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Peter M Villiger - One of the best experts on this subject based on the ideXlab platform.
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effect of rheumatoid arthritis and age on Metacarpal Bone shaft geometry and density a longitudinal pqct study in postmenopausal women
Seminars in Arthritis and Rheumatism, 2020Co-Authors: Daniel Aeberli, H Bonel, Burkhard Moller, Niklaus Fankhauser, Roger Zebaze, Peter M VilligerAbstract:Abstract Objective This study aimed to elucidate the effects of changes in the geometry and density of the Metacarpal Bone of patients with rheumatoid arthritis (RA). Methods This prospective study included consecutive postmenopausal RA patients who met the American College of Rheumatology Criteria and healthy controls (HC). Peripheral quantitative computed tomography scans at 50% of the total Metacarpal shaft (Third Metacarpal Bone) were obtained at baseline and follow-ups. Use of bisphosphonates (BP), glucocorticoids (GC), biologics, and disease-modifying anti-rheumatic drugs (DMARD) was monitored (baseline to follow-up). Total cross-sectional area (CSA), cortical-transitional zone and compact zone CSA, cortical volumetric Bone mineral density, and compact cortex porosity were measured. A linear mixed-effects model was used to determine significant differences in the rate of change in the RA and control groups and in RA patient subgroups. Results Thirty-nine RA patients and 42 consecutive postmenopausal HC were followed for 63 months. RA and HC depicted a time-dependent increase of medullary CSA (+0.41 mm2/year, P Conclusion Increase in medullary Metacarpal CSA and thinning of the cortical CSA are physiological and time dependent. RA status is associated with loss in cortical density. Even upon biological therapy, low glucocorticoid dose affects Metacarpal Bone shaft geometry and density over time.
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reduced trabecular Bone mineral density and cortical thickness accompanied by increased outer Bone circumference in Metacarpal Bone of rheumatoid arthritis patients a cross sectional study
Arthritis Research & Therapy, 2010Co-Authors: Daniel Aeberli, Prisca Eser, H Bonel, Jolanda Widmer, Gion Caliezi, Pierrealain Varisco, Burkhard Moller, Peter M VilligerAbstract:Introduction: The objective of this study was to assess three-dimensional Bone geometry and density at the epiphysis and shaft of the Third meta-carpal Bone of rheumatoid arthritis (RA) patients in comparison to healthy controls with the novel method of peripheral quantitative computed tomography (pQCT). Methods: PQCT scans were performed in 50 female RA patients and 100 healthy female controls at the distal epiphyses and shafts of the Third Metacarpal Bone, the radius and the tibia. Reproducibility was determined by coefficient of varia-tion. Bone densitometric and geometric parameters were compared between the two groups and correlated to disease characteristics. Results: Reproducibility of different pQCT parameters was between 0.7% and 2.5%. RA patients had 12% to 19% lower trabecular Bone mineral density (BMD) (P ≤ 0.001) at the distal epiphyses of radius, tibia and Metacarpal Bone. At the shafts of these Bones RA patients had 7% to 16% thinner cortices (P ≤ 0.03). Total cross-sectional area (CSA) at the Metacarpal Bone shaft of pa-tients was larger (between 5% and 7%, P < 0.02), and relative cortical area was reduced by 13%. Erosiveness by Ratingen score correlated negatively with tra-becular and total BMD at the epiphyses and shaft cortical thickness of all measured Bones (P < 0.04). Conclusions: Reduced trabecular BMD and thinner cortices at peripheral Bones, and a greater Bone shaft diameter at the Metacarpal Bone suggest RA spe-cific Bone alterations. The proposed pQCT protocol is reliable and allows measuring juxta-articular trabecular BMD and shaft geometry at the Metacarpal Bone.
Alan Boyde - One of the best experts on this subject based on the ideXlab platform.
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combined nanoindentation testing and scanning electron microscopy of Bone and articular calcified cartilage in an equine fracture predilection site
European Cells & Materials, 2010Co-Authors: Michael Doube, E C Firth, Alan Boyde, Andrew J. BushbyAbstract:Condylar fracture of the Third Metacarpal Bone (Mc3) is the commonest cause of racetrack fatality in Thoroughbred horses. Linear defects involving hyaline articular cartilage, articular calcified cartilage (ACC) and subchondral Bone (SCB) have been associated with the fracture initiation site, which lies in the sagittal grooves of the Mc3 condyle. We discovered areas of thickened and abnormally-mineralised ACC in the sagittal grooves of several normal 18-monthold horses, at the same site that linear defects and condylar fracture occur in older Thoroughbreds and questioned whether this tissue had altered mechanical properties. We embedded Bone slices in PMMA, prepared flat surfaces normal to the articular surface and studied ACC and SCB using combined quantitative backscattered electron scanning electron microscopy (qBSE) and nanoindentation testing: this allowed correlation of mineralisation density and tissue stiffness (E) at the micron scale. We studied both normal and affected grooves, and also normal condylar regions. Large arrays of indentations could be visualised as 2-dimensional maps of E with a limit to resolution of indentation spacing, which is much larger than qBSE pixel spacing. ACC was more highly mineralised but less stiff in early linear defects than in control regions, while subchondral Bone was more highly mineralised and stiffer in specimens with early linear defects than those without. Thus both ACC and SCB mineralisation may be abnormal in a class of early linear defect in 18-month-old Thoroughbred horses, and this may possibly contribute to later fracture of the Mc3 condyle.
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musculoskeletal responses of 2 year old thoroughbred horses to early training 8 quantitative back scattered electron scanning electron microscopy and confocal fluorescence microscopy of the epiphysis of the Third Metacarpal Bone
New Zealand Veterinary Journal, 2005Co-Authors: Alan Boyde, E C FirthAbstract:Abstract AIM: To characterise and explain the increase in density evident by computerised tomography (CT) and radiography in companion studies as a response to training, in Bone in the palmar and dorsal regions of the condyles of the Third Metacarpal Bone (Mc3) of 2-year-old Thoroughbred horses. METHODS: Compositional back-scattered electron (BSE) imaging in scanning electron microscopy (SEM) and confocal scanning laser microscopy (CSLM) were conducted on polymethyl methacrylate (PMMA)-embedded mediolateral slices of the right distal Mc3 from seven 2-year-old Thoroughbred horses trained on a racetrack and seven untrained horses kept at pasture. One left Mc3 from each group was studied in transverse section planes. This study focussed on regions of Mc3 found to differ in density between the trained and untrained horses in companion studies using CT and radiography. RESULTS: The increase of Bone density in the condyles of Mc3 in trained horses compared with untrained horses occurred, without prior osteoclas...
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articular calcified cartilage canals in the Third Metacarpal Bone of 2 year old thoroughbred racehorses
Journal of Anatomy, 2004Co-Authors: Alan Boyde, E C FirthAbstract:We describe morphological aspects of the articular calcified cartilage mineralizing front ‘tidemark’ in the distal joint surface of the Third Metacarpal Bone from 14 horses. Compositional backscattered electron scanning electron microscopy and confocal scanning light microscopy were conducted on polymethylmethacrylate (PMMA)-embedded medio-lateral slices. After maceration, scanning electron microscopy (SEM) was used to study the calcified cartilage surface in the ‘wedges’ intervening between the slices. An anatomically reproducible clustering of canals in the calcified cartilage was found at one site on the sagittal ridge in all the horses. The site is one that is relatively less loaded during joint function. These canals through calcified cartilage result from osteoclastic resorption (cutting cones) penetrating from Bone through to the non-mineralized hyaline articular cartilage. Their presence may indicate a pathway for connection between Bone and cartilage extracellular fluid. In one horse, repair of such canals by plugging with new calcified cartilage was demonstrated. Differences in the degree of mineralization of regions of cartilage were seen in the combined compositional-cum-topographical backscattered SEM images of the macerated ‘tidemark’ front. More-or-less circular patches of lower mineralization density were frequently centred on (and may possibly originate from) canals. These microanatomical features should be searched for in other joints, at other ages and in other species to discover their frequency and significance.
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three dimensional structure of the distal condyles of the Third Metacarpal Bone of the horse
Equine Veterinary Journal, 1999Co-Authors: Alan Boyde, Y Haroon, S J Jones, C M RiggsAbstract:Summary This study examined the three-dimensional (3D) microarchitecture of regions of the equine Third Metacarpal Bone (McIII) commonly involved in distal condylar fractures. Limbs were obtained from Thoroughbred horses (neonates to age 24 years) destroyed for inoperable fractures and a variety of other conditions. Beams, blocks and sections were cut in the principal axes, some embedded in PMMA and others examined unembedded. Several methods were used to study the 3D structure, including conventional and confocal optical microscopy, scanning electron microscopy (SEM) and radiography. The mineralised articular cartilage tends to cleave in the sagittal plane. Proximal to the subchondral Bone, the main trabeculae are robust plates running in the sagittal direction with less significant mediolateral connections. Small blood vessel canals lie inside the sagittal plates. This structure gives maximum strength and protection in the sagittal plane in which the Bone rotates, but offers minimal resistance to fracture propagation in this plane. The anatomical course of the common distal condylar fractures of the Third Metacarpal Bones can be explained by underlying anisotropic structural features of the mineralised tissues.
E C Firth - One of the best experts on this subject based on the ideXlab platform.
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combined nanoindentation testing and scanning electron microscopy of Bone and articular calcified cartilage in an equine fracture predilection site
European Cells & Materials, 2010Co-Authors: Michael Doube, E C Firth, Alan Boyde, Andrew J. BushbyAbstract:Condylar fracture of the Third Metacarpal Bone (Mc3) is the commonest cause of racetrack fatality in Thoroughbred horses. Linear defects involving hyaline articular cartilage, articular calcified cartilage (ACC) and subchondral Bone (SCB) have been associated with the fracture initiation site, which lies in the sagittal grooves of the Mc3 condyle. We discovered areas of thickened and abnormally-mineralised ACC in the sagittal grooves of several normal 18-monthold horses, at the same site that linear defects and condylar fracture occur in older Thoroughbreds and questioned whether this tissue had altered mechanical properties. We embedded Bone slices in PMMA, prepared flat surfaces normal to the articular surface and studied ACC and SCB using combined quantitative backscattered electron scanning electron microscopy (qBSE) and nanoindentation testing: this allowed correlation of mineralisation density and tissue stiffness (E) at the micron scale. We studied both normal and affected grooves, and also normal condylar regions. Large arrays of indentations could be visualised as 2-dimensional maps of E with a limit to resolution of indentation spacing, which is much larger than qBSE pixel spacing. ACC was more highly mineralised but less stiff in early linear defects than in control regions, while subchondral Bone was more highly mineralised and stiffer in specimens with early linear defects than those without. Thus both ACC and SCB mineralisation may be abnormal in a class of early linear defect in 18-month-old Thoroughbred horses, and this may possibly contribute to later fracture of the Mc3 condyle.
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musculoskeletal responses of 2 year old thoroughbred horses to early training 8 quantitative back scattered electron scanning electron microscopy and confocal fluorescence microscopy of the epiphysis of the Third Metacarpal Bone
New Zealand Veterinary Journal, 2005Co-Authors: Alan Boyde, E C FirthAbstract:Abstract AIM: To characterise and explain the increase in density evident by computerised tomography (CT) and radiography in companion studies as a response to training, in Bone in the palmar and dorsal regions of the condyles of the Third Metacarpal Bone (Mc3) of 2-year-old Thoroughbred horses. METHODS: Compositional back-scattered electron (BSE) imaging in scanning electron microscopy (SEM) and confocal scanning laser microscopy (CSLM) were conducted on polymethyl methacrylate (PMMA)-embedded mediolateral slices of the right distal Mc3 from seven 2-year-old Thoroughbred horses trained on a racetrack and seven untrained horses kept at pasture. One left Mc3 from each group was studied in transverse section planes. This study focussed on regions of Mc3 found to differ in density between the trained and untrained horses in companion studies using CT and radiography. RESULTS: The increase of Bone density in the condyles of Mc3 in trained horses compared with untrained horses occurred, without prior osteoclas...
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articular calcified cartilage canals in the Third Metacarpal Bone of 2 year old thoroughbred racehorses
Journal of Anatomy, 2004Co-Authors: Alan Boyde, E C FirthAbstract:We describe morphological aspects of the articular calcified cartilage mineralizing front ‘tidemark’ in the distal joint surface of the Third Metacarpal Bone from 14 horses. Compositional backscattered electron scanning electron microscopy and confocal scanning light microscopy were conducted on polymethylmethacrylate (PMMA)-embedded medio-lateral slices. After maceration, scanning electron microscopy (SEM) was used to study the calcified cartilage surface in the ‘wedges’ intervening between the slices. An anatomically reproducible clustering of canals in the calcified cartilage was found at one site on the sagittal ridge in all the horses. The site is one that is relatively less loaded during joint function. These canals through calcified cartilage result from osteoclastic resorption (cutting cones) penetrating from Bone through to the non-mineralized hyaline articular cartilage. Their presence may indicate a pathway for connection between Bone and cartilage extracellular fluid. In one horse, repair of such canals by plugging with new calcified cartilage was demonstrated. Differences in the degree of mineralization of regions of cartilage were seen in the combined compositional-cum-topographical backscattered SEM images of the macerated ‘tidemark’ front. More-or-less circular patches of lower mineralization density were frequently centred on (and may possibly originate from) canals. These microanatomical features should be searched for in other joints, at other ages and in other species to discover their frequency and significance.
Christopher E Kawcak - One of the best experts on this subject based on the ideXlab platform.
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qualitative assessment of Bone density at the distal articulating surface of the Third Metacarpal in thoroughbred racehorses with and without condylar fracture
Equine Veterinary Journal, 2017Co-Authors: A B Loughridge, Ann M Hess, T D H Parkin, Christopher E KawcakAbstract:Reasons for performing study: Changes in subchondral Bone density, induced by the repetitive cyclical loading of exercise, may potentiate fatigue damage and the risk of fracture. Objectives: To use computed tomography (CT) to characterise Bone density patterns at the articular surface of the Third Metacarpal Bone in racehorses with and without lateral condylar fractures. Study Design: Case control Methods: Computed tomographic images of the distal articulating surface of the Third Metacarpal Bone were obtained from Thoroughbred racehorses subjected to euthanasia in the UK. Third Metacarpal Bones were divided into 3 groups based on lateral condyle status; fractured (FX, n = 42), nonfractured contralateral condyle (NFX, n = 42) and control condyles from horses subjected to euthanasia for reasons unrelated to the Third Metacarpal Bone (control, n = 94). Colour CT images were generated whereby each colour represented a range of pixel values and thus a relative range of Bone density. A density value was calculated qualitatively by estimating the percentage of each colour within a specific region. Subchondral Bone density was assessed in 6 regions from dorsal to palmar and 1 mm medial and lateral to the centre of the lateral parasagittal groove in NFX and control condyles and 1 mm medial and lateral to the fracture in FX condyles. Results: Bone density was significantly higher in the FX and NFX condyles compared with control condyles for all 6 regions. A significantly higher Bone density was observed in FX condyles relative to NFX condyles in the lateral middle and lateral palmar regions. Fractured condyles had increased heterogeneity in density among the 6 regions of interest compared with control and NFX condyles. Conclusions: Adjacent to the fracture, a focal increase in Bone density and increased heterogeneity of density were characteristic of limbs with lateral condylar fractures compared with control and NFX condyles. These differences may represent pathological changes in Bone density that increase the risk for lateral condylar fractures in racehorses.
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COMPARISON OF GROSS AND HISTOPATHOLOGIC FINDINGS WITH QUANTITATIVE COMPUTED TOMOGRAPHIC Bone DENSITY IN THE DISTAL Third Metacarpal Bone OF RACEHORSES
2016Co-Authors: Martha G Drum, Christopher E Kawcak, Wayne C Mcilwraith, R W Norrdin, Richard D Park, Clifford M LesAbstract:Comparison of subchondral Bone density determined by quantitative computed tomography (CT) with gross and histopathologic changes have not been made in horses. The goal of this study was to determine if mean quantitative CT density and mean voxel standard deviation are associated with the presence and severity of osteochondral lesions in the palmar aspect of the distal Third Metacarpal Bone in racing horses. Meta-carpophalangeal joints from nine racehorses were imaged using CT and scored for gross damage. Four-millimeter-thick sagittal and 301 palmar dorsal plane sections were cut, decalcified and stained with hem-atoxylin and eosin from the distal Third Metacarpal Bone. Microscopic osteochondral lesions and subchondral remodeling were scored on a scale of 0–3. Percent subchondral Bone, expressed as the ratio of Bone volume to tissue volume, was also measured. Mean quantitative CT density and mean voxel standard deviation were measured from three-dimensional models of CT images comparable with histologic sections. Mean quantitative CT density was not associated with lesion severity or number of lesions. A weak correlation between mean quantitative CT density and gross score was found, but mean quantitative CT density was not predictive for gross score. Mean voxel standard deviation was not correlated with gross or histopathologic measures, but was predictive of mild osteochondral lesions. Results support the association of subchondral remodeling with the development of palmar Metacarpal lesions. However, there was not a strong correlation between mean quan-titative CT density or mean voxel standard deviation and histopathologic lesions of the distal Third metacarpa
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effect of sequential removal of parts of the second Metacarpal Bone on the biomechanical stability of the equine carpus biomechanical stability of the equine carpus
Veterinary Surgery, 2012Co-Authors: Kathryn A Seabaugh, Jeremy Hubert, Kirk C Mcgilvray, Christopher E Kawcak, Brandon G SantoniAbstract:Objective To quantify changes in biomechanical stability and stiffness within the equine carpus after removal of 50%, 80%, and 100% of the second Metacarpal Bone (MC2). Study Design In vitro biomechanical study. Methods Cadaveric equine forelimbs (n = 16) were evaluated. Intact constructs were loaded in axial compression from 0 to 5000 N and compression + torsion (5000 N ± 20°) for 5 cycles. This was repeated after removal of 50%, 80%, and 100% of MC2. The primary biomechanical outcome variables were the compressive stiffness and compressive + torsional stiffness of the carpus. Relative kinematic motion was also evaluated between the second carpal Bone (C2) and the radial carpal Bone (RC), C2 and the Third Metacarpal Bone (MC3) and C2 and the Third carpal Bone (C3). Results A significant decrease in compressive + torsional stiffness was found after 100% removal of MC2. Compressive stiffness of the carpus did not change after 100% MC2 removal. A significant increase in relative rotation around the z-axis (rotation around the long axis) was observed for C2 versus MC3 and C2 versus C3 when 100% of MC2 was removed as compared to 80%, 50%, and 0% removal. No significant difference in relative rotation between C2 and RC was detected. Conclusions The biomechanical results reported here suggest that the torsional stability of the equine carpus is significantly decreased only after complete resection of MC2.
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the effect of sequence selection and field strength on detection of osteochondral defects in the metacarpophalangeal joint
Veterinary Radiology & Ultrasound, 2011Co-Authors: Natasha M Werpy, Anthony Pease, Christopher E KawcakAbstract:Six cadaver forelimbs were imaged in two high-field magnetic resonance (MR) systems and one low-field MR system following the creation of osteochondral defects on the palmar distal aspect of the Third Metacarpal Bone. The following sequences were performed using all three systems: proton density (PD) turbo spin echo, T2* gradient echo (GRE), T2-weighted fast spin echo, and short tau inversion recovery. In addition, 3D T1 GRE sagittal standard and motion insensitive sequences were obtained using the low-field system. PD fat saturated and 3D T1-weighted spoiled GRE images with and without fat suppression were acquired with the high-field systems. Lesions were measured and assigned a confidence score. The images obtained using high-field systems (1.0 and 1.5 T) more accurately represented the osteochondral defects when compared with low-field system (0.27 T) images. The largest difference was observed when evaluating articular cartilage defects, which were not identified on the low-field images. Sequence selection affected the appearance of the lesions. On all systems the turbo and fast spin echo sequences more accurately represented the lesion size and shape when compared with the GRE sequences. The T1 GRE sequence is the only sequence that appears to allow visualization of the articular cartilage on the low-field images, but is limited in providing adequate cartilage visualization. Confidence scores were greater on the high-field systems when compared with the low-field system.
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mechanical loading of the distal end of the Third Metacarpal Bone in horses during walking and trotting
American Journal of Veterinary Research, 2010Co-Authors: Jonathan S Merritt, Colin Burvill, Christopher E Kawcak, Marcus G Pandy, Nicholas A T Brown, Wayne C Mcilwraith, Helen M. S. DaviesAbstract:Objective—To assess the net mechanical load on the distal end of the Third Metacarpal Bone in horses during walking and trotting. Animals—3 Quarter Horses and 1 Thoroughbred. Procedures—Surface strains measured on the left Third Metacarpal Bone of the Thorough-bred were used with a subject-specific model to calculate loading (axial compression, bending, and torsion) of the structure during walking and trotting. Forelimb kinematics and ground reaction forces measured in the 3 Quarter Horses were used with a musculoskeletal model of the distal portion of the forelimb to determine loading of the distal end of the Third Metacarpal Bone. Results—Both methods yielded consistent data regarding mechanical loading of the distal end of the Third Metacarpal Bone. During walking and trotting, the distal end of the Third Metacarpal Bone was loaded primarily in axial compression as a result of the sum of forces exerted on the Metacarpal condyles by the proximal phalanx and proximal sesamoid Bones. Conclusions and Clini...
Susan M. Stover - One of the best experts on this subject based on the ideXlab platform.
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preexisting lesions associated with complete diaphyseal fractures of the Third Metacarpal Bone in 12 thoroughbred racehorses
Journal of Veterinary Diagnostic Investigation, 2017Co-Authors: Sarah N Gray, Mathieu Spriet, Tanya C Garcia, Francisco A Uzal, Susan M. StoverAbstract:We characterized features of complete diaphyseal fractures of Third Metacarpal Bones in Thoroughbred racehorses. Given that stress fractures are known to occur in the Third Metacarpal Bone, an additional aim was to determine if complete fractures are associated with signs of a preexisting incomplete stress fracture. Bilateral metacarpi from 12 Thoroughbred racehorses euthanized because of complete unilateral Metacarpal diaphyseal fracture were examined visually and radiographically. Open, comminuted, transverse or short oblique fractures occurred in the middle of the diaphysis or supracondylar region. Periosteal surface discoloration and Bone callus formation contiguous with the fracture line were present in fractured Bones. All contralateral intact metacarpi had gross anatomic lesions, and 10 had radiographic abnormalities similar to those observed on fractured metacarpi. Catastrophic Metacarpal fractures occurred in racehorses with bilateral evidence of preexisting Bone injury.
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how do metacarpophalangeal joint extension collateromotion and axial rotation influence dorsal surface strains of the equine proximal phalanx at different loads in vitro
Journal of Biomechanics, 2013Co-Authors: E R Singer, Tanya C Garcia, Susan M. StoverAbstract:Abstract The biomechanical circumstances that promote sagittal fracture of the equine proximal phalanx (P1) are poorly understood. In order to improve our understanding of equine metacarpophalangeal joint (MCPJ) biomechanics and potential aetiologies of sagittal P1 fractures, the study objectives were to quantify P1 Bone strains, collateromotion and axial rotation during MCPJ extension under controlled loading circumstances. Unilateral limbs from six cadavers were instrumented with Bone reference markers for measurement of P1 movement relative to Third Metacarpal Bone positions during axial limb loading to 10,500 N. Bone reference markers recorded by video were digitized and the movement analyzed during MCPJ extension. Concurrently, dorsoproximal P1 surface strains were measured with one uniaxial and one rosette strain gauge. Strain gauge data was reduced to determine principal and shear strain magnitude and direction. External axial rotation and collateromotion increased with increasing MCPJ extension. Maximum principal strain increased linearly as load increased from 2000 to 10,500 N. Minimum principal and maximum shear strains had curvilinear relationships with limb loading, with negligible strain magnitude until approximately 6000 N load, after which strain increased rapidly. The direction of P1 minimum principal strain shifted approximately 30–40° as load increased from 5400 N to 10,000 N, moving from proximolateral–distomedial to a nearly proximodistal direction. At near maximal MCPJ extension, with concurrent axial rotation and collateromotion, a rapid increase in dorsoproximal P1 Bone strain and a change in principal strain direction occurred. The alterations in principal strain magnitude and direction associated with maximal MCPJ extension may support a biomechanical theory for sagittal P1 fracture occurrence in horses.
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osteon pullout in the equine Third Metacarpal Bone effects of ex vivo fatigue
Journal of Orthopaedic Research, 2003Co-Authors: L P Hiller, Scott J Hazelwood, Jeffery C Gibeling, Susan M. Stover, V.a. Gibson, C S Prater, Oscar C Yeh, R B MartinAbstract:An important concept in Bone mechanics is that osteons influence mechanical properties in several ways, including contributing to toughness and fatigue strength by debonding from the interstitial matrix so as to "bridge" developing cracks. Observations of "pulled out" osteons on fracture surfaces are thought to be indicative of such behavior. We tested the hypothesis that osteon pullout varies with mode of loading (fatigue vs. monotonic), cortical region, elastic modulus, and fatigue life. Mid-diaphseal beams from the dorsal, medial, and lateral regions of the equine Third Metacarpal Bone were fractured in four point bending by monotonic loading to failure under deflection control, with or without 10(5) cycles of previous fatigue loading producing 5000 microstrain (15-20% of the expected failure strain) on the first cycle; or sinusoidal fatigue loading to failure, under load or deflection control, with the initial cycle producing 10,000 microstrain (30-40% of the expected failure strain). Using scanning electron microscopy, percent fracture surface area exhibiting osteon pullout (%OP.Ar) was measured. Monotonically loaded specimens and the compression side of fatigue fracture surfaces exhibited no osteon pullout. In load-controlled fatigue, pullout was present on the tension side of fracture surfaces, was regionally dependent (occurring to a greater amount dorsally), and was correlated negatively with elastic modulus and positively with fatigue life. Regional variation in %OP.Ar was also significant for the pooled (load and deflection controlled) fatigue specimens. %OP.Ar was nearly significantly greater in deflection controlled fatigue specimens than in load-controlled specimens (p=0.059). The data suggest that tensile fatigue loading of cortical Bone eventually introduces damage that results in osteonal debonding and pullout, which is also associated with increased fatigue life via mechanisms that are not yet clear.
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Biomechanical investigation of the association between suspensory ligament injury and lateral condylar fracture in thoroughbred racehorses.
Veterinary surgery : VS, 2003Co-Authors: Sarah S. Le Jeune, Susan M. Stover, Melinda H. Macdonald, Kenneth T. Taylor, Max GerdesAbstract:Objective-To determine whether partial transection of the medial branch of the suspensory ligament (MBSL) alters equine Third Metacarpal Bone (MC3) condylar surface strains and forelimb, distal joint angles in a manner consistent with promotion of lateral condylar fracture. Study Design-In vitro biomechanical experiment. Sample Population-Right forelimbs from 7 Thoroughbred horse cadavers. Methods-Lateral and medial MC3 condylar, dorsal and abaxial, Bone surface strains and distal joint angles were measured both before and after partial transection of the MBSL during in vitro axial limb compression. Dorsal, principal Bone strains and abaxial, uniaxial, and proximodistal strains were compared before and after MBSL partial transection at 1,400-, 3,000-, and 5,600-N loads. Results-Bone strains increased in all locations with increasing axial load. All lateral condylar Bone strains were significantly higher, and abaxial surface medial condylar Bone strain was significantly lower, after partial transection of the MBSL. Respective distal joints became more flexed or extended as axial load increased but were not significantly different after partial transection of the MBSL. Conclusions-Partial transection of the MBSL increases in vitro MC3 lateral condylar Bone surface strains. Clinical Relevance-Loss of integrity of the medial branch of the suspensory ligament could increase the risk for lateral condylar fracture in Thoroughbred horses by amplifying Bone strain in the lateral condyle.
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stiff and strong compressive properties are associated with brittle post yield behavior in equine compact Bone material
Journal of Orthopaedic Research, 2002Co-Authors: Susan M. Stover, Kenneth T. Taylor, Joyce H Keyak, A J KanepsAbstract:Abstract Our hypothesis was that post-yield mechanical behavior of compact Bone material in compression, defined as the stress, strain, or energy absorbed between 0.2% strain-offset and the point of maximum stress, is correlated with material density, modulus, strength, histomorphometric evidence of remodeling, and post-failure gross specimen morphology. Post-yield behavior of compact Bone material from the Third Metacarpal Bone of 10 horses, ages 5 months to 20 years, was investigated using single-load compression-to-failure. The post-yield stress, strain, and absorbed energy were compared with the compressive elastic modulus, yield stress, ash density, post-failure macroscopic appearance of the specimen, and histologic evidence of remodeling. High values of elastic modulus, yield stress, and ash density were associated with low values of post-yield mechanical properties (stress, strain, and absorbed energy). Macroscopic post-failure morphology was associated with post-yield mechanical behavior, in that specimens displaying fractures were associated with lower post-yield mechanical properties, and that those without evidence of frank fracture were associated with higher post-yield mechanical properties. Microscopic evidence of remodeling activity was associated with high post-yield mechanical properties, but not with gross post-failure morphology. There was an abrupt change from relatively high values to extremely low values of post-yield mechanical properties at intermediate levels of ash density. This feature may serve as a functional upper limit to the maximization of Bone material stiffness and strength.