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Biomedical subjects

T Albrektsson

Publications and source records attributed to T Albrektsson.

At least 127 records · Page 7Linked to original sources
PubMed1985

Interface analysis of titanium and zirconium bone implants.

A thin layer of titanium or zirconium was evaporated onto the surface of a plastic implant which was then inserted in the rabbit tibial metaphysis for six months. The implants and surrounding bone were cut out en bloc and sectioned for phase contrast microscopy, scanning- and transmission-electron microscopy. The intact bone-to-metal interface in the case of titanium revealed a fibrous tissue-free boundary zone with a 200-400 A thick proteoglycan coat immediately adjacent to the titanium oxide. Thereafter collagen filaments were seen and, at approximately 1000 A from the interface, collagen bundles. The tissues surrounding the zirconium-coated implant consisted of a 300-500 A thick proteoglycan layer, followed by a zone with collagen filaments and collagen bundles, not closer to the zirconium oxide than a few thousand A.

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PubMed1985

Dose-response for bone regeneration after single doses of 60Co irradiation.

The Bone Growth Chamber (BGC) methodology was used to establish a dose-response relationship for regeneration of mature bone tissue after irradiation of 5, 8, 11, 15 and 25 Gy single dose 60Co. The BGC, which is a titanium implant, was inserted in the proximal tibial metaphyses, bilaterally, of a rabbit immediately following local irradiation to one tibia. Each animal thus served as its own control. During a healing period of 4 weeks, the two canals penetrating the implant became filled with more or less newly formed bone. At the end of the healing period, the implants were removed and taken apart and the newly formed bone was collected and its volume measured by microradiography and microdensitometry. It was found that in the dose range of 5 to 8 Gy bone regeneration was reduced by about 20% as compared to non-irradiated controls. Between 8 and 11 Gy, there was a critical range in that a small increase in dose resulted in a greatly reduced bone formation. At 11 Gy and above, the depression in bone formation, as compared to non-irradiated controls, was about 65 to 75%.

Animals↗
PubMed1985

Effects of direct currents on bone growth into delrin implants.

The delrin Bone Growth Chamber (BGC) which is a dividable implant, was inserted in its assembled form in the tibial metaphysis of the rabbit. The BGC allows a numerical estimation of the bone growth into the implant, based on microradiography and microdensitometry that permits evaluation of direct current (DC) effects on bone regeneration. A test chamber was inserted in one tibia and was stimulated with either 5, 20 or 50 microA for three weeks, while on the contralateral side of the same animal, a control implant was inserted under identical conditions as the test, but was not stimulated. The results showed a significant increase of bone growth with 20 and 50 microA and a tendency towards more bone formation with 5 microA.

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PubMed1985

Alterations in bone regenerative capacity after low level gamma irradiation. A quantitative study.

In the present study the influence of single 2.5 and 5 Gy doses of irradiation on the regenerative capacity of mature bone tissue has been investigated. To the knowledge of the present authors, no quantitative analysis of bone repair after low doses of irradiation has been presented previously. The experimental model used was the Bone Growth Chamber (BGC), which is a porous implant made of titanium. Each one of twenty animals was irradiated with 2.5 or 5 Gy to one tibial metaphysis. Directly after irradiation each animal had BGC:s inserted bilaterally into the tibial metaphyses. Thus, each animal served as its own control. Four weeks after irradiation the BGC:s were removed and the newly formed bone was collected from the implant pores and was analyzed by microradiography and quantified by microdensitometry and histology. It was found that 2.5 Gy irradiation led to no statistically significant alteration in bone formation as compared to non-irradiated controls. At the 5 Gy dose level, however, there was a significant reduction of bone formation as compared to non-irradiated controls.

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PubMed1985

Vascular reactions during electrical stimulation. Vital microscopy of the hamster cheek pouch and the rabbit tibia.

Vital microscopy during electrical stimulation was performed in the hamster cheek pouch and the rabbit tibia. Stimulation with DC of 5,20 or 50 microA or AC of 20 microA was demonstrated to cause macromolecular capillary leakage as evidenced by FITC-dextran fluorescence and histological demonstration of extravasated white blood cells. It was further demonstrated that the vascular leakage was blocked by administration of indomethacin. Pulsed electromagnetical fields did not visibly affect the vascular permeability within 3 h. As the same DC electrical stimulator has been demonstrated to increase the osteogenic capacity in similar titanium implants in the rabbit tibia, it is suggested that the observation of macromolecular leakage may predict a positive osteogenic response.

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PubMed1984

Osseous penetration rate into implants pretreated with bone cement.

The titanium bone growth chamber consists of two titanium disks held together by two screws. At the level of the intersection between the disks, a 1 mm wide canal penetrates the implant. After implantation, in e.g. the rabbit, tibial metaphysis bone and vessels will grow through this canal, the contents of which are collected four weeks after surgery. Microradiography and a computer-based analysis give a numerical representation of the amount of newly formed bone in the canal. When the bone ingrowth into two identical titanium implants, one inserted in the left and the other in the right tibia, was compared, only small and insignificant differences were found in the same animal. However, when one animal was compared to another, greater differences in the bone-forming capacity were found, in spite of the fact that the rabbits were controlled with respect to race, age and sex. The osseous penetration rate into titanium canals was compared to the bone ingrowth in equally sized pipes of polymerized acrylic cement which had been inserted in the titanium chamber. In these cases there was significantly less bone formed in the cement pipes compared to the titanium controls. Poor biocompatibility of the cement compared to titanium is suggested to be one factor responsible for the reduced bone formation in the cement environment. This may be one reason for the fibrous tissue capsule generally seen around cemented implants.

Animals↗
PubMed1984

Direct current influence on bone formation in titanium implants.

A dividable, titanium implant was inserted bilaterally in assembled form in the tibial metaphyses of adult rabbits. A titanium cathode was placed 5 mm proximal and a platinum-iridium anode 5 mm distally. The chamber on one side served as a non-stimulated control: on the other side the electrodes were connected to a constant current generator. Ten animals were treated with 5 microA, ten with 20 microA and ten with 50 microA. After three weeks the implants were removed, taken apart and the bone which had grown into two central canals of the chamber was collected for macroradiographic and computer-based numerical analysis. DC-stimulation with 50 microA did not result in any measurable increase of bone formation in the test implants compared to the controls. After stimulation with 5 or 20 microA, on the other hand, there was a statistically significant increase of osteogenesis, in spite of the fact that the electrodes were situated at some distance from the implant.

Animals↗
PubMed1984

An experimental and clinical study of osseointegrated implants penetrating the nasal cavity and maxillary sinus.

Implants were inserted in the upper jaw of three dogs in such a way that they penetrated the bone wall of the nasal cavity. The dogs were killed one year later, and the hard and soft tissues around the penetrating implants were analyzed. Radiographic and histologic examinations did not show any signs of adverse tissue reaction. The implants were all integrated in bone without fibrous tissue formation in the interface. A total of 139 implants, which pierced the bone of the sinus or nasal cavity, were inserted in the upper jaws of 101 patients. Forty-four sinus- and 47 nasal-penetrating implants were observed for five to ten years. The success rates were 70% and 72%, respectively. For 25 sinus- and 23 nasal-penetrating implants that were observed for two to five years, the success rates were 88% and 96%, respectively. The implant losses in nearly all clinical cases occurred during the first two years of function.

Animals↗
PubMed1984

The effect of heat on bone regeneration: an experimental study in the rabbit using the bone growth chamber.

A dividable titanium implant that, after insertion in the tibial metaphysis of an experimental animal, permits a numerical estimation of ingrowing bone was used to evaluate the effects of a defined temperature rise on bone regeneration. Heating the test implants to 47 degrees C or 50 degrees C for 1 minute caused significantly reduced bone formation in the implants, while no significant effects were observed after heating to 44 degrees C for 1 minute. The results reflect the importance of controlling the heat produced during surgery to avoid impaired bone regeneration.

Animals↗
PubMed1984

Assessment of bone viability after heat trauma. A histological, histochemical and vital microscopic study in the rabbit.

In the present investigation a comparison was made between conventional histology, histochemistry and vital microscopy for assessment of heat-induced bone tissue injury. The extent of the bone damage around a burr hole or after heating fibular bone samples in saline solutions of various temperatures was evaluated by means of histology and histochemistry, using the absence of filled osteocyte lacunae or lack of oxidative enzyme activities as indication of bone death, respectively. In both cases a wider necrotic border zone was detected with histochemistry than with histology. The vital microscopic method is based on a titanium chamber which, after insertion in the rabbit tibia, allows observation and registration of the same bone compartment for a follow-up period of more than one year. The dynamic tissue events taking place after heating to 50 degrees C for one minute were investigated and compared with histological and histochemical data of the bone. The vital microscopic method showed a consistent and widespread bone tissue injury after heating to 50 degrees C for one minute while, on the other hand, the indirect methods exhibited only inconsistent signs of tissue injury. It is concluded that histochemistry using the presence or otherwise of diaphorase enzyme activities is a more reliable method than is histology for the estimation of bone viability after heat trauma. Vital microscopy is more sensitive than indirect, morphologic and metabolic techniques for detection of heat-induced bone tissue injury.

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PubMed1984

Heat caused by drilling cortical bone. Temperature measured in vivo in patients and animals.

In vivo temperature measurements were performed at drilling in the femoral cortex of the rabbit, dog and man. In the clinical study the bone temperature was measured at fixation of a Richards plate to stabilize a pertrochanteric fracture. With a drill speed of around 20 000 rpm and saline cooling, temperatures of 40 degrees C in rabbits, 56 degrees C in dogs and 89 degrees C in patients were recorded at a distance of 0.5 mm from the periphery of the drill hole. The difference in temperature between the animal and clinical studies was mainly attributed to the difference in cortical thickness between the species. When drilling straight through the canine femur from the lateral to the medial side, a 9 degrees C higher temperature was measured in the remote, medial cortex compared to that recorded in the lateral cortex. This difference arose because it is difficult for the cooling agent to reach the medial cortex. The results of the present study indicate that temperatures measured in animal experiments are not applicable to the clinical situation where very high temperatures may arise on drilling in cortical bone, even if saline cooling is used.

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PubMed1984

Bone injury caused by curing bone cement. A vital microscopic study in the rabbit tibia.

The tissue trauma caused by leakage of monomer from curing bone cement was studied in rabbit bone. With a chamber method it was possible to study by intravital microscopy the tissue response in the same animal from the time of cement application to as long as 350 days afterward. The immediate monomer effects were mainly vascular: blood flow disturbances, blood flow standstill, and intravascular hemolysis. The most striking finding was that the extent of vascular disturbance was related to the type of tissue afflicted: In fatty marrow the effects were widespread, and in bone or fibrous tissue they were very limited. This is interpreted to reflect the affinity of the monomer to lipid-rich tissues. Follow-up observations showed marked resorption of marrow fat cells during the first weeks after injury, whereas very little bone was resorbed.

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