Programmed water-induced shape-memory of bioabsorbable poly(D,L-lactide): activation and properties in physiological temperature.

This study reports of the novel water-induced shape-memory of bioabsorbable poly(D,L-lactide). We have developed an orientation-based programming process that generates an ability for poly(D,L-lactide) to transform its shape at 37°C in an aqueous environment without external energy and to adapt to a predefined stress level by stress generation or relaxation. In this orientation-programming process, polymer material is deformed and oriented at an elevated temperature and subsequently cooled down while retaining its deformed shape, tension, and polymer chain entanglements. At body temperature and in an aqueous environment, the shape-memory is activated by the plasticizing effect of water molecules diffused into the polymer matrix causing an entropy-driven directed relaxation of oriented and preloaded polymer chains. This plasticizing effect is clearly seen as a decrease of the onset glass transition temperature by 10-13°C. We found that γ-irradiation used for sterilizing the orientation-programmed materials strongly affected the shape-recovery rate, but not the recovery ratio. Both non-γ-irradiated and γ-irradiated sample materials showed excellent shape-recovery ratios during a ten-week test period: 94 and 97%, respectively. The orientation-programmed materials generated a predefined load in a 37°C aqueous environment when their shape-recovery was restricted, but when external tension was applied to them, they adapted to the predefined level by stress relaxation. Our results show that functionality in terms of shape-memory can be generated in bioabsorbable polymers without tailoring the polymer chain structure thus shortening the time from development of technology to its utilization in medical devices.

Manufacturing, mechanical characterization, and in vitro performance of bioactive glass 13-93 fibers.

Fibers were manufactured from the bioactive glass 13-93 by melt spinning. The fibers were further characterized by measuring their tensile and flexural strength, and their in vitro performance was characterized by immersing them in simulated body fluid, which analyzed changes in their mass, their flexural strength, and surface reactions. The strength of glass fibers is highly dependent on fiber diameter, test method, and possible surface flaws, for example, cracks due to abrasion. In this study, the thinnest fibers (diameter between 24 and 33 microm) possessed the highest average tensile strength of 861 MPa. The flexural strength was initially 1353.5 MPa and it remained at that level for 2 weeks. The Weibull modulus for both tensile and flexural strength values was initially about 2.1. The flexural strength started to decrease and was only approximately 20% of the initial strength after 5 weeks. During the weeks 5-40, only a slight decrease was detected. The flexural modulus decreased steadily from 68 to 40 GPa during this period. The weight of the samples initially decreased due to leaching of ions and further started to increase due to precipitation of calcium phosphate on the fiber surfaces. The mass change of the bioactive glass fibers was dependent on the surface area rather than initial weight of the sample. The compositional analysis of the fiber surface after 24 h and 5 weeks immersion did confirm the initial leaching of ions and later the precipitation of a calcium phosphate layer on the bioactive glass 13-93 fiber surface in vitro.

Characterization of human primary osteoblast response on bioactive glass (BaG 13-93)- coated poly-L,DL-lactide (SR-PLA70) surface in vitro.

Bioabsorbable polylactide-based polymers are commonly used for bone reconstruction. Although these polymers have proven successful in many applications, they do not have the capacity to induce osteoconduction. Therefore, several strategies have been developed to manufacture osteoconductive polylactide-based composites. In this study, we have investigated in vitro response of human primary osteoblasts for self-reinforced poly-L,DL-lactide 70/30 (SR-PLA70) plates coated with spheres of bioactive glass 13-93 (SR-PLA70 + BaG). Osteoblasts were cultured on SR-PLA70 and SR-PLA70 + BaG plates for 2, 7, or 14 days. By day 7, both materials induced a reduction in total cell population. However, by day 14 the proliferative response of osteoblasts on SR-PLA70 + BaG surface was such that the cell population had regained similar levels as that of day 2 controls. Alkaline phosphatase activity was higher on SR-PLA70 at day 7 but declined to control levels by day 14. There were no significant time-dependent variations in alkaline phosphatase activity on SR-PLA70 + BaG. After in vitro hydrolysis for 7 days, the elemental analysis of SR-PLA70 + BaG surface showed the presence of mineral precipitates that were confirmed as crystalline hydroxyapatite. This was accompanied by osteoblast spreading, protrusions of microvilli adhered to BaG 19-39 surface, cuboidal phenotype and cell surface associated formation of hydroxyapatite microspheres. In conclusion, the SR-PLA70 + BaG composite is capable of inducing a proliferative response of human primary osteoblasts, and appears to support the development of mature osteoblast phenotype. Therefore, the SR-PLA70 + BaG composites appear as promising osteoconductive scaffold candidates for reconstruction and regeneration of bone matrix.

Histomorphometric analysis of poly-L/D-lactide 96/4 sutures in the gastrocnemius tendon of rabbits.

BACKGROUND: Common Achilles tendon ruptures are not usually fixed by bioabsorbable sutures due to limitations in their strength retention properties. Modern technology has made it possible to develop bioabsorbable sutures with prolonged strength retention. AIMS: To evaluate histologically tissue reactions of poly-L/D-lactide (PLDLA) sutures implanted in Achilles tendon of rabbits. MATERIAL AND METHODS: Fifteen rabbits were evaluated at 2, 6 and 12 weeks postoperatively, with five rabbits in each follow-up group. PLDLA monofilament sutures were implanted into the medial gastrocnemius tendon. Polyglyconate monofilament sutures with similar diameter (Maxon 4-0, Cyanamid of Great Britain Ltd., Gosport, UK) were implanted in the contralateral gastrocnemius tendon. The histology was studied in hard-resin embedded samples. The thickness of the formed fibrous tissue capsule was determined histomorphometrically. RESULTS: PLDLA led to formation of significantly thinner fibrous tissue capsule than Maxon sutures of the same diameter. Median thickness (PLDLA vs. Maxon) at two weeks was 5.26 vs.13.22 microm, at six weeks 11.66 vs. 80.97 microm, and at 12 weeks 10.63 vs. 17.59 microm (p<0.01). CONCLUSIONS: During the 12 week follow-up period, PLDLA sutures implanted intratendineously formed thinner fibrous capsule than Maxon sutures of the same diameter. The suture materials were not totally absorbed by 12 weeks.

Efficacy of bioabsorbable antibiotic containing bone screw in the prevention of biomaterial-related infection due to Staphylococcus aureus.

Impregnation of antimicrobial agents within biodegradable orthopedic implants provides a possibility for local antimicrobial prophylaxis of biomaterial-related infections. The objective of this study was to evaluate the efficacy of a bioabsorbable ciprofloxacin containing bone screw (Ab-PLGA) in the prevention of biomaterial-related infection due to Staphylococcus aureus in a rabbit model. Animals in Group I (n=8) received a Ab-PLGA screw contaminated with S. aureus, while animals in Group II (n=8) received a stainless steel (SS) screw contaminated with S. aureus. In two negative control groups, the animals received a Ab-PLGA screw (Group III, n=4) or a SS screw (Group IV, n=4) without bacterial contamination. 18F-FDG-PET imaging, performed at 6 weeks, was applied as a novel quantitative in vivo imaging modality of implant-related infection. Infection was verified by swab cultures, direct cultures of the retrieved implant, and quantitative cultures of pulverized bone. The concentrations of ciprofloxacin in serum and local bone tissue were determined by a high performance liquid chromatographic (HPLC) method with fluorescence (FLD) detection. In the group of contaminated Ab-PLGA screws, all cultures were negative. In the group of contaminated SS screws, all cultures of retrieved implants and six cultures out of eight of pulverized bone were positive for inoculated S. aureus. In negative control groups, all cultures were negative except one contaminant (S. cohnii) found in a SS screw culture. Verified infection of contaminated SS screws was collaborated by the increased 18F-FDG-PET uptake (P=0.004 compared with the group of contaminated Ab-PLGA screws). The mean bone tissue concentration of ciprofloxacin varied from 2.54 to 0.83 microg/g bone as a function of distance from the implantation site. The serum concentration of ciprofloxacin remained undetectable and below the resolution of the analytic method (<5.0 ng/ml). This study confirmed the in vivo efficacy of bioabsorbable antibiotic containing bone screw in the prevention of biomaterial-related infection due to S. aureus.

Self-reinforced composites of bioabsorbable polymer and bioactive glass with different bioactive glass contents. Part I: Initial mechanical properties and bioactivity.

Spherical bioactive glass 13-93 particles, with a particle size distribution of 50-125 microm, were combined with bioabsorbable poly-L,DL-lactide 70/30 using twin-screw extrusion. The composite rods containing 0, 20, 30, 40 and 50 wt% of bioactive glass were further self-reinforced by drawing to a diameter of approximately 3 mm. The bioactive glass spheres were well dispersed and the open pores were formed on the composite surface during drawing. The initial mechanical properties were studied. The addition of bioactive glass reduced the bending strength, bending modulus, shear strength, compression strength and torsion strength of poly-L,DL-lactide. However, the strain at maximum bending load increased in self-reinforced composites. Initially brittle composites became ductile in self-reinforcing. The bioactivity was studied in phosphate buffered saline for up to 12 days. The formation of calcium phosphate precipitation was followed using scanning electron microscopy and energy dispersive X-ray analysis. Results showed that the bioactive glass addition affected the initial mechanical properties and bioactivity of the composites. It was concluded that the optimal bioactive glass content depends on the applications of the composites.

A novel bioabsorbable composite membrane of Polyactive 70/30 and bioactive glass number 13--93 in repair of experimental maxillary alveolar cleft defects.

A novel bioabsorbable composite membrane of polyethylene oxide terephthalate and polybutylene terephthalate copolymer (Polyactive 70/30) combined with bioactive glass No. 13--93 was tested in the repair of experimental maxillary alveolar cleft defects. In this pilot study, the possible ability of the membrane to promote bone formation by guided tissue regeneration was investigated. Standard alveolar defects were made bilaterally in the maxilla of 12 growing rabbits and were filled with autogenous bone grafts. The test defect was covered with the composite membrane and the other defect was left uncovered to serve as a control. The follow-up time was 10 weeks. Radiological, histological, and histomorphometric evaluations were performed. Radiologically, no statistically significant differences between test and control defects at 10 weeks were found. Histologically, the membrane enhanced osteogenic activity locally at the membrane-bone interface. Swelling of the membrane was observed. Histomorphometrically, no significant promotion of bone formation by the membrane was observed. The composite membrane was found to be biocompatible and surgically easy to use, but its osteopromotive effect was limited in this experimental cleft model. Further studies are necessary to assess its suitability for reconstructive surgical applications.

Bioabsorbable self-reinforced poly-L-lactide, metallic, and silicone stents in the management of experimental tracheal stenosis.

The aim of the present study was to compare, in rabbits, the biocompatibility and suitability of a bioabsorbable spiral stent made of self-reinforced poly-L-lactide (SR-PLLA) in the management of experimental tracheal stenosis with stents made of metal and silicone. Tracheobronchial stenosis, and its management, is still problematic because stenoses are not always amenable to surgical resection and reconstruction, especially concerning anastomotic problems and stenosis after lung transplantation. Stenosis can be handled with stenting, although the ideal stent has yet to be developed; all the stents available have their disadvantages. Because stenting of the airways can be only temporary, stents made of bioabsorbable materials, theoretically, offer benefits. Tracheal stenosis was created in rabbits by the extramucosal resection of cartilaginous arches of the cervical trachea. After a few weeks, the animals were operated on again, and those stenoses that had developed were dilated with a balloon. Stents then were implanted in the area of stenosis to keep the dilated trachea open. All the animals in the group with silicone stents had to be killed because of respiratory difficulties: their stents had a tendency to occlude because of internal encrustation, and they developed a hyperplastic polyp at the ends of the stents. The SR-PLLA and metallic stents were tolerated well, and after follow-up ended the animals were put to death. This experimental study showed that silicone stents had a tendency to occlude and that stents made of metal and of SR-PLLA were well tolerated and can be used in the management of airway stenosis.

The effects of fibre reinforcement and gold plating on the flexural and tensile strength of PGA/PLA copolymer materials in vitro.

Changes in the flexural and/or tensile strength of plates and rods made of PGA/PLA copolymer submerged in water for a period of 4 wk were investigated. During this time, the effects of PGA/PLA fibre self-reinforcement, carbon fibre reinforcement and gold plating on tensile and/or flexural strength were examined. The results were used for evaluation of the surgical applications of PGA/PLA copolymer and its composites. The initial tensile strength of non-reinforced material was 45 Mpa and its flexural strength was 150 MPa: the flexural strength of self-reinforced material was 265 MPa. The tensile strength of carbon fibre reinforced material was 90 MPa and its flexural strength 190 MPa. The initial strengths of plated and unplated samples were the same but plating delayed the loss of the mechanical strength of carbon fibre reinforced samples. After 4 wk the flexural strength of self-reinforced and carbon fibre reinforced samples was decreased to the level of cancellous bone (10-20 MPa) while the flexural strength of non-reinforced samples was below that level (less than or equal to 5 MPa). The results suggested that self-reinforced PGA/PLA composites may be used for the treatment of fractures in cancellous bone. Positive animal experiments led to clinical studies in vivo. These studies showed that there was no difference in outcome between 2 groups of patients with displaced fractures of the ankle treated with metallic implants or PGA/PLA fibre self-reinforced implants, respectively. Self-reinforced biodegradable implants are now used routinely in Helsinki University Central Hospital.

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.

In vitro degradation of Polyactive 1000PEOT70PBT30 devices.

Polyactive 1000PEOT70PBT30 (a segmented block copolymer of poly(ethylene oxide terephtalate)/poly(butylene terephtalate) with 70/30 PEOT/PBT ratio) was processed into three different types of samples: injection molded to rods, hot-pressed to films and to composite membranes made by hot-pressing a tubular mesh of poly-L,D-lactide 96/4 between two films of Polyactive. The molecular weight of Polyactive was not influenced by processing, but gamma-sterilization seemed to increase the weight average molecular weight (Mw). Mechanical properties of the rods and films decreased rapidly in hydrolytic conditions due to the hydrogel nature of the polymer, swelling and degradation. Mesh reinforcement increased the mechanical properties, but the components separated during soaking. In vitro the molecular weight of the rods and films started to decrease immediately, but the PEOT (or PEO) proportion remained relatively constant for 26 weeks. Macroscopically, all the wet devices remained intact, but fragmented on drying. Microscopically, topographical formations of polymer were found on the surfaces and small sodium-rich spots were precipitated onto and inside the polymer. Thermal measurements showed that polymer consisted of amorphous PEOT segments and both amorphous and crystalline PBT segments.

Strength and strength retention in vitro, of absorbable, self-reinforced polyglycolide (PGA) rods for fracture fixation.

The initial shear strength and changes in flexural strength of self-reinforced, absorbable polyglycolide (PGA) composite rods, submerged in distilled water (at 37 degrees C) for a period of 6 wk, were investigated. The recently developed self-reinforced absorbable material consists of an absorbable polymeric matrix reinforced with fibres of the same polymer. The initial shear strength of self-reinforced cylindrical PGA rods with a diameter of 3.2 mm was 250 MPa and the initial flexural strength of the rods was 370 MPa. During the first week of immersion the level of flexural strength decreased very little i.e. to 320 MPa. The loss of flexural strength increased after 1 wk immersion. However, after 3 wk it was 90 MPa. After 5 wk the flexural strength decreased to the level of strength of cancellous bone i.e. 10-20 MPa. The gamma-irradiation of the PGA rods (total dosage 2.5 Mrad) decreased the initial bending strength to 300 MPa but the hydrolytic behaviour of the rods was not changed. The in vitro strength and the strength retention of self-reinforced PGA rods are clearly better than the corresponding values for self-reinforced glycolide/lactide copolymer rods which we developed recently. Self-reinforced PGA rods are now used routinely in Helsinki University Central Hospital in the treatment of certain types of cancellous bone fracture.

Mechanical properties of biodegradable ligament augmentation device of poly(L-lactide) in vitro and in vivo.

To evaluate the mechanical properties of absorbable braided poly(L-lactide) (PLLA) fibre implants, 2.0 and 3.2 mm in diameter, maximum load defined as tensile load carrying capacity, elongation and axial rigidity were investigated after immersion in phosphate-buffered distilled water at 37 degrees C and pH 6.1 and after subcutaneous implantation in rabbit. The results confirm earlier indications that PLLA degrades faster in vivo than in vitro. The non-sterilized 2.0 mm implants lost 69% of initial tensile load carrying capacity in 46 wk in vitro. In vivo the loss of tensile load carrying capacity of the 2.0 and 3.2 mm implants was most marked between 6 to 12 wk. After 48 wk in vivo 2.0 and 3.2 mm implants retained 3 and 4% of initial tensile load carrying capacity respectively. Both in vitro and in vivo, elongation diminished in the same way as the maximum load. In vitro, mean axial rigidity of unsterilized 2.0 mm implants was 64 N during the first 34 wk but fell to 31 N at 46 wk. In vivo the initial mean axial rigidity of the 2.0 and 3.2 mm implants was 29 and 95 N respectively. At 24 wk the mean axial rigidity was 2 N in both implants.

Bioabsorbable scaffolds for guided bone regeneration and generation.

Several different bioabsorbable scaffolds designed and manufactured for guided bone regeneration and generation have been developed. In order to enhance the bioactivity and potential osteoconductivity of the scaffolds, different bioabsorbable polymers, composites of polymer and bioactive glass, and textured surface structures of the manufactured devices and composites were investigated in in vitro studies and experimental animal models. Solid, self-reinforced polyglycolide (SR-PGA) rods and self-reinforced poly L-lactide (SR-PLLA) rods were successfully used as scaffolds for bone formation in muscle by free tibial periosteal grafts in animal experiments. In an experimental maxillary cleft model, a bioabsorbable composite membrane of epsilon-caprolactone and L-lactic acid 50/50 copolymer (PCL/LLA) film and mesh and poly 96L,4D-lactide (PLA96) mesh were found to be suitable materials for guiding bone regeneration in the cleft defect area. The idea of solid layer and porous layer combined together was also transferred to stiff composite of poly 70L,30DL-lactide (PLA70) plate and PLA96 mesh which structure is introduced. The osteoconductivity of several different biodegradable composites of polymers and bioactive glass (BG) was shown by apatite formation in vitro. Three composites studied were self-reinforced composite of PLA70 and bioactive glass (SR-(PLA70 + BG)), SR-PLA70 plate coated with BG spheres, and Polyactive with BG.

Bone changes after experimental osteotomies fixed with absorbable self-reinforced poly-L-lactide screws or metallic screws studied by plain radiographs, quantitative computed tomography and magnetic resonance imaging.

The healing of the distal femoral osteotomy fixed with self-reinforced poly-L-lactide (SR-PLLA) or metallic screws in 16 rabbits was evaluated with plain radiographs, quantitative computed tomography and magnetic resonance imaging (MRI). At 36 weeks in the metallic fixation there was significantly more external callus than in the SR-PLLA fixation. On the metallic fixation side the cortical bone mineral density was significantly lower than on the non-operated side at 6 weeks as well as at 36 weeks. This decrease was not found in the SR-PLLA fixation. On the MRI on T1-weighted images a dark zone (signal void), and on the T2-weighted images a bright zone (increased signal intensity), was seen surrounding the screws, indicating oedema. At 36 weeks these oedematous zones were significantly smaller in the SR-PLLA fixation group than in the metallic one. The results give indirect evidence towards a more rapid and better osteotomy healing with the more physiologically elastic SR-PLLA screws than with the metallic screws. Fixation with SR-PLLA screws may prevent stress-protection atrophy and weakening of the fixed bone usually caused by the rigid metallic fixation.

Strength retention of self-reinforced polyglycolide membrane: an experimental study.

Self-reinforced polyglycolide (SR-PGA) devices are stronger than non-reinforced ones. To study the strength retention of SR-PGA membrane, in vitro and in vivo, membranes were either immersed in distilled water at 37 degrees C, or implanted in the subcutis or around the femoral bone of rats. The SR-PGA membranes lost their strength in vitro by 6 wk, while they retained it for 15 wk in vivo due to the fibrous tissue that formed around and inside the implant (biomembrane). This is an advantage when clinical application of the membrane is being considered.

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.

Effect of filler content on mechanical and dynamic mechanical properties of particulate biphasic calcium phosphate--polylactide composites.

A bioabsorbable self-reinforced polylactide/biphasic calcium phosphate (BCP) composite is being developed for fracture fixation plates. One manufacturing route is to produce preimpregnated sheets by pulling polylactide (PLA) fibres through a suspension of BCP filler in a PLA solution and compression moulding the prepreg to the desired shape. To aid understanding of the process, interactions between the matrix and filler were investigated. Composite films containing 0-0.25 volume fraction filler, produced by solvent casting, were analysed using SEM, tensile testing and dynamic mechanical analysis (DMA). Homogeneous films could be made, although some particle agglomeration was seen at higher filler volume fractions. As the filler content increased, the failure strain decreased due to a reduction in the amount of ductile polymer present and the ultimate tensile strength (UTS) decreased because of agglomeration and void formation at higher filler content. The matrix glass transition temperature increased due to polymer chain adsorption and immobilization onto the BCP particles. Complex damping mechanisms, such as particle-particle agglomeration, may exist at the higher BCP volume fractions.

Comparison of in vitro hydrolysis, subcutaneous and intramedullary implantation to evaluate the strength retention of absorbable osteosynthesis implants.

To evaluate the behaviour of mechanical properties of absorbable osteosynthesis implants in vivo, the strength retention of self-reinforced polyglycolide rods in distilled water at 37 degrees C in the subcutis and femoral medullary cavity of the rabbit was investigated. The self-reinforced polyglycolide rods lost their strength significantly faster in vivo than in vitro. The strength loss of the self-reinforced polyglycolide rods was only slightly faster in the medullary cavity than in the subcutis. As the removal of the implants from the medullary cavity became difficult 5-6 wk after implantation, it is suggested that subcutaneous implantation would be a suitable method to evaluate the strength retention of absorbable osteosynthesis implants.

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.