Showing papers by "Jukka S. Jurvelin published in 2015"

Implementation of a gait cycle loading into healthy and meniscectomised knee joint models with fibril-reinforced articular cartilage

Abstract: Computational models can be used to evaluate the functional properties of knee joints and possible risk locations within joints. Current models with fibril-reinforced cartilage layers do not provide information about realistic human movement during walking. This study aimed to evaluate stresses and strains within a knee joint by implementing load data from a gait cycle in healthy and meniscectomised knee joint models with fibril-reinforced cartilages. A 3D finite element model of a knee joint with cartilages and menisci was created from magnetic resonance images. The gait cycle data from varying joint rotations, translations and axial forces were taken from experimental studies and implemented into the model. Cartilage layers were modelled as a fibril-reinforced poroviscoelastic material with the menisci considered as a transversely isotropic elastic material. In the normal knee joint model, relatively high maximum principal stresses were specifically predicted to occur in the medial condyle of the knee joint during the loading response. Bilateral meniscectomy increased stresses, strains and fluid pressures in cartilage on the lateral side, especially during the first 50% of the stance phase of the gait cycle. During the entire stance phase, the superficial collagen fibrils modulated stresses of cartilage, especially in the medial tibial cartilage. The present computational model with a gait cycle and fibril-reinforced biphasic cartilage revealed time- and location-dependent differences in stresses, strains and fluid pressures occurring in cartilage during walking. The lateral meniscus was observed to have a more significant role in distributing loads across the knee joint than the medial meniscus, suggesting that meniscectomy might initiate a post-traumatic process leading to osteoarthritis at the lateral compartment of the knee joint.

Pre-Osteoarthritis: Definition and Diagnosis of an Elusive Clinical Entity

Abstract: ObjectiveAn attempt to define pre-osteoarthritis (OA) versus early OA and definitive osteoarthritis.MethodsA group of specialists in the field of cartilage science and treatment was formed to consider the nature of OA onset and its possible diagnosis.ResultsLate-stage OA, necessitating total joint replacement, is the end stage of a biological process, with many previous earlier stages. Early-stage OA has been defined and involves structural changes identified by arthroscopy or radiography. The group argued that before the “early-stage OA” there must exist a stage where cellular processes, due to the presence of risk factors, have kicked into action but have not yet resulted in structural changes. The group suggested that this stage could be called “pre-osteoarthritis” (pre-OA).ConclusionsThe group suggests that defining points of initiation for OA in the knee could be defined, for example, by traumatic episodes or surgical meniscectomy. Such events may set in motion metabolic processes that could be diagn...

Optical absorption spectra of human articular cartilage correlate with biomechanical properties, histological score and biochemical composition

Abstract: This study investigates the relationship between the optical response of human articular cartilage in the visible (VIS) and near infrared (NIR) spectral range and its matrix properties.Full-thickness osteochondral cores (dia. = 16 mm, n = 50) were extracted from human cadaver knees (N = 13) at four anatomical locations and divided into quadrants. Absorption spectra were acquired in the spectral range 400-1100 nm from one quadrant. Reference biomechanical, biochemical composition, histological, and cartilage thickness measurements were obtained from two other quadrants. A multivariate statistical technique based on partial least squares (PLS) regression was then employed to investigate the correlation between the absorption spectra and tissue properties.Our results demonstrate that cartilage optical response correlates with its function, composition and morphology, as indicated by the significant relationship between spectral predicted and measured biomechanical (79.0% ⩽ R(2) ⩽ 80.3%, p < 0.0001), biochemical (65.1% ⩽ R(2) ⩽ 81.0%, p < 0.0001), and histological scores ([Formula: see text] = 83.3%, p < 0.0001) properties. Significant correlation was also obtained with the non-calcified cartilage thickness ([Formula: see text] = 83.2%, p < 0.0001).We conclude that optical absorption of human cartilage in the VIS and NIR spectral range correlates with the overall tissue properties, thus providing knowledge that could facilitate development of systems for rapid assessment of tissue integrity.

Effect of Oat Bran Fractions on Extrudates Made of Defatted Oats

Abstract: Oats are rich in dietary fibre (DF) especially in β-glucan which has several health-promoting effects. Oats are not commonly used in extruded snacks because they often result in a poor expansion and hard structure. In the present study, defatted wholegrain oat flour (WF) and defatted endosperm oat flour (EF) were used as starch sources for extrudates. Five differently treated oat bran fractions (untreated, ultra-fine ground, enzymatically hydrolysed and hot water-extracted solubles and residue) were added to EF (10 or 20 %), and their influence on the chemical, textural and structural properties of extrudates was investigated. Extrudates made of WF had a poor expansion (151 %) and hard texture (399 N), whereas EF formed a better expanded (199 %) and less hard product (149 N). Addition of oat bran concentrate (OBC) decreased the expansion (171–176 %) and resulted in a harder texture (200–265 N) compared to that of EF 100 % extrudates. The lower expansion of WF and OBC-enriched extrudates was due to the higher content of insoluble fibre. However, no statistical differences were detected between the untreated, ultra-fine ground and enzyme-hydrolysed OBC. The water-insoluble (WIS-OBC) and water-soluble (WS-OBC) fractions had opposite effects on the EF-based extrudates: 10 % addition of WIS-OBC fraction significantly decreased the expansion (163 %) and increased the hardness (313 N), whereas the addition of WS-OBC (10 or 20 %) enhanced the expansion (218–226 %) and resulted in less hard textures (131–146 N). The soluble fibres and low protein content in WS-OBC fraction were hypothesised to cause the improved expansion and decreased hardness. The results demonstrated that extrudates with acceptable expansion and hardness can be produced with defatted oat endosperm flour and oat bran fractions. However, the water-insoluble bran components had a negative effect on the textural properties of extrudates.

Cortical Bone Histomorphometry in Male Femoral Neck: The Investigation of Age-Association and Regional Differences

Abstract: Low bone volume and changes in bone quality or microarchitecture may predispose individuals to fragility fractures. As the dominant component of the human skeleton, cortical bone plays a key role in protecting bones from fracture. However, histological investigations of the underlying structural changes, which might predispose to fracture, have been largely limited to the cancellous bone. The aim of this study was to investigate the age-association and regional differences of histomorphometric properties in the femoral neck cortical bone. Undecalcified histological sections of the femoral neck (n = 20, aged 18–82 years, males) were cut (15 μm) and stained using modified Masson-Goldner stain. Complete femoral neck images were scanned, and cortical bone boundaries were defined using our previously established method. Cortical bone histomorphometry was performed with low (×50) and high magnification (×100). Most parameters related to cortical width (Mean Ct.Wi, Inferior Ct.Wi, Superior Ct.Wi) were negatively associated with age both before and after adjustment for height. The inferior cortex was the thickest (P < 0.001) and the superior cortex was the thinnest (P < 0.008) of all cortical regions. Both osteonal size and pores area were negatively associated with age. Osteonal area and number were higher in the antero-inferior area (P < 0.002) and infero-posterior area (P = 0.002) compared to the postero-superior area. The Haversian canal area was higher in the infero-posterior area compared to the postero-superior area (P = 0.002). Moreover, porosity was higher in the antero-superior area (P < 0.002), supero-anterior area (P < 0.002) and supero-posterior area (P < 0.002) compared to the infero-anterior area. Eroded endocortical perimeter (E.Pm/Ec.Pm) correlated positively with superior cortical width. This study describes the changes in cortical bone during ageing in healthy males. Further studies are needed to investigate whether these changes explain the increased susceptibility to femoral neck fractures.

Quantitative Evaluation of Knee Subchondral Bone Mineral Density Using Cone Beam Computed Tomography

Abstract: Contrast agent enhanced cone beam computed tomography (CE-CBCT), a technique capable of high-resolution in vivo imaging with small radiation dose, has been applied successfully for clinical diagnostics of cartilage degeneration, ie, osteoarthritis (OA) As an X-ray technique, CE-CBCT may also detect changes in mineral density of subchondral bone (volumetric bone mineral density, vBMD), known to be characteristic for OA However, its feasibility for density measurements is not clear due to limited signal-to-noise ratio and contrast of CBCT images In the present study, we created clinically applicable hydroxyapatite phantoms and determined vBMDs of cortical bone, trabecular bone, subchondral trabecular bone and subchondral plate of 10 cadaver (ex vivo) and 10 volunteer (in vivo) distal femora using a clinical CBCT scanner, and for reference, also using a conventional CT scanner Our results indicated strong linear correlations between the vBMD values measured with the CT and CBCT scanners $(R ^{2} > 090, p , however, absolute vBMD values were dependent on the scanner in use Further, the differences between the vBMDs of cortical bone, trabecular bone and subchondral bone were similar and independent of the scanner The present results indicate that vBMD values might not be directly comparable between different instruments However, based on our present and previous results, we propose that, for OA diagnostics, clinical CBCT enables not only quantitative analysis of articular cartilage but also subchondral bone vBMD Quantitative information on both cartilage and subchondral bone could be beneficial in OA diagnostics

Diagnosis of Knee Osteochondral Lesions With Ultrasound Imaging

Abstract: Evaluation of articular cartilage and subchondral bone is essential in the diagnosis of joint diseases and injuries Interobserver and intraobserver reproducibilities of arthroscopic grading are only poor to moderate Thus, for quantitative and objective evaluation of cartilage and subchondral bone, ultrasound arthroscopy (UA) has been introduced to clarify this dilemma Assessment of the clinical feasibility of high-frequency ultrasonography (US) during 6 knee arthroscopies was conducted, and the surgical technique is presented US imaging was conducted with a flexible 9-MHz US catheter inserted into the joint through conventional portals US and arthroscopy videos were synchronously recorded, and US parameters for cartilage and subchondral bone characteristics were measured Arthroscopy and US imaging were combined to perform cartilage grading UA produced quantitative data on lesion size, as well as cartilage quality, and showed subchondral bone changes Visualization of an osteochondritis dissecans lesion not detected by conventional arthroscopy and US-guided retrograde drilling were possible with UA To conclude, UA proved to be clinically feasible and aided in the diagnosis when assessing knee osteochondral lesions

Development of new criteria for cortical bone histomorphometry in femoral neck: intra- and inter-observer reproducibility

Abstract: Histomorphometry is commonly applied to study bone remodeling. Histological definitions of cortical bone boundaries have not been consistent. In this study, new criteria for specific definition of the transitional zone between the cortical and cancellous bone in the femoral neck were developed. The intra- and inter-observer reproducibility of this method was determined by quantitative histomorphometry and areal overlapping analysis. The undecalcified histological sections of femoral neck specimens (n = 6; from men aged 17–59 years) were processed and scanned to acquire histological images of complete bone sections. Specific criteria were applied to define histological boundaries. “Absolute cortex area” consisted of pure cortical bone tissue only, and was defined mainly based on the size of composite canals and their distance to an additional “guide” boundary (so-called “preliminary cortex boundary,” the clear demarcation line of density between compact cortex and sparse trabeculae). Endocortical bone area was defined by recognizing characteristic endocortical structures adjacent to the preliminary cortical boundary. The present results suggested moderate to high reproducibility for low-magnification parameters (e.g., cortical bone area). The coefficient of variation (CV %) ranged from 0.02 to 5.61 in the intra-observer study and from 0.09 to 16.41 in the inter-observer study. However, the intra-observer reproducibility of some high-magnification parameters (e.g., osteoid perimeter/endocortical perimeter) was lower (CV %, 0.33–87.9). The overlapping of three histological areas in repeated analyses revealed highest intra- and inter-observer reproducibility for the absolute cortex area. This study provides specific criteria for the definition of histological boundaries for femoral neck bone specimens, which may aid more precise cortical bone histomorphometry.

Ultrasound Backscattering Is Anisotropic in Bovine Articular Cartilage.

Abstract: Collagen, proteoglycans and chondrocytes can contribute to ultrasound scattering in articular cartilage. However, anisotropy of ultrasound scattering in cartilage is not fully characterized. We investigate this using a clinical intravascular ultrasound device with ultrasound frequencies of 9 and 40 MHz. Osteochondral samples were obtained from intact bovine patellas, and cartilage was imaged in two perpendicular directions: through articular and lateral surfaces. At both frequencies, ultrasound backscattering was higher (p < 0.05) when measured through the lateral surface of cartilage. In addition, the composition and structure of articular cartilage were investigated with multiple reference methods involving light microscopy, digital densitometry, polarized light microscopy and Fourier infrared imaging. Reference methods indicated that acoustic anisotropy of ultrasound scattering arises mainly from non-uniform distribution of chondrocytes and anisotropic orientation of collagen fibers. To conclude, ultrasound backscattering in articular cartilage was found to be anisotropic and dependent on the frequency in use.

Inter-individual changes in cortical bone three-dimensional microstructure and elastic coefficient have opposite effects on radial sound speed

Abstract: Knowledge about simultaneous contributions of tissue microstructure and elastic properties on ultrasound speed in cortical bone is limited. In a previous study, porosities and elastic coefficients of cortical bone in human femurs were shown to change with age. In the present study, influences of inter-individual and site-dependent variation in cortical bone microstructure and elastic properties on radial speed of sound (SOS; at 4, 6, and 8 MHz) were investigated using three-dimensional (3D) finite difference time domain modeling. Models with fixed (nominal model) and sample-specific (sample-specific model) values of radial elastic coefficients were compared. Elastic coefficients and microstructure for samples (n = 24) of human femoral shafts (n = 6) were derived using scanning acoustic microscopy and micro-computed tomography images, respectively. Porosity-related SOS varied more extensively in nominal models than in sample-specific models. Linear correlation between pore separation and SOS was similar (R = 0.8, p < 0.01, for 4 MHz) for both models. The determination coefficient (R(2)= 0.75, p < 0.05) between porosity and radial SOS, especially at 4 MHz, was highest in the posterior quadrant. The determination coefficient was lower for models with sample-specific values of radial elastic coefficient implemented (R(2) < 0.33, p < 0.05), than for nominal models (0.48 < R(2)< 0.63, p < 0.05). This information could be useful in in vivo pulse-echo cortical thickness measurements applying constant SOS.