3D morphometric analysis of calcified cartilage properties using micro-computed tomography

OBJECTIVE: Our aim is to establish methods for quantifying morphometric properties of calcified cartilage (CC) from micro-computed tomography (muCT). Furthermore, we evaluated the feasibility of these methods in investigating relationships between osteoarthritis (OA), tidemark surface morphology and open subchondral channels (OSCCs). METHOD: Samples (n = 15) used in this study were harvested from human lateral tibial plateau (n = 8). Conventional roughness and parameters assessing local 3-dimensional (3D) surface variations were used to quantify the surface morphology of the CC. Subchondral channel properties (percentage, density, size) were also calculated. As a reference, histological sections were evaluated using Histopathological osteoarthritis grading (OARSI) and thickness of CC and subchondral bone (SCB) was quantified. RESULTS: OARSI grade correlated with a decrease in local 3D variations of the tidemark surface (amount of different surface patterns (rs = -0.600, P = 0.018), entropy of patterns (EP) (rs = -0.648, P = 0.018), homogeneity index (HI) (rs = 0.555, P = 0.032)) and tidemark roughness (TMR) (rs = -0.579, P = 0.024). Amount of different patterns (ADP) and EP associated with channel area fraction (CAF) (rp = 0.876, P < 0.0001; rp = 0.665, P = 0.007, respectively) and channel density (CD) (rp = 0.680, P = 0.011; rp = 0.582, P = 0.023, respectively). TMR was associated with CAF (rp = 0.926, P < 0.0001) and average channel size (rp = 0.574, P = 0.025). CC topography differed statistically significantly in early OA vs healthy samples. CONCLUSION: We introduced a mu-CT image method to quantify 3D CC topography and perforations through CC. CC topography was associated with OARSI grade and OSCC properties; this suggests that the established methods can detect topographical changes in tidemark and CC perforations associated with OA

Modelling the translational dynamics of the Atlas motion platform

The novel Atlas motion platform is designed to prescribe in six degrees of freedom the motion of a spherical simulator cockpit with the unusual capability of providing kinematically-uncoupled translational and rotational motion, unbounded rotational motion, and a fully-dexterous workspace. In support of the design and operation of the Atlas simulator, a translational dynamic model of the system has been developed. It includes the prescribed motion of the interface between the translational and rotational stages, translational motion of the spherical cockpit, and translational motion of the upper 'halo' support structure. Contact points between the spherical cockpit and the constraint/actuation system were modelled using directed elements consisting of either constant-force elements or spring/damper elements. In the case of the spring/damper elements, stiffness and damping parameters were obtained by a combination of finite element analysis of structural elements and experimental characterization of viscoelastic elements along the interfacing load paths. The dynamic model is suitable for evaluating internal forces and relative motions within the simulator resulting from translation motions; and forms the basis for extension to include rotational dynamics of the simulator system

A novel method for automatic localization of joint area on knee plain radiographs

Abstract Osteoarthritis (OA) is a common musculoskeletal condition typically diagnosed from radiographic assessment after clinical examination. However, a visual evaluation made by a practitioner suffers from subjectivity and is highly dependent on the experience. Computer-aided diagnostics (CAD) could improve the objectivity of knee radiographic examination. The first essential step of knee OA CAD is to automatically localize the joint area. However, according to the literature this task itself remains challenging. The aim of this study was to develop novel and computationally efficient method to tackle the issue. Here, three different datasets of knee radiographs were used (n = 473/93/77) to validate the overall performance of the method. Our pipeline consists of two parts: anatomically-based joint area proposal and their evaluation using Histogram of Oriented Gradients and the pre-trained Support Vector Machine classifier scores. The obtained results for the used datasets show the mean intersection over the union equals to: 0.84, 0.79 and 0.78. Using a high-end computer, the method allows to automatically annotate conventional knee radiographs within 14–16 ms and high resolution ones within 170 ms. Our results demonstrate that the developed method is suitable for large-scale analyses

A street deposit sampling method for metal and hydrocarbon contamination assessment

International audienceUrban surface contamination, by atmospheric deposits as well as human activities, is a major concern for urban pollution management. Besides coarse street deposits which are clearly perceived and easily removed, suspended solid (SS) surface loads and contamination by heavy metals and hydrocarbons are rarely assessed although theycould be of major importance with regards to combined or separate server overflow (CSO and SSO) impacts. Both dry and wet vacuum sampling procedures have been first compared, in the laboratory, using dry and sieved clay or street deposits. Then the wet vacuum sampling procedure has been refined, coupling the injection of water and the hand-brushing of the surface prior to its vacuum cleaning, and evaluated on a car parking area close to the University. Finally this procedure has been assessed in Bearn Street within the 'Le Marais' district in Paris centre, and 34 samples have been analysed for metal and eight for aromatic hydrocarbon contamination. Heavy metal concentrations (0.1-1.7 g.kg-1 dry wt. Cu, 0.9-6.1 g.kg-1 dry wt. Pb and 1.5-4.6 g.kg-1 dry wt. Zn) within street deposit samples collected in Paris centre, indicate a high contamination, especially for copper and zinc, as compared to reported data. Total polyaromatic hydrocarbons (PAHs) are in the 3-11 mg.kg-1 dry wt. range, thus approxiamtely 10 times less contaminated than dry atmospheric deposits. This paper presents data obtained ans discusses the difficulties encountered when sampling street deposits in busy areas of a city like Paris. The water jet street cleaning procedure used in Paris city workers was tested for its efficiency., by comparison of surface loads before and after the cleaning procedure. Although solids cleaning efficiency is highly variable (20-65%) and somewhat higher for particles larger than 100 µm, particulate metal cleaning efficiency is even more variable (0-75%) and particulate PAHs appear not to be significantly revoved

Subchondral bone histology and grading in osteoarthritis

Abstract Objective: Osteoarthritis (OA) has often regarded as a disease of articular cartilage only. New evidence has shifted the paradigm towards a system biology approach, where also the surrounding tissue, especially bone is studied more vigorously. However, the histological features of subchondral bone are only poorly characterized in current histological grading scales of OA. The aim of this study is to specifically characterize histological changes occurring in subchondral bone at different stages of OA and propose a simple grading system for them. Design: 20 patients undergoing total knee replacement surgery were randomly selected for the study and series of osteochondral samples were harvested from the tibial plateaus for histological analysis. Cartilage degeneration was assessed using the standardized OARSI grading system, while a novel four-stage grading system was developed to illustrate the changes in subchondral bone. Subchondral bone histology was further quantitatively analyzed by measuring the thickness of uncalcified and calcified cartilage as well as subchondral bone plate. Furthermore, internal structure of calcified cartilage-bone interface was characterized utilizing local binary patterns (LBP) based method. Results: The histological appearance of subchondral bone changed drastically in correlation with the OARSI grading of cartilage degeneration. As the cartilage layer thickness decreases the subchondral plate thickness and disorientation, as measured with LBP, increases. Calcified cartilage thickness was highest in samples with moderate OA. Conclusion: The proposed grading system for subchondral bone has significant relationship with the corresponding OARSI grading for cartilage. Our results suggest that subchondral bone remodeling is a fundamental factor already in early stages of cartilage degeneration

Acoustic emissions and kinematic instability of the osteoarthritic knee joint

To evaluate the acoustic emissions (AE) and kinematic instability (KI) of the osteoarthritic (OA) knee joints, and to compare these signals to radiographic findings. Sixty-six female and 43 male participants aged 44–67 were recruited. On radiography, joint-space narrowing, osteophytes and Kellgren–Lawrence (KL) grade were evaluated. Based on radiography

Patient characteristics.

<p>Patient characteristics.</p

Masson’s trichrome (A, C-F) and HE stained (B) histological images of the features of subchondral bone.

<p>(A) Subchondral bone fenestra marked with an asterisk. (B) Subchondral trabeculae showing some intra-trabecular cartilage (triangles), polarized light microscopy. (C-D) Some of the more degenerated samples were seen with cartilage (triangle) among trabecular bone. (E-F) Late-stage degeneration samples revealing degenerated and apoptotic cartilage. Scale bar 200 μm.</p

Mean OARSI scores of subchondral bone grades and histological image analysis data in correlation to samples bone OA grade.

<p>(A) OARSI score increases by subchondral oa grade. Samples with subchondral grade 0 reached mean OARSI score of 1.46. Subchondral OA grades 1, 2 and 3 had mean OARSI scores of 3.45, 3.99 and 5.19 respectively. Each bar and point represents the mean ± S.E. (B) Mean cartilage thickness. (C) Mean subchondral bone plate thickness. (D) Mean calcified cartilage thickness. Each bar and point represents the mean ± S.E. * p<0.05, *** p<0.001</p

LBP based homogeneity and entropy of subchondral bone in correlation to bone and cartilage OA grade.

<p>(A) Homogeneity and (B) entropy in samples with subchondral bone grade 0-2. Grade 3 samples had smooth and worn surface and were excluded. (N = 2, 9 and 7 for grades 0, 1 and 2 respectively). Linear regression models between (C) homogeneity, (D) entropy and cartilage OARSI grade, r²(C) = 0.583, r(D) = 0.612. * p<0.05, *** p<0.001.</p