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Pentti Rokkanen - One of the best experts on this subject based on the ideXlab platform.
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Tissue response to Polyglycolide and polylevolactide pins in osteotomized cancellous bone.
Clinical orthopaedics and related research, 2001Co-Authors: Pia Nordström, Harri Pihlajamäki, Pertti Tormala, T. Toivonen, Pentti RokkanenAbstract:A transcondylar osteotomy of the distal femur was fixed with a self-reinforced Polyglycolide pin in one hind leg and with a self-reinforced polylevolactide pin in the other hind leg of 49 rats. The intact femurs of eight rats that did not have surgical treatment were used as controls. The tissue reaction to the implant and the consolidation of the osteotomy were examined radiographically, histologically, histomorphometrically, microradiographically, and using oxytetracycline fluorescence studies. The followups were from 1 to 52 weeks. A vigorous osteostimulatory tissue response to self-reinforced Polyglycolide pins and self-reinforced polylevolactide pins was observed 1 week after fixation. This reaction reached its highest value 24 weeks after self-reinforced Polyglycolide pin fixation and 6 weeks after self-reinforced polylevolactide pin fixation. The highest values of the mean trabecular bone area fraction, 27.9% for self-reinforced Polyglycolide pins and 28.1% for self-reinforced polylevolactide pins, were measured at 48 weeks. At 12 weeks there was a peak of phagocytizing macrophages in the specimens with self-reinforced Polyglycolide pin fixation. During the followup, total phagocytosis of self-reinforced Polyglycolide pins was seen, but only a few signs of degradation of self-reinforced polylevolactide pins were observed. Both polymeric implants seemed to possess osteostimulatory properties, and the biocompatibility and clinical relevance proved to be acceptable.
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Tissue response to Polyglycolide and polylactide pins in cancellous bone.
Archives of orthopaedic and trauma surgery, 1998Co-Authors: Pia Nordström, T. Toivonen, P. Törmälä, H Pihlajamäki, Pentti RokkanenAbstract:An absorbable self-reinforced Polyglycolide (SR-PGA) pin, 2.0 mm in diameter and 15 mm in length, was implanted in the trabecular bone areas of the distal femur of 51 rats and a biodegradable self-reinforced poly-L-lactide (SR-PLLA) pin of the same size was inserted into the distal femur of the other hind leg of the same rats. The intact femora of eight non-operated rats were used as controls. Tissue reaction to the implants was examined within standardized sample fields radiographically, histologically, histomorphometrically, microradiographically and using oxytetracycline fluorescence studies. The follow-up periods of the groups consisting of five operated rats and one intact control rat were 1, 3, 6, 12, 24, 36, 48 and 52 weeks. Eleven extra rats were operated on to ensure five samples in each follow-up group for the final analyses. The first signs of degradation of the SR-PGA pin were seen at 3 weeks, and the pin was totally degraded by 36 weeks. No signs of degradation of the SR-PLLA pin were observed during the follow-up period. Active new bone formation was seen close to the implant profile at 1 week in both groups. At 12 weeks the mean fractional osteoid formation surface was statistically significantly (P < 0.01) higher in the SR-PGA-implanted specimens than in the SR-PLLA-implanted specimens. At that time there were also statistically significantly (P < 0.05) more phagocyting macrophages in the SR-PGA-implanted specimens than in the SR-PLLA-implanted specimens, which is in accordance with the degradation behaviour of both implants. The biocompatibility of Polyglycolide and polylactide proved to be good.
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Absorbable fixation of femoral head fractures. A prospective study of six cases.
Annales chirurgiae et gynaecologiae, 1998Co-Authors: Kirsi Jukkala-partio, Eero Hirvensalo, Pentti RokkanenAbstract:Background and aims Fracture of the femoral head associated with a traumatic dislocation of the hip is a rare but severe injury. The methods of the recommended treatment have varied from primary closed or open reduction without fixation to excision of fragments or internal fixation. In our department we have treated other kinds of intra-articular fractures successfully with totally absorbable Polyglycolide and poly-L-lactide implants. The aim of this study was to investigate the value of totally absorbable rods and screws in the fixation of the femoral head fractures. Material and methods Six femoral head fractures associated with a posterior traumatic dislocation of the hip were treated by open reduction and internal fixation using self-reinforced absorbable Polyglycolide (SR-PGA) or poly-L-lactide (SR-PLLA) rods and screws. The follow-up time was 38 months in average (range 6 weeks to 77 months). Results In three patients the end results were excellent and in one fair. One patient died six weeks after the accident from the consequences of the cerebral injury. In one 61-year-old patient an arthroplasty was performed one year after the primary osteosynthesis, because of avascular necrosis of the femoral head. Conclusions Self-reinforced Polyglycolide and polylactide implants can be used safely to fix femoral head fractures without the need of implant removal.
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Absorbable Polyglycolide devices in trauma and bone surgery.
Biomaterials, 1997Co-Authors: Nureddin Ashammakhi, Pentti RokkanenAbstract:Poly(glycolic acid) or Polyglycolide (PGA) is a polymer of glycolic acid. Glycolic acid is produced during normal body metabolism and is known as hydroxyacetic acid. Strong implants can be manufactured from this polymer with a self-reinforcing (SR) technique and used in the treatment of fractures and osteotomies. Since 1984, SR-PGA implants have been used routinely in our hospital for internal fixation of bone fractures. These implants were studied extensively in experimental animals and proved biocompatible. In 1.7% of human cases, sinus formation may develop after the use of these implants, which does not disturb healing. Use of these absorbable implants is justified as it obviates the need for a second operation for implant removal and avoids the risks associated with biostable implants.
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Osteolytic Changes After Polyglycolide Pin Fixation in Chevron Osteotomy
Foot & ankle international, 1997Co-Authors: Kia Pelto-vasenius, Jarkko Vasenius, Eero Hirvensalo, Pentti RokkanenAbstract:Absorbable Polyglycolide pins were used for fixation of 94 chevron osteotomies in 70 patients at the Department of Orthopaedics and Traumatology, Helsinki University Central Hospital, between 1986 and 1992. Postoperative osteolytic changes around the degrading pin occurred in 21 of 94 (22%) metatarsal heads. In 17 of 21 metatarsal heads, polydioxanone-coated Polyglycolide pins were used. This type of pin has not been used since 1988. At follow-up, 16 of 21 osteolytic changes resolved completely and four partially resolved. In the remaining one, the osteolytic area remained visible after 6 years. Cystic changes in the metatarsal head, not attributable to the location of the absorbable implants, occurred in seven (7.4%) metatarsal heads and avascular necrosis of the entire metatarsal head in one (1.1%). Foreign body reaction occurred in six (6.3%) metatarsal heads and wound infection in three (3.2%) metatarsal heads. No association was observed between osteolytic changes and foreign body reaction or infecti...
Pertti Tormala - One of the best experts on this subject based on the ideXlab platform.
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Bioabsorbable Ciprofloxacin-Containing and Plain Self-Reinforced Polylactide-Polyglycolide 80/20 Screws: Pullout Strength Properties in Human Cadaver Parietal Bones
Journal of Craniofacial Surgery, 2002Co-Authors: Johanna Tiainen, Pertti Tormala, Minna Veiranto, Esa Suokas, Timo Waris, Milomir Ninkovic, Nureddin AshammakhiAbstract:The aim of this study was to compare the pullout forces of recently developed bioabsorbable ciprofloxacin-containing and plain self-reinforced polylactide/Polyglycolide (SR-PLGA) miniscrews in human cadaver parietal bones. Parietal bone pieces (approximately 6 × 20 cm) were collected from five human
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bioabsorbable ciprofloxacin containing and plain self reinforced polylactide Polyglycolide 80 20 screws pullout strength properties in human cadaver parietal bones
Journal of Craniofacial Surgery, 2002Co-Authors: Johanna Tiainen, Pertti Tormala, Minna Veiranto, Esa Suokas, Timo Waris, Milomir Ninkovic, Nureddin AshammakhiAbstract:The aim of this study was to compare the pullout forces of recently developed bioabsorbable ciprofloxacin-containing and plain self-reinforced polylactide/Polyglycolide (SR-PLGA) miniscrews in human cadaver parietal bones. Parietal bone pieces (approximately 6 × 20 cm) were collected from five human
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Tissue response to Polyglycolide and polylevolactide pins in osteotomized cancellous bone.
Clinical orthopaedics and related research, 2001Co-Authors: Pia Nordström, Harri Pihlajamäki, Pertti Tormala, T. Toivonen, Pentti RokkanenAbstract:A transcondylar osteotomy of the distal femur was fixed with a self-reinforced Polyglycolide pin in one hind leg and with a self-reinforced polylevolactide pin in the other hind leg of 49 rats. The intact femurs of eight rats that did not have surgical treatment were used as controls. The tissue reaction to the implant and the consolidation of the osteotomy were examined radiographically, histologically, histomorphometrically, microradiographically, and using oxytetracycline fluorescence studies. The followups were from 1 to 52 weeks. A vigorous osteostimulatory tissue response to self-reinforced Polyglycolide pins and self-reinforced polylevolactide pins was observed 1 week after fixation. This reaction reached its highest value 24 weeks after self-reinforced Polyglycolide pin fixation and 6 weeks after self-reinforced polylevolactide pin fixation. The highest values of the mean trabecular bone area fraction, 27.9% for self-reinforced Polyglycolide pins and 28.1% for self-reinforced polylevolactide pins, were measured at 48 weeks. At 12 weeks there was a peak of phagocytizing macrophages in the specimens with self-reinforced Polyglycolide pin fixation. During the followup, total phagocytosis of self-reinforced Polyglycolide pins was seen, but only a few signs of degradation of self-reinforced polylevolactide pins were observed. Both polymeric implants seemed to possess osteostimulatory properties, and the biocompatibility and clinical relevance proved to be acceptable.
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Evaluation of self-reinforced Polyglycolide membrane implanted in the subcutis of rabbits.
Annales chirurgiae et gynaecologiae, 1999Co-Authors: Martti M. Ruuskanen, Pertti Tormala, Nureddin Ashammakhi, Timo Pohjonen, Matti Kallioinen, Timo WarisAbstract:BACKGROUND Self-reinforced absorbable implants have been developed recently to use in hard tissue reconstructive surgery. Polyglycolide is a biocompatible polymer from which the suture Dexon is made and widely used. AIMS To study histologically the behaviour of self-reinforced Polyglycolide membrane (SR-PGA) in rabbits' ears. MATERIAL AND METHODS SR-PGA membranes, 0.4 mm thick, were implanted in the subcutis of the ears of 24 New Zealand white rabbits. Sham operations were carried out on the contralateral ear of each rabbit. The rabbits were followed-up for 4, 12 and 20 weeks. Attention was directed towards external macroscopic changes in the rabbits' ears. After sacrifice, the ears were taken as specimens, inspected for any evidence of infection, sinus formation or fluid accumulation and histological examination was carried out. RESULTS No complications such as infection, fluid accumulation or sinus formation were observed. Histologically, the membranes induced a foreign-body reaction involving fibrous tissue encapsulation, macrophages and giant cells. Fibrous tissue and inflammatory cells were seen between the PGA fibres. The membranes underwent progressive degradation throughout the follow-up period. However, PGA material could be still seen 20 weeks postoperatively, with a small amount of fibrous tissue and macrophages and giant cells. The implant-cartilage interface comprised fibrous and fatty tissue. CONCLUSIONS SR-PGA membranes are biocompatible when implanted in the subcutis of the ears of rabbits.
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Strength retention of self-reinforced Polyglycolide membrane: An experimental study
Biomaterials, 1995Co-Authors: Nureddin Ashammakhi, Kimmo Vihtonen, Pentti Rokkanen, Hilkka Kuisma, Pertti TormalaAbstract:Self-reinforced Polyglycolide (SR-PGA) devices are stronger than non-reinforced ones. To study the strength retention of SR-PGA membrane, in vitro and in vivo, membranes were either immersed in distilled water at 37 degrees C, or implanted in the subcutis or around the femoral bone of rats. The SR-PGA membranes lost their strength in vitro by 6 wk, while they retained it for 15 wk in vivo due to the fibrous tissue that formed around and inside the implant (biomembrane). This is an advantage when clinical application of the membrane is being considered.
Jarkko Vasenius - One of the best experts on this subject based on the ideXlab platform.
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Osteolytic Changes After Polyglycolide Pin Fixation in Chevron Osteotomy
Foot & ankle international, 1997Co-Authors: Kia Pelto-vasenius, Jarkko Vasenius, Eero Hirvensalo, Pentti RokkanenAbstract:Absorbable Polyglycolide pins were used for fixation of 94 chevron osteotomies in 70 patients at the Department of Orthopaedics and Traumatology, Helsinki University Central Hospital, between 1986 and 1992. Postoperative osteolytic changes around the degrading pin occurred in 21 of 94 (22%) metatarsal heads. In 17 of 21 metatarsal heads, polydioxanone-coated Polyglycolide pins were used. This type of pin has not been used since 1988. At follow-up, 16 of 21 osteolytic changes resolved completely and four partially resolved. In the remaining one, the osteolytic area remained visible after 6 years. Cystic changes in the metatarsal head, not attributable to the location of the absorbable implants, occurred in seven (7.4%) metatarsal heads and avascular necrosis of the entire metatarsal head in one (1.1%). Foreign body reaction occurred in six (6.3%) metatarsal heads and wound infection in three (3.2%) metatarsal heads. No association was observed between osteolytic changes and foreign body reaction or infecti...
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Absorbable self-reinforced Polyglycolide (SR-PGA) screws for the fixation of fractures and osteotomies: strength and strength retention in vitro and in vivo.
Clinical materials, 1994Co-Authors: Jarkko Vasenius, Pentti Rokkanen, Pertti Helevirta, Hilkka Kuisma, Pertti TormalaAbstract:The initial mechanical strength and strength retention in vitro and in vivo of novel absorbable and self-reinforced Polyglycolide (SR-PGA) screws for the fixation of fractures and osteotomies were determined. The SR-PGA screws showed initial bending strength values comparable with those of yield strength of standard stainless steel. The SR-PGA screws lost all their bending and shear strengths in 6 weeks in vivo. The strength retention properties of SR-PGA screws are sufficient for safe fixation of relatively rapidly consolidating fractures and osteotomies of cancellous bone that are not exposed to hard mechanical stresses.
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Degradation and tissue replacement of an absorbable Polyglycolide screw in the fixation of rabbit femoral osteotomies.
The Journal of bone and joint surgery. American volume, 1992Co-Authors: Ole Böstman, Jarkko Vasenius, Esa K. Partio, Unto Päivärinta, M. Manninen, Pentti RokkanenAbstract:Degradation and tissue replacement of a totally absorbable Polyglycolide screw, 4.5 millimeters in diameter and thirty millimeters in length, were studied histologically, morphometrically, and radiographically at sequential stages of resorption at as long as thirty-six weeks after fixation of a transverse distal femoral osteotomy in rabbits. The initial mean shear force to failure was 95.0 newtons for the specimens that had been fixed with the Polyglycolide screw compared with 257.0 newtons for the distal part of the contralateral, intact femur. The physical appearance of the screw was unaltered at three weeks. The first histological signs of degradation were seen at six weeks, along the thread ridge. Premature breakage of the screw resulted in gross displacement and non-union of the osteotomy in one animal. The degradation of Polyglycolide was accompanied histologically by a typical non-specific foreign-body reaction. This kind of tissue response seemed to be associated with an osteolytic proximal expansion of the implant cavity that was suggestive of increased pressure within the cavity during degradation of the screw. In eight specimens, a wall of new bone formed around this area of osteolysis and demarcated the implant cavity from the surrounding normal cancellous bone. Seventy-four per cent of the periphery and 28 per cent of the central core of the screw had been resorbed at twelve weeks. At thirty-six weeks, no polymeric material could be discerned, and the predominant tissue component within the implant cavity was loose connective tissue. The volume fractions of trabecular bone and hematopoietic bone marrow were significantly lower (p less than 0.01) than those of the intact, control side, but the degree of restoration of tissue varied considerably from animal to animal.
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Strength retention of self‐reinforced, absorbable Polyglycolide rods in hydrolytic environment
Angewandte Makromolekulare Chemie, 1991Co-Authors: Pertti Tormala, Jarkko Vasenius, Heta‐maija Mikkola, Vainionpää S, Pentti RokkanenAbstract:Absorbable Polyglycolide suture fibers were sintered with the compression molding techniques to cylindrical rods at temperatures between 205°C and 232°C for 3–5 min with final pressures of 50–80 N/mm2. The cylindrical rods had nominal diameters between 1.5–4.5 mm and a length of 50 mm. The initial bending moduli and the initial bending strengths of the rods were between 9–15 GPa and 220–430 MPa, respectively. The shear strengths of the rods were between 165–255 MPa. The hydrolytic loss of mechanical strength of the above self-reinforced, absorabable Polyglycolide rods were studied in phosphate buffer at 37°C and 77°C. It was found that the rate of strength loss decreases with the increasing diameter of the rods. On the other hand, the rate of strength loss increases when the temperature of the buffer solution is raised. The strength, retention time at 37°C was between 7–10 weeks showing that the loss of mechanical strength of self-reinforced Polyglycolide rods occurs more rapidly in vivo than in vitro.
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Ultra‐high‐strength absorbable self‐reinforced Polyglycolide (SR‐PGA) composite rods for internal fixation of bone fractures: In vitro and in vivo study
Journal of biomedical materials research, 1991Co-Authors: Pertti Tormala, Jarkko Vasenius, Seppo Vainionpää, Juha Laiho, Timo Pohjonen, Pentti RokkanenAbstract:The ultra-high-strength, self-reinforced (SR) absorbable polymeric composites, consisting of reinforcement elements, like fibers, and of matrix polymer which have the same chemical element composition as reinforcement, were defined. A method to manufacture self-reinforced, absorbable Polyglycolide (SR-PGA) rods of Polyglycolide sutures (Dexon) by sintering them partially together at elevated temperature and pressure was presented. The rods with nominal diameters of 1.5 mm, 2.0 mm, 3.2 mm, and 4.5 mm showed initial bending modulus and strength values of 8-15 GPa and 220-405 MPa, respectively. Their initial shear strengths were 165-255 MPa. The smallest rods (diam. 1.5 mm) lost their mechanical strength after implantation in the subcutis of rabbits in 4-5 weeks while the thickest rods retained their strength over 8 weeks. The ultra-high-strength SR-PGA rods were concluded to be suitable for fixation of cancellous bone fractures, osteotomies, and epiphyseal plate fractures where the fixation is not exposed to excessive mechanical stresses and where the loads are predominantly of a shear nature.
Nureddin Ashammakhi - One of the best experts on this subject based on the ideXlab platform.
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Bioabsorbable Ciprofloxacin-Containing and Plain Self-Reinforced Polylactide-Polyglycolide 80/20 Screws: Pullout Strength Properties in Human Cadaver Parietal Bones
Journal of Craniofacial Surgery, 2002Co-Authors: Johanna Tiainen, Pertti Tormala, Minna Veiranto, Esa Suokas, Timo Waris, Milomir Ninkovic, Nureddin AshammakhiAbstract:The aim of this study was to compare the pullout forces of recently developed bioabsorbable ciprofloxacin-containing and plain self-reinforced polylactide/Polyglycolide (SR-PLGA) miniscrews in human cadaver parietal bones. Parietal bone pieces (approximately 6 × 20 cm) were collected from five human
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bioabsorbable ciprofloxacin containing and plain self reinforced polylactide Polyglycolide 80 20 screws pullout strength properties in human cadaver parietal bones
Journal of Craniofacial Surgery, 2002Co-Authors: Johanna Tiainen, Pertti Tormala, Minna Veiranto, Esa Suokas, Timo Waris, Milomir Ninkovic, Nureddin AshammakhiAbstract:The aim of this study was to compare the pullout forces of recently developed bioabsorbable ciprofloxacin-containing and plain self-reinforced polylactide/Polyglycolide (SR-PLGA) miniscrews in human cadaver parietal bones. Parietal bone pieces (approximately 6 × 20 cm) were collected from five human
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Evaluation of self-reinforced Polyglycolide membrane implanted in the subcutis of rabbits.
Annales chirurgiae et gynaecologiae, 1999Co-Authors: Martti M. Ruuskanen, Pertti Tormala, Nureddin Ashammakhi, Timo Pohjonen, Matti Kallioinen, Timo WarisAbstract:BACKGROUND Self-reinforced absorbable implants have been developed recently to use in hard tissue reconstructive surgery. Polyglycolide is a biocompatible polymer from which the suture Dexon is made and widely used. AIMS To study histologically the behaviour of self-reinforced Polyglycolide membrane (SR-PGA) in rabbits' ears. MATERIAL AND METHODS SR-PGA membranes, 0.4 mm thick, were implanted in the subcutis of the ears of 24 New Zealand white rabbits. Sham operations were carried out on the contralateral ear of each rabbit. The rabbits were followed-up for 4, 12 and 20 weeks. Attention was directed towards external macroscopic changes in the rabbits' ears. After sacrifice, the ears were taken as specimens, inspected for any evidence of infection, sinus formation or fluid accumulation and histological examination was carried out. RESULTS No complications such as infection, fluid accumulation or sinus formation were observed. Histologically, the membranes induced a foreign-body reaction involving fibrous tissue encapsulation, macrophages and giant cells. Fibrous tissue and inflammatory cells were seen between the PGA fibres. The membranes underwent progressive degradation throughout the follow-up period. However, PGA material could be still seen 20 weeks postoperatively, with a small amount of fibrous tissue and macrophages and giant cells. The implant-cartilage interface comprised fibrous and fatty tissue. CONCLUSIONS SR-PGA membranes are biocompatible when implanted in the subcutis of the ears of rabbits.
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Absorbable Polyglycolide devices in trauma and bone surgery.
Biomaterials, 1997Co-Authors: Nureddin Ashammakhi, Pentti RokkanenAbstract:Poly(glycolic acid) or Polyglycolide (PGA) is a polymer of glycolic acid. Glycolic acid is produced during normal body metabolism and is known as hydroxyacetic acid. Strong implants can be manufactured from this polymer with a self-reinforcing (SR) technique and used in the treatment of fractures and osteotomies. Since 1984, SR-PGA implants have been used routinely in our hospital for internal fixation of bone fractures. These implants were studied extensively in experimental animals and proved biocompatible. In 1.7% of human cases, sinus formation may develop after the use of these implants, which does not disturb healing. Use of these absorbable implants is justified as it obviates the need for a second operation for implant removal and avoids the risks associated with biostable implants.
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Strength retention of self-reinforced Polyglycolide membrane: An experimental study
Biomaterials, 1995Co-Authors: Nureddin Ashammakhi, Kimmo Vihtonen, Pentti Rokkanen, Hilkka Kuisma, Pertti TormalaAbstract:Self-reinforced Polyglycolide (SR-PGA) devices are stronger than non-reinforced ones. To study the strength retention of SR-PGA membrane, in vitro and in vivo, membranes were either immersed in distilled water at 37 degrees C, or implanted in the subcutis or around the femoral bone of rats. The SR-PGA membranes lost their strength in vitro by 6 wk, while they retained it for 15 wk in vivo due to the fibrous tissue that formed around and inside the implant (biomembrane). This is an advantage when clinical application of the membrane is being considered.
Seppo Vainionpää - One of the best experts on this subject based on the ideXlab platform.
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Ultra‐high‐strength absorbable self‐reinforced Polyglycolide (SR‐PGA) composite rods for internal fixation of bone fractures: In vitro and in vivo study
Journal of biomedical materials research, 1991Co-Authors: Pertti Tormala, Jarkko Vasenius, Seppo Vainionpää, Juha Laiho, Timo Pohjonen, Pentti RokkanenAbstract:The ultra-high-strength, self-reinforced (SR) absorbable polymeric composites, consisting of reinforcement elements, like fibers, and of matrix polymer which have the same chemical element composition as reinforcement, were defined. A method to manufacture self-reinforced, absorbable Polyglycolide (SR-PGA) rods of Polyglycolide sutures (Dexon) by sintering them partially together at elevated temperature and pressure was presented. The rods with nominal diameters of 1.5 mm, 2.0 mm, 3.2 mm, and 4.5 mm showed initial bending modulus and strength values of 8-15 GPa and 220-405 MPa, respectively. Their initial shear strengths were 165-255 MPa. The smallest rods (diam. 1.5 mm) lost their mechanical strength after implantation in the subcutis of rabbits in 4-5 weeks while the thickest rods retained their strength over 8 weeks. The ultra-high-strength SR-PGA rods were concluded to be suitable for fixation of cancellous bone fractures, osteotomies, and epiphyseal plate fractures where the fixation is not exposed to excessive mechanical stresses and where the loads are predominantly of a shear nature.
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ultra high strength absorbable self reinforced Polyglycolide sr pga composite rods for internal fixation of bone fractures in vitro and in vivo study
Journal of Biomedical Materials Research, 1991Co-Authors: Pertti Tormala, Jarkko Vasenius, Seppo Vainionpää, Juha Laiho, Timo Pohjonen, Pentti RokkanenAbstract:The ultra-high-strength, self-reinforced (SR) absorbable polymeric composites, consisting of reinforcement elements, like fibers, and of matrix polymer which have the same chemical element composition as reinforcement, were defined. A method to manufacture self-reinforced, absorbable Polyglycolide (SR-PGA) rods of Polyglycolide sutures (Dexon) by sintering them partially together at elevated temperature and pressure was presented. The rods with nominal diameters of 1.5 mm, 2.0 mm, 3.2 mm, and 4.5 mm showed initial bending modulus and strength values of 8-15 GPa and 220-405 MPa, respectively. Their initial shear strengths were 165-255 MPa. The smallest rods (diam. 1.5 mm) lost their mechanical strength after implantation in the subcutis of rabbits in 4-5 weeks while the thickest rods retained their strength over 8 weeks. The ultra-high-strength SR-PGA rods were concluded to be suitable for fixation of cancellous bone fractures, osteotomies, and epiphyseal plate fractures where the fixation is not exposed to excessive mechanical stresses and where the loads are predominantly of a shear nature.
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Chevron Osteotomy Fixed with Absorbable Polyglycolide Pins
Foot & ankle, 1991Co-Authors: Eero Hirvensalo, Ole Böstman, Seppo Vainionpää, Pertti Tormala, Pentti RokkanenAbstract:Seventy-eight chevron osteotomies augmented by internal fixation with self-reinforced Polyglycolide pins, 2 mm in diameter, were performed in 60 patients suffering from a painful hallux valgus. The mean metatarsophalangeal angle was 31°, and there was a metatarsus primus varus varying from 10° to 20°. The average follow-up time was 14 (range, 12 to 31) months. No postoperative redisplacement or disturbance of healing of the osteotomy was observed, but recurrence of hallux valgus occurred in 8 feet (10%), each initially with a moderate to severe hallux valgus. Some pain at the first metatarsophalangeal joint during physical activity remained in 12 feet (15%). There was a mean shortening of 2.5 mm of the first metatarsal bone, and the most significant shortening was associated with pain in the forefoot. The metatarsophalangeal joint motion was not decreased. The subjective overall result was excellent or good in 75% of the patients. Because of the biodegradability of the implants used, no secondary procedur...
