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Results for “Absorbable Implants”

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PubMed2002

In-vitro release of fluoropyrimidines from PLGA film implants.

The release of two low-molecular weight water-soluble fluoropyrimidines, 5-fluorouracil and 5-fluorouridine, from implants of PLGA films was modulated by varying the area (diameter) and number of layers of film per implant. The aim was to achieve continuous release without burst effect for at least a month. The film implants were prepared by the solvent evaporation technique. Except with 5-fluorouracil films, the in-vitro release profiles were in all cases triphasic, indicating that release proceeds by a combination of diffusion and polymer erosion. The experimental data fit the equation resulting from the sum of two exponentials, one direct and the other inverse. 5-fluorouridine release from simple films presented a relatively minor burst effect (24-28%). In contrast, the delivery of both compounds from sandwich-type implants occurred continuously without a burst effect, and lasted for 17-20 days. During the first phase, both 3- and 5-mm sandwiches released 55% of the dose of 5-fluorouridine, at rate constants of 0.037+/-0.021 h(-1) (n = 3) and 0.009+/-0.003 h(-1) (n=3), respectively. In the second phase, release was gradual from both simple films (k2 = 0.011-0.015 h(-1)) and sandwiches (k2 = 0.018-0.058 h(-1)). According to the analysis-of-variance results, neither the area nor type of implant influenced the rate constants significantly. The release profiles of 5-fluorouracil from simple films showed a severe burst effect (64-71%). Release of 5-fluorouracil was gradual only from sandwiches, 5 mm in diameter, showing a lag time unobserved in the 3-mm sandwiches. In the second phase, release was gradual (k2 = 0.014+/-0.003 h(-1)) from 3-mm implants. However, the high variability in results for 5-mm implants prevents conclusions being drawn about the model parameters. Therefore, the sandwich-type film implants showed their utility for releasing water-soluble drugs for a prolonged time, without burst effect.

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PubMed2001

[Lactic acid polymer implants in the repair of traumatic defects of the orbital floor].

BACKGROUND: The criteria determining the choice of the technique used to repair traumatic orbital floor defects include the quality of the expected result, morbidity, ease of use and plasticity of the method, and its cost and availability. Among the different methods proposed, lactic acid polymer implants are particularly interesting. MATERIAL AND METHODS: Eighteen patients with an isolated blow-out fracture of the orbital floor were treated with a lactic acid polymer implant between 1995 and 1996. Ten of these patients were reviewed at 24 to 43 months follow-up. RESULTS: The mean age of the patients was 35 years (20-52 years). No residual diplopia was observed. None of the patients had an anomalous orbital volume or ocular dystopia. None of the implants migrated. One patient experienced episodes of palpebral inflammation that resolved spontaneously. The ten patients reviewed were satisfied with the outcome. DISCUSSION: The properties of lactic acid polymer implants facilitate their use, avoid morbidity and provide a quality result. This is the procedure of choice for repairing tissue loss of the orbital floor. It has several advantages over alternative methods (the implants are rigid, thin, resorbable and well tolerated) without having their defects (thickness, fragility, roughness, predetermined form, rapid alteration, specific instrumentation, iatrogenic disorders). In addition, lactic acid polymer plates can be remodeled when heated, allowing a precise adaptation of the implant to the orbital structures. Finally, the cost, compared with the advantages, is not a barrier for routine use.

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PubMed2002

Composite resorbable polymer/hydroxylapatite composite screws for fixation of osteochondral osteotomies.

The aim of this study was to evaluate biomechanically the healing of an osteochondral fragment created in the distal sheep femur in response to fixation with a resorbable composite screw made of polylactide and hydroxylapatite. Pure poly(L-lactide) screws were used for comparison. At follow-up times of 4 or 8 weeks, specimens were examined with standard radiography, biomechanics, and histology. The intact contralateral femur served as a control. Only minimal signs of polymer degradation were seen in the histologic specimens. At 8 weeks, most osteotomies had healed completely and there was no difference in compressive strength and elastic modulus of cylindrical cores between the two types of biodegradable implants used. The width of the repair tissue at the tissue-implant interface was 250+/-50 micro m representing a clear transition zone of newly formed trabecular bone separating the implant from the surrounding plexiform bone. We conclude that relatively large polylactide implants, blended with hydroxyapatite, are capable of fixing an osteochondral fragment in an animal model. Biomechanical data assessing the quality of the bone formed at the osteotomy sites were found to be equivalent when compared to the control poly(L-lactide) implants of similar design and size. In addition, hydroxylapatite composite implants showed benign tissue responses and good implant osteointegration. Results suggest that hydroxylapatite composite screw implants can be used for similar indications as pure poly(L-lactide) implants in current clinical use.

Absorbable Implants↗

PubMedDate not supplied

Treatment of peri-implant defects with guided bone regeneration: a comparative clinical study with various membranes and bone grafts.

In this clinical study, a bioabsorbable membrane (Biofix) and two augmentation membranes made of expanded polytetrafluoroethylene (Gore-Tex) were tested for their osteopromotive potential. Forty-six implants were augmented with Gore-Tex membranes, 45 implants with titanium-reinforced Gore-Tex membranes, and 38 peri-implant defects with a resorbable polyglycolid membrane (Biofix). Autogenous bone (n = 85) and bovine bone matrix (Bio-Oss, n = 16) were used as filling materials beneath membranes. The results showed that bone repair is significantly improved by the use of membrane techniques. The average rate of bone regeneration with non-resorbable membranes was 84% (GTAM) and 81% (TR-GTAM). The use of Biofix membranes resulted in an average bone gain of 60%. The differences in efficacy established for the three types of membranes were found to be statistically significant (P < .001). Barrier membranes represent a valid technique for the treatment of peri-implant defects. Clinical and histologic results showed that Bio-Oss is an osteoconductive scaffold that promotes new bone formation.

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PubMed2001

Augmentation of a ruptured posterior cruciate ligament provides normal knee joint stability during ligament healing.

OBJECTIVE: To identify an augmentation technique which would provide mechanical protection for the healing posterior cruciate ligament. DESIGN: Six human knee specimens were tested in vitro for posterior knee joint stability after augmenting the cut posterior cruciate ligament by six different techniques using a resorbable double strand Polydioxanone augmentation device. BACKGROUND: A fresh isolated rupture of the posterior cruciate ligament is often treated conservatively. Results have shown that it can heal, but ligament elongations occur frequently. Therefore a method is needed to provide posterior knee joint stability during ligament healing. METHODS: The effect of different femoral augmentation insertions on posterior knee stability was tested by recording the antero-posterior (AP) position of the tibia and the augmentation force. Testing was performed during flexion--extension cycles and under posterior shear loads. RESULTS: The insertion combination that proved to stabilize the joints best consisted of one augmentation strand leading along the antero-lateral posterior cruciate ligament fibres and inserting at the distal end of the Blumensaat line and one strand leading along the posteriormedial fibres and inserting in the middle of the Blumensaat line. AP translations similar to those occurring in healthy knee joints could be achieved. CONCLUSIONS: It is possible to restore normal posterior knee joint stability by implanting a double strand augmentation device. This can help a posterior cruciate ligament to heal under non-elongated conditions.

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PubMed1998

Guided bone regeneration for immediate non-submerged implant placement using bioabsorbable materials in Beagle dogs.

The aim of the present study was to evaluate the combined application of different bioabsorbable materials for healing of residual peri-implant defects after placement of non-submerged implants into fresh extraction sockets. Second and third mandibular premolars were extracted from 10 Beagle dogs, the coronal part of the distal sockets were surgically enlarged and this was followed by immediate placement of specially designed hollow-screw non-submerged dental implants. For each animal, the coronal peri-implant defects were further treated with one of the 4 following procedures: 1) no treatment, control site; 2) grafting with porous hydroxyapatite (HA); 3) collagen membrane tightly secured around the implant and over the defect and 4) grafting with HA covered with a collagen membrane. After 16 weeks of healing, specimens were removed from the mandibule and prepared for a histomorphometric evaluation. The bone-to-implant contact length (BIC) was measured and compared amongst the different treatment modalities. In the defect area, the irregular bone regeneration was similar between all the treatment procedures (P > 0.10). In the sites covered with a collagen membrane alone, the total BIC (47%) was greater than in control sites (28.7%, P < 0.05) or sites grafted with HA (22.2%, P < 0.02). Total BIC in sites treated with the HA-membrane combination (43%) was only significantly different from sites treated with HA (P < 0.05). It is concluded that the use of bioabsorbable materials results in a limited increase of osseointegration when used in conjunction with immediate placement of non-submerged implants, although the principle of the one stage surgical approach can be maintained.

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PubMed1999

Factors influencing the success of GBR. Smoking, timing of implant placement, implant location, bone quality and provisional restoration.

The aim of this retrospective clinical study was to evaluate the influence of different factors on the outcome of GBR treatment. 75 patients, who were not randomly assigned to the investigated parameters for clinical reasons, were included in the study. They presented with defect sites around implants and were treated with a xenogenic grafting material and a resorbable collagen membrane. The defect morphology was described, its dimension was measured and calculated at the time of implant installation and at re-entry. The success of GBR treatment was related to several clinical variables and possible correlations were evaluated. Defect sites around maxillary implants showed significantly more bone fill (96%) compared to those in the mandible (78%). The insertion of a provisional restoration during the healing period was also associated with significantly better results than when no provisional was inserted. Immediate and short-term delayed implant placements showed the best results both with 92% bone fill, when compared with long-term delayed placements with 80% bone fill (n.s.). In sites with type I bone quality (compact bone), a reduced bone fill was observed (64%). The results indicate that successful bone fill can be achieved with GBR; this is more feasible in the maxilla, when a provisional restoration is used. Early implant placement timings seem to be preferable due to the alveolar ridge preservation, more favorable defect morphologies and a higher regenerative capacity.

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PubMed2006

Biodegradable elastomeric polyurethane membranes as chondrocyte carriers for cartilage repair.

Autologous chondrocyte implantation in combination with an autologous periosteal patch has become a clinically accepted procedure for the treatment of articular cartilage defects. The use of periosteum has, however, several drawbacks. We have been able to fabricate thin elastomeric biodegradable polyurethane (PU) membranes that may possibly have an application as a tissue-engineered substitute for the periosteal patch. Three types of membranes varying in pore size and surface texture were used as substrates for bovine chondrocytes in culture. The membranes, marked as P-I, P-II, and P-R, had average pore sizes of 10 to 20 microm, 40 to 60 microm, and less than 5 microm, respectively. A poly(L/DL-lactide) 80/ 20% micro-porous membrane (PLA) with an average pore size in the range of 10 to 70 microm was used as a control. There was no difference in the cell proliferation profile among the 4 membranes. In terms of proteoglycan and collagen production, P-I, P-R, and PLA performed similarly to one another. The rate of matrix production appears to be greater in the PU membranes than in the PLA membrane in the first 10 days, although by day 30, the PLA membrane had caught up. In all comparisons, the performance of P-II lagged behind those of the other materials. In conclusion, this preliminary study supports the potential use of this novel group of PUs as a periosteal flap substitute or perhaps as a chondrocyte carrier for matrix-assisted chondrocyte implantation and related techniques. Further studies will be necessary to better define their role in clinical applications for cartilage repair.

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PubMed2006

Cranioplasty after trephination using a novel biodegradable burr hole cover: technical case report.

OBJECTIVE AND IMPORTANCE: We have developed novel biodegradable polymer implants by using the rapid prototyping technology fused deposition modeling. Early results of a clinical pilot study for cranioplasty are presented. CLINICAL PRESENTATION: Five patients with the diagnosis of chronic subdural hematoma were included in the study. After trephination and evacuation of the subdural hematoma, burr holes (diameter, 14 mm) were closed using a biodegradable implant made of polycaprolactone. Implants were computer designed with an upper rim diameter of 16 mm and a 14 mm body diameter with a fully interconnected, honeycomb-like architecture of 400 to 600 microm in pore size. INTERVENTION: Postoperative computed tomographic scans indicated that the plugs were stably anchored in the osseous host environment with no fluid collection detectable. The postoperative course was uneventful, and patients were discharged after 5 days. Follow-up scans after 3, 6, and 12 months showed that the implants were well integrated in the surrounding calvarial bone with new bone filling the porous space. CONCLUSION: These novel polymer scaffolds made of the slow-degrading material polycaprolactone represent a suitable implant for closure of post-trephination defects.

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PubMed2000

Treatment of peri-implant defects with combination growth factor cement.

BACKGROUND: The use of growth factor agents in the regeneration of oral tissues is an area of current investigation. Combinations of growth factors have been used synergistically to improve tissue regeneration. The aim of this study was to determine the effects of a combination growth factor cement (GFC) on guided bone regeneration around dental implants. METHODS: A combination of bone morphogenetic protein-2 (BMP-2), transforming growth factor-beta (TGF-beta), platelet-derived growth factor (PDGF), and basic fibroblast growth factor (bFGF) was used in a bioabsorbable, non-hydroxyapatite, calcium phosphate cement. Five adult hound dogs were used to compare the effects of GFC, plain cement, and control (no cement). The right and left second, third, and fourth mandibular premolar teeth were extracted; the implant osteotomies were prepared; and a uniform circumferential gap was prepared 1.5 mm beyond the width of the implant in the coronal half of the osteotomy for cement placement. Titanium machine-polished dental implants were placed in the prepared sites, and coronal defects were treated according to previously randomized, assigned modality. A bioabsorbable collagen membrane was secured over the control site, and the flaps were closed primarily. The dogs were maintained on a soft diet to avoid soft tissue trauma. The dogs were sacrificed at 3 months. The specimens were sectioned, mounted, and stained with Stevenel's blue and van Gieson's picric fuchsin. The bone-to-implant contact and bone 1 mm peripheral to the implant surface were recorded with a computerized microscopic digitizer. RESULTS: The findings of this study indicate a significant effect of GFC on increased bone-to-implant contact and amount of bone per surface area compared with the other treatment modalities (P <0.0009). Plain cement demonstrated slight but nonsignificant increases compared with the control (P>0.05). CONCLUSIONS: GFC increases bone-to-implant contact and bone surface area within peri-implant defects. Further studies may be beneficial to determine the feasibility of its use for other regenerative applications.

Absorbable Implants↗

PubMed2000

Synthesis of CAD/CAM, robotics and biomaterial implant fabrication: single-step reconstruction in computer-aided frontotemporal bone resection.

The preoperative manufacturing of individual skull implants, developed by an interdisciplinary research group at Ruhr-University Bochum, is based on the use of titanium as the most common material for implants at present. Using the existing technology for materials that can be milled or moulded, customized implants may be manufactured as well. The goal of the study was to examine biodegradable materials and to evaluate the practicability of intraoperative instrument navigation and robotics. Data acquisition of an adult sheep's head was performed with helical computer tomography (CT). The data were transferred onto a computer aided design/computer aided manufacturing system (CAD/CAM system), and two complex defects in the frontotemporal skull were designed. Standard individual titanium implants were milled for both of the defects. Additionally, for one of the defects a resection template, as well as a mould for the biodegradable poly(D,L-lactide) (PDLLA) implant, were fabricated by the CAD/CAM system. A surgeon carried out the first bone resection (#1) for the prefabricated titanium implant using the resection template and an oscillating saw. The robot system Stäubli RX90CR, modified for clinical use, carried out the other resection (#2). Both titanium implants and the PDLLA implant were inserted in their respective defects to compare the precision of their fit. A critical comparison of both implant materials and both resection types shows that fabrication of a PDLLA implant and robot resection are already possible. At present, the titanium implant and resection using a template are more convincing due to the higher precision and practicability.

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PubMed2005

In vivo biostability of polyether polyurethanes with polyethylene oxide surface-modifying end groups; resistance to biologic oxidation and stress cracking.

Polyethylene oxide (PEO) on polymer surfaces has been reported to reduce cellular adhesion, a very desirable property for cardiac pacing leads. A Shore 80A polyether polyurethane with up to 6% PEO surface-modifying end groups (SME) was evaluated for its chronic in vivo biostability. In a short-term (12 week) screening test, strained samples appeared to develop the same surface oxidation as unmodified polymer, but did not produce visible cracking > or =500x, prompting a longer-term study. By the time the longer-term study was initiated, most of the PEO SME had disappeared from the starting material's surface. After 1 year in vivo, surface oxidation, shallow surface cracking, and environmental stress cracking (ESC) developed on highly strained samples to the point of failure, so that there was no significant difference between the SME polymer and its control (the same polymer without SME). No further change was seen for up to 2 years of implantation. Unstrained PEO SME polymer developed shallow surface cracking, but no ESC up to 2 years of implantation. Thus, PEO SME slightly delayed, but did not stop biodegradation, and under unstrained conditions, has no adverse effect on biostability.

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PubMed2005

Biocatalytic synthesis of highly ordered degradable dextran-based hydrogels.

We have prepared unique macroporous and ordered dextran-based hydrogels using a single-step biocatalytic transesterification reaction between dextran and divinyladipate in neat dimethylsulfoxide. These hydrogels show a unimodal distribution of interconnected pores with average diameters from 0.4 to 2.0 microm depending on the degree of substitution. In addition, the hydrogels show a higher elastic modulus for a given swelling ratio than chemically synthesized dextran-based hydrogels. In vivo studies in rats show that the hydrogel networks are degradable over a range of time scales from 5 to over 40 days, and possess good biocompatibility, as reflected in only a mild inflammatory reaction and minor fibrous capsule formation during the time-frame of subcutaneous implantation. These combined properties may offer competitive advantages in biomedical applications ranging from tissue engineering to controlled drug delivery.

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PubMed2006

Preparation of hybrid scaffold from fibrin and biodegradable polymer fiber.

A biodegradable hybrid scaffold was prepared from fibrin and poly(glycolic acid) (PGA) fiber. Mixed fibrinogen and thrombin solution homogeneously dispersed in the presence of various amounts (0, 1.5, 3.0, and 6.0mg) of PGA fiber was freeze-dried to obtain fibrin sponges with or without PGA fiber incorporation. By scanning electron microscopy observation, the fibrin sponges had an interconnected pore structure, irrespective of the amount of PGA fiber incorporated. PGA fiber incorporation enabled the fibrin sponges to significantly enhance their compression strength. In vitro cell culture studies revealed that the number of L929 fibroblasts initially attached was significantly larger for any fibrin sponge with PGA fiber incorporation than for the fibrin sponge without PGA fiber. The shrinkage of sponges after cell seeding was suppressed by fiber incorporation. It is possible that the shrinkage suppression of sponges maintains their intraspace, resulting in the superior cell attachment of a sponge with PGA fiber incorporation. After subcutaneous implantation into the backs of mice, the residual volume of a fibrin sponge with PGA fiber incorporation was significant compared with that of a fibrin sponge without PGA fiber. Larger number of cells infiltrated deep inside the fibrin sponges with PGA fiber incorporation implanted subcutaneously. It is concluded that the fibrin sponge reinforced by fiber incorporation is a promising three-dimensional scaffold of cells for tissue engineering.

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PubMed2006

Intrathecal implants of microencapsulated xenogenic chromaffin cells provide a long-term source of analgesic substances.

Adrenal medullary chromaffin cells secrete several neuroactive substances including catecholamines and opioid peptides that produce analgesic effects in the central nervous system. This study was designed to investigate whether intrathecal microencapsulated chromaffin cells could release analgesic materials producing antiallodynic effects on the chronic neuropathic pain in rats induced by chronic constriction injury (CCI) of the sciatic nerve. Prior to intrathecal implantation, chromaffin cells were encapsulated with alginate and poly-L-lysine to protect them from the host immune system. Behavior tests were performed before CCI, 1 week later, and at 4, 7, 14, 21, 28 days postimplantation. At the end of study, we performed cerebrospinal fluid (CSF) collection and implant retrieval. We observed that intrathecal implantation of encapsulated xenogenic chromaffin cells reduced the mechanical and cold allodynia in a model of neuropathic pain. CSF levels of catecholamines and metenkephalin in the rats that received implants were higher than the controls. In addition, we observed chronic survival of implants. These results suggested that intrathecal microencapsulated chromaffin cells may represent a new approach to chronic neuropathic pain management.

Absorbable Implants↗

PubMed2004

Self-reinforced bioresorbable poly-L/DL-lactide [SR-P(L/DL)LA] 70/30 miniplates and miniscrews are reliable for fixation of anterior mandibular fractures: a pilot study.

OBJECTIVE: Bioresorbable osteofixation devices are being increasingly used in orthognathic surgery and in cases of trauma to avoid problems associated with conventional metal osteofixation devices. The aim of this clinical study was to assess the reliability and efficacy of bioresorbable self-reinforced poly-L/DL-lactide (SR-P(L/DL)LA 70/30) plates and screws in the fixation of mandibular fractures in adults. STUDY DESIGN: Ten patients (20 to 49 years old) with isolated anterior mandibular parasymphyseal fractures were treated by means of open reduction and internal fixation using SR-P(L/DL)LA 70/30 bioresorbable plates and screws. RESULTS: During the minimum of 6 months of follow-up, no problems were encountered except for 1 case where a plate became exposed intraorally and infected. This required debridement and later excision of the exposed part of the plate. Despite this setback the fractured bone healed well. CONCLUSIONS: SR-P(L/DL)LA 70/30 plates and screws are reliable for internal fixation of anterior mandibular fractures in adults. Proper soft tissue coverage should be ensured to avoid plate exposure. Should implant exposure occur, it might be necessary to excise the exposed part after fracture healing (6-8 weeks postoperatively).

Absorbable Implants↗

PubMed2000

Chondral injury after meniscal repair with bioabsorbable arrows.

SUMMARY: Meniscal repair is a frequently performed procedure. Repair may be accomplished using several different techniques including inside-out, outside-in, and all-inside instrumentation. The Meniscus Arrow (Bionx, Blue Bell, PA) is an all-inside technique that has gained considerable popularity in the past 3 years. We report and illustrate a potential complication with this implant. Arrow fracture with condyle grooving should be considered in patients who have undergone repair with the Meniscus Arrow and complain of late postoperative symptoms.

Absorbable Implants↗

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.

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