A combined experimental atomic force microscopy-based nanoindentation and computational modeling approach to unravel the key contributors to the time-dependent mechanical behavior of single cells.

Cellular responses to mechanical stimuli are influenced by the mechanical properties of cells and the surrounding tissue matrix. Cells exhibit viscoelastic behavior in response to an applied stress. This has been attributed to fluid flow-dependent and flow-independent mechanisms.

Ability of ultrasound imaging to detect erosions in a bone phantom model.

Objectives: The authors examined the validity, interobserver reliability and interscanner variation in detecting bone erosions with ultrasonography using a custom-made phantom.

Methods: 21 bovine bones were used. Artificial erosions were made into 15 bones and six bones were left as controls.

Estimation of mechanical properties of articular cartilage with MRI - dGEMRIC, T2 and T1 imaging in different species with variable stages of maturation.

Background: Magnetic resonance imaging (MRI) is one of the most potential methods for non-invasive diagnosis of cartilage disorders. Several methods have been established for clinical use; T(1) relaxation time imaging with negatively charged contrast agent (delayed gadolinium enhanced MRI of cartilage, dGEMRIC) has been shown to be sensitive to proteoglycan (PG) content while T(2) relaxation time has been demonstrated to express properties of the collagen fibril network. The use of native T(1) relaxation time has received less attention.

Comparison of novel clinically applicable methodology for sensitive diagnostics of cartilage degeneration.

In order efficiently to target therapies intending to stop or reverse degenerative processes of articular cartilage, it would be crucial to diagnose osteoarthritis (OA) earlier and more sensitively than is possible with the existing clinical methods. Unfortunately, current clinical methods for OA diagnostics are insensitive for detecting the early degenerative changes, e.g.

Quantitative ultrasound imaging detects degenerative changes in articular cartilage surface and subchondral bone.

Previous studies have suggested that quantitative ultrasound imaging could sensitively diagnose degeneration of the articular surface and changes in the subchondral bone during the development of osteoarthrosis (OA). We have recently introduced a new parameter, ultrasound roughness index (URI), for the quantification of cartilage surface roughness, and successfully tested it with normal and experimentally degraded articular surfaces. In this in vitro study, the applicability of URI was tested in bovine cartilage samples with spontaneously developed tissue degeneration.

Acoustic properties of articular cartilage under mechanical stress.

Mechano-acoustic and elastographic techniques may provide quantitative means for the in vivo diagnostics of articular cartilage. These techniques assume that sound speed does not change during tissue loading. As articular cartilage shows volumetric changes during compression, acoustic properties of cartilage may change affecting the validity of mechano-acoustic measurements.

T(2) relaxation time mapping reveals age- and species-related diversity of collagen network architecture in articular cartilage.

Objective: The magnetic resonance imaging (MRI) parameter T(2) relaxation time has been shown to be sensitive to the collagen network architecture of articular cartilage. The aim of the study was to investigate the agreement of T(2) relaxation time mapping and polarized light microscopy (PLM) for the determination of histological properties (i.e.

Cellulose sponge as a scaffold for cartilage tissue engineering.

One goal of functional tissue engineering is to manufacture scaffolds infiltrated with chondrocytes which are suitable for transplantation into the lesion areas of articular cartilage. Various research strategies are used to fabricate cartilage transplants which would have the correct phenotype, contain enough extracellular matrix components, and have structural and biomechanical properties equivalent to normal articular cartilage. We have investigated the suitability of viscose cellulose sponges as a scaffold for cartilage tissue engineering.

In situ and ex vivo evaluation of an arthroscopic indentation instrument to estimate the health status of articular cartilage in the equine metacarpophalangeal joint.

Objective: To evaluate an arthroscopic indentation instrument (Artscan 200) for assessment of the health status of equine articular cartilage.

Study Design: In vitro experiment using equine isolated proximal phalanx (P1) specimens.

Sample Population: P1 specimens from 39 horses (aged 1.

T2 relaxation time and delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) of human patellar cartilage at 1.5 T and 9.4 T: Relationships with tissue mechanical properties.

Quantitative magnetic resonance imaging (MRI) techniques have been developed for noninvasive assessment of the structure of articular cartilage. T2 relaxation time is sensitive to the integrity and orientation of the collagen network, while T1 relaxation time in presence of Gd-DTPA2- (dGEMRIC) reflects the proteoglycan content of cartilage. In the present study, human patellar cartilage samples were investigated in vitro to determine the ability of MRI parameters to reveal topographical variations and to predict mechanical properties of cartilage at two different field strengths.

Quantitative ultrasound imaging of spontaneous repair of porcine cartilage.

Objective: Arthroscopy offers qualitative means to evaluate the surface of articular cartilage. However, possible degeneration of the deep cartilage and subchondral bone remains undetected. High frequency ultrasound imaging is an advanced cartilage evaluation method which is conceivable to arthroscopic use and brings diagnostic information also from deeper cartilage and subchondral bone.

Site-specific ultrasound reflection properties and superficial collagen content of bovine knee articular cartilage.

Previous quantitative 2D-ultrasound imaging studies have demonstrated that the ultrasound reflection measurement of articular cartilage surface sensitively detects degradation of the collagen network, whereas digestion of cartilage proteoglycans has no significant effect on the ultrasound reflection. In this study, the first aim was to characterize the ability of quantitative 2D-ultrasound imaging to detect site-specific differences in ultrasound reflection and backscattering properties of cartilage surface and cartilage-bone interface at visually healthy bovine knee (n = 30). As a second aim, we studied factors controlling ultrasound reflection properties of an intact cartilage surface.

Functional consequences of cartilage degeneration in the equine metacarpophalangeal joint: quantitative assessment of cartilage stiffness.

Reasons For Performing Study: No quantitative data currently exist on the relationship of the occurrence of cartilage degeneration and changes in site-specific biomechanical properties in the metacarpophalangeal (MCP) joint in the horse.

Objectives: To gain insight into the biomechanical consequences of cartilage deterioration at 2 differently loaded sites on the proximal articular surface of the proximal phalanx (P1).

Hypothesis: Static and dynamic stiffness of articular cartilage decreases significantly in degenerated cartilage.

Influence of age, site, and degenerative state on the speed of sound in equine articular cartilage.

Objective: To determine the speed of sound (SOS) in equine articular cartilage and investigate the influence of age, site in the joint, and cartilage degeneration on the SOS.

Sample Population: Cartilage samples from 38 metacarpophalangeal joints of 38 horses (age range, 5 months to 22 years).

Procedure: Osteochondral plugs were collected from 2 articular sites of the proximal phalanx after the degenerative state was characterized by use of the cartilage degeneration index (CDI) technique.

Localization of sentinel nodes in breast cancer: novel method and device to help pen marking of active nodes during gamma camera imaging.

Gamma camera imaging with Tc-99m marking is a widely used method to locate sentinel lymph nodes (SNs) in breast cancer patients. Prior to SN biopsy, the anterior and lateral location of the SN is marked on the patient's skin using an ink pen. The pen marks guide the surgeon during an operation.

Functional adaptation of articular cartilage from birth to maturity under the influence of loading: a biomechanical analysis.

Reasons For Performing Study: The concept of functional adapatation of articular cartilage during maturation has emerged from earlier biochemical research. However, articular cartilage has principally a biomechanical function governed by joint loading.

Objectives: To verify whether the concept of functional adaptation can be confirmed by direct measurement of biomechanical properties of cartilage.

Undersulfated chondroitin sulfate does not increase in osteoarthritic cartilage.

Objective: To test whether there is undersulfation of chondroitin sulfate in osteoarthritic bovine articular cartilage to support the hypothesis that sulfate deficiency is involved with the development of osteoarthritis.

Methods: Cartilage samples from bovine patellae (n = 32) were divided into 3 groups based on their osteoarthritic progression, as assessed by modified Mankin score. Uronic acid contents of the samples were determined.

Mechano-acoustic determination of Young's modulus of articular cartilage.

The compressive stiffness of an elastic material is traditionally characterized by its Young's modulus. Young's modulus of articular cartilage can be directly measured using unconfined compression geometry by assuming the cartilage to be homogeneous and isotropic. In isotropic materials, Young's modulus can also be determined acoustically by the measurement of sound speed and density of the material.

Ultrasonic quantitation of superficial degradation of articular cartilage.

Ultrasound (US) has been suggested as a means for the quantitative detection of early osteoarthrotic changes in articular cartilage. In this study, the ability of quantitative US 2-D imaging (20 MHz) to reveal superficial changes in bovine articular cartilage after mechanical or enzymatic degradation was investigated in vitro. Mechanical degradation was induced by grinding samples against an emery paper with the grain size of 250 microm, 106 microm, 45 microm or 23 microm.

Ultrasound attenuation in normal and spontaneously degenerated articular cartilage.

High-frequency ultrasound (US) measurements may provide means for the quantification of articular cartilage quality. Bovine patellar cartilage samples (n = 32) at various degenerative stages were studied using US attenuation measurements in the 5- to 9-MHz frequency range. The results were compared with the histologic, biochemical and mechanical parameters obtained for the same samples, to identify which structural or functional factors could be related to the attenuation and its variations.

Proteoglycan and collagen sensitive MRI evaluation of normal and degenerated articular cartilage.

Quantitative magnetic resonance imaging (MRI) techniques have earlier been developed to characterize the structure and composition of articular cartilage. Particularly, Gd-DTPA(2-)-enhanced T1 imaging is sensitive to cartilage proteoglycan content, while T2 relaxation time mapping is indicative of the integrity and arrangement of the collagen network. However, the ability of these techniques to detect early osteoarthrotic changes in cartilage has not been demonstrated.

Prediction of biomechanical properties of articular cartilage with quantitative magnetic resonance imaging.

Quantitative magnetic resonance imaging (MRI) is the most potential non-invasive means for revealing the structure, composition and pathology of articular cartilage. Here we hypothesize that cartilage mechanical properties as determined by the macromolecular framework and their interactions can be accessed by quantitative MRI. To test this, adjacent cartilage disk pairs (n=32) were prepared from bovine proximal humerus and patellofemoral surfaces.

Ultrasound indentation of normal and spontaneously degenerated bovine articular cartilage.

Objective: We have previously developed a handheld ultrasound indentation instrument for the diagnosis of cartilage degeneration. The instrument has been demonstrated to be capable of quantifying mechanical and acoustic properties of enzymatically degraded and normal bovine articular cartilage in vitro and in situ. The aim of this study was to investigate the sensitivity of the instrument to distinguish between normal and spontaneously degenerated (e.

Fibril reinforced poroelastic model predicts specifically mechanical behavior of normal, proteoglycan depleted and collagen degraded articular cartilage.

Degradation of collagen network and proteoglycan (PG) macromolecules are signs of articular cartilage degeneration. These changes impair cartilage mechanical function. Effects of collagen degradation and PG depletion on the time-dependent mechanical behavior of cartilage are different.

Ultrasound indentation of bovine knee articular cartilage in situ.

We have earlier developed a handheld ultrasound indentation instrument for the diagnosis of articular cartilage degeneration. In ultrasound indentation, cartilage is compressed with the ultrasound transducer. Tissue thickness and deformation are calculated from the A-mode ultrasound signal and the stress applied is registered with the strain gauges.