| 1. |
- Inkinen, Satu, et al.
(författare)
-
Collagen and chondrocyte concentrations control ultrasound scattering in agarose scaffolds
- 2014
-
Ingår i: Ultrasound in Medicine and Biology. - : Elsevier. - 0301-5629 .- 1879-291X. ; 40:9, s. 2162-2171
-
Tidskriftsartikel (refereegranskat)abstract
- Ultrasound imaging has been proposed for diagnostics of osteoarthritis and cartilage injuries in vivo. However, the specific contribution of chondrocytes and collagen to ultrasound scattering in articular cartilage has not been systematically studied. We investigated the role of these tissue structures by measuring ultrasound scattering in agarose scaffolds with varying collagen and chondrocyte concentrations. Ultrasound catheters with center frequencies of 9 MHz (7.1–11.0 MHz, −6 dB) and 40 MHz (30.1–45.3 MHz, −6 dB) were applied using an intravascular ultrasound device. Ultrasound backscattering quantified in a region of interest starting right below sample surface differed significantly (p < 0.05) with the concentrations of collagen and chondrocytes. An ultrasound frequency of 40 MHz, as compared with 9 MHz, was more sensitive to variations in collagen and chondrocyte concentrations. The present findings may improve diagnostic interpretation of arthroscopic ultrasound imaging and provide information necessary for development of models describing ultrasound propagation within cartilage.
|
|
| 2. |
- Arokoski, Jari, et al.
(författare)
-
Nivelrikon etiopatogeneesi [Etiopathogenesis of osteoarthritis].
- 2001
-
Ingår i: Duodecim. - : Duodecim. - 0012-7183 .- 2242-3281. ; 117:16, s. 1617-1626
-
Tidskriftsartikel (refereegranskat)abstract
- Nivelrikon patofysiologia tunnetaan huonosti. Nykykäsityksen mukaan artroosissa ei olekyse nivelruston passiivisesta kulumisesta vaan biokemiallisesta tapahtumasarjasta, jossasoluväliaineen tuhoutuminen saa ylivallan rustoa korjaavista prosesseista. Nivelrikon alkuvaiheessarustosoluissa eli kondrosyyteissä aktivoituvat sekä ruston aineosien synteesitoimintaettä rustoa hajottavien entsyymien ilmentyminen ja niitä koodaavien geenientoiminta. Nivelrikko on koko nivelen sairaus, joka aiheuttaa muutoksia niin nivelrustossa,luussa kuin pehmytosissakin. Vallitsevan käsityksen mukaan nivelrikko käynnistyynivelruston pinnallisesta vyöhykkeestä. On myös esitetty, että nivelalueen altistuminenliialliselle kuormitukselle aiheuttaisi ensin rustonalaisen luun paksunemisen ja jäykkenemisen,mikä puolestaan altistaisi nivelruston suuremmille kuormittaville voimille. Riskitekijöistätärkeimpiä ovat ikääntyminen, liikapaino, niveleen kohdistuvat vammat ja ruumiillisentyön aiheuttama liikarasitus. Perinnöllisten tekijöiden osuus on myös merkittävä.Ruston kollageenien rakennevirheiden tiedetään altistavan nivelrikolle.
|
|
| 3. |
- Dahlberg, Leif E, et al.
(författare)
-
A first-in-human, double-blind, randomised, placebo-controlled, dose ascending study of intra-articular rhFGF18 (sprifermin) in patients with advanced knee osteoarthritis
- 2016
-
Ingår i: Clinical and Experimental Rheumatology. - 0392-856X. ; 34:3, s. 50-445
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To evaluate the safety of intra-articular sprifermin (primary), and to evaluate systemic exposure, biomarkers, histology, and other cartilage parameters in patients with advanced osteoarthritis (OA).METHODS: This was a first-in-human, double-blind, randomised, placebo-controlled trial of single and multiple ascending doses of sprifermin from 3-300 μg in knee OA patients scheduled for total knee replacement. Patients were randomised 3:1 to sprifermin or placebo, injected into the target knee once or once weekly for 3 weeks, and followed-up for 24 weeks.RESULTS: Fifty-five patients were treated with sprifermin, 25 with single and 30 with multiple doses, 18 received placebo. There was no clear difference between the active and placebo groups in incidence, severity, and nature of reported treatment emergent adverse events. Acute inflammatory reactions were slightly more common with sprifermin 300 μg, but none led to discontinuation. No clear difference was seen between placebo and sprifermin in physician-assessed local tolerability, pain, or swelling in the knee. No meaningful changes over time, or differences between treatment groups, were observed for safety laboratory parameters or ECG. Although individual abnormalities were observed, no patterns were evident suggesting a relation to treatment or potential safety concern. No systemic sprifermin exposure, anti-FGF18 antibodies, or clear-cut effects on systemic biomarkers were detected.CONCLUSIONS: This first clinical trial of sprifermin revealed no serious safety concerns, although larger studies are needed. The possibility of positive effects of intra-articular sprifermin on histological and other cartilage parameters in knee OA also warrant further investigation.
|
|
| 4. |
- Grassi, Lorenzo, et al.
(författare)
-
Elucidating failure mechanisms in human femurs during a fall to the side using bilateral digital image correlation
- 2020
-
Ingår i: Journal of Biomechanics. - : Elsevier BV. - 0021-9290. ; 106
-
Tidskriftsartikel (refereegranskat)abstract
- An improved understanding of the mechanical properties of human femurs is a milestone towards a more accurate assessment of fracture risk. Digital image correlation (DIC) has recently been adopted to provide full-field strain measurements during mechanical testing of femurs. However, it has typically been used to measure strains on the anterior side of the femur, whereas in both single-leg-stance and sideways fall loading conditions, the highest deformations result on the medial and lateral sides of the femoral neck. The goal of this study was to measure full-field deformations simultaneously on the medial and lateral side of the femoral neck in a configuration resembling a fall to the side. Twelve female cadaver femurs were prepared for DIC measurements and tested in sideways fall at 5 mm/s displacement rate. Two pairs of cameras recorded the medial and lateral side of the femoral neck, and deformations were calculated using DIC. The samples exhibited a two-stage failure: first, a compressive collapse on the superolateral side of the femoral neck in conjunction with peak force, followed by complete femoral neck fracture at the force drop following the post-elastic phase. DIC measurements corroborated this observation by reporting no tensile strains above yield limit for the medial side of the neck up to peak force. DIC measurements registered onto the bone micro-architecture showed strain localizations in proximity of cortical pores due to, for instance, blood vessels. This could explain previously reported discrepancies between simulations and experiments in regions rich with large pores, like the superolateral femoral neck.
|
|
| 5. |
- Grassi, Lorenzo, et al.
(författare)
-
Experimental Validation Of Finite Element Model For Proximal Composite Femur Using Optical Measurements
- 2013
-
Ingår i: Journal of the Mechanical Behavior of Biomedical Materials. - : Elsevier BV. - 1751-6161. ; 21, s. 86-94
-
Tidskriftsartikel (refereegranskat)abstract
- Patient-specific finite element models have been used to predict femur strength and fracture risk in individuals. Validation of the adopted finite element modelling procedure against mechanical testing data is a crucial step when aiming for clinical applications. The majority of the works available in literature used data from strain gages to validate the model, thus having up to 15 experimental measurements. Optical techniques, such as Digital Image Correlation, can help to improve the models by providing a continuous field of deformation data over a femoral surface. The main objective of this study was to validate finite element models of six composite femora against strain data from digital image correlation, obtained during fracture tests performed in quasi-axial loading configuration. The finite element models were obtained from CT scans, by means of a semi-automatic segmentation. The principal strains both during the elastic phase and close to the fracture were compared, and showed a correlation coefficient close to 0.9. In the linear region, the slope and intercept were close to zero and unity, while for the case when fracture load was simulated, the slope decreased somewhat. The accuracy of the obtained results is comparable with the state-of-the-art literature, with the significant improvement of having around 50000 data points for each femur. This large number of measurements allows a more comprehensive validation of the predictions by the finite element models, since thousand of points are tracked along the femoral neck and trochanter region, i.e., the sites that are most critical for femur fracture. Moreover, strain measurement biases due to the strain gage reinforcement effect, were avoided. The combined experimental-numerical approach proved to be ready for application to in-vitro tests of human cadaver femurs, thus helping to develop a suitable mechanistic fracture risk criterion.
|
|
| 6. |
- Grassi, Lorenzo, et al.
(författare)
-
Full-field Strain Measurement During Mechanical Testing of the Human Femur at Physiologically Relevant Strain Rates
- 2014
-
Ingår i: Journal of Biomechanical Engineering. - : ASME International. - 0148-0731 .- 1528-8951. ; 136:11
-
Tidskriftsartikel (refereegranskat)abstract
- Understanding the mechanical properties of human femora is of great importance for the development of a reliable fracture criterion aimed at assessing fracture risk. Earlier ex vivo studies have been conducted by measuring strains on a limited set of locations using strain gauges. Digital Image Correlation (DIC) could instead be used to reconstruct the full-field strain pattern over the surface of the femur. The objective of this study was to measure the full-field strain response of cadaver femora tested at a physiological strain rate up to fracture in a configuration resembling single stance. The three cadaver femora were cleaned from soft tissues, and a white background paint was applied with a random black speckle pattern over the anterior surface. The mechanical tests were conducted up to fracture at a constant displacement rate of 15 mm/s, and two cameras recorded the event at 3000 frames per second. DIC was performed to retrieve the full-field displacement map, from which strains were derived. A low-pass filter was applied over the measured displacements before the crack opened in order to reduce the noise level. The noise levels were assessed using a dedicated control plate. Conversely, no filtering was applied at the frames close to fracture to get the maximum resolution. The specimens showed a linear behavior of the principal strains with respect to the applied force up to fracture. The strain rate was comparable to the values available in literature from in-vivo measurements during daily activities. The cracks opened and fully propagated in less than 1 ms, and small regions with high values of the major principal strains could be spotted just a few frames before the crack opened. This corroborates the hypothesis of a strain-driven fracture mechanism in human bone. The data represents a comprehensive collection of full-field strains, both at physiological load levels and up to fracture. About 10000 measurements were collected for each bone, providing superior spatial resolution compared to ~15 measurements typically collected using strain gauges. These experimental data collection can be further used for validation of numerical models, and for experimental verification of bone constitutive laws and fracture criteria.
|
|
| 7. |
- Grassi, Lorenzo, et al.
(författare)
-
How accurately can subject-specific finite element models predict strains and strength of human femora? Investigation using full-field measurements
- 2016
-
Ingår i: Journal of Biomechanics. - : Elsevier BV. - 1873-2380 .- 0021-9290. ; 49:5, s. 802-806
-
Tidskriftsartikel (refereegranskat)abstract
- Subject-specific finite element models have been proposed as a tool to improve fracture risk assessment in individuals. A thorough laboratory validation against experimental data is required before introducing such models in clinical practice. Results from digital image correlation can provide full-field strain distribution over the specimen surface during in vitro test, instead of at a few pre-defined locations as with strain gauges. The aim of this study was to validate finite element models of human femora against experimental data from three cadaver femora, both in terms of femoral strength and of the full-field strain distribution collected with digital image correlation. The results showed a high accuracy between predicted and measured principal strains (R2=0.93, RMSE=10%, 1600 validated data points per specimen). Femoral strength was predicted using a rate dependent material model with specific strain limit values for yield and failure. This provided an accurate prediction (<2% error) for two out of three specimens. In the third specimen, an accidental change in the boundary conditions occurred during the experiment, which compromised the femoral strength validation. The achieved strain accuracy was comparable to that obtained in state-of-the-art studies which validated their prediction accuracy against 10–16 strain gauge measurements. Fracture force was accurately predicted, with the predicted failure location being very close to the experimental fracture rim. Despite the low sample size and the single loading condition tested, the present combined numerical-experimental method showed that finite element models can predict femoral strength by providing a thorough description of the local bone mechanical response.
|
|
| 8. |
- Grassi, Lorenzo, et al.
(författare)
-
Prediction of femoral strength using 3D finite element models reconstructed from DXA images: validation against experiments
- 2017
-
Ingår i: Biomechanics and Modeling in Mechanobiology. - : Springer Science and Business Media LLC. - 1617-7940 .- 1617-7959. ; 16:3, s. 989-1000
-
Tidskriftsartikel (refereegranskat)abstract
- Computed tomography (CT)-based finite element (FE) models may improve the current osteoporosis diagnostics and prediction of fracture risk by providing an estimate for femoral strength. However, the need for a CT scan, as opposed to the conventional use of dual-energy X-ray absorptiometry (DXA) for osteoporosis diagnostics, is considered a major obstacle. The 3D shape and bone mineral density (BMD) distribution of a femur can be reconstructed using a statistical shape and appearance model (SSAM) and the DXA image of the femur. Then, the reconstructed shape and BMD could be used to build FE models to predict bone strength. Since high accuracy is needed in all steps of the analysis, this study aimed at evaluating the ability of a 3D FE model built from one 2D DXA image to predict the strains and fracture load of human femora. Three cadaver femora were retrieved, for which experimental measurements from ex vivo mechanical tests were available. FE models were built using the SSAM-based reconstructions: using only the SSAM-reconstructed shape, only the SSAM-reconstructed BMD distribution, and the full SSAM-based reconstruction (including both shape and BMD distribution). When compared with experimental data, the SSAM-based models predicted accurately principal strains (coefficient of determination >0.83, normalized root-mean-square error <16%) and femoral strength (standard error of the estimate 1215 N). These results were only slightly inferior to those obtained with CT-based FE models, but with the considerable advantage of the models being built from DXA images. In summary, the results support the feasibility of SSAM-based models as a practical tool to introduce FE-based bone strength estimation in the current fracture risk diagnostics.
|
|
| 9. |
- Helminen, Heikki, et al.
(författare)
-
Kuormituksen vaikutus nivelrustoon [The effects of loading on articular cartilage].
- 1992
-
Ingår i: Duodecim. - : Duodecim. - 0012-7183 .- 2242-3281. ; 108:12, s. 1097-1107
-
Forskningsöversikt (refereegranskat)abstract
- Nivelen kuormitus on tärkeimpiä nivelruston aineenvaihduntaan ja rakenteeseen vaikuttavia fysiologisia tekijöitä. Kohtuullinen rytminen kuormitus lisää nuoren ihmisen nivelruston proteoglykaanipitoisuutta. Tämän vaikutuksesta rusto jäykistyy ja kasvaa paksuutta. Hyvin voimakas kuormitus ei aiheuta tällaista positiivista vastetta. Toisaalta nivelkuormituksen puuttuminen pienentää ruston proteoglykaanipitoisuutta ja heikentää kimmo-ominaisuuksia. Nämä surkastumismuutokset ovat suurimmaksi osaksi–elleivät kokonaan–korjautuvia. Kohtuullisella nivelkuormituksella voidaan siis ylläpitää ja parantaa nivelruston ominaisuuksia. Pitkäaikaisen liikkumattomuuden jälkeen nivelrusto on heikompi kuin normaalisti ja voi vaurioitua niveltä voimakkaasti kuormitettaessa. Siksi nivelen kuormitusta pitää lisätä toipumisvaiheessa vähitellen.
|
|
| 10. |
|
|
| 11. |
|
|
| 12. |
- Honkanen, Juuso, et al.
(författare)
-
Cationic contrast agent diffusion differs between cartilage and meniscus
- 2016
-
Ingår i: Annals of Biomedical Engineering. - : Springer. - 0090-6964 .- 1573-9686. ; 44:10, s. 2913-2921
-
Tidskriftsartikel (refereegranskat)abstract
- Contrast enhanced computed tomography (CECT) is a non-destructive imaging technique used for the assessment of composition and structure of articular cartilage and meniscus. Due to structural and compositional differences between these tissues, diffusion and distribution of contrast agents may differ in cartilage and meniscus. The aim of this study is to determine the diffusion kinematics of a novel iodine based cationic contrast agent (CA(2+)) in cartilage and meniscus. Cylindrical cartilage and meniscus samples (d = 6 mm, h ≈ 2 mm) were harvested from healthy bovine knee joints (n = 10), immersed in isotonic cationic contrast agent (20 mgI/mL), and imaged using a micro-CT scanner at 26 time points up to 48 h. Subsequently, normalized X-ray attenuation and contrast agent diffusion flux, as well as water, collagen and proteoglycan (PG) contents in the tissues were determined. The contrast agent distributions within cartilage and meniscus were different. In addition, the normalized attenuation and diffusion flux were higher (p < 0.05) in cartilage. Based on these results, diffusion kinematics vary between cartilage and meniscus. These tissue specific variations can affect the interpretation of CECT images and should be considered when cartilage and meniscus are assessed simultaneously.
|
|
| 13. |
- Julkunen, Petro, et al.
(författare)
-
A Review of the Combination of Experimental Measurements and Fibril-Reinforced Modeling for Investigation of Articular Cartilage and Chondrocyte Response to Loading
- 2013
-
Ingår i: Computational & Mathematical Methods in Medicine. - : Hindawi Limited. - 1748-6718 .- 1748-670X.
-
Forskningsöversikt (refereegranskat)abstract
- The function of articular cartilage depends on its structure and composition, sensitively impaired in disease (e. g. osteoarthritis, OA). Responses of chondrocytes to tissue loading are modulated by the structure. Altered cell responses as an effect of OA may regulate cartilage mechanotransduction and cell biosynthesis. To be able to evaluate cell responses and factors affecting the onset and progression of OA, local tissue and cell stresses and strains in cartilage need to be characterized. This is extremely challenging with the presently available experimental techniques and therefore computational modeling is required. Modern models of articular cartilage are inhomogeneous and anisotropic, and they include many aspects of the real tissue structure and composition. In this paper, we provide an overview of the computational applications that have been developed for modeling the mechanics of articular cartilage at the tissue and cellular level. We concentrate on the use of fibril-reinforced models of cartilage. Furthermore, we introduce practical considerations for modeling applications, including also experimental tests that can be combined with the modeling approach. At the end, we discuss the prospects for patient-specific models when aiming to use finite element modeling analysis and evaluation of articular cartilage function, cellular responses, failure points, OA progression, and rehabilitation.
|
|
| 14. |
- Julkunen, Petro, et al.
(författare)
-
Biomechanical, biochemical and structural correlations in immature and mature rabbit articular cartilage.
- 2009
-
Ingår i: Osteoarthritis and Cartilage. - : Saunders Elsevier. - 1063-4584 .- 1522-9653. ; 17:12, s. 1628-1638
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: The structure and composition of articular cartilage change during development and growth. These changes lead to alterations in the mechanical properties of cartilage. In the present study, biomechanical, biochemical and structural relationships of articular cartilage during growth and maturation of rabbits are investigated.DESIGN: Articular cartilage specimens from the tibial medial plateaus and femoral medial condyles of female New Zealand white rabbits were collected from seven age-groups; 0 days (n=29), 11 days (n=30), 4 weeks (n=30), 6 weeks (n=30), 3 months (n=24), 6 months (n=24) and 18 months (n=19). The samples underwent mechanical testing under creep indentation. From the mechanical response, instantaneous and equilibrium moduli were determined. Biochemical analyses of tissue collagen, hydroxylysylpyridinoline (HP) and pentosidine (PEN) cross-links in full thickness cartilage samples were conducted. Proteoglycans were investigated depth-wise from the tissue sections by measuring the optical density of Safranin-O-stained samples. Furthermore, depth-wise collagen architecture of articular cartilage was analyzed with polarized light microscopy. Finite element analyses of the samples from different age-groups were conducted to reveal tensile and compressive properties of the fibril network and the matrix of articular cartilage, respectively.RESULTS: Tissue thickness decreased from approximately 3 to approximately 0.5mm until the age of 3 months, while the instantaneous modulus increased with age prior to peak at 4-6 weeks. A lower equilibrium modulus was observed before 3-month-age, after which the equilibrium modulus continued to increase. Collagen fibril orientation angle and parallelism index were inversely related to the instantaneous modulus, tensile fibril modulus and tissue thickness. Collagen content and cross-linking were positively related to the equilibrium compressive properties of the tissue.CONCLUSIONS: During maturation, significant modulation of tissue structure, composition and mechanical properties takes place. Importantly, the present study provides insight into the mechanical, chemical and structural interactions that lead to functional properties of mature articular cartilage.
|
|
| 15. |
- Julkunen, Petro, et al.
(författare)
-
Stress-relaxation of human patellar articular cartilage in unconfined compression : prediction of mechanical response by tissue composition and structure.
- 2008
-
Ingår i: Journal of Biomechanics. - : Elsevier. - 0021-9290 .- 1873-2380. ; 41:9, s. 1978-86
-
Tidskriftsartikel (refereegranskat)abstract
- Mechanical properties of articular cartilage are controlled by tissue composition and structure. Cartilage function is sensitively altered during tissue degeneration, in osteoarthritis (OA). However, mechanical properties of the tissue cannot be determined non-invasively. In the present study, we evaluate the feasibility to predict, without mechanical testing, the stress-relaxation response of human articular cartilage under unconfined compression. This is carried out by combining microscopic and biochemical analyses with composition-based mathematical modeling. Cartilage samples from five cadaver patellae were mechanically tested under unconfined compression. Depth-dependent collagen content and fibril orientation, as well as proteoglycan and water content were derived by combining Fourier transform infrared imaging, biochemical analyses and polarized light microscopy. Finite element models were constructed for each sample in unconfined compression geometry. First, composition-based fibril-reinforced poroviscoelastic swelling models, including composition and structure obtained from microscopical and biochemical analyses were fitted to experimental stress-relaxation responses of three samples. Subsequently, optimized values of model constants, as well as compositional and structural parameters were implemented in the models of two additional samples to validate the optimization. Theoretical stress-relaxation curves agreed with the experimental tests (R=0.95-0.99). Using the optimized values of mechanical parameters, as well as composition and structure of additional samples, we were able to predict their mechanical behavior in unconfined compression, without mechanical testing (R=0.98). Our results suggest that specific information on tissue composition and structure might enable assessment of cartilage mechanics without mechanical testing.
|
|
| 16. |
- Kallioniemi, Antti, et al.
(författare)
-
Contrast agent enhanced pQCT of articular cartilage.
- 2007
-
Ingår i: Physics in Medicine and Biology. - : Institute of Physics Publishing (IOPP). - 0031-9155 .- 1361-6560. ; 52:4, s. 1209-1219
-
Tidskriftsartikel (refereegranskat)abstract
- The delayed gadolinium enhanced MRI of cartilage (dGEMRIC) technique is the only non-invasive means to estimate proteoglycan (PG) content in articular cartilage. In dGEMRIC, the anionic paramagnetic contrast agent gadopentetate distributes in inverse relation to negatively charged PGs, leading to a linear relation between T1,Gd and spatial PG content in tissue. In the present study, for the first time, contrast agent enhanced peripheral quantitative computed tomography (pQCT) was applied, analogously to dGEMRIC, for the quantitative detection of spatial PG content in cartilage. The suitability of two anionic radiographic contrast agents, gadopentetate and ioxaglate, to detect enzymatically induced PG depletion in articular cartilage was investigated. First, the interrelationships of x-ray absorption, as measured with pQCT, and the contrast agent solution concentration were investigated. Optimal contrast agent concentrations for the following experiments were selected. Second, diffusion rates for both contrast agents were investigated in intact (n=3) and trypsin-degraded (n=3) bovine patellar cartilage. The contrast agent concentration of the cartilaginous layer was measured prior to and 2-27 h after immersion. Optimal immersion time for the further experiments was selected. Third, the suitability of gadopentetate and ioxaglate enhanced pQCT to detect the enzymatically induced specific PG depletion was investigated by determining the contrast agent concentrations and uronic acid and water contents in digested and intact osteochondral samples (n=16). After trypsin-induced PG loss (-70%, p<0.05) the penetration of gadopentetate and ioxaglate increased (p<0.05) by 34% and 48%, respectively. Gadopentetate and ioxaglate concentrations both showed strong correlation (r=-0.95, r=-0.94, p<0.01, respectively) with the uronic acid content. To conclude, contrast agent enhanced pQCT provides a technique to quantify PG content in normal and experimentally degraded articular cartilage in vitro. As high resolution imaging of e.g. the knee joint is possible with pQCT, the present technique may be further developed for in vivo quantification of PG depletion in osteoarthritic cartilage. However, careful in vitro and in vivo characterization of diffusion mechanics and optimal contrast agent concentrations are needed before diagnostic applications are feasible.
|
|
| 17. |
- Khayyeri, Hanifeh, et al.
(författare)
-
A novel semi-automatic hip morphology assessment tool is more accurate than manual radiographic evaluations
- 2020
-
Ingår i: Computer Methods in Biomechanics and Biomedical Engineering: Imaging and Visualization. - : Informa UK Limited. - 2168-1163 .- 2168-1171. ; 8:1, s. 76-86
-
Tidskriftsartikel (refereegranskat)abstract
- Radiological and pathological characteristics of hip osteoarthritis (OA) is joint-space loss due to degradation of articular cartilage. However, patients with early-stage OA do not yet show any radiological signs, which leaves them without diagnosis and treatment. This study evaluates the potential of a novel tool to identify pre-radiographic OA changes based on hip bone morphology. Two statistical appearance models for femur and pelvis were used to estimate the 3Dmorphology of the hip bones based on planar radiographs from patients. Well-known hip geometrical parameters (n = 22) were computed from patient CT scans (truth), 3D reconstructions (new method) and radiographs (calculated manually). The methods were compared by measuring relative error to truth. The new method was significantly more accurate in calculating hip geometrical parameters than the manual 2D calculations. The proposed approach could also capture rotational parameters like cross-over sign and anterior wall sign (100% correct predictions). The method can successfully reconstruct 3D hip shapes and densities for patients that have not yet developed severe osteoarthritis, and provided higher precision than manual estimations. Thus, it may be used to calculate morphological parameters that are predictors of OA and can become a powerful tool in human hip OA research and diagnostics.
|
|
| 18. |
- Kinnunen, Jussi, et al.
(författare)
-
Nondestructive fluorescence-based quantification of threose-induced collagen cross-linking in bovine articular cartilage
- 2012
-
Ingår i: Journal of Biomedical Optics. - : SPIE - International Society for Optical Engineering. - 1083-3668 .- 1560-2281. ; 17:9, s. 97003-
-
Tidskriftsartikel (refereegranskat)abstract
- Extensive collagen cross-linking affects the mechanical competence of articular cartilage: it can make the cartilage stiffer and more brittle. The concentrations of the best known cross-links, pyridinoline and pentosidine, can be accurately determined by destructive high-performance liquid chromatography (HPLC). We explore a nondestructive evaluation of cross-linking by using the intrinsic fluorescence of the intact cartilage. Articular cartilage samples from bovine knee joints were incubated in threose solution for 40 and 100 h to increase the collagen cross-linking. Control samples without threose were also prepared. Excitation-emission matrices at wavelengths of 220 to 950 nm were acquired from the samples, and the pentosidine and pyridinoline cross-links and the collagen concentrations were determined using HPLC. After the threose treatment, pentosidine and lysyl pyridinole (LP) concentrations increased. The intrinsic fluorescence, excited below 350 nm, decreased and was related to pentosidine [r=−0.90, 240/325nm (excitation/emission)] or LP (r=−0.85, 235/285nm) concentrations. Due to overlapping, the changes in emission could not be linked specifically to the recorded cross-links. However, the fluorescence signal enabled a nondestructive optical estimate of changes in the pentosidine and LP cross-linking of intact articular cartilage.
|
|
| 19. |
- Kiviranta, Ilkka, et al.
(författare)
-
Effects of mechanical loading and immobilization on the articular cartilage
- 1997
-
Ingår i: Bailliere's Clinical Orthopaedics. - 1074-8814. ; 2:1, s. 109-122
-
Forskningsöversikt (refereegranskat)abstract
- Articular cartilage provides nearly frictionless surfaces for joint movemants and reduces contact pressures, protecting the underlying suchondral bone from excess stress. The unique properties of articular cartilage are based on the interaction of the main components of the extracellular matrix: proteoglycans (PGs), collagen and interstitial fluid. Animal experiments and in vitro studies demonstrate that one of the most important regulators of the extracellular matrix metabolism is mechanical loading acting on the joints. Unloading and immobilization leads to PG depletion and softening of articular cartilage, increasing the risk of permanent cartilage degeneration. Moderate running exercise and increased weight bearing increases cartilage thickness, PG concentration and improves biomechanical properties of articular cartilage. With further increase in training intensity this positive influence of exercise disappears and cartilage shows changes analogous to immobilization of the joint, i.e. PG depletion and softening of the tissue. In humans most epidemiological studies have failed to prove the connection between running training and cartilage degeneration, but there is evidence that sports activities exposing joints to impact loading might increase the risk of osteoarthrosis.
|
|
| 20. |
- Kobrina, Yevgeniya, et al.
(författare)
-
Clustering of infrared spectra reveals histological zones in intact articular cartilage
- 2012
-
Ingår i: Osteoarthritis and Cartilage. - : Elsevier BV. - 1063-4584. ; 20:5, s. 460-468
-
Tidskriftsartikel (refereegranskat)abstract
- Objective: Articular cartilage (AC) exhibits specific zonal structure that follows the organization of collagen network and concentration of tissue constituents. The aim of this study was to investigate the potential of unsupervised clustering analysis applied to Fourier transform infrared (FIR) microspectroscopy to detect depth-dependent structural and compositional differences in intact AC. Method: Seven rabbit and eight bovine intact patellae AC samples were imaged using FTIR microspectroscopy and normalized raw spectra were clustered using the fuzzy C-means algorithm. Differences in mean spectra of clusters were investigated by quantitative estimation of collagen and proteoglycan (PG) contents, as well as by careful visual investigation of locations of spectral changes. Results: Clustering revealed the typical layered structure of AC in both species. However, more distinct clusters were found for rabbit samples, whereas bovine AC showed more complex layered structure. In both species, clustering structure corresponded with that in polarized light microscopic (PLM) images; however, some differences were also observed. Spectral differences between clusters were identified at the same spectral locations for both species. Estimated PG/collagen ratio decreased significantly from superficial to middle or deep zones, which might explain the difference in clustering results compared to PLM. Conclusion: FTIR microspectroscopy in combination with cluster analysis allows detailed examination of spatial changes in AC. As far as we know, no previous single technique could reveal a layered structure of AC without any a priori information. (C) 2012 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.
|
|
| 21. |
- Koistinen, Arto P, et al.
(författare)
-
Short-term exercise-induced improvements in bone properties are for the most part not maintained during aging in hamsters.
- 2014
-
Ingår i: Experimental Gerontology. - : Elsevier BV. - 1873-6815 .- 0531-5565. ; 51, s. 46-53
-
Tidskriftsartikel (refereegranskat)abstract
- Physical exercise during growth affects composition, structure and mechanical properties of bone. In this study we investigated whether the beneficial effects of exercise during the early growth phase have long-lasting effects or not. Female Syrian golden hamsters (total n=152) were used in this study. Half of the hamsters had access to running wheels during their rapid growth phase (from 1 to 3months of age). The hamsters were sacrificed at the ages of 1, 3, 12, and 15months. The diaphysis of the mineralized humerus was analyzed with microCT and subjected to three-point-bending mechanical testing. The trabecular bone in the tibial metaphysis was also analyzed with microCT. The collagen matrix of the humerus bone was studied by tensile testing after decalcification. The weight of the hamsters as well as the length of the bone and the volumetric bone mineral density (BMDvol) of the humerus was higher in the running group at the early age (3months). Moreover, the mineralized bone showed improved mechanical properties in humerus and had greater trabecular thickness in the subchondral bone of tibia in the runners. However, by the age of 12 and 15months, these differences were equalized with the sedentary group. The tensile strength and Young's modulus of decalcified humerus were higher in the runners at early stage, indicating a stronger collagen network. In tibial metaphysis, trabecular thickness was significantly higher for the runners in the old age groups (12 and 15months). Our study demonstrates that physical exercise during growth improves either directly or indirectly through weight gain bone properties of the hamsters. However, the beneficial effects were for the most part not maintained during aging.
|
|
| 22. |
- Kopakkala-Tani, Milla, et al.
(författare)
-
Ultrasound stimulates proteoglycan synthesis in bovine primary chondrocytes.
- 2006
-
Ingår i: Biorheology. - : IOS Press. - 0006-355X .- 1878-5034. ; 43:3-4, s. 271-282
-
Tidskriftsartikel (refereegranskat)abstract
- Mechanical forces can stimulate the production of extracellular matrix molecules. We tested the efficacy of ultrasound to increase proteoglycan synthesis in bovine primary chondrocytes. The ultrasound-induced temperature rise was measured and its contribution to the synthesis was investigated using bare heat stimulus. Chondrocytes from five cellular isolations were exposed in triplicate to ultrasound (1 MHz, duty cycle 20%, pulse repetition frequency 1 kHz) at average intensity of 580 mW/cm2 for 10 minutes daily for 1-5 days. Temperature evolution was recorded during the sonication and corresponding temperature history was created using a controllable water bath. This exposure profile was used in 10-minute-long heat treatments of chondrocytes. Heat shock protein 70 (Hsp70) levels after one-time treatment to ultrasound and heat was analyzed by Western blotting, and proteoglycan synthesis was evaluated by 35S-sulfate incorporation. Ultrasound treatment did not induce Hsp70, while heat treatment caused a slight heat stress response. Proteoglycan synthesis was increased approximately 2-fold after 3-4 daily ultrasound stimulations, and remained at that level until day 5 in responsive cell isolates. However, chondrocytes from one donor cell isolation out of five remained non-responsive. Heat treatment alone did not increase proteoglycan synthesis. In conclusion, our study confirms that pulsed ultrasound stimulation can induce proteoglycan synthesis in chondrocytes.
|
|
| 23. |
- Kulmala, Katariina, et al.
(författare)
-
Diffusion of ionic and non-ionic contrast agents in articular cartilage with increased cross-linking : contribution of steric and electrostatic effects
- 2013
-
Ingår i: Medical Engineering and Physics. - : Elsevier. - 1350-4533 .- 1873-4030. ; 35:10, s. 1415-20
-
Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: To investigate the effect of threose-induced collagen cross-linking on diffusion of ionic and non-ionic contrast agents in articular cartilage.DESIGN: Osteochondral plugs (Ø=6mm) were prepared from bovine patellae and divided into two groups according to the contrast agent to be used in contrast enhanced computed tomography (CECT) imaging: (I) anionic ioxaglate and (II) non-ionic iodixanol. The groups I and II contained 7 and 6 sample pairs, respectively. One of the paired samples served as a reference while the other was treated with threose to induce collagen cross-linking. The equilibrium partitioning of the contrast agents was imaged after 24h of immersion. Fixed charge density (FCD), water content, contents of proteoglycans, total collagen, hydroxylysyl pyridinoline (HP), lysyl pyridinoline (LP) and pentosidine (Pent) cross-links were determined as a reference.RESULTS: The equilibrium partitioning of ioxaglate (group I) was significantly (p=0.018) lower (-23.4%) in threose-treated than control samples while the equilibrium partitioning of iodixanol (group II) was unaffected by the threose-treatment. FCD in the middle and deep zones of the cartilage (p<0.05) and contents of Pent and LP (p=0.001) increased significantly due to the treatment. However, the proteoglycan concentration was not systematically altered after the treatment. Water content was significantly (-3.5%, p=0.007) lower after the treatment.CONCLUSIONS: Since non-ionic iodixanol showed no changes in partition after cross-linking, in contrast to anionic ioxaglate, we conclude that the cross-linking induced changes in charge distribution have greater effect on diffusion compared to the cross-linking induced changes in steric hindrance.
|
|
| 24. |
- Lammi, Mikko, 1961-, et al.
(författare)
-
Undersulfated chondroitin sulfate does not increase in osteoarthritic cartilage.
- 2004
-
Ingår i: Journal of Rheumatology. - : Journal of Rheumatology. - 0315-162X .- 1499-2752. ; 31:12, s. 2449-2453
-
Tidskriftsartikel (refereegranskat)abstract
- 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. Fragmentation of the proteoglycans due to proteolytic processing was estimated with agarose gel electrophoresis. The molar ratios of chondroitin sulfate isoforms in the extracted proteoglycans were determined with fluorophore-assisted carbohydrate electrophoresis.RESULTS: Loss of proteoglycans and accumulation of tissue water was evident in groups II and III, and progressive OA increased heterogeneity of aggrecan population in groups II and III. Importantly, the molar ratio of nonsulfated disaccharide was decreased in the osteoarthritic articular cartilage.CONCLUSION: The structure of chondroitin sulfate in degenerated bovine cartilage did not support the hypothesis that sulfate depletion is present in osteoarthritic joint.
|
|
| 25. |
- Lötjönen, Pauno, et al.
(författare)
-
Strain-dependent modulation of ultrasound speed in articular cartilage under dynamic compression.
- 2009
-
Ingår i: Ultrasound in Medicine and Biology. - : Elsevier. - 1879-291X .- 0301-5629. ; 35:7, s. 1177-1184
-
Tidskriftsartikel (refereegranskat)abstract
- Mechanical properties of articular cartilage may be determined by means of mechano-acoustic indentation, a clinically feasible technique for cartilage diagnostics. Unfortunately, ultrasound speed varies in articular cartilage during mechanical compression. This can cause significant errors to the measured mechanical parameters. In this study, the strain-dependent variation in ultrasound speed was investigated during dynamic compression. In addition, we estimated errors that were induced by the variation in ultrasound speed on the mechano-acoustically measured elastic properties of the tissue. Further, we validated a computational method to correct these errors. Bovine patellar cartilage samples (n = 7) were tested under unconfined compression. Strain-dependence of ultrasound speed was determined under different compressive strains using an identical strain-rate. In addition, the modulation of ultrasound speed was simulated using the transient compositional and structural changes derived from fibril-reinforced poroviscoelastic (FRPVE) model. Experimentally, instantaneous compressive strain modulated the ultrasound speed (p < 0.05) significantly. The decrease of ultrasound speed was found to change nonlinearly as a function of strain. Immediately after the ramp loading ultrasound speed was found to be changed -0.94%, -1.49%, -1.84%, -1.87%, -1.89% and -2.15% at the strains of 2.4%, 4.9%, 7.3%, 9.7%, 12.1% and 14.4%, respectively. The numerical simulation revealed that the compression-related decrease in ultrasound speed induces significant errors in the mechano-acoustically determined strain (39.7%) and dynamic modulus (72.1%) at small strains, e.g., at 2.4%. However, at higher strains, e.g., at 14.4%, the errors were smaller, i.e., 12.6% for strain and 14.5% for modulus. After the proposed computational correction, errors related to ultrasound speed were decreased. By using the correction, with e.g., 2.4% strain, errors in strain and modulus were decreased from 39.7% to 7.2% and from 72.1% to 35.3%, respectively. The FRPVE model, addressing the changes in fibril orientation and void ratio during compression, showed discrepancy of less than 1% between the predicted and measured ultrasound speed during the ramp compression.
|
|
