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Biomedical subjects

B Kummer

Publications and source records attributed to B Kummer.

At least 19 recordsLinked to original sources
PubMed2000

Immediate sealing of arterial puncture sites after cardiac catheterization and coronary interventions: initial U.S. feasibility trial using the Duett vascular closure device.

The aim of this first U.S. feasibility study was to investigate the safety and efficacy of a novel vascular sealing device, Duett, following percutaneous endovascular procedures. Immediately following a catheterization procedure, the sealing device was deployed at the femoral arterial access site in 43 patients (diagnostic 29, intervention 11, intervention + abciximab 3). Patients were followed up at 1 month with clinical assessment, ankle-brachial index measurement, and Doppler ultrasound of the treated femoral artery puncture site. Successful hemostasis was achieved with the Duett alone in 42/43 (97.7%) patients. There was one uncomplicated crossover to manual compression. The time to hemostasis was 4.0+/-1.5, 6.9+/-4.2, and 5.8+/-1.2 min for diagnostic, interventional, and abciximab patients, respectively. At 1-month follow-up, one patient (2.3%) required ultrasound-guided compression for treatment of a pseudoaneurysm. There were no other major complications. This novel vascular sealing device appears to achieve rapid and safe hemostasis successfully immediately following a wide range of percutaneous endovascular procedures.

Adult↗
PubMed1998

[What is the value of biomechanical knowledge for surgery of the hand?].

Cartilage and bone as supportive tissues are submitted to mechanical stresses and react to these in a very specific manner. Functional adaptation to the quality and magnitude of the acting forces is the result. In this article, the basic principles of functional adaptation of cartilage and bone will be presented. On the basis of these principles, promising functional concepts and clinical treatments may be established; this will be shown by some examples concerning the hand.

Adaptation, Physiological↗
PubMed1996

[Biomechanics of arthrodesis of the major joints of the extremities].

Insufficient movement after an arthrodesis must be compensated for by other joints. Arm movements with an ankylotic shoulder joint can be executed by rotation and tilting of the scapula. The trapezius muscle plays an important role in these movements. Arthrodesis of the hip joint requires an extended range of movement in the intact contralateral joint and sufficient mobility of the lumbar spine. Moreover, every ankylotic joint is stressed by bending because compensation of the torque due to the weight of the corresponding part of the body by the balancing muscles is no longer necessary. The architecture of the spongy bone is adapted to that bending stress. Characteristic examples are anatomic specimens of ankylotic hip and knee joints.

Arthrodesis↗
PubMed1995

[Basics of Pauwels' theory of the functional adaptation of bones].

Bone is a secondary support tissue. It develops on the base of a preexistent primary scaffold, built up by connective tissue or by cartilage. Bone formation depends on the magnitude of the elastic deformation, due to loading. The skeletal organ "bone" reacts to the actual stress like a feedback system: high stress stimulates new bone formation and incorporation of mineral salts; low stress leads to bone resorption and mobilization of mineral salts. The result of extreme stress is bone resorption (stress fractures, pseudocysts). The radiological density and architecture of the spongy bone reflect exactly the direction and local magnitude of stress.

Biomechanical Phenomena↗
PubMed1994

[Biomechanics of the meniscus].

The menisci of the knee joint enlarge the area of support to more than twice the surface of pure cartilage contact. As a result of the wedge-shaped cross-section, the meniscus is stressed by radially directed shear forces, but because of the bone attachment at both ends, the shear forces are transformed into circular tensile stress. The arrangement of collagen fibres reflects the pattern of tensile stress trajectories. Single chondroma are found in the peripheral zone. The range of displacement of the knee is considerably widened by the menisci. After meniscectomy, this function can be compensated for by the cruciate ligaments, but the stress on the articular cartilage will then increase.

Biomechanical Phenomena↗
PubMed1993

Is the Pauwels' theory of hip biomechanics still valid? A critical analysis, based on modern methods.

The Pauwels' theory of hip biomechanics assuming bending stresses of the proximal femur has been critisized by recent authors. Therefore, the fundamentals of the classic theory have been reviewed, analysed by means of modern methods, and completed. The conclusion is that, hypothetically, a totally bending-free skeletal scaffold could be obtained by muscular tear strings. The analysis of anatomical specimens and considerations on optimisation show, however, that the bending theory of the proximal femur gives still the best explanation for the observations. Furthermore, the classic model has to be completed by two important conditions: 1. The supporting foot must be positioned on the action line of the gravity force of the body, and 2. the abductorial forces on the hip (to balance the momentum of the body weight) is composed by the forces of the lesser glutei (70%) and the muscles tending the tractus iliotibialis (30%).

Biomechanical Phenomena↗
PubMed1990

[The function-dependent morphogenesis of the visceral cranium].

The growth pattern of the facial skull is described by the method of coordinate transformation and simulated in a computer model under the presumption of different growth gradients. The law of functional adaptation of the bone, as it has been proved for the postcranial skeleton, has been applied to the skull. The mechanical stress of the facial skull results from the masticatory function. Due to the complex architecture of the facial skeleton, the stress pattern cannot be determined with sufficient accuracy, needed for a detailed prediction of the growth processes. However, the exact knowledge of the mechanical stresses of single teeth allows the explanation of their positional changes by remodeling processes on the alveolar wall.

Biomechanical Phenomena↗
PubMed1990

Physiological regulation of circadian and pulsatile thyrotropin secretion in normal man and woman.

The circadian and pulsatile TSH secretion profiles were investigated in 5 females at the time of menstruation and 21 healthy males by sampling blood every 10 min for 24 h. Computer-assisted analysis, i.e. the Cluster and Desade programs, revealed means of 9.9 +/- 1.7 (Cluster) and 11.4 +/- 3.9 (Desade) pulses/24 h. More than 50% of the TSH pulses were detected between 2000-0400 h. Male and female subjects showed no significant difference in the basal mean and pulsatile secretion of TSH or in the TSH response to TRH (200 micrograms). Repetition of the TSH secretion analysis in 4 healthy subjects after 1, 2, and 6 months (2 subjects) revealed a significantly better cross-correlation within than between individuals (P less than 0.0001). We modulate the circadian TSH secretion pattern by acute sleep withdrawal or prolonged sleep after a night of sleep withdrawal in six healthy male volunteers. Sleep withdrawal augmented the nightly TSH secretion (mean serum TSH, 2.1 +/- 1.3 mU/L; mean TSH in sleep, 1.3 +/- 0.5 mU/L; P less than 0.05), whereas sleep after sleep withdrawal almost completely suppressed the circadian variation (mean TSH, 1.1 +/- 0.7 mU/L; P less than 0.01). This modulation is due to a significant decrease in pulse amplitude, but not to an alteration in the frequency or temporal distribution of TSH pulses.

Adult↗
PubMed1989

[Densitometry of the bony structures of the human TMJ].

Four millimeter sagittal section of 65 formalin-fixed human TMJs were prepared. The X-rays of these specimen were evaluated numerically in a densitometer. The distribution of bone material and densities in condyle and fossa led to a classification of condylar and fossa types. In 48 specimen a combination of increased density of the condyle on the facial aspect with a thin bony lamella in the roof of the fossa, which either shows high density or very little material of low density, a so-called parchment fossa, was observed. The varying degrees of density as a function of mechanical stresses are discussed. The transfer of forces in the human TMJ during mastication exposes the superio-anterior or superio-facial segments of the condyle and the posterior slope of the articular tubercle to loading forces, while at the same time the roof of the fossa remains free of load.

Bone Density↗
PubMed1988

[Biomechanical aspects of hip dislocation].

The stress distribution in the subluxated hip joint is analyzed by means of a two-dimensional computer model. Luxation becomes manifest if the action line does not intersect with the contour of the socket. Pathological stress with overloading of the bone and cartilage tissue appear if the articular resultant force is shifted towards the acetabular edge. The important parameter is the CE angle. The coxa valga per se has no pathological meaning as long as the femoral head is covered sufficiently by the acetabular roof.

Biomechanical Phenomena↗
PubMed1987

[Anatomy and biomechanics of the meniscus of the knee joint].

The menisci enlarge the weight-bearing surface to an extension twice of the pure contact surface between the femur condyles and the tibia plateau. Furthermore they widen the range of the articular resultant force. Consequently, the balancing muscular forces can be implemented more economically. The menisci are adapted to their functional stressing: circular tension is resisted by circularly arranged collagen fiber bundles. Split lines, however, show a more complex arrangement.

Biomechanical Phenomena↗
PubMed1987

[MR of the shoulder joint with surface coils at 1.5 tesla. Its anatomy and possible clinical use].

High spatial resolution magnetic resonance images of the shoulder were obtained in axial, sagittal and coronal orientations using a 1.5 T imaging system and anatomically shaped, wrap-around surface coils. Variations in scapular position induced by patient positioning change the relationship of the planes to the shoulder anatomy and make reproducibility of sagittal and coronal planes difficult. We, therefore, use--after axial orientation--image-oblique planes perpendicular and parallel to the glenoid fossa. In this manner MRI can visualise the anatomic structures of the shoulder including rotator cuff, long biceps tendon, articular capsule, articular cartilage, muscles and bones due to the high soft tissue contrast of MRI.

Humans↗
PubMed1985

[Mathematical model of the longitudinal growth of long bones].

The specific shape of the long bones is due to a more or less regular increase in length at the level of the epiphyseal plate (Pauwels 1958). This theory assumes, that the epiphyseal cartilage reacts to the local magnitude of stresses. The amount of bone formation is supposed to be proportional to the stress magnitudes. The bone grows straight in the direction of its axis, if the stresses are distributed evenly over the cross-section; but if the stresses increase toward one border of the epiphyseal plate, the bone formation will be stimulated more intensively at this side and consequently the axis of the bone will be bent to the opposite side. By this mechanism, the epiphyseal plate becomes oriented at a right angle to the direction of the stressing force. Pauwels (1958) explains the reorientation of the articular extremities in bones with fractures, consolidated in an angular position by the described reaction. The same reaction is responsible for the formation of the juvenile genu valgum. The genu varum and the so-called coxa vara congenita on the other hand are due to overloading of the epiphyseal cartilage. The described theory has been expressed by a mathematical function and the biological response of the bone has been simulated by means of a computer model. This model explains in a first approximation normal reactions of the growing bone even well as some pathological growth processes.

Bone Development↗