The vascular territories (angiosomes) of the body: experimental study and clinical applications

The blood supply to the skin and underlying tissues was investigated by ink injection studies, dissection, perforator mapping and radiographic analysis of fresh cadavers and isolated limbs. The results were correlated with previous regional studies done in this department. The blood supply is shown to be a continuous three-dimensional network of vessels not only in the skin but in all tissue layers. The anatomical territory of a source artery in the skin and deep tissues was found to correspond in most cases, giving rise to the angiosome concept. Arteries follow closely the connective tissue framework of the body. The primary supply to the skin is by direct cutaneous arteries which vary in calibre, length and density in different regions. This primary supply is reinforced by numerous small indirect vessels, which are "spent" terminal branches of arteries supplying the deep tissues. An average of 374 major perforators was plotted in each subject, revealing that there are still many more potential skin flaps. Our arterial roadmap of the body provides the basis for the logical planning of incisions and flaps. The angiosomes defined the tissues available for composite transfer.

Structure of the tendon connective tissue

Tendons consist of collagen (mostly type I collagen) and elastin embedded in a proteoglycan-water matrix with collagen accounting for 65-80% and elastin approximately 1-2% of the dry mass of the tendon. These elements are produced by tenoblasts and tenocytes, which are the elongated fibroblasts and fibrocytes that lie between the collagen fibers, and are organized in a complex hierarchical scheme to form the tendon proper. Soluble tropocollagen molecules form cross-links to create insoluble collagen molecules which then aggregate progressively into microfibrils and then into electronmicroscopically clearly visible units, the collagen fibrils. A bunch of collagen fibrils forms a collagen fiber, which is the basic unit of a tendon. A fine sheath of connective tissue called endotenon invests each collagen fiber and binds fibers together. A bunch of collagen fibers forms a primary fiber bundle, and a group of primary fiber bundles forms a secondary fiber bundle. A group of secondary fiber bundles, in turn, forms a tertiary bundle, and the tertiary bundles make up the tendon. The entire tendon is surrounded by a fine connective tissue sheath called epitenon. The three-dimensional ultrastructure of tendon fibers and fiber bundles is complex. Within one collagen fiber, the fibrils are oriented not only longitudinally but also transversely and horizontally. The longitudinal fibers do not run only parallel but also cross each other, forming spirals. Some of the individual fibrils and fibril groups form spiral-type plaits. The basic function of the tendon is to transmit the force created by the muscle to the bone, and, in this way, make joint movement possible. The complex macro- and microstructure of tendons and tendon fibers make this possible. During various phases of movements, the tendons are exposed not only to longitudinal but also to transversal and rotational forces. In addition, they must be prepared to withstand direct contusions and pressures. The above-described three-dimensional internal structure of the fibers forms a buffer medium against forces of various directions, thus preventing damage and disconnection of the fibers.

Anatomic aspects of vaginal eversion after hysterectomy

OBJECTIVE

Our aim was to understand how vaginal eversion after hysterectomy differs from other forms of prolapse.

STUDY DESIGN

The role of individual structures involved in vaginal support was studied by pelvic dissection of 61 cadavers. Serial cross sections from 13 additional cadavers were examined.

RESULTS

The upper third of the vagina (level I) is suspended from the pelvic walls by vertical fibers of the paracolpium, which is a continuation of the cardinal ligament. In the middle third of the vagina (level II) the paracolpium attaches the vagina laterally to the arcus tendineus and fascia of the levator ani muscles. The vagina's lower third fuses with the perineal membrane, levator ani muscles, and perineal body (level III). Dissection reveals that the paracolpium's vertical fibers in level I prevented prolapse of the vaginal apex and vaginal eversion.

CONCLUSIONS

The paracolpium in level I forms the critical factor that differentiates vaginal eversion from posthysterectomy cystocele-rectocele or enterocele in which the vaginal apex remains well suspended.

New attachment formation in the human periodontium by guided tissue regeneration. Case reports

The aim of the present study was to evaluate whether a regenerative surgical procedure, based on guided tissue regeneration, could predictably result in the formation of a new attachment in human teeth. The material included 12 teeth in 10 patients with advanced periodontal disease. Following flap elevation, scaling, root planing and removal of granulation tissue, a teflon membrane was placed over the denuded root surface in such a way that the epithelium and the gingival connective tissue were prevented from reaching contact with the root during healing. The flap was replaced on the outer surface of the membrane and secured with interdental sutures. This design of wound preparation gives preference to the cells originating from the periodontal ligament (PDL-cells) to repopulate the wound area adjacent to the root. Histologic analysis of the result of treatment was made in 5 of the 12 teeth scheduled for extraction. In the remaining 7 teeth, the result was evaluated using clinical measurements. The result of healing disclosed that in all teeth treated, substantial amounts of new attachment had formed. This suggests that predictable restitution of the attachment apparatus can be accomplished by using a method of treatment which is based on the principle of guided tissue regeneration.

A comparison of the quantitative anatomy of the bronchi in normal subjects, in status asthmaticus, in chronic bronchitis, and in emphysema

The quantitative anatomy of the bronchi has been studied in sudden deaths in normal subjects, in deaths from status asthmaticus and chronic bronchitis, and in patients with emphysema. In the normal bronchi the observed range of values for the percentage volume of mucous glands was between 7·6 and 16·7. In the status asthmaticus group the mucous gland volume was greatly increased and in no case was there an overlap with the normal subjects. In the 19 cases of chronic bronchitis, two cases had values of 15·2 and 15·4% respectively, but all the others had values higher than the normal range and, in two instances, values of over 40% were obtained. The values obtained for mucous gland volume in the bronchi in emphysema were variable, approximately half being within the normal range. The bronchial smooth muscle accounted for 4·6±2·2% of the volume of the normal bronchial wall. The values obtained in chronic bronchitis and emphysema did not differ significantly from this but in those dying of status asthmaticus there was a very significant increase with a mean value of 11·9±3·36.

Human aging, muscle mass, and fiber type composition

To assess the age-related loss of muscle mass and to determine the mechanisms behind this aging atrophy, the muscle structure and fiber type composition have been estimated, using invasive and noninvasive techniques. Limb muscles from older men and women are 25-35% smaller and have significantly more fat and connective tissue than limb muscles from younger individuals. Comparisons of muscle biopsies from younger and older individuals reveal that type 2 (fast-twitch) fibers are smaller in the old, while the size of type 1 (slow-twitch) fibers is much less affected. Studies of whole muscle cross sections also show a significantly smaller number of muscle fibers, a significantly lower relative type 2 fiber area, and a significant increase in fiber type grouping with increasing age. These results indicate a gradual decrease in size/volume with advancing age, accompanied by a replacement by fat and connective tissue. This aging atrophy seems to be due to a reduction in both number and size of muscle fibers, mainly of type 2, and is to some extent caused by a slowly progressive neurogenic process.

The sinoatrial node, a heterogeneous pacemaker structure

This article focuses on the regional heterogeneity of the mammalian sinoatrial (SA) node in terms of cell morphology, pacemaker activity, action potential configuration and conduction, densities of ionic currents (i(Na), i(Ca,L), i(to), i(K,r), i(K,s) and i(f)), expression of gap junction proteins (Cx40, Cx43 and Cx45), autonomic regulation, and ageing. Experimental studies on the single SA node cell to the whole animal are reviewed. The heterogeneity is considered in terms of the gradient model of the SA node, in which there is gradual change in the intrinsic properties of SA node cells from periphery to centre, and the alternative mosaic model, in which there is a variable mix of atrial and SA node cells from periphery to centre. The heterogeneity is important for the dependable functioning of the SA node as the pacemaker for the heart, because (i) via multiple mechanisms, it allows the SA node to drive the surrounding atrial muscle without being suppressed electrotonically; (ii) via an action potential duration gradient and a conduction block zone, it promotes antegrade propagation of excitation from the SA node to the right atrium and prevents reentry of excitation; and (iii) via pacemaker shift, it allows pacemaking to continue under diverse pathophysiological circumstances.

Effects of mechanical factors on the fracture healing process

An interdisciplinary study based on animal experiments, cell culture studies, and finite element models is presented. In a sheep model, the influence of the osteotomy gap size and interfragmentary motion on the healing success was investigated. Increasing gap sizes delayed the healing process. Increasing movement stimulated callus formation but not tissue quality. Typical distributions of intramembranous bone, endochondral ossification, and connective tissue in the fracture gap are quantified. The comparison of the mechanical data determined by a finite element model with the histologic images allowed the attribution of certain mechanical conditions to the type of tissue differentiation. Intramembranous bone formation was found for strains smaller than approximately 5% and small hydrostatic pressure (< 0.15 MPa). Strains less than 15% and hydrostatic pressure more than 0.15 MPa stimulated endochondral ossification. Larger strains led to connective tissue. Cell culture studies on the influence of strain on osteoblasts supported these findings. Proliferation and transforming growth factor beta production was increased for strains up to 5% but decreased for larger strains. Osteoblasts under larger strains (> 4%) turned away from the principal strain axis and avoided larger deformations. It is hypothesized that gap size and the amount of strain and hydrostatic pressure along the calcified surface in the fracture gap are the fundamental mechanical factors involved in bone healing.

Constitutive equations for fibrous connective tissues

A general multiaxial theory for the constitutive relations in fibrous connective tissues is developed on the basis of microstructural and thermodynamic considerations. It is compatible with existing general material theories. In elastic tissues, the theory considers the strain-energy function to be the sum of strain-energies of the tissue's components. The stresses are derived from this strain-energy function. Viscoelastic constitutive relations are obtained in an analogous manner. Few examples are developed in detail. The results of the present strain-energy based theory are identical with those of the author's previous structural models (Lanir, 1979a, b) which are based on detailed equilibrium analysis. It turns out, however, that the analytical work involved in solving boundary value problems is considerably shorter if the present theory is used. The advantages of structural theories in avoiding ambiguity in material characterization and in offering an insight into the function, structure and mechanics of tissue components are discussed.

Laminar structure of the heart: ventricular myocyte arrangement and connective tissue architecture in the dog

We have studied the three-dimensional arrangement of ventricular muscle cells and the associated extracellular connective tissue matrix in dog hearts. Four hearts were potassium-arrested, excised, and perfusion-fixed at zero transmural pressure. Full-thickness segments were cut from the right and left ventricular walls at a series of precisely located sites. Morphology was visualized macroscopically and with scanning electron microscopy in 1) transmural planes of section and 2) planes tangential to the epicardial surface. The appearance of all specimens was consistent with an ordered laminar arrangement of myocytes with extensive cleavage planes between muscle layers. These planes ran radially from endocardium toward epicardium in transmural section and coincided with the local muscle fiber orientation in tangential section. Stereological techniques were used to quantify aspects of this organization. There was no consistent variation in the cellular organization of muscle layers (48.4 +/- 20.4 microns thick and 4 +/- 2 myocytes across) transmurally or in different ventricular regions (23 sites in 6 segments), but there was significant transmural variation in the coupling between adjacent layers. The number of branches between layers decreased twofold from subepicardium to midwall, whereas the length distribution of perimysial collagen fibers connecting muscle layers was greatest in the midwall. We conclude that ventricular myocardium is not a uniformly branching continuum but a laminar hierarchy in which it is possible to identify three axes of material symmetry at any point.

Needle insertion into soft tissue: a survey

Needle insertion in soft tissue has attracted considerable attention in recent years due to its application in minimally invasive percutaneous procedures such as biopsies and brachytherapy. This paper presents a survey of the current state of research on needle insertion in soft tissue. It examines the topic from several aspects, e.g. modeling needle insertion forces, modeling tissue deformation and needle deflection during insertion, robot-assisted needle insertion, and the effect of different trajectories on tissue deformation. All studies show that the axial force of a needle during insertion in soft tissue is the summation of different forces distributed along the needle shaft such as stiffness force, frictional force and cutting force. Some studies have modeled these forces. The force data in some procedures is used for identifying tissue layers as the needle is inserted or for path planning. Needle deflection and tissue deformation are major problems for accurate needle insertion and attempts have been made to model them. Using current models several insertion techniques have been developed which are briefly reviewed in this paper.

The involution of the ageing human thymic epithelium is independent of puberty. A morphometric study

One hundred and thirty-six thymuses completely removed at autopsy from persons suffering a sudden death were examined by stereological and morphometrical methods. Adding biopsy material from immunologically healthy cardiac patients we obtained relative volumes from 204 persons ranging in age from 1 month to 107 years. The size of the human thymus remains unchanged during ageing under normal physiological conditions (median: 19.5 cm3). Individual maximum size (range: 5-70 cm3) is reached in the first year of life. Early histological changes are in the enlargement of the perivascular space, the Hassall's bodies, and the connective tissue. This begins in the first year of life, reaches a maximum from 10 to 25 years, then declines again. Adipose tissue replaces the lymphocytic perivascular space and the connective tissue only. This occurs extensively after the age of 15 years. When defined by the silver impregnation technique, the volumes of the thymic epithelium (cortex and medulla), show a continuous involution from the first year to the end of life. The curve can be approximated to simple negative logarithmic functions. The velocity and nature of involution of the thymic epithelium do not change under the influence of the changing hormonal balance due to puberty. Since important thymic functions (T lymphopoiesis and T-cell differentiation) are located in the epithelial space, the age-related involution of the human thymus is not related to puberty.

The reactions of bone, connective tissue, and epithelium to endosteal implants with titanium-sprayed surfaces

The results of a research project which has been under way for the last 7 years are reported. The project has been centred around a series of animal (monkey) experiments designed to test the suitability of cylindrical titanium implants with titanium-sprayed surfaces. The following results have been obtained: 1. The bone applies itself "ankylotically" (i.e. without an intervening layer of connective tissue) to the surface of the implant and, as revealed by observation over periods of up to 1 3/4 years, even remains attached to the implant surface when placed under load. 2. The fibres of the connective tissue between the bone and the epithelium insert into the titanium-sprayed surface and appear to be functionally orientated. 3. If the post of the implant is situated in a region of immobile, keratinized mucosa signs of adhesion of the epithelial cells to the titanium-sprayed surface become apparent. 4. The clinical success of the implant is clearly dependent on (a) the presence of tethered, immobile mucosa ("gingiva") around the post of the implant, and (b) perfect oral hygiene.

Palatal growth studied on human autopsy material. A histologic microradiographic study

The postnatal development of the hard palate was studied by conventional histologic and microradiographic means on autopsy material from thirty-three boys and twenty-seven girls aged 0 to 18 years. The findings indicated thet growth in length of the hard palate until the age of 13 to 15 was due to growth in the transverse suture and to apposition on the posterior margin of the palate. After this age the sutural growth was found to cease, whereas the apposition seemed to continue for some years. During the postnatal development the morphology of the transverse suture changed. At birth the suture was broad and slightly sinuous; later it developed into a typical squamous suture, the palatine part covering the maxillary part. During puberty the course of the suture was again slightly sinuous. The importance of this change for the vertical growth of the hard palate was discusses. It was pointed out that the lowering of the anterior part of the palate. The transverse growth of the midpalatal suture continued up to tha age of 16 in girls and 18 in boys. On the basis of morphology, the development of the median suture could be divided into three stages. In the first stage the suture was short, broad, and Y shaped; in the second the course was more sinuous; and in the third interdigitation was so heavy that a separation of the two halves of the maxilla would not be possible without fracturing the interdigitated processes.

Relationship of acupuncture points and meridians to connective tissue planes

Acupuncture meridians traditionally are believed to constitute channels connecting the surface of the body to internal organs. We hypothesize that the network of acupuncture points and meridians can be viewed as a representation of the network formed by interstitial connective tissue. This hypothesis is supported by ultrasound images showing connective tissue cleavage planes at acupuncture points in normal human subjects. To test this hypothesis, we mapped acupuncture points in serial gross anatomical sections through the human arm. We found an 80% correspondence between the sites of acupuncture points and the location of intermuscular or intramuscular connective tissue planes in postmortem tissue sections. We propose that the anatomical relationship of acupuncture points and meridians to connective tissue planes is relevant to acupuncture's mechanism of action and suggests a potentially important integrative role for interstitial connective tissue.

Tissue response to mechanical vibrations for "sonoelasticity imaging"

The goal of "sonoelasticity imaging" is to differentiate between normal soft tissues and hard lesions. This is done by measuring and then displaying the ultrasound Doppler spectrum of regions within tissues which are mechanically forced with low frequency (20-1000 Hz) vibrations. The resolution and sensitivity of the technique ultimately rest on the spatial resolution of ultrasound Doppler detection, the low frequency mechanical properties of tissues, and the vibration response of layered, inhomogeneous regions with hard tumor inclusions and complicated boundary conditions set by the presence of skin, bones and other regions. An initial investigation has measured some tissue stiffness parameters, and applied these in a NASTRAN finite element analysis to simulate a prostate tumor in the pelvic cavity. The measurements show a wide separation between the elastic modulus of tumors and soft tissues such as muscle and prostate. NASTRAN analyses show the ability to delineate regions of different elasticity based on the pattern of vibration amplitudes. The ability to change vibration frequency within the 100-300 Hz band seems particularly helpful in simulations and experiments which visualize small stiff inclusions in tissues. Preliminary results support the postulate that sonoelasticity imaging can provide useful information concerning tissue properties that are not otherwise obtainable.

Mechanical signaling through connective tissue: a mechanism for the therapeutic effect of acupuncture

The mechanism of action of acupuncture remains largely unknown. The reaction to acupuncture needling known as 'de qi', widely viewed as essential to the therapeutic effect of acupuncture, may be a key to understanding its mechanism of action. De qi includes a characteristic needling sensation, perceived by the patient, and 'needle grasp' perceived by the acupuncturist. During needle grasp, the acupuncturist feels pulling and increased resistance to further movement of the inserted needle. We hypothesize that 1) needle grasp is due to mechanical coupling between the needle and connective tissue with winding of tissue around the needle during needle rotation and 2) needle manipulation transmits a mechanical signal to connective tissue cells via mechanotransduction. Such a mechanism may explain local and remote, as well as long-term effects of acupuncture.

Anatomy of the anterior cruciate ligament with regard to its two bundles

The anterior cruciate ligament (ACL) consists of two major fiber bundles, namely the anteromedial and posterolateral bundle. When the knee is extended, the posterolateral bundle (PL) is tight and the anteromedial (AM) bundle is moderately lax. As the knee is flexed, the femoral attachment of the ACL becomes a more horizontal orientation; causing the AM bundle to tighten and the PL bundle to relax. There is some degree of variability for the femoral origin of the anterome-dial and posterolateral bundle. The anteromedial bundle is located proximal and anterior in the femoral ACL origin (high and deep in the notch when the knee is flexed at 90 degrees ); the posterolateral bundle starts in the distal and posterior aspect of the femoral ACL origin (shallow and low when the knee is flexed at 90 degrees ). In the frontal plane the anteromedial bundle origin is in the 10:30 clock position and the postero-lateral bundle origin in the 9:30 clock position. At the tibial insertion the ACL fans out to form the foot region. The anteromedial bundle insertion is in the anterior part of the tibial ACL footprint, the posterolateral bundle in the posterior part. While the anteromedial bundle is the primary restraint against anterior tibial translation, the posterolateral bundle tends to stabilize the knee near full extension, particularly against rotatory loads.

Histometric evaluation of periodontal surgery. II. Connective tissue attachment levels after four regenerative procedures

The present study was undertaken to determine the effect of four periodontal regenerative procedures on the connective tissue attachment level. The procedures tested were: 1) the modified Widman flap procedure, 2) the modified Widman flap procedure combined with transplantation of previously frozen autogenous red marrow and cancellous bone, 3) the modified Widman flap procedure in combination with implantation of beta tricalcium phosphate, and 4) periodic root planing and soft tissue curettage. Eight adult Rhesus monkeys, divided into four equal groups, were used. Periodontal pockets were produced around contralateral teeth in a standardized manner. In each group of animals, the pockets on one side of the jaws were subjected to one of the above-mentioned surgical treatments, while the contralateral pockets remained as unoperated controls. Three weeks before surgery, a carefully designed plaque control program was instituted and continued until the animals were sacrificed 12 months after surgery. In histologic sections, linear measurements along the root surfaces were made from the cemento-enamel junction (CEJ) to the most apical cells of the junctional epithelium (JE). These measurements from operated and unoperated sites were then compared. The data revealed that healing following the four different regenerative procedures resulted in the reformation of an epithelial lining (long junctional epithelium) along the treated root surfaces, with no new connective tissue attachment.

The nonlinear characteristics of soft gels and hydrated connective tissues in ultrafiltration

A one-dimensional ultrafiltration problem of fluid flow through a soft permeable tissue or gel under high pressure and compressive strain is solved. A finite deformation biphasic theory is used to model the behavior of the soft porous permeable solid matrix. This theory includes a Helmholtz free energy function which depends on the three principal invariants (I, II, III) of the right Cauchy-Green tensor and which satisfies the Baker-Ericksen inequalities on the principal stresses and strains. The dependence of the porosity phi f and the solidity phi s on deformation is deduced and a generalization of the exponential strain-dependent functional form for the permeability, k = k0 exp (M epsilon), of Lai and Mow (Biorheology 103, 111-123, 1980) is proposed. In this one-dimensional problem, we show that the dependence of the permeability on phi f, phi s, and III is equivalent to its dependence on hydration as proposed by Fatt and Goldstick (J. Colloid Sci. 20, 962-988, 1965). The exact solution of the ultrafiltration problem is derived and asymptotic and numerical methods are used to evaluate it. For high pressures and finite strains, the solution provides some surprising effects. The theory predicts that a material starting with a homogeneous porosity will have a strongly non-homogeneous porosity throughout the column during ultrafiltration. The resulting change in pore size through the filtration column may be very important in understanding its filtration characteristics. It is also found that there is a long delay time, up to 10 to 15 min, before the filtration velocity reaches an equilibrium. In filtration experiments where the rate of mass transport across the tissue or column of gel is important, sufficient time must be allowed for the steady state to be reached.

Functional morphology and homology in the odontocete nasal complex: implications for sound generation

The site and physiologic mechanism(s) responsible for the generation of odontocete biosonar signals have eluded investigators for decades. To address these issues we subjected postmortem toothed whale heads to interrogation using medical imaging techniques. Most of the 40 specimens (from 19 species) were examined using x-ray computed tomography (CT) and/or magnetic resonance imaging (MR). Interpretation of scan images was aided by subsequent dissection of the specimens or, in one case, by cryosectioning. In all specimens we described a similar tissue complex and identified it as the hypothetical biosonar signal generator. This complex includes a small pair of fatty bursae embedded in a pair of connective tissue lips, a cartilaginous blade, a stout ligament, and an array of soft tissue air sacs. Comparing and contrasting the morphologic patterns of nasal structures across species representing every extant odontocete superfamily reveals probable homologous relationships, which suggests that all toothed whales may be making their biosonar signals by a similar mechanism.

Deep Learning MR Imaging-based Attenuation Correction for PET/MR Imaging

Purpose To develop and evaluate the feasibility of deep learning approaches for magnetic resonance (MR) imaging-based attenuation correction (AC) (termed deep MRAC) in brain positron emission tomography (PET)/MR imaging. Materials and Methods A PET/MR imaging AC pipeline was built by using a deep learning approach to generate pseudo computed tomographic (CT) scans from MR images. A deep convolutional auto-encoder network was trained to identify air, bone, and soft tissue in volumetric head MR images coregistered to CT data for training. A set of 30 retrospective three-dimensional T1-weighted head images was used to train the model, which was then evaluated in 10 patients by comparing the generated pseudo CT scan to an acquired CT scan. A prospective study was carried out for utilizing simultaneous PET/MR imaging for five subjects by using the proposed approach. Analysis of covariance and paired-sample t tests were used for statistical analysis to compare PET reconstruction error with deep MRAC and two existing MR imaging-based AC approaches with CT-based AC. Results Deep MRAC provides an accurate pseudo CT scan with a mean Dice coefficient of 0.971 ± 0.005 for air, 0.936 ± 0.011 for soft tissue, and 0.803 ± 0.021 for bone. Furthermore, deep MRAC provides good PET results, with average errors of less than 1% in most brain regions. Significantly lower PET reconstruction errors were realized with deep MRAC (-0.7% ± 1.1) compared with Dixon-based soft-tissue and air segmentation (-5.8% ± 3.1) and anatomic CT-based template registration (-4.8% ± 2.2). Conclusion The authors developed an automated approach that allows generation of discrete-valued pseudo CT scans (soft tissue, bone, and air) from a single high-spatial-resolution diagnostic-quality three-dimensional MR image and evaluated it in brain PET/MR imaging. This deep learning approach for MR imaging-based AC provided reduced PET reconstruction error relative to a CT-based standard within the brain compared with current MR imaging-based AC approaches. © RSNA, 2017 Online supplemental material is available for this article.