic knee joints, among other applications.

Knee joint unloading and daily physical activity associate with cartilage T2 relaxation times 1 month after ACL injury

Osteoarthritis (OA) is prevalent after anterior cruciate ligament (ACL) injury, but mechanismsunderlying its development are poorly understood. The purpose of this study was to determine if gait biomechanics and daily physical activity (PA) associate with cartilage T2 relaxation times, a marker of collagen organization and water content, 1 month after ACL injury. Twenty-seven participants (15-35 years old) without chondral lesions completed magnetic resonance imaging, three-dimensional gait analysis, and 1 week of PA accelerometry. Interlimb differences and ratios were calculated for gait biomechanics and T2 relaxation times, respectively. Multiple linear regression models adjusted for age, sex, and concomitant meniscus injury were used to determine the association between gait biomechanics and PA with T2 relaxation times, respectively. Altered knee adduction moment (KAM) impulse, less knee flexion excursion (kEXC) and higher daily step counts accounted for 35.8%-65.8% of T2 relaxation time variation in the weightbearing and posterior cartilage of the medial and lateral compartment (all p ≤ .011). KAM impulse was the strongest factor for T2 relaxation times in all models (all p ≤ .001). Lower KAM impulse associated with longer T2 relaxation times in the injured medial compartment (β = -.720 to -.901) and shorter T2 relaxation in the lateral compartment (β = .713 to .956). At 1 month after ACL injury, altered KAM impulse, less kEXC, and higher PA associated with longer T2 relaxation times, which may indicate poorer cartilage health. Statement of Clinical Significance: Gait biomechanics and daily PA are modifiable targets that may improve cartilage health acutely after ACL injury and slow progression to OA.

Cutoff points of T1 rho/T2 mapping relaxation times distinguishing early-stage and advanced osteoarthritis

INTRODUCTION

The histopathology grading system is the gold standard post-operative method to evaluate cartilage degeneration in knee osteoarthritis (OA). Magnetic resonance imaging (MRI) T1 rho/T2 mapping imaging can be used for preoperative detection. An association between histopathology and T1 rho/T2 mapping relaxation times was suggested in previous research. However, the cutoff point was not determined among different histopathology grades. Our study aimed to determine the cutoff point of T1 rho/T2 mapping.

MATERIAL AND METHODS

T1 rho/T2 mapping images were acquired from 80 samples before total knee replacements. Then the histopathology grading system was applied.

RESULTS

The mean T1 rho/T2 mapping relaxation times of 80 samples were 39.17 ms and 37.98 ms respectively. Significant differences were found in T1 rho/T2 mapping values between early-stage and advanced OA (p < 0.001). The cutoff point for T1 rho was 33 ms with a sensitivity of 94.12 (95% CI: 80-99.3) and a specificity of 91.30 (95% CI: 79.2-97.6). The cutoff point for T2 mapping was suggested as 35.04 ms with a sensitivity of 88.24 (95% CI: 72.5-96.7) and specificity of 97.83 (95% CI: 88.5-99.9). After bootstrap simulation, the 95% CI of the T1 rho/T2 mapping cutoff point was estimated as 29.36 to 36.32 ms and 34.8 to 35.04 ms respectively. The area under the PR curve of T1 rho/T2 mapping was 0.972 (95% CI: 0.925-0.992) and 0.949 (95% CI: 0.877-0.989) respectively.

CONCLUSIONS

The cutoff point of T1 rho relaxation times, which was suggested as 33 ms, could be used to distinguish early-stage and advanced OA.

Individual and cumulative measures of knee joint load associate with T2 relaxation times of knee cartilage in young, uninjured individuals: A pilot study

BACKGROUND

Articular cartilage structure and chondrocyte health are sensitive and reliant on dynamic joint loading during activities. The purpose of this pilot study was to determine the association between measures of individual and cumulative knee joint loading with T2 relaxation times in the knee cartilage of young individuals without knee injury.

METHODS

Twelve participants (17-30 years old) without history of knee injury or surgery completed MRI, physical activity (PA), and biomechanical gait testing. T2 relaxation times were calculated in the cartilage within the patella and lateral and medial compartments. Accelerometry was used to measure mean daily step counts, minutes of PA, and % sedentary time over 7 days. Vertical ground reaction force, external knee joint moments and peak knee flexion angle were measured during stance phase of gait using three-dimensional motion capture. Cumulative knee joint loading was calculated as daily step count by external knee joint moment impulse. The relationship between measures of knee joint loading and T2 relaxation times was assessed using Pearson correlations.

RESULTS

Higher T2 relaxation times in the femoral and tibial cartilage were consistently correlated to greater body mass, daily step counts, moderate and vigorous PA, and peak knee joint moments (r = 0.10-0.84). Greater cumulative knee flexion and adduction loading was associated with higher T2 relaxation times in the femoral and tibial cartilage (r = 0.16-0.65).

CONCLUSION

Preliminary findings suggest that individual loading factors and cumulative knee joint loading are associated with higher T2 relaxation times in the articular cartilage of young, healthy knees.

Review of Quantitative Knee Articular Cartilage MR Imaging

Osteoarthritis (OA) is one of the most prevalent disorders in today’s society, resulting in significant socio-economic costs and morbidity. MRI is widely used as a non-invasive imaging tool for OA of the knee. However, conventional knee MRI has limitations to detect subtle early cartilage degeneration before morphological changes are visually apparent. Novel MRI pulse sequences for cartilage assessment have recently received increased attention due to newly developed compositional MRI techniques, including: T2 mapping, T1rho mapping, delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), sodium MRI, diffusion-weighted imaging (DWI)/ diffusion tensor imaging (DTI), ultrashort TE (uTE), and glycosaminoglycan specific chemical exchange saturation transfer (gagCEST) imaging. In this article, we will first review these quantitative assessments. Then, we will discuss the variations of quantitative values of knee articular cartilage with cartilage layer (depth)- and angle (regional)-dependent approaches. Multiple MRI sequence techniques can discern qualitative differences in knee cartilage. Normal articular hyaline cartilage has a zonal variation in T2 relaxation times with increasing T2 values from the subchondral bone to the articular surface. T1rho values were also higher in the superficial layer than in the deep layer in most locations in the medial and lateral femoral condyles, including the weight-bearing portion. Magic angle effect on T2 mapping is clearly observed in the both medial and lateral femoral condyles, especially within the deep layers. One of the limitations for clinical use of these compositional assessments is a long scan time. Recent new approaches with compressed sensing (CS) and MR fingerprinting (MRF) have potential to provide accurate and fast quantitative cartilage assessments.

Recent Progress in Cartilage Lubrication

Healthy articular cartilage, covering the ends of bones in major joints such as hips and knees, presents the most efficiently-lubricated surface known in nature, with friction coefficients as low as 0.001 up to physiologically high pressures. Such low friction is indeed essential for its well-being. It minimizes wear-and-tear and hence the cartilage degradation associated with osteoarthritis, the most common joint disease, and, by reducing shear stress on the mechanotransductive, cartilage-embedded chondrocytes (the only cell type in the cartilage), it regulates their function to maintain homeostasis. Understanding the origins of such low friction of the articular cartilage, therefore, is of major importance in order to alleviate disease symptoms, and slow or even reverse its breakdown. This progress report considers the relation between frictional behavior and the cellular mechanical environment in the cartilage, then reviews the mechanism of lubrication in the joints, in particular focusing on boundary lubrication. Following recent advances based on hydration lubrication, a proposed synergy between different molecular components of the synovial joints, acting together in enabling the low friction, has been proposed. Additionally, recent development of natural and bio-inspired lubricants is reviewed.

Higher Body Mass Index Is Associated With Biochemical Changes in Knee Articular Cartilage After Marathon Running: A Quantitative T2-Relaxation MRI Study

Background:

More than 30 million individuals participate in marathon running every year worldwide. As the popularity of marathon running continues to increase, it is essential for the purposes of injury prevention to understand the effects of marathon running on the knee cartilage.

Purpose:

To investigate the immediate effects of marathon running on knee articular cartilage and to determine the relationship between body mass index and cartilage biochemical composition.

Study Design:

Descriptive laboratory study.

Methods:

T2-relaxation magnetic resonance imaging (MRI) of knees in 18 nonprofessional marathoners (mean age, 35.6 ± 6.4 years) was performed before and after a full-length marathon. Three-dimensional models of the knee articular cartilage were reconstructed and divided into different regions of interest. The 3-dimensional models were then applied to corresponding T2-relaxation MRI maps to calculate T2 values in each region of interest. The mean values of the T2-relaxation times in each region of interest before and after the marathon were compared by use of the paired Student t test. The Pearson correlation coefficient between T2 change and runner body mass index (BMI) was calculated.

Results:

Postmarathon T2-relaxation times were significantly higher than premarathon values for patellofemoral cartilage (32.6 ± 12.1 vs 34.1 ± 10.9 ms; P < .01) and medial tibial cartilage (35.6 ± 11.7 vs 34.6 ± 12.0 ms; P = .01). The greatest increase was observed in the anterior part of the medial tibial cartilage. No statistically significant changes were seen in the T2-relaxation times of the lateral tibial and femoral cartilage. Postmarathon T2-relaxation elevation in the anteromedial knee tibiofemoral joint cartilage strongly correlated with body weight (R = 0.6746; P = .03) and BMI (R = 0.6989; P = .001). Changes in T2-relaxation times did not correlate with marathon time, height, age, or sex in any regions of interest.

Conclusion:

Marathon running leads to immediate postmarathon elevated T2-relaxation values within knee articular cartilage, suggesting biochemical content alteration. Additionally, runners with higher BMI may have greater changes in cartilage biochemical composition after a marathon. Further studies should investigate whether these changes are sustained over time to determine the relationship between immediate biochemical changes in cartilage composition and cartilage degeneration.

Clinical Relevance:

Runners with a higher BMI may carry a higher risk of anteromedial tibiofemoral cartilage degeneration compared with runners with lower BMI.

Morphological MRI of knee cartilage: repeatability and reproducibility of damage evaluation and correlation with gross pathology examination

OBJECTIVE

To assess the performance of a morphological evaluation, based on a clinically relevant magnetic resonance imaging (MRI) protocol, in scoring the severity of knee cartilage damage. Specifically, to evaluate the reproducibility, repeatability, and agreement of MRI evaluation with the gross pathology examination (GPE) of the tissue.

METHODS

MRI of the knee was performed the day before surgery in 23 patients undergoing total knee arthroplasty. Osteochondral tissue resections were collected and chondral defects were scored by GPE according to a semi-quantitative scale. MR images were independently scored by four radiologists, who assessed the severity of chondral damage according to equivalent criteria. Inter- and intra-rater agreements of MRI evaluations were assessed. Correlation, precision, and accuracy metrics between MRI and GPE scores were calculated.

RESULTS

Moderate to substantial inter-rater agreement in scoring cartilage damage by MRI was found among radiologists. Intra-rater agreement was higher than 96%. A significant positive monotonic correlation between GPE and MRI scores was observed for all radiologists, although higher correlation values were obtained by radiologists with expertise in musculoskeletal radiology and/or longer experience. The accuracy of MRI scores displayed a spatial pattern, characterized by lesion overestimation in the lateral condyle and underestimation in the medial condyle with respect to GPE.

CONCLUSIONS

Evaluation of knee cartilage morphology by MRI is a reproducible and repeatable technique, which positively correlates with GPE. Clinical expertise in musculoskeletal radiology positively impacts the evaluation reliability. These findings may help to address limitations in MRI evaluation of knee chondral lesions, thus improving MRI assessment of knee cartilage.

KEY POINTS

• MRI evaluation of knee cartilage shows moderate to strong correlation with gross pathology examination. • MRI evaluation overestimates cartilage damage in the lateral condyle and underestimates it in the medial condyle. • Education and experience of the radiologist play a role in MRI evaluation of knee chondral lesions.

Magnetic Resonance Imaging of the Musculoskeletal System at 7T: Morphological Imaging and Beyond

In 2017, a whole-body 7T magnetic resonance imaging (MRI) device was given regulatory approval for clinical use in both the EU and United States for neuro and musculoskeletal applications. As 7 Tesla allows for higher signal-to-noise , which results in higher resolution images than those obtained on lower-field-strength scanners, it has attracted considerable attention from the musculoskeletal field, as evidenced by the increasing number of publications in the last decade. Besides morphological imaging, the quantitative MR methods, such as T₂, T₂∗, T_1ρ mapping, sodium imaging, chemical-exchange saturation transfer, and spectroscopy, substantially benefit from ultrahigh field scanning. In this review, we provide technical considerations for the individual techniques and an overview of (mostly) clinical applications for the assessment of cartilage, tendon, meniscus, and muscle. The first part of the review is dedicated to morphological applications at 7T, and the second part describes the most recent developments in quantitative MRI at 7T.

[Advanced cartilage imaging for detection of cartilage injuries and osteochondral lesions]

BACKGROUND

Osteochondral defects represent a main risk factor for osteoarthritis of the ankle.

OBJECTIVES

The aim of this article is to provide an overview of current optimal clinical cartilage imaging techniques of the foot and ankle and to show typical osteochondral injuries on imaging.

MATERIALS AND METHODS

A thorough literature search was performed and was supported by personal experience.

RESULTS

Cartilage imaging of the foot and ankle remains challenging. However, advanced morphological and quantitative magnetic resonance (MR) imaging techniques may provide useful clinical information, for example, concerning cartilage repair surgery. Compared to MRI, MR arthrography (MR-A) and CT arthrography (CT-A) have higher sensitivity with respect to detection of osteochondral defects. Regarding smaller joints of the foot, mainly advanced osteoarthritic changes are detected on conventional radiography; only in rare cases, MR and CT imaging of these smaller joints is of relevance.

CONCLUSIONS

While at the smaller joints of the foot cartilage imaging only plays a minor role, at the ankle joint cross-sectional cartilage imaging using CT and MRI becomes more and more important for clinicians due to emerging therapeutic options, such as different osteochondral repair techniques.

[Update cartilage imaging of the small joints : Focus on high-field MRI]

BACKGROUND

Cartilage imaging of small joints is increasingly of interest, as early detection of cartilage damage may be relevant regarding individualized surgical therapies and long-term outcomes.

PURPOSE

The aim of this review is to explain modern cartilage imaging of small joints with emphasis on MRI and to discuss the role of methods such as CT arthrography as well as compositional and high-field MRI.

MATERIALS AND METHODS

A PubMed literature search was performed for the years 2008-2018.

RESULTS

Clinically relevant cartilage imaging to detect chondral damage in small joints remains challenging. Conventional MRI at 3 T can still be considered as a reference for cartilage imaging in clinical routine. In terms of sensitivity, MR arthrography (MR-A) and computed tomography arthrography (CT-A) are superior to non-arthrographic MRI at 1.5 T in the detection of chondral damage. Advanced degenerative changes of the fingers and toes are usually sufficiently characterized by conventional radiography. MRI at field strengths of 3 T and ultrahigh-field imaging at 7 T can provide additional quantifiable, functional and metabolic information.

CONCLUSION

Standardized cartilage imaging plays an important role in clinical diagnostics in the ankle joint due to the availability of different and individualized therapeutic concepts. In contrast, cartilage imaging of other small joints as commonly performed in clinical studies has not yet become standard of care in daily clinical routine. Although individual study results are promising, additional studies with large patient collectives are needed to validate these techniques. With rapid development of new treatment concepts radiological diagnostics will play a more significant role in the diagnosis of cartilage lesions of small joints.

3D grating-based X-ray phase-contrast computed tomography for high-resolution quantitative assessment of cartilage: An experimental feasibility study with 3T MRI, 7T MRI and biomechanical correlation

Objective

Aim of this study was, to demonstrate the feasibility of high-resolution grating-based X-ray phase-contrast computed tomography (PCCT) for quantitative assessment of cartilage.

Materials and methods

In an experimental setup, 12 osteochondral samples were harvested from n = 6 bovine knees (n = 2 each). From each knee, one cartilage sample was degraded using 2.5% Trypsin. In addition to PCCT and biomechanical cartilage stiffness measurements, 3T and 7T MRI was performed including MSME SE T2 and ME GE T2* mapping sequences for relaxationtime measurements. Paired t-tests and receiver operating characteristics (ROC) curves were used for statistical analyses.

Results

PCCT provided high-resolution images for improved morphological cartilage evaluation as compared to 3T and 7T MRI. Quantitative analyses revealed significant differences between the superficial and the deep cartilage layer for T2 mapping as well as for PCCT (P<0.05). No significant difference was detected for PCCT between healthy and degraded samples (P>0.05). MRI and stiffness measurements showed significant differences between healthy and degraded osteochondral samples. Accuracy in the prediction of cartilage degradation was excellent for MRI and biomechanical analyses.

Conclusion

In conclusion, high-resolution grating-based X-ray PCCT cartilage imaging is feasible. In addition to MRI and biomechanical analyses it provides complementary, water content independent, information for improved morphological and quantitative characterization of articular cartilage ultrastructure.

New imaging modalities to predict and evaluate osteoarthritis progression

In this narrative review, we discuss the role of different imaging methods for the evaluation of progression of structural osteoarthritis. We will focus on the role of less commonly applied imaging modalities and imaging biomarkers that were introduced in recent years or on established methods that have evolved into more prominent positions in recent years. We will highlight findings from longitudinal studies that focused on structural osteoarthritis progression as their outcome of interest. Imaging modalities discussed include plain radiography (including novel approaches of joint space width assessment and fractal signature analysis), ultrasonography (including the assessment of synovitis), magnetic resonance imaging (including semiquantitative, quantitative, and compositional evaluation), and positron emission tomography.

Micromass cultures are effective for differentiation of human amniotic fluid stem cells into chondrocytes

OBJECTIVES

Articular cartilage is vulnerable to injuries and undergoes an irreversible degenerative process. The use of amniotic fluid mesenchymal stromal stem cells for the reconstruction of articular cartilage is a promising therapeutic alternative. The aim of this study was to investigate the chondrogenic potential of amniotic fluid mesenchymal stromal stem cells from human amniotic fluid from second trimester pregnant women in a micromass system (high-density cell culture) with TGF-β3 for 21 days.

METHODS

Micromass was performed using amniotic fluid mesenchymal stromal stem cells previously cultured in a monolayer. Chondrocytes from adult human normal cartilage were used as controls. After 21 days, chondrogenic potential was determined by measuring the expression of genes, such as SOX-9, type II collagen and aggrecan, in newly differentiated cells by real-time PCR (qRT-PCR). The production of type II collagen protein was observed by western blotting. Immunohistochemistry analysis was also performed to detect collagen type II and aggrecan. This study was approved by the local ethics committee.

RESULTS

SOX-9, aggrecan and type II collagen were expressed in newly differentiated chondrocytes. The expression of SOX-9 was significantly higher in newly differentiated chondrocytes than in adult cartilage. Collagen type II protein was also detected.

CONCLUSION

We demonstrate that stem cells from human amniotic fluid are a suitable source for chondrogenesis when cultured in a micromass system. amniotic fluid mesenchymal stromal stem cells are an extremely viable source for clinical applications, and our results suggest the possibility of using human amniotic fluid as a source of mesenchymal stem cells.

Anatomically Standardized Maps Reveal Distinct Patterns of Cartilage Thickness With Increasing Severity of Medial Compartment Knee Osteoarthritis

While cartilage thickness alterations are a central element of knee osteoarthritis (OA), differences among disease stages are still incompletely understood. This study aimed to quantify the spatial-variations in cartilage thickness using anatomically standardized thickness maps and test if there are characteristic patterns in patients with different stages of medial compartment knee OA. Magnetic resonance images were acquired for 75 non-OA and 100 OA knees of varying severities (Kellgren and Lawrence (KL) scores 1-4). Three-dimensional cartilage models were reconstructed and a shape matching technique was applied to convert the models into two-dimensional anatomically standardized thickness maps. Difference thickness maps and statistical parametric mapping were used to compare the four OA and the non-OA subgroups. This analysis showed distinct thickness patterns for each clinical stage that formed a coherent succession from the non-OA to the KL 4 subgroups. Interestingly, the only significant difference for early stage (KL 1) was thicker femoral cartilage. With increase in disease severity, typical patterns developed, including thinner cartilage in the anterior area of the medial condyle (significant for KL 3 and 4) and thicker cartilage in the posterior area of the medial and lateral condyles (significant for all OA subgroups). The tibial patterns mainly consisted of thinner cartilage for both medial and lateral compartments (significant for KL 2-4). Comparing anatomically standardized maps allowed identifying patterns of thickening and thinning over the entire cartilage surface, consequently improving the characterization of thickness differences associated with OA. The results also highlighted the value of anatomically standardized maps to analyze spatial variations in cartilage thickness. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2442-2451, 2017.

Contrast-Enhanced Computed Tomography Enables Quantitative Evaluation of Tissue Properties at Intrajoint Regions in Cadaveric Knee Cartilage

Objective The aim of this study was to investigate whether the concentration of the anionic contrast agent ioxaglate, as quantitated by contrast-enhanced computed tomography (CECT) using a clinical cone-beam CT (CBCT) instrument, reflects biochemical, histological, and biomechanical characteristics of articular cartilage imaged in an ex vivo, intact human knee joint. Design An osteoarthritic human cadaveric knee joint (91 years old) was injected with ioxaglate (36 mg I/mL) and imaged using CBCT over 61 hours of ioxaglate diffusion into cartilage. Following imaging, the joint surfaces were excised, rinsed to remove contrast agent, and compressive stiffness (equilibrium and instantaneous compressive moduli) was measured via indentation testing ( n = 17 sites). Each site was sectioned for histology and assessed for glycosaminoglycan content using digital densitometry of Safranin-O stained sections, Fourier transform infrared spectroscopy for collagen content, and morphology using both the Mankin and OARSI semiquantitative scoring systems. Water content was determined using mass change after lyophilization. Results CECT attenuation at all imaging time points, including those <1 hour of ioxaglate exposure, correlated significantly ( P < 0.05) with cartilage water and glycosaminoglycan contents, Mankin score, and both equilibrium and instantaneous compressive moduli. Early time points (<30 minutes) also correlated ( P < 0.05) with collagen content and OARSI score. Differences in cartilage quality between intrajoint regions were distinguishable at diffusion equilibrium and after brief ioxaglate exposure. Conclusions CECT with ioxaglate affords biochemical and biomechanical measurements of cartilage health and performance even after short, clinically relevant exposure times, and may be useful in the clinic as a means for detecting early signs of cartilage pathology.

T2* Mapping for Hip Joint Cartilage Assessment: Pre-MRI Exercise and Time of Imaging Do Not Bias the T2* Measurement in Asymptomatic Volunteers

Objective To identify if the time of day and pre-imaging exercise matter while performing T2* mapping of hip joint cartilage at 3 T. Design Nine asymptomatic healthy volunteers (mean age 27.4 ± 4.0 years) with no obvious morphological evidence of cartilage damage were enrolled. The MRI protocol included a double-echo steady state (DESS) sequence for morphological cartilage assessment and a multi-echo data image combination sequence for the T2* measurement. T2* values were obtained between 8 and 11 a.m., between 3 and 6 p.m., and after 50 knee-bends at several time points of each measurement (0, 15, 30, 45, 60 minutes). Results We observed no differences ( P = 0.47) between the T2* values obtained in the morning (T2* = 22.9 ± 3.0 ms) and those measured in the afternoon (T2* = 23.2 ± 3.2 ms). We also observed no statistically significant differences between the T2* values at different time points ( P = 0.67) or after 50 knee-bends ( P = 0.43). Conclusions Timing of the scan and pre-imaging exercise clearly did not matter in this modality. This study consolidates the value of T2* imaging in hip joint cartilage that seems to be independent of diurnal effects and physical activity prior to MRI.

Value of delayed gadolinium-enhanced magnetic resonance imaging of cartilage for the pre-operative assessment of cervical intervertebral discs

The study was performed to preoperatively assess the cartilage integrity of cervical intervertebral discs (IVDs) using Delayed Gadolinium-Enhanced Magnetic Resonance Imaging of Cartilage (dGEMRIC). Therefore, 53 cervical intervertebral discs of nine preoperative patients with neck and shoulder/arm pain scheduled for discectomy (five females, four males; mean age: 47.1 ± 8.4 years; range: 36-58 years) were included for biochemical analysis in this retrospective study. The patients underwent 3T magnetic resonance imaging (MRI) including biochemical imaging with dGEMRIC and morphological, sagittal T2 weighted (T2w) imaging. Cervical IVDs were rated using an MRI based grading system for cervical IVDs on T2w images. Region-of-interest measurements were performed in the nucleus pulposus (NP) and annulus fibrosus (AF) and a dGEMRIC index was calculated. Our results demonstrated that IVDs scheduled for discectomy showed significantly lower dGEMRIC index compared to IVDs that did not require surgical intervention in NP and AF (NP: 898.4 ± 191.9 ms vs. 1,150.3 ± 320.7 ms, p = 0.008; AF: 738.7 ± 183.8 ms vs. 984.6 ± 178.9 ms, p = 0.008). For Miyazaki score 3, the dGEMRIC indices were significantly lower in IVDs scheduled for surgery compared to non-operated discs for NP (p = 0.043) and AF (p = 0.018). In conclusion we could demonstrate that biochemical imaging with dGEMRIC is feasible in cervical IVDs. Significantly lower dGEMRIC index suggested GAG depletion in degenerated cervical IVD, scheduled for discectomy. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1824-1830, 2017.

Imaging in Osteoarthritis

With technologic advances and the availability of sophisticated computer software and analytical strategies, imaging plays an increasingly important role in understanding the disease process of osteoarthritis (OA). Radiography has limitations in that it can visualize only limited features of OA, such as osteophytes and joint space narrowing, but remains the most commonly used modality for establishing an imaging-based diagnosis of OA. This article describes the roles and limitations of different imaging modalities and discusses the optimum imaging protocol, imaging diagnostic criteria of OA, differential diagnoses, and what the referring physician needs to know.

Both 3-T dGEMRIC and Acetabular-Femoral T2 Difference May Detect Cartilage Damage at the Chondrolabral Junction

BACKGROUND

In addition to case reports of gadolinium-related toxicities, there are increasing theoretical concerns about the use of gadolinium for MR imaging. As a result, there is increasing interest in noncontrast imaging techniques for biochemical cartilage assessment. Among them, T2 mapping holds promise because of its simplicity, but its biophysical interpretation has been controversial.

QUESTIONS/PURPOSES

We sought to determine whether (1) 3-T delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) and T2 mapping are both capable of detecting cartilage damage at the chondrolabral junction in patients with femoroacetabular impingement (FAI); and (2) whether there is a correlation between these two techniques for acetabular and femoral head cartilage assessment.

METHODS

Thirty-one patients with hip-related symptoms resulting from FAI underwent a preoperative 3-T MRI of their hip that included dGEMRIC and T2 mapping (symptomatic group, 16 women, 15 men; mean age, 27 ± 8 years). Ten volunteers with no symptoms according to the WOMAC served as a control (asymptomatic group, seven women, three men; mean age, 28 ± 3 years). After morphologic cartilage assessment, acetabular and femoral head cartilages were graded according to the modified Outerbridge grading criteria. In the midsagittal plane, single-observer analyses of precontrast T1 values (volunteers), the dGEMRIC index (T1_Gd, patients), and T2 mapping values (everyone) were compared in acetabular and corresponding femoral head cartilage at the chondrolabral junction of each hip by region-of-interest analysis.

RESULTS

In the symptomatic group, T1_Gd and T2 values were lower in the acetabular cartilage compared with corresponding femoral head cartilage (T1_Gd: 515 ± 165 ms versus 650 ± 191 ms, p < 0.001; T2: 39 ± 8 ms versus 46 ± 10 ms, p < 0.001). In contrast, the asymptomatic group demonstrated no differences in T1 and T2 values for the acetabular and femoral cartilages with the numbers available (T1: 861 ± 130 ms versus 860 ± 182 ms, p = 0.98; T2: 43 ± 7 ms versus 42 ± 6 ms, p = 0.73). No correlation with the numbers available was noted between the modified Outerbridge grade and T1, T1_Gd, or T2 as well as between T2 and either T1 or T1_Gd.

CONCLUSIONS

Without the need for contrast media application, T2 mapping may be a viable alternative to dGEMRIC when assessing hip cartilage at the chondrolabral junction. However, acquisition-related phenomena as well as regional variations in the microstructure of hip cartilage necessitate an internal femoral head cartilage control when interpreting these results.

LEVEL OF EVIDENCE

Level IV, diagnostic study.

Electromechanical probe and automated indentation maps are sensitive techniques in assessing early degenerated human articular cartilage

Recent advances in the development of new drugs to halt or even reverse the progression of Osteoarthritis at an early-stage requires new tools to detect early degeneration of articular cartilage. We investigated the ability of an electromechanical probe and an automated indentation technique to characterize entire human articular surfaces for rapid non-destructive discrimination between early degenerated and healthy articular cartilage. Human cadaveric asymptomatic articular surfaces (four pairs of distal femurs and four pairs of tibial plateaus) were used. They were assessed ex vivo: macroscopically, electromechanically, (maps of the electromechanical quantitative parameter, QP, reflecting streaming potentials), mechanically (maps of the instantaneous modulus, IM), and through cartilage thickness. Osteochondral cores were also harvested from healthy and degenerated regions for histological assessment, biochemical analyses, and unconfined compression tests. The macroscopic visual assessment delimited three distinct regions on each articular surface: Region I was macroscopically degenerated, region II was macroscopically normal but adjacent to regions I and III was the remaining normal articular surface. Thus, each extracted core was assigned to one of the three regions. A mixed effect model revealed that only the QP (p < 0.0001) and IM (p < 0.0001) were able to statistically discriminate the three regions. Effect size was higher for QP and IM than other assessments, indicating greater sensitivity to distinguish early degeneration of cartilage. When considering the mapping feature of the QP and IM techniques, it also revealed bilateral symmetry in a moderately similar distribution pattern between bilateral joints. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:858-867, 2017.

Juvenile Particulate Osteochondral Allograft for Treatment of Osteochondral Lesions of the Talus: Detection of Altered Repair Tissue Biochemical Composition Using 7 Tesla MRI and T2 Mapping

During the previous 2 decades, numerous surgical procedures have become available to treat osteochondral lesions of the talus. The objective of the present study was to use 7 Tesla (7T) magnetic resonance imaging (MRI) to quantify and compare T2 values (a marker of collagen architecture) of native tibiotalar cartilage and cartilage repair tissue in patients treated with a juvenile particulate allograft for osteochondral lesions of the talus. The institutional review board approved the present study, and all subjects provided written informed consent. We scanned the ankles of 7 cartilage repair patients using a 7T MRI scanner with a multi-echo spin-echo sequence to measure the cartilage T2 values. We assessed the cartilage T2 values in the talar repair tissue, adjacent native talar cartilage, and overlying tibial cartilage. We compared the differences between groups using the paired t test. The talar cartilage repair tissue demonstrated greater mean T2 relaxation times compared with the native adjacent talar cartilage (64.88 ± 12.23 ms versus 49.56 ± 7.82 ms; p = .043). The tibial cartilage regions overlying these talar cartilage regions demonstrated a trend toward greater T2 relaxation times (77.00 ± 31.29 ms versus 59.52 ± 7.89 ms; p = .067). 7T MRI can detect differences in T2 values in cartilage repair tissue compared with native cartilage and could be useful for monitoring the status of cartilage health after surgical intervention.

A narrative overview of the current status of MRI of the hip and its relevance for osteoarthritis research - what we know, what has changed and where are we going?

OBJECTIVE

To review and discuss the role of magnetic resonance imaging (MRI) in the context of hip osteoarthritis (OA) research.

DESIGN

The content of this narrative review, based on an extensive PubMed database research including English literature only, describes the advances in MRI of the hip joint and its potential usefulness in hip OA research, reviews the relevance of different MRI features in regard to symptomatic and structural progression in hip OA, and gives an outlook regarding future use of MRI in hip OA research endeavors.

RESULTS

Recent technical advances have helped to overcome many of the past difficulties related to MRI assessment of hip OA. MRI-based morphologic scoring systems allow for detailed assessment of several hip joint tissues and, in combination with the recent advances in MRI, may increase reproducibility and sensitivity to change. Compositional MRI techniques may add to our understanding of disease onset and progression. Knowledge about imaging pitfalls and anatomical variants is crucial to avoid misinterpretation. In comparison to research on knee OA, the associations between MRI features and the incidence and progression of disease as well as with clinical symptoms have been little explored. Anatomic alterations of the hip joint as seen in femoro-acetabular impingement (FAI) seem to play a role in the onset and progression of structural damage.

CONCLUSIONS

With the technical advances occurring in recent years, MRI may play a major role in investigating the natural history of hip OA and provide an improved method for assessment of the efficacy of new therapeutic approaches.

Changes in Cartilage and Tendon Composition of Patients With Type I Diabetes Mellitus: Identification by Quantitative Sodium Magnetic Resonance Imaging at 7 T

OBJECTIVE

The aim of this study was to investigate possible biochemical alterations in tendons and cartilage caused by type 1 diabetes mellitus (DM1), using quantitative in vivo 7 T sodium magnetic resonance (MR) imaging.

MATERIALS AND METHODS

The institutional review board approved this prospective study, and written informed consent was obtained. Eight DM1 patients with no history of knee trauma and 9 healthy age- and weight-matched volunteers were examined at 7 T using dedicated knee coils.All participants underwent morphological and sodium MR imaging. Region-of-interest analysis was performed manually for the non-weight-bearing area of the femoral condyle cartilage and for the patella tendon. Two readers read the image data sets independently, twice, for intrareader and interreader agreement. Normalized mean sodium signal intensity (NMSI) values were compared between patients and volunteers for each reader using analysis of variance.

RESULTS

On morphological images, cartilage in the non-weight-bearing area and the patellar tendon was intact in all patients. On sodium MR imaging, bivariate analysis of variance showed significantly lower mean NMSI values in the cartilage (P = 0.008) and significantly higher values in the tendons (P = 0.025) of patients compared with those of volunteers.

CONCLUSION

Our study showed significantly different NMSI values between DM1 patients and matched volunteers. Differences observed in the cartilage and tendon might be associated with a DM1-related alteration of biochemical composition that occurs before it can be visualized on morphological MR sequences.

T2* mapping of subtalar cartilage: Precision and association between anatomical variants and cartilage composition

Hindfoot arthritis is an important contributor to foot pain and physical disability. While the subtalar joint (STJ) is most frequently affected, anatomical variants such as facet configuration were suggested to further STJ cartilage deterioration. T2* mapping enables detection of ultra-structural cartilage change, particularly in thin cartilage layers, but its feasibility in the STJ has not yet been evaluated. The purpose of this study was to evaluate segmentation consistency and inter-scan short-term precision error of T2* mapping of talocalcaneal cartilage and to investigate the relationship between facet configuration and STJ T2* values. Using 3Tesla morphological magnetic resonance imaging, STJ configuration was categorized according to the degree of fusion between anterior, medial, or posterior facets. Subsequently, two repeats of multi-echo gradient recalled echo sequences were performed to obtain T2* maps with repositioning. Segmentation consistency of T2* values attained an ICC of 0.90 (95%CI 0.69-0.99). Precision errors comprised a coefficient of variation (CV) ranging 0.01-0.05, corresponding to a root mean square CV of 0.03-0.04. A 2-joint configuration type (i.e., fused anterior-medial facets) was significantly associated with a decrease in posterior facet T2* values (β = -0.6, p = 0.046). STJ T2* mapping is a reliable method requiring at least a 4% difference within people to enable detection of significant change. Anatomical variants in STJ configuration were associated with T2* values with the more stable 3-joint types exhibiting more favorable cartilage outcomes. Longer-term larger-scaled studies focusing on arthritis pathology are needed to further support the use of T2* mapping in hindfoot disease monitoring. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1969-1976, 2016.

Imaging of femoroacetabular impingement-current concepts

Following the recognition of femoroacetabular impingement (FAI) as a clinical entity, diagnostic tools have continuously evolved. While the diagnosis of FAI is primarily made based on the patients' history and clinical examination, imaging of FAI is indispensable. Routine diagnostic work-up consists of a set of plain radiographs, magnetic resonance imaging (MRI) and MR-arthrography. Recent advances in MRI technology include biochemically sensitive sequences bearing the potential to detect degenerative changes of the hip joint at an early stage prior to their appearance on conventional imaging modalities. Computed tomography may serve as an adjunct. Advantages of CT include superior bone to soft tissue contrast, making CT applicable for image-guiding software tools that allow evaluation of the underlying dynamic mechanisms causing FAI. This article provides a summary of current concepts of imaging in FAI and a review of the literature on recent advances, and their application to clinical practice.

Imaging of Osteoarthritis in Geriatric Patients

Imaging of osteoarthritis (OA) in the elderly is gaining importance because of the aging population. It requires knowledge about findings relevant for patient management and others which are abnormal findings, but part of normal aging without relevance for patient management due to lack of clinical symptoms. This review will provide information on what imaging techniques are best used for knee OA and how to systematically assess knee joint structures in order to cover the most common asymptomatic and symptomatic MR findings in OA. We will discuss which findings are typically found in older patients and which are likely to progress to severe pain and disability, finally leading to total joint replacement. The review may aid radiologists and referring clinicians to better understand the evolution of symptomatic OA and the current or future clinical significance of the most common symptomatic and asymptomatic findings.

In vivo deformation of thin cartilage layers: Feasibility and applicability of T2* mapping

The objectives of this study were as follows: (i) to assess segmentation consistency and scan precision of T2* mapping of human tibio-talar cartilage, and (ii) to monitor changes in T2* relaxation times of ankle cartilage immediately following a clinically relevant in vivo exercise and during recovery. Using multi-echo gradient recalled echo sequences, averaged T2* values were calculated for tibio-talar cartilage layers in 10 healthy volunteers. Segmentation consistency and scan precision were determined from two repeated segmentations and two repeated acquisitions with repositioning, respectively. Subsequently, acute in vivo cartilage loading responses were monitored by calculating averaged tibio-talar T2* values at rest, immediately after (i.e., deformation) and at 15 min (i.e., recovery) following a 30-repetition knee bending exercise. Precision errors attained 4-6% with excellent segmentation consistency point estimates (i.e., intra-rater ICC of 0.95) and acceptable limits of confidence. At deformation, T2* values were increased in both layers [+16.1 (10.7)%, p = 0.004 and +17.3 (15.3)%, p = 0.023, for the talus and tibia, respectively] whereas during recovery no significant changes could be established when comparing to baseline [talar cartilage: +5.2 (8.2)%, p = 0.26 and tibial cartilage: +6.6 (10.4)%, p = 0.23]. T2* mapping is a viable method to monitor deformational behavior in thin cartilage layers such as ankle cartilage. Longitudinal changes in T2* can be reliably appraised and require at least 4-6% differences to ascertain statistical significance. The ability to detect considerable change even after non-strenuous loading events, endorses T2* mapping as an innovative method to evaluate the effects of therapeutic exercise on thin cartilage layers. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:771-778, 2016.

Biologic Treatments for Sports Injuries II Think Tank-Current Concepts, Future Research, and Barriers to Advancement, Part 3: Articular Cartilage

Focal chondral defects of the articular surface are a common occurrence in the field of orthopaedics. These isolated cartilage injuries, if not repaired surgically with restoration of articular congruency, may have a high rate of progression to posttraumatic osteoarthritis, resulting in significant morbidity and loss of function in the young, active patient. Both isolated and global joint disease are a difficult entity to treat in the clinical setting given the high amount of stress on weightbearing joints and the limited healing potential of native articular cartilage. Recently, clinical interest has focused on the use of biologically active compounds and surgical techniques to regenerate native cartilage to the articular surface, with the goal of restoring normal joint health and overall function. This article presents a review of the current biologic therapies, as discussed at the 2015 American Orthopaedic Society for Sports Medicine (AOSSM) Biologics Think Tank, that are used in the treatment of focal cartilage deficiencies. For each of these emerging therapies, the theories for application, the present clinical evidence, and specific areas for future research are explored, with focus on the barriers currently faced by clinicians in advancing the success of these therapies in the clinical setting.

An experimental study on the assessment of rabbit hepatic fibrosis by using magnetic resonance T1ρ imaging

OBJECTIVE

To explore the correlation between the T1ρ values of liver and liver fibrosis by using magnetic resonance (MR) T1ρ imaging.

MATERIALS AND METHODS

The study consisted of the control group and the hepatic fibrosis (HF) group. Carbon tetrachloride (CCl4) injection was performed once a week for 10 weeks (week 1-10) in the HF group which was divided into 5 subgroups and underwent MR examinations at weeks 4, 5, 6, 10, and 15 respectively post the first CCl4 injection (week 1). According to Scheuer Classification, the stage of HF of all rabbits was classified as S0-S4. Mann-Whitney U test was performed to compare the T1ρ values, and p<0.05 was considered statistically significant.

RESULTS

The control group included 11 rabbits and the HF group included 46 rabbits. The T1ρ values in the HF group tended to increase with the increase of CCl4 injection duration or in higher HF stages. The T1ρ values were significantly lower (p=0.036) in the control group (or the stage S0 group) (23.5±4.0 ms) compared to the whole HF group (or S1-S4 group) (26.1±3.7 ms), and dropped at week 15 (p=0.043) after the CCl4 injection was stopped at week 10.

CONCLUSION

T1ρ imaging is closely associated with the severity of HF and may play an important role in the early diagnosis of HF.

Sodium NMR/MRI for anisotropic systems

Sodium ((23)Na) plays a central role in many physiological processes, and its high NMR sensitivity makes it an attractive nucleus for biomedical NMR and MRI research. Many biological tissues contain structures such as fibers and membranes that impose anisotropic translational and rotational motions on the sodium ions. Translational motion can be studied by diffusion measurements. Anisotropic rotational motion results in non-vanishing quadrupolar interaction that it is best studied by exploiting multiple quantum coherences for (23)Na NMR spectroscopy and MRI. The current review covers the application of the various NMR techniques to the study of (23)Na in anisotropic compartments in cartilage, tendon, intervertebral discs, red blood cells, nervous system and muscles.

Comparison of multiple quantitative MRI parameters for characterization of the goat cartilage in an ongoing osteoarthritis: dGEMRIC, T1ρ and sodium

RATIONALE AND OBJECTIVES

Osteoarthritis (OA) is a degenerative joint disease leading to cartilage deterioration by loss of matrix, fibrillation, formation of fissures, and ultimately complete loss of the cartilage surface. Here, three magnetic resonance imaging (MRI) techniques, dGEMRIC (delayed Gadolinium enhanced MRI of cartilage; dG1=T1,post; dG2=1/T1,post-1/T1,pre), T1ρ,and sodium MRI, are compared in a preclinical in vivo study to evaluate the differences in their potential for cartilage characterization and to establish an examination protocol for a following clinical study.

MATERIALS AND METHODS

OA was induced in 12 caprine knees (6 control, 6 therapy). Adipose derived stem cells were injected afterwards as a treatment. The animals were examined healthy, 3 and 16 weeks postoperatively with all three MRI methods. Using statistical analysis, the OA development and the degree of correlation between the different MRI methods were determined.

RESULTS

A strong correlation was observed between the dGEMRIC indices dG1 and dG2 (r=-0.87) which differ only in considering or not considering the T1 baseline. Moderate correlations were found between T1ρ and dG1 (r=0.55), T1ρ and dG2 (r=0.47) and at last, sodium and dG1 (r=0.45). The correlations found in this study match to the biomarkers which the methods are sensitive to.

CONCLUSION

Even though the goat cartilage is significantly thinner than the human cartilage and even more in a degenerated cartilage, all three methods were able to characterize the cartilage over the whole period of time during an ongoing OA. Due to measurement and post processing optimizations, as well as the correlations detected in this work, the overall measurement time in future goat studies can be minimized. Moreover, an examination protocol for characterizing the cartilage in a clinical study was established.

Conventional and novel imaging modalities in osteoarthritis: current state of the evidence

PURPOSE OF REVIEW

Imaging modalities are currently an inseparable part of osteoarthritis diagnosis. In this review, we describe the current state of evidence regarding conventional and novel imaging modalities in evaluation of osteoarthritis. Modalities including radiography (qualitative and semi-quantitative assessments), ultrasonography, computed tomography [CT; conventional multidetector CT (MDCT), cone-beam CT (CBCT) and four-dimensional CT (4DCT)], MRI (MRI; semi-quantitative, quantitative and compositional) and PET and their applications are reviewed.

RECENT FINDINGS

Radiography is the modality of choice for initial assessment of osteoarthritis. However, due to its low sensitivity and specificity, numerous recent investigations have proposed MRI as a powerful addition to detect and grade osteoarthritis features, which are not apparent in radiography. Semi-quantitative MRI measurements are feasible to perform in routine clinical practice. Quantitative and compositional MRI measurements have extended the amount of information an MRI examination can provide regarding the three-dimensional shape and tissue composition of articular cartilage. 4DCT and CBCT are introduced as imaging examinations that may reveal biomechanical cartilage abnormalities in osteoarthritis joint by dynamic and weight-bearing evaluations, respectively. Recent PET studies may unveil the underlying metabolic activities that can be associated with osteoarthritis.

SUMMARY

In addition to the established role of radiographs, MRI is the advanced modality of choice for detection and quantification of various osteoarthritis features. 4DCT and CBCT may have specified applications when diagnosis of underlying motion abnormality or dynamic changes in weight-bearing situation is suspected. Future studies should elucidate the specific clinical applications of ultrasonography and PET.

Noninvasive assessment of osteoarthritis severity in human explants by multicontrast MRI

PURPOSE

Medical imaging has the potential to noninvasively diagnose early disease onset and monitor the success of repair therapies. Unfortunately, few reliable imaging biomarkers exist to detect cartilage diseases before advanced degeneration in the tissue.

METHOD

In this study, we quantified the ability to detect osteoarthritis (OA) severity in human cartilage explants using a multicontrast magnetic resonance imaging (MRI) approach, inclusive of novel displacements under applied loading by MRI, relaxivity measures, and standard MRI.

RESULTS

Displacements under applied loading by MRI measures, which characterized the spatial micromechanical environment by 2D finite and Von Mises strains, were strong predictors of histologically assessed OA severity, both before and after controlling for factors, e.g., patient, joint region, and morphology. Relaxivity measures, sensitive to local macromolecular weight and composition, including T1ρ, but not T1 or T2, were predictors of OA severity. A combined multicontrast approach that exploited spatial variations in tissue biomechanics and extracellular matrix structure yielded the strongest relationships to OA severity.

CONCLUSION

Our results indicate that combining multiple MRI-based biomarkers has high potential for the noninvasive measurement of OA severity and the evaluation of potential therapeutic agents used in the treatment of early OA in animal and human trials.

Compositional MRI techniques for evaluation of cartilage degeneration in osteoarthritis

Osteoarthritis (OA), a leading cause of disability, affects 27 million people in the United States and its prevalence is rising along with the rise in obesity. So far, biomechanical or behavioral interventions as well as attempts to develop disease-modifying OA drugs have been unsuccessful. This may be partly due to antiquated imaging outcome measures such as radiography, which are still endorsed by regulatory agencies such as the United States Food and Drug Administration (FDA) for use in clinical trials. Morphological magnetic resonance imaging (MRI) allows unparalleled multi-feature assessment of the OA joint. Furthermore, advanced MRI techniques also enable evaluation of the biochemical or ultrastructural composition of articular cartilage relevant to OA research. These compositional MRI techniques have the potential to supplement clinical MRI sequences in identifying cartilage degeneration at an earlier stage than is possible today using morphologic sequences only. The purpose of this narrative review is to describe compositional MRI techniques for cartilage evaluation, which include T2 mapping, T2* Mapping, T1 rho, dGEMRIC, gagCEST, sodium imaging and diffusion weighted imaging (DWI). We also reviewed relevant clinical studies that have utilized these techniques for the study of OA. The different techniques are complementary. Some focus on isotropy or the collagen network (e.g., T2 mapping) and others are more specific in regard to tissue composition, e.g., gagCEST or dGEMRIC that convey information on the GAG concentration. The application and feasibility of these techniques is also discussed, as they will play an important role in implementation in larger clinical trials and eventually clinical practice.

T2* mapping and delayed gadolinium-enhanced magnetic resonance imaging in cartilage (dGEMRIC) of humeral articular cartilage--a histologically controlled study

BACKGROUND

Cartilage biochemical imaging modalities that include the magnetic resonance imaging (MRI) techniques of T2* mapping (sensitive to water content and collagen fiber network) and delayed gadolinium-enhanced MRI of cartilage (dGEMRIC, sensitive to the glycosaminoglycan content) can be effective instruments for early diagnosis and reliable follow-up of cartilage damage. The purpose of this study was to provide T2* mapping and dGEMRIC values in various histologic grades of cartilage degeneration in humeral articular cartilage.

METHODS

A histologically controlled in vitro study was conducted that included human humeral head cartilage specimens with various histologic grades of cartilage degeneration. High-resolution, 3-dimensional (3D) T2* mapping and dGEMRIC were performed that enabled the correlation of MRI and histology data. Cartilage degeneration was graded according to the Mankin score, which evaluates surface morphology, cellularity, toluidine blue staining, and tidemark integrity. SPSS software was used for statistical analyses.

RESULTS

Both MRI mapping values decreased significantly (P < .001) with increasing cartilage degeneration. Spearman rank analysis revealed a significant correlation (correlation coefficients ranging from -0.315 to 0.784; P < .001) between the various histologic parameters and the T2* and T1Gd mapping values.

CONCLUSION

This study demonstrates the feasibility of 3D T2* and dGEMRIC to identify various histologic grades of cartilage damage of humeral articular cartilage. With regard to the advantages of these mapping techniques with high image resolution and the ability to accomplish a 3D biochemically sensitive imaging, we consider that these imaging techniques can make a positive contribution to the currently evolving science and practice of cartilage biochemical imaging.

Current knowledge and importance of dGEMRIC techniques in diagnosis of hip joint diseases

Accurate assessment of early hip joint cartilage alterations may help optimize patient selection and follow-up of hip joint preservation surgery. Delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) is sensitive to the glycosaminoglycan content in cartilage that is lost early in the development of osteoarthritis (OA). Hence, the dGEMRIC technique holds promise for the development of new diagnostic and therapeutic procedures. However, because of the location of the hip joint deep within the body and due to the fairly thin cartilage layers that require high spatial resolution, the diagnosis of early hip joint cartilage alterations may be problematic. The purpose of this review is to outline the current status of dGEMRIC in the assessment of hip joint cartilage. A literature search was performed with PubMed, using the terms "cartilage, osteoarthritis, hip joint, MRI, and dGEMRIC", considering all levels of studies. This review revealed that dGEMRIC can be reliably used in the evaluation of early stage cartilage pathology in various hip joint disorders. Modifications in the technique, such as the operation of three-dimensional imaging and dGEMRIC after intra-articular contrast medium administration, have expanded the range of application. Notably, the studies differ considerably in patient selection and technical prerequisites. Furthermore, there is a need for multicenter prospective studies with the required technical conditions in place to establish outcome based dGEMRIC data to obtain, in conjunction with clinical data, reliable threshold values for normal and abnormal cartilage, and for hips that may benefit from conservative or surgical treatment.

Advanced Imaging in Femoroacetabular Impingement: Current State and Future Prospects

Symptomatic femoroacetabular impingement (FAI) is now a known precursor of early osteoarthritis (OA) of the hip. In terms of clinical intervention, the decision between joint preservation and joint replacement hinges on the severity of articular cartilage degeneration. The exact threshold during the course of disease progression when the cartilage damage is irreparable remains elusive. The intention behind radiographic imaging is to accurately identify the morphology of osseous structural abnormalities and to accurately characterize the chondrolabral damage as much as possible. However, both plain radiographs and computed tomography (CT) are insensitive for articular cartilage anatomy and pathology. Advanced magnetic resonance imaging (MRI) techniques include magnetic resonance arthrography and biochemically sensitive techniques of delayed gadolinium-enhanced MRI of cartilage (dGEMRIC), T1rho (T1ρ), T2/T2* mapping, and several others. The diagnostic performance of these techniques to evaluate cartilage degeneration could improve the ability to predict an individual patient-specific outcome with non-surgical and surgical care. This review discusses the facts and current applications of biochemical MRI for hip joint cartilage assessment covering the roles of dGEMRIC, T2/T2*, and T1ρ mapping. The basics of each technique and their specific role in FAI assessment are outlined. Current limitations and potential pitfalls as well as future directions of biochemical imaging are also outlined.

Use of micro-computed tomography to evaluate the effects of exercise on preventing the degeneration of articular cartilage in tail-suspended rats

Space flight has been shown to induce bone loss and muscle atrophy, which could initiate the degeneration of articular cartilage. Countermeasures to prevent bone loss and muscle atrophy have been explored, but few spaceflight or ground-based studies have focused on the effects on cartilage degeneration. In this study, we investigated the effects of exercise on articular cartilage deterioration in tail-suspended rats. Thirty-two female Sprague-Dawley rats were randomly divided into four groups (n=8 in each): tail suspension (TS), tail suspension plus passive motion (TSP), tail suspension plus active exercise (TSA), and control (CON) groups. In the TS, TSP, and TSA groups, the rat hindlimbs were unloaded for 21 days by tail suspension. Next, the cartilage thickness and volume, and the attenuation coefficient of the distal femur were evaluated by micro-computed tomography (μCT). Histological analysis was used to assess the surface integrity of the cartilage, cartilage thickness, and chondrocytes. The results showed that: (1) the cartilage thickness on the distal femur was significantly lower in the TS and TSP groups compared with the CON and TSA groups; (2) the cartilage volume in the TS group was significantly lower compared with the CON, TSA, and TSP groups; and (3) histomorphology showed that the chondrocytes formed clusters where the degree of matrix staining was lower in the TS and TSP groups. There were no significant differences between any of these parameters in the CON and TSA groups. The cartilage thickness measurements obtained by μCT and histomorphology correlated well. In general, tail suspension could induce articular cartilage degeneration, but active exercise was effective in preventing this degeneration in tail-suspended rats.

OARSI Clinical Trials Recommendations: Knee imaging in clinical trials in osteoarthritis

Significant advances have occurred in our understanding of the pathogenesis of knee osteoarthritis (OA) and some recent trials have demonstrated the potential for modification of the disease course. The purpose of this expert opinion, consensus driven exercise is to provide detail on how one might use and apply knee imaging in knee OA trials. It includes information on acquisition methods/techniques (including guidance on positioning for radiography, sequence/protocol recommendations/hardware for magnetic resonance imaging (MRI)); commonly encountered problems (including positioning, hardware and coil failures, sequences artifacts); quality assurance (QA)/control procedures; measurement methods; measurement performance (reliability, responsiveness, validity); recommendations for trials; and research recommendations.