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Results for “Absorbable Implants”

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At least 343 records · Page 19Linked to original sources

PubMed2004

New method of pediatric cranioplasty for skull defect utilizing polylactic acid absorbable plates and carbonated apatite bone cement.

Cranial defect repair in the pediatric population requires a variety of special considerations. The pediatric skull has a dynamic nature that prohibits the use of rigid fixation, which is commonly applied in the adult population. A technique using a combination of polylactic acid plates and carbonated apatite bone cement has been devised by our group. Skull defects of varying sizes were repaired in 34 pediatric patients. Patients were examined on postoperative day 3 and at 3 months via three-dimensional computed tomography scans. Patients have been followed up to 60 months after surgery without complications or failures to date. This method benefits the pediatric patients undergoing cranioplasty by minimizing the insertion of long-term foreign bodies and allows the possibility for transformation of this construct into viable tissue.

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PubMed2001

The fate of a tissue-engineered cardiac graft in the right ventricular outflow tract of the rat.

OBJECTIVE: The synthetic materials currently available for the repair of cardiac defects are nonviable, do not grow as the child develops, and do not contract synchronously with the heart. We developed a beating patch by seeding fetal cardiomyocytes in a biodegradable scaffold in vitro. The seeded patches survived in the right ventricular outflow tract of adult rats. METHODS: Cultured fetal or adult rat heart cells (1 x 10(6) cells) were seeded into a gelatin sponge (15 x 15 x 1 mm), and the cell number was expanded in culture for 1 or 3 weeks, respectively. The free wall of the right ventricular outflow tract in syngeneic adult rats was resected and repaired with either unseeded patches or patches seeded with either fetal or adult cardiomyocytes (n = 10 for each group). The patches were examined histologically over a 12-week period. RESULTS: A significant inflammatory reaction was noted in the patch at 4 weeks as the scaffold dissolved. At 12 weeks, the gelatin scaffold had completely dissolved. Both types of the seeded cells were detected in the patch with 5-bromo-2'-deoxyuridine staining, and they maintained their continuity. Unseeded patches had an ingrowth of fibrous tissue. The patches became thinner between the fourth and the twelfth weeks in unseeded (P =.003), fetal (P =.0001), and adult (P =.07) cardiomyocyte groups as the scaffold dissolved. The control patch, but not the cell-seeded patches, was thinner than the normal right ventricular outflow tract. The endocardial surface area of each patch was covered with endothelial cells identified by factor VIII staining. CONCLUSIONS: A gelatin patch was used to replace the right ventricular outflow tract in syngeneic rats. The seeded cells survived in the right ventricular outflow tract after the scaffold dissolved 12 weeks after implantation. In addition, the unseeded patches encouraged the ingrowth of fibrous tissue as the scaffold dissolved and the patches remained completely endothelialized.

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PubMed2002

[New biodegradable polylactide implants (Polypin-C) in therapy for radial head fractures].

Dislocated radial head fractures of the type Mason II are usually treated with screws and buttress plates. The implants are generally removed at a later date. Biodegradable implants can be applied successfully for the reduction of small radial head fractures subject to shearing forces and slight loads. The implants are completely absorbed once the fracture has healed, making a second operation for the removal of the implant unnecessary. The Polypin C-Pin is made of poly(L, DL-lactide) mixed with 10% beta-tricalcium phosphate to ensure controlled, slow degradation with no significant side effects. This new Polypin C fixation pin was clinically tested on 35 patients with radial head fractures (CCF 21B2.1 and 21B2.2) from 31.10.1996 until 1.4.2002. A total of 34 of the patients (97.1%) underwent a clinical and conventional radiological follow-up examination after an average of 38.2 months. In 29 cases a CT was also carried out. Between 18 and 24 months, two cases of grade 1 osteolysis were observed around the pin head. No trace of osteolysis was observed at the final examination in either case. According to the Broberg score, an average of 96 out of a possible 100 points were attained at the final examination (31 excellent, 2 good, 1 unsatisfactory). After a period of 24 months, the pins were no longer visible on a conventional x-ray. A CT evaluation showed a density similar to that of spongioid bone in the original pin cavities after 3 years. These excellent clinical results prove that the Polypin C is a good method to treat dislocated radial head fractures.

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PubMed2005

Fabrication, implantation, elution, and retrieval of a steroid-loaded polycaprolactone subretinal implant.

A subretinal drug delivery system was developed to overcome the limitations of current treatments for retinal disease. A rod-shaped implant was made by embedding the corticosteroid triamcinolone acetonide within a biodegradable polycaprolactone polymer matrix. The implant was fabricated by homogeneously mixing the polymer and drug in solvent. The mixture was then dried, melted, and extruded, and the prepared solid form was drawn into a filament. The rods were mechanically sectioned to a length of 2 mm with a diameter of up to 320 microm. The rods were successfully implanted into the subretinal space of six rabbits. No complications were observed during the 4-week follow-up period. Initial observations of the implantation and elution characteristics revealed that polycaprolactone is well tolerated by the retinal tissue and that the implant can elute steroid for a period of at least 4 weeks without eliciting inflammatory response or complications. In vitro drug elution rates of different polymer to drug ratios and geometries into a balanced salt solution/bovine serum albumin (1%) solution showed an early rapid-release phase and late first-order phase. Histology and device retrieval after implantation revealed minimal encapsulation and good preservation of cellular morphology during the follow-up period and a more fibrous polymer microstructure of the implant.

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PubMed2000

Biodegradable scleral implant for intravitreal controlled release of ganciclovir.

BACKGROUND: The aims of this study were to develop biodegradable scleral implants that could overcome previously reported disadvantages such as an adverse burst in the late phase of release and to investigate the release profile of modified scleral implants in vitro and in vivo. METHODS: The modified scleral implants (weight 8.5 mg, length 5 mm) were made of mixtures of poly(DL-lactide) (PLA) with different molecular weights and contained 25 weight % of ganciclovir (GCV). The release of GCV was evaluated in vitro by spectrophotometry. Intravitreal GCV concentrations in vivo were measured by high-performance liquid chromatography following plug implantation in pigmented rabbits. The biocompatibility of the device was determined by indirect ophthalmoscopy and light microscopy. RESULTS: The in vitro release studies showed stable, long-term sustained and slow release. The in vivo release studies showed that the implants had long-term release in the diffusional phase of the triphasic release pattern and only a minor adverse burst of GCV in the late phase. No significant retinal toxicity was observed by histologic examination. CONCLUSION: Our findings showed that this newly modified scleral implant may provide suitable intravitreal drug delivery for treatment of cytomegalovirus retinitis.

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PubMed2000

The evolution of clinical applications of biodegradable implants in arthroscopic surgery.

Arthroscopic surgery is the most recent orthopaedic discipline to embrace biodegradable implant technology. Osteochondral fractures have been shown to be amenable to arthroscopic fixation with biodegradable pins. The areas of most recent interest have been biodegradable interference screw fixation for ACL reconstruction in the knee, biodegradable suture anchors for rotator cuff repair and capsulolabral repair in the shoulder. Biodegradable implants have allowed a paradigm shift away from bionic (mechanical replacement) engineering and toward true biologic solutions to reconstructive problems in arthroscopic surgery.

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PubMed2001

Tissue response to polyglycolide and polylevolactide pins in osteotomized cancellous bone.

A transcondylar osteotomy of the distal femur was fixed with a self-reinforced polyglycolide pin in one hind leg and with a self-reinforced polylevolactide pin in the other hind leg of 49 rats. The intact femurs of eight rats that did not have surgical treatment were used as controls. The tissue reaction to the implant and the consolidation of the osteotomy were examined radiographically, histologically, histomorphometrically, microradiographically, and using oxytetracycline fluorescence studies. The followups were from 1 to 52 weeks. A vigorous osteostimulatory tissue response to self-reinforced polyglycolide pins and self-reinforced polylevolactide pins was observed 1 week after fixation. This reaction reached its highest value 24 weeks after self-reinforced polyglycolide pin fixation and 6 weeks after self-reinforced polylevolactide pin fixation. The highest values of the mean trabecular bone area fraction, 27.9% for self-reinforced polyglycolide pins and 28.1% for self-reinforced polylevolactide pins, were measured at 48 weeks. At 12 weeks there was a peak of phagocytizing macrophages in the specimens with self-reinforced polyglycolide pin fixation. During the followup, total phagocytosis of self-reinforced polyglycolide pins was seen, but only a few signs of degradation of self-reinforced polylevolactide pins were observed. Both polymeric implants seemed to possess osteostimulatory properties, and the biocompatibility and clinical relevance proved to be acceptable.

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PubMed2000

Guided bone regeneration around endosseous implants with anorganic bovine bone mineral. A randomized controlled trial comparing bioabsorbable versus non-resorbable barriers.

BACKGROUND: Guided bone regeneration (GBR) is a viable treatment for osseous defects surrounding dental implants. Controversy exists regarding the choice of barrier membrane used and the method of membrane fixation to achieve GBR. METHODS: This study compared the efficacy of a porcine-derived bioabsorbable collagen membrane and an expanded polytetrafluoroethylene (ePTFE) membrane (non-resorbable) for GBR using a bovine bone xenograft/autograft bone composite in defects surrounding dental implants. The study also examined the effect of primary barrier fixation on GBR. Defect size was recorded at Stage 1 and 2 surgeries (performed 6 months apart). Forty-eight subjects (41% males, 59% females) requiring GBR were treated with either collagen (23) or ePTFE (25) barriers, respectively. Implants were titanium self-tapping screw-type. In 34 GBR sites, barrier fixation was achieved with polylactic acid resorbable pins. The remaining barriers were secured with the implant cover screw and/or embedded beneath the flaps. RESULTS: At 6 months, a decrease in defect width (collagen barrier 1.95 +/- 0.60 mm, ePTFE barrier 2.65 +/- 0.56 mm), length (collagen barrier 2.65 +/- 0.61 mm, ePTFE barrier 2.26 +/- 0.66 mm), and circumference (degrees) (collagen barrier 57.7 +/- 18.7, ePTFE barrier 80.2 +/- 19.9) was observed for both membranes. A significant number (chi2, P = 0.041) of postoperative complications occurred when barrier fixation was lacking at initial surgery. Furthermore, a significant difference (P <0.05) in the success of GBR with respect to defect size was observed when barrier fixation was taken into account. CONCLUSIONS: In conclusion, both collagen and ePTFE barriers proved suitable for achieving GBR of osseous defects surrounding dental implants. The results of this study stress the importance of barrier fixation at the time of initial surgery.

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PubMed2004

Early findings in a pilot study of anterior cervical fusion in which bioabsorbable interbody spacers were used in the treatment of cervical degenerative disease.

OBJECT: In this pilot study the authors assessed the efficacy of bioabsorbable interbody spacers in the treatment of cervical degenerative disease. Metallic cages or interbody spacers have been widely used in the treatment of degenerative and traumatic cervical disease. Bioabsorbable technology has been used to develop a resorbable cage that can eliminate the complications and drawbacks seen with the use of traditional metallic implants. In general clinical practice bioabsorbable implants have shown the ability to degrade safely while demonstrating optimal imaging characteristics as a result of their radiolucency, and these devices eliminate stress shielding by their gradual dissolution. METHODS: This study is a retrospective evaluation of charts and x-ray films obtained in the first eight patients who underwent an anterior cervical decompression and fusion procedure with placement of a bioabsorbable interbody spacer and anterior cervical plate. All patients were treated in one surgeon's practice and had a minimum follow-up period of at least 6 months. At a follow-up interval of approximately 7 months, five patients exhibited an excellent result and three had a good result; no patient was noted to have a satisfactory or poor outcome according to the Odom criteria at their most recent follow-up visit. Seventeen (94%) of 18 grafted levels appeared to be solidly fused. One patient experienced a perisurgical complication consisting of a symptomatic hematoma, which was successfully drained. CONCLUSIONS: Bioabsorbable interbody spacers appear to be a safe and effective interbody implant in terms of clinical outcome and radiographically confirmed healing.

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PubMed2002

Applications of a resorbable interbody spacer in posterior lumbar interbody fusion.

Polyhydroxy acids are a promising class of resorbable materials with potential applications in spinal surgery. One such polymer, MacroPore (MacroPore Biosurgery, Inc.), offers a balance of strength, predictable degradation, lack of stimulus of foreign body reaction, and biocompatibility with neural tissue. MacroPore can be formed into an array of shapes and can be manufactured, sterilized, and stored using conventional techniques. Limited clinical experience has been gained with resorbable implants used as load-sharing devices in a posterior lumbar interbody fusion construct.

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PubMed2006

Mechanical evaluation of implanted calcium phosphate cement incorporated with PLGA microparticles.

In this study, the mechanical properties of an implanted calcium phosphate (CaP) cement incorporated with 20wt% poly (dl-lactic-co-glycolic acid) (PLGA) microparticles were investigated in a rat cranial defect. After 2, 4 and 8 weeks of implantation, implants were evaluated mechanically (push-out test) and morphologically (Scanning Electron Microscopy (SEM) and histology). The results of the push-out test showed that after 2 weeks the shear strength of the implants was 0.44+/-0.44MPa (average+/-sd), which increased to 1.34+/-1.05MPa at 4 weeks and finally resulted in 2.60+/-2.78MPa at 8 weeks. SEM examination showed a fracture plane at the bone-cement interface at 2 weeks, while the 4- and 8-week specimens created a fracture plane into the CaP/PLGA composites, indicating an increased strength of the bone-cement interface. Histological evaluation revealed that the two weeks implantation period resulted in minimal bone ingrowth, while at 4 weeks of implantation the peripheral PLGA microparticles were degraded and replaced by deposition of newly formed bone. Finally, after 8 weeks of implantation the degradation of the PLGA microparticles was almost completed, which was observed by the bone ingrowth throughout the CaP/PLGA composites. On basis of our results, we conclude that the shear strength of the bone-cement interface increased over time due to bone ingrowth into the CaP/PLGA composites. Although the bone-cement contact could be optimized with an injectable CaP cement to enhance bone ingrowth, still the mechanical properties of the composites after 8 weeks of implantation are insufficient for load-bearing purposes.

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PubMed2006

Is device closure for direct access valved stent implantation safe?

OBJECTIVE: Despite the progress made in the development of valved stents for trans-apical valve replacement, a reliable closure of the access orifice remains a major issue. The present study was designed to evaluate if device closure of the ventricular wall is safe. MATERIALS AND METHODS: Transventricular access for pulmonary valve replacement was simulated with a 26F sheath and the resulting orifice was closed with an Amplatzer Muscular VSD Occluder (AMuscVSDO) in chronic sheep experiments (body weight 45-48 kg). Mean procedure time, blood loss, and standard hemo-dynamics were recorded. The animals were sacrificed electively and the histopathological changes in and around AMuscVSDO in the right ventricular wall were systematically studied by semi-quantitative analysis of collagenisation, inflammatory response and 'resorptive' process. RESULTS: Mean procedure time was 31+/-10.7 min, blood loss was 22.5+/-8.7 ml, heart rate was 123+/-22.6 bits/min before and 128+/-28.7 bits/min after, mean arterial blood pressure was 88+/-16.7 mm Hg before and 82.6+/-18.3 mm Hg after the procedure. Mean survival was 5.3 weeks. The collagen and scar formation studies revealed three different periods: (1) initial fibrosis (0-3 weeks); (2) so-called 'capsulation' (3-9 weeks after the implantation of the Occluder); and (3) final remodelling and differentiation (9 weeks). The fabric inside the Occluder played the role of a collagenisation promoter, active from the 3rd week till it vanishes. Inflammation plays a role as a temporary reaction (0-3 weeks) during the healing process, with no signs of any active, focal or circumscribed, myocardial damage. CONCLUSIONS: (1) The closure of the free ventricular wall perforation with AMuscVSDO is safe due to the scar tissue resulting from the healing process around and in the device. (2) The myocardial healing around and inside an implanted AMuscVSDO represents two processes: extensive fibrosis ensues around metallic wires with the progression towards the inside of the myocardium, whereas inside AMuscVSDO the loose connective tissue fills the myocardial lesion. During cicatrisation, the fabric elements of AMuscVSDO act as the ground for collagen formation and fibroblast proliferation. (3) The cicatrisation processes after ventricular AMuscVSDO implantation show remodelling, with rearrangement of collagen fibres architecture and distribution.

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PubMedDate not supplied

Biodegradable implants versus standard metal fixation for displaced radial head fractures. A prospective, randomized, multicenter study.

This multicenter, prospective, randomized study compares the use of biodegradable polylactide pins with standard metal mini-fragment implants for the treatment of displaced radial head fractures. It compares complication rates and clinical outcomes of both treatment methods. At 2 years, 135 (82%) of 164 patients were available for evaluation. Equivalence of treatment method was defined as a difference of 10% or less in the number of complication-free patients. Functional status was assessed by using the Broberg and Morrey Elbow Score and compared by an unpaired t test. Good or excellent clinical results were achieved by 92% (56/61) of the control patients and 96% (71/74) of the polylactide patients. The incidence of complication-free patients was 3.7% less in the polylactide group than in the control group. The 1-sided 95% confidence interval for the treatment difference between the 2 groups was more than -6.1%. Biodegradable polylactide pins have at least comparable outcomes as standard metal implants for the internal fixation of reconstructable displaced radial head fractures.

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PubMed2003

Proton pump inhibitors control osteoclastic resorption of calcium phosphate implants and stimulate increased local reparative bone growth.

Calcium phosphate (CAP) rods and pastes based on dicalcium and tetracalcium phosphate chemistry were modified with a specific osteoclast proton pump inhibitor, Bafilomycin A(1), and implanted in the distal femurs of young male Wistar rats for 7, 10, and 14 days. The extent of osteoclastic resorption of these materials and the amount of regenerative bone formed were qualitatively evaluated. Resorptive activity similar to the remodeling process of natural bone was observed in the controls. In contrast, the resorption of materials containing Bafilomycin A(1) was considerably lower, even though tartrate-resistant acid phosphatase-positive osteoclasts were present at the tissue/material interface. A greater amount of newly formed bone consistently surrounded the CAP rods and pastes containing Bafilomycin A(1) in comparison to the control specimens, which indicated that this reparative bone was not resorbed as quickly as the new bone surrounding the controls. Increased local bone mass around the Bafilomycin A(1)-modified materials resulted from the diffusion of the proton pump inhibitor into the biological tissue at the defect site. Thus, through inhibition of the osteoclast proton pump, Bafilomycin A(1) slowed down not only the resorption of the implant material but also the resorption of the newly formed reparative bone, which resulted in an increased local bone mass.

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PubMed2005

Biodegradable implants for Pipkin fractures.

The current study was designed to clarify whether biodegradable poly-L/DL lactide pins provide an operative alternative for fixation of Pipkin fractures. Nine patients with Pipkin fractures (one with Pipkin Type I, one with Pipkin Type II, and seven with Pipkin Type IV fractures) were treated surgically between 1996 and 2002. In all patients, the femoral head fractures were fixed with biodegradable, 2.7-mm and 2.0-mm polylactide pins. Eight patients were followed up for an average of 54.2 months. One patient died before the final followup. Eight fractures healed uneventfully. In one patient, a persisting femoral head defect led to posttraumatic arthritis requiring insertion of a femoral endoprosthesis at 1 year. The average range of motion of the affected hips of all patients at followup was 109 degrees -0 degrees -0 degrees in flexion and extension. External and internal rotation averaged 37 degrees -0 degrees -29 degrees . One patient had Brooker Grade I heterotopic ossification develop, and another had a Grade II heterotopic develop. Merle d'Aubigne and Postel ratings showed two excellent and five satisfactory results (average score, 13.1). Adverse effects from the polylactide implants were not observed. Pipkin fractures can be fixed successfully with biodegradable polylactide pins.

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PubMed2004

Biological evaluation of hydroxyapatite/poly-L-lactide (HAp/PLLA) composite biomaterials with poly-L-lactide of different molecular weights intraperitoneally implanted into mice.

Histopathologic analysis of the tissue with HAp/PLLA implants was made and the leukocyte formula and chemiluminescence response of peritoneal phagocytes 2, 7 and 12 weeks after intraperitoneal implantation studied. Implants were made of HAp/PLLA biocomposites with PLLA molecular weights of 50000 (HAp/PLLA(50)) and 430000 g/mol (HAp/PLLA(430)) and of crushed devitalized femur bone of a young Wistar rat. Leukocyte formula and chemiluminescence of peritoneal phagocytes showed no systemic inflammatory response. The studied implants caused locally weak inflammatory reaction. The resorption of implants ranges in intensity (polymer resorption, i.e. disappearance rate), from the highest with the bone implants, low with HAp/PLLA(50), to the lowest with the HAp/PLLA(430) implants. Good resorption of the biocomposites and its mutual ingrowth with connective tissue prove their good biocompatibility.

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PubMed2005

[A novel orthopaedic biodegradable polymer and its biocompatibility].

Copolymer of polycaprolactone (PCL) and polylactic acid (PLA) was synthesized and catalyzed using Y (CF3COO)3/AL (I-Bu)3. The biocompatibility was evaluated by means of biochemistry, immunocytochemistry, and by cytotoxity test. This novel orthopedic biodegradable polymer can serve as an ideal orthopedic biodegradable implants, and adjustment of molecular weight and ratio of polymers can control its degradation period.

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PubMed1999

Comparison of polylactide screw and expansion bolt in bioabsorbable fixation with patellar tendon bone graft for anterior cruciate ligament rupture of the knee. A preliminary study.

In a preliminary study, 24 patients with rupture of the anterior cruciate ligament (ACL) were operated on using implants made of self-reinforced poly-l-lactide (SR-PLLA). The operation method was outside-in bone-tendon-bone reconstruction. In 10 patients the fixation was made with an SR-PLLA screw with a diameter of 6.3 mm, in 12 with an SR-PLLA expansion plug with a diameter of 6.0 mm, and in two cases both implants were used, but these cases were excluded from comparison. The purpose of the study was to evaluate and compare the use and fixation results of these two implants. The follow-up time averaged 3.2 years. Twenty patients attended follow-up. On subjective evaluations, seven of the eight patients following SR-PLLA screw fixation and six of the ten after expansion plug fixation regarded their knee as normal or nearly normal. Arthrometric testing showed the side-to-side difference to average 2. 9 mm following SR-PLLA screw fixation and 2.6 mm after expansion plug fixation (NS). Six of the patients had giving-way symptoms (two after screw fixation and four after plug fixation). The pivot shift test was slightly positive in two patients and positive in one patient after SR-PLLA screw fixation, and in three knees slightly positive and in another three knees positive following expansion plug fixation. Radiography showed variation in the location and orientation of the bone channels. Magnetic resonance imaging was performed in seven cases, and in two cases an edema was found in the tendon of the anterior cruciate ligament graft and in six cases the implants were visible. No statistical difference in results between the SR-PLLA screw and SR-PLLA expansion bolt was noted. Fixation with expansion plug seems technically more challenging, with a tendency to inferior results compared to screw fixation. In the absorbable fixation of a bone-tendon-bone graft there are no metallic artifacts on magnetic resonance imaging and no need to remove the fixation material regarding the revision surgery.

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