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  • 1.
    Arumugam, Ashokan
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Fysioterapi.
    Markström, Jonas L.
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Fysioterapi.
    Häger, Charlotte K.
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Fysioterapi.
    Introducing a novel test with unanticipated medial/lateral diagonal hops that reliably captures hip and knee kinematics in healthy women2019Ingår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 82, s. 70-79Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Despite a vast literature on one-leg hops and cutting maneuvers assessing knee control pre/post-injury of the anterior cruciate ligament (ACL), comprehensive and reliable tests performed under unpredictable conditions are lacking. This study aimed to: (1) assess the feasibility of an innovative, knee-challenging, one-leg double-hop test consisting of a forward hop followed by a diagonal hop (45°) performed medially (UMDH) or laterally (ULDH) in an unanticipated manner; and (2) determine within- and between-session reliability for 3-dimensional hip and knee kinematics and kinetics of these tests. Twenty-two healthy women (22.3 ± 3.3 years) performed three successful UMDH and ULDH, twice 1–4 weeks apart. Hop success rate was 69–84%. Peak hip and knee angles demonstrated moderate to excellent within-session reliability (intraclass correlation coefficient [ICC] 95% confidence interval [CI]: 0.67–0.99, standard error of measurement [SEM] ≤  3°) and poor to excellent between-session reliability (ICC CI: 0.22–0.94, SEM ≤ 3°) for UMDH and ULDH. The smallest real difference (SRD) was low (≤ 5°) for nearly all peak angles. Peak hip and knee moments demonstrated poor to excellent reliability (ICC CI: 0–0.97) and, in general, moments were more reliable within-session (SEM ≤ 0.14 N.m/kg.m, both directions) than between-session (SRD ≤ 0.43 N.m/kg.m). Our novel test was feasible and, in most but not all cases, provided reliable angle estimates (within-session > between-session, both directions) albeit less reliable moments (within-session > between-session, both directions). The relatively large hip and knee movements in the frontal and transverse planes during the unanticipated hops suggest substantial challenge of dynamic knee control. Thus, the test seems appropriate for evaluating knee function during ACL injury rehabilitation.

  • 2.
    Börlin, Niclas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Thien, Truike
    Katholieke Universiteit Nijmegen, Nijmegen, Holland.
    Kärrholm, Johan
    Sahlgrenska University Hospital, Göteborg, Sweden.
    The precision of radiostereometric measurements: manual vs. digital measurements2002Ingår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 35, nr 1, s. 69-79Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The precision of digital vs. manual radiostereometric measurements in total hip arthroplasty was evaluated using repeated stereoradiographic exposures with an interval of 10–15 min. Ten Lubinus SP2 stems cemented into bone specimens and 12 patients with the same stem design were used to evaluate the precision of stem translations and rotations. The precision of translations and rotations of the cup and femoral head penetration was studied in 12 patients with whole polyethylene cups.

    The use of a measurement method based on digitised radiographs improved the precision for some of the motion parameters, whereas many of them did not change. A corresponding pattern was observed for both the intra- and interobserver error. Of the wear parameters, the most pronounced improvements were the 3D wear and in the proximal-distal direction, although the anterior-posterior precision was also improved. The mean errors of rigid body and elliptic fitting decreased in all evaluations but one, consistent with a more reproducible identification of the markers centres and the edge of the femoral head.

    Increased precision of radiostereometric measurements may be used to increase the statistical power of future randomised studies and to study new fields in orthopaedics requiring higher precision than has been available with RSA based on manual measurements.

  • 3.
    Grip, Helena
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Sjukgymnastik.
    Häger, Charlotte
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering.
    A new approach to measure functional stability of the knee based on changes in knee axis orientation2013Ingår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 46, nr 5, s. 855-862Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    There is a lack of measures that quantify functional knee stability, which is of particular relevance in knee rehabilitation. Therefore, the aim of this study was to investigate the usefulness of knee finite helical axis (FHA) variables in 33 healthy subjects during two different functional tasks; One leg side hop (SH) and Two Leg Squat (TLS), and to investigate correlations of these variables with laxity. Laxity was assessed with a KT-1000 arthrometer and the Beighton Hypermobility Score. Movements were registered with an optical motion capture system. Knee rotation and translation were defined by a six degree of freedom segment model. FHA was calculated for finite steps of 20 degrees knee flexion, based on error simulations. We computed the FHA inclination, the translation along FHA and an FHA Direction Index quantifying directional changes. All variables were repeatable (average ICCs similar to 0.97 during TLS and similar to 0.83 during SH). The lower functional knee stability in SH was reflected by a significantly higher FHA Direction Index and a larger medio-lateral FHA inclination compared to those in TLS. The superior-inferior inclination was smaller during Landing in SH compared to Take-Off and TLS. Translation along FHA was generally small as expected in healthy subjects. Beighton Hypermobility Score and KT-1000 values had weak but significant correlations with FHA Direction Index and FHA translation, which show that laxity influences the functional knee stability. We conclude that FHA measures were sensitive enough to discriminate between SH and TLS. The next step is to investigate the usability of these measures in subjects with knee injury.

  • 4.
    Grip, Helena
    et al.
    Biomedical Engineering & Informatics, University Hospital of Umeå, 90185 Umeå, Sweden.
    Sundelin, Gunnevi
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering.
    Gerdle, Björn
    Department of Rehabilitation Medicine, INR, Faculty of Health Sciences, Linköping, Sweden.
    Karlsson, J Stefan
    Biomedical Engineering & Informatics, University Hospital of Umeå, 90185 Umeå, Sweden.
    Cervical helical axis characteristics and its centre of rotation during active head movements: comparisons of whiplash-associated disorders, non-specific neck pain and asymptomatic individuals2008Ingår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 41, nr 13, s. 2799-2805Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The helical axis model can be used to describe translation and rotation of spine segments. The aim of this study was to investigate the cervical helical axis and its center of rotation during fast head movements (side rotation and flexion/extension) and ball catching in patients with non-specific neck pain or pain due to whiplash injury as compared with matched controls. The aim was also to investigate correlations with neck pain intensity. A finite helical axis model with a time-varying window was used. The intersection point of the axis during different movement conditions was calculated. A repeated-measures ANOVA model was used to investigate the cervical helical axis and its rotation center for consecutive levels of 15° during head movement. Irregularities in axis movement were derived using a zero-crossing approach. In addition, head, arm and upper body range of motion and velocity were observed. A general increase of axis irregularity that correlated to pain intensity was observed in the whiplash group. The rotation center was superiorly displaced in the non-specific neck pain group during side rotation, with the same tendency for the whiplash group. During ball catching, an anterior displacement (and a tendency to an inferior displacement) of the center of rotation and slower and more restricted upper body movements implied a changed movement strategy in neck pain patients, possibly as an attempt to stabilize the cervical spine during head movement.

  • 5.
    Grip, Helena
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Radiofysik.
    Sundelin, Gunnevi
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Sjukgymnastik.
    Gerdle, Björn
    Karlsson, Stefan J
    Umeå universitet, Medicinska fakulteten, Institutionen för strålningsvetenskaper, Radiofysik.
    Cervical helical axis characteristics and its center of rotation during active head and upper arm movements-comparisons of whiplash-associated disorders, non-specific neck pain and asymptomatic individuals.2008Ingår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 41, nr 13, s. 2799-2805Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The helical axis model can be used to describe translation and rotation of spine segments. The aim of this study was to investigate the cervical helical axis and its center of rotation during fast head movements (side rotation and flexion/extension) and ball catching in patients with non-specific neck pain or pain due to whiplash injury as compared with matched controls. The aim was also to investigate correlations with neck pain intensity. A finite helical axis model with a time-varying window was used. The intersection point of the axis during different movement conditions was calculated. A repeated-measures ANOVA model was used to investigate the cervical helical axis and its rotation center for consecutive levels of 15 degrees during head movement. Irregularities in axis movement were derived using a zero-crossing approach. In addition, head, arm and upper body range of motion and velocity were observed. A general increase of axis irregularity that correlated to pain intensity was observed in the whiplash group. The rotation center was superiorly displaced in the non-specific neck pain group during side rotation, with the same tendency for the whiplash group. During ball catching, an anterior displacement (and a tendency to an inferior displacement) of the center of rotation and slower and more restricted upper body movements implied a changed movement strategy in neck pain patients, possibly as an attempt to stabilize the cervical spine during head movement.

  • 6.
    Grip, Helena
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Fysioterapi.
    Tengman, Eva
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Sjukgymnastik.
    Häger, Charlotte
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Sjukgymnastik.
    Dynamic knee stability as estimated by finite helical axis methods during drop landing twenty years after anterior cruciate ligament injury2015Ingår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 48, nr 10, s. 1906-1914Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Finite helical axis (FHA) measures of the knee joint during weight-bearing tasks may capture dynamic knee stability following Anterior Cruciate Ligament (ACL) injury. The aim was to investigate dynamic knee stability during two-leg squat (TLS) and one-leg side hop (SH) in a long-term follow-up of ACL injury, and to examine correlations with knee laxity (KT-1000), osteoarthritis (OA, Kellgren–Lawrence) and knee function (Lysholm score). Participants were injured 17–28 years ago and then treated with surgery (n=33, ACLR) or physiotherapy only (n=37, ACLPT) and healthy-knee controls (n=33) were tested. Movements were registered with an optical motion capture system. We computed three FHA inclination angles, its' Anterior–Posterior (A–P) position, and an index quantifying directional changes (DI), during stepwise knee flexion intervals of ∼15°. Injured knees were less stable compared to healthy controls' and to contralateral non-injured knees, regardless of treatment: the A–P intersection was more anterior (indicating a more anterior positioning of tibia relative to femur) positively correlating with high laxity/low knee function, and during SH, the FHA was more inclined relative to the flexion–extension axis, possibly due to reduced rotational stability. During the TLS, A–P intersection was more anterior in the non-injured knee than the injured, and DI was higher, probably related to higher load on the non-injured knee. ACLR had less anterior A–P intersection than ACLPT, suggesting that surgery enhanced stability, although rotational stability may remain reduced. More anterior A–P intersection and greater inclination between the FHA and the knee flexion–extension axis best revealed reduced dynamic stability ∼23 years post-injury.

  • 7.
    Grip, Helena
    et al.
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Fysioterapi.
    Tengman, Eva
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Fysioterapi.
    Häger, Charlotte K
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Fysioterapi.
    Dynamic knee stability estimated by finite helical axis methods during functional performance approximately twenty years after anterior cruciate ligament injury2015Ingår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 48, nr 10, s. 1906-1914Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Finite helical axis (FHA) measures of the knee joint during weight-bearing tasks may capture dynamic knee stability following Anterior Cruciate Ligament (ACL) injury. The aim was to investigate dynamic knee stability during two-leg squat (TLS) and one-leg side hop (SH) in a long-term follow-up of ACL injury, and to examine correlations with knee laxity (KT-1000), osteoarthritis (OA, Kellgren-Lawrence) and knee function (Lysholm score). Participants were injured 17-28 years ago and then treated with surgery (n=33, ACL(R)) or physiotherapy only (n=37, ACL(PT)) and healthy-knee controls (n=33) were tested. Movements were registered with an optical motion capture system. We computed three FHA inclination angles, its' Anterior-Posterior (A-P) position, and an index quantifying directional changes (DI), during stepwise knee flexion intervals of similar to 15 degrees. Injured knees were less stable compared to healthy controls' and to contralateral non-injured knees, regardless of treatment: the A-P intersection was more anterior (indicating a more anterior positioning of tibia relative to femur) positively correlating with high laxity/low knee function, and during SH, the FHA was more inclined relative to the flexion-extension axis, possibly due to reduced rotational stability. During the TLS, A-P intersection was more anterior in the non-injured knee than the injured, and DI was higher, probably related to higher load on the non-injured knee. ACL(R) had less anterior A-P intersection than ACL(PT), suggesting that surgery enhanced stability, although rotational stability may remain reduced. More anterior A-P intersection and greater inclination between the FHA and the knee flexion-extension axis best revealed reduced dynamic stability similar to 23 years post-injury.

  • 8. Hodges, Paul W
    et al.
    Eriksson, A E Martin
    Umeå universitet, Medicinska fakulteten, Institutionen för samhällsmedicin och rehabilitering, Fysioterapi.
    Shirley, Debra
    Gandevia, Simon C
    Intra-abdominal pressure increases stiffness of the lumbar spine2005Ingår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 38, nr 9, s. 1873-1880Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Intra-abdominal pressure (IAP) increases during many tasks and has been argued to increase stability and stiffness of the spine. Although several studies have shown a relationship between the IAP increase and spinal stability, it has been impossible to determine whether this augmentation of mechanical support for the spine is due to the increase in IAP or the abdominal muscle activity which contributes to it. The present study determined whether spinal stiffness increased when IAP increased without concurrent activity of the abdominal and back extensor muscles. A sustained increase in IAP was evoked by tetanic stimulation of the phrenic nerves either. unilaterally or bilaterally at 20 Hz (for 5 s) via percutaneous electrodes in three subjects. Spinal stiffness was measured as the force required to displace an indentor over the L4 or L2 spinous process with the subjects lying prone. Stiffness was measured as the slope of the regression line fitted to the linear region of the force-displacement curve. Tetanic stimulation of the diaphragm increased IAP by 27-61% of a maximal voluntary pressure increase and increased the stiffness of the spine by 8-31% of resting levels. The increase in spinal stiffness was positively correlated with the size of the IAP increase. IAP increased stiffness at L2 and L4 level. The results of this:study provide evidence that the stiffness of the lumbar spine is increased when IAP is elevated.

  • 9.
    Julkunen, Petro
    et al.
    Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland; Department of Clinical Neurophysiology, Kuopio University Hospital, Kuopio, Finland.
    Wilson, Wouter
    Department of Biomedical Engineering, Eindhoven University of Technology, Eindhoven, The Netherlands.
    Jurvelin, Jukka
    Department of Physics, University of Kuopio, Kuopio, Finland; Department of Clinical Physiology and Nuclear Medicine, Kuopio University Hospital, Kuopio, Finland.
    Rieppo, Jarno
    Department of Biomedicine, Anatomy, University of Kuopio, Kuopio, FinlandDepartment of Biomedicine, Anatomy, University of Kuopio, Kuopio, Finland.
    Qu, Cheng-Juan
    Department of Biomedicine, Anatomy, University of Kuopio, Kuopio, Finland.
    Lammi, Mikko
    Department of Biosciences, Applied Biotechnology, University of Kuopio, Kuopio, Finland.
    Korhonen, Rami
    Department of Physics, University of Kuopio, Kuopio, Finland; Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, Alberta, Canada.
    Stress-relaxation of human patellar articular cartilage in unconfined compression: prediction of mechanical response by tissue composition and structure.2008Ingår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 41, nr 9, s. 1978-86, artikel-id 18490021Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 10.
    Parkkinen, Jyrki
    et al.
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Lammi, Mikko
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Karjalainen, Seppo
    Department of Instrumentation, University of Kuopio, Kuopio, Finland.
    Laakkonen, Jukka
    Department of Instrumentation, University of Kuopio, Kuopio, Finland.
    Hyvärinen, Erkki
    Department of Instrumentation, University of Kuopio, Kuopio, Finland.
    Tiihonen, Aimo
    Department of Instrumentation, University of Kuopio, Kuopio, Finland.
    Helminen, Heikki
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    Tammi, Markku
    Department of Anatomy, University of Kuopio, Kuopio, Finland.
    A mechanical apparatus with microprcessor controlled stress profile for cyclic compression of cultured articular cartilage explants1989Ingår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 22, nr 11-12, s. 1285-1291Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An apparatus was designed for mechanical compression of cultured articular cartilage explants with a cylindrical plain-ended loading head (diameter 2–5 mm) driven by a stepping motor. A load cell under the culture dish was applied for feedback regulation utilizing a microprocessor-based control unit. The operating programs allowed either continuous or cyclic loading, the latter with adjustable loading/resting ratio. The improvements in the present design compared with previously described apparatuses for similar purposes include: (1) the accurately controlled compression by a load cell and a rapid feedback circuit; (2) the wide range of selectable stresses (25 kPa–12.5 MPa) with both continuous and cyclic loading modes; (3) the ability to handle cycles as short as 1 s with 15 ms peak loading phase. Using a 4s cycle and 0.5 MPa load for 1.5 h resulted in a significantly enhanced incorporation of radiosulphate in cultured bovine articular cartilage explants, suggesting a stimulation of proteoglycan synthesis. Light and scanning electron microscopic examinations revealed a slight depression and superficial alterations in cartilage structure at the impact site following high pressures. We expect that this apparatus will help in revealing how articular cartilage tissue and chondrocytes respond to external mechanical stimuli.

  • 11.
    Pontén, Eva
    et al.
    Umeå universitet, Medicinsk fakultet, Integrativ medicinsk biologi, Anatomi.
    Fridén, Jan
    Immobilization of the rabbit tibialis anterior muscle in a lengthened position causes addition of sarcomeres in series and extra-cellular matrix proliferation.2008Ingår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 41, nr 8, s. 1801-4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Rabbits were immobilized for 3 weeks with the ankle in plantar flexion, midrange position or dorsal extension (n=15). The left leg was used as control. Sarcomere lengths were measured by laser diffraction in vivo in the tibialis anterior (TA) muscle. Legs immobilized in the midrange position showed coherent diffraction patterns through the range of motion, but in those immobilized with TA in the stretched position no diffraction patterns in vivo could be obtained. Morphological analyses revealed increased fibrosis and occurrence of whorled fibers in these muscles. On 15 more likewise immobilized rabbits, a technique of measuring sarcomere lengths in vitro by first digesting the collagen in nitric acid was developed. These in vitro measurements showed shorter sarcomeres in the muscles immobilized in a lengthened position compared to the control, indicating an addition of sarcomeres in series.

  • 12.
    Söderkvist, Inge
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Wedin, Per-Åke
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för datavetenskap.
    Determining the movements of the skeleton using well-configured markers1993Ingår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 26, nr 12, s. 1473-1477Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The problem of determining skeletal movements in three dimensions by using a number of landmarks is treated. We present a method that determines the motion of a rigid body by using the positions of the landmarks in least-squares sense. The method uses the singular value decomposition of a matrix derived from the positions of the landmarks. We show how one can use this method to express movement of skeleton segments relative to each other. As many others have pointed out, the movement can be very ill determined if the landmarks are badly configured. We present a condition number for the problem with good geometrical properties. The condition number depends on the configuration of the landmarks and indicates how to distribute the landmarks in a suitable way.

  • 13.
    Turunen, Mikael
    et al.
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland; Department of Clinical Physiology, Kuopio University Hospital, Kuopio, Finland.
    Töyräs, Juha
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland; Department of Clinical Physiology, Kuopio University Hospital, Kuopio, Finland.
    Lammi, Mikko
    Department of Biosciences, University of Eastern Finland, Kuopio, Finland; Biocenter Kuopio, University of Eastern Finland, Kuopio, Finland.
    Jurvelin, Jukka
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
    Korhonen, Rami
    Department of Applied Physics, University of Eastern Finland, Kuopio, Finland.
    Hyperosmolaric contrast agents in cartilage tomography may expose cartilage to overload-induced cell death.2012Ingår i: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 45, nr 3, s. 497-503, artikel-id 22206829Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In clinical arthrographic examination, strong hypertonic contrast agents are injected directly into the joint space. This may reduce the stiffness of articular cartilage, which is further hypothesized to lead to overload-induced cell death. We investigated the cell death in articular cartilage while the tissue was compressed in situ in physiological saline solution and in full strength hypertonic X-ray contrast agent Hexabrix(TM). Samples were prepared from bovine patellae and stored in Dulbecco's Modified Eagle's Medium overnight. Further, impact tests with or without creep were conducted for the samples with contact stresses and creep times changing from 1 MPa to 10 MPa and from 0 min to 15 min, respectively. Finally, depth-dependent cell viability was assessed with a confocal microscope. In order to characterize changes in the biomechanical properties of cartilage as a result of the use of Hexabrix™, stress-relaxation tests were conducted for the samples immersed in Hexabrix™ and phosphate buffered saline (PBS). Both dynamic and equilibrium modulus of the samples immersed in Hexabrix™ were significantly (p<0.05) lower than those of the samples immersed in PBS. Cartilage samples immersed in physiological saline solution showed load-induced cell death primarily in the superficial and middle zones. However, under high 8-10 MPa contact stresses, the samples immersed in full strength Hexabrix™ showed significantly (p<0.05) higher number of dead cells than the samples compressed in physiological saline, especially in the deep zone of cartilage. In conclusion, excessive loading stresses followed by tissue creep might increase the risk for chondrocyte death in articular cartilage when immersed in hypertonic X-ray contrast agent, especially in the deep zone of cartilage.

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