Magnetic resonance imaging of entheses. Part 1

Ultra-high field magnetic resonance imaging of the quadriceps tendon enthesis in healthy subjects

PURPOSE

Although enthesitis is a hallmark of several rheumatologic conditions, current imaging methods are still unable to characterize entheses changes because of the corresponding short transverse relaxation times (T2). A growing number of MR studies have used Ultra-High Field (UHF) MRI in order to assess low-T2 tissues e.g., tendon but never in humans. The purpose of the present study was to assess in vivo the enthesis of the quadriceps tendon in healthy subjects using UHF MRI.

METHODS

Eleven healthy subjects volunteered in an osteoarthritis imaging study. The inclusion criteria were: no knee trauma, Lequesne index = 0, less than 3 h of sport activities per week, and Kellgren and Lawrence grade = 0. 3D MR images were acquired at 7 T using GRE sequences and a T2* mapping. Regions of interest i.e., trabecular bone, subchondral bone, enthesis, and tendon body were identified, and T2* values were quantified and compared.

RESULTS

Quadriceps tendon enthesis was visible as a hyper-intense signal. The largest and the lowest T2* values were quantified in the subchondral bone region and the tendon body respectively. T2* value within subchondral bone was significantly higher than T2* value within the enthesis. T2* in subchondral bone region was significantly higher than the whole tendon body T2*.

CONCLUSION

A T2* gradient was observed along the axis from the enthesis toward the tendon body. It illustrates different water biophysical properties. These results provide normative values which could be used in the field of inflammatory rheumatologic diseases and mechanical disorders affecting the tendon.

[Principles of tendon healing at the shoulder and consequences for their treatment : Importance of platelet-rich plasma and regenerative medicine]

Tendon pathologies are a frequent cause of shoulder pain and can lead to significant decline in the quality of life. Conservative treatment is suitable for most tendon pathologies. In addition to classical conservative treatment options, such as physiotherapy, oral analgesia and infiltrations, there are a number of additive treatment options to promote structural tendon healing and clinical outcome. Furthermore, there are approaches to improve the results of the surgical treatment of tendon injuries by biological augmentation. The objective of this article is to give an overview of biological and regenerative therapeutic options in the treatment of tendon injuries of the shoulder. Therefore, the anatomical and molecular biological principles of the tendon structure and their importance for tendon healing are explained in order to highlight the various therapeutic options for daily practice. Biological augmentation procedures and regenerative medicine represent a promising therapeutic option for tendon injuries of the shoulder, however, the benefits are so far supported by little or no evidence at all.

The imaging features of the meniscal roots on isotropic 3D MRI in young asymptomatic volunteers

BACKGROUND

This study aimed to describe clearly the normal imaging features of the meniscal roots on the magnetic resonance imaging (MRI) with a 3-dimensional (3D) proton density-weighted (PDW) sequence at 3T.

METHODS

A total of 60 knees of 31 young asymptomatic volunteers were examined using a 3D MRI. The insertion patterns, constitution patterns, and MR signals of the meniscal roots were recorded.

RESULTS

The anterior root of the medial meniscus (ARMM), the anterior root of the lateral meniscus (ARLM), and the posterior root of the medial meniscus (PRMM) had 1 insertion site, whereas the posterior root of the lateral meniscus (PRLM) can be divided into major and minor insertion sites. The ARLM and the PRMM usually consisted of multiple fiber bundles (≥3), whereas the ARMM and the PRLM often consisted of a single fiber bundle. The ARMM and the PRLM usually appeared as hypointense, whereas the ARLM and the PRMM typically exhibited mixed signals.

CONCLUSIONS

The meniscal roots can be complex and diverse, and certain characteristics of them were observed on 3D MRI. Understanding the normal imaging features of the meniscal roots is extremely beneficial for further diagnosis of root tears.

Morphologic characterization of meniscal root ligaments in the human knee with magnetic resonance microscopy at 11.7 and 3 T

OBJECTIVE

To determine the feasibility of using MR microscopy to characterize the root ligaments of the human knee at both ultra-high-field (11.7 T) and high-field (3 T) strengths.

MATERIALS AND METHODS

Seven fresh cadaveric knees were used for this study. Six specimens were imaged at 11.7 T and one specimen at 3 T using isotropic or near-isotropic voxels. Histologic correlation was performed on the posteromedial root ligament of one specimen. Meniscal root ligament shape, signal intensity, and ultrastructure were characterized.

RESULTS

High-resolution, high-contrast volumetric images were generated from both MR systems. Meniscal root ligaments were predominantly oval in shape. Increased signal intensity was most evident at the posteromedial and posterolateral root ligaments. On the specimen that underwent histologic preparation, increased signal intensity corresponded to regions of enthesis fibrocartilage. Collagen fascicles were continuous between the menisci and root ligaments. Predominantly horizontal meniscal radial tie fibers continued into the root ligaments as vertical endoligaments.

CONCLUSION

MR microscopy can be used to characterize and delineate the distinct ultrastructure of the root ligaments on both ultra-high-field- and high-field-strength MR systems.

The influence of life history and sexual dimorphism on entheseal changes in modern humans and African great apes

Entheseal changes have been widely studied with regard to their correlation to biomechanical stress and their usefulness for biocultural reconstructions. However, anthropological and medical studies have demonstrated the marked influence of both age and sex on the development of these features. Studies of entheseal changes are mostly aimed in testing functional hypotheses and are mostly focused on modern humans, with few data available for non-human primates. The lack of comparative studies on the effect of age and sex on entheseal changes represent a gap in our understanding of the evolutionary basis of both development and degeneration of the human musculoskeletal system. The aim of the present work is to compare age trajectories and patterns of sexual dimorphism in entheseal changes between modern humans and African great apes. To this end we analyzed 23 postcranial entheses in a human contemporary identified skeletal collection (N = 484) and compared the results with those obtained from the analysis of Pan (N = 50) and Gorilla (N = 47) skeletal specimens. Results highlight taxon-specific age trajectories possibly linked to differences in life history schedules and phyletic relationships. Robusticity trajectories separate Pan and modern humans from Gorilla, whereas enthesopathic patterns are unique in modern humans and possibly linked to their extended potential lifespan. Comparisons between sexes evidence a decreasing dimorphism in robusticity from Gorilla, to modern humans to Pan, which is likely linked to the role played by size, lifespan and physical activity on robusticity development. The present study confirms previous hypotheses on the possible relevance of EC in the study of life history, pointing moreover to their usefulness in evolutionary studies.

Co-cultured tissue-specific scaffolds for tendon/bone interface engineering

The tendon/ligament-to-bone interface has a complex organization to enable transfer of forces through the tendon/ligament to the bone. The purpose of this study is to create a co-culture environment enabling a tissue-specific tendon region and tissue-specific bone region on a degradable scaffold, using NIH 3T3 fibroblast–deposited extracellular matrix and MC 3T3 osteoblast–deposited extracellular matrix, respectively. Before full characterization of the deposited extracellular matrix coating can be analyzed, co-culture parameters including culture medium and seeding technique should be addressed. An appropriate medium formulation was developed to reduce fibroblast to osteoblast mineralization by adjusting beta-glycerophosphate concentrations. Standard growth medium with fetal bovine serum + 3 mM beta-glycerophosphate + 25 µg/mL ascorbic acid was found to be the most suitable formulation evaluated in these study conditions. Seeding and cell migration studies of co-cultured fibroblast- and osteoblast-specific scaffolds were performed to identify whether tissue regions could be created on the scaffold. Fibroblast and osteoblast regions were successfully seeded and little to no cell migration was observed up to 42 h after seeding. Finally, a preliminary analysis of basic extracellular matrix components was measured in the fibroblast, osteoblast, and transition regions. Tissue-specific DNA, glycosaminoglycan, and collagen were found in uniform amounts on the scaffolds and were not different significantly between scaffold regions. In conclusion, initial steps to create tissue-specific fibroblast and osteoblast regions on a degradable scaffold were successful in preparation for further characterization investigations as a tendon-to-bone interface scaffold.

Magnetic resonance imaging of pelvic entheses--a systematic comparison between short tau inversion recovery (STIR) and T1-weighted, contrast-enhanced, fat-saturated sequences

OBJECTIVE

To assess the contribution of contrast material in detecting and evaluating enthesitis of pelvic entheses by MRI.

MATERIALS AND METHODS

Sixty-seven hip or pelvic 1.5-T MRIs (30:37 male:female, mean age: 53 years) were retrospectively evaluated for the presence of hamstring and gluteus medius (GM) enthesitis by two readers (a resident and an experienced radiologist). Short tau inversion recovery (STIR) and T1-weighted pre- and post-contrast (T1+Gd) images were evaluated by each reader at two sessions. A consensus reading of two senior radiologists was regarded as the gold standard. Clinical data was retrieved from patients' referral form and medical files. Cohen's kappa was used for intra- and inter-observer agreement calculation. Diagnostic properties were calculated against the gold standard reading.

RESULTS

A total of 228 entheses were evaluated. Gold standard analysis diagnosed 83 (36%) enthesitis lesions. Intra-reader reliability for the experienced reader was significantly (p = 0.0001) higher in the T1+Gd images compared to the STIR images (hamstring: k = 0.84/0.45, GM: k = 0.84/0.47). Sensitivity and specificity increased from 0.74/0.8 to 0.87/0.9 in the STIR images and T1+Gd sequences. Intra-reader reliability for the inexperienced reader was lower (p > 0.05).

CONCLUSIONS

Evidence showing that contrast material improves the reliability, sensitivity, and specificity of detecting enthesitis supports its use in this setting.

Imaging the hard/soft tissue interface

Interfaces between different tissues play an essential role in the biomechanics of native tissues and their recapitulation is now recognized as critical to function. As a consequence, imaging the hard/soft tissue interface has become increasingly important in the area of tissue engineering. Particularly as several biotechnology based products have made it onto the market or are close to human trials and an understanding of their function and development is essential. A range of imaging modalities have been developed that allow a wealth of information on the morphological and physical properties of samples to be obtained non-destructively in vivo or via destructive means. This review summarizes the use of a selection of imaging modalities on interfaces to date considering the strengths and weaknesses of each. We will also consider techniques which have not yet been utilized to their full potential or are likely to play a role in future work in the area.

Quantitative parametric MRI of articular cartilage: a review of progress and open challenges

With increasing life expectancies and the desire to maintain active lifestyles well into old age, the impact of the debilitating disease osteoarthritis (OA) and its burden on healthcare services is mounting. Emerging regenerative therapies could deliver significant advances in the effective treatment of OA but rely upon the ability to identify the initial signs of tissue damage and will also benefit from quantitative assessment of tissue repair in vivo. Continued development in the field of quantitative MRI in recent years has seen the emergence of techniques able to probe the earliest biochemical changes linked with the onset of OA. Quantitative MRI measurements including T(1), T(2) and T(1ρ) relaxometry, diffusion weighted imaging and magnetisation transfer have been studied and linked to the macromolecular structure of cartilage. Delayed gadolinium-enhanced MRI of cartilage, sodium MRI and glycosaminoglycan chemical exchange saturation transfer techniques are sensitive to depletion of cartilage glycosaminoglycans and may allow detection of the earliest stages of OA. We review these current and emerging techniques for the diagnosis of early OA, evaluate the progress that has been made towards their implementation in the clinic and identify future challenges in the field.

Tendon and ligament imaging

MRI and ultrasound are now widely used for the assessment of tendon and ligament abnormalities. Healthy tendons and ligaments contain high levels of collagen with a structured orientation, which gives rise to their characteristic normal imaging appearances as well as causing particular imaging artefacts. Changes to ligaments and tendons as a result of disease and injury can be demonstrated using both ultrasound and MRI. These have been validated against surgical and histological findings. Novel imaging techniques are being developed that may improve the ability of MRI and ultrasound to assess tendon and ligament disease.

Review. The Agfa Mayneord lecture: MRI of short and ultrashort T₂ and T₂* components of tissues, fluids and materials using clinical systems

A variety of techniques are now available to directly or indirectly detect signal from tissues, fluids and materials that have short, ultrashort or supershort T₂ or T₂* components. There are also methods of developing image contrast between tissues and fluids in the short T₂ or T₂* range that can provide visualisation of anatomy, which has not been previously seen with MRI. Magnetisation transfer methods can now be applied to previously invisible tissues, providing indirect access to supershort T₂ components. Particular methods have been developed to target susceptibility effects and quantify them after correcting for anatomical distortion. Specific methods have also been developed to image the effects of magnetic iron oxide particles with positive contrast. Major advances have been made in techniques designed to correct for loss of signal and gross image distortion near metal. These methods are likely to substantially increase the range of application for MRI.

Psoriatic arthritis: correlation between imaging and pathology

Psoriatic arthritis (PsA) is an archetypal type of spondyloarthritis, but may have some features of rheumatoid arthritis, namely a small joint polyarthritis pattern. Most of these features are well demonstrated on imaging, and as a result, imaging has helped us to better understand the pathophysiology of PsA. Although the unique changes of PsA such as the "pencil-in-cup" deformities and periostitis are commonly shown on conventional radiography, PsA affects all areas of joints, with enthesitis being the predominant pathology. Imaging, especially magnetic resonance imaging (MRI) and ultrasonography, has allowed us to explain the relationships between enthesitis, synovitis (or the synovio-entheseal complex) and osteitis or bone oedema in PsA. Histological studies have complemented the imaging findings, and have corroborated the MRI changes seen in the skin and nails in PsA. The advancement in imaging technology such as high-resolution "microscopy" MRI and whole-body MRI, and improved protocols such as ultrashort echo time, will further enhance our understanding of the disease mechanisms. The ability to demonstrate very early pre-clinical changes as shown by ultrasonography and bone scintigraphy may eventually provide a basis for screening for disease and will further improve the understanding of the link between skin and joint disease.

Imaging of seronegative spondyloarthritis

Magnetic resonance imaging (MRI) and ultrasonography (US) are useful adjuncts in the diagnosis of seronegative spondyloarthritides (SpA); a group of diseases that present early at a stage when radiographic assessment is invariably normal. This chapter will review how MRI and US can be used in the evaluation of early SpA. The diffuse osteitis/enthesitis on MRI may serve as a diagnostic hallmark for SpA spinal disease, but needs confirmatory studies for comparison with other spinal pathologies. MRI is the modality of choice for monitoring axial disease in anti-tumour necrosis factor (TNF) therapy responses in the research environment, but it is not yet certain whether this will be relevant in clinical practice. Anti-TNF therapy may be associated with regression of MRI-determined osteitis, but retardation of associated bony fusion is debatable. MRI and US are still undergoing evaluation for the diagnosis of enthesitis of the appendicular skeleton; US, in particular, shows promise at these sites.