Evaluation of human knee meniscus biopsies with near-infrared, reflectance confocal microscopy. A pilot study

Correlations of characteristics with tissue involvement in knee gouty arthritis: Magnetic resonance imaging analysis

Objective

This study investigates the MRI features of knee gouty arthritis (KGA), examines its relationship with the extent of tissue involvement, and assesses whether risk factors can predict KGA.

Materials and methods

Patients diagnosed with KGA underwent MRI examinations, and two independent observers retrospectively analyzed data from 44 patients (49 knees). These patients were divided into mild and severe groups based on tissue involvement observed during arthroscopy. MRI features were summarized, and the intraclass correlation coefficient evaluated interobserver reproducibility. Single-factor analysis compared clinical indicators and MRI features between groups, while Cramer's V coefficient assessed correlations. Multivariate logistic regression identified predictors of tissue involvement extent, and a ROC curve evaluated diagnostic performance.

Results

Among 49 knees, 18 had mild and 31 had severe tissue involvement. Key MRI features included ligament sketch-like changes, meniscal urate deposition, irregularly serrated cartilage changes, low-signal signs within joint effusion, synovial proliferation, Hoffa's fat pad synovitis, gouty tophi, bone erosion, and bone marrow edema. The interobserver reliability of the MRI features was good. Significant differences (P < 0.05) were observed between the groups for anterior cruciate ligament (ACL) sketch-like changes, Hoffa's fat pad synovitis, and gouty tophi. ACL sketch-like changes (r = 0.309), Hoffa's fat pad synovitis (r = 0.309), and gouty tophi (r = 0.408) were positively correlated with the extent of tissue involvement (P < 0.05). ACL sketch-like changes (OR = 9.019, 95 % CI: 1.364-61.880), Hoffa's fat pad synovitis (OR = 6.472, 95 % CI: 1.041-40.229), and gouty tophi (OR = 5.972, 95 % CI: 1.218-29.276) were identified as independent predictors of tissue involvement extent (P < 0.05). The area under the ROC curve was 0.862, with a sensitivity of 67.70 %, specificity of 94.40 %, and accuracy of 79.14 %.

Conclusion

This comprehensive analysis of MRI features identifies ligament sketch-like changes, meniscal urate deposition, and low-signal signs within joint effusion as characteristic MRI manifestations of KGA. Irregular cartilage changes are valuable for differential diagnosis in young and middle-aged patients. ACL sketch-like changes, Hoffa's fat pad synovitis, and gouty tophi correlate with tissue involvement severity and are critical in predicting and assessing the extent of tissue involvement in KGA.

In Situ Loading and Time-Resolved Synchrotron-Based Phase Contrast Tomography for the Mechanical Investigation of Connective Knee Tissues: A Proof-of-Concept Study

Articular cartilage and meniscus transfer and distribute mechanical loads in the knee joint. Degeneration of these connective tissues occurs during the progression of knee osteoarthritis, which affects their composition, microstructure, and mechanical properties. A deeper understanding of disease progression can be obtained by studying them simultaneously. Time-resolved synchrotron-based X-ray phase-contrast tomography (SR-PhC-µCT) allows to capture the tissue dynamics. This proof-of-concept study presents a rheometer setup for simultaneous in situ unconfined compression and SR-PhC-µCT of connective knee tissues. The microstructural response of bovine cartilage (n = 16) and meniscus (n = 4) samples under axial continuously increased strain, or two steps of 15% strain (stress-relaxation) is studied. The chondrocyte distribution in cartilage and the collagen fiber orientation in the meniscus are assessed. Variations in chondrocyte density reveal an increase in the top 40% of the sample during loading, compared to the lower half. Meniscus collagen fibers reorient perpendicular to the loading direction during compression and partially redisperse during relaxation. Radiation damage, image repeatability, and image quality assessments show little to no effects on the results. In conclusion, this approach is highly promising for future studies of human knee tissues to understand their microstructure, mechanical response, and progression in degenerative diseases.

High angular resolution diffusion imaging (HARDI) of porcine menisci: a comparison of diffusion tensor imaging and generalized q-sampling imaging

Background

Diffusion magnetic resonance imaging (MRI) allows for the quantification of water diffusion properties in soft tissues. The goal of this study was to characterize the 3D collagen fiber network in the porcine meniscus using high angular resolution diffusion imaging (HARDI) acquisition with both diffusion tensor imaging (DTI) and generalized q-sampling imaging (GQI).

Methods

Porcine menisci (n=7) were scanned ex vivo using a three-dimensional (3D) HARDI spin-echo pulse sequence with an isotropic resolution of 500 µm at 7.0 Tesla. Both DTI and GQI reconstruction techniques were used to quantify the collagen fiber alignment and visualize the complex collagen network of the meniscus. The MRI findings were validated with conventional histology.

Results

DTI and GQI exhibited distinct fiber orientation maps in the meniscus using the same HARDI acquisition. We found that crossing fibers were only resolved with GQI, demonstrating the advantage of GQI over DTI to visualize the complex collagen fiber orientation in the meniscus. Furthermore, the MRI findings were consistent with conventional histology.

Conclusions

HARDI acquisition with GQI reconstruction more accurately resolves the complex 3D collagen architecture of the meniscus compared to DTI reconstruction. In the future, these technologies have the potential to nondestructively assess both normal and abnormal meniscal structure.

Quantitative three-dimensional collagen orientation analysis of human meniscus posterior horn in health and osteoarthritis using micro-computed tomography

OBJECTIVE

Knee osteoarthritis (OA) is associated with meniscal degeneration that may involve disorganization of the meniscal collagen fiber network. Our aims were to quantitatively analyze the microstructural organization of human meniscus samples in 3D using micro-computed tomography (μCT), and to compare the local microstructural organization between OA and donor samples.

METHOD

We collected posterior horns of both medial and lateral human menisci from 10 end-stage medial compartment knee OA patients undergoing total knee replacement (medial & lateral OA) and 10 deceased donors without knee OA (medial & lateral donor). Posterior horns were dissected and fixed in formalin, dehydrated in ascending ethanol concentrations, treated with hexamethyldisilazane (HMDS), and imaged with μCT. We performed local orientation analysis of collagenous microstructure in 3D by calculating structure tensors from greyscale gradients within selected integration window to determine the polar angle for each voxel.

RESULTS

In donor samples, meniscus bundles were aligned circumferentially around the inner border of meniscus. In medial OA menisci, the organized structure of collagen network was lost, and main orientation was shifted away from the circumferential alignment. Quantitatively, medial OA menisci had the lowest mean orientation angle compared to all groups, -24° (95%CI -31 to -18) vs medial donor and -25° (95%CI -34 to -15) vs lateral OA.

CONCLUSIONS

HMDS-based μCT imaging enabled quantitative analysis of meniscal collagen fiber bundles and their orientations in 3D. In human medial OA menisci, the collagen disorganization was profound with overall lower orientation angles, suggesting collagenous microstructure disorganization as an important part of meniscus degradation.

Collagenous Ultrastructure of the Torn Medial Meniscus Posterior Root: A Transmission Electron Microscopy Study

BACKGROUND

The collagen ultrastructure of torn medial meniscus posterior roots (MMPRs) has not been precisely defined.

PURPOSE

To investigate the ultrastructure of torn MMPRs, focusing on their collagen fibers, and to compare the collagen net architecture between intact and torn MMPRs using the Collagen Meniscal Architecture (CMA) scoring system.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Forty-three human meniscal specimens were obtained from 32 patients with osteoarthritis during total knee arthroplasty between January 2018 and November 2018. There were 23 specimens taken from patients with an MMPR tear and 20 taken from patients without an MMPR tear served as a control group. The presence of an MMPR tear was defined as a complete radial tear within 9 mm of the posterior root attachment. The collagen ultrastructure of the meniscal specimens was assessed with transmission electron microscopy using the CMA scoring system. Patient demographics included sex, age, and body mass index, and radiographic assessments included the Kellgren-Lawrence (K-L) grading system and the mechanical axis angle.

RESULTS

The median CMA score was significantly higher in torn MMPRs (5.5 [interquartile range, 3.5-6.0]) than in intact MMPRs (2.0 [interquartile range, 1.5-3.8]) (P < .001). When the CMA scores were converted to CMA grading, 23 torn MMPRs had 1 grade I, 9 grade II, and 13 grade III menisci. In 20 intact MMPRs, there were 12 grade I, 7 grade II, and 1 grade III menisci. No significant differences in sex, age, body mass index, K-L grade, or mechanical axis angle were found between groups.

CONCLUSION

This study showed that torn MMPRs had decreased numbers and disorganized courses of collagen fibers. The structural problem of torn MMPRs can negatively affect meniscal healing, function, and long-term survival after root repair.

CLINICAL RELEVANCE

These results might provide a histopathological reason for the low healing rate after MMPR repair.

The anatomical pathology of gout: a systematic literature review

Background

The aim of this systematic literature review was to comprehensively describe the anatomical pathology of tissues affected by gout.

Methods

We searched PubMed, The Cochrane Library, Excerpta Medica Database (EMBASE), and Web of Science Core Collection for all English language articles published before March 2018. Articles were included if they described the microscopic or macroscopic appearances of gout in human tissue.

Results

Four hundred and seventeen articles met inclusion criteria and were included in the review. Articles describing the anatomical pathology of gout in musculoskeletal structures, including bone, tendon and ligaments, synovium and cartilage, were most common. Articles describing skin and kidney pathology in gout were also common, with pathology in other sites such as visceral organs less common. At all sites, monosodium urate crystal deposition was reported, and the tophus was also described within many different tissues. During a gout flare, diffuse acute neutrophilic synovial inflammation was evident. The tophus was described as an organised chronic giant cell granulomatous structure consisting of monosodium urate crystals, innate and adaptive immune cells, and fibrovascular tissue.

Conclusions

Consistent with the clinical presentation of gout, most studies describing the anatomical pathology of gout report involvement of musculoskeletal structures, with monosodium urate crystal deposition and tophus the most common lesions described. This review details the anatomical pathology features of gout at affected sites.

Electronic supplementary material

The online version of this article (10.1186/s12891-019-2519-y) contains supplementary material, which is available to authorized users.

Maturation State and Matrix Microstructure Regulate Interstitial Cell Migration in Dense Connective Tissues

Few regenerative approaches exist for the treatment of injuries to adult dense connective tissues. Compared to fetal tissues, adult connective tissues are hypocellular and show limited healing after injury. We hypothesized that robust repair can occur in fetal tissues with an immature extracellular matrix (ECM) that is conducive to cell migration, and that this process fails in adults due to the biophysical barriers imposed by the mature ECM. Using the knee meniscus as a platform, we evaluated the evolving micromechanics and microstructure of fetal and adult tissues, and interrogated the interstitial migratory capacity of adult meniscal cells through fetal and adult tissue microenvironments with or without partial enzymatic digestion. To integrate our findings, a computational model was implemented to determine how changing biophysical parameters impact cell migration through these dense networks. Our results show that the micromechanics and microstructure of the adult meniscus ECM sterically hinder cell mobility, and that modulation of these ECM attributes via an exogenous matrix-degrading enzyme permits migration through this otherwise impenetrable network. By addressing the inherent limitations to repair imposed by the mature ECM, these studies may define new clinical strategies to promote repair of damaged dense connective tissues in adults.

Collagenous Ultrastructure of the Discoid Meniscus: A Transmission Electron Microscopy Study

BACKGROUND

The collagen ultrastructure of the discoid lateral meniscus (DLM) has not been precisely defined.

PURPOSE

To investigate the ultrastructure of the DLM, focusing on its collagen fibers, and to compare the collagen net architecture between intact and torn DLMs using the Collagen Meniscal Architecture (CMA) scoring system.

STUDY DESIGN

Descriptive laboratory study.

METHODS

Thirty specimens were taken from 30 patients with a diagnosis of a complete DLM using a 1-piece technique. The collagen ultrastructure of the DLMs was assessed with transmission electron microscopy. To evaluate the meniscal ultrastructure, the degree of collagen disruption, intrafibrillar edema, loss of banding, degree of collagen packing, and fibril size variability were assessed and graded from 1 (normal) to 3 (severe disarray) according to the CMA scoring system. The DLM specimens were divided into 3 groups according to the intrasubstance tear: the intact group (group I) had no tear; the simple tear group (group S) had a radial, longitudinal, or horizontal tear; and the complicated tear group (group C) had a complicated horizontal tear. Intact normal meniscus specimens (group N) were used as the control group.

RESULTS

There were 10 specimens in group I, 8 in group S, 12 in group C, and 13 in group N. In group I, there were 5 grade 1 and 5 grade 2 menisci; group S had 2 grade 1, 3 grade 2, and 3 grade 3 menisci; group C had 1 grade 1, 4 grade 2, and 7 grade 3 menisci; and group N had 4 grade 1, 7 grade 2, and 2 grade 3 menisci. A significant difference in the CMA score was observed between the 4 groups ( P = .009). The median CMA score was significantly lower in group I (2; range, 1-4) than in group S (4; range, 2-7) ( P = .041) and group C (4.25; range, 1.5-7) ( P = .018). No significant difference was found between groups S, C, and N.

CONCLUSION

Variability existed in the collagen ultrastructure of the DLM, and some DLMs showed a nearly normal ultrastructural pattern. The degree of density and disorganization of the collagen architecture in the DLM was related to the tear.

CLINICAL RELEVANCE

The study results might provide a histological background for partial meniscectomy in the treatment of a symptomatic DLM.

A Comprehensive Specimen-Specific Multiscale Data Set for Anatomical and Mechanical Characterization of the Tibiofemoral Joint

Understanding of tibiofemoral joint mechanics at multiple spatial scales is essential for developing effective preventive measures and treatments for both pathology and injury management. Currently, there is a distinct lack of specimen-specific biomechanical data at multiple spatial scales, e.g., joint, tissue, and cell scales. Comprehensive multiscale data may improve the understanding of the relationship between biomechanical and anatomical markers across various scales. Furthermore, specimen-specific multiscale data for the tibiofemoral joint may assist development and validation of specimen-specific computational models that may be useful for more thorough analyses of the biomechanical behavior of the joint. This study describes an aggregation of procedures for acquisition of multiscale anatomical and biomechanical data for the tibiofemoral joint. Magnetic resonance imaging was used to acquire anatomical morphology at the joint scale. A robotic testing system was used to quantify joint level biomechanical response under various loading scenarios. Tissue level material properties were obtained from the same specimen for the femoral and tibial articular cartilage, medial and lateral menisci, anterior and posterior cruciate ligaments, and medial and lateral collateral ligaments. Histology data were also obtained for all tissue types to measure specimen-specific cell scale information, e.g., cellular distribution. This study is the first of its kind to establish a comprehensive multiscale data set for a musculoskeletal joint and the presented data collection approach can be used as a general template to guide acquisition of specimen-specific comprehensive multiscale data for musculoskeletal joints.

Reflectance Confocal Microscopy Features of Focal Dermal Mucinosis Differ from Those Described for Basal Cell Carcinoma: Report of Two Cases

The purpose of this study was to describe the reflectance confocal microscopy (RCM) features of focal dermal mucinosis (FDM). The entity clinically and dermatoscopically mimics other diagnostic entities, most notably nonpigmented basal cell carcinoma. We describe two cases that highlight the dermatoscopic, RCM and histopathological attributes of FDM. RCM features such as dermal foci of dense collagen bundles oriented in the same direction, foci of haphazardly oriented thin collagen fibers separated by dark structureless areas and the absence of dark silhouettes and tumor islands are clues for FDM diagnosis. The FDM cases described here present consistent and particular RCM findings that appear to correlate well with the histopathological features of FDM. Therefore, RCM is a promising technology in diagnosing skin lesions and it use can avoid invasive procedures.

Macroscopic and histopathologic analysis of human knee menisci in aging and osteoarthritis

OBJECTIVE

Meniscus lesions following trauma or associated with osteoarthritis (OA) have been described, yet meniscus aging has not been systematically analyzed. The objectives of this study were to (1) establish standardized protocols for representative macroscopic and microscopic analysis, (2) improve existing scoring systems, and (3) apply these techniques to a large number of human menisci.

DESIGN

Medial and lateral menisci from 107 human knees were obtained and cut in two different planes (triangle/cross section and transverse/horizontal section as well) in three separate locations (middle portion, anterior and posterior horns). All sections included vascular and avascular regions and were graded for (1) surface integrity, (2) cellularity, (3) matrix/fiber organization and collagen alignment, and (4) Safranin-O staining intensity. The cartilage in all knee compartments was also scored.

RESULTS

The new macroscopic and microscopic grading systems showed high inter-reader and intra-reader intraclass correlation coefficients. The major age-related changes in menisci in joints with no or minimal OA included increased Safranin-O staining intensity, decreased cell density, the appearance of acellular zones, and evidence of mucoid degeneration with some loss of collagen fiber organization. The earliest meniscus changes occurred predominantly along the inner rim. Menisci from OA joints showed severe fibrocartilaginous separation of the matrix, extensive fraying, tears and calcification. Abnormal cell arrangements included decreased cellularity, diffuse hypercellularity along with cellular hypertrophy and abnormal cell clusters. In general, the anterior horns of both medial and lateral menisci were less affected by age and OA.

CONCLUSIONS

New standardized protocols and new validated grading systems allowed us to conduct a more systematic evaluation of changes in aging and OA menisci at a macroscopic and microscopic level. Several meniscus abnormalities appear to be specific to aging in the absence of significant OA. With aging the meniscal surface can be intact but abnormal matrix organization and cellularity were observed within the meniscal substance. The increased Safranin-O staining appears to represent a shift from fibroblastic to chondrocytic phenotype during aging and early degeneration.

Virtual biopsy of the joint tissues using near-infrared, reflectance confocal microscopy. A pilot study

Standard noninvasive imaging techniques applied to joints provide gross morphological features, insufficient for assessing histological detail. On the other hand, biopsying is invasive, time consuming, and may involve unwanted processing artifacts. Near-infrared reflectance confocal microscopy is a technique that allows serial, high-resolution optical sectioning through intact tissues without employing exogenous fluorescent stains. The aim of this work was to evaluate the potential utility of near-infrared reflectance confocal microscopy for providing immediate histological information on meniscus, articular cartilage, epiphyseal plate, bone, muscle, and tendon. Images from near-infrared reflectance confocal microscopy were compared with mirror routine histology sections. Characteristic architectural features were readily visualized in the three dimensions of space. Additionally, the use of experimental contrast agents highlighted the localization of nuclei. Limitations include penetration depth and minor optical artifacts. In conclusion, near-infrared reflectance confocal microscopy is a useful technique for immediate, nondestructive, serial "virtual" sectioning through intact tissues, being thus a potential adjunct to current imaging techniques in orthopedics.