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Biomedical subjects

M Manninen

Publications and source records attributed to M Manninen.

At least 37 records · Page 2Linked to original sources
PubMed1994

Tissue-implant interface at an absorbable fracture fixation plug made of polylactide in cancellous bone of distal rabbit femur.

The tissue-implant interface at a self-reinforced poly-L-lactide (SR-PLLA) expansion plug implanted in distal rabbit femoral cancellous bone was studied histologically, histomorphometrically, and microradiographically in 35 rabbits during consolidation of a transverse transcondylar osteotomy fixed with the SR-PLLA expansion plug. The absorbable plug for internal fixation of fractures and osteotomies measured 4.5 mm in diameter and 30 mm in length and had an expandable distal locking blade system. The femoral specimens were harvested in groups of 5-10 rabbits after a follow-up time of 3, 6, 12, and 24 weeks. The intact contralateral femur served as a control. Vigorous osteogenic response to the implant was already observed at 3 weeks postoperatively, and the osteoid surface fraction at 24 weeks was still significantly higher than in the unoperated contralateral femur. Incomplete union of the osteotomy seemed to result in increased fibrous tissue formation at the tissue-implant boundary. No signs of degradation of the SR-PLLA was observed within the entire follow-up period. The number of inflammatory cells at the tissue-implant interface was low. Consequently, the short-term biocompatibility of the implant was deemed acceptable. Clinical application of the expansion plug is being planned.

Animals↗
PubMed1994

Shear strength of a distal rabbit femur during consolidation of an osteotomy fixed with a polylactide expansion plug.

The consolidation of a transverse transcondylar osteotomy of the distal rabbit femur, fixed with a self-reinforced polylactide expansion plug, was studied radiographically and mechanically. The peak shear force was assessed by stressing the osteotomy site to failure. The intact contralateral femur of the same rabbit served as a control. Fifteen rabbits were tested in groups of five animals with follow-up times of 6, 12 or 24 wk after fixation of the osteotomy. The absorbable plug, measuring 4.5 mm in diameter and 30 mm in length, had an expandable distal locking blade system. Thirteen osteotomies showed a radiographically solid bony union. The mean shear strength of the specimens was 3.5 MPa at 6 wk, 3.5 MPa at 12 wk and 4.3 MPa at 24 wk. The mean shear strength of the control distal femora was 3.6 MPa. In conclusion, the fixation properties of the newly developed absorbable expansion plug were deemed satisfactory in this experimental fracture model.

Animals↗
PubMed1994

Absorbable plugs of self-reinforced poly-L-lactic acid in the internal fixation of rabbit distal femoral osteotomies.

An absorbable plug for the internal fixation of fractures and osteotomies, measuring 4.5 mm in diameter and 30 mm in length, was constructed of poly-L-lactide using a self-reinforcing fibers-in-matrix manufacturing technique. To increase the rotational stability and grip of the device, the plug has deployable distal fins. The plug was used in the fixation of a transverse distal femoral osteotomy in 20 rabbits. The consolidation of the osteotomy was investigated histologically, histomorphometrically, and microradiographically in groups of five rabbits observed for three, six, 12, or 24 weeks. Fifteen osteotomies showed bony union. In five rabbits, no bridging trabeculae across the osteotomy had developed, but these rabbits belonged to the groups with the shortest follow-up times of three or six weeks. No mechanical failures of the plugs were encountered, and the short-term biocompatibility of the implant was excellent. Future clinical applications are planned.

Animals↗
PubMed1992

Polymeric debris from absorbable polyglycolide screws and pins. Intraosseous migration studied in rabbits.

The migration of polymeric particles during degradation of absorbable implants made of polyglycolide was investigated in the cancellous bone of distal rabbit femur by using a transverse osteotomy model. The osteotomy was fixed either with a 4.5 x 25 mm screw or with two 1.5 x 30 mm pins. The histologic sections obtained at 3, 6, 12, and 36 weeks were morphometrically analyzed using polarized-light microscopy. The migration of the polymeric debris into the host-tissues showed two different patterns. On the one hand, particles were in all specimens seen lying intracellularly in phagocytic cells in a regular front close to the original tissue-implant boundary. In addition, in several specimens there occurred expansions filled with largely extracellular polymeric particles that bulged into the hematopoietic bone marrow up to 2.8 mm from the original implant cavity. This kind of particle migration over long distances could not be explained by cellular transport, but may have been caused by an increased osmotic pressure that developed within the implant cavity during depolymerization of polyglycolide.

Animals↗
PubMed1992

Degradation and tissue replacement of an absorbable polyglycolide screw in the fixation of rabbit femoral osteotomies.

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.

Animals↗
PubMed1992

The tissue-implant interface during degradation of absorbable polyglycolide fracture fixation screws in the rabbit femur.

A transverse transcondylar osteotomy of the distal femur was fixed with an axially placed absorbable fracture fixation screw made of polyglycolide (PGA) in 25 rabbits. Changes at the tissue-implant interface accompanying degradation of the screw were examined histologically, histomorphometrically, and microradiographically seven, 20, 40, 80, and 250 days after implantation. At seven days postimplantation, a layer of fibroblasts was seen surrounding the implant, and new bone formation was discernible in the host tissues adjacent to this membranous structure. At 20 days postimplantation, the geometry of the screw was still intact and the tissue-implant boundary was distinct. The first signs of invasion of vascular granulation tissue into the implant were observed 40 days after implantation, at which time the osteotomies were united. The apparent walling-off response by formation of new trabecular bone outlining the PGA profile continued, with the greatest mean trabecular bone volume fraction at the interface, 23.9%, measured at 40 days. A significant decrease in the new bone volume occurred between 40 and 80 days postimplantation. The intensity of the foreign-body reaction seen was histologically moderate. The giant cell count was highest at 80 days postimplantation, when the migratory activity of phagocytic cells had transported intracellular particulate polymeric debris 400-800 microns away from the original tissue-implant boundary. At 250 days postimplantation, no birefringent polymeric material could be seen in the specimens. No contraindications for the clinical application of PGA implants emerged in this study.

Animals↗
PubMed1991

Evaluation of a microbiological method for detection of irradiation of spices.

The suitability of a microbiological method, a combination of the direct epifluorescent filter technique (DEFT) and the total aerobic plate count (APC), for the detection of irradiation of spices was evaluated. The evaluation was carried out using different kinds of spices including peppers, paprika, cardamom, cinnamon, ginger; herbs such as thyme, marjoram, basil, and oregano; and garlic powder. Ground spices were tested as well as cut and whole spice samples. Samples were analysed before and after gamma-irradiation mainly with doses of 5 and 10 kGy. Two different methods (centrifugation, filtration) for sample pretreatment were compared. Differences between the DEFT count and the APC with doses of 5 and 10 kGy varied between 3.9 and 6.8 and between 5.7 and 7.5 log units, respectively. The duration of storage after irradiation had no effect on the microbiological results. When applied to fumigated samples, the method might cause confusion in the absence of chemical analyses. The results of the analyses of samples treated by an unknown process indicated that the method could, in fact, detect irradiated samples, although it could not differentiate between irradiated and heat-treated samples.

Bacteria↗