PubMed Health⌕ Search

Biomedical subjects

B A Rahn

Publications and source records attributed to B A Rahn.

At least 73 records · Page 4Linked to original sources
PubMed1982

Silver antibacterial bone cement. Comparison with gentamicin in experimental osteomyelitis.

An animal model was used to evaluate and compare silver methacrylate with gentamicin methacrylate in experimental Staphylococcus osteomyelitis. One tibia from each of 54 rabbits was innoculated with 4 X 10(6) CFU of S. aureus and inserted with prepolymerized PMM rods containing either 1% Ag2SO4, 2.5% gentamicin, or no additives. By six weeks, the mortality rate was 61% in controls, 22% in Ag-PMM animals and 6% in gentamicin-PMM animals. Bacterial counts from the bone of dying and surviving animals were significantly lower than controls, 23.6% of controls for the Ag-PMM treated and 6.0% for the gentamicin-PMM treated groups. All surviving animals were culture positive, except for three sterile bones obtained from the gentamicin-PMM group. In light of these results and the favorable characteristics as an antimicrobial agent, further investigation of silver in bone cement (or other vehicles) for the prevention or treatment of bone infection appears warranted.

Animals↗
PubMed1981

Effects of plates on cortical bone perfusion.

Using disulphine blue, sheep tibial cortex perfusion was decreased by subperiosteal stripping but not by extraperiosteal exposure. Semitubular plates applied with either low (20 kp) force, sufficient for extraosseous vascular occlusion, or high (200 kp) force, similar to that used clinically, both produced significant ischemia beneath the plate. In contrast, the dynamic compression plate produced significantly greater ischemia only with the higher force.

Animals↗
PubMed1981

Healing patterns of metaphyseal fractures.

Metaphyseal fractures having different degrees of stability were produced in rats, rabbits, and dogs. The progress of healing various radiologic patterns, observed by correlated roentgenographic and histologic observations, show that the appearance on radiographs of one or two broad, ill-defined bands of increased density indicates a normal healing process. Cortical healing lags behind cancellous bone healing. No external callus develops. The appearance of two dense, well-defined bars bordering a radiolucent gap indicates delayed union or nonunion and usually can be attributed to instability at fracture site. The appearance of an external callus and the elaboration of a fibrocartilaginous bridging by callus portrays delayed union, secondary to gross instability and/or displacement. Similar patterns appear when there is an avascular fragment, in which case osteogenic activity is limited to one fracture line. Radiologic criteria based on histologic observations permit assessment of metaphyseal fracture healing.

Animals↗
PubMed1980

[Area of contact between osteosynthesis plate and bone in internal fixation (author's transl)].

The bone can be protected against excessive stress if the plate is properly adapted to the surface of the contact area between plate and bone, thus ensuring good and longlasting repositioning of the fracture. The article describes an in-vitro method for the quantitative evaluation of the contact area between plate and bone in osteosynthesis. With four different bones and the requisite plates, six expert surgeons were able to obtain an area of contact between plate and bone which varied between 13 and 60%, the average being 32%. The available data allow us to conclude that the peak loads of pressure occurring with small contact areas may be so great that they exceed the maximum compressive strength of the bone.

Bone Plates↗
PubMed1980

Biomechanics of fracture healing.

Internal fixation of fractures alters the physical environment of living bone. The authors have studied the reaction of living bone to force and motion, mainly in sheep. Cortical bone does not undergo pressure necrosis when compression is applied in internal fixation. Compressing the fragments increases the stability of the reduction and leads to uneventful healing without resorption. Small areas of plastic bone deformation owing to mechanical overload are nor removed by surface resorption but by internal remodelling. Interfragmentary motion produces callus and resorption of the contact surfaces. The static compression applied to cortical bone does not induce a change in the rate of internal remodelling. The static forces must exceed the dynamic load to maintain close coaptation at the contact surface.

Animals↗
PubMed1979

[A method of quantitative determination of tissue tolerance in decreased relative movement between implant and tissue].

A method of testing in vivo tissue tolerance to different implant materials is presented. It aims at reduction of variance due to mechanical irritation at the tissue-implant interface through the use of cylindrical implants with grooves. The special type of histological preparation which is necessary and problems encountered when using these techniques are described. The numerical evaluation of round cells and foreign body giant cells seems to give uniform results with low variance, which could be of interest for standard testing of material.

Animals↗
PubMed1979

[Bone perfusion after plate osteosynthesis. A study of the intact rabbit tibia with disulfin blue vital staining].

After operative fracture treatment an interference with blood supply has to be expected. The fixation of a plate to an intact rabbit tibia lead to extended areas where circulation is disturbed. These disturbances were partially reversible within one week without structural changes visible in the recovering bone. Only the zones remaining without vascular supply after one week started to recover in the 4th week, when intracanalicular remodelling and the formation of new Haversian systems became visible at the borders of the avascular regions.

Animals↗
PubMed1976

[Osseous bridging of the distraction gap in leg lengthening procedures (author's transl)].

The bony refill of the distraction-space in leg-lengthening operations is analysed by X-ray control and histological technic as well in animal experiments as clinical patients. Based on our observations a theory of the formation of bone is postulated: We figured out, that a) presumable besides the periosteal potentials of bone formation there are also other active mechanisms of bone growth to be found. b) frequently histological recognised formations of bones cannot yet be proved by X-ray, that means, that the X-ray changes follow the histological ones. c) optimal formation of callus needs most possible stability during the time of consolidation. d) most careful distraction prevents deformities.

Adolescent↗
PubMed1976

[Biomechanical apsects of implantation in bone].

Bone in the adult shows a continuous adaptation to the actual influence of applied stress by a combination of apposition and resorption. Little is known about this process around dental implants. It is only resorption which is known to be in relation with micromovements between bone and implant. Thus, the formation of connective tissue around implants is explained. The mechanical stress upon this connective tissue leads to the formation if fibres which recall the system of suspension of the teeth.

Biomechanical Phenomena↗