Biomedical subjects
Publications and source records attributed to E Partio.
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.
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.
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.
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.
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.
We studied prospectively the demographic data, fracture types and modes of treatment in 390 patients with acute traumatic hip fractures in two health care regions in Finland, the Middle Finland region and the Kymenlaakso region in 1989. In Middle Finland population (251,203 inhabitants) 199 patients with a hip fracture were admitted to two acute care hospitals, while 191 patients were admitted in Kymenlaakso (population 189,726) to four acute hospitals. There were no significant differences in the sex- and age-specific incidences between the two regions. In Middle Finland, 70% of the fractures were of the femoral neck, 28% were trochanteric and 2% subtrochanteric. The corresponding figures in Kymenlaakso were 57%, 38% and 5% (P < 0.05). In Middle Finland, 73% of the femoral neck fractures were treated primarily with a hemiendoprosthesis, 2% with primary total hip replacement and 25% by osteosynthesis. The corresponding figures in Kymenlaakso were 81%, 7% and 12% (P < 0.001). The mean duration of hospital stay was 14 days in Middle Finland and 21 days in Kymenlaakso (P < 0.01).
Within a 6-year period (1984-1989) absorbable pins, rods, and screws made of polyglycolide, polylactide, or lactide-glycolide copolymer were used in the internal fixation of 881 fractures, 73.1% of which were displaced malleolar fractures of the ankle. During the last 3 years the patients treated using absorbable fracture fixation constituted 19.6% of all fracture patients managed by internal fixation at the department. The number of hardware removal procedures avoided during the 6-year period as a result of the use of the absorbable implants was estimated at approximately 700. By determining all direct and indirect costs associated with internal fracture fixation and the influence of the percentage of hardware removal, a cost coefficient was calculated for certain fracture types when treated using absorbable versus metallic internal fixation. In bimalleolar fractures, an optimal indication for absorbable fixation, the coefficient was 1.04 (cost of absorbable fixation 4% higher than that of metallic fixation) if the removal percentage with metallic fixation was zero and 0.91 (cost of absorbable fixation 9% lower than that of metallic fixation) if the removal percentage was 100%. The breakeven point was a removal rate of 31%.
In 20 rabbits, a transverse distal femoral osteotomy was fixed using a 4.5 by 30-mm absorbable screw made of polyglycolide. No postoperative external support was used. The consolidation of the osteotomy was investigated histologically, morphometrically, and microradiographically in groups of 4 to 6 rabbits that were followed for 3, 6, 12, or 36 weeks. Fourteen osteotomies showed solid bony union; and in 3, several bone trabeculae were seen to bridge a still partially ununited osteotomy. In another 3 rabbits, each with a follow-up time of 12 or 36 weeks, no convincing signs of progressing consolidation could be seen. Only 1 of these rabbits showed displacement of the distal fragment.
During the period 1972-1974 10 patients suffering from pyogenic spondylitis have been treated at the Central Hospital of Middle Finland. Three of the patients had become acutely ill with septic fever and back pain. In the remaining cases the onset of the disease was insidious. Fever, weight loss and fatigue were the general symptoms. Percussion revealed local tenderness at the site of infection in all patients. Two patients showed neurological signs. The ESR was elevated in all cases and alkaline phosphatase was elevated in six patients. Blood culture was positive in those three patients who had become acutely ill. Narrowing of the intervertebral space was observed in all patients. Scanning with Tc99 was performed in nine patients, seven of whom were at an early stage of the disease; a significant uptake was recorded in five of these cases. The average interval between the onset of symptoms and the diagnosis was 3 months, range 1 to 5 months. The treatment consisted of bed rest and antibiotics. All the patients recovered and became symptom-free.
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