Simultaneous ultrasound measurement of articular cartilage and subchondral bone

Effect of Knee Hyperextension on Femoral Cartilage Thickness in Stroke Patients

OBJECTIVE

Knee hyperextension is one of the most common compensatory mechanisms in stroke patients. The first aim of the study was to measure knee hyperextension and femoral cartilage thickness in stroke patients. The second aim was to compare the femoral cartilage thickness of the paretic and nonparetic limbs in stroke patients with and without knee hyperextension.

DESIGN

Forty stroke patients were included in the study. The patients were divided into two groups according to the presence of knee hyperextension based on kinematic analyses performed during walking with a three-dimensional motion analysis system. The medial femoral cartilage, lateral femoral cartilage, and intercondylar cartilage thicknesses of the paretic and nonparetic sides of the patients were measured by ultrasonography.

RESULTS

In the study group, medial femoral cartilage, intercondylar, and lateral femoral cartilage thicknesses were less on the paretic side than on the nonparetic side, while the femoral cartilage thicknesses on the paretic and nonparetic sides were similar in the control group. Paretic side medial femoral cartilage and intercondylar thicknesses were less in the study group compared with the control group, and lateral femoral cartilage thickness was similar between the two groups.

CONCLUSIONS

Knee hyperextension during walking causes femoral cartilage degeneration in stroke patients.Clinical Trial code: NCT05513157.

Detection of Subchondral Bone Microcirculatory Perfusion in Adults with Early Osteonecrosis of the Femoral Head Using Contrast-Enhanced Ultrasound: A Prospective Study

The aim of this study was to quantitatively assess subchondral bone microcirculation perfusion in adults with early osteonecrosis of the femoral head (ONFH) using contrast-enhanced ultrasound (CEUS) and to evaluate its correlation with the Association Research Circulation Osseous (ARCO) stage. We investigated 97 adult patients with definite ONFH by imaging a total of 155 hips, performing CEUS, storing images of CEUS processes at different ARCO stages and generating CEUS time-intensity curves (TICs) to obtain perfusion parameters. Differences in CEUS parameters at different ARCO stages were analyzed, and correlations were explored. A logistic regression model was constructed by incorporating the meaningful CEUS indicators. The CEUS parameters time to peak (TTP), peak intensity (PI), enhanced intensity (EI), ascending slope (AS), descending slope (DS) and area under the receiver operating characteristic curve (AUC) were significantly different in ARCO stage Ⅰ compared with stage ⅢA, and the same results were obtained in stage Ⅱ compared with stage ⅢA. However, there were no significant differences between stages Ⅰ and Ⅱ. The MTT (mean transit time) assay was not significantly different between the different stages. The receiver operating characteristic curve analysis of TTP, PI, EI, AS, DS and AUC in stages Ⅰ and ⅢA had a certain diagnostic efficacy, similar to the results in stages Ⅱ and ⅢA. The diagnostic performance of DS was less accurate in stages Ⅰ and ⅢA, while the diagnostic performance of TTP was less accurate in stages Ⅱ and ⅢA. ARCO stage was independently and negatively correlated with TTP and DS and independently and positively correlated with PI, EI, AS and AUC. The MTT assay was not correlated with ARCO stage. Logistic regression models containing statistically significant TTP, EI and AUC values were constructed, and all three values were closely related to the ARCO stage. In patients with different ARCO stages of ONFH, CEUS can effectively assess subchondral bone perfusion of the femoral head and is expected to become an effective imaging method for the diagnosis of early ONFH.

Quantitative Ultrasound Assessment of Early Osteoarthritis in Human Articular Cartilage Using a High-Frequency Linear Array Transducer

Quantitative ultrasound (QUS) assessment of osteoarthritis (OA) using high-frequency, research-grade single-element ultrasound systems has been reported. The objective of this ex vivo study was to assess the performance of QUS in detecting early OA using a high-frequency linear array transducer. Osteochondral plugs (n = 26) of human articular cartilage were scanned with ExactVu Micro-Ultrasound using an EV29L side-fire transducer. For comparison, the samples were also imaged with SAM200Ex, a custom 40-MHz scanning acoustic microscope with a single-element, focused transducer. Thirteen QUS parameters were derived from the ultrasound data. Magnetic resonance imaging (MRI) data, with T1 and T2 extracted as the quantitative parameters, were also acquired for comparison. Cartilage degeneration was graded from histology and correlated to all quantitative parameters. A maximum Spearman rank correlation coefficient (ρ) of 0.75 was achieved using a combination of ExactVu QUS parameters, while a maximum ρ of 0.62 was achieved using a combination of parameters from SAM200Ex. A maximum ρ of 0.75 was achieved using the T1 and T2 MRI parameters. This study illustrates the potential of a high-frequency linear array transducer to provide a convenient method for early OA screening with results comparable to those of research-grade single-element ultrasound and MRI.

The Oral Administration of Highly-Bioavailable Curcumin for One Year Has Clinical and Chondro-Protective Effects: A Randomized, Double-Blinded, Placebo-Controlled Prospective Study

Purpose

The purpose of this study was to determine the clinical and chondroprotective efficacy and safety of orally administered Theracurmin in patients who underwent mosaicplasty for knee chondral or osteochondral diseases over 12 months of treatment.

Methods

We enrolled 50 patients, older than 20 years of age, who underwent mosaicplasty for their knee joint diseases. Theracurmin at 180 mg of curcumin per day or placebo was administered orally every day for 12 months. Because 7 patients dropped out of the study, 43 patients were examined; they included 14 men and 29 women and 24 right and 19 left knees. The mean operative age was 59.5 years (range, 24-84 years). We evaluated the Japanese Orthopaedic Association knee osteoarthritis score (JOA), visual analog scale (VAS), and Japanese Knee Osteoarthritis Measure (JKOM) as clinical symptoms; T2 mapping values using magnetic resonance imaging as an indication of the chondroprotective effect; and blood concentration of curcumin at 0, 3, 6, and 12 months after the operations. We performed intraoperative acoustic evaluation of articular cartilage as a measure of chondroprotective effect during the operations and second-look arthroscopy.

Results

The JOA, VAS and JKOM at 3, 6, and 12 months were significantly better than those during the preoperative period. However, the values of JOA, VAS and JKOM and T2 mapping were not significantly different between the Theracurmin and placebo groups. The blood concentration of curcumin in the Theracurmin group was significantly higher than that in the placebo group at 3, 6, and 12 months after the operations. Cartilage stiffness and surface roughness were significantly better in the Theracurmin group than in the placebo group at second-look arthroscopy.

Conclusions

The oral administration of Theracurmin for 1 year demonstrated significantly better chondroprotective effects and no worse clinical effects and adverse events than the placebo.

Level of Evidence

Level I, double-blinded, placebo-controlled, prospective study.

High-Frequency Acoustic Imaging Using Adhesive-Free Polymer Transducer

The piezoelectric polymer PVDF and its copolymers have a long history as transducer materials for medical and biological applications. An efficient use of these polymers can potentially both lower the production cost and offer an environment-friendly alternative for medical transducers which today is dominated by piezoelectric ceramics containing lead. The main goal of the current work has been to compare the image quality of a low-cost in-house transducers made from the copolymer P(VDF-TrFE) to a commercial PVDF transducer. Several test objects were explored with the transducers used in a scanning acoustic microscope, including a human articular cartilage sample, a coin surface, and an etched metal film with fine line structures. To evaluate the image quality, C- and B-scan images were obtained from the recorded time series, and compared in terms of resolution, SNR, point-spread function, and depth imaging capability. The investigation is believed to provide useful information about both the strengths and limitations of low-cost polymer transducers.

3D High-Frequency Ultrasound Imaging of Cartilage-Bone Interface Compared with Micro-CT

Cartilage-bone interface (CBI) is a complex structure which bears important information in pathophysiology of osteoarthritis (OA). While high-frequency ultrasound (US) has been widely used for the investigation of articular cartilage, 3D imaging of CBI using US is less commonly reported in this field. Here, we adopted a 3D high-frequency ultrasound imaging approach specifically for the investigation of CBI in human knee samples. Fifteen osteochondral disks from the tibial plateau of seven OA patients were prepared in vitro and scanned using both high-frequency US and micro-CT imaging. The 3D morphology of the tidemark was reconstructed and compared using an image registration approach between the two imaging modalities. Results showed that the 3D tidemark could be well registered between the two imaging methods with a mean surface discrepancy of 33.2 ± 9.9 μm. Quantitative surface waviness/roughness parameter analysis showed significant correlations between the two imaging modalities. An intensity projected en face imaging was proposed to probe characteristic details of the CBI such as its perforations. This study provided evidence for the 3D high-frequency ultrasound as a nonionizing radiation imaging tool potentially useful to evaluate the change of CBI in basic research of join diseases including OA.

The role of subchondral bone, and its histomorphology, on the dynamic viscoelasticity of cartilage, bone and osteochondral cores

OBJECTIVE

Viscoelastic properties of articular cartilage have been characterised at physiological frequencies. However, studies investigating the interaction between cartilage and subchondral bone and the influence of underlying bone histomorphometry on the viscoelasticity of cartilage are lacking.

METHOD

Dynamic Mechanical Analysis (DMA) has been used to quantify the dynamic viscoelasticity of bovine tibial plateau osteochondral cores, over a frequency sweep from 1 to 88 Hz. Specimens (approximately aged between 18 and 30 months) were neither osteoarthritic nor otherwise compromised. A maximum nominal stress of 1.7 MPa was induced. Viscoelastic properties of cores have been compared with that of its components (cartilage and bone) in terms of the elastic and viscous components of both structural stiffness and material modulus. Micro-computed tomography scans were used to quantify the histomorphological properties of the subchondral bone.

RESULTS

Opposing frequency-dependent loss stiffness, and modulus, trends were witnessed for osteochondral tissues: for cartilage it increased logarithmically (P < 0.05); for bone it decreased logarithmically (P < 0.05). The storage stiffness of osteochondral cores was logarithmically frequency-dependent (P < 0.05), however, the loss stiffness was typically frequency-independent (P > 0.05). A linear relationship between the subchondral bone plate (SBP) thickness and cartilage thickness (P < 0.001) was identified. Cartilage loss modulus was linearly correlated to bone mineral density (BMD) (P < 0.05) and bone volume (P < 0.05).

CONCLUSION

The relationship between the subchondral bone histomorphometry and cartilage viscoelasticity (namely loss modulus) and thickness, have implications for the initiation and progression of osteoarthritis (OA) through an altered ability of cartilage to dissipate energy.

Ultrasonic cartilage thickness measurement is accurate, reproducible, and reliable-validation study using contrast-enhanced micro-CT

Background

Ultrasonography is a fast and patient-friendly modality to assess cartilage thickness. However, inconsistent results regarding accuracy have been reported. Therefore, we asked what are (1) the accuracy, (2) reproducibility, and (3) reliability of ultrasonographic cartilage thickness measurement using contrast-enhanced micro-CT for validation?

Methods

A series of 50 cartilage–bone plugs were harvested from fresh bovine and porcine joints. Ultrasonic cartilage thickness was determined using an A-mode, 20-MHz hand-held ultrasonic probe with native (1580 m/s) and adjusted speed of sound (1696 m/s). All measurements were performed by two observers at two different occasions. Angle of insonation was controlled by tilting the device and recording minimal thickness. Retrieval of exact location for measurement was facilitated by aligning the circular design of both cartilage–bone plug and ultrasonic device. There was no soft tissue interference between cartilage surface and ultrasonic probe. Ground truth measurement was performed using micro-CT with iodine contrast agent and a voxel size of 16 μm. The mean cartilage thickness was 1.383 ± 0.402 mm (range, 0.588–2.460 mm).

Results

Mean accuracy was 0.074 ± 0.061 mm (0.002–0.256 mm) for native and 0.093 ± 0.098 mm (0.000–0.401 mm) for adjusted speed of sound. Bland–Altman analysis showed no systematic error. High correlation was found for native and adjusted speed of sound with contrast-enhanced micro-CT (both r = 0.973; p < 0.001). A perfect agreement for reproducibility (intraclass correlation coefficient [ICC] 0.992 and 0.994) and reliability (ICC 0.993, 95% confidence interval 0.990–0.995) was found.

Conclusions

Ultrasonic cartilage thickness measurement could be shown to be highly accurate, reliable, and reproducible. The A-mode ultrasonic cartilage thickness measurement is a fast and patient-friendly modality which can detect early joint degeneration and facilitate decision making in joint preserving surgery.

Electronic supplementary material

The online version of this article (10.1186/s13018-019-1099-8) contains supplementary material, which is available to authorized users.

Ultrasound Parameters for Human Osteoarthritic Subchondral Bone ex Vivo: Comparison with Micro-Computed Tomography Parameters

The aim of this study was to identify ultrasound parameters reflecting subchondral porosity (P_o), subchondral plate thickness (T_pl) and bone volume fraction at the trabecular bone region (BV/TV_Tb). Sixteen osteoarthritic human lateral femoral condyles were evaluated ex vivo using a 15-MHz pulsed-echo ultrasound 3-D scanning system. The cartilage-subchondral bone (C-B) surface region (layer 1) and inner subchondral bone region (layer 2) were analyzed; we newly introduced entropy (ENT) and correlation (COR) of ultrasound texture parameters of the parallel (x) or perpendicular (z) direction to the C-B interface for this analysis. P_o, T_pl and BV/TV_Tb were evaluated as reference measurements using micro-computed tomography. ENT_L1x (ENT of layer 1, x-direction) and ENT_L1z were significantly correlated with P_o (both r values = 0.58), COR_L2x with T_pl (r = -0.73) and COR_L2z with BV/TV_Tb (r = -0.66). These are efficient indicators of the characteristics of osteoarthritis-related subchondral bone; the other texture parameters were not significant.

How precisely does ultrasonographic evaluation reflect the histological status of the articular cartilage of the knee joint?

The thickness and the grade of the articular cartilages of the knee of 34 patients who underwent total knee arthroplasty were evaluated by ultrasound (US) and by histology. The US grade correlated with the histological grade and the thickness of the articular cartilage measured by US. The thickness measured by US was significantly correlated with that measured by histology for the medial condyle. The US thickness was significantly less than the histological thickness for thicker articular cartilages. US grading and the thickness of the articular cartilages evaluated by US is sufficiently reliable to indicate their histological status.

Quantitative Evaluation of Enzyme-Induced Porcine Articular Cartilage Degeneration Based on Observation of Entire Cartilage Layer Using Ultrasound

Enzyme-induced articular cartilage degeneration resembling osteoarthritis was evaluated using a newly defined acoustic parameter, the "averaged magnitude ratio" (AMR), which has been suggested as an indicator of articular cartilage degeneration. In vitro experiments were conducted on porcine cartilage samples digested with trypsin for 2 h (n = 10) and 4 h (n = 13) and healthy control samples (n = 13). AMR was determined with 15- and 25-MHz ultrasound, and the integrated reflection coefficient (IRC) and apparent integrated backscattering coefficient (AIB) were also calculated for comparison. The Young's modulus of superficial cartilage was measured using atomic force microscopy. Performance of the AMR differs between 15 and 25 MHz, possibly because of frequency-related attenuation and resolution of ultrasound. At the proper settings, AMR exhibited a competence similar to that of IRC and AIB in detecting cartilage degeneration and could also detect differences in deeper positions. Furthermore, AMR has the advantages of being easy to measure and requiring no reference material.

High-Frequency Ultrasound Imaging of Tidemark In Vitro in Advanced Knee Osteoarthritis

High-frequency ultrasound imaging has been widely adopted for assessment of the degenerative changes of articular cartilage in osteoarthritis (OA). Yet, there are few reports on investigating its capability to evaluate subchondral bone. Here, we employed high-frequency ultrasound imaging (25 MHz) to examine in vitro the tidemark in cylindrical osteochondral disks (n = 33) harvested from advanced OA knees of humans. We found good correspondence in morphology observed by ultrasound imaging and micro-computed tomography. Ultrasound roughness index (URI) of tidemark was derived from the raw radiofrequency signals to compare with bone quality factors, including bone volume fraction (BV/TV) and bone mineral density (BMD) measured by micro-computed tomography, using the Spearman correlation (ρ). URI of the tidemark was negatively associated with the subchondral plate BV/TV (ρ = -0.73, p <0.001), BMD (ρ = -0.40, p = 0.020), as well as the underneath trabecular bone BV/TV (ρ = -0.39, p = 0.025) and BMD (ρ = -0.43, p = 0.012). In conclusion, this preliminary study demonstrated that morphology measured by high-frequency ultrasound imaging could reflect the quality of the subchondral bone. High-frequency ultrasound is a promising imaging tool to evaluate the changes of the subchondral bone in addition to those of the overlying cartilage in OA.

Regular chondrocyte spacing is a potential cause for coherent ultrasound backscatter in human articular cartilage

The potential of quantitative ultrasound (QUS) to assess the regular cellular spacing in the superficial cartilage zones was investigated experimentally and numerically. Nine osteochondral samples, extracted from two human cadaver knee joints, were measured using a 50-MHz ultrasound scanning device and evaluated using Mankin score. Simulated backscattered power spectra from models with an idealized cell alignment exhibited a pronounced frequency peak. From the peak, cell spacing in the range between 15 and 40 μm between cell layers was detected with an average error of 0.2 μm. The mean QUS-based cell spacing was 28.3 ± 5.3 μm. Strong correlation (R²= 0.59, p ≤ 0.001) between spacing estimates from light microscopy (LM) and QUS was found for samples with Mankin score ≤3. For higher scores, QUS-based spacing was significantly higher (p ≤ 0.05) compared to LM-based spacing. QUS-based spacing estimates together with other QUS parameters may serve as future biomarkers for detecting early signs of osteoarthrosis.

Nondestructive evaluation of a new hydrolytically degradable and photo-clickable PEG hydrogel for cartilage tissue engineering

Photopolymerizable and hydrolytically labile poly(ethylene glycol) (PEG) hydrogels formed from photo-clickable reactions were investigated as cell delivery platforms for cartilage tissue engineering (TE). PEG hydrogels were formed from thiol-norbornene PEG macromers whereby the crosslinks contained caprolactone segments with hydrolytically labile ester linkages. Juvenile bovine chondrocytes encapsulated in the hydrogels were cultured for up to four weeks and assessed biochemically and histologically, using standard destructive assays, and for mechanical and ultrasound properties, as nondestructive assays. Bulk degradation of acellular hydrogels was confirmed by a decrease in compressive modulus and an increase in mass swelling ratio over time. Chondrocytes deposited increasing amounts of sulfated glycosaminoglycans and collagens in the hydrogels with time. Spatially, collagen type II and aggrecan were present in the neotissue with formation of a territorial matrix beginning at day 21. Nondestructive measurements revealed an 8-fold increase in compressive modulus from days 7 to 28, which correlated with total collagen content. Ultrasound measurements revealed changes in the constructs over time, which differed from the mechanical properties, and appeared to correlate with ECM structure and organization shown by immunohistochemical analysis. Overall, non-destructive and destructive measurements show that this new hydrolytically degradable PEG hydrogel is promising for cartilage TE.

STATEMENT OF SIGNIFICANCE

Designing synthetic hydrogels whose degradation matches tissue growth is critical to maintaining mechanical integrity as the hydrogel degrades and new tissue forms, but is challenging due to the nature of the hydrogel crosslinks that inhibit diffusion of tissue matrix molecules. This study details a promising, new, photo-clickable and synthetic hydrogel whose degradation supports cartilaginous tissue matrix growth leading to the formation of a territorial matrix, concomitant with an increase in mechanical properties. Nondestructive assays based on mechanical and ultrasonic properties were also investigated using a novel instrument and found to correlate with matrix deposition and evolution. In sum, this study presents a new hydrogel platform combined with nondestructive assessments, which together have potential for in vitro cartilage tissue engineering.

Nondestructive Techniques to Evaluate the Characteristics and Development of Engineered Cartilage

In this review, methods for evaluating the properties of tissue engineered (TE) cartilage are described. Many of these have been developed for evaluating properties of native and osteoarthritic articular cartilage. However, with the increasing interest in engineering cartilage, specialized methods are needed for nondestructive evaluation of tissue while it is developing and after it is implanted. Such methods are needed, in part, due to the large inter- and intra-donor variability in the performance of the cellular component of the tissue, which remains a barrier to delivering reliable TE cartilage for implantation. Using conventional destructive tests, such variability makes it near-impossible to predict the timing and outcome of the tissue engineering process at the level of a specific piece of engineered tissue and also makes it difficult to assess the impact of changing tissue engineering regimens. While it is clear that the true test of engineered cartilage is its performance after it is implanted, correlation of pre and post implantation properties determined non-destructively in vitro and/or in vivo with performance should lead to predictive methods to improve quality-control and to minimize the chances of implanting inferior tissue.

Simultaneous evaluation of articular cartilage and subchondral bone from immobilized knee in rats by photoacoustic imaging system

BACKGROUND

Osteoarthritis is not only a disease of articular cartilage, but also of subchondral bone. It is difficult for ultrasound to evaluate subchondral bone because of permeability. This study aimed to evaluate sequential osteoarthritic changes of articular cartilage and subchondral bone from immobilized knees in rats with a photoacoustic (PA) imaging system.

METHODS

The unilateral knee joints of adult male rats were immobilized with an internal fixator (IM group) for 4 and 8 weeks. Sham operated animals had holes drilled in the femur and tibia and screws inserted without a plate (control group). A whole proximal third of the tibia was obtained. The specimens were immersed in normal saline and scanned by the PA imaging system, which can create both ultrasound (US) and PA imaging. After the scanning, specimens were fixed with paraformaldehyde, decalcified and embedded in paraffin. Thinly sliced tissues were prepared for histological evaluation. PA signals from the articular cartilage and subchondral bone were independently evaluated.

RESULTS

Gross observations showed that fibrillation occurred in the superficial layers and permeability of the articular cartilage increased. Histological observations showed that the articular cartilage became thicker and the bone marrow space expanded during immobilization. US images by the PA imaging system could evaluate the articular cartilage. PA signals from the articular cartilage and subchondral bone increased with the duration of immobilization and the difference, compared to the control group, was significant.

CONCLUSIONS

The PA imaging system could evaluate articular cartilage and subchondral bone simultaneously.

A new method for evaluating the degeneration of articular cartilage using pulse-echo ultrasound

This paper presents a novel nondestructive ultrasonic technique for measuring the sound speed and acoustic impedance of articular cartilage using the pulsed Vz,t technique. Vz,t data include a series of pulsed ultrasonic echoes collected using different distances between the ultrasonic transducer and the specimen. The 2D Fourier transform is applied to the Vz,t data to reconstruct the 2D reflection spectrum Rθ,ω. To obtain the reflection coefficient of articular cartilage, the Vz,t data from a reference specimen with a well-known reflection coefficient are obtained to eliminate the dependence on the general system transfer function. The ultrasound-derived aggregate modulus (Ha) is computed based on the measured reflection coefficient and the sound speed. In the experiment, 32 cartilage-bone samples were prepared from bovine articular cartilage, and 16 samples were digested using 0.25% trypsin solution. The sound speed and Ha of these cartilage samples were evaluated before and after degeneration. The magnitude of the sound speed decreased with trypsin digestion (from 1663 ± 5.6 m/s to 1613 ± 5.3 m/s). Moreover, the Young's modulus in the corresponding degenerative state was measured and was correlated with the ultrasound-derived aggregate modulus. The ultrasound-derived aggregate modulus was determined to be highly correlated with the Young's modulus (n = 16, r>0.895, p<0.003, Pearson correlation test for each measurement). The results demonstrate the effectiveness of using the proposed method to assess the changes in sound speed and the ultrasound-derived aggregate modulus of cartilage after degeneration.

Direct measurement of speed of sound in cartilage in situ using ultrasound and magnetic resonance images

This study verified the accuracy of the speed of sound (SOS) measured by the combination method, which calculates the ratio between the thickness values of cartilage measured by using the magnetic resonance imaging (MRI) and the ultrasonic pulse-echo imaging, and investigated in vivo application of this method. SOS specific to an ultrasound imaging device was used as a reference value to calculate the actual SOS from the ratio of cartilage thicknesses obtained from MR and ultrasound images. The accuracy of the thickness measurement was verified by comparing results obtained using MRI and a non-contact laser, and the accuracy of the calculated SOS was confirmed by comparing results of the pulse-echo and transmission methods in vitro. The difference between laser and MRI measurements was 0.05 ± 0.22 mm. SOS values in a human knee measured by the combination method in the medial and lateral femoral condyles were 1650 ± 79 and 1642 ± 78 m/s, respectively (p < 0.05). The results revealed the feasibility of in situ SOS measurement using the combination method.

In vivo quantitative ultrasound image analysis of femoral subchondral bone in knee osteoarthritis

A potential of quantitative noninvasive knee ultrasonography (US) for detecting changes in femoral subchondral bone related to knee osteoarthritis (OA) was investigated. Thirty-nine patients referred to a knee arthroscopy underwent dynamic noninvasive US examination of the knee joint. The subchondral bone was semiautomatically segmented from representative US images of femoral medial and lateral condyles and intercondylar notch area. Subsequently, the normalized mean gray-level intensity profile, starting from the cartilage-bone interface and extending to the subchondral bone depth of -1.7 mm, was calculated. The obtained profile was divided into 5 depth levels and the mean of each level, as well as the slope of the profile within the first two levels, was calculated. The US quantitative data were compared with the arthroscopic Noyes' grading and radiographic Kellgren-Lawrence (K-L) grading. Qualitatively, an increase in relative subchondral bone US gray-level values was observed as OA progressed. Statistically significant correlations were observed between normalized US mean intensity or intensity slope especially in subchondral bone depth level 2 and K-L grading (r = 0.600, P < 0.001; r = 0.486, P = 0.006, resp.) or femoral arthroscopic scoring (r = 0.332, P = 0.039; r = 0.335, P = 0.037, resp.). This novel quantitative noninvasive US analysis technique is promising for detection of femoral subchondral bone changes in knee OA.

Tougu Xiaotong capsule inhibits the tidemark replication and cartilage degradation of papain-induced osteoarthritis by the regulation of chondrocyte autophagy

The tidemark is located between calcified and non-calcified cartilage matrices. Tidemark replication plays an important role in the pathogenesis of osteoarthrosis (OA). Autophagy, or cellular self-digestion, is an essential cellular homeostasis mechanism that was found to be deficient in osteoarthritic cartilage. This study evaluated the effects of Tougu Xiaotong capsule (TXC) on the tidemark replication and cartilage degradation, and also investigated LC3 I/II, which executes autophagy, the potential role of ULK1, an inducer of autophagy, and Beclin1, a regulator of autophagy, in the development of a papain-induced OA in rat knee joints. Using a papain-injected knee rat model, standard histological methods were used to validate our model as well as treatment with TXC or glucosamine (GlcN). After 12 weeks of treatment, the changes of cartilage structure were observed by digital radiography (DR), optical microscopy, scanning electron microscopy and transmission electron microscopy, and the LC3 I/II, ULK1 and Beclin1 levels were measured by western blotting. Cartilage degradation was evaluated by the Mankin score on paraffin-embedded sections stained with Safranin O-fast green. TXC was found to improve the arrangement of subchondral bone collagen fibers and calcium phosphate crystals, inhibit the tidemark replication and delay the cartilage degradation in the papain-induced OA. Our results also showed that LC3 I/II, ULK1 and Beclin1 levels in both the TXC+OA and GlcN+OA groups were significantly increased compared to those in the OA group. The results indicate that TXC could inhibit the tidemark replication and cartilage degradation by the regulation of chondrocyte autophagy.

Comparison of articular cartilage images assessed by high-frequency ultrasound microscope and scanning acoustic microscope

PURPOSE

The purpose of this study was to compare images of a newly developed high-frequency ultrasound imaging system (HFUIS) and scanning acoustic microscope (SAM) and to calculate their Pearson product moment correlations with a view to applying HFUIS for clinical use.

METHODS

Cylindrical cartilage-bone complexes from adult male Sprague-Dawley rats were obtained. The specimens were immersed in normal saline and scanned by HFUIS. Intensity by HFUIS was normalised by reflection from a steel plate at the same distance. After the scanning, specimens were fixed with paraformaldehyde, decalcified and embedded in paraffin. Thinly sliced tissues were prepared for SAM evaluation. After the scanning, three layers of articular cartilage (superficial, middle and deep) were independently evaluated and their relationships calculated.

RESULTS

The superficial and deep layers indicated high relative intensity, whereas the middle layer showed nonhomogeneous relative intensity by HFUIS. A high relative intensity by HFUIS and high sound speed area by SAM had strong correlations (Pearson product moment correlation, superficial layer 0.704, middle layer 0.731).

CONCLUSIONS

HFUIS produced high-resolution images of the articular cartilage and its intensity was strongly correlated with sound speed by SAM.