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Biomedical subjects

G Bergmann

Publications and source records attributed to G Bergmann.

144 records · Page 8Linked to original sources
PubMed1977

[Incorporation of radioactive calcium and technetium pyrophosphate in to bones].

A method is given for simultaneous in vivo measurement of mineral and collagen metabolism of the bone. Accretion rates of 47-calcium as a chlorid into the bone are representative for bone mineralisation and of 99m-technetium labelled pyrophosphate for collagen metabolism. Compartmental models used for analysis are presented. Bone accretion rates are given in mg, or mMol respectively per unit time for the skeleton, by computation of the specific activity of 47-calcium and 99m-Technetium pyrophosphate and rational bone accretion as registered by total body profile scanning technique. The results obtained in five normal volunteers are presented.

Apatites↗
PubMed1977

[Critical observations and the loads on femoral head replacement and the femoral bone calculated for a support in 3 points (author's transl)].

In their attempts at calculation of forces acting on a femoral head implant and the forces transmitted to the bone, some authors have assumed support of the implant in a few distinct points. It can be shown, however, that forces thus calculated very much depend on the direction and point of action of the supporting forces assumed arbitrarrily. The suggestion to implant a prosthesis in a "valgus" position cannot be justified by results obtained by the method in question. The change in the resultant force at the hip joint due to positioning in "varus" or "valgus" has not been taken into account by previous authors. In the valgus position of the femoral head prosthesis the resultant hip force is up to 33% greater than that in a "varus" position.

Biomechanical Phenomena↗
PubMed1977

[Walking with canes and forearm-crutches. I. Reduction of loads at the hip and proximal end of the femur by one sided use of cane/crutch (author's transl)].

The effect of one cane or forearm-crutch on some mechanical parameters at the contralateral hip were investigated. 5 healthy individuals were photographed on a walkway while using an instrumented cane/crutch. Geometric data from an original mathematical model were taken from these fotographs and an X-ray film of the pelvis and femur. The resultant force and pressure at the hip joint, shear force in the femoral neck and, in one case, the bending moment in the trochanteric region were computed and expressed as a function of the load applied to the walking-aid. All values decreased with an increase of this load. The reduction of force and pressure at the hip joint achieved by application of a load equal to 15% of bodyweight are superior to those resulting from common operative procedures done for the samp purpose. Differences between the effects of one sided cane and forearm-crutch are negligible.

Biomechanical Phenomena↗
PubMedDate not supplied

[In-vitro measurement of loading using an instrumented vertebral internal fixator].

Only little is known about the loads acting on internal spinal fixation devices. The forces and moments for different external loads were now measured using instrumented implants. Measurements were performed on intact cadaver spines and after a corpectomy. Additionally the influence of the mounting accuracy on the distribution of the loads in the fixators was investigated. It could be shown that the implants are not loaded symmetrically. After a corpectomy the loads on the implants are significantly higher than for an intact spine.

Aged↗
PubMedDate not supplied

[In vivo measurement of hip joint stress. 1. Physical therapy].

The forces acting during physiotherapy in both hip joints of one patient have been measured in vivo using a telemeterized joint prosthesis. During supported exercises the loads are up to 50% of the body weight (BW). Active movement of the leg against resistance in a lying position let the forces rise up to 250% BW. During symmetric two-legged-stance the load is typically 70% BW, while during walking peak values of about 300% BW were measured. By use of one crutch a 25% reduction of the joint force can be achieved.

Biomechanical Phenomena↗
PubMedDate not supplied

[Stresses on the femur following hip joint replacement].

The stresses in femur after joint replacement have been calculated with the finite element method and the results were checked by using strain gauges glued on the surface of the femur and on the prosthetic stem. The influence of stem length and prosthetic collar on the distribution of the stresses have been investigated. The stem length has only a minor effect on the stress distribution if the stem has a texture which allows transfer of tension and shear at the interface endoprosthesis--bone cement. Merely at the tip of the stem changes of the stresses are obvious. The stresses in the bone near the resection plane are distinctly reduced if the prosthesis has a collar. These results have very limited relevance for implants with a smooth stem which does not allow the transfer of tension and shear at the interface endoprosthesis--bone cement.

Bone Cements↗
PubMedDate not supplied

Analysis of simulated single ligament transection on the mechanical behaviour of a lumbar functional spinal unit.

The influence of the different lumbar spinal ligaments on intersegmental rotation is not fully understood. In order to explore this effect, a finite element model of the functional spinal unit L3/L4 was loaded with pure moments in the three main anatomic planes. The two extremes--minimum and maximum--ligament stiffness values reported in the literature were applied. After virtual transection of each of the spinal ligaments in turn, the intersegmental rotation and forces in the remaining ligaments were calculated. On flexion, the highest force was found for the posterior longitudinal ligament; on extension and lateral bending for the anterior longitudinal ligament; and on axial rotation for the facet capsular ligament. The strongest influence on intersegmental rotation is exerted by the interspinous ligament on flexion, by the anterior longitudinal ligament on extension and lateral bending, and by the facet capsular ligaments on axial rotation. Ligament stiffness has a strong influence on intersegmental rotation and forces in the ligaments, so that finite element models of spinal segments must be validated by experimental data. This study should help to elucidate the role of the various ligaments.

Biomechanical Phenomena↗