Biomedical subjects

P Rokkanen

Publications and source records attributed to P Rokkanen.

At least 19 recordsLinked to original sources

PubMed1992

[Absorbable rods and screws: a new method of fixation for fractures of the olecranon].

Between April 1986 and July 1990 fractures of the olecranon in 41 adult patients were treated by fixation with absorbable rods (20 patients) and screws (21 patients) of self-reinforced polyglycolide (SR-PGA), 3.2 mm in diameter and 20-70 mm in length. Patients were followed up for a mean time of 2 years 7 months (range 1 year to 4 years 6 months). After reduction of the fracture, channels were drilled from the proximal fragment through the cortex of the distal fragment and the fractures were fixed with absorbable rods or screws. By one year from follow-up maintenance of an anatomical reduction of the fracture was seen in 34 patients. Failure of fixation requiring a second operation occurred in 2 cases. In all cases functional recovery was at least satisfactory. Sinus formation as a sign of transient tissue reaction was observed in 3 cases, but did not influence the healing of the fractures or the functional recovery. The results in patients treated with rods or screws was similar. Absorbable screws combined with small rods and absorbable sutures allow treatment of +ore severe fractures of the olecranon than do rods alone.

Adult↗

PubMed1992

Intramedullary fixation of cortical bone osteotomies with self-reinforced polylactic rods in rabbits.

Osteotomies of the femoral shaft in rabbits were fixed with intramedullary rods made of poly-L-lactic acid (SR-PLLA) and poly-DL/L-lactic acid (SR-PDLLA/PLLA). Follow up was from one week to 2 years. In the PLLA group, in 37 out of 40 osteotomies the fixation was firm and the bone was united. In the PDLLA/PLLA group, the fixation was firm in 30 out of 45, but in 13 of these angular deformity of more than 10 degrees had occurred. The fixation had failed in 15. No inflammatory or foreign body reaction was seen in either group. This study demonstrates that SR-PLLA rods are suitable fixation for cortical osteotomies in rabbits.

Animals↗

PubMed1992

Self-reinforced absorbable screws in the fixation of displaced ankle fractures: a prospective clinical study of 152 patients.

The series consisted of 152 patients with ankle fractures treated between May 1987 and August 1989 using absorbable screws of self-reinforced polyglycolide 3.4 mm in inner diameter and 25-70 mm in length. The mean follow-up time was 2 years, 5 months (range, 1 year, 7 months-3 years, 10 months). After open reduction, a channel was drilled through the fracture surfaces and the fragments were fixed with one absorbable screw or screws. A plaster cast was used postoperatively. At 1-year follow-up observation, the radiographical result was anatomical in 93.3% of 104 patients with unimalleolar and bimalleolar ankle fractures (Weber A or B) and in 80.5% of 41 severe ankle fractures. Seven patients were unavailable for follow-up observation. Two reoperations were performed because of primary or secondary failure of fixation. In all unimalleolar and bimalleolar fractures and in 95.1% of severe ankle fractures the functional recovery score was at least satisfactory. Sinus formation as a sign of tissue reaction was observed in 10 patients 2-6 months postoperatively, but this did not influence the healing of the fracture or the functional recovery. This report is the first extensive publication on the clinical use of absorbable screws.

Activities of Daily Living↗

PubMed1992

The effect of an intramedullary biodegradable self-reinforced polyglycolic acid implant on tubular bone. An experimental study on growing dogs.

The purpose of this study was to examine the effects of intramedullary self-reinforced polyglycolic acid (SR-PGA) implant to the femoral bone growth in a growing dog by using radiographic, microradiographic, oxytetracycline-fluorescence, histological, polariscopical and histomorphometric studies. Intramedullary reaming and SR-PGA implant did not cause any longitudinal overgrowth phenomenon, but resulted in a slight increase in femoral neck-angle. The bone histology showed normal features and blood cell counts were within normal limits.

Animals↗

PubMed1992

The effect of an intramedullary self-reinforced poly-L-lactide (SR-PLLA) implant on growing bone with special reference to fixation properties. An experimental study on growing rabbits.

Polylactic acid (PLA) is a synthetic biodegradable material. The self-reinforced implants made of poly-L-lactic acid (SR-PLLA) were manufactured of biodegradable polymeric matrix reinforced with fibres of the same material. The purpose of this study was to find out the effect of an intramedullary SR-PLLA implant on growing bone and its applicability to the fixation of a femoral shaft osteotomy in a growing rabbit. In seven rabbits 6 weeks of age a SR-PLLA implant 2.0 mm in diameter and 50 mm in length was introduced into the intramedullary cavity of the right femur. A proximal femoral shaft osteotomy of the right femur was made in another ten 6-weeks-old rabbits. After accurate reduction, fixation of the osteotomy was achieved with an intramedullary 2.0 mm by 50 mm SR-PLLA-rod. The follow-up times were 6 and 28 weeks. An intramedullary SR-PLLA-rod neither caused any disturbance of the bone growth nor abnormalities of the peripheral blood cell counts. Solid union of the osteotomy was seen in six weeks after fixation with SR-PLLA implant.

Animals↗

PubMed1992

Absorbable pins of self-reinforced poly-L-lactic acid for fixation of fractures and osteotomies.

We reviewed 27 patients with small-fragment fractures or osteotomies treated by internal fixation with absorbable self-reinforced poly-L-lactide pins. The follow-up time ranged from eight to 37 months. The two most common indications were chevron osteotomy of the first metatarsal bone for hallux valgus and displaced fracture of the radial head. No redisplacements occurred, and there were no signs of inflammatory foreign-body reaction. Biopsy in two patients 20 and 37 months after implantation showed that no polymeric material remained.

Adult↗

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

Polylactide screws in the fixation of olecranon osteotomies. A mechanical study in sheep.

We studied absorbable self-reinforced poly-L-lactide screws in the fixation of osteotomies in sheep. A left olecranon osteotomy in 10 sheep was fixed with polylactide screws and in an additional 10 sheep with metallic AO cortical screws. Follow-up times were 6 and 12 weeks. 8 polylactide fixations healed and 2 failed. All metal fixations united; one of them had a fracture of the proximal fragment resulting in malposition. After killing the sheep the olecranons were radiographed and the shear strengths of the osteotomies were compared with those of the non-operated contralateral bones. After 6 weeks the mean comparative strength was 74 percent in the polylactide group and 83 percent in the metallic control group. After 12 weeks the corresponding values were 112 and 47 percent (P less than 0.05). Our study demonstrated that the mechanical weakening of fixed bone can be avoided by using absorbable polylactide screws instead of metallic screws. However, polylactide screws are not recommended for use without external support in places of high mechanical strain.

Animals↗

PubMed1992

Talocrural arthrodesis with absorbable screws, 12 cases followed for 1 year.

In 11 patients, 12 arthrodeses of the ankle joint were performed by using absorbable self-reinforced poly-l-lactide (SR-PLLA) or polyglycolide (SR-PGA) screws. 8 patients had posttraumatic arthrosis, 3 rheumatoid arthritis, and 1 rigid flexion contracture of the ankle due to neuropathy. The average follow-up time was 14 (7-22) months. Solid fusion was achieved in 11 of 12 cases in 9(6-16) weeks.

Absorption↗

PubMed1992

Foreign-body reactions to polyglycolide screws. Observations in 24/216 malleolar fracture cases.

Out of 216 patients with displaced malleolar fractures operated on using absorbable polyglycolide screws, 24 developed a transient local nonbacterial inflammatory reaction on an average 3 months after the operation. Upon histopathologic examination, these tissue responses were found to be nonspecific foreign-body reactions. Neither the age of the patient nor the number of screws used in the fixation affected the incidence of the reactions. The first-generation screws that were colored with an aromatic quinone dye showed a higher incidence, 19 reactions among 105 patients, than the new noncolored implants, 5 among 111 patients (P less than 0.01). No deleterious effect of these tissue responses on the union of the fractures could be detected, but the possible long-term consequences of this complication are so far unknown.

Adult↗

PubMed1992

[Resorbable rods and screws of polyglycolide in stabilizing malleolar fractures. A clinical study of 600 patients].

Absorbable internal fracture fixation implants have been in large-scale clinical use since 1984. The main advantage of these devices is that no subsequent operation for implant removal is required. In this study the results obtained in a series of 600 patients with displaced malleolar fractures who were operated on over a 6-year period (1985-1990) using rods or screws made of polyglycolide were analysed. Rod fixation was used in 63% and screw fixation in 37% of the patients. Recovery was uneventful in 91.5%. Bacterial wound infection occurred in 1.2% and failure of fixation necessitating reoperation in 0.8% (5 patients). In 4 of these 5 patients a refixation procedure with AO devices was performed. In one elderly patient with failed fixation talocrural arthrodesis had to be done. A sterile inflammatory foreign-body reaction complicated the course in 6.5%. The incidence of these reactions was higher during the early years of the study, when the implants contained an aromatic quinone dye, than later, when stain-free implants were used. The foreign-body reactions were transient and did not significantly influence the ultimate results of treatment. During the 6-year period the use of absorbable implants has made it possible for resources corresponding to several hundred hardware removal procedures to be used for other purposes.

Adolescent↗

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

Biodegradable fixation of distal humeral physeal fractures.

Polyglycolic acid (PGA) has been used worldwide as a biodegradable suture material since 1970. Biodegradable polyglycolide implants were introduced in osteofixation of cancellous bone fractures in 1985. From September 1987 to September 1989, 19 consecutive children with physeal fractures of the distal humerus necessitating open reduction and internal fixation were treated by transphyseal biodegradable fixation using 1.5 x 60-mm2 self-reinforced polyglycolide (SR-PGA) pins. Included were nine displaced fractures of the lateral humeral condyle, five severe avulsions of the medial epicondyle of the humerus, four displaced fractures of the humeral capitellum, and one intraarticular fracture of the medial condyle of the humerus. After accurate reduction, two smooth Kirschner pins 1.5 mm in diameter were introduced across the growth plate for temporary fixation. The metallic pins then were removed one by one and subsequently replaced with the cylindrical SR-PGA pins 1.5 mm in diameter. After operation, a padded plaster splint was worn for four weeks. Neither secondary displacement nor signs of growth disturbance were seen during the 26-month follow-up time (mean, 17.2 months). Not only the reduction of the costs but also the psychological aspects should be considered when dealing with biodegradable fixation of physeal fractures in children. Transphyseal biodegradable fixation has established itself as a procedure of choice for handling simple physeal fractures.

Adolescent↗

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↗

PubMed1992

Fixation of femoral shaft osteotomy with intramedullary metallic or absorbable rod: an experimental study on growing dogs.

The purpose of this study was to examine the effects of an intramedullary self-reinforced polyglycolic acid (SR-PGA), self-reinforced poly-L-lactic acid (SR-PLLA) and a metallic rod on growing bone and their applicability in the fixation of a femoral shaft osteotomy in growing dogs. In 5 dogs, 12 weeks of age, a SR-PGA rod and in another 5 dogs a SR-PLLA rod, both 4.7 mm in diameter and 60 mm in length, were introduced into the intramedullary cavity of the right femur to fix a femoral shaft osteotomy. In a third group of 5 dogs the femoral shaft osteotomy was fixed with an intramedullary metallic rod of equal size. The follow-up intervals were 1, 3, 6, 12, 24 and 48 weeks. Solid union of the osteotomy without secondary displacement was seen radiographically 6 weeks after the operation in all dogs. Neither an intramedullary SR-PGA-, SR-PLLA- nor metallic rod caused any significant disturbance to the longitudinal growth of the operated femur. Narrowing of the femoral neck and a slight valgization of the angle between the femoral neck and shaft without any functional disability was seen 48 weeks after the operation.

Absorption↗

PubMed1992

Platelet activation during acute phase after multiple trauma.

The acute phase after multiple trauma is associated with both thrombotic phenomena and a bleeding diathesis. To evaluate the activation of platelets, beta-thromboglobulin (BTG) in plasma and serum and thromboxane B2 (TxB2) in serum were measured in 14 patients with multiple trauma. BTG in plasma was significantly increased on days 1, 2 and 10 to 14 after the trauma. The highest median value 90 micrograms/l was measured on day 1. BTG in serum was significantly reduced 1 to 7 days after the trauma (median levels 4450-9100 micrograms/l). TxB2 was significantly reduced (median levels 18-97 ng/l) on days 1 to 14. The increased plasma levels of BTG is due to the posttraumatic activation of platelets in vivo. The reduced levels of serum BTG and TxB2 reflect the deficient functional capacity of circulating platelets to respond to extreme stress. Therefore, platelet count alone may correlate poorly with the haemostatic potential and may underestimate the need of platelet transfusions.

Acute-Phase Reaction↗

PubMed1992

Immunologic studies of nonunited fractures.

We studied tissue samples of noninfected delayed union or nonunion of diaphyseal bones in 10 patients immunopathologically and neuroimmunologically 4 to 25 months after the primary injury. Samples mostly consisted of vascularized connective tissue of varying density with the proline-4-hydroxylase-containing fibroblast as the major cell type. Most inflammatory cells were CD4 T-lymphocytes and their number was always twice that of the CD8 positive cells. Staining for CD11b positive monocyte/macrophages showed in all samples positive cells scattered in the connective tissue stroma with perivascular enrichments. Mast cells were absent or very rare. Our findings suggest that delayed union and nonunion tissue consists of vascularized connective tissue, which mostly contains 5B5 fibroblasts, CD11b macrophages and vascular endothelial cells with only few immigrant recently recruited monocytes or lymphoid cells. Almost all resident cells seem to be involved in tissue remodeling as suggested by their content of fibroblast-type MMP-1 and its proteolytic activator MMP-3 or stromelysin. The most striking finding was the paucity or total lack of peripheral innervation, which may have to do with the nonunion of the fracture.

Adolescent↗

PubMed1992

Holding power of metallic screws in cancellous bone and metallic plates in cortical bone. An experimental study on rabbits using polymethylmethacrylate and bone graft as supporting material.

The holding power of metallic screws in cancellous bone and metallic plates in cortical bone was tested in sixty rabbits (n = 60). These metallic devices were fixed either without support or with the support of plastic material or autogenous bone graft. The fixation firmness was studied radiographically and by a test of the bonding strength. After six weeks, the mean value of the holding power of screws in cancellous bone without support was 440 N, and that of screws supported by polymethylmethacrylate 674 N and by bone graft 540 N. Corresponding values after twelve weeks were 436 N, 664 N, and 616 N. Fixation with polymethylmethacrylate was better than either fixation without support (P < 0.001, t-test) or fixation with bone graft (P < 0.01), whereas fixation with bone graft was better than fixation without support (P < 0.07). The best fixation was achieved by polymethylmethacrylate according to group mean values. Our investigation of the holding power of plates in cortical bone did not reveal any statistically significant differences between the methods used.

Animals↗