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Biomedical subjects

M Manninen

Publications and source records attributed to M Manninen.

At least 19 recordsLinked to original sources
PubMed2001

Inability of transforming growth factor-beta 1, combined with a bioabsorbable polymer paste, to promote healing of bone defects in the rat distal femur.

The ability of transforming growth factor-beta 1 (TGF-beta 1) to promote bone formation suggests that it may have potential as a therapeutic agent in bone defects. However, there still exists a need for an effective method of delivering TGF-beta 1 to the site of an osseous defect. In the present study, TGF-beta 1 was embedded in a bioabsorbable polymer paste (a blend of an L-lactide oligomer and a copolymer of epsilon-caprolactone and DL-lactide). The release of TGF-beta 1 from the polymer paste was examined in vitro with an enzyme-linked immunosorbent assay, which showed sustained release of active TGF-beta 1 over a 7-day period. Further, the polymer paste was used to fill a bone defect in the rat distal femur. The amount of TGF-beta 1 per rat was 50 micrograms, while in a control group we used an identical polymer paste without the growth factor. After a follow-up of 1 week and 3 weeks, the femurs were examined radiographically, histologically, histomorphometrically, microradiographically, and were also used for tetracycline-labeling studies. TGF-beta 1 did not enhance healing of the bone defect. A combination of growth factors would probably be a more potent osteoinductor than TGF-beta 1 alone.

Animals↗
PubMed2000

Thermal expansion in small metal clusters and its impact on the electric polarizability

The thermal expansion coefficients of Na(N) clusters with 8</=N</=40, and Al7, Al-13, and Al-14 clusters are obtained from ab initio Born-Oppenheimer local-density-approximation molecular dynamics. Thermal expansion of small metal clusters is considerably larger than that in the bulk and is size dependent. We demonstrate that the average static electric dipole polarizability of Na clusters depends linearly on the mean interatomic distance and only to a minor extent on the detailed ionic configuration when the overall shape of the electron density is enforced by electronic shell effects. Taking thermal expansion into account brings theoretical and experimental polarizabilities into quantitative agreement.

Journal Article↗
PubMed1999

Combining transforming growth factor-beta(1) to a bioabsorbable self-reinforced polylactide pin for osteotomy healing: an experimental study on rats.

The effect of a bioabsorbable pin containing transforming growth factor-beta(1) on fracture healing was studied in a rat model. The growth factor was mixed into a bioabsorbable polymer paste (a blend of an l-lactic acid oligomer and a copolymer of epsilon-caprolactone and dl-lactide) that was used to fill the grooves of a self-reinforced fracture fixation pin made of a poly-ld-lactic acid copolymer. In an in vitro assay, sustained release of the growth factor from the pins over a 7-day period was demonstrated. A distal femoral osteotomy was made in 60 rats and stabilized with the fracture fixation pin in 48 of them; In the remaining 12 rats, no fixation was performed. The pin used in the study group contained either 5 microg (15 rats) or 50 microg (15 rats) of the growth factor, while in a control group of 18 rats an identical pin without the growth factor was used. After a follow-up of 1, 3, or 6 weeks, the femurs were examined radiographically, histologically, histomorphometrically, and microradiographically, and also used in tetracycline labeling studies. Faster callus formation was evident in the growth factor-treated rats but no acceleration in the healing of the osteotomy was detected.

Absorbable Implants↗
PubMed1998

Polylactide pin with transforming growth factor beta 1 in delayed osteotomy fixation.

The effect of an absorbable pin containing transforming growth factor beta 1 on fracture healing was studied in a rat model of delayed osteotomy fixation. Transforming growth factor beta 1 was mixed into a blend of L-lactide oligomer and a copolymer of epsilon-caprolactone and DL-lactide that was placed in the grooves of a self reinforced fracture fixation pin made of poly-LD-lactic acid copolymer. A distal femoral osteotomy was made in 54 rats and left untreated. A week later surgery was performed to fix the osteotomy with a fracture fixation pin in 48 rats. In the remaining six rats no fixation was performed. The pin that was used in the study group contained either 5 micrograms (15 rats) or 50 micrograms (15 rats) of the growth factor, while in the control group of 18 rats, an identical pin without growth factor was used. The femurs were examined radiographically, histologically, histomorphometrically, and microradiographically. Tetracycline labeling studies were used after a followup of 1, 3, and 6 weeks. Faster callus formation in the transforming growth factor beta 1 treated animals but no acceleration in the healing of the osteotomy is reported. The addition of bone growth factors to bioabsorbable fracture fixation materials may enhance bone healing.

Animals↗
PubMed1997

Complications of plate fixation in fresh displaced midclavicular fractures.

BACKGROUND: The role of plate fixation in the management of fresh displaced midclavicular fractures is unsettled. The objective of this study was to evaluate the drawbacks and pitfalls of this treatment method. METHODS: We analyzed the complications encountered in 103 consecutive adult patients with severely displaced fresh fractures of the middle third of the clavicle who were treated by open reduction and internal fixation using AO/ASIF plates. These 103 patients accounted for 9.5% of the 1,081 patients with fresh midclavicular fractures seen between 1989 and 1995. The mean age of the 103 patients was 33.4 years (range, 19-62 years). RESULTS: Seventy-nine patients had an uneventful recovery, whereas 24 (23%) suffered one or several complications. The major complications included deep infection, plate breakage, nonunion, and refracture after plate removal. The most common of the minor complications was plate loosening resulting in malunion. The infection rate was 7.8%. A total of 14 reoperations were performed because of the complications. Permanent nonunion ensued in two patients. A severely comminuted fracture (relative risk of failure, 5.15) as well as a state of alcohol intoxication on admission (relative risk of failure, 3.12) were identified as markers of increased complication risk. CONCLUSIONS: Patient noncompliance with the postoperative regimen could be suspected to have been a major cause of the failures. The high complication rate supports a reserved attitude toward plate fixation of fresh midclavicular fractures. The method should be reserved for patients who have trustworthy personal motives for quick pain relief and functional recovery.

Adult↗
PubMed1997

Extended high frequency hearing and history of acute otitis media in 14-year-old children in Finland.

We studied the extended high frequency hearing of 573 white, urban, mean 13.8-year-old unselected children in Tampere, Finland. All their ear-related morbidity had been recorded since their birth and they had been examined at the ages of 7 months, 2 years, and some of them at 5 years. The extended high frequency audiometry was measured from 10 to 18 kHz, with 1 kHz steps, and the results were related to the number of attacks of acute otitis media (AOM) (0, 1-2, 3-7 and > or = 8) they had experienced. The mean pure tone hearing thresholds varied from 10.7 dB at 10 kHz to 37.0 dB at 18 kHz in the right ears and between 11.6 dB at 10 kHz and 37.4 dB at 18 kHz in the left ears. Among those with > or = 8 attacks of AOM the the thresholds were highest, the difference between them and each of the first 3 groups being statistically significant at 13 and 14 kHz. From 11 to 16 kHz the same difference was significant between the last (> or = 8 AOM) and at least 2 of the first 3 AOM groups. Numerous attacks of AOM may have a harmful effect on high frequency hearing in the long term.

Acute Disease↗
PubMed1995

Hearing and acute otitis media in 13-year-old children.

Air and bone conduction thresholds of 330 unselected urban 13-year-old children with a known history of otitis were measured under ideal conditions, using standard clinical audiometry. In the subgroups of children with different numbers (0, 1-2, 3-7, > or = 8) of attacks of acute otitis media (AOM) in their history, the mean air conduction thresholds varied from 0.2 to 11.5 dB at different frequencies in different AOM subgroups. Air conduction pure tone averages (PTA, mean threshold at 0.5, 1 and 2 kHz) > 20 dB were not found in any of the ears. The mean bone conduction thresholds varied from -0.0 to 1.8 dB, depending on the subgroup and frequency (0.25 to 4.0 kHz) studied. Bone conduction PTAs > 10 dB were measured in 5 (0.8%) ears. Single bone conduction thresholds > 10 dB were found at different frequencies in 3 to 15 (0.5 to 2.3%) of the ears, and thresholds > 20 dB in only 2 ears (0.3%). The mean thresholds and number of ears with decreased hearing were distributed equally between different AOM subgroups, except that some air conduction high frequency losses were more frequent in children with > or = 8 attacks of AOM. We conclude that childhood AOM, even if it occurs frequently, seems not to have a significant harmful long-term effect on hearing.

Acute Disease↗
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↗