Biomedical subjects

T Pohjonen

Publications and source records attributed to T Pohjonen.

At least 19 recordsLinked to original sources

PubMed2006

Organisational injustice and impaired cardiovascular regulation among female employees.

OBJECTIVES: To examine the relation between perceived organisational justice and cardiovascular reactivity in women. METHODS: The participants were 57 women working in long term care homes. Heart rate variability and systolic arterial pressure variability were used as markers of autonomic function. Organisational justice was measured using the scale of Moorman. Data on other risk factors were also collected. RESULTS: Results from logistic regression models showed that the risk for increased low frequency band systolic arterial pressure variability was 3.8-5.8 times higher in employees with low justice than in employees with high justice. Low perceived justice was also related to an 80% excess risk of reduced high frequency heart rate variability compared to high perceived justice, but this association was not statistically significant. CONCLUSIONS: These findings are consistent with the hypothesis that cardiac dysregulation is one stress mechanism through which a low perceived justice of decision making procedures and interpersonal treatment increases the risk of health problems in personnel.

Adult↗

PubMed2004

Intramedullary fixation of femoral cortical osteotomies with interlocked biodegradable self-reinforced poly-96L/4D-lactide (SR-PLA96) nails.

Femoral diaphyseal osteotomies of adult sheep were fixed with intramedullary (i.m.) biodegradable self-reinforced poly-96L/4D-lactide (SR-PLA96) nails (Phi 10.66-10.78 mmx195-199 mm) that were interlocked with four Phi 1.5 mm metallic Kirschner (K) wires. Hollow i.m. nails used in the pilot study resulted in implant failure and only two of these sheep were followed long term (18 months and 3 years). In the main study, solid nails were used and this resulted in consolidation in 5/6 cases and in one non-union due to failure of both proximal K wires at 3 weeks. Sheep in the main study were followed for 6 and 12 months. Femurs were studied radiographically, microradiographically, histologically and by oxytetracycline labelling. Good bone healing was achieved and histology showed only a mild tissue reaction to the implant at 6-18 months. At 3 years, the implant had almost degraded and numerous foamy macrophages were ingesting the disintegrated material. No accumulations of lymphocytes implying an immunological inflammatory reaction were seen. This investigation demonstrated that absorbable SR-PLA96 i.m. nails can be used together with interlocking metallic K wires in fixation of simple cortical osteotomies in large animals weighing up to 63 kg. The long-term biocompatibility should be studied in a larger population.

Animals↗

PubMed2002

Treatment of pectus excavatum with bioabsorbable polylactide plates: Preliminary results.

BACKGROUND/PURPOSE: Pectus excavatum usually is corrected by thoracoplasty using metal plates. Recently bioabsorbabe polylactide plates have been developed. The aim of this study was to compare outcome after use of metal and bioasorbable plates in thoracoplasty performed for correction of pectus excavatum. METHODS: Eighty-three children (<16 years old) underwent thoracoplasty (Sulamaa's technique). In 75 patients, metallic plates, and in 8 patients, self-reinforced poly-L-lactide (SR-PLLA) plates, were used. Seven patients in the SR-PLLA group and 13 patients in the metal plate group were assessed 0.5 to 13 years postoperatively. RESULTS: The mean operating time was 121 minutes in the metal plate group, and 87 minutes in the SR-PLLA plate group. In the metal plate group, complications were pain caused by instability of the metal plates (n = 17), wound infection (n = 3), recurrence of deformity (n = 3), postoperative pain (n = 3), pneumothorax (n = 1), and nonspecific postoperative fever (n = 1). Thirteen patients underwent reoperation to refix the position of the metallic plates. In the SR-PLLA group, one case of pneumothorax occurred, and plate fragment palpability caused local pain in one patient. Cosmetic results and lung function values were similar. CONCLUSION: Our preliminary results show that bioabsorbable plates are a useful option in the treatment of pectus excavatum in children.

Absorbable Implants↗

PubMed2001

The fixation properties of carbon fiber-reinforced liquid crystalline polymer implant in bone: an experimental study in rabbits.

A novel composite material with ultra-high strength and a low elastic modulus called carbon fiber-reinforced liquid crystalline polymer (LCP/CF) has been developed. We studied the fixation properties of an intramedullary LCP/CF rod in rabbit bone. The medullary canals of both femora were reamed with a drill 3.2 mm in diameter starting from the trochanteric fossa in eleven New Zealand White rabbits weighing on average 4.8 kg. A smooth LCP/CF rod 3.2 mm in diameter and 50 mm in length was introduced into the medullary canal of both femora. The follow-up intervals were 0, 6, 12, and 52 weeks. The upper part of the harvested femora was cut into two pieces, each 25 mm in length. A mechanical push-out test was performed within 48 h to determine bone-implant interface attachment strength in the proximal (cancellous) and distal (cortical) locations. The mean push-out strength values at 0, 6, 12, and 52 weeks were 61, 250, 382, and 612 KPa in the cancellous location and 0, 32, 41, and 68 KPa in the cortical location, respectively. The strength of the bone/implant interface appeared to be quite low, similar to other uncoated or nonporous implants, but it was found to increase with time.

Animals↗

PubMed2001

Effects of worksite physical exercise intervention on physical fitness, perceived health status, and work ability among home care workers: five-year follow-up.

OBJECTIVE: The effects and constancy of a worksite physical exercise intervention were examined in relation to the physical fitness, perceived health status, and work ability of female service workers during periods of 1 and 5 years. METHODS: The subjects comprised female home care workers divided into an intervention group (n = 50, mean age 41.8 (SD 10.4) years) and a control group (n = 37, mean age 43.3 (SD 8.8) years). The intervention group participated in 9 months of supervised exercise intervention twice a week during the workday. Functional capacity, perceived health, and work ability were assessed at the beginning of the study and after a 1- and a 5-year period of follow-up. RESULTS: In the 1-year follow-up measurements, body fat had decreased (4%) and dynamic muscle performance and maximal oxygen consumption in relation to body mass (30-38 and 7%, respectively) had increased in the intervention group. The differences in outcome variables between the intervention and the control groups were significant (from P = 0.014 to P < 0.001). These positive effects of worksite exercise were observed despite the age of the subjects, and the changes were consistent during a 5-year period. In the control group the decline of the work ability index (L smean) was about three times faster than in the intervention group during the 5-year period. CONCLUSIONS: Physical exercise executed in work units can be used to improve the physical capacity of female home care aides and prevent the early decline of their work ability. In jobs that are physically demanding, such as home care work, early prevention must start before the age-related deterioration of health and physical capacity.

Adult↗

PubMed2001

Shear-load carrying capacity of cancellous bone after implantation of self-reinforced polyglycolic acid and poly-L-lactic acid pins: experimental study on rats.

Both distal femora of 40 rats were implanted with a self-reinforced polyglycolic acid (SR-PGA) pin in the right femur and with a self-reinforced poly-L-lactic acid (SR-PLLA) pin in the left femur. The intact femora of 20 rats served as controls. The follow-up times were 1, 3, 6, 12, 24, 36, 48, and 52 weeks. After killing all operated and control femora were examined macroscopically and radiographically. The shear-load carrying capacities of all the femurs were investigated, and the SR-PGA and SR-PLLA fixed specimens were compared with each other and with the control specimens. The shear-load carrying capacities reached their highest values at 36 weeks in the SR-PGA and SR-PLLA fixed and control specimens. Thereafter they gradually decreased. At 52 weeks both the SR-PGA fixed specimens and the control specimens had statistically significantly (p < 0.001) higher values than the SR-PLLA fixed specimens, when the influence of the pins had ceased. Otherwise, the shear-load capacities showed higher values in the SR-PLLA fixed specimens, as the pins carried the load. During the whole follow-up period the mean shear-load carrying capacity of the SR-PGA fixed specimens was 171.2 N and that of the SR-PLLA fixed specimens 180.9 N, the corresponding value of the control specimens was 148.2 N.

Animals↗

PubMed2001

Use of self-reinforced polylactide osteosynthesis devices in craniofacial surgery: a long-term follow-up study.

Self-reinforced polylactic acid or polylactide (SR-PLA) is a biodegradable polymer, which is strong enough to fix weight-bearing cortical bone fractures and osteotomies. We report our experience and follow-up of the use of SR-PLA plates in 15 clinical cranioplasties. Two of the cases are described in greater detail. In one of them SR-PLA plates were used in addition to titanium plates, and in the other an SR-PLA plate fixed with mini-titanium screws was used as the only fixation material. In the other patients SR-PLA plates or wire were used in addition to titanium. So far no complications have been observed in these 15 patients. The only small superficial fistula was associated with a titanium plate and titanium screws. The longest follow-up has been over eight years. Recent results show metal-like deformation properties in addition to complete late resorption, making SR-PLA osteosynthesis devices promising for use in craniofacial surgery.

Absorbable Implants↗

PubMed2001

Perceived work ability of home care workers in relation to individual and work-related factors in different age groups.

This study analysed the relationship between age and items of the Work Ability Index (WAI) among 19- to 62-year-old female home care workers (n = 636). The first significant decrease in work ability occurred between the ages of 40 and 44 years, and a second, sharper decrease occurred after 55 years of age. The subjects' physical work ability deteriorated as early as 35 years of age. In addition, current work ability, number of diagnosed diseases and work impairment due to diseases proved to be the most age-sensitive measures of work ability. The subjects who perceived their health status as poor had the highest risk for poor work ability. Moreover, the age-adjusted odds ratio indicated that the WAI was strongly associated with age and musculoskeletal and psychosomatic symptoms. Ergonomics, possibilities to control one's own work, time pressure and management were the features of work that predicted work ability. The study demonstrated the need to promote the work ability of home care workers early in working life. Among both older and younger workers, preventive measures should focus on the above-mentioned factors.

Adult↗

PubMed2001

Age-related physical fitness and the predictive values of fitness tests for work ability in home care work.

Despite the widespread assessment of physical fitness in occupational medicine and health services, only a few validity studies have been made of the fitness tests used in relation to job demands. The purpose of this study was to assess the physical fitness of female home care workers (n = 132) in relation to age and to evaluate whether the fitness tests used predict work ability over a 5-year period of follow-up. Muscle endurance declined by 18% to 37%, and isometric muscle strength by 10% to 18%, from the youngest (21 to 35 years) to the oldest (45 to 59 years) age group. The proportion of those subjects who could be classified below the average age-related fitness categories according to the maximal oxygen consumption was highest (50%) for the 21-to-35 age group. The logistic regression model showed that obesity (odds ratio [OR] = 7.51) and poor results on the sit-up (OR, 8.9), balance (OR, 6.5), and weight-lifting (OR, 4.6) tests predicted the highest risk for reduced work ability, according to the work ability index used in the 5-year follow-up. Moreover, average results for the trunk side-bending test (OR, 4.6), poor results for the squatting test (OR, 3.8), poor knee extension strength (OR, 4.2), and the average maximal oxygen consumption (l.min-1) (OR, 3.1) indicated a high risk for reduction in work ability. The physical fitness tests were strongly associated with the physical demands of home care work and were relevant for the evaluation of work-related fitness among home care workers.

Adult↗

PubMed2001

Biodegradation and strength retention of poly-L-lactide screws in vivo. An experimental long-term study in sheep.

BACKGROUND AND AIMS: Poly-L-lactide implants have gained popularity in the fixation of fractures and osteotomies in the past decade. The aim of the present experimental long-term study was to examine the degradation and strength retention of self-reinforced poly-L-lactide (SR-PLLA) lag-screws and the bone tissue response. MATERIAL AND METHODS: A total of 27 young adult sheep were used. Self-reinforced poly-L-lactide (SR-PLLA) lag-screws of 6.3 mm were implanted in the left proximal femur of nine sheep. At two, three and five years three of the sheep were sacrificed and the degradation was studied radiologically, microradiographically and histologically. For the strength retention measurements five SR-PLLA lag-screws of 6.3 mm and five lag-screws of 4.5 mm were implanted in the subcutaneous tissue of the five sheep and lag-screws of 6.3 mm for the pull-out test in the left proximal femur of 20 sheep. At 0, 12, 18, 24, 32, and 36 weeks bending and shear strength, molecular weight and pull-out measurements were performed. RESULTS: At five years no SR-PLLA material could be seen. The implant area was surrounded by high density bone with bone ingrowth in the screw area. At 36 weeks the bending strength of the 6.3 mm screws had decreased from 257.9 MPa to 36.4 MPa and the shear strength from 131.8 MPa to 19.8 MPa. The pull-out strength of the lag-screws of 6.3 mm in diameter decreased from 1507 N to 331 N in 24 weeks. CONCLUSIONS: SR-PLLA lag-screws showed high initial values, a controlled strength retention and gradual degradation process making the use of them safe also in demanding fixations.

Absorbable Implants↗

PubMed2000

Treatment of subcapital femoral neck fractures with bioabsorbable or metallic screw fixation. A preliminary report.

BACKGROUND AND AIMS: Cancellous bone fractures and arthrodeses have been treated successfully with bioabsorbable polyglycolide and poly-L-lactide implants. In this study bioabsorbable poly-L-lactide lag screws and metallic screws were compared in the fixation of subcapital femoral neck fractures. PATIENTS AND METHODS: Forty patients with femoral neck fractures were treated by internal fixation using three bioabsorbable self-reinforced poly-L-lactide (SR-PLLA) lag screws of 6.3 mm in diameter and 38 patients using three metallic screws of 7 mm in diameter. In addition, one patient was operated on using two and one using four metallic screws. The patients did not differ in age, body weight or primary dislocation of the fracture. There were six males in the lactide group versus 14 in the metallic fixation group. There were two Garden Stage I, 27 Garden Stage II, nine Garden Stage III, and two Garden Stage IV fractures in both groups. RESULTS: In the Garden I and II fractures there were 5/29 redislocations after SR-PLLA fixation and 8/29 after metallic fixation. In the Garden III fractures there were 4/9 and in the Garden IV fractures 2/2 redislocations in both groups. The ability to walk and the range of movement were better after bioabsorbable fixation. CONCLUSION: Self-reinforced poly-L-lactide lag screws can be used safely to fix subcapital femoral neck fractures in Garden Stage I and II fractures and in younger patients in Garden III fractures.

Absorbable Implants↗

PubMed1999

Application of a self-reinforced polyglycolic acid (SR-PGA) membrane to the closure of an abdominal fascial defect in rats.

The suitability of a polyglycolic acid (PGA) membrane to fascial closure was tested in 40 rats. To induce collagen synthesis, a fascial strip from the vastus lateralis muscle was applied to the peritoneal side of the PGA membrane. A midline laparotomy was performed, and the incision was covered with the membrane fixed at the edges. The animals were sacrificed at 3, 6, 12, and 28 weeks, at which time macroscopical, histological, and electron microscopical findings, as well as the results of breaking force tests were evaluated. Fascial augmentation had no effect on the results. Ventral hernias were observed in 37.5% of the cases, half of which were observed after 6 weeks postoperatively. In one case, intestinal adhesions to the membrane were found. Inflammatory reaction during the follow-up was moderate and lasted up to 12 weeks. Breaking force decreased up to 6 weeks, after which it slightly increased without reaching the breaking force level of the control animals.

Abdominal Injuries↗

PubMed1999

Development of a bioabsorbable suture anchor.

In this article, the design and properties of a new bioabsorbable suture anchor (SmartAnchor(trade mark)) are described and its properties are compared with those of some commercial anchors. Two comparative experiments were carried out in order to measure (1) the breaking force of suture/anchor attachment for SmartAnchor, MitekGII, and for Ogden anchors; and (2) the fixation force of the following anchors and tacks: SmartAnchor, MitekGII, BankartTack, and Suretac. The average suture/anchor attachment breaking force of SmartAnchor (204, 9 N) was 32% higher in comparison to MitekGII (155, 6 N) and 84% higher in comparison to the Ogden anchor (111, 4). The mean fixation force of the SmartAnchor (195, 5 N) was 40% higher than that of MitekGII (139, 2 N), but the T-test showed no statistical differences between MitekGII and SmartAnchor (p = 0.05). Both tested tacks behaved very similarly in this test. The average fixation force (pull-out force) for both tacks was about 210 N. Therefore, it is evident that the bioabsorbable SmartAnchor has a high enough initial mechanical performance for clinical investigation.

Absorbable Implants↗

PubMed1999

Comparison of polylactide screw and expansion bolt in bioabsorbable fixation with patellar tendon bone graft for anterior cruciate ligament rupture of the knee. A preliminary study.

In a preliminary study, 24 patients with rupture of the anterior cruciate ligament (ACL) were operated on using implants made of self-reinforced poly-l-lactide (SR-PLLA). The operation method was outside-in bone-tendon-bone reconstruction. In 10 patients the fixation was made with an SR-PLLA screw with a diameter of 6.3 mm, in 12 with an SR-PLLA expansion plug with a diameter of 6.0 mm, and in two cases both implants were used, but these cases were excluded from comparison. The purpose of the study was to evaluate and compare the use and fixation results of these two implants. The follow-up time averaged 3.2 years. Twenty patients attended follow-up. On subjective evaluations, seven of the eight patients following SR-PLLA screw fixation and six of the ten after expansion plug fixation regarded their knee as normal or nearly normal. Arthrometric testing showed the side-to-side difference to average 2. 9 mm following SR-PLLA screw fixation and 2.6 mm after expansion plug fixation (NS). Six of the patients had giving-way symptoms (two after screw fixation and four after plug fixation). The pivot shift test was slightly positive in two patients and positive in one patient after SR-PLLA screw fixation, and in three knees slightly positive and in another three knees positive following expansion plug fixation. Radiography showed variation in the location and orientation of the bone channels. Magnetic resonance imaging was performed in seven cases, and in two cases an edema was found in the tendon of the anterior cruciate ligament graft and in six cases the implants were visible. No statistical difference in results between the SR-PLLA screw and SR-PLLA expansion bolt was noted. Fixation with expansion plug seems technically more challenging, with a tendency to inferior results compared to screw fixation. In the absorbable fixation of a bone-tendon-bone graft there are no metallic artifacts on magnetic resonance imaging and no need to remove the fixation material regarding the revision surgery.

Absorbable Implants↗

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↗

PubMed1999

Fixation of mandibular body osteotomies using biodegradable amorphous self-reinforced (70L:30DL) polylactide or metal lag screws: an experimental study in sheep.

Mandibular body osteotomies were fixed in nine sheep using new totally amorphous (70L:30DL), self-reinforced, polylactide (SR-PLA) lag screws and in nine sheep using standard stainless steel lag screws. No intermaxillary fixation was used. During follow-up, radiological, histological and microradiological studies were undertaken at 3, 6, 12 and 24 weeks. In both groups, all osteotomies consolidated at similar rates and no adverse reaction to the screws was seen. However, displacements of the fixed osteotomy fragments were common in both groups during the first 3 weeks. The biocompatibility of SR-PLA during the follow-up period was found to be good. Only initial signs of biodegradation were seen. The results of this study indicate that (70L:30DL) SR-PLA has potential for use as a fixation screw material in oral and maxillofacial surgery, and that further studies using this material are justified.

Absorbable Implants↗

PubMed1999

Material properties of absorbable self-reinforced fibrillated poly-96L/4 D-lactide (SR-PLA96) rods; a study in vitro and in vivo.

A study was carried out to investigate changes in mechanical properties and degradation of self-reinforced fibrillated poly-96L/4D-lactide (SR-PLA96) rods in vitro and in vivo. The viscosity-average molecular weight, Mv, of the intact sterile (gamma irradiated) rods was around 50,000 g mol(-1). The SR-PLA96 rods of diameter 1.1 mm by 30 mm and diameter 4.5 mm by 50 mm were immersed in phosphate-buffered saline or implanted in the dorsal subcutis of rabbits. Bending, shear and torsion strength and bending modulus, together with the changes of viscosity and crystallinity, were measured up to 24 wk. The strength values showed only a slight decrease during the follow-up period with the exception of torsion strength, that decreased to 52% of the initial value during 24 wk. There were no statistically significant differences in the strength retention between in vitro and in vivo groups. Crystallinity increased over time, being 46-49% at 24 wk. The Mv of the rods decreased over 50% by 24 wk. These promising results motivated us to continue the studies with the fixation of experimental cortical bone osteotomies with SR-PLA96 intramedullary rods.

Journal Article↗

PubMed1999

Evaluation of self-reinforced polyglycolide membrane implanted in the subcutis of rabbits.

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.

Absorbable Implants↗