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Biomedical subjects

P U Rokkanen

Publications and source records attributed to P U Rokkanen.

13 recordsLinked to original sources
PubMed2001

Long-term results of wrist arthrodeses fixed with self-reinforced polylevolactic acid implants in patients with rheumatoid arthritis.

OBJECTIVE: Implants made of self-reinforcing polylevolactic acid (SR-PLLA) have been successfully used in arthrodeses of patients with rheumatoid arthritis. No lone-term evaluation on bioabsorbable fixation in patients with rheumatoid arthritis has been published so far. METHODS: In this study 21 wrist fusions were performed on 18 patients with rheumatoid arthritis by using SR-PLLA rods as fixation devices. The follow-up time was 3-8 years (mean 5.4 years). RESULTS: The results showed one non-union but no infections or problems associated with the bioabsorbable implants used. CONCLUSION: According to this study, fixation of wrist arthrodesis in patients with rheumatoid arthritis can be performed by using SR-PLLA implants with favourable results. The benefit of this method is the avoidance of the removal operation of fixation devices.

Absorbable Implants↗
PubMed2000

Bioabsorbable fixation in orthopaedic surgery and traumatology.

Bioabsorbable internal fixation devices were introduced clinically in the treatment of fractures and osteotomies of the extremities at the Department of Orthopaedics and Traumatology, Helsinki University, in 1984. Since November 5, 1984, a total of 3200 patients were managed using bone or ligament fixation devices made of self-reinforced (matrix and fibres of the same polymer) bioabsorbable alpha-hydroxy polyesters. The devices used included cylindrical rods, screws, tacks, plugs, arrows, and wires. The most common indication for the use of bioabsorbable implants was the displaced malleolar fracture of the ankle. Transphyseal fixation with small-diameter, mainly polyglycolide pins was used in children. The postoperative clinical course was uneventful in more than 90% of the patients. The complications included bacterial wound infection in 4% and failure of fixation in 4%. In one-fifth of the latter cases, however, re-operation was not necessary. The occurrence of non-infectious foreign-body reactions two to three months postoperatively has been observed in 2% of the patients operated in the last few years with polyglycolide implants but none of the patients managed with polylactide implants. This inflammatory tissue response often required aspiration with a needle but did not influence the functional or radiologic result of the treatment. Owing to the biodegradability of these internal fixation devices, implant removal procedures were avoided. This results in financial benefits and psychological advantages. Bioabsorbable implants can also be used in open fractures and infection operations.

Absorbable Implants↗
PubMed1998

Consolidation of craniotomy lines after resorbable polylactide and titanium plating: a comparative experimental study in sheep.

The consolidation process of craniotomy lines in a skeletally immature large mammal was studied. A traditional narrow titanium miniplate was compared with a 0.5-mm-thick, 12-mm-wide absorbable punched self-reinforced poly-L-lactide (SR-PLLA) plate, both fixed with titanium miniscrews over bilateral parietal 2.5-mm-wide stable transosseous craniotomies on nine female sheep (16 to 20 months old). After 6, 12, 20, 52, and 104 weeks, cross-sectional histology, histomorphometry, and oxytetracycline chloride fluorescence studies were done to compare the healing process of the craniotomy lines and to study the biocompatibility and the degradation process of the SR-PLLA plate. The consolidation pattern supported the principle of guided tissue regeneration: under the wide, resorbable plate osseous bridging proceeded evenly throughout the line, whereas titanium plating led to bulky, uneven growth in the bone margins. All SR-PLLA-plated osteotomy lines had healed completely by 20 weeks, whereas none of the titanium-plated lines had consolidated during a follow-up of 1 year. The nonossified gaps were filled with dense connective tissue. Histomorphometric analysis showed that osseous bridging proceeded significantly faster on the resorbable plate side compared with the titanium side (p < 0.001). The osteoid surface fraction over the total trabecular surface was highest at 6 weeks, being 63 percent on the SR-PLLA side and only 36 percent on the titanium side. The oxytetracycline chloride fluorescence studies confirmed these findings. After 52 weeks, there was no osteoid or oxytetracycline chloride fluorescence left as a sign of terminated ossification, even in the nonconsolidated titanium sides. Microscopic cracking of the plate was evident at 12 to 20 weeks, and the first signs of active resorption were present at 52 weeks. After 2 years, the plate had disappeared and tiny polylactide particles were being actively reabsorbed. The biocompatibility of SR-PLLA and titanium was good, and no adverse cellular reactions to these materials were noted, except a clinical foreign body reaction caused by loosened titanium miniscrews. A densely punched, 0.5-mm-thick self-reinforced PLLA plate seems to retain its integrity for a sufficiently long time to complete osseous healing of a 2.5-mm-wide craniotomy line in the sheep calvarial area. A thin, wide fixation plate enables superior healing, especially in osseous defects. The degradation process of the SR-PLLA plate begins within 1 year and is far advanced after 2 years. By using absorbable SR-PLLA fixation plates instead of metallic plates, a subsequent operation for the removal of the implants can be avoided. SR-PLLA devices could thus be a potential additive or even alternative to metallic implants in craniofacial surgery.

Animals↗
PubMed1997

Comparison of the tissue response to absorbable self-reinforced polylactide screws and metallic screws in the fixation of cancellous bone osteotomies: an experimental study on the rabbit distal femur.

The availability of absorbable fracture-fixation devices for clinical use calls for better knowledge of the reaction of bone tissue to absorbable polyester implants as compared with similar metallic devices. To examine and compare the tissue response to biodegradable and metallic screws within cancellous bone, a transverse transcondylar osteotomy of the distal femur was fixed with absorbable self-reinforced polylevolactide screws in 35 rabbits and with stainless-steel screws in 35 rabbits. New bone formation and consolidation of the osteotomy were examined histologically, histomorphometrically, and microradiographically within standardized sample fields 1, 3, 6, 12, 24, 36, and 48 weeks postoperatively. The intact contralateral femur served as the control. A vigorous osteoconductive response to the polylevolactide screws was observed at 3 weeks postoperatively, and the osteoid surface fraction was significantly higher in all follow-ups than in the contralateral femora. In the femora with metallic screws, new bone formation was seen 3, 6, and 12 weeks postoperatively, but at 24, 36, and 48 weeks the osteoid surface fraction did not differ significantly from that of the intact control femora. The total bone area was significantly larger in the femora with self-reinforced polylevolactide screws than in the control bone 6-48 weeks postoperatively; in the femora with metallic screws, this was found only at 6 and 12 weeks. After 48 weeks, the femora fixed with metallic screws had statistically smaller total bone area than the intact control femora. Solid bone union was seen in 84% of the osteotomies in the self-reinforced polylevolactide group and in 76% of those in the metallic group after 3 weeks or more. No signs of degradation of the self-reinforced polyleuolactide implant and only a mild foreign-body reaction with no accumulations of inflammatory cells to either self-reinforced polylevolactide or metallic screws were observed during the follow-up period. Both types of screws seemed to induce an osteostimulatory response around their threads. This phenomenon was transient for metallic screws but lasted for at least 48 weeks for self-reinforced polylevolactide screws. The polylevolactide screw does not seem to cause osteopenia at the implantation site. The fixation properties of both self-reinforced polylevolactide screws and metallic screws appear to be sufficient for the fixation of small fragments of cancellous bone.

Animals↗
PubMed1995

Clinical biocompatibility and degradation of polylevolactide screws in the ankle.

The clinical biocompatibility and degradation behavior of absorbable fracture fixation devices are still incompletely known in humans. Fifty-one patients with displaced fracture of the ankle treated by open reduction and internal fixation with absorbable screws made of polylevolactide were seen in followup for at least 3 years. The mean duration of followup time was 52 months. The tissue tolerance and degradation of the devices were studied clinically and radiographically using computed tomographic scans. In addition, biopsy specimens for histologic examination were taken in 5 patients. The screws were clinically effective: An accurate position of the fragments was maintained until union in 50 patients. A mild transient subcutaneous late foreign body reaction occurred in 1 patient 22 months after fixation of the fracture. Despite radiographic evidence of an advancing degradation of the implants, biopsy specimens taken 45 months after the original operation still showed consistent areas of polylactide in the tissues. In 3 patients, a disturbing palpable subcutaneous screw head had to be removed. The incidence of foreign body reactions to polylevolactide screws in the ankle seems to be low, but the duration of the degradation process of the polymer in human tissues is considerably longer than has been anticipated.

Adult↗
PubMed1994

Glassy carbon implant as a bone graft substitute: an experimental study on rabbits.

The purpose of this experimental investigation was to study the incorporation of porous glassy carbon in bone. Cylinders of porous glassy carbon were implanted in drill holes in diaphyses and metaphyses of rabbits tibia for 1, 3, 6, 12 and 24 weeks. Bone ingrowth into the glassy carbon implants was examined by radiographic, histologic, fluorocrome and microradiographic methods. The material caused no pathological reaction. Tissue ingrowth into pores was seen by all examination methods. The amount of bone in the pores increases with time. The ingrowth was most distinctive in those areas where the implant was in close contact with cortical bone or trabeculae of the cancellous bone. Porous glassy carbon can be used as bone substitute, although the small size of implant available is at the present a limitation for its clinical use.

Animals↗
PubMed1993

Arthrodesis of the first metatarsophalangeal joint in rheumatoid arthritis. Biodegradable rods and Kirschner-wires in 39 cases.

The first metatarsophalangeal joint was arthrodesed in 39 patients with rheumatoid arthritis. Fixation material was either biodegradable self-reinforced poly-L-lactide rods or Kirschner-wires. There were 3 clinical nonunions in the biodegradable group, and none in the K-wire group, and radiographic nonunion in 5 and 2 cases, respectively. The fixator had to be removed in 3 cases in the K-wire group. The biodegradable rods did not seem to be any better than K-wires.

Adult↗
PubMed1991

Absorbable materials in orthopaedic surgery.

The most important surgical biodegradable polymers are aliphatic polyesters of -hydroxy acid derivates. Implants made of these polymers that are currently used include sutures and fiber constructions, porous composites and drug delivery system and partially or totally biodegradable devices. Development and experimental and clinical use of absorbable devices in the fixation of fractures or osteotomies are presented. The clinical experience is based on 1,300 operated patients. The results in the fixation of cancellous bone fractures or osteotomies with absorbable implants are comparable to those of metallic implants but there is no need for removal procedures as with metallic osteosyntheses. This substantially benefits the individual as well as save money.

Absorption↗
PubMed1990

Is the treatment of the most severe multiply injured patients worth the effort? A follow-up examination 5 to 20 years after severe multiple injury.

Ninety-two most severely injured patients--with injuries to at least four body regions with a mean ISS of 39--were examined at the outpatient clinic 5 to 20 years after the trauma. In addition, nine patients were interviewed by phone, thus 92.6% of the patients still alive were contacted. Of those who were not retired before the injury 59 of 82 (72%) had been able to return to work and most of them were still working at the time of the followup. The main reasons for inability to work were brain and spinal cord injuries, blindness, and 'failure in re-education.' Most complaints arose from sequelae of brain, pelvic, and upper and lower extremity injuries. Only seven patients needed constant medication because of their injuries. We conclude that the treatment of even the most severely injured patients with multiple injuries is certainly worth the effort.

Adolescent↗
PubMed1989

Characteristics of patients with multiple injuries treated in an intensive care unit with favorable results.

A series of 1,169 consecutive patients with multiple injuries was analyzed. A strict criterion for multiple injury was used, the average Injury Sum (sum of the severities of regional injuries) was 7.6, the average time of treatment in the intensive care unit was 11 days and the mean duration of hospital treatment was 51 days. Road traffic accidents were the most common cause of injury (75%) and the regions most commonly injured were the lower extremity (68%), brain (62%) and chest (58%). 46% required ventilation. Mortality was 11.3% during intensive care and the total hospital mortality was 13.1%. The factors most relevant to patients who were able to return home from the hospital were: no need for respirator treatment, no renal complications, no previous mental disturbance or alcoholism, young age, less severe brain or thoracolumbar spine injuries, few initial blood transfusions, few complications during treatment and prompt operative intervention if required.

Adult↗
PubMed1989

Blunt injury patients benefiting from intensive care.

The files of 2,002 trauma patients admitted to our intensive care unit between 1966 and 1984 were analyzed. 74% of the patients were admitted because of the trauma after primary care and 26% later. The main reasons for later admissions were respiratory distress in 11% and postoperative follow-up in 8% of the cases. The series consists of blunt injury patients with a mean age of 39 years for those who survived and 52 years for those who died. 65% of the patients were injured in road traffic accidents. Injuries to the lower extremity were the most frequent (60%) and injuries to the cervical spine the least frequent (11%). The injury Sum (= sum of injuries) ranged from 1 to 18 with an average of 5.6 in the whole series. Two thirds of the patients were multiply injured. A statistical analysis showed that the most important determinants between the dead and those who survived were resuscitation, need for respirator treatment, age of the patient, amount of primary blood transfusions, brain and renal complications. The ICU mortality was 9.0% and the total hospital mortality was 11.9%.

Adult↗
PubMed1983

Presentation and diagnosis of acute abdominal pain in Finland: a computer aided study.

326 patients presenting with acute abdominal pain to a hospital in Tampere were compared with others in England and Norway, and with a large series of 6097 cases collected under the auspices of the World Organization of Gastro-Enterology. The distribution of disease in these 326 Finnish patients bore remarkable similarities to the distribution in other countries. When subjected to a computer-aided diagnostic analysis, comparing Finnish patients with UK and world-wide data, as regards appendicitis, cholecystitis and nonspecific pain, the computer performed roughly as well as the clinicians diagnosing the same cases. It is concluded that these diseases therefore have a common presentation in Finland with that elsewhere. As regards small bowel obstruction however, the computer diagnosed only 22% of cases correctly, (compared with the accuracy of clinical diagnosis 73%). This leads us to conclude that this disease presents unusually in Scandinavia, and possible reasons are discussed.

Abdomen, Acute↗