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  • 1
    Electronic Resource
    Electronic Resource
    The influence of geometry on the stress distribution in joints — a finite element analysis (1994)
    Springer
    Anatomy and embryology 189 (1994), S. 545-552 
    Details
    ISSN: 1432-0568
    Keywords: Incongruity ; Joint loading ; Load distribution ; Finite element method ; Joint geometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The incongruity of human joints is a phenomenon which has long been recognized, and recent CT-osteoabsorptiometric findings suggest that this incongruity influences the distribution of stress in joints during their normal physiological use. The finite element method (FEM) was therefore applied to five different geometric configurations consistent with the anatomy of articular surfaces, and a program with variable contact areas (Marc) was used to calculate the stress distribution for loads of 100 to 6 900 N. The assumption of congruity between head and socket results in a “bell-shaped” distribution of stress with a maximum value of 61.5 N/mm2 in the depths of the socket, decreasing towards zero at its edges. In the model with a flatter socket the von Mises stresses are higher (max. 101.3 N/mm2); with a deeper socket, lower (max. 53.0 N/mm2). If the diameter of the head is greater, the stresses build up from the periphery of the socket and move towards its depths as the load increases. The combination of an oversized head and a deeper socket results in the most satisfactory stress distribution (max. 43.2 N/mm2). These results extend previous photoelastic findings with incongruous joint surfaces. The calculated mechanical conditions show a relationship to the location of osteoarthritic changes, and are reflected by the distribution pattern of subchondral bone density. A more satisfactory stress distribution is found with functionally advantageous, incongruous joint surfaces (oversized head and deepened socket) than in the congruous joint, and a better nutritive situation for the articular cartilage seems likely. The geometry of the joint is therefore a physiologically important and quantifiable factor contributing to an optimized transmission of forces in joints.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00186828
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  • 2
    Electronic Resource
    Electronic Resource
    Direct comparison of contact areas, contact stress and subchondral mineralization in human hip joint specimens (1997)
    Springer
    Anatomy and embryology 195 (1997), S. 279-288 
    Details
    ISSN: 1432-0568
    Keywords: Key words Pelvis ; Load transfer ; Subchondral bone ; Functional adaptation ; Osteoarthrosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  X-ray densitometric and CT osteoabsorptiometric findings suggest that in the human hip subchondral mineralization patterns change from bicentric to monocentric as a function of age. It has been hypothesized that these changes indicate an alteration in the geometric configuration of the joint from incongruous to congruous, possibly associated with the onset of osteoarthrosis. The purpose of this study was therefore to directly compare contact areas, contact stress and subchondral mineralization in the hip joint. Twelve specimens without cartilage lesions (ages 34–86 years) were investigated. Simulating the mid-stance phase, the contact areas were determined by polyether casting and the contact stress with Fuji film. The distribution of subchondral mineralization was assessed non-invasively with CT osteoabsorptiometry. At small loads the load-bearing areas were located at the periphery of the lunate surface. In some joints they were found in the acetabular roof and expanded, with higher loads, to the center of the lunate surface and the anterior and posterior horns. In other joints, the contact areas were recorded at lower loads in the anterior and posterior horns, and only at higher forces they merged in the acetabular roof. The maximal contact stress ranged from 8 to 9 MPa at 300% body weight. Maxima of subchondral mineralization were recorded in the acetabular roof, in the anterior and posterior horns, or in all three locations. There was no clear correlation between the distribution of contact and pressure, and the pattern of subchondral bone density. Incongruity is shown to strongly affect the distribution of contact and pressure in the human hip joint. However, the pattern of subchondral mineralization cannot be readily explained in terms of the contact areas and contact stress during mid-stance. Incongruity may give rise to tensile stresses in the subchondral bone, and the construction of the pelvis as a whole may play an important role in subchondral bone loads and adaptation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004290050047
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  • 3
    Electronic Resource
    Electronic Resource
    Physiological incongruity of the humero-ulnar joint: a functional principle of optimized stress distribution acting upon articulating surfaces? (1993)
    Springer
    Anatomy and embryology 188 (1993), S. 449-455 
    Details
    ISSN: 1432-0568
    Keywords: Incongruity ; Humero-ulnar joint ; Elbow-joint physiology ; Stress distribution ; Joint loading
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Investigations into the distribution of subchondral bone density in the human elbow have suggested that the geometry of the trochlear notch deviates from a perfect fit with the trochlea, and that the load is transmitted ventrally and dorsally rather than through the centre of the humero-ulnar joint. We therefore decided to make a quantitative assessment of the degree of incongruity between the two components in 15 human specimens (age distribution 60 to 93 years) with different types of joint surface. Polyether casts of the joint cavity were prepared under loads of 10,40,160 and 640 N. The thickness of the casts was then measured at 50 predetermined points, and an area distribution of the width of the joint space represented in a two-dimensional template of the trochlear notch. The reproducibility of this procedure was tested by image analysis. At a load of 10 N, only a narrow space was present ventrally and dorsally in the joint, but in the depths of the trochlear notch a width of 0.5 to 1 mm was recorded in the centre, and up to 3 mm at its medial and lateral edges. Specimens with continuous articular cartilage showed a lower degree of incongruity than those with a divided articular surface. As the load was increased to 640 N, however, the original incongruity between the articular surfaces disappeared almost completely. The joint surfaces became more congruous, probably because of the viscoelastic properties of the articular cartilage and the subchondral bone, and the contact areas merged in the centre of the joint. It is suggested that this physiological incongruity brings about an optimal distribution of stress over the articular surface during the transmission of the load, and it may lead to better nourishment of the articular cartilage by providing intermittent mechanical stimulation and circulation of the synovial fluid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00190139
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  • 4
    Electronic Resource
    Electronic Resource
    Quantitative relationships of normal cartilage volumes of the human knee joint – assessment by magnetic resonance imaging (1998)
    Springer
    Anatomy and embryology 197 (1998), S. 383-390 
    Details
    ISSN: 1432-0568
    Keywords: Key words Cartilage ; MR imaging ; Knee joint ; Three-dimensional reconstruction ; Osteoarthritis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The objective of this study was to assess the normal range of cartilage volumes in the knee joints of healthy adults, the ratio between the patellar, femoral, and tibial cartilages, and the correlation of the volumes with age, body weight, height, body mass index (obesity), patellar bone size, and the diameter of the tibial head. We examined the knee joints of nine healthy volunteers and eleven normal post-mortem specimens with an age range of 24 to 82 years. The cartilage volumes of the patella, femur, medial tibia and the lateral tibia were quantified, using a fat-suppressed FLASH-3D sequence (resolution 2×0.31×0.31 mm3) and digital postprocessing, involving three-dimensional reconstruction. The mean total volume of the knee joint cartilage was 23,245 mm3, the relative standard deviation (CV%) 19%, and the range 16,341 to 33,988 mm3. In the patella, femur and tibia, the CV% amounted to between 22 and 25%. These joint surfaces occupied a relatively variable proportion of the total knee joint volume, the percentage of the patella being 11 to 22%, that of the femur 54 to 69%, that of the medial tibia 7 to 12%, and that of lateral tibia 11 to 16%. The volumes of the lateral tibia were systematically higher than those of the medial tibia (P〈0.001). There was no significant correlation of the knee joint cartilage volume with age (r=+0.05), body weight (r=+0.38), height (r=+0.39) or body mass index (r=+0.29), but a relatively high correlation with the diameter of the tibial head (r=+0.78, P〈0.001). After normalising the volumes to this diameter, the CV% of the total knee joint cartilge volume was reduced to 13%, its variation being 12 to 21% in the patella, femur and tibia. MRI is available for measuring cartilage volume during growth, functional adaptation, and tissue loss in degenerative joint disease. The study shows that a wide variation of cartilage volumes exists in the knee joints of normal adults. To reduce the variability between individuals, the cartilage volumes may be normalised to the head of the tibial diameter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004290050149
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  • 5
    Electronic Resource
    Electronic Resource
    Tension and bending, but not compression alone determine the functional adaptation of subchondral bone in incongruous joints (1999)
    Springer
    Anatomy and embryology 199 (1999), S. 85-97 
    Details
    ISSN: 1432-0568
    Keywords: Key words Joint mechanics ; Elbow joint ; Finite element model ; Trabecular architecure ; Split lines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In the present study, we tested the hypothesis that tension and bending, rather than compression alone, determine the functional adaptation of subchondral bone in incongruous joints. We investigated whether tensile stresses in the subchondral bone of the humero-ulnar articulation are affected by the direction of muscle and joint forces, and whether the tensile stresses are large enough to cause microstructural adaptation, specifically a preferential alignment of the trabeculae and the subchondral collagen fibres. Using a previously validated finite element model of the human humero-ulnar joint, we calculated the contact pressure, the principal compressive and tensile stresses, and the strain energy density in the subchondral bone for various flexion angles. A bicentric (ventro-dorsal) pressure distribution was found in the joint at 30° to 120° of flexion, with contact pressures of up to between 2.5 and 3 MPa in the ventral and dorsal aspects of the ulnar joint surface, but less than 0.5 MPa in the centre. The principal tensile stress in the subchondral bone of the trochlear notch quantitatively exceeded the principal compressive stress at low flexion angles (maximum 8.2 MPa), and the distribution of subchondral strain energy density differed substantially from that of the contact stress (r=–0.72 at 30° and r=+0.58 at 90° of flexion). No important tensile stress was computed in the trochlea humeri. On contact radiography, we found sagittally orientated subarticular trabeculae in the notch, running tangential to the surface. Furthermore, we observed sagittally orientated split lines in the subchondral bone of the notch of 20 cadaver joints, suggesting a ventro-dorsal orientation of the collagen fibres. The trochlea humeri, on the other hand, did not show a preferential direction of the subchondral split lines, these findings confirming the predictions of tensile stresses in the model. We conclude that, due to the important contribution of tension to subchondral bone stress, the distribution of subchondral density cannot be directly employed for assessing the long term distribution of joint pressure at the cartilage surface. The magnitude of the tensional stress varies considerably with the direction of the muscle and joint forces, and it appears large enough to cause functional adaptation of the subchondral bone on a microstructural level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004290050212
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  • 6
    Electronic Resource
    Electronic Resource
    Computed tomography-osteoabsorptiometry for assessing the density distribution of subchondral bone as a measure of long-term mechanical adaptation in individual joints (1989)
    Springer
    Skeletal radiology 18 (1989), S. 507-512 
    Details
    ISSN: 1432-2161
    Keywords: Computed tomography-osteoabsorptiometry ; Subchondral bone density ; Biomechanics ; Functional adaptation ; X-ray densitometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To estimate subchondral mineralisation patterns which represent the long-term loading history of individual joints, a method has been developed employing computed tomography (CT) which permits repeated examination of living joints. The method was tested on 5 knee, 3 sacroiliac, 3 ankle and 5 shoulder joints and then investigated with X-ray densitometry. A CT absorptiometric presentation and maps of the area distribution of the subchondral bone density areas were derived using an image analyser. Comparison of the results from both X-ray densitometry and CT-absorptiometry revealed almost identical pictures of distribution of the subchondral bone density. The method may be used to examine subchondral mineralisation as a measure of the mechanical adaptability of joints in the living subject.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351749
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  • 7
    Electronic Resource
    Electronic Resource
    Morphomechanics of the humero-ulnar joint: I. Joint space width and contact areas as a function of load and flexion angle (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 243 (1995), S. 318-326 
    Details
    ISSN: 0003-276X
    Keywords: Elbow ; Humero-ulnar joint ; Incongruity ; Joint loading ; Joint space ; Contact areas ; Load transmission ; Numerical methods ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Background: Previous studies have shown that the trochlear notch is deeper than necessary for an exact fit with the humerus. However, humero-ulnar joint space width and contact areas have so far not been quantified for variations in the load and angle of flexion.Methods: Six fresh cadaveric specimens were investigated at 30°, 60°, 90°, and 120° of flexion and at loads of 25 and 500 N, simulating resisted elbow extension. The joint space width and contact were determined, using polyether casting material.Results: At 25 N all joints made contact in the ventral and dorsal aspects of the articular surfaces, whereas in the depth of the trochlear notch the joint space was on average between 0.3 and 2.8 mm wide, with some variation between individuals. At 500 N the joint space width was considerably reduced and the contact areas expanded towards the depth of the notch. The size of the dorsal contact areas was significantly smaller at 30° and that of the ventral ones at 120°, their ventro-dorsal ratio decreasing considerably from 30° to 120° (P〈 0.01).Conclusion: These results indicate that the size of the contact areas depends to a slight extent on the joint position, but that at all loads and flexion angles a bicentric contact and an important central joint space width emerge because of the concave incongruity of the joint, These data may be used for numerical calculations, analysing the effects of incongruity on the joint stress and on the functional adaptation of the subarticular tissues. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092430306
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  • 8
    Electronic Resource
    Electronic Resource
    Morphomechanics of the humero-ulnar joint: II. Concave incongruity determines the distribution of load and subchondral mineralization (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    The @Anatomical Record 243 (1995), S. 327-335 
    Details
    ISSN: 0003-276X
    Keywords: Elbow ; Humero-ulnar joint ; Incongruity ; Finite element analysis ; Articular cartilage ; Subchondral mineralization ; Bone density ; Joint stress ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: Background: A deeper joint socket (concave incongruity) is found at most angles of flexion of the humero-ulnar joint and maintained over a wide range of physiological loading. It is, however, unclear how far this incongruity affects the distribution of load and subchondral mineralization of this joint as compared with a congruous configuration.Methods: Two nonlinear, axisymmetrical finite element models with two cartilage layers were constructed, one congruous and one incongruous, with a joint space of realistic magnitude. The distribution of subchondral mineralization was determined by computed tomography osteoabsorptiometry in the same six specimens that were investigated in the first part of the study, and compared with the biomechanical data obtained there and the predictions of the models.Results: In the congruous case, the center of the socket is highly loaded, whereas the periphery does not experience mechanical stimulation. A central bone density maximum is predicted. With concave incongruity the position of the contact areas shifts from the joint margin towards the center as the load increases, and the peak stresses are considerably lower. A bicentric ventro-dorsal distribution pattern of subchondral mineralization is predicted, and this is actually found in the six specimens.Conclusions: Concave incongruity is shown to determine load transmission and subchondral mineralization of the humero-ulnar joint. It is suggested that this shape leads to a more even distribution of stress, provides intermittent stimulation of the cartilaginous tissue, and has beneficial effects on the metabolism, nutrition, and lubrication of the articular cartilage during cyclic loading. © 1995 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ar.1092430307
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