Journal of Orthopaedic Research
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Internal deformations of intact and denucleated human lumbar discs subjected to compression, flexion, and extension loads Abstract Three rows of six evenly spaced 0.5 mm metal beads were implanted midsagittally into the discs of ten L4–5 human lumbar motion segments. The intradiscal bead displacements in response to compression, flexion, and extension loads were obtained by digitizing the bead positions from sagittal plane radiographs taken before and during the load application. Each disc was denucleated and the loading process was repeated. For the intact discs, in compression, the intradiscal bead displacements were predominantly anterior. In flexion, the beads in the center of the disc moved posteriorly whereas the beads closer to the periphery of the disc moved anteriorly. In extension, the central beads moved anteriorly and the beads closer to the periphery of the disc moved posteriorly. After denucleation, the bead displacements for compression and flexion implied an inward bulging of the inner wall of the annulus, despite outward bulging of the disc surface. We hypothesize that the inward bulging causes radial tensile stresses within the disc, leading to disruption of adjacent layers of annulus.
Journal of Orthopaedic Research - Tập 7 Số 1 - Trang 122-131 - 1989
Shear mechanical properties of human lumbar annulus fibrosus Abstract Function, failure, and remodeling of the intervertebral disc are all related to the stress and strain fields in the tissue and may be calculatd by finite element models with accurate material properties, realistic geometry, and appropriate boundary conditions. There is no comprehensive study in the literature investigating the shear material properties of the annulus fibrosus. This study obtained shear material properties of the annulus fibrosus and tested the hypothesis that these properties are affected by the amplitude and frequency of shearing, applied compressive stress, and degenerative state of the tissue. Cylindrical specimens with an axial orientation from seven nondegenerated and six degenerated discs were tested in torsional shear under dynamic and static conditions. Frequency sweep experiments over a physiological range of frequencies (0.1‐100 rad/sec) at a shear strain amplitude of 0.05 rad were performed under three different axial compressive stresses (17.5, 25, and 35 kPa). At the largest compressive stress, shear strain sweep experiments (strain amplitude range: 0.005‐0.15 rad at a frequency of 5 rad/sec) and transient stress‐relaxation tests (shear strain range: 0.02‐0.15 rad) were performed. The annulus fibrosus material was less stiff and more dissipative at larger shear strain amplitudes, stiffer at higher frequencies of oscillation, and stiffer and less dissipative at larger axial compressive stresses. The dynamic shear modulus, |G*|, had values ranging from 100 to 400 kPa, depending on the experimental condition and degenerative level. The shear behavior was also predominantly elastic, with values for the tangent of the phase angle (tanδ) ranging from 0.1 to 0.7. The annulus material also became stiffer and more dissipative with degenerative grade; however, this was not statistically significant. The results indicated that nonlinearities, compression/shear coupling, intrinsic viscoelasticity, and, to a lesser degree, degeneration all affect the shear material behavior of the annulus fibrosus, with important implications for load‐carriage mechanisms in the intervertebral disc. These material complexities should be considered when choosing material constants for finite element models.
Journal of Orthopaedic Research - Tập 17 Số 5 - Trang 732-737 - 1999
Radial tensile properties of the lumbar annulus fibrosus are site and degeneration dependent Abstract We conducted an in vitro study of the radial tensile properties of the annulus fibrosus. The stress‐strain response was nonlinear, with a mean tangent modulus of 0.19 MPa at zero strain and 0.47 MPa at 70% of the yield strain. We also investigated whether these properties varied as a function of location within the disc and degree of degeneration. Specimens harvested from the middle layers of the annulus were stiffer and failed at smaller strain magnitudes than those from the inner or outer annulus (analysis of covariance, p <0.05). Differences due to degeneration were evident; degenerated discs had a 30% decrease in yield and ultimate stress compared with normal discs. Similarity between our data and those reported for the annulus in compression suggests that these values reflect the material behavior of the interlaminar matrix and are an order of magnitude smaller than values used in previous analytical representations of this tissue. We expect that awareness of these data will result in improved understanding of the physical behavior and tolerance to injury of the annulus fibrosus.
Journal of Orthopaedic Research - Tập 15 Số 6 - Trang 814-819 - 1997
Repeatability of kinematic, kinetic, and electromyographic data in normal adult gait Abstract The repeatability of gait variables is an important consideration in the clinical use of results of quantitative gait analysis. Statistical measures were used to evaluate repeatability of kinematic, kinetic, and electromyographic data waveforms and spatiotemporal parameters of 40 normal subjects. Subjects were evaluated three times on each test day and on three different test days while walking at their preferred or natural speed. Intrasubject repeatability was excellent for kinematic data in the sagittal plane both within a test day as well as between test days. For joint angle motion in the frontal and transverse planes, the repeatability was good within a test day and poor between test days. Poor between‐day repeatability of joint angle motion in the frontal and transverse planes was noted to be partly due to variabilities in the alignment of markers. Vertical reaction and fore–aft shear forces were more repeatable than the mediolateral shear force. Sagittal plane joint moments were more repeatable than frontal or transverse plane moments. For electromyographic data, repeatability within a day was slightly better than between test days. In general, the results demonstrate that with the subjects walking at their natural or preferred spped, the gait variables are quite repeatable. These observations suggest that it may be reasonable to base significant clinical decisions on the results of a single gait evaluation.
Journal of Orthopaedic Research - Tập 7 Số 6 - Trang 849-860 - 1989
Kinematics of the trapeziometacarpal joint after sectioning of ligaments Abstract This study was designed to examine the roles of ligaments in the maintenance of the articular kinematics of the trapeziometacarpal joint. Circumduction of the trapeziometacarpal joint was studied in 12 hands from fresh human cadavera. With use of a magnetic tracking system, changes in the motion of the base of the first metacarpal after ligament sectioning were analyzed and compared with those of the normal joint. Two sets of ligaments were sectioned: (a) the anterior oblique and ulnar collateral ligaments and (b) the first intermetacarpal ligament and the ulnar joint capsule. Sectioning of the anterior oblique and ulnar collateral ligaments resulted in a significant dorsal‐ulnar shift in the path of the base of the first metacarpal. However, sectioning of the first intermetacarpal ligament did not affect the movement pattern of the center of the base. The anterior oblique and ulnar collateral ligaments provided constraint of the trapeziometacarpal joint during circumduction of the thumb.
Journal of Orthopaedic Research - Tập 12 Số 2 - Trang 205-210 - 1994
Kinematics of the normal trapeziometacarpal joint Abstract Motion of the trapeziometacarpal joint was studied in 12 hands from fresh human cadavera. By use of a magnetic tracking system, a full range of motion of the first metacarpal was analyzed with respect to a defined trapezial coordinate system. The traces of the reference points on the head and base of the first metacarpal were monitored, and the instantaneous centers of rotation were calculated. During circumduction, the reference points on the head and base followed elliptical paths but in opposite directions. The average instantaneous center of circumduction was at approximately the center of the trapezial joint surface. In flexion‐extension, the axis of rotation was located within the trapezium, and the path of the head was identical to the path of the base. In abduction‐adduction, the axis of rotation was located distal to the trapezium within the base of the first metacarpal, and the base and head moved in opposite directions. There was no single center of rotation: rather, instantaneous motion occurred reciprocally between these centers of rotation within the trapezium and metacarpal base in the normal thumb. This changing instantaneous center of rotation results in a unique pattern of motion which is related to congruent, tightly constrained joint surfaces of two reciprocal saddle joints and to precisely positioned extraarticular ligaments.
Journal of Orthopaedic Research - Tập 12 Số 2 - Trang 197-204 - 1994
Contact areas in the thumb carpometacarpal joint Abstract The thumb carpometacarpal joint is a common site of osteoarthritis. It has been hypothesized that peaks of localized stress on the dorsoradial or volar‐ulnar regions, or both, of the articular surfaces of the trapezium and metacarpal lead to erosion of cartilage and may be responsible for the progression of the disease. The objective of this study was to determine the contact areas in this joint under the functional position of lateral (key) pinch and in the extremes of range of motion of the joint. These contact areas were assessed relative to the observed sites of cartilage thinning. Eight hands from cadavers of women and five from cadavers of men were tested in vitro with the thumb under a 25 N load in the lateral pinch position, and under small muscle loads (0–5 N) with the thumb in flexion, extension, abduction, adduction, and neutral positions. Contact areas of articular surfaces of the thumb carpometacarpal joint were determined for these positions using a stereophotogrammetric technique. The lateral pinch position produced contact areas predominantly on the central, volar, and volar‐ulnar regions of the trapezium and the metacarpal. In three specimens, contact areas were distinctly separated between the dorsoradial and volar‐ulnar regions, and in one specimen, from a man, contact occurred exclusively on the dorsoradial region of the trapezium. Using stereophotogrammetry, maps of cartilage thickness also were determined for a subset of nine specimens. The volar‐ulnar, ulnar, and dorsoradial regions of the trapezium were the most common sites of thin cartilage, and these may be sites of cartilage wear. The results of this study indicate that the lateral pinch position produced stresses in the same regions where cartilage thinning was observed; this lends support to the hypothesis that high stresses can lead to osteoarthritis in this joint.
Journal of Orthopaedic Research - Tập 13 Số 3 - Trang 450-458 - 1995
Cell death after cartilage impact occurs around matrix cracks Abstract The damage from rapid high energy impacts to cartilage may contribute to the development of osteoarthritis (OA). Understanding how and when cells are damaged during and after the impact may provide insight into how these lesions progress. Mature bovine articular cartilage on the intact patella was impacted with a flat impacter to 53 MPa in 250 ms. Cell viability was determined by culturing the cartilage with nitroblue tetrazolium for 18 h or for 4 days in medium containing 5% serum before labeling (5‐day sample) and compared to adjacent, non‐impacted tissue as viable cells per area. There was a decrease in viable cell density only in specimens with macroscopic cracks and the loss was localized primarily near matrix cracks, which were in the upper 25% of the tissue. This was confirmed using confocal microscopy with a fluorescent live/dead assay, using 5′‐chloromethylfluorescein diacetate and propidium iodide. Cell viability in the impacted regions distant from visible cracks was no different than the non‐impacted control. At 5 days, viable cell density decreased in the surface layer in both the control and impacted tissue, but there was no additional impact‐related change. In summary, cell death after the impaction of cartilage on bone occurred around impact induced cracks, but not in impacted areas without cracks. If true in vivo, early stabilization of the damaged area may prevent late sequelae that lead to OA. © 2003 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.
Journal of Orthopaedic Research - Tập 21 - Trang 881-887 - 2003
PPARγ is involved in the hyperglycemia‐induced inflammatory responses and collagen degradation in human chondrocytes and diabetic mouse cartilages ABSTRACT Diabetic hyperglycemia has been suggested to play a role in osteoarthritis. Peroxisome proliferator‐activated receptor‐γ (PPARγ) was implicated in several pathological conditions including diabetes and inflammation. The detailed effects and mechanisms of hyperglycemia on cartilage damage still need to be clarified. Here, we investigated the role of PPARγ in hyperglycemia‐triggered chondrocyte/cartilage damages using a human chondrocyte culture model and a diabetic mouse model. Human chondrocytes were cultured and treated with high concentration of glucose (30 mM) to mimic hyperglycemia in the presence or absence of pioglitazone, a PPARγ agonist. Streptozotocin (STZ) was used to induce mouse diabetes. Our data showed that high glucose induced the protein expressions of cyclooxygenase‐2 (COX‐2) and production of prostaglandin‐E2 (PGE2 ), interleukin‐6 (IL‐6), and metalloproteinase‐13 (MMP‐13), but decreased the protein expression of collagen II and PPARγ in human chondrocytes. These alterations in high glucose‐treated human chondrocytes could be reversed by pioglitazone in a dose‐dependent manner. Moreover, pioglitazone administration could also significantly reverse the hyperglycemia, formation of AGEs, productions of IL‐6 and MMP‐13, and cartilage damage in STZ‐induced diabetic mice. Taken together, these findings suggest that hyperglycemia down‐regulates PPARγ expression and induces inflammatory and catabolic responses in human chondrocytes and diabetic mouse cartilages. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 33:???–???, 2015.
Journal of Orthopaedic Research - Tập 33 Số 3 - Trang 373-381 - 2015
In vivo kinematics of mobile‐bearing knee arthroplasty in deep knee bending motion Abstract The current study aimed to analyze kinematics during deep knee bending motion by subjects with fully congruent mobile‐bearing total knee arthroplasties allowing axial rotation and anteroposterior (AP) gliding. Twelve subjects were implanted with Dual Bearing Knee prostheses (DBK, slot type: Finsbury Orthopaedics, Surrey, UK). These implants include a mobile‐bearing insert that is fully congruent with the femoral component throughout flexion and allows axial rotation and limited AP translation. Sequential fluoroscopic images were taken in the sagittal plane during loaded knee bending motion. In vivo kinematics were analyzed using a two‐ to three‐dimensional registration technique, which uses computer‐assisted design models to reproduce the spatial position of femoral and tibial components from single‐view fluoroscopic images. The average femoral component demonstrated 13.4° external axial rotation for 0–120° flexion. On average, the medial condyle moved anteriorly 6.2 mm for 0–100° flexion, then posteriorly 4.0 mm for 100–120° flexion. On average, the lateral condyle moved anteriorly 1.0 mm for 0–40° flexion, then posteriorly 8.7 mm for 40–120° flexion. The typical subject exhibited a lateral pivot pattern from extension to 60° flexion and a central pivot pattern from 60° to 100° flexion, patterns that are not usually observed in normal knees. Subsequently from 100° to 120° flexion, a rollback pattern was reproduced in which bilateral condyles moved backward. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
Journal of Orthopaedic Research - Tập 22 Số 5 - Trang 1044-1049 - 2004
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