Biomedical subjects

T Albrektsson

Publications and source records attributed to T Albrektsson.

At least 163 records · Page 9Linked to original sources

PubMed1980

The healing of autologous bone grafts after varying degrees of surgical trauma. A microscopic and histochemical study in the rabbit.

Tibial grafts in rabbits were studied using a microscopic technique in vivo that made it possible to photograph the "graft to be" at the donor site and then subsequently to observe the same graft repeatedly at the host site. With this method the effects on the graft tissues of varying degrees of surgical trauma have been tested. The period of follow-up ranged between 14 and 300 days. The grafts removed with minimal trauma showed a more rapid rapid of revascularisation. In this group the first vessels appeared on average seven days after grafting, whereas they took 15 days in the grafts which were more severely traumatised. Bone remodelling started when the vascular density resembled the more pattern and this occurred earlier and much more rapidly in the minimally injured grafts. It correlated with the presence of surviving cells, as shown by histochemical tests, and a causal relationship is suggested. It is concluded that control of trauma is important not only in the preparation of the host bed but also in procurement of the graft. Suggestions are given on techniques to minimise the surgical trauma.

Animals↗

PubMed1980

Irradiation injury of bone tissue. A vital microscopic method.

A vital microscopic method using the titanium chamber for observation of bone irradiation injury in situ is described. The subsequent development of bone tissue resorption and replacement with a pathologic immature bone could be observed and recorded.

Animals↗

PubMed1980

Repair of bone grafts. A vital microscopic and histological investigation in the rabbit.

Using a vital microscopic method--the titanium chamber--it has been possible for the first time to dynamically follow the healing patterns in ortotopical cancellous and cortical bone grafts. Cancellous grafts healed by an initial strong osteogenetic phase without previous resorption of pre-existing bone trabeculae. Cortical grafts occasionally also healed primarily with osteogenesis, however rapidly followd by a dominant resorptive phase. A second and much stronger osteogenetic phase followed 60 days or more after grafting. Lamellated bone was as a rule preceded by woven bone of which two different types are described. Woven bone observed before grafting became lamellated afterwards which might be taken as an indication of survival of grafted woven bone. Numerous Howships lacunae, giving the bone a wavy appearance, were seen at resorption of bone trabeculae. In dense bone creeping substitution was observed. The cutter heads moved with an estimated rate of 30--40 microns a day. The resorption canals were later replaced by new bone formation. Vascular penetration rate in a cancellous graft was calculated to maximum 0.2--0.4 mm/day and in a cortical graft in pre-existing vascular canals to maximum 0.15--0.30 mm/day. A sufficient amount of vessels--about the same vascular density as before grafting--was necessary for bone remodelling to occur.

Animals↗

PubMed1980

In vivo studies of bone grafts. The possibility of vascular anastomoses in healing bone.

A titanium chamber enabling vital microscopic studies of bone tissue in situ was installed in the tibiae of 10 rabbits. Using a gentle surgical technique the chamber and surrounding bone were cut in bloc, twisted 360 degrees and reinserted into the same donor bed. Vital microscopy of these orthotopical bone grafts revealed that the circulation was mainly regained via ingrowth of newly developed vessels of host origin, starting at 5--8 days after grafting. Bone remodelling was observed at 3 weeks post grafting in these cases. In two grafts, however, an additional mode of blood flow recovery was seen. Here vessels of more than 30 microns width, registered before grafting, apparently were functioning also afterwards, indicating end-to-end anastomoses between host and pre-existing graft vessels. In these two grafts bone remodelling started as early as 1 week after transplantation.

Angiography↗

PubMed1978

The preformed autologous bone graft. An experimental study in the rabbit.

The preformation of bone grafts involves a two-step procedure. Primarily a mould is inserted in the donor bone. After a healing period of about 6 weeks (rabbits) the mould is removed. The performed bone graft (PBG) consists of the former cortical bone that has remodelled according to the shape of the mould. PBGs are today used clinically in selected cases of mandibular reconstruction. The present paper is the first in an animal experiment series investigating the PBG. It is shown that the PBG vascular supply is rearranged towards a more marrow-dominated circulation. Six weeks after the mould installation the bone showed evidence of accretion in the form of new-developed bone protrusions along the inner mould walls. A histochemical investigation revealed that the PBG surface cells survived the surgical trauma in a higher percentage than was the case when corresponding control grafts were examined.

Angiography↗

PubMed1978

Microcirculation in grafted bone. A chamber technique for vital microscopy of rabbit bone transplants.

A method enabling in vivo observations of the microcirculation in orthotopically transplated bone in the rabbit is presented. The technique permits repeated study of a well-defined bone tissue compartment both before and after grafting to an autogenous or allogenous recipient site, respectively. It yields information about the reorganization of the microvascular system and the resorptive and formative processes of bone remodelling during incorporation of grafted bone. In the autologous experimental series, new capillaries were seen in the bone grafts 4 to 5 days after transplantation. No re-utilization of pre-existing graft vessels was observed.

Animals↗

PubMedDate not supplied

Oxidized implants and their influence on the bone response.

Surface oxide properties are regarded to be of great importance in establishing successful osseointegration of titanium implants. Despite a large number of theoretical questions on the precise role of oxide properties of titanium implants, current knowledge obtained from in vivo studies is lacking. The present study is designed to address two aspects. The first is to verify whether oxide properties of titanium implants indeed influence the in vivo bone tissue responses. The second, is to investigate what oxide properties underline such bone tissue responses. For these purposes, screw-shaped/turned implants have been prepared by electrochemical oxidation methods, resulting in a wide range of oxide properties in terms of: (i) oxide thickness ranging from 200 to 1000 nm, (ii) the surface morphology of barrier and porous oxide film structures, (iii) micro pore configuration - pore sizes<8 microm by length, about 1.27 microm2 to 2.1 microm2 by area and porosity of about 12.7-24.4%, (iv) the crystal structures of amorphous, anatase and mixtures of anatase and rutile type, (v) the chemical compositions of TiO2 and finally, (vi) surface roughness of 0.96-1.03 microm (Sa). These implant oxide properties were divided into test implant samples of Group II, III, IV and V. Control samples (Group I) were turned commercially pure titanium implants. Quantitative bone tissue responses were evaluated biomechanically by resonance frequency analysis (RFA) and removal torque (RT) test. Quantitative histomorphometric analyses and qualitative enzyme histochemical detection of alkaline (ALP) and acidic phosphatase (ACP) activities were investigated on cut and ground sections after six weeks of implant insertion in rabbit tibia. In essence, from the biomechanical and quantitative histomorphometric measurements we concluded that oxide properties of titanium implants, i.e. the oxide thickness, the microporous structure, and the crystallinity significantly influence the bone tissue response. At this stage, however, it is not clear whether oxide properties influence the bone tissue response separately or synergistically.

Journal Article↗

PubMedDate not supplied

A removal torque and histomorphometric study of commercially pure niobium and titanium implants in rabbit bone.

Screw-shaped commercially pure (c.p.) niobium and c.p. titanium implants were inserted in rabbit bone. After a healing period of 3 months, a significantly higher removal torque was demonstrated to unscrew the niobium implants (average 32.9 Ncm) compared to the c.p. titanium implants (average 25.3 Ncm). In the histomorphometric part of the study, there were no significant differences in bone-to-metal contact between the 2 implant materials. An average of 41.1% bony contact was demonstrated for the niobium screws compared to an average of 37.2% for the c.p. titanium ones. Our removal torque findings could be related to the differences that we observed between the 2 implant surfaces as indicated by SEM. Since niobium implants showed a more irregular surface topography and niobium is a softer metal than c.p. titanium, this seems the most probable reason for the differences observed in removal torque between the 2 metals. Hypothetically, a more "positive biocompatibility" of the c.p. niobium in comparison to the c.p. titanium remains as another possible reason for the observed differences. However, against such a difference in biocompatibility between c.p. niobium and c.p. titanium, there is the very similar amount of bony contact registered in the histomorphometric analysis.

Animals↗

PubMedDate not supplied

Integration of titanium implants in irradiated bone. Histologic and clinical study.

Nine patients who had undergone combined surgical and radiologic treatment for malignant tumors had skin-penetrating titanium implants inserted in the bone tissue in the treated region at various time intervals after irradiation. The absorbed dose to the implant region varied between 25 and 86 Gy normalized to five fractions of 2.0 Gy/wk, according to the cumulative radiation effect formula. The time interval between irradiation and fixture insertion varied from 9 months to 37 years. Of the 35 fixtures installed, only five were lost because of lack of osseointegration. The follow-up time from implant insertion ranged from 15 to 44 months.

Ear Neoplasms↗

PubMedDate not supplied

A clinical pilot study on preformed autologous ossicles. II.

A research project concerning performed autologous ossicles has been going on for more than ten years. Animal experimental studies were followed by a clinical pilot study which showed that bone could be produced in a titanium mould placed in the proximal tibia metaphysis. In the present investigation, in which another five patients were operated on, the experimental design was changed compared to the first pilot study and bone production was improved. In addition to the tibial moulds ten titanium cylinders were placed around a bony bridge prepared in the linea temporalis of the ear to be reconstructed. Nine out of ten of these cylinders contained bone suitable for ossiculoplasty. Histology showed higher osteocyte density and a higher proportion of vital looking osteocytes in the performed grafts compared with a peroperatively sculptured graft of cortical bone. On histochemical investigation the performed graft cells seemed viable at the time of transplantation. The technique for obtaining a preformed autologous ossicle through the titanium cylinders in the temporal bone was easy to perform and the patients did not experience any discomfort. The risk of infection in this area was judged to be small.

Adult↗

PubMedDate not supplied

A clinical pilot study on preformed autologous ossicles. I.

The study is part of a project aimed at obtaining an autologous, preformed transplant for reconstruction of a defect ossicular chain. In animal experiments we found that bone could be produced in a titanium mould placed in the tibia of the rabbit and dog. To find out whether this observation was applicable in man, 5 patients with ossicular defects were selected. A titanium mould containing two chambers was placed in the proximal tibial metaphysis for 6 months. When the moulds were extracted bone was found in 7 of the 10 chambers. In 2 of these the bone was stable and suitable for ossiculoplasty. On histological examination the same picture as in the animal experiments was found, an outer layer of cortical bone surrounding a system of spongy bone with marrow and haematopoietic cells. Microradiological examination verified the presence of mineralized bone tissue.

Adult↗

PubMedDate not supplied

Five-year experience with skin-penetrating bone-anchored implants in the temporal bone.

A method for stable integration of titanium-implants in bone tissue has been developed at the University of Gothenburg, Sweden. Screw shaped implants have been inserted in the temporal bone using a delicate surgical technique. After healing-in of the implants it is, in a later séance, possible to penetrate the skin to establish a reaction-free percutaneous passage. An up to 5-year clinical follow-up has shown the possibilities of this new method in the treatment of patients with e.g. certain hearing disorders or facial defects after tumour surgery.

Follow-Up Studies↗

PubMedDate not supplied

Survival of the cortical bone columella in ear surgery.

Twenty-six partial and twenty-four ossicular replacement grafts were removed from patients because of hearing problems, cholesteatoma or re-perforation. The ossicles had been inserted in the middle ear between 7 and 121 months. The removed grafts were analysed with histology, enzyme histochemistry and, in 5 cases, tetracycline labelling. The results demonstrated that the majority (78%) of the grafts consisted at the time of removal of a mixture of living and dead bone. In 13% of the cases there were no indications of bone survival, while 9% of the removed grafts were found to consist of mainly vital bone. It is concluded that the fate of ossicular replacement grafts resembles that previously described for cortical bone grafts used in orthopaedic surgery.

Bone Transplantation↗

PubMedDate not supplied

Development of cochlear-wall implants for electrical stimulation of the auditory nerve.

The aim of these experiments was to investigate the use of titanium implants for anchorage of stimulating electrodes or other clinical or experimental devices in the bony wall of the cochlea. Twenty-six cylindrical titanium fixtures, 0.6 mm in diameter, were inserted into holes drilled in the otic capsule in 8 ears in 5 nonhuman primates and then examined for stability after periods of 2 months to 2 years. Following sacrifice, the bone-metal interfaces were examined microscopically. Fourteen of the implants were firmly fixed in the bone, 6 were loosely fixed and 6 came out. Poor fixation was associated with infection in the middle ear. In uninfected ears, 90% of the implants were stable. The implants were not osseointegrated in the classic sense, but in stable implants, direct bone contact covering 5 to 60% of the titanium oxide surface of the implant shaft was observed.

Animals↗

PubMedDate not supplied

Dynamics of irradiation injury to bone tissue. A vital microscopic investigation.

The dynamic changes after a single dose of 15, 25 or 40 Gy 60Co were followed in a titanium vital microscopic bone chamber which permitted observation of the same tissue compartment for over 2 years. The chamber consists of a hollow screw containing 2 glass rods 100 micron apart. The device was inserted into the cortex of the proximal tibial metaphysis of a rabbit. During a healing period of 4 to 6 weeks the space between the glass rods became filled with bone and vessels and in some cases fat. Once a steady state in bone remodelling had been achieved, the animals were irradiated. Vital microscopy was then performed at regular intervals. Mature bone was relatively radioresistant since remodelling continued at a normal rate. In contrast, immature woven bone remained unlamellarized and in some animals tended to increase in amount. The vascular architecture was largely unaltered, even after 40 Gy. Thrombosis or hemorrhage clearly attributable to irradiation was not noted. Initially, the number of fat cells was reduced but repopulation was later seen in several cases.

Adipose Tissue↗

PubMedDate not supplied

Provoked repetitive healing of mature bone tissue following irradiation. A quantitative investigation.

A titanium implant, the bone harvest chamber (BHC), was used to investigate the regenerative capacity of mature bone after irradiation. One BHC was inserted in each proximal tibial metaphysis of a rabbit. One of these implant sites was irradiated (60Co single dose) to either 15 or 25 Gy while the other served as control. Newly formed bone grew through a canal that penetrated the implant. This newly formed bone was harvested from the implant every three weeks following irradiation and then quantified by microradiography and computer-assisted densitometry. In this way a ratio between bone formed on the irradiated side in comparison with the control could be established. An immediate depression in bone formation compared with the non-irradiated controls, was seen at both dose levels. A recovery in bone regenerative capacity was seen at 15 weeks after 15 Gy while the decrease in bone formation remained constant after 25 Gy during the 30 week follow-up period.

Animals↗

PubMedDate not supplied

Bone healing following irradiation during tourniquet ischaemia.

The bone harvest chamber (BHC) methodology, a titanium implant for quantitative evaluations of bone healing, was used in order to investigate the radioprotective function of anoxia, in healing bone tissue. After incorporation of one BHC in each proximal tibial metaphysis of a rabbit it was possible to collect newly formed bone specimens in 3-week-periods without animal sacrifice. The amount of bone was determined by microradiography and densitometry. Ten animals divided into 2 groups were used. One group receiving a single dose of 25 Gy during tourniquet ischaemia was compared with another receiving the same dose during normal blood perfusion. A significantly improved bone healing response was seen in the ischaemic group, with a tendency to further improvement with increasing time after irradiation.

Animals↗

PubMedDate not supplied

Tissue regeneration adjacent to titanium implants placed with simultaneous transposition of the inferior dental nerve: a study in dogs.

Transposition of the inferior alveolar nerve was performed in an experimental dog model. Four adult greyhounds were used in the study. Surgical transposition of the nerve was made bilaterally, and 3 implants were placed on each side while the nerve was lateralized. On one side, the nerve was repositioned in contact with the implants, while on the contralateral side a resorbable membrane was positioned between the implant surface and the neurovascular bundle. Histologic section after 4 months of healing showed an intimate contact between implants and nerve tissue in all cases without an interpositional membrane, in contrast to cases with membranes. Histomorphometric measurements of the distance between the implants and the nerve tissue showed that the membrane side had a considerably larger distance between the implant and the nerve, although not with concomitant bone formation.

Absorption↗