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1.  Tendon Gradient Mineralization for Tendon to Bone Interface Integration 
Tendon-to-bone integration is a great challenge for tendon or ligament reconstruction regardless of use of autograft or allograft tendons. We mineralized the tendon, thus transforming the tendon-to-bone into a “bone-to-bone” interface for healing. Sixty dog flexor digitorum profundus (FDP) tendons were divided randomly into 5 groups: 1) normal FDP tendon, 2) CaP (Non-extraction and mineralization without fetuin), 3) CaPEXT (Extraction by Na2HPO4 and mineralization without fetuin), 4) CaPFetuin (Non-extraction and mineralization with fetuin), and 5) CaPEXTFetuin (Extraction and mineralization with fetuin). The calcium and phosphate content significantly increased in tendons treated with combination of extraction and fetuin compared to the other treatments. Histology also revealed a dense mineral deposition throughout the tendon outer layers and penetrated into the tendon to a depth of 200 μm in a graded manner. Compressive moduli were significantly lower in the four mineralized groups compared with normal control group. No significant differences in maximum failure strength or stiffness were found in the suture pull-out test among all groups. Mineralization of tendon alters the interface from tendon to bone into mineralized tendon to bone, which may facilitate tendon-to-bone junction healing following tendon or ligament reconstruction.
doi:10.1002/jor.22412
PMCID: PMC4121959  PMID: 23939935
Tendon Mineralization; Graded Mineral; Tendon-to-Bone Healing; Tendon Allografts
2.  Validation of Shear Wave Elastography in Skeletal Muscle 
Journal of biomechanics  2013;46(14):10.1016/j.jbiomech.2013.07.033.
Skeletal muscle is a very dynamic tissue, thus accurate quantification of skeletal muscle stiffness throughout its functional range is crucial to improve the physical functioning and independence following pathology. Shear wave elastography (SWE) is an ultrasound-based technique that characterizes tissue mechanical properties based on the propagation of remotely induced shear waves. The objective of this study is to validate SWE throughout the functional range of motion of skeletal muscle for three ultrasound transducer orientations. We hypothesized that combining traditional materials testing (MTS) techniques with SWE measurements will show increased stiffness measures with increasing tensile load, and will correlate well with each other for trials in which the transducer is parallel to underlying muscle fibers. To evaluate this hypothesis, we monitored the deformation throughout tensile loading of four porcine brachialis whole-muscle tissue specimens, while simultaneously making SWE measurements of the same specimen. We used regression to examine the correlation between Young's modulus from MTS and shear modulus from SWE for each of the transducer orientations. We applied a generalized linear model to account for repeated testing. Model parameters were estimated via generalized estimating equations. The regression coefficient was 0.1944, with a 95% confidence interval of (0.1463 – 0.2425) for parallel transducer trials. Shear waves did not propagate well for both the 45° and perpendicular transducer orientations. Both parallel SWE and MTS showed increased stiffness with increasing tensile load. This study provides the necessary first step for additional studies that can evaluate the distribution of stiffness throughout muscle.
doi:10.1016/j.jbiomech.2013.07.033
PMCID: PMC3818126  PMID: 23953670
Ultrasonography; passive stiffness; materials testing; elastic moduli; shear wave elastography
3.  A High-Density Genetic Map for Soybean Based on Specific Length Amplified Fragment Sequencing 
PLoS ONE  2014;9(8):e104871.
Soybean is an important oil seed crop, but very few high-density genetic maps have been published for this species. Specific length amplified fragment sequencing (SLAF-seq) is a recently developed high-resolution strategy for large scale de novo discovery and genotyping of single nucleotide polymorphisms. SLAF-seq was employed in this study to obtain sufficient markers to construct a high-density genetic map for soybean. In total, 33.10 Gb of data containing 171,001,333 paired-end reads were obtained after preprocessing. The average sequencing depth was 42.29 in the Dongnong594, 56.63 in the Charleston, and 3.92 in each progeny. In total, 164,197 high-quality SLAFs were detected, of which 12,577 SLAFs were polymorphic, and 5,308 of the polymorphic markers met the requirements for use in constructing a genetic map. The final map included 5,308 markers on 20 linkage groups and was 2,655.68 cM in length, with an average distance of 0.5 cM between adjacent markers. To our knowledge, this map has the shortest average distance of adjacent markers for soybean. We report here a high-density genetic map for soybean. The map was constructed using a recombinant inbred line population and the SLAF-seq approach, which allowed the efficient development of a large number of polymorphic markers in a short time. Results of this study will not only provide a platform for gene/quantitative trait loci fine mapping, but will also serve as a reference for molecular breeding of soybean.
doi:10.1371/journal.pone.0104871
PMCID: PMC4130620  PMID: 25118194
4.  Multiple-locus variable number of tandem repeats analysis of Salmonella enterica serotype paratyphi A from Yuxi and comparison with isolates from the Chinese Medical Culture Collection Center 
Molecular Medicine Reports  2014;10(1):68-74.
The aim of the present study was to genotype Salmonella enterica serotype paratyphi A (SPA) isolated from Yuxi, China, in a multiple-locus variable number of tandem repeats (VNTRs) analysis (MLVA) and to compare them with isolates from the Chinese Medical Culture Collection Center (CMCC). Potential VNTRs were screened from the genomes of ATCC9150 and AKU_12601 using the Tandem Repeats Finder program. Nine VNTRs were established for MLVA typing of 195 SPA isolates from Yuxi and 20 isolates from CMCC. The dendogram for MLVA profiles and minimum spanning tree (MST) were drawn using the categorical coefficient calculated by BioNumerics software. A total of 23 MLVA types were identified in 215 SPA isolates and were grouped into six distinct cluster groups A, B, C, D, E and F. A total of 195 Yuxi SPA isolates were exclusively grouped into cluster C with nine MLVA genotypes. A total of 20 CMCC isolates were grouped in clusters A B, D, E and F with the other 14 MLVA types. The MLVA with nine VNTR loci, which was exploited in the present study, represents a successful strategy for genotyping SPA. Furthermore, the 195 Yuxi isolates appear to be closely related to each other and distinct from the 20 CMCC strains.
doi:10.3892/mmr.2014.2187
PMCID: PMC4068728  PMID: 24788795
Salmonella enterica serotype paratyphi A; multiple-locus variable number of tandem repeat analysis
5.  Genome-Wide Analyses of a Plant-Specific LIM-Domain Gene Family Implicate Its Evolutionary Role in Plant Diversification 
Genome Biology and Evolution  2014;6(4):1000-1012.
The Arabidopsis DA1 genes appear to have multiple functions in regulating organ size and abiotic stress response, but the biological roles of its closely related genes remain unknown. Evolutionary analyses might provide some clues to aid in an understanding of their functional diversification. In this work, we characterized the molecular evolution and expressional diversification of DA1-like genes. Surveying 354 sequenced genomes revealed 142 DA1-like genes only in plants, indicating plant-specificity of these genes. The DA1-like protein modular structure was composed of two UIMs (ubiquitin interaction motifs), one LIM-domain (from lin-11, isl-1, and mec-3), and a conserved C-terminal, and was distinguishable from the already defined three groups of LIM-domain proteins. We further found that the DA1-like genes diverged into Classes I and II at the ancestor of seed plants and acquired 13 clade-specific residues during their evolutionary history. Moreover, diverse intron size evolution was noted following the transition from size-expandable introns to minimal ones, accompanying the emergence and diversification of angiosperms. Functional diversification as it relates to gene expression was further investigated in soybean. Glycine max DA1 genes showed diverse tissues expression patterns during development and had substantially varied abiotic stress response expression. Thus, variations in the coding regions, intron size, and gene expression contributed to the functional diversification of this gene family. Our data suggest that the evolution of the DA1-like genes facilitated the development of diverse molecular and functional diversification patterns to accompany the successful radiation of plants into diverse environments during evolution.
doi:10.1093/gbe/evu076
PMCID: PMC4007552  PMID: 24723730
abiotic stress; gene expression; genome; LIM-domain; evolution; soybean
6.  The Prevalence and Molecular Spectrum of α- and β-Globin Gene Mutations in 14,332 Families of Guangdong Province, China 
PLoS ONE  2014;9(2):e89855.
Objective
To reveal the familial prevalence and molecular variation of α- and β-globin gene mutations in Guangdong Province.
Methods
A total of 40,808 blood samples from 14,332 families were obtained and analyzed for both hematological and molecular parameters.
Results
A high prevalence of α- and β-globin gene mutations was found. Overall, 17.70% of pregnant women, 15.94% of their husbands, 16.03% of neonates, and 16.83% of couples (pregnant women and their husbands) were heterozygous carriers of α- or β-thalassemia. The regions with the highest prevalence were the mountainous and western regions, followed by the Pearl River Delta; the region with the lowest prevalence was Chaoshan. The total familial carrier rate (both spouses were α- or β-thalassemia carriers) was 1.87%, and the individual carrier rates of α- and β-thalassemia were 1.68% and 0.20%, respectively. The total rate of moderate-to-severe fetal thalassemia was 12.78% among couples in which both parents were carriers.
Conclusions
There was a high prevalence of α- and β-thalassemia in Guangdong Province. This study will contribute to the development of thalassemia prevention and control strategies in Guangdong Province.
doi:10.1371/journal.pone.0089855
PMCID: PMC3937408  PMID: 24587075
7.  Mechanical characteristics of native tendon slices for tissue engineering scaffold 
The purpose of this study was to characterize the mechanical behavior of tendon slices with different thicknesses. Tendon slices of 100, 200, 300, 400, and 500 μm thickness were mechanically tested. The 300 μm slices were further tested for strength and modulus after 21,000-cycle fatigue testing under different applied strain levels (0, 1, 3, 5, 8, 10, and 12%). The tendon slice structure, morphology, and viability of bone marrow stromal cells (BMSCs) seeded onto the slices were also examined with histology, scanning electron microscopy, and vital cell labeling, respectively. Tendon slices 300 μm or more in thickness had similar ultimate tensile strength and Young's modulus to the intact tendon bundle. A strain of 5% or less did not cause any structural damage, nor did it change the mechanical properties of a 300 μm-thick tendon slice after 21,000-cycle fatigue testing. BMSCs were viable between and on the tendon slices after 2 weeks in tissue culture. This study demonstrated that, if tendon slices are used as a scaffold for tendon tissue engineering, slices 300 μm or more in thickness would be preferable from a mechanical strength point of view. If mechanical stimulation is performed for seeded-cell preparations, 5% strain or less would be appropriate.
doi:10.1002/jbm.b.32508
PMCID: PMC3911687  PMID: 22323314
tendon; slice; mechanical test; cell viability; fatigue
8.  Anterior and Posterior Variations in Mechanical Properties of Human Vertebrae Measured by Nanoindentation 
Journal of biomechanics  2012;46(3):456-461.
Osteoporotic spinal fractures are a significant global public health issue affecting more than 200 million people. Local degradation of the mechanical properties of bone and changes in global spine curvature increase fracture risk. However, a gap in knowledge exists relating material properties of trabecular bone in different regions of the spine. The purpose of our project was to measure the intrinsic mechanical properties of the anterior and posterior regions of human vertebral bodies in the thoracic and lumbar spine. Nanoindentation was used to evaluate Young’s modulus (E) and hardness (H) of anterior and posterior trabecular bone regions from each vertebra (T7, T8 and L4). One-way ANOVA and the Turkey-Kramer test were used to analyze significance between vertebrae and t-test was used to test for significance within vertebrae. There was no difference in (E) and (H) within vertebrae. Young’s modulus in the anterior regions of T7 (19.8 ± 1.3) and T8 (19.6 ± 1.4) were statistically greater than that in L4 (17.6 ± 0.5). There was no difference between the posterior regions of all vertebrae. There was a statistical significant difference in hardness between the anterior regions of T7 and T8 compared to L4, while the posterior regions demonstrated no difference. The results presented in this study, for the first time, reveal the differences in bone properties between the kyphotic thoracic spine and lordotic lumbar spine regions. This information will be helpful in understanding vertebral body remodeling and adaption in different regions of the spine which may be associated with spinal curvature and loading conditions.
doi:10.1016/j.jbiomech.2012.11.008
PMCID: PMC3552121  PMID: 23182219
Nanoindentation; Vertebrae; Trabecular bone; Stiffness; Regions
9.  Feasibility of Using Magnetic Resonance Elastography to Study the Effect of Aging on Shear Modulus of Skeletal Muscle 
A common complication associated with aging is the stiffening of skeletal muscles. The purpose of this study was to determine the ability of magnetic resonance elastography (MRE) to study this phenomenon in vivo. Twenty female subjects were included in the study with an age range of 50 to 70 years. Shear modulus was calculated for the tibialis anterior of each subject. There was not a significant relationship between age and shear modulus. However, three subjects had abnormally high values and were among the oldest subjects tested. There was a significant relationship between age and tissue stiffness homogeneity. More research is needed to determine whether the changes seen here are reflective of increased tissue cross-linking or related to reduced muscle quality. However, MRE shows promise as a tool to study aging-related muscle stiffness changes or to evaluate treatments to counteract these changes.
PMCID: PMC3904741  PMID: 19299834
advanced glycation end products; biomechanics; aging; MRE
10.  Wave attenuation as a measure of muscle quality as measured by magnetic resonance elastography: Initial results 
Journal of biomechanics  2009;42(4):537-540.
Advances in imaging technologies such as magnetic resonance elastography (MRE) have allowed researchers to gain insights into muscle function in vivo. MRE has been used to examine healthy and diseased muscle by calculating shear modulus. However, additional information can be measured from visualizing a mechanical wave as it passes through a tissue. One such measurable quantity is wave attenuation. The purpose of this study was to determine if a simple measure of wave attenuation could be used to distinguish between healthy and diseased muscle. Twenty seven subjects (14 healthy controls, 7 hyperthyroid myopathy patients, 6 myositis patients) participated in this study. Wave amplitude was determined along a linear profile through the center of the muscle, and an exponential decay curve was fit to the data. This measure was able to find significant differences in attenuation between healthy and diseased muscle. Furthermore, four hyperthyroid myopathy subjects who were tested following treatment all showed improvement by this measure. A likely reason for patients with hyperthyroid myopathy and myositis behaving similarly is that this measurement may reflect similar changes in the muscle extracellular matrix. In addition to modulus, attenuation seems to be an important parameter to measure in skeletal muscle. Further research is needed to investigate other potential measures of attenuation as well as examining other potential measures that can be found from visualizing wave propagation. Future studies should also include muscle biopsies to confirm that the changes seen are as a result of changes in extracellular matrix structure.
doi:10.1016/j.jbiomech.2008.11.034
PMCID: PMC3903001  PMID: 19171346
Biomechanics; MRE; Collagen; Extracellular matrix; Myositis; Hyperthyroid myopathy
11.  Histone deacetylase 3 is required for maintenance of bone mass during aging 
Bone  2012;52(1):296-307.
Histone deacetylase 3 (Hdac3) is a nuclear enzyme that removes acetyl groups from lysine residues in histones and other proteins to epigenetically regulate gene expression. Hdac3 interacts with bone-related transcription factors and co-factors such as Runx2 and Zfp521, and thus is poised to play a key role in the skeletal system. To understand the role of Hdac3 in osteoblasts and osteocytes, Hdac3 conditional knockout (CKO) mice were created with the Osteocalcin (OCN) promoter driving Cre expression. Hdac3 CKOOCN mice were of normal size and weight, but progressively lost trabecular and cortical bone mass with age. The Hdac3 CKOOCN mice exhibited reduced cortical bone mineralization and material properties and suffered frequent fractures. Bone resorption was lower, not higher, in the Hdac3 CKOOCN mice, suggesting that primary defects in osteoblasts caused the reduced bone mass. Indeed, reductions in bone formation were observed. Osteoblasts and osteocytes from Hdac3 CKOOCN mice showed increased DNA damage and reduced functional activity in vivo and in vitro. Thus, Hdac3 expression in osteoblasts and osteocytes is essential for bone maintenance during aging.
doi:10.1016/j.bone.2012.10.015
PMCID: PMC3513670  PMID: 23085085
Histone deacetylase; Osteocalcin-Cre; Osteoblast; Osteocyte; DNA damage
12.  Compressive properties of cd-HA-gelatin modified intrasynovial tendon allograft in canine model in vivo 
Journal of biomechanics  2011;44(9):1793-1796.
Although we sometimes use the intrasynovial tendon allograft as a donor, the gliding ability of allograft prepared by lyophilization is significantly decreased. The gliding ability of the grafted tendon after tendon reconstruction is very important because the high gliding resistance causes more adhesion and leads to poor clinical results. We recently revealed that tendon surface treatment with a carbodiimide derivatized HA (cd-HA)-gelatin mixture for intrasynovial tendon allograft significantly improved its gliding ability. The purpose of this study was to investigate whether this cd-HA-gelatin treatment affects the tendon mechanical property or not. A total of 40 flexor digitorum profundus (FDP) tendons from canines were evaluated for compressive property by using indentation test. Indentation stiffness was measured for normal tendon, rehydrated tendon after lyophilization, rehydrated tendon after lyophilization that was implanted 6 weeks in vivo, and cd-HA treated rehydrated tendon after lyophilization that was implanted 6 weeks in vivo. The results for all groups showed no significant difference in the tendon compressive properties. The findings of these results demonstrate that cd-HA treatment for intrasynovial tendon allograft is an excellent method to improve the tendon gliding ability after lyophilization without changing the compressive property of donor tendon.
doi:10.1016/j.jbiomech.2010.12.030
PMCID: PMC3625931  PMID: 21549380
Tendon graft; Allograft; Lyophilization; Mechanical property
13.  Assessment of stiffness changes in the ex vivo porcine aortic wall using magnetic resonance elastography 
Magnetic resonance imaging  2011;30(1):122-127.
Magnetic resonance elastography (MRE) is a noninvasive phase-contrast technique for estimating the mechanical properties of tissues by imaging propagating mechanical waves within the tissue. In this study, we hypothesize that changes in arterial wall stiffness, experimentally induced by formalin fixation, can be measured using MRE in ex vivo porcine aortas. In agreement with our hypothesis, the significant stiffness increase after sample fixation were clearly demonstrated by MRE and confirmed by mechanical testing. The results indicate that MRE can be used to examine the stiffness changes of the aorta. This study has provided evidence of the effectiveness of using MRE to directly assess the stiffness change in aortic wall. The results offer motivation to pursue MRE as a noninvasive method for the evaluation of arterial wall mechanical properties.
doi:10.1016/j.mri.2011.09.009
PMCID: PMC3238136  PMID: 22055848
MRI; Elastography; Aorta; Stiffness
14.  Shear elastic modulus estimation from indentation and SDUV on gelatin phantoms 
Tissue mechanical properties such as elasticity are linked to tissue pathology state. Several groups have proposed shear wave propagation speed to quantify tissue mechanical properties. It is well known that biological tissues are viscoelastic materials; therefore velocity dispersion resulting from material viscoelasticity is expected. A method called Shearwave Dispersion Ultrasound Vibrometry (SDUV) can be used to quantify tissue viscoelasticity by measuring dispersion of shear wave propagation speed. However, there is not a gold standard method for validation. In this study we present an independent validation method of shear elastic modulus estimation by SDUV in 3 gelatin phantoms of differing stiffness. In addition, the indentation measurements are compared to estimates of elasticity derived from shear wave group velocities. The shear elastic moduli from indentation were 1.16, 3.40 and 5.6 kPa for a 7, 10 and 15% gelatin phantom respectively. SDUV measurements were 1.61, 3.57 and 5.37 kPa for the gelatin phantoms respectively. Shear elastic moduli derived from shear wave group velocities were 1.78, 5.2 and 7.18 kPa for the gelatin phantoms respectively. The shear elastic modulus estimated from the SDUV, matched the elastic modulus measured by indentation. On the other hand, shear elastic modulus estimated by group velocity did not agree with indentation test estimations. These results suggest that shear elastic modulus estimation by group velocity will be bias when the medium being investigated is dispersive. Therefore a rheological model should be used in order to estimate mechanical properties of viscoelastic materials.
doi:10.1109/TBME.2011.2111419
PMCID: PMC3134144  PMID: 21317078
Indentation; SDUV; elasticity
15.  Evaluation of Muscles Affected by Myositis Using Magnetic Resonance Elastography 
Muscle & nerve  2011;43(4):585-590.
Introduction
Idiopathic inflammatory myopathies (IIM or myositis), is a group of autoimmune diseases that result in decreased muscle strength and/or endurance. Non-invasive tools to assess muscle may improve our understanding of the clinical and functional consequences of myopathies and their response to treatment. This study examined Magnetic Resonance Elastography (MRE), a non-invasive technique that assesses the shear modulus (stiffness) of muscle, in IIM subjects.
Methods
Nine subjects with active myositis completed the MRE protocol. Participants lay in a positioning device, and scans of the vastus medialis (VM) were taken in the relaxed state and at two contraction levels. Manual inversion was used to estimate the stiffness.
Results
A significant reduction in muscle stiffness was seen in myositis subjects compared with healthy controls during the ‘relaxed’ condition.
Discussion
The use of non-invasive technologies such as MRE may provide greater understanding of the pathophysiology of IIM and improve assessment of treatment efficacy.
doi:10.1002/mus.21923
PMCID: PMC3059125  PMID: 21319167
Muscle; Magnetic Resonance Elastography (MRE); Myositis; Muscle Stiffness; Noninvasive
16.  Crosslinking Characteristics and Mechanical Properties of an Injectable Biomaterial Composed of Polypropylene fumarate and Polycaprolactone Copolymer 
In this work, a series of copolymers of polypropylene fumarate-co-polycaprolactone (PPF-co-PCL) were synthesized via a three-step polycondensation reaction of oligomeric polypropylene fumarate (PPF) with polycaprolactone (PCL). The effects of PPF precursor molecular weight, PCL precursor molecular weight, and PCL fraction in the copolymer (PCL feed ratio) on the maximum crosslinking temperature, gelation time, and mechanical properties of the crosslinked copolymers were investigated. The maximum crosslinking temperature fell between 38.2±0.3 and 47.2±0.4 °C, which increased with increasing PCL precursor molecular weight. The gelation time was between 4.2±0.2 and 8.5±0.7 min, and decreased with increasing PCL precursor molecular weight. The compressive moduli ranged from 44±1.8 to 142±7.4 MPa, with enhanced moduli at higher PPF precursor molecular weight and lower PCL feed ratio. The compressive toughness was in the range of 4.1±0.3 and 17.1±1.3 KJ/m3. Our data suggest that the crosslinking and mechanical properties of PPF-co-PCL can be modulated by varying the composition. Therefore the PPF-co-PCL copolymers may offer increased versatility as an injectable, in situ polymerizable biomaterial than the individual polymers of PPF and PCL.
doi:10.1163/092050610X487765
PMCID: PMC3062160  PMID: 20566042
Polypropylene fumarate; polycaprolactone; injectable biomaterials; in situ polymerizable
17.  MEASUREMENT OF STIFFNESS CHANGES IN IMMOBILIZED MUSCLE USING MAGNETIC RESONANCE ELASTOGRAPHY 
Background
The isolated evaluation of changes in muscle following immobilization and disuse is a challenge in living subjects. The purpose of this study was to determine whether magnetic resonance elastography is capable of detecting these changes.
Methods
An animal model was created to produce a mild joint contracture following 42 days of one forelimb immobilization in a maximally flexed position with twice-daily passive exercise. Eight pairs of dog forelimbs were harvested. Magnetic resonance elastography scans were performed on the experimental limb in an extended elbow position with a torque of 0.6 Nm. Scans of the contralateral limb were performed in two conditions, position matching and torque matching. Furthermore, wet weight, cross sectional area, resting muscle length, and range of elbow joint motion were measured.
Findings
The muscle from the experimental limb showed significant reduction in muscle mass, cross sectional area, slack length, and range of elbow motion. When comparing limbs in position matching condition, the muscle lengths were similar, and the experimental muscle had a significantly higher shear modulus (79.1 (SD 12.0) kPa) than the contralateral muscle (31.9 (SD 24.4) kPa). When comparing limbs in torque matching conditions, the muscle strains were similar, and the experimental muscle had a significantly lower shear modulus than the contralateral muscle (113.0 (SD 24.8) kPa).
Interpretation
These findings suggest that following immobilization, magnetic resonance elastography has the potential to be used as a clinical tool to guide rehabilitation and as a research tool to study the loss of passive elastic components of muscle.
doi:10.1016/j.clinbiomech.2010.02.006
PMCID: PMC3042859  PMID: 20236744
Immobilized Muscle; Magnetic Resonance Elastography; Muscle Stiffness; Muscle Contracture; Muscle Atrophy
18.  The 2009 Frank Stinchfield Award: “Hip Squeaking”: A Biomechanical Study of Ceramic-on-ceramic Bearing Surfaces 
We designed and implemented an in vitro bench test to simulate and identify potential biomechanical causes for hip squeaking with alumina ceramic-on-ceramic bearing surfaces. All bearings were third-generation alumina ceramic with a 32-mm head coupled with a 56-mm acetabular component with a 32-mm ceramic insert. Conditions for testing were normal gait, high load, stripe wear, stripe wear in extreme load, metal transfer, edge wear with extreme load, and microfracture. Each condition was tested two times in dry conditions and two times in a lubricated condition with 25% bovine serum. Squeaking was reproduced in all dry conditions. It occurred quickly with high load, stripe wear, or metal transfer. Once squeaking occurred, it did not stop. Squeaking disappeared for all conditions when a small amount of lubricant was introduced. In lubricated conditions, squeaking was only reproduced for the material transfer condition. Our observations suggest squeaking is a problem of ceramic-ceramic lubrication and that this noise occurs when the film fluid between two surfaces is disrupted. Material (metal) transfer was the only condition that led to squeaking in a lubricated situation.
Electronic supplementary material
The online version of this article (doi:10.1007/s11999-009-0911-x) contains supplementary material, which is available to authorized users.
doi:10.1007/s11999-009-0911-x
PMCID: PMC2806975  PMID: 19543782
19.  Effect of Collagen Digestion on the Passive Elastic Properties of Diaphragm Muscle in Rat 
Medical engineering & physics  2009;32(1):90-94.
Effects of collagen digestion have been defined up to the fibril level. However, the question remains as to whether the alteration of skeletal muscle extracellular matrix (ECM) affects a muscle’s passive elastic response. Various elastography methods have been applied as tools for evaluating the mechanical properties and ECM content of skeletal muscle. In an effort to develop an ECM altered skeletal muscle model, this study determined the effect of collagen digestion on the passive elastic properties of skeletal muscle. Passive mechanical properties of rat diaphragms were evaluated in various degrees of collagen digestion. Between cyclic loading tests, muscle strips were immersed in various concentrations of clostridium histolyticum derived bacterial collagenase. All samples were later viewed via light microscopy. Cyclic testing revealed linear relationships between passive muscle stiffness and digestion time at multiple concentrations. These results demonstrate that collagenase digestion of the ECM in skeletal muscle could be used as a simple and reliable model of mechanically altered in vitro tissue samples.
doi:10.1016/j.medengphy.2009.11.002
PMCID: PMC2841476  PMID: 19945332
Extracellular matrix; biomechanics; myopathy; elastography
20.  Ability of Magnetic Resonance Elastography to Assess Taut Bands 
Background
Myofascial taut bands are central to diagnosis of myofascial pain. Despite their importance, we still lack either a laboratory test or imaging technique capable of objectively confirming either their nature or location. This study explores the ability of magnetic resonance elastography to localize and investigate the mechanical properties of myofascial taut bands on the basis of their effects on shear wave propagation.
Methods
This study was conducted in three phases. The first involved the imaging of taut bands in gel phantoms, the second a finite element modeling of the phantom experiment, and the third a preliminary evaluation involving eight human subjects-four of whom had, and four of whom did not have myofascial pain. Experiments were performed with a 1.5 Tesla magnetic resonance imaging scanner. Shear wave propagation was imaged and shear stiffness was reconstructed using matched filtering stiffness inversion algorithms.
Findings
The gel phantom imaging and finite element calculation experiments supported our hypothesis that taut bands can be imaged based on its outstanding shear stiffness. The preliminary human study showed a statistically significant 50-100% (p=0.01) increase of shear stiffness in the taut band regions of the involved subjects relative to that of the controls or in nearby uninvolved muscle.
Interpretation
This study suggests that magnetic resonance elastography may have a potential for objectively characterizing myofascial taut bands that have been up to now detectable only by the clinician's fingers.
doi:10.1016/j.clinbiomech.2007.12.002
PMCID: PMC2474796  PMID: 18206282
Magnetic Resonance Elastography; Myofascial Pain; Wave Propagation; Finite Element Modeling

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