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During the last two decades autologous platelet and leukocyte rich products (PRP; PRF), opened new perspectives in regenerative medicine. In particular regenerative dentistry played a pioneer role in the application of these products in bone regenerative cases. Many aspects of cytokines, such as, growth factor release, blood cell content and its characterization were reported, but some practical questions are still unanswered in the preparation of PRF membranes and sticky bones. A new folding technique was introduced that created a good quality, pliable, and strong F-PRF membrane with a dense fibrin network and more homogenous blood cell distribution. F-PRF produced a very promising sticky bone combined with human freeze-dried cortical bone matrix gelatin (BMG). There hasn't been much focus on the quality and character of the applied bone and the optimal membrane/bone particle ratio has not been reported. A 0.125 g BMG/ml plasma (1 g/8 ml) seems like the ideal combination with maximal BMG adhesion capacity of the membrane. Particle distribution of BMG showed that 3/4 of the particles ranged between 300-1000 µ, the remnant 1/4 was smaller than 300 µ. The whole F-PRF membrane and its parts were compared with conventional A-PRF membrane concerning their resistance against proteolytic digestion. The F-PRF was superior to A-PRF, which dissolved within 4-5 days, while F-PRF was destroyed only after 11 days, so this provides a better chance for local bone morphogenesis. The F-PRF pieces had similar resistance to the whole intact one, so they can be ideal for surgical procedures without risk of fast disintegration., (© 2021. The Author(s).)

Purpose: Donor site pain affects 32-43 % of patients after anterior cruciate ligament surgery when the autograft is freshly harvested bone-patellar tendon-bone tissue. Our aim was to compare functional and morphological differences between donor sites with and without serum albumin-coated bone allograft filling., Methods: After harvesting and implanting the graft, the tibia site was filled with either fresh autologous cancellous bone enhanced with albumin-coated allograft or autologous bone alone. The patella site was filled either with albumin-coated allograft or with blood clot. Knee function was evaluated by the VISA, Lysholm and IKDC scores and a visual analog scale of pain during standing, kneeling and crouching after six weeks and six months. Computed tomography was performed at six months for morphological evaluation., Results: At six weeks, both groups were still recovering from surgery and the overall knee function was still impaired but the functional scores were significantly higher in the Bone-Albumin group. The pain with crouching and kneeling was also lower as compared to controls. At six months, the knee function scores were close to normal, with a slight decrease in the controls. Pain at kneeling was still prominent in the controls, but significantly lower in the Bone-Albumin group. Computed tomography showed significantly smaller bone defects and higher bone density in the Bone-Albumin group., Conclusions: Results from the present study indicate that donor site pain, a disturbing long-term side effect of bone-patellar tendon-bone surgery, is significantly reduced if bone buildup in the patella and the tibia is augmented by serum albumin-coated bone allografts.

The authors report the history of a 74-year-old patient who underwent surgical treatment for segmental knee-joint periprosthetic bone loss using structural proximal tibial allografts coated with serum albumin. Successful treatment of late complications which occurred in the postoperative period is also described. The authors emphasize that bone replacement with allografts is a physiological process that enables the stable positioning of the implant and the reconstruction of the soft tissues, the replacement of extensive bone loss, and also it is a less expensive operation. It has been already confirmed that treatment of lyophilised allografts with albumin improves the ability of bone marrow-derived mesenchymal stem cells to adhere and proliferate the surface of the allografts, penetrate the pores and reach deeper layers of the graft. Earlier studies have shown osteoblast activity on the surface and interior of the graft.

Bone replacement and the use of bone supplementary biological substances have become widespread in clinical practice. Although autografts have excellent properties, their limited availability, difficulties with shaping and donor site morbidity have made allografts a viable and increasingly preferred alternative. The main drawback of allografts is that the preparation destroys osteogenic cells and results in denaturation of osteoinductive proteins. Serum albumin is a well-known constituent of stem cell culture media and we found that lyophilizing albumin onto bone allografts markedly improves stem-cell attachment and bone healing in animal models thus replacing some of the osteoinductive potential. As a first step in the clinical introduction of albumin coated grafts, we aimed to test surgical handling and early incorporation in aseptic revision arthroplasty in humans. We selected patients who needed large structural allografts and the current operation was the last attempt at preserving a moving joint. In a series of 10 cases of hip and knee revision surgery we did not experience any drawbacks of the albumin-coated grafts during handling and implantation. Twelve months radiographic and SPECT-CT follow-up showed that the graft was well received by the host and active remodelling was observed. The lack of graft-related complications and the good 1-year results indicate that controlled trials may be initiated in more common bone grafting indications where long-term effectiveness can be evaluated.

Mineralized scaffolds are widely used as bone grafts with the assumption that bone marrow derived cells colonize and remodel them. This process is slow and often unreliable so we aimed to improve the biocompatibility of bone grafts by pre-seeding them with human mesenchymal stem cells from either bone marrow or dental pulp. Under standard cell culture conditions very low number of seeded cells remained on the surface of freeze-dried human or bovine bone graft or hydroxyapatite. Coating the scaffolds with fibronectin or collagen improved seeding efficiency but the cells failed to grow on the surface until the 18th day. In contrast, human albumin was a very potent facilitator of both seeding and proliferation on allografts which was further improved by culturing in a rotating bioreactor. Electron microscopy revealed that cells do not form a monolayer but span the pores, emphasizing the importance of pore size and microstructure. Albumin coated bone chips were able to unite a rat femoral segmental defect, while uncoated ones did not. Micro-hardness measurements confirmed that albumin coating does not influence the physical characteristics of the scaffold, so it is possible to introduce albumin coating into the manufacturing process of lyophilized bone allografts.

In most cases of vascular repair a graft implantation is needed. Homografts have been proven to be suitable conduits when no autogenous graft is available. High viability index of vein homograft was confirmed during long term refrigerated storage in tissue culture medium, however there was no data of successful implanted cases. We report two cases of great saphenous vein (GSV) homograft implantation with excellent early results. In the first case graft-popliteal bypass was performed with vein homograft after septic ilio-femoral Dacron graft explantation and aorto-bifemoral Silver bypass procedure. Septic crossover synthetic bypass was replaced with GSV homograft in the second case. Long term storage of vein allografts at 4 C is a valuable and cost-effective option for revascularization and we propose wide-scale introduction of this method.

One of the most important factors concerning the successful clinical outcome after transplantation of osteochondral allografts is the viability of the cartilage.The viability of cryopreserved cartilage is quite poor, 20-30% cell survival has been published. The purpose of this study was to develop a new storage method which improves the chondrocyte viability. The talus of cadaveric donors was used as a model tissue to compare human osteochondral allograft cartilage viability following cryopreservation with that remaining after prolonged refrigerated storage. Full-thickness cartilage punch biopsies had been cryopreserved, and tali were divided into two matched groups and stored in TCM for 60 days at +4 degrees C, either with or without regular medium replacement. The cartilage of each graft was biopsied and assayed for viability on every third day by the MTT reduction assay. During 4 degrees C storage, a recurring pattern of large fluctuations in apparent cartilage viability was observed in every stored graft, with or without medium replacement. These fluctuations did not appear in control specimens of either fresh or cryopreserved human skin that were assayed in parallel with the cartilage biopsies, so the viability fluctuation seems an intrinsic property of the cartilage in these conditions. Cartilage stored for 60 days at +4 degrees C showed significantly higher viability (35.2 +/- 3.3 %) than fresh cartilage that had been cryopreserved (21.6 +/- 1.8 %). This was true even when cryopreserved and thawed cartilage was subjected to a 3 day post thaw incubation under presumably favorable conditions (17.7 +/- 1.6 %). These viability assay results, (reflective of intracellular metabolic activity), were corroborated by the fluorescent dye mixture SYTO-16 and propidium iodide. The data indicate that long-term stored refrigerated cartilage appears to retain a viability higher than that of cryopreserved cartilage for up to and perhaps beyond 60 days of storage. There was no viability index difference between the medium replaced and non-replaced groups. Although an exceptional result, in one individual case, more than 65% viable cells could be detected in the talar cartilage after 60 days storage at +4 degrees C.

The aim of this study was to adapt a reliable, reproducible and simple viability assay for cartilage and osteochondral studies. The previous assays (radioisotope uptake, assessment of matrix components, histological methods, oxygen consumption etc.) were complex, laborious, time consuming or suffer from difficulty of interpretation. MTT assay was chosen because it has been widely and successfully used in different cell and tissue studies, but has not been published on human solid articular cartilage. Fresh intact cartilage samples of human tali were tested to investigate the assay. The reliability of the MTT assay was also tested by an fluorescent dye combination. The MTT assay is based on the production of purple formazan pigment from methyltetrazolium salt by the mitochondrial enzymes of viable chondrocytes. The enzyme kinetics of the reaction was also investigated because it was unknown in the case of cartilage. The amount of pigment formed can be measured by spectrophotometry after extraction by methyl cellosolve. The color density is proportional to mitochondrial enzyme activity, reflecting the number of viable chondrocytes. The optimal reagent concentration, biopsy size, and incubation period were established. There is a linear relationship between the cartilage weight and the pigment production activity. A 9.8% nonspecific raction was observed in the negative controls. The enzyme kinetics of the reaction was also investigated. The MTT clevage up to 0.1% (w/v) follows the Michaelis kinetics. We calculated the Michaelis constant (2835 +/- 130 microM), the maximal velocity (36 +/- 3.2 x 10(-5)microMsec(-1)) and the velocity constant (1.27 +/- 0.2 x 10(-7)sec(-1)) of the reaction. The latter is a significant marker for each tissue type. The viability of cartilage was also assessed and calculated by a fluorescent dye combination comprising 1 microg/ml propidium iodide (PI) and 4 microM/ml SYTO-16 stains. The PI stains dead cells (red fluorescence), the SYTO-16 stains live cells (green fluorescence). The staining can be visualised simultaneously, and the live/dead ratio can be calculated by image analysis software from saved image files. The MTT assay is a simple, non-expensive, efficient, reliable, reproducible, sensitive viability test for cartilage studies. The MTT reduction assay and the staining method were corrobative.

Clinical application of human freeze-dried bone matrix gelatin (BMG) in the bone-cysts is reported. The BMG is produced at the West Hungarian Regional Tissue Bank in Gyór under principles of the American and European Association of Tissue Banks. BMG was applied to fill bone cysts in maxilla and mandible. The BMG has many advantages in comparison to other materials in the management of maxillofacial cysts. Of 31 cases 28 primary bone-heating have been detected clinically assessed by X-ray and histologically in three cases there was secondary restoration. In the favourable courses very fast and effective restorations have been found. The authors possess very favorable experience on the field of implantation of human bone matrix gelatin and recommend its clinical application at the maxillofacial surgery.

After a short historical survey authors summarise the histological processes of the replacement of allogen spongiosa. They compare the characteristics of the autologous and homologous bone. They review the technology of the preparation of the lyophylised spongiosa. They mention the bonematrix gelatin, bone morphogenetic protein and the fibrin sealant which increases the formers effectiveness. They demonstrate their cases, some of them in detail. They pointed out the good clinical results and suggest wider application and further investigation.

After transplantation of allogeneic bone, cartilage and soft connective tissues different healing processes could be detected depending on the difference of host and graft antigenicities. If the graft antigens were removed completely, HLA, AB0 or Rh matching would not necessary. In case of bone tissue the most important step is the elimination of antigen rich bone marrow and other cells. After transplantation of soft connective tissues with low antigenicity the expected immune response is low. By means of proper pretreatment the antigenicity is diminishable. The best preservation method of bone and soft connective tissues is the freeze-drying. In case of those grafts where the viability of cells is crucial e.g. osteochondral allografts, cartilage, skin, heart valves, the cryopreservation is thought to be the best preservation method. After transplantation immunosuppression is not necessary. The correct donor selection and the graft sterility are the most important, in respect successful clinical application. The evoked immune response generally does not reach that level which could damage graft or host.

Authors describe the considerations supporting the use of cadaveric skin homografts. The surgical relations of the burns, the site and advantages of the application of the homografts in the treatment of the burned patients are summarized.