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Biomedical subjects

J Jurvelin

Publications and source records attributed to J Jurvelin.

At least 19 recordsLinked to original sources
PubMed1995

Indentation instrument for the measurement of cartilage stiffness under arthroscopic control.

Changes in the biomechanical properties of articular cartilage are one of the first signs of the tissue degeneration. We have developed a small size indentation instrument for the quantification of cartilage stiffness under arthroscopic control. During measurement, the indenter imposes a constant deformation on the cartilage and the maximal indenter force, by which the cartilage resists the deformation, is used as a measure for cartilage stiffness. The instrument has been tested in laboratory conditions with elastomer and cadaver knee joint cartilage samples. A linear relationship was found between indenter force and elastomer stiffness (r = 0.990, n = 14) as well as between indenter force and cartilage shear modulus obtained by a reference device (r = 0.879, n = 22). Also, the correlation between two repeated measurements at the measurement sites, used to evaluate the reproducibility, was linear (r = 0.953, n = 16). Quantitative detection of cartilage stiffness is possible with the instrument.

Arthroscopes↗
PubMed1995

Ultrasound attenuation of the calcaneus in normal subjects and in patients with wrist fracture.

We determined broadband ultrasound attenuation (BUA) of the calcaneus, and bone mineral density (BMD) of the spine, proximal femur and radius in 137 healthy subjects (79 women and 58 men) and in 56 women with Colles' fracture. The repeated measurements on 9 healthy subjects indicated a short-term reproducibility (coefficient of variation) of 4 percent for BUA. There was a small (7 percent) but significant difference in BUA between normal men and women. The age-dependence in normal subjects was weak. When all the study subjects were pooled, modest correlations between BUA of the calcaneus and BMD at all measured skeletal sites were found (rs values 0.3-0.4). However, it was not possible to make an accurate prediction of the axial BMD, using BUA. BUA values were 13 percent lower in the wrist fracture patients than in the age-matched normals. In general, BUA could discriminate the fracture patients from normals as effectively as BMD. As suggested by the physical theory of ultrasound attenuation, our results support the idea that BUA reflects not only the bone density but also other factors related to the structural properties of bone.

Absorptiometry, Photon↗
PubMed1994

Articular cartilage thickness and glycosaminoglycan distribution in the young canine knee joint after remobilization of the immobilized limb.

The recovery of articular cartilage from atrophy induced by joint immobilization was investigated in immature dogs. In a previous study, we showed that 11 weeks of immobilization of the knee (stifle) joint of young dogs reduced the concentration of articular cartilage glycosaminoglycans (GAGs) by 13-47%. In the present study, right hindlimbs from six female beagles were immobilized for 11 weeks, as in the previous study, and then were remobilized for 15 weeks. Cartilage from the knee joint was compared with cartilage from nonimmobilized knees of eight age-matched control beagles. Histological samples taken from 11 different locations of the knee joint were stained with safranin O, and microspectrophotometry was used to demonstrate distribution of GAGs in the tissue. After remobilization, GAG concentration was restored in the patellofemoral region and tibial condyles. On the summits of the femoral condyles, and especially at the periphery of the femoral condyles, GAG concentration remained 8-26% less than the control values. On the summits, the thickness of the uncalcified cartilage was as much as 15% less than in the age-matched controls. Consequently, the changes induced by unloading were reversible to a great extent, but a full restoration of articular cartilage was not obtained at all sites of the knee joint within the 15 weeks of remobilization. Immobilization of the skeletally immature joint therefore may affect the development of articular cartilage in such a way that very slow recovery or permanent alterations are induced.

Animals↗
PubMed1994

Softening of the lateral condyle articular cartilage in the canine knee joint after long distance (up to 40 km/day) running training lasting one year.

The effects of long distance running training (up to 40km/day) on the biomechanical properties of young canine articular cartilage were investigated using in situ indentation creep technique. The stiffness of articular cartilage was determined in the form of instantaneous and equilibrium shear moduli. The rate of cartilage deformation was also computed. Microspectrophotometric and polarized light microscopic analyses were made for determination of local glycosaminoglycan content and collagen organization, respectively. During a period of one year, the runner dogs (n = 10) underwent a gradually increased treadmill exercise up to 40 km/day, while the littermate control dogs (n = 10) lived normally in their cages. The equilibrium shear modulus of articular cartilage decreased significantly by 12 to 14% (p < 0.05) in the lateral, but not in the medial, condyles of femur and tibia. In the lateral condyles of the runner dogs, the deformation rate of cartilage increased by 16% (p < 0.05). Consequently, the articular cartilage response to running training was site-dependent. The simultaneous changes of the equilibrium shear modulus or the retardation time spectrum and the glycosaminoglycan content confirm the key role of proteoglycans in modulating the cartilage equilibrium stiffness and creep rate. The changes in the instant shear modulus appeared to be predominantly related to the alterations in the organization of the superficial collagen network. Although the running training did not create cartilage damage, we assume that the softening of the cartilage may with time jeopardize the ability of articular cartilage to maintain its normal structural and functional properties.

Animals↗
PubMed1994

A Finnish multicentre quality assurance project in bone scintigraphy and brain SPET: a phantom study.

We examined all routinely used bone scintigraphy and brain single photon emission tomographic (SPET) systems in 19 laboratories in Finland. Physical performance of bone scintigraphy systems was measured with a 57Co flood source and with a NEMA resolution phantom. Total performance of the systems was evaluated with a transmission phantom simulating bone imaging of the thorax. It was acquired both with the protocol used in a given laboratory and with a fixed protocol. The participant laboratories were asked to report all accumulations on a diagrammatic thorax drawing. Tomographic uniformity, contrast and resolution (i.e. physical performance) of the SPET systems were evaluated with a special phantom. In addition, a Hoffman brain phantom was measured with routinely used acquiring and reconstruction protocols (total performance). All measurements were performed with the same test objects supervised by the same physicist. Manufacturer, age or the collimator of the camera did not correlate with the physical performance of the imaging systems (r < 0.65). This is probably due to lack of regular quality control of the gamma cameras in some laboratories. Comparison of the physical and the total performance shows that the detector itself is not necessarily responsible for inaccurate findings from the test object. Use of dual intensity and digital images in both scintigraphy could certainly increase the sensitivity of the findings: sensitivity of single intensity images was 65% (33-89%), dual 73% (28-100%), analog 65% (28-100%) and digital 74% (50-94%). Standardization of acquisition and reconstruction protocols will improve quality of brain SPET images and comparability between laboratories. This study showed the need for objective audit tests of bone scintigraphy and brain SPET systems in Finland.

Bone and Bones↗
PubMed1994

Proteoglycan and collagen alterations in canine knee articular cartilage following 20 km daily running exercise for 15 weeks.

The composition of extracellular matrix was studied at 11 different sites in the knee (stifle) articular cartilage of young beagle dogs after running exercise of 15 weeks, 20 km/day. Water content was significantly elevated by 5-17% in the patellofemoral groove and in anterior and intermediate sites on the lateral condyle of femur. Collagen content was decreased by 14 to 20% in the same sites of the lateral condyle. Proteoglycan (PG) content was not significantly changed except in the posterior edge of the medial condyle of femur with a 30% decrease. The proportion of PGs capable of reaggregation with hyaluronan was increased in tibial and femoral surfaces (mean of all sites +18%). Also, the aggregating PG monomers were larger at all sites, as studied by agarose gel electrophoresis. The chondroitin-6 to 4-sulphate ratio was reduced at the summits of femoral condyles and patella by 10 to 25%, but increased in the patellar surface of femur and tibial medial condyle, fitting to a previous finding that strenuous running depleted proteoglycans at the summits of femoral condyle from the superficial zone that is rich in chondroitin-6-sulphate. The increased water content, accompanied with a decreased concentration of collagen in the lateral femoral condyle, suggests loosening of the collagenous framework, an idea compatible with an earlier notion of superficial depletion of PGs in these sites, and possibly predisposing to degeneration. The size increase of the aggregating PGs probably indicate that a larger proportion of matrix PGs were newly synthesized and hence the turnover rate of the PGs was enhanced. It is concluded that the strenuous running program induced locally restricted changes resembling early degeneration of articular cartilage, while simultaneously caused alterations that suggest a general stimulation of proteoglycan metabolism.

Animals↗
PubMed1994

Samarium-153-EDTMP in bone metastases.

Thirty-five patients with painful bone metastases arising from a variety of tumor types underwent a clinical trial in which 153Sm-EDTMP was injected as a single intravenous dose. The injection ranged in amount from 330 MBq to 1110 MBq of 153Sm-EDTMP. Pain relief usually occurred within one week after administration. The duration of pain relief lasted from 2 to 17 weeks. A detectable degree of pain palliation was experienced by 80% of the treated patients; 54% reported substantial or complete pain relief. Due to the small number of patients, no clear-cut dose-related response was detectable. Moderate myelosuppression was observed in one patient (WHO grade III). The metastatic lesion-to-normal bone ratios remained constant (varying from 1.5 to 4.8) for at least 5 days post-injection. 153Sm cleared very rapidly from the blood. Less than 1% of the injected dose remained in circulation at 4 hours post-injection. No local accumulation of the tracer could be detected outside the skeleton. Urinary excretion was quite complete at 6 hours post-injection. The biodistributions of 153Sm-EDTMP and 99mTc-DPD are very similar in metastatic and normal bone; thus, bone scanning can be used for patient selection and followup. According to our results, it seems that higher doses of 153Sm-EDTMP can be given safely and without any irreversible myelosuppression.

Bone Neoplasms↗
PubMed1993

Long-distance running causes site-dependent decrease of cartilage glycosaminoglycan content in the knee joints of beagle dogs.

OBJECTIVE: To study the effects of a long-term (1-year) program of running exercise (up to 40 km/day) on the thickness and glycosaminoglycan (GAG) content of articular cartilage in the knee and humeral head cartilage of young dogs. METHODS: Samples for histologic analysis were obtained from 12 different locations of the joints. We conducted a detailed, area-specific analysis, measuring the thickness of articular cartilage and analyzing the distribution of Safranin O stain that binds stoichiometrically to GAG as determined by quantitative microspectrophotometry. RESULTS: Running exercise decreased the GAG content of the uncalcified articular cartilage in the weight-bearing summits of the femoral condyles by 5-13% (P < 0.05), while at margins of these areas the GAG content was equivalent to control levels. In the lateral condyle of the femur, the reduction was most prominent in the superficial zone (up to 28% decrease; P < 0.05), and extended into the intermediate zone (11% decrease; P < 0.05). GAG content was also significantly reduced in the superficial zone at the lateral condyle of the tibia and the head of the humerus, by 35% (P < 0.01) and 15% (P < 0.05), respectively. Running did not alter GAG concentration in the patellofemoral region. CONCLUSION: The GAG depletion caused by 40-km/day running exercise is restricted to prominent weight-bearing areas of the joint and begins from the superficial cartilage without signs of degeneration. The different degree and type of joint loading can explain the site-dependent cartilage response to long-distance running. The loss of GAGs was possibly due to breakdown of proteoglycans, which could not be compensated for by neosynthesis of molecules. With time, this may affect the condition of articular cartilage, especially if the joint is exposed to loading for lengthy periods.

Animals↗
PubMed1993

Effect of running exercise on proteoglycans and collagen content in the intervertebral disc of young dogs.

Collagen and proteoglycans in the intervertebral disc (LI-II) of young beagle dogs (age 55 weeks) were analyzed following a 15 weeks' daily 20 km running training on a treadmill with 15 degree uphill inclination. In nucleus pulposus no statistically significant alterations were found in the content of proteoglycans or collagen. In annulus fibrosus the total tissue wet weight and total amount of collagen (hydroxyproline) increased by 34-36% in the runners as compared to age-matched, untrained controls. Since the total amount of proteoglycans did not increase, the annulus fibrosus became relatively depleted of proteoglycans, as indicated by the 27% reduction in uronic acid concentration, expressed either per wet weight or hydroxyproline. The average molecular size of the remaining nonaggregating proteoglycans was larger, and there was also a trend towards increased proportion of proteoglycans aggregating with hyaluronan. Most of the chondroitin sulfate side chains were 6-sulfated (65-66%). Running did not alter the sulfation or length of the chondroitin sulfate chains. The decreased proteoglycan/collagen ratio in annulus fibrosus may result in altered mechanical properties of the tissue and reflects its adaptation to enhanced motion and stress.

Animals↗
PubMed1993

Physical performance of the Siemens MultiSPECT 3 gamma camera.

We evaluated physical performance of the new Siemens MultiSPECT 3 gamma camera. The camera is a triple-headed, large detector system dedicated to multislice single photon emission tomographic (SPET) imaging over all the human body. A triangular aperture up to 60 cm in diameter and a patient couch with low gamma-ray attenuation allow all patients to be studied without exception. The patient is easily, quickly and reproducibly positioned. Collimator change is rapidly and semiautomatically performed. Camera tuning, calibration, acquisition and processing are controlled by a MacIntosh Quadra 950 computer. The ICON software is easy to use (a mouse driven system) and the operator does not necessarily need to go through the manuals. The software includes useful reporting and imaging utilities but the version tested by us (vol. 3.0) also has several limitations such as no gated or dynamic SPET, no list-mode acquisition and no body outline attenuation correction. The planar sensitivity using high-resolution collimators (HR) is 380 cps MBq-1 for 99Tcm with a symmetric energy window of 15%. The radial SPET resolution is 8.5 mm full-width half-maximum (FWHM) in scatter with a rotational radius of 12.6 cm (corresponding to the radius of a brain scan) and a tangential resolution of 7.1 mm. The quality of the daily bone, brain and heart scans is superior when compared to those of a conventional single-headed gamma camera. The system allows fast and accurate SPET imaging both for clinical routine practice and for research.

Adult↗
PubMed1992

Analysis of left ventricular function from gated first-pass and multiple gated equilibrium acquisitions.

99mTechnetium-sestamibi is a new myocardial perfusion imaging agent that offers significant physical advantages over 201thallium for myocardial perfusion imaging. One of these advantages is that it can be used in the assessment of ventricular function by means of first-pass radionuclide angiography (FPRNA), acquired during the injection of the tracer. In this study we compared gated list mode first-pass acquisition with 99mTc-sestamibi (FP-MIBI) to multiple gated equilibrium radionuclide ventriculography (MUGA) with 99mTc-labelled red blood cells for the determination of global left ventricular ejection fraction (LVEF). The study population consisted of 20 patients (mean age 54 years) who were submitted to stress-rest perfusion imaging. Resting FPRNA was performed using 99mTc-sestamibi and the reference data were acquired within a week with the MUGA technique. A linear correlation between FP LVEF and MUGA LVEF gave an r = 0.974 (p < 0.01). Diastolic and systolic timing and velocity parameters had lower correlations between these two methods. We conclude that global LVEF can be precisely measured with 99mTc-sestamibi when compared to usually employed MUGA technique with 99mTc-labelled red blood cells.

Cardiac Output↗
PubMed1992

Articular cartilage thickness and glycosaminoglycan distribution in the canine knee joint after strenuous running exercise.

The influences of the strenuous running training program on the knee joint articular cartilage was studied in six female beagle dogs. At the age of 15 weeks, the dogs started running on a treadmill inclined 15 degrees uphill. Thereafter, the dogs were trained for 40 weeks, five times a week. For the final 15 weeks, the dogs ran 20 km/day. Six age-matched female beagles served as controls. The cartilage surfaces were intact after the running exercise. The training reduced the thickness of the uncalcified cartilage by 6% in the medial femoral condyle. The glycosaminoglycan concentration was reduced an average of 11% on the summits of the femoral condyles. The reduction was most pronounced (41%) in the superficial 50-micron cartilage zone. In other regions of the knee, such a decrease of glycosaminoglycans was not observed. A shift to strenuous running voided the increase in cartilage thickness and proteoglycan content previously observed after moderate running. Strenuous running induced marked depletion of proteoglycans from the superficial layer of the femoral condyles at sites subjected to highest impact loads.

Animals↗
PubMed1990

Proteoglycan alterations following immobilization and remobilization in the articular cartilage of young canine knee (stifle) joint.

The distribution of proteoglycans (PGs) at 11 sites on the knee (stifle joint) cartilage of young female beagle dogs was studied following cast immobilization for 11 weeks in 90 degrees flexion and after a subsequent remobilization for 15 weeks. Immobilization induced a reduction in PG uronic acid at all sites (mean of -38%), but the greatest depletion (-64%) occurred at the anterior and posterior extremes of the femoral condyles, i.e., at locations where the immobilized cartilage lost contact to the opposing cartilage. Following remobilization, the content of uronic acid remained lower than in the age-matched controls (-18% on average), particularly at the minimum contact sites most affected by immobilization (-33%). The chondroitin-6-sulfate to chondroitin-4-sulfate ratio was reduced by immobilization in most locations (average of -14%) and returned to control values after remobilization. There was no consistent change in the percentage of aggregating PGs observed in Sephacryl S-1000 gel filtration after immobilization or remobilization. However, following remobilization, the aggregating PGs showed an enhanced proportion of the slower mobility band in agarose gel electrophoresis, indicative of a larger monomer size. In the contralateral, load-bearing knee joint, both the uronic acid content and PG monomer type distribution were identical to those observed in the experimental joint, suggesting that the state reached after the remobilization period was due to factor(s) influencing both sides. The results suggest that contact forces between articulating surfaces are required to maintain normal PG content and that the control mechanism works locally at each cartilage site. Restriction of joint mobility and loading in young animals is concluded to cause persistent changes in cartilage matrix. Furthermore, the use of the contralateral joint as the sole control in this kind of studies, although experimentally convenient, seems not to be appropriate.

Animals↗
PubMed1990

Indentation stiffness of young canine knee articular cartilage--influence of strenuous joint loading.

The indentation stiffness of knee articular cartilage subjected to strenuous physical training (SPT: treadmill running 20 km day-1 for 15 weeks, n = 6) of young Beagles was tested and compared to that obtained from age-matched (55 weeks, n = 9) controls. The mathematical solution for the shear modulus, as determined from indentation of an elastic layer bonded to a rigid half space, was extended to small Poisson's ratios and applied to the analysis of cartilage response after a step stress (0.39 MPa) application. In these measurements with an impervious, plane-ended indenter, the equilibrium deformation was systematically greater than values predicted from the instant response by the linear biphasic theory. Therefore, the accurate determination of Poisson's ratio from the creep curves was not possible. The mean shear modulus (calculated by using the deformation at 900 s after load application and assuming a constant Poisson's ratio of 0.40 for the matrix) of canine knee articular cartilage was 0.37 MPa. While the cartilage thickness was not affected by SPT, the cartilage of the lateral tibial plateau was stiffer (13.3%, p less than 0.05) than that in controls. However, in the femoral condyles, the stiffness was at the control level or even below. Our results on cartilage structure and properties suggest that SPT, in contrast to our previous findings with moderate training, does not necessarily improve the biological properties of articular cartilage in young animals.

Animals↗
PubMed1989

Levels of chondroitin-6-sulfate and nonaggregating proteoglycans at articular cartilage contact sites in the knees of young dogs subjected to moderate running exercise.

The levels and types of proteoglycans in articular cartilage of the knees of young beagle dogs were studied after 15 weeks of running exercise, at 4 km/day. Running increased the levels of proteoglycans in the cartilage of the patella, the superior patellofemoral groove, and the summit of the medial condyle of the femur, all of which are considered contact sites subject to enhanced loading caused by running. The elevated content of uronic acid at the femoral sites proved to be due to proteoglycans that were unable to aggregate with hyaluronic acid. There was no change in the content of aggregating proteoglycans. Analysis of chondroitinase AC-derived disaccharides at the same sites showed an increase in chondroitin-6-sulfate content as compared with chondroitin-4-sulfate levels. We believe that this modulation of the proteoglycan matrix reflects enhanced tissue maturation and physiologic adjustment to higher local contact pressures.

Animals↗
PubMed1989

Partial restoration of immobilization-induced softening of canine articular cartilage after remobilization of the knee (stifle) joint.

The restoration of the biomechanical properties of articular cartilage was studied after 15 weeks of remobilization of the knee joint in beagles previously immobilized with a cast for 11 weeks. The shear moduli were determined with an indentation creep test immediately after load application and at equilibrium at six predefined test points of femoral, tibial, and patellar cartilages. Permeability of the cartilage was estimated from the creep measurements. The values were compared with nontreated, age-matched (55 weeks) controls and with cartilage collected immediately after immobilization. Remobilization reduced the high creep rates created by immobilization and shifted the depressed equilibrium shear moduli towards those of the controls. However, in the femoral condylar cartilage, the equilibrium shear modulus remained at lower level (p less than 0.05) and permeability at higher level (p less than 0.05) as compared with the controls. We conclude that articular cartilage, showing signs of atrophy after long-term immobilization, was capable of restoring its biomechanical properties during remobilization. This repair was not, however, completed in all parts of the knee joint by the end of the observation period.

Animals↗
PubMed1988

Moderate running exercise augments glycosaminoglycans and thickness of articular cartilage in the knee joint of young beagle dogs.

The local influences of physical exercise on thickness and glycosaminoglycan (GAG) content of canine articular cartilage were measured by microspectrophotometry of Safranin O- and periodic acid-Schiff (PAS)-stained tissue sections. Female Beagle dogs were housed in individual cages (bottom 0.9 x 1.2 m) and divided into runner (n = 6) and control (n = 8) groups. The training program started at the age of 15 weeks. During the subsequent 10 weeks, the dogs were accustomed to running on a treadmill inclined 15 degrees uphill. Thereafter, the dogs ran 1 h daily, 5 days a week, at a speed of 4 km/h for 15 weeks. At the age of 40 weeks, the dogs were killed, and the samples for histology were taken from 11 different anatomical locations of the right knee (stifle) joint. The thickness of the uncalcified cartilage increased 19-23% on the lateral condyle and patellar surface of the femur, whereas the enhancement was smaller in other parts of the trained cartilage. The calcified cartilage did not show thickness alterations. Total GAGs were augmented by 28% in the summits on the femoral condyles, more on the medial than lateral side. The increased GAGs appeared to be predominantly chondroitin sulphates and were localized in the intermediate, deep, and even in the calcified zones, whereas the superficial zone did not show changes. There was a concomitant increase of non-GAG oligosaccharides in the intermediate and deep zones, but not in the calcified cartilage.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗