Biomechanical Function (biomechanical + function)

Distribution by Scientific Domains


Selected Abstracts


Trabecular bone structure in the mandibular condyles of gouging and nongouging platyrrhine primates

AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2010
Timothy M. Ryan
Abstract The relationship between mandibular form and biomechanical function is a topic of significant interest to morphologists and paleontologists alike. Several previous studies have examined the morphology of the mandible in gouging and nongouging primates as a means of understanding the anatomical correlates of this feeding behavior. The goal of the current study was to quantify the trabecular bone structure of the mandibular condyle of gouging and nongouging primates to assess the functional morphology of the jaw in these animals. High-resolution computed tomography scan data were collected from the mandibles of five adult common marmosets (Callithrix jacchus), saddle-back tamarins (Saguinus fuscicollis), and squirrel monkeys (Saimiri sciureus), respectively, and various three-dimensional morphometric parameters were measured from the condylar trabecular bone. No significant differences were found among the taxa for most trabecular bone structural features. Importantly, no mechanically significant parameters, such as bone volume fraction and degree of anisotropy, were found to vary significantly between gouging and nongouging primates. The lack of significant differences in mechanically relevant structural parameters among these three platyrrhine taxa may suggest that gouging as a habitual dietary behavior does not involve significantly higher loads on the mandibular condyle than other masticatory behaviors. Alternatively, the similarities in trabecular architecture across these three taxa may indicate that trabecular bone is relatively unimportant mechanically in the condyle of these primates and therefore is functionally uninformative. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. [source]


Vulnerability of the superficial zone of immature articular cartilage to compressive injury

ARTHRITIS & RHEUMATISM, Issue 10 2010
Bernd Rolauffs
Objective The zonal composition and functioning of adult articular cartilage causes depth-dependent responses to compressive injury. In immature cartilage, shear and compressive moduli as well as collagen and sulfated glycosaminoglycan (sGAG) content also vary with depth. However, there is little understanding of the depth-dependent damage caused by injury. Since injury to immature knee joints most often causes articular cartilage lesions, this study was undertaken to characterize the zonal dependence of biomechanical, biochemical, and matrix-associated changes caused by compressive injury. Methods Disks from the superficial and deeper zones of bovine calves were biomechanically characterized. Injury to the disks was achieved by applying a final strain of 50% compression at 100%/second, followed by biomechanical recharacterization. Tissue compaction upon injury as well as sGAG density, sGAG loss, and biosynthesis were measured. Collagen fiber orientation and matrix damage were assessed using histology, diffraction-enhanced x-ray imaging, and texture analysis. Results Injured superficial zone disks showed surface disruption, tissue compaction by 20.3 ± 4.3% (mean ± SEM), and immediate biomechanical impairment that was revealed by a mean ± SEM decrease in dynamic stiffness to 7.1 ± 3.3% of the value before injury and equilibrium moduli that were below the level of detection. Tissue areas that appeared intact on histology showed clear textural alterations. Injured deeper zone disks showed collagen crimping but remained undamaged and biomechanically intact. Superficial zone disks did not lose sGAG immediately after injury, but lost 17.8 ± 1.4% of sGAG after 48 hours; deeper zone disks lost only 2.8 ± 0.3% of sGAG content. Biomechanical impairment was associated primarily with structural damage. Conclusion The soft superficial zone of immature cartilage is vulnerable to compressive injury, causing superficial matrix disruption, extensive compaction, and textural alteration, which results in immediate loss of biomechanical function. In conjunction with delayed superficial sGAG loss, these changes may predispose the articular surface to further softening and tissue damage, thus increasing the risk of development of secondary osteoarthritis. [source]


Developmental and osteoarthritic changes in Col6a1 -knockout mice: Biomechanics of type VI collagen in the cartilage pericellular matrix

ARTHRITIS & RHEUMATISM, Issue 3 2009
Leonidas G. Alexopoulos
Objective Chondrocytes, the sole cell type in articular cartilage, maintain the extracellular matrix (ECM) through a homeostatic balance of anabolic and catabolic activities that are influenced by genetic factors, soluble mediators, and biophysical factors such as mechanical stress. Chondrocytes are encapsulated by a narrow tissue region termed the "pericellular matrix" (PCM), which in normal cartilage is defined by the exclusive presence of type VI collagen. Because the PCM completely surrounds each cell, it has been hypothesized that it serves as a filter or transducer for biochemical and/or biomechanical signals from the cartilage ECM. The present study was undertaken to investigate whether lack of type VI collagen may affect the development and biomechanical function of the PCM and alter the mechanical environment of chondrocytes during joint loading. Methods Col6a1,/, mice, which lack type VI collagen in their organs, were generated for use in these studies. At ages 1, 3, 6, and 11 months, bone mineral density (BMD) was measured, and osteoarthritic (OA) and developmental changes in the femoral head were evaluated histomorphometrically. Mechanical properties of articular cartilage from the hip joints of 1-month-old Col6a1,/,, Col6a1+/,, and Col6a1+/+ mice were assessed using an electromechanical test system, and mechanical properties of the PCM were measured using the micropipette aspiration technique. Results In Col6a1,/, and Col6a1+/, mice the PCM was structurally intact, but exhibited significantly reduced mechanical properties as compared with wild-type controls. With age, Col6a1,/, mice showed accelerated development of OA joint degeneration, as well as other musculoskeletal abnormalities such as delayed secondary ossification and reduced BMD. Conclusion These findings suggest that type VI collagen has an important role in regulating the physiology of the synovial joint and provide indirect evidence that alterations in the mechanical environment of chondrocytes, due to either loss of PCM properties or Col6a1,/, -derived joint laxity, can lead to progression of OA. [source]


The medial and lateral bellies of gastrocnemius: A cadaveric and ultrasound investigation

CLINICAL ANATOMY, Issue 1 2008
Tony Antonios
Abstract It is commonly reported that the medial belly (MG) of the gastrocnemius muscle extends further distally than the lateral belly (LG). This observation is made in several standard anatomy texts with no explanation or quantitative data. In this study, the medial and lateral bellies of gastrocnemius in 45 embalmed cadavers were measured. The observed difference in length of the two bellies was found to be highly significant (mean difference in length = 1.74 cm, P < 0.001). In 8 out of 84 legs examined (9.5%), however, the MG was found to be shorter than the LG (three right legs, five left legs, bilateral in two individuals). Surprisingly, there was no correlation between the difference in muscle belly length in any individual and ipsilateral leg length or total body length, suggesting that the difference in belly length may be unrelated to biomechanical function. An ultrasound investigation into the activity pattern of the two bellies was carried out on five volunteers. Muscle activity was monitored during passive and active movements of the ankle and knee joints at different leg positions. During knee flexion and ankle plantarflexion, the LG contracted first in four of the five subjects, followed by the MG, then a period of either LG predomination or equal contraction. The fifth subject, who showed a reversed pattern of activity, had previously suffered an inversion injury of the ankle. We suggest that the initial activation of the LG may help to stabilize the ankle during plantarflexion. We found no evidence that gastrocnemius acts as a shunt muscle during distraction of the knee. Clin. Anat. 21:66,74, 2008. © 2007 Wiley-Liss, Inc. [source]


Is the circumferential tensile modulus within a human medial meniscus affected by the test sample location and cross-sectional area?

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2000
Kate Lechner
Quantifying the material properties of the human menisci is paramount to understanding their biomechanical functions within the knee. One important intrinsic material property governing the biomechanical functions of the meniscus is the circumferential tensile modulus. The purpose of this study was to determine if the circumferential tensile modulus of the human medial meniscus depends on the location and thickness of the sample tested. The following three hypotheses were tested: (a) the circumferential location (anterior, central, and posterior) does not significantly affect the tensile modulus, (b) the radial location (inner to outer) significantly affects the tensile modulus, and (c) the thicknes (cross-sectional area) significantly affects the tensile modulus. Test samples, whose length was oriented in parallel with the circumferential collagen fibers, were collected from different circumferential and radial locations throughout 30 human medial menisci. Samples of three different thicknesses (0.5, 1.5, and 3.0 mm) were taken from three equal groups of 10 menisci (i.e., one thickness per group). The circumferential tensile modulus was measured under quasi-statc loading. Statistical analysis showed no significant effect of the circumferential or radial location of the sample on the circumferential tensile modulus. This indicates that an overall circumferential tensile modulus may be calculated for the human medial meniscus by averaging the values determined at the various locations. However, the thickness of the test sample had a significant effect on the measured circumferential tensile modulus: the modulus varied inversely with the thickness. Thus, moduli determined from test samples that are too small in cross-sectional area overestimate the effective modulus of the tissue on the whole, and the cross-sectional area of the sample must be considered when determining a representative circumferential tensile modulus for the medial meniscus in a human knee. [source]


A radiologic and histologic study of the os peroneum: Prevalence, morphology, and relationship to degenerative joint disease of the foot and ankle in a cadaveric sample

CLINICAL ANATOMY, Issue 6 2009
C. Muehleman
Abstract The present study investigated the prevalence of an os peroneum (OP, a sesamoid bone) in a cadaveric sample and its relationship to the shape of the cuboid tuberosity, and cartilage degeneration at the cuboid tuberosity and in regional joints within the foot (first metatarsophalangeal and calcaneocuboid) and ankle. The fibularis longus tendon of 33 embalmed human cadavers (mean age 81 years) were obtained from the anatomy laboratory. Nineteen of 64 tendons (30%) displayed an OP both radiographically and histologically. The os peronei ranged in size from small spicules to prominent masses: mean area 2.48 mm2 (left) and 2.70 mm2 (right). Histologically, the os peronei were cancellous bone, the largest occupying most of the tendon at the point of contact with the cuboid tuberosity. Fibrocartilage was present at their borders, merging with dense regular fibrous tissue and peritenon. The talocrural, calcaneocuboid, and first metatarsophalangeal joints were examined for cartilage integrity and osteophytes based on an earlier suggestion that there may be an association between degenerative joint disease and endochondral bone formation. There was no statistical correlation between presence of an OP with any of the following parameters: age, gender, body size, cartilage degeneration, or osteophytes within any of the joints examined. Therefore, the presence of an OP does not appear to be associated with increased endochondral ossification or degenerative joint disease. This study does not preclude the possibility that sesamoid bone formation may be associated with biomechanical functions within the foot; thus, future studies may be warranted. Clin. Anat. 22:747,754, 2009. © 2009 Wiley-Liss, Inc. [source]