Biomedical subjects

A J Aho

Publications and source records attributed to A J Aho.

At least 19 recordsLinked to original sources

PubMed2004

Surface porous fibre-reinforced composite bulk bone substitute.

The aim of this study was to describe and evaluate the significance of a porous surface with bioactive glass granules (S53P4) covering an artificial bulk material based on polymethylmetacrylate (PMMA) and fibre-reinforced composite (FRC) technology. Effort was focused particularly on characters of the porous surface and biomechanical properties of the material in vitro , and test in vivo the implant in reconstruction in an experimental long bone segment defect model. The defect, 10 mm in length, created in the shaft of rabbit tibia, was reconstructed by the implant and fixed by intramedullary K-wires. The implant was incorporated within 4 weeks by new bone growth from the host bone covering particularly its posterior surface and cortex/implant junctions with bridging trabecular bone. Later, at 8 weeks, new bone was found also at the cortex/implant interface and in the medullary canal of the implant. Histometric measurements revealed direct bone/implant surface contact in 34% at the interface. Bioactive glass granules in the porous surface evoked the most direct contact with bone. The implants manufactured from PMMA only served as a control group, and showed significantly lower osteoconductive properties. Biomechanical measurements in vitro of fibre-reinforced PMMA specimens revealed values for bending strength and the flexural modulus to match them to human bone. This artificial bulk bone material based on PMMA/FRC technology seems to have proposing properties to be used as a bone substitute on load-bearing conditions.

Bone Substitutes↗

PubMed2003

Granule size and composition of bioactive glasses affect osteoconduction in rabbit.

Bioactive glass granules of three different compositions, regarding particularly Si- and Al- content (S53P4, S59.7P2.5, S52P3) and of two different granule sizes (200-250 microm and 630-800 microm) were implanted for 4 and 8 weeks in the distal part of rabbit femur. The effect of glass composition and granule size on bone formation was studied. The results were evaluated using histology, computerized histomorphometry, scanning electron microscopy and energy dispersive X-ray analysis, and used for mathematical description of bone formation. The results showed that both the composition of the glass and the granule size of the granules, have influence on bone growth from the surrounding tissue. Glass S53P4, which from previous observations is known to be an effective bioactive glass and widely used in the Biomaterial Project of Turku, Finland, showed bone bonding and increasing bone growth between the granules. Glass S59.7P2.5 which due to its high Si-content should be inert, showed bone bonding. At 4 weeks the bone growth was significantly more abundant in bone defects filled with large granules (630-800 microm) than in defects filled with small granules (200-250 microm). Glass S52P3 with an alumina content of 3 wt %, showed good bone conduction, possibly even bone bonding for granules of 630-800 microm size. Granules of 200-250 microm with a high alumina content at the surface of the reaction layer, showed hardly any bone contact at all. This data, therefore, gives new information concerning bone bonding and osteoconduction of bioactive glasses with a high silica or alumina content.

Journal Article↗

PubMed2002

Bioactive glass as bone-graft substitute for posterior spinal fusion in rabbit.

Bioactive glass S53P4 and autogenous bone were studied as bone graft materials for spinal fusion in a rabbit model. Sixteen rabbits underwent surgery by a dorsal approach. A bioactive glass, a combination of bioactive glass and autogenous bone (70/30 vol%), and autogenous bone were implanted at two thoracolumbar vertebraes for 4 and 12 weeks. The volume, consolidation to vertebrae, and fusion of the graft material were evaluated with plain-film radiology, computed tomography (CT) and bone-mineral density measurements, and compared with histomorphometrical measurements. Radiological consolidation by CT of bone graft to underlying vertebrae at 12 weeks was observable in all groups. This was histologically confirmed as bone was growing from the vertebrae into the graft material. Radiologic fusion of vertebraes was, at 12 weeks, observable in all groups in 50--75% of the cases. The radiologic fusion seen at the CT scans could, however, not be confirmed by histology in any of the three groups. Significant differences for graft material and observation period with the use of bone-mineral density measurements (Hounsfield units) were also observable, with the highest measured values for the bioactive glass group and the lowest for the autogenous bone group. The results indicate that bioactive glass have potential as bone-graft material in spinal fusion. The reliability of radiologic evaluation methods in spinal surgery using bone substitutes is also questioned and discussed.

Animals↗

PubMed2000

Tissue response to bioactive glass and autogenous bone in the rabbit spine.

Bioactive glass S53P4 and autogenous bone were used as bone graft materials in an experimental rabbit model for spinal fusion. The study focused on differences in bone formation using bioactive glass and autogenous bone as bone graft materials. Bioactive glass, a mixture of bioactive glass and autogenous bone or autogenous bone was implanted for 4 and 12 weeks at the thoracolumbar level. Undecalcified sections were prepared for histological and histomorphometric evaluation. New bone formation was seen in all implanted areas, with the bone growing from the surface of the vertebrae enclosing both glass and autogenous bone in the bone fusion mass. During the observation period, the measured amount of bone remained at the same level in the autograft group, while in the glass and the glass/autograft bone groups it increased. By 12 weeks, no significant difference in bone formation between the three groups was observable. The bone formation in two selected standardized areas at 12 weeks was 21 and 24% in the glass group, 23 and 28% in the glass/autograft bone group and 27 and 26% in the autograft bone group. We consider bioactive glass as a potential bone graft material in experimental spinal fusion.

Animals↗

PubMed1998

Bone morphogenetic protein in bone neoplasms: comparison of different detection methods.

The presence of bone morphogenetic proteins (BMPs) in 13 primary bone neoplasms was investigated with conventional bioassay method and immunohistochemically using antiserum against highly purified mixture of bovine BMPs as antibody. In conventional bioassay after implantation of lyophilized bone tumor tissues into mouse muscle pouches 9/13 samples turned out positive by radiography and 10/13 histologically. By immunohistochemical staining, using the avidin-biotin-peroxidase method, signs of BMPs could be verified in all cases investigated. Microscopical scoring showed the local concentration of BMPs to be especially high in sections from giant cell tumors when compared to other bone neoplasms.

Adolescent↗

PubMed1998

Bone bank service in Finland. Experience of bacteriologic, serologic and clinical results of the Turku Bone Bank 1972-1995.

560 bones were harvested by The Turku Bone Bank between 1972-1995. It was started with massive allografts for bone tumor surgery, but today most are femoral heads for hip revision surgery. The increase in harvested bones nearly trebled from 1984-1989 to 1990-1995. Only 1 positive hepatitis C test was found. There were no hepatitis B or HIV positive donors. The incidence of discarding after screening was 24%, with positive bacterial growth (8%, usually Staphylococcus epidermidis) as the commonest reason. 2 massive grafts with negative cultures when harvesting were positive after thawing and resulted in deep infection. 369 allografts were transplanted. The infection rate of massive allografts for bone tumor surgery was 5/63 in 1973-1995, and 2/52 in 1985-1995. The infection rate for hip revision surgery was 3.4%. The clinical functional results correspond to those reported in larger international series.

Adolescent↗

PubMed1998

Immune responses and clinical outcome of massive human osteoarticular allografts.

Cell mediated immune responses as measured by lymphocyte proliferation induced by the mitogens phytohemagglutinin and concanavalin A and antigen extracts of donor derived bone were studied within 2 years after wide resection of bone tumors in 18 patients receiving fresh frozen massive osteoarticular allografts. No uniform changes were seen in mitogen induced responses in 18 patients. However, five of nine patients tested with antigen extracts of donor derived bone showed elevated immune responses, one moderate and four weak. The incorporation of the allograft (evaluated by repeated radiographs; specific isotope techniques; clinical outcome assessed by the functional rating scores of Mankin-Waber and the Musculoskeletal Tumor Society; and histologic biopsy findings on new bone formation) did not differ in these patients from those in patients without any response to donor derived tissue. During a long term followup (mean, 11 years; range, 2-20 years), degenerative joint and sclerotic density bone changes developed after 2 to 4 years without correlation to immune responses. Histologic specimens showed no signs of immunologic reaction, and no clinical rejection episodes were recorded. A slightly variable immune response to allograft bone seems to occur, but its clinical significance for outcome of the grafts remains to be determined. The low immune responses might reflect a low antigen release rate through an indirect pathway or immunologic tolerance to antigens or proteins shed from massive allografts that are nonliving scaffold implants during the creeping substitution process, corresponding to the low immune response and the slow histologic repair.

Adolescent↗

PubMed1997

Measurement of total and local bone morphogenetic protein concentration in bone tumours.

Bone morphogenetic protein (BMP) has been shown to be one of the significant factors in the prognosis of bone tumours. In normal development BMP induces new bone formation and later takes part in fracture healing, but its function in malignant tumours is not known. In this study the concentration of bone morphogenetic protein was measured in primary bone tumours by two methods. Local staining intensity was detected immunohistologically by the avidin-biotin-peroxidase method determining the highest dilution of anti-serum against bovine bone morphogenetic protein. The total amount of BMP in a tumour sample was measured by an enzyme-linked immunosorbent assay technique after digesting the tissue with collagenase to remove proteins from the connective tissue. Immunohistochemical staining showed that bone morphogenetic protein was present in the cytoplasm and in reactive bone formed by malignant cells. The local concentration was highest in the tissue of giant cell tumours compared to chondrosarcoma, osteosarcoma and benign bone tumours. The total amount in malignant bone tumours was 2.4 times higher compared to benign bone tumours.

Adolescent↗

PubMed1997

Treatment results of osteogenic sarcoma. An evaluation of 36 patients treated during 30-year period in south-western Finland.

Histological re-evaluation revealed 36 osteogenic sarcoma (OS) patients for analysis in South-Western Finland treated between 1958 and 1987. In 21 cases (58%) the tumour was located in the knee region. The mean age at diagnosis was 28 years (range: 5-62 years) and the follow-up time of the patients was at least 5 years or until death. In 29 patients without metastases at the time of diagnosis, the extent of the primary tumour was T2 in 37% and T3 in 63% of the patients. There were no differences regarding the extent of the primary tumour, delay of the diagnosis, mean age of the patients, or duration of the symptoms while comparing the three decades of the study. Before the 1970s the treatment consisted of surgery with or without radiotherapy in most cases. Since the 1970s the combination of surgical treatment (amputation or wide excision) and adjuvant chemotherapy was the most common treatment modality. Since the late 1970s limb-salvage surgery has been applied in selected cases, and it seems to be justified. None of the patients treated before 1970 survived for 5 years. The 5- and 10-year survival of all 36 patients was 44.4% and 33.6%, respectively. In non-metastatic patients both the 5- and 10-year disease-free survival was 46.7%. A certain group exhibiting a good prognosis was found; the 10-year survival of the 10 patients with OS in extremities, treated with combined chemotherapy and surgery, was 70%. The median survival time was significantly longer for the patients with an intracompartmental tumour extent of T2 (112 months) compared with an extracompartmental extent of T3 (23 months), and for the patients with the primary tumour in the knee region (112 months) compared with other locations (18 months). The long-term survival of the OS patients has improved concomitantly with the multimodality of the treatment.

Adolescent↗

PubMed1996

Subchondral bone and cartilage repair with bioactive glasses, hydroxyapatite, and hydroxyapatite-glass composite.

The repair of an osteochondral defect in rabbit femur was studied with three kinds of bioactive glasses (BG), hydroxyapatite (HA), and hydroxyapatite-glass (HAG) composite. Seventy-two osteochondral defects were created in 18 rabbits. Sixty-four cylinders were implanted and eight defects were left empty as controls. Histomorphometry, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA) were used for evaluation. Small osteochondral defects in rabbit femur found to heal themselves by regeneration. The three BGs, HA, and HAG led to direct lamellar bone repair of subchondral bone and restoration of articular surfaces mostly with hyalinelike cartilage in 12 weeks. However, the composition of the materials affects their behavior. Chondrogenesis took place earlier with the BGs than with HA. HAG degraded too much, glass 14 was too reactive and brittle, and the high alumina content in glass 11 disturbed its bone-bonding ability. Glass 7 and HA were the most balanced in the repair process. A special preparation method was used to retain soft tissues fairly unchanged and enable them to the observed together with hard tissues in SEM analysis.

Animals↗

PubMed1996

Polymethylmethacrylate composites: disturbed bone formation at the surface of bioactive glass and hydroxyapatite.

The effects of polymethylmethacrylate on bone formation were studied alone and as composites in combination with hydroxyapatite and bioactive glass in the rabbit subchondral femur. Radiographs, histology, computer assisted histomorphometry, scanning electron microscopy and energy dispersive X-ray analysis were used for evaluation. A total of 60 cones were implanted for 3, 6 and 12 weeks. The composite cones consisted of granules of bioactive glass (S56.5P4) or hydroxyapatite embedded in polymethylmethacrylate. Pure polymethylmethacrylate cones served as controls. At the interface of the cones, bone contact was observed only when bioactive glass or hydroxyapatite was present at the cone surface. Fibrous tissue was always found at the polymethylmethacrylate-tissue interface. The osteoconductive bone formation at the surface of bioactive glass and hydroxyapatite was disturbed by polymethylmethacrylate. It seemed to resist bone formation at the interface of both bioactive glass and hydroxyapatite. However, bioactive glass was better able to withstand the detrimental effect of polymethylmethacrylate than hydroxyapatite.

Animals↗

PubMed1995

Hydroxyapatite-glass composite as a bone substitute in large metaphyseal cavities in rabbits.

This study evaluated hydroxyapatite-glass (HA-G) composite as a filler material when implanted into a proximal metaphyseal tibial cavity consisting of medullary tissue and cancellous bone in rabbits. The repair process was compared with that of autogenous bone grafts and untreated controls. Scanning electron microscopy, energy dispersive x-ray studies, radiography, histology with tetracycline fluorescence and morphometric bone measurements were used for evaluation. Equal amounts of mineralised bone were produced in both HA-G granule and autograft groups at 3 weeks; thereafter, autografts mostly resorbed, whereas there was appositional lamellar bone formation on the early woven bone in the HA-group. A relatively small proportion of the cavities was repaired by new bone. The HA-G granules were biocompatible without foreign body reaction and showed good osteoconductive potential. Mesenchymal cells were able to differentiate into osteoblasts on bioactive surfaces of the composite. Although HA-G was able to form Ca-P-rich and Si-rich layers, most of the granules underwent degradation through its glass matrix, resulting in fewer bony contacts than granules with no surface degradation.

Animals↗

PubMed1995

Massive osteoarticular knee allografts: structural changes evaluated with CT.

PURPOSE: To analyze the structural changes seen at computed tomography (CT), particularly the findings that precede insufficiency (fatigue) fractures in massive osteoarticular knee allografts. MATERIALS AND METHODS: The subchondral and cancellous bone of 12 allografts were retrospectively evaluated with repeat transaxial CT (mean follow-up, 53 months). RESULTS: Early cortical graft resorption was followed by slow thickening after 6 months. Formation of resorptive cysts increased the cortical irregularity, which leveled off after 2 years. Late remodeling was evident as a subcortical sclerotic rim, "neocortex." Initially, the cancellous graft bone showed higher attenuation than the host bone; this difference subsided gradually during the first 3 years. Four insufficiency fractures were detected after the 1st postoperative year. Poor remodeling preceded these fractures. CONCLUSION: CT effectively depicted the structural changes during allograft incorporation and was superior to plain radiography for the detection of insufficiency fractures. The use of CT for follow-up of massive osteoarticular knee allografts provides additional information concerning the readiness of the graft for weight bearing.

Adolescent↗

PubMed1995

Bone formation in rabbit cancellous bone defects filled with bioactive glass granules.

We examined new bone formation after filling cancellous bone defects with bioactive glass (BG) in granular form. Cylindrical defects in the trochanter area of 18 rabbit femora were filled with BG granules (diameter 600-830 microns) and compared with similar defects filled with morcellized autogenous bone. New bone formation and surface reaction of BG particles were evaluated by light microscopy, histomorphometry, and scanning electron microscopy. The chemical profile at the bone- material interface was studied by energy dispersive x-ray analysis (EDXA). In the BG group, 41, 32, and 38 percent of the defects were filled with new bone after 3, 6, and 12 weeks, respectively. The corresponding figures for the autogenous bone group were 36, 29, and 34 percent. The thickness of the reaction layer on the glass surface increased from 82 to 163 microns during the observation periods. An intimate contact without intervening soft tissue between new bone lamellae and BG granules was a constant finding. EDXA showed a chemical continuum between the granules and the new bone. No adverse reactions related to BG were observed. BG is a promising material for filling cancellous bone defects.

Animals↗

PubMed1995

[Tissue banks].

Explore the source record for details and available documents.

Bone Transplantation↗

PubMed1994

Incorporation and clinical results of large allografts of the extremities and pelvis.

The results of implantation of 37 large deep-frozen allografts with 29 osteoarticular grafts of the extremities and pelvis following the resection of malignant or aggressive benign bone tumors were evaluated at followup (mean, 6 years; range, 2.5-20 years). The patients had excellent or good results in 62% of all cases according to the Mankin-Waber functional rating score, and a corresponding rating of 81% in the Musculoskeletal Tumor Society Score. Benign versus malignant disease rated 83% and 76%, respectively, in the Musculoskeletal Tumor Society Score, and 67% and 46%, respectively, in the Mankin-Waber score. Radiological and nuclear medicine (single-photon emission computed tomography) studies and histological biopsies indicated that the incorporation, perfusion, and replacement with new bone was only partial and of a low degree. Late degenerative cartilage and sclerotic changes occurred in 20 of 29 cases with osteoarticular grafts. The best functional results were achieved with knee osteoarticular allografts (81%-88%) compared with modest results in the proximal humerus (69%) and hemipelvis (57%) according to the Musculoskeletal Tumor Society Score rating. Chemotherapy did not influence the union or infection rate of the allografts. In the 4 cases (11%) with infection, all grafts could be salvaged, but the functional results were only 63% in the Musculoskeletal Tumor Society Score. The overall complication rate was high (57%); graft-related complications occurred in 43%, including fatigue fractures in 27%. There were no cases of nonunion at the host graft junction. Clinical rejection did not occur. These clinical results may be improved in the future by new technology that uses bone substitutes, growth factors, and bone morphogenetic proteins.

Adult↗

PubMed1993

Clinical use of bone allografts.

Modern techniques of bone allograft surgery provide a treatment modality for management of difficult skeletal defects. In oncological limb-salvage surgery, allograft reconstructions permit re-establishment of skeletal continuity and function after a wide resection of bone tumour. Bone allografts are increasingly used in salvage of difficult bone stock deficiencies following failed total joint replacements. Union between the allograft and the host bone takes place slowly and the use of autogenous bone graft at the graft-host junction is recommended for induction of repair. Internal repair (revascularization and substitution of the original graft bone with new host bone) also progresses slowly and seems to be confined only to the superficial surface and the ends of the graft. Biomechanically, a massive allograft may serve a structural function in the absence of advanced revascularization and creeping substitution processes. Infection of an allograft is a disastrous complication, whereas non-union of the graft-host junction and fracture of the graft are amenable to surgical treatment. Osteochondral allografts tend to show gradual deterioration of the articular cartilage with time, necessitating occasionally late resurfacing arthroplasty. It is evident that there is more active immune response to osteochondral grafts than was thought previously. Bone allografts induce cell-mediated and antibody-mediated cytotoxicity specific for donor antigens similar to that seen after organ transplantations. Not only the basic mechanisms of bone allograft rejection but also the clinical features of bone allograft rejection are poorly characterized. Clinically, new non-invasive imaging techniques should be applied in determining the metabolic activity of bone in order to find the optimal loading of healing allografts. Although the clinical results of massive bone allografts are still not completely predictable, the method has proved to be a technically and biologically feasible alternative for non-biological skeletal reconstructions.

Arthroplasty↗

PubMed1993

Bioactive glass versus hydroxylapatite in reconstruction of osteochondral defects in the rabbit.

We studied osseointegration of a bioactive glass (BG) and hydroxylapatite (HA) in rabbit femur epiphyseal and metaphyseal regions. 17 BG and 24 HA cones implanted in defects through arthrotomy were analyzed. The holes for implants were drilled through distal femur joint surfaces. The cartilage wound repaired generally by fibrous tissue. Histomorphometry showed that 61, 78, and 79 percent of BG surface was covered by bone at 3, 6, and 12 weeks, respectively. The corresponding figures for HA were 47, 67, and 78 percent. Chemical bonding between bone and implants of both types was confirmed by scanning electron microscopy (SEM) and energy-dispersive x-ray analysis (EDXA). Formation of a calcium phosphate-rich layer on the surface BG implant was demonstrated by EDXA. Our results indicate that the osseointegration rate of bioactive glass does not differ from that of hydroxylapatite.

Animals↗