Erosion of the foramen transversarium of the axis. Anatomical observations

Six hundred foramina transversaria (FT) of the axis vertebrae of 4 population groups were examined for the presence of erosion of the lateral articular mass. Of these, 127 (21%) and 72 (12%) presented with moderate and marked erosion, respectively. Evidence is presented incriminating the tortuosity of the vertebral artery as well as congenital factors in the etiology of the erosion of the FT. Attention is drawn to the possible correlation between angulation of the transverse process of the axis and erosion of the FT.     

Osteological and Soft-Tissue Evidence for Pneumatization in the Cervical Column of the Ostrich (Struthio camelus) and Observations on the Vertebral Columns of Non-Volant,Semi-Volant and Semi-Aquatic Birds

Postcranial skeletal pneumaticity (PSP) is a condition most notably found in birds, but that is also present in other saurischian dinosaurs and pterosaurs. In birds, skeletal pneumatization occurs where bones are penetrated by pneumatic diverticula, membranous extensions that originate from air sacs that serve in the ventilation of the lung. Key questions that remain to be addressed include further characterizing (1) the skeletal features that can be used to infer the presence/absence and extent of PSP in birds and non-avian dinosaurs, and (2) the association between vertebral laminae and specific components of the avian respiratory system. Previous work has used vertebral features such as pneumatic foramina, fossae, and laminae to identify/infer the presence of air sacs and diverticula, and to discuss the range of possible functions of such features. Here, we tabulate pneumatic features in the vertebral column of 11 avian taxa, including the flightless ratites and selected members of semi-volant and semi-aquatic Neornithes. We investigate the associations of these osteological features with each other and, in the case of Struthio camelus, with the specific presence of pneumatic diverticula. We find that the mere presence of vertebral laminae does not indicate the presence of skeletal pneumaticity, since laminae are not always associated with pneumatic foramina or fossae. Nevertheless, laminae are more strongly developed when adjacent to foramina or fossae. In addition, membranous air sac extensions and adjacent musculature share the same attachment points on the vertebrae, rendering the use of such features for reconstructing respiratory soft tissue features ambiguous. Finally, pneumatic diverticula attach to the margins of laminae, foramina, and/or fossae prior to their intraosseous course. Similarities in PSP distribution among the examined taxa are concordant with their phylogenetic interrelationships. The possible functions of PSP are discussed in brief, based upon variation in the extent of PSP between taxa with differing ecologies.     

Importance of the ribbon sign, indicating unsuitability of the vessel, in replanting a finger

A marked tortuosity of the digital arteries ("ribbon" sign) at the site of a digit amputation is a sign of a severe avulsion injury to the neurovascular bundles. When this finding is present, the artery should be resected and the gap bridged by a vein graft, if revascularization is attempted.     

Abnormal carotid arteries in the velocardiofacial syndrome: a report of three cases

Internal carotid arteries of unusual size and tortuosity were found before or at the time of pharyngeal flap surgery in three children who had the velocardiofacial syndrome with velopharyngeal insufficiency. In two cases, medial displacement of the arteries prevented surgery, and in the other, hypernasality persisted because only a narrow, asymmetrical flap could be raised. Medial displacement of the internal carotid arteries inhibits surgical treatment of velopharyngeal insufficiency, necessitating treatment with a prosthetic speech device in such children. Since displacement and tortuosity may be associated findings in the velocardiofacial syndrome, the exact location of the internal carotids should be ascertained when pharyngeal flap surgery is planned.     

Roentgeno-anatomy of the gastroduodenal artery

For the first time the data on clinical roentgenoanatomy of the functioning gastroduodenal artery and its branches are presented. It is based on analysis of vital angiograms performed in 607 persons (376 men and 213 women), in standard frontal and lateral projections. Certain roentgenological signs are described; they make it possible to distinguish the arteries from other vessels in the area. The data on topic position of the beginning of the arteries in regard to the vertebral column, depending on the sex of the examined persons, on direction, dimentions of the arteries, on their branches and on the character of their branching off are revealed. The data obtained could be useful in every day clinical practice of roenrgenoangiological rooms at making diagnosis and catheterization treatment of patients suffering from some pathology in the pancreatic-duodenal zone.     

The effect of collagenase on the critical buckling pressure of arteries

The stability of arteries is essential to normal arterial functions and loss of stability can lead to arterial tortuosity and kinking. Collagen is a main extracellular matrix component that modulates the mechanical properties of arteries and collagen degradation at pathological conditions weakens the mechanical strength of arteries. However, the effects of collagen degradation on the mechanical stability of arteries are unclear. The objective of this study was to investigate the effects of collagen degradation on the critical buckling pressure of arteries. Arterial specimens were subjected to pressurized inflation testing and fitted with nonlinear thick-walled cylindrical model equations to determine their stress strain relationships. The arteries were then tested for the critical buckling pressure at a set of axial stretch ratios. Then, arteries were divided into three groups and treated with Type III collagenase at three different concentrations (64, 128, and 400 U/ml). Mechanical properties and buckling pressures of the arteries were determined after collagenase treatment. Additionally, the theoretical buckling pressures were also determined using a buckling equation. Our results demonstrated that the buckling pressure of arteries was lower after collagenase treatment. The difference between pre- and post- treatment was statistically significant for the highest concentration of 400U/ml but not at the lower concentrations. The buckling equation was found to yield a fair estimation to the experimental critical pressure measurements. These results shed light on the role of matrix remodeling on the mechanical stability of arteries and developments of tortuous arteries.     

Postcranial pneumaticity: an evaluation of soft-tissue influences on the postcranial skeleton and the reconstruction of pulmonary anatomy in archosaurs

Postcranial pneumaticity has been reported in numerous extinct sauropsid groups including pterosaurs, birds, saurischian dinosaurs, and, most recently, both crurotarsan and basal archosauriform taxa. By comparison with extant birds, pneumatic features in fossils have formed the basis for anatomical inferences concerning pulmonary structure and function, in addition to higher-level inferences related to growth, metabolic rate, and thermoregulation. In this study, gross dissection, vascular and pulmonary injection, and serial sectioning were employed to assess the manner in which different soft tissues impart their signature on the axial skeleton in a sample of birds, crocodylians, and lizards. Results from this study indicate that only cortical foramina or communicating fossae connected with large internal chambers are reliable and consistent indicators of pneumatic invasion of bone. As both vasculature and pneumatic diverticula may produce foramina of similar sizes and shapes, cortical features alone do not necessarily indicate pneumaticity. Noncommunicating (blind) vertebral fossae prove least useful, as these structures are associated with many different soft-tissue systems. This Pneumaticity Profile (PP) was used to evaluate the major clades of extinct archosauriform taxa with purported postcranial pneumaticity. Unambiguous indicators of pneumaticity are present only in certain ornithodiran archosaurs (e.g., sauropod and theropod dinosaurs, pterosaurs). In contrast, the basal archosauriform Erythrosuchus africanus and other nonornithodiran archosaurs (e.g., parasuchians) fail to satisfy morphological criteria of the PP, namely, that internal cavities are absent within bone, even though blind fossae and/or cortical foramina are present on vertebral neural arches. An examination of regional pneumaticity in extant avians reveals remarkably consistent patterns of diverticular invasion of bone, and thus provides increased resolution for inferring specific components of the pulmonary air sac system in their nonavian theropod ancestors. By comparison with well-preserved exemplars from within Neotheropoda (e.g., Abelisauridae, Allosauroidea), the following pattern emerges: pneumaticity of cervical vertebrae and ribs suggests pneumatization by lateral vertebral diverticula of a cervical air sac system, with sacral pneumaticity indicating the presence of caudally expanding air sacs and/or diverticula. The identification of postcranial pneumaticity in extinct taxa minimally forms the basis for inferring a heterogeneous pulmonary system with distinct exchange and nonexchange (i.e., air sacs) regions. Combined with inferences supporting a rigid, dorsally fixed lung, osteological indicators of cervical and abdominal air sacs highlight the fundamental layout of a flow-through pulmonary apparatus in nonavian theropods.     

The Effect of Collagenase on the Critical Buckling Pressure of Arteries^*

The stability of arteries is essential to normal arterial functions and loss of stability can lead to arterial tortuosity and kinking. Collagen is a main extracellular matrix component that modulates the mechanical properties of arteries and collagen degradation at pathological conditions weakens the mechanical strength of arteries. However, the effects of collagen degradation on the mechanical stability of arteries are unclear. The objective of this study was to investigate the effects of collagen degradation on the critical buckling pressure of arteries. Arterial specimens were subjected to pressurized inflation testing and fitted with nonlinear thick-walled cylindrical model equations to determine their stress strain relationships. The arteries were then tested for the critical buckling pressure at a set of axial stretch ratios. Then, arteries were divided into three groups and treated with Type III collagenase at three different concentrations (64, 128, and 400U/ml). Mechanical properties and buckling pressures of the arteries were determined after collagenase treatment. Additionally, the theoretical buckling pressures were also determined using a buckling equation. Our results demonstrated that the buckling pressure of arteries was lower after collagenase treatment. The difference between pre- and post- treatment was statistically significant for the highest concentration of 400U/ml but not at the lower concentrations. The buckling equation was found to yield a fair estimation to the experimental critical pressure measurements. These results shed light on the role of matrix remodeling on the mechanical stability of arteries and developments of tortuous arteries.     

Numerical simulations of the blood flow through vertebral arteries

Vertebral arteries are two arteries whose structure and location in human body result in development of special flow conditions. For some of the arteries, one can observe a significant difference between flow rates in the left and the right arteries during ultrasonography diagnosis. Usually the reason of such a difference was connected with pathology of the artery in which a smaller flow rate was detected. Simulations of the flow through the selected type of the vertebral artery geometry for twenty five cases of artery diameters have been carried out. The main aim of the presented experiment was to visualize the flow in the region of vertebral arteries junction in the origin of the basilar artery. It is extremely difficult to examine this part of human circulation system, thus numerical experiments may be helpful in understanding the phenomena occurring when two relatively large arteries join together to form one vessel. The obtained results have shown that an individual configuration and diameters of particular arteries can exert an influence on the flow in them and affect a significant difference between flow rates for vertebral arteries. It has been assumed in the investigations that modelled arteries were absolutely normal, without any pathology. In the numerical experiment, the non-Newtonian model of blood was employed.     

The effect of Tyrophagus putrescentiae on Fusarium poae transmission and fungal community in stored barley in a laboratory experiment

The effect of Tyrophagus putrescentiae on Fusarium poae transmission and fungal community composition was studied in nonsterile barley grain. The experiments included following treatments： control barley without mites; barley containing l0 or 50 mites without preincubation on E poae （Tpl0 and TpS0）; barley containing 10 or 50 mites after preincubation on E poae （FTp 10 and FTp50）. The number of mites, suc cessful transfer of E poae, and changes in the fungal communities were examined after 21 d of experiment. Increase of deoxynivalenol （DON） content in the barley was chosen as a criterion of successful Epoae transfer. The preincubation of T. putrescentiae on Epoae increased DON level approximately to 800 and 300μg/kg of grain for FTpl0 and FTpS0, respectively. T. putrescentiae population growth in FTpl0 was lower than in Tpl0, while no difference was found between FTp50 and Tp50. Fungal communities were compared by amplification, cloning and sequencing of ITS fragments, and operational taxonomic units （OTU） analysis. The OTU analysis did not support the transfer ofF. poae via mites. From the analyzed clones, only 13 cloned sequences clustered with E poae in an OTU defined at distance level 0.07. The related clones originated from FTpl0, Tpl 0, Tp50 and control treatments, but not from FTp50. However, the presence of E poae in FTp50 was confirmed by PCR amplification with specific primers. The observation may be explained by different effect of mite population density, that is, in the high density, （FTp50 treatment） the fungus was overgrazed, while the lower population density （FTp 10） supported E poae transfer.     

The arterial supply of the thoracic and lumbar spine in newborns

The major arteries supplying the vertebral column are definite. The branching arteries of these trunks are variable. The posterior intercostal arteries and the lumbar arteries have an ascending, descending or horizontal course. In accordance with the literature, we found large, arched anastomoses between the rami ascendentes and the rami descendentes arising from the rami canalis vertebralis anteriores on the dorsal plane of the vertebral bodies. There are also nearly horizontal junctions between the rr. ascendentes of both sides. We found junctions on the front of the thoracolumbar vertebral column at the end of the arteries. On the dorsal plane of the vertebral body 2 arteriae centrales posteriores originate from the rr. ascendentes. They run to the centre of the vertebral body. On the ventrolateral plane of the vertebral body 2 or 3 aa. centrales anteriores can be found. These 4 or 5 arteries join in the middle of the vertebral body. The blood supply of the thoracal and lumbar vertebral bodies does not differ essentially. Vessels come especially from lateral in the intervertebral disc. We suggest to name such a vessel ramus disci intervertebralis. The posterior longitudinal ligament is mainly supplied by the junction between the rr. ascendentes of both sides and the anterior longitudinal ligament by the aa. nutriciae in the thoracal and the lumbar area.     

Lésion vertébrale froide en TEP/TDM au FNa-(18F) : n’oubliez pas l’ostéonécrose vertébrale (ou maladie de Kümmell) !

A 75-year-old woman presented with a history of severe backache and spinal cord compression syndrome. MRI revealed a well-circumscribed, homogeneous, wedge-shaped lesion involving T11 vertebral body, which was hypointense on T1- and hyperintense on T2-weighted images with bulging posterior border. Patient benefited from a decompressive T10–T12 laminectomy. Four months later, a new vertebral collapse of T10 was evidenced on plain X-rays. A second MRI exam displayed worrisome diffuse signal abnormalities of T10 pointing to a space-occupying lesion. A (18F)-NaF PET/CT was ordered and disclosed an hypometabolic (“cold”) activity of T10 and T11 vertebral bodies with a partial postero-lateral hypermetabolic rim. Twined low dose CT evidenced fracture sequelae and air-filled cleft within vertebral bodies. Histopathologic examination of the biopsy specimen of T10 revealed thinned out trabeculae surrounded by hyalinized fatty marrow cells and fibrovascular tissue, thus ascertaining the diagnosis of avascular necrosis of the vertebra. The radiographic and CT sine qua non for Kümmell's disease is intraosseous vacuum phenomenon. That is to say, vacuum clefts (VCs) of the vertebral bodies are radiographically recognized as a vacuum or air-filled cleft within the collapsed vertebrae. This sign is felt to be suggestive of ischemic necrosis but not specific as VCs of the vertebral bodies have also been associated with delayed union or non-union of osteoporotic fractures. Because of often misleading MRI abnormalities, integrative interpretation of (18F)-NaF PET/CT pattern should be undertaken in order to suspect Kümmell's disease and to discard some of the differentials.     

Calcium plays an important role in the regulation of hepatic branched-chain 2-oxo acid dehydrogenase activity

A fetal haemoglobin variant was noted in a healthy Jamaican infant of mixed African/Chinese extraction. A two-dimensional chromatogram of the soluble tryptic peptides (Tp) showed 2 ‘new’ ones/ One was composed of the last 4 residues of the usually insoluble Tpγ41–59. To permit a tryptic split this required a change of residue γ55 Met to Lys or Arg. The other new Tp contained arginine and was in the position expected for a Tpγ41–55 (55 Arg). As the material was limited it could not be analysed. When after more than 6 years no example of Hb F Kingston had become available it was decided to describe the variant on the basis of the present evidence.     

Differential susceptibility of cytotoxic and helper T cell precursors to neonatal tolerization to histocompatibility antigens

The ability of various (C57BL/6J X CBA/HT6T6)F1 spleen cell subpopulations to induce tolerance to allogeneic histocompatibility antigens after injection into neonatal CBA/HT6T6 mice was examined. The requirements for tolerization of cytotoxic T lymphocyte precursors (CTLp) and IL 2-producing helper T cell precursors (IL 2Tp) appear to be coordinated but not identical. CTLp frequencies measured in limiting dilution analysis (LDA) were found to be decreased by 90 to 99% in mice injected neonatally with unseparated or a variety of semiallogeneic spleen cell fractions, including T cells, T cell-depleted spleen, the Ig+ and Ig- fractions of nylon-adherent, T-depleted spleen cells, Sephadex-G10 (G10)-nonadherent spleen cells, and T-depleted allogeneic C57BL/6J spleen cells. In contrast, IL 2Tp showed tolerization only after neonatal injection of unseparated or T cell-depleted F1 spleen cells, and not after injection of T or B cells or of G10-nonadherent or T-depleted allogeneic spleen cells. These studies show that the CTLp and IL 2Tp compartments have different requirements for neonatal tolerization, which appear to correlate with the presence of cells expressing class I or class II alloantigens in the inoculum: all spleen cell types tested were capable of tolerizing the CTLp compartment, whereas only whole spleen and T-depleted spleen cells could tolerize IL 2Tp; donor T cells, although capable of inducing CTLp tolerance, are not necessary for either CTLp or IL 2Tp tolerance induction; Ig+ B cells alone are marginally effective in tolerization of IL 2Tp, and G10-nonadherent cells are ineffective, suggesting that macrophages or another type of G10-adherent accessory cell may be required for tolerization of IL 2Tp, although it is not clear whether they are sufficient; and tolerization of CTLp can occur in the presence of a normal IL 2Tp compartment when certain inocula, such as T cells, are used for tolerance induction at birth.     

Tissue distribution and biochemical and functional properties of Tp55 (CD27), a novel T cell differentiation antigen

Two monoclonal antibodies (CLB-CD 27/1 and CLB-CD 27/2) were raised against a novel determinant on human T lymphocytes. One of these antibodies, CLB-CD 27/1 (clone 9F4), was grouped by the Third International Workshop and Conference on Human Leucocyte Differentiation Antigens together with three other monoclonal antibodies (VIT 14, OKT 18A, and S152) in the new cluster CD27. In this paper we show that antibodies belonging to this cluster recognize an antigen present on a large subset of peripheral T lymphocytes and most medullary thymocytes. At least two different nonoverlapping epitopes were identified with directly labeled monoclonal antibodies. Immunoprecipitation studies indicate that the target antigen of CD27 antibodies is a polypeptide of 55 kDa, which appears in the form of a disulfide-linked homodimer on the T lymphocyte membrane (Tp55). Stimulation of T cells via the T3/T cell antigen-receptor complex, with either phytohemagglutinin or CD3 monoclonal antibodies, resulted in a fivefold increase in the membrane expression of Tp55, whereas activation by phorbol myristate acetate caused a marked down-regulation. Moreover, an additional molecule of 32 kDa was precipitated from the membrane of activated but not of resting T cells. Addition of CD27 antibodies to cultures stimulated with either phytohemagglutinin or CD3 monoclonal antibody led to enhanced proliferation, whereas no effect was observed in phorbol myristate acetate or interleukin 2-stimulated cultures. The possible role of the Tp55 antigen in T cell activation is discussed.     

Inotropic effect of hyperosmotic NaCl solutions on the isolated rat cardiac tissue.

The inotropic effect of Krebs-Henseleit solution rendered hyperosmotic by addition of NaCl or sucrose (increments of 50, 100, 150 and 200 mOsm/l) on myocardial contractile activity was studied in rat isolated left atria paced at 4, 16 and 64 stim/min. The solutions did not affect the peak tension (Tp) at 4 stim/min, whereas sucrose caused a dose-dependent increase in Tp at 16 stim/min and NaCl decreased Tp at 64 stim/min. The total time duration of the contraction was increased in a dose-dependent fashion by both solutes, but the effect of NaCl was attenuated at 64 stim/min. The results showed that, in the isolated rat atrial tissue exposed to hyperosmotic NaCl solutions, the negative inotropic effect of increased Na+ concentration overcomes the positive influence of hyperosmolality only at higher pacing rates (about 1 Hz).     

On the subclavian steal syndrome in vitro studies.

An elastic model of the arterial system has been used in which a specially designed pumping unit simulated the heart action. Physiological pressures and normal geometry, size, and flow distribution together with the normal cardiac output and use of prosthetic heart valves are the features of the system. Atherosclerosis was simulated by introducing blockages of known cross-section at specific sites of predilection. It has been shown that, for some specific occlusion magnitude in the left or right subclavian, or in the brachycephalic arteries, the stagnant no blood flow condition will appear in the left vertebral, or the right vertebral, or right common carotid, or the right internal carotid arteries. For larger occlusions the blood flow in these arteries reverses its direction, i.e., the "steal syndrome" appears. It is shown that besides the known single steal syndrome there exists also a double steal syndrome, i.e., blood reverses its flow direction simultaneously in two arteries, both on the right side of the arterial system. This blood is taken from the circle of Willis, which at the same time is significantly supplemented by the increased blood flow through the other arteries leading into the circle of Willis.     

Atrial septation: I. Scanning electron microscopy in the chick

Chick hearts were prepared for scanning electron microscopy by standard methods, the purpose being to investigate the surface morphology of the developing atrial septal region. By Day 3, the atrial septum primum appeared as a sickle-shaped structure. During Day 4, the first representation of the foramina secunda occurred in the mid-dorsal portion of the septum. During Day 5, the septum primum fused with the atrioventricular endocardial cushions, thereby occluding the foramen primum. From Days 5 through 8, the secondary perforations (foramina secunda) multiplied and increased in size. The endocardial-covered cords of cells comprising the septum thickened from Days 9 through 15. This resulted in a marked reduction in the dimensions of the perforations from Day 16 to hatching. The atrial septum at hatching occasionally contained a small single orifice. At 3 days posthatching, the atrial septum was a solid sheet covered with flattened endocardial cells. All interatrial communications were occluded. During Days 5 through 9, two distinct cell types became apparent on the endocardial-covered cords. Simultaneously, fenestrations were observed on the cords surrounding the foramina secunda and on the ventral portion of the atrial septum. The integral role which the fenestrations and cellular types play in the development of the formina secunda is discussed.     

The arterial supply of the cervical vertebral body in newborns

The cervical vertebral column is mainly supplied by both vertebral arteries. A regular ladder pattern of arteries is on the dorsal plane as well as on the ventral plane of the cervical vertebral bodies, opposite to the thoracal and the lumbar area of the vertebral column with only a dorsal ladder pattern of arteries. The cervical arterial anastomoses are built by the segmental arteries of the vertebral arteries, in the back of the cervical vertebral bodies by the arteriae canalis vertebralis anteriores and in the front by the rami anteriores (corporum vertebrarum). The thyrocervical and the costocervical trunks are an additional blood supply especially to the ventral anastomoses. A loss of a segmental artery may have no effect because of the good anastomoses. Some decades of aa. nutriciae come in the vertebral body from all sides, but only 2 up to 4 rr. centrales anteriores and 2 rr. centrales posteriores join in the middle of the vertebral body. There are parallels to the arterial blood supply of the thoracal and the lumbar vertebral bodies. The longitudinal ligaments are supplied by both ladder patterns of arteries.     

Genetics and bone. Using the mouse to understand man

The rationale for use of inbred strains of mice in bone research is well recognized and includes: a) practical factors (economics of scale, rapid development of adult status, pre-existing knowledge, down-sized technologies) and b) proven methodologies for genetic studies (polygenic trait analyses, mapping tools, genomic sequencing, methods for gene manipulation). Initial investigations of inbred strains of mice showed that femoral and lumbar vertebral volumetric bone mineral density (BMD, mg/mm(3)) by pQCT varied in excess of 50% for femurs and 9% in vertebral BMD. Two strains - low BMD C57BL/6J (B6) mice and high BMD C3H/HeJ (C3H) - were investigated for insights to their BMD diversity. B6C3F2 females derived from intercrossing B6C3F1s were raised to adult skeletal status at 4 months, then necropsied for phenotyping of bone and genotyping of genomic DNA. 1000 F2 females were genotyped for PCR product polymorphisms on all 19 autosomes at approximately 15 cM. Genome wide analyses for genotype-phenotype correlations showed 10 chromosomes (Chrs) carried genes for femoral and 7 Chrs for vertebral BMD. LOD scores ranged from 2.90 to 24.4, and percent of F2 variance accounted for ranged from 1 to 10%. Analyses of main effects revealed both dominant-recessive and additive inheritance patterns. Both progenitor strains carried alleles with positive and negative effects on BMD of each bone sites. A remarkable array of additonal skeletal phenotypes (femur and vertebral geometry, strength measures, serum markers) also proved polygenic in nature, with complex segregation patterns. Verification of BMD quantitative trait loci (QTLs) was undertaken by creating congenic B6 strains carrying individual QTL regions from C3H. Following 6 cycles of backcrossing a QTL-containing region from C3H to the B6 strain, N6F2 congenic strain mice were aged to 4 months, then genotyped for the QTL region and phenotyped for skeletal traits. Comparison of mice homozygous for C3H alleles versus homozygous for B6 alleles in the QTL regions showed that femoral BMD increased or decreased significantly in congenic strains, as was predicted from F2 data. Gender differences specific to BMD QTLs have been revealed, as have more than 30 additional phenotypes associated with cortical and trabecular structural parameters and biomechanical properties.