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Exposure rates of wrapped and unwrapped orbital implants following enucleation.

PURPOSE: To compare the complication rate of porous polyethylene orbital motility implants with solid acrylic implants following enucleation and identify possible risk factors. METHODS: The authors retrospectively reviewed the charts of a total of 117 consecutive enucleations performed at the University of Illinois at Chicago between March 28, 1994, and May 28, 1999. Data obtained included patient demographics, surgical indication, implant type, attending surgeon, surgical technique, and any reported complications. The primary outcome was presence or absence of implant exposure at the final recorded visit. RESULTS: Of the 117 identified cases, 29 were eliminated due to insufficient follow-up data. Of the 88 remaining cases, 48 patients received porous implants and 40 received solid acrylic implants. Implant exposure developed in four cases. All exposures occurred in unwrapped porous polyethylene implants (n=2) or porous polyethylene implants wrapped in absorbable material (n=2). All exposures occurred in patients younger than 18 years of age, and 75% occurred early after trauma-associated enucleation surgery. CONCLUSIONS: The exposure rate of porous polyethylene implants in this study (9%) was found to be comparable to published rates for hydroxyapatite implants. There were no exposures of unwrapped solid acrylic spheres. Unwrapped porous implants in pediatric patients or following trauma-related enucleation may represent an increased risk for postoperative implant exposure. Absorbable wrapping of porous implants may carry the same risk for exposure as no wrapping. Porous implants wrapped in durable material appear to be as safe as solid acrylic spheres.

Adolescent↗

[In vivo study of degradation of poly-(D,L-) lactide and poly-(L-lactide-co-glycolide) osteosynthesis material].

AIMS: Comparison of the degradation of poly(D,L)lactide (Resorb X) or poly(lactide-co-glycolide) (LactoSorb) in vivo. MATERIAL AND METHODS: LactoSorb and Resorb X osteosynthesis plates were fixed at the lateral aspect of the femora of 26 Chinchilla rabbits using the respective osteosynthesis screws. After intraperitoneal injection of fluorochromes the screw plate bone blocks were resected after 1, 6, 12, 14, 16, 21, 26 months and radiologic, histologic as well as fluorescence microscopic examinations were carried out. RESULTS: Newly formed bone was detectable above and beneath the polymers 1 month after the implantation. The implants were totally covered by newly formed bone after 6 months. While the LactoSorb screws were found to be as birefringent as after 1 month, in the Resorb X screws a continuous resorption by phagocytizing marrow cells starting from the periphery was detectable. Resorb X was totally resorbed in histologic slides 12 months after implantation, while total resorption of LactoSorb lasted 14 months; both polymers were replaced by marrow cells. Bone remodeling was not finished 26 months after implantation in both polymers. CONCLUSION: Resorption of Resorb X was finished earlier than the resorption of LactoSorb. Both materials were found by fluorescence microscope to be completely resorbed after 12 or 14 months, but bone remodeling of the screw holes was not yet finished 26 months after implantation.

Absorbable Implants↗

Characterization of crosslinked high amylose starch matrix implants. 2. In vivo release of ciprofloxacin.

The purpose of this study was to develop a crosslinked high amylose starch (CLHAS) matrix implant as a sustained antimicrobial delivery system for local prevention and/or treatment of osteomyelitis. Implants (200 mg) of CLHAS containing 2.5% (5 mg), 7.5% (15 mg), 15.0% (30 mg) and 20.0% (40 mg) of ciprofloxacin (CFX), were prepared by direct compression of dry blends. Rabbits were administered six 2.5, two 7.5, one 15.0 or one 20.0%-CFX implants along the femur between the quadriceps and biceps femoris muscles to determine systemic (serum) versus local (muscle and bone) CFX concentrations over 1 month. Blood samples were taken throughout the study for CFX assay. Muscle and femur were collected at 3, 7, 14, 21 and 28 days after implantation for host response evaluation and CFX assay. Residual polymer was explanted to determine the remaining dose of CFX. All animals remained healthy during the study. Local tissue reaction was mild and limited to the implantation site. Serum CFX concentrations remained low regardless of implant loading. Increased drug loading resulted in a higher and longer release of CFX in muscle and in bone. Local CFX concentrations were detected largely in excess of the MIC over 28 days with 20.0%-CFX implants. More residual CFX in polymer was detected over a longer period of time at high loading. These results strongly support the development of CLHAS implants for local antibacterial therapy.

Absorbable Implants↗

Bioabsorbable suture anchor (co-polymer 85/15 D,L lactide/glycolide) implanted in bone: correlation of physical/mechanical properties, magnetic resonance imaging, and histological response.

A novel bioabsorbable suture anchor has been introduced for shoulder rotator cuff surgical repair made of the co-polymer 85/15 D,L lactide/glycolide. Previous clinical reports on the use of this material in anterior cruciate ligament reconstruction have described intraosseous edema at various time intervals following implantation. The purpose of this study was to analyze the implant's loss of physical properties and to correlate magnetic resonance imaging (MRI) finding with gross and histological observations at various time intervals after intraosseous implantation in the experimental animal. Six drill holes were made in the tibias of 11 dogs. The spherical implant was placed in 5 of the drill holes and the sixth was preserved as a sham control. The dogs were killed at 3, 4, 6, 9, 12, and 26 weeks for gross and microscopic inspection. Correlative MRIs were taken from the 4-, 12-, and 26-week specimens. Gross inspection showed that the overlying soft tissue healed to bone in 3 weeks. The implants were surrounded by new bone by 6 weeks. The implants maintained gross physical integrity for 6 to 12 weeks. Histologically, there was minimal inflammatory response to the degrading implant. The implant site had been completely replaced by bone at 12 weeks. Correlative MRI showed edema adjacent to the implant sites, but there was no correlative inflammation or cyst formation through the time necessary for complete absorption of the implant. Correlative MRI identified and differentiated the image of the intact and degrading implant.

Absorbable Implants↗

Tissue engineering research in oral implant surgery.

In this article, we introduce some of the more extensively evaluated technologies using concepts of tissue engineering. We report on hard tissue engineering and soft tissue engineering and their utility for dental implant therapy. For hard tissue engineering, we evaluated human recombinant bone morphogenetic protein-2 and marrow mesenchymal stem cells using a model of sinus augmentation procedure in rabbit. We also describe distraction osteogenesis as another category for hard tissue engineering. In addition, we evaluate soft tissue management using cultured epithelial grafting for soft tissue engineering. The results of our tissue regeneration materials and methods in this study are positive. When the tissue engineering materials are used in clinics in the future, implant surgery could be the leading field.

Absorbable Implants↗

Use of collagen membranes for guided bone regeneration: a review.

There has been an increase in the use of the resorbable membranes that do not require a second stage surgery for removal in guided bone regeneration. The purpose of this review is to discuss the immune response of the host to the collagen, the use of resorbable membranes derived from Type I collagen of bovine Achilles tendon around dental implants, and its potential significance in the future of dental implantology.

Absorbable Implants↗

Biocorrosion of magnesium alloys: a new principle in cardiovascular implant technology?

OBJECTIVES: To develop and test a new concept of the degradation kinetics of newly developed coronary stents consisting of magnesium alloys. METHODS: Design of a coronary stent prototype consisting of the non-commercial magnesium based alloy AE21 (containing 2% aluminium and 1% rare earths) with an expected 50% loss of mass within six months. Eleven domestic pigs underwent coronary implantation of 20 stents (overstretch injury). RESULTS: No stent caused major problems during implantation or showed signs of initial breakage in the histological evaluation. There were no thromboembolic events. Quantitative angiography at follow up showed a significant (p < 0.01) 40% loss of perfused lumen diameter between days 10 and 35, corresponding to neointima formation seen on histological analysis, and a 25% re-enlargement (p < 0.05) between days 35 and 56 caused by vascular remodelling (based on intravascular ultrasound) resulting from the loss of mechanical integrity of the stent. Inflammation (p < 0.001) and neointimal plaque area (p < 0.05) depended significantly on injury score. Planimetric degradation correlated with time (r = 0.67, p < 0.01). CONCLUSION: Vascular implants consisting of magnesium alloy degradable by biocorrosion seem to be a realistic alternative to permanent implants.

Absorbable Implants↗

Use of a bioabsorbable implant for the repair of severed digital flexor tendons in four horses.

A new bioabsorbable implant composed of poly-L-lactic acid was used to repair the severed digital flexor tendons of four horses. The limbs were immobilised with distal casts which were changed after six to eight weeks and removed after 12 to 16 weeks. The horses were followed clinically and ultrasonographically for from seven to 19 months after the surgery. The ultrasonographic examination after the cast had been removed showed that the implants had been well incorporated into scar tissue. Two of the horses were mildly lame at the trot seven months after the surgery, but had returned to work after 12 months. The other two horses are still lame. No complications were observed with the implant.

Absorbable Implants↗

Biocompatibility and long-term toxicity of InnoPol implant, a biodegradable polymer scaffold.

InnoPol, a poly((D,L)-lactic-co-glycolic acid) [PLGA] 65/35 scaffold manufactured by special gas foaming methods in Korea, was subjected to tests to evaluate the degradation and tissue compatibility characteristics and long-term systemic toxicity in mice and rats. C57BL/6 mice and SD rats were implanted subcutaneously with 3-mm- and 1-mm-thick InnoPol circular discs, 10 mm in diameter, respectively, and sacrificed 8, 12, and 24 weeks after implantation. No test material-related effects were observed in mortality, clinical signs, body weight gain, food and water consumption, ophthalmologic signs, urinalysis, hematology, serum biochemistry parameters and organ weights of all animals implanted with InnoPol. Also, there were no systemic symptoms including metabolic alterations and inflammatory reactions in either mice or rats. In addition, no gross pathological findings, except skin lesions around the implantation sites, were found in the major organs. Although mild inflammation at the site of InnoPol implantation was confirmed from hematoxylin and eosin or Masson's trichrome staining at 8-12 weeks, the reactions had disappeared at 24 weeks following complete degradation of the scaffold, leaving granulomatous tissues that were similar to surgical wounds in sham operation controls without implants. These results suggest that InnoPol possesses good mechanical properties and tissue compatibility and does not cause any systemic toxicity other than transient local inflammatory reactions at the implantation site, and that it might be useful in applications as a medical device for implantation.

Absorbable Implants↗

Alveolar ridge repair using resorbable membranes and autogenous bone particles with simultaneous placement of implants: an experimental pilot study in dogs.

The aim of this experimental study was to evaluate the use of autogenous bone harvested during preparation of implant sites in combination with resorbable membranes for vertical ridge augmentation under 2 different defect site conditions. Combined vertical/horizontal alveolar bone defects were created by experimentally induced periodontal infections around all premolar teeth in the mandibles of 3 dogs (group 1). In another 3 dogs, fresh surgical defects were created after extraction of all premolar teeth in the mandibles (group 2). In all dogs, 2 implants were placed on each side of the mandible into the defect areas. One implant on each side of the mandible received augmentation with autogenous bone particles, and both implants on one side of the mandible were covered with polylactic acid membranes. After 5 months, the material was evaluated histologically. There was a small but significant increase in bone regeneration in the defects augmented with bone particles with and without membrane coverage in group 1. In group 2, no significant difference was seen between the controls and the augmented sites. The major limiting effect for bone regeneration appeared to be insufficient stability of the bone material to withstand the overlying soft tissue pressure. It was concluded that the placement of autogenous bone particles, either with or without membrane coverage, had little effect on the regeneration of peri-implant bone defects.

Absorbable Implants↗

[The influence of biodegradable polymer on bone and soft tissue].

Clinical and research reports concerning orthopedic biodegradable implants were reviewed. The clinical results were analyzed in terms of complications and compatibility. The possible applications of the implants and further research fields were summarized.

Absorbable Implants↗

Computerized tomography evaluation of a resorbable implant after transforaminal lumbar interbody fusion.

OBJECT: Synthetic bioabsorbable implants have recently been introduced in spinal surgery; consequently, the indications, applications, and results are still evolving. The authors used absorbable interbody spacers (Medtronic Sofamor Danek, Memphis, TN) packed with recombinant bone morphogenetic protein (Infuse; Medtronic Sofamor Danek) for single- and multiple-level transforaminal lumbar interbody fusion (TLIF) procedures over a period of 18 months. This is a consecutive case series in which postoperative computerized tomography (CT) scanning was used to assess fusion status. METHODS: There were 22 patients (17 men, five women; 39 fusion levels) whose mean age was 41.6 years (range 23-70 years) and in whom the mean follow-up duration was 12.4 months (range 6-18 months). Bridging bone was noted as early as the 3-month postoperative CT scan when obtained; solid arthrodesis was routinely noted between 6 and 12 months in 38 (97.4%) of 39 fusion levels. In patients who underwent repeated CT scanning, the fusion mass appeared to increase with time, whereas the disc space height remained stable. Although the results are early (mean 12-month follow-up duration), there was only one noted asymptomatic delayed union/nonunion at L5-S1 in a two-level TLIF with associated screw breakage. There were no infections or complications related to the cages. CONCLUSIONS: The bioabsorbable cages appear to be a viable alternative to metal interbody spacers, and may be ideally suited to spinal interbody applications because of their progressive load-bearing properties.

Absorbable Implants↗

Vertical bone augmentation with granulated brushite cement set in glycolic acid.

Brushite cements are a biocompatible materials that are resorbed in vivo. A new cement composed of a mixture of monocalcium phosphate (MCP) and beta-tricalcium phosphate (beta-TCP) that sets using glycolic acid (GA) was synthesized and characterized. After setting, the cement composition, derived from X-ray diffraction, was 83 wt % brushite and 17 wt % beta-TCP with an average brushite crystal size of about 2.6 +/- 1.4 microm. The cement has a diametral tensile strength of 2.9 +/- 0.7 MPa. Granules prepared from the set-cement were used as grafting material in bone defects on rabbit calvaria for evaluating in vivo its bone regeneration capacity. Considerable cement resorption, improvement in the bone mineral density, and bone neoformation was observed after 4 weeks of the granules' implantation.

Absorbable Implants↗

In vitro properties of PLLA screws and novel bioabsorbable implant with elastic nucleus to replace intervertebral disc.

The suitability of two different implant types for the replacement of the intervertebral disc was studied in vitro. Self-reinforced poly-L-lactide (SR-PLLA) screws Ø 4.5 mm were studied 24 weeks in vitro and cylindrical implants with elastic nucleus made of poly(L/D)lactide 96/4, poly(L/DL)lactide 70/30, Bioactive Glass n:o 13-93 and Polyactive 1000PEOT70PBT30 were studied 15 weeks in vitro. The cylindrical implant mimics the size and shape of the intervertebral disc. During the in vitro, there were no changes in compression properties with either implant types. The screws had sufficient modulus for intervertebral ossification in the canine model and the cylindrical implant showed also sufficient mechanical properties. These results suggest that both implant types could be used in clinical testing.

Absorbable Implants↗

Pre-clinical in vivo evaluation of orthopaedic bioabsorbable devices.

The presence of bioabsorbable materials in orthopaedics has grown significantly over the past two decades with applications in fracture fixation, bone replacement, cartilage repair, meniscal repair, fixation of ligaments, and drug delivery. Numerous biocompatible, biodegradable polymers are now available for both experimental and clinical use. Not surprisingly, there have been a wealth of studies investigating the biomechanical properties, biocompatibility, degradation characteristics, osteoconductivity, potential toxicity, and histologic effects of various materials. Promising results have been reported in the areas of fracture fixation, ligament repair, and drug delivery. In this article we review the pre-clinical in vivo testing of bioabsorbable devices with particular emphasis on implants used for these applications.

Absorbable Implants↗

A preliminary report on the biocompatibility of photopolymerizable semi-interpenetrating anhydride networks.

A new family of poly(anhydrides) (PA) has been developed which can be cured photochemically to produce degradable networks. These degradable anhydride networks may be useful in orthopaedics as bone cements and as matrices for drug delivery. This system, which is a semi-interpenetrating network (semi-IPN), has been evaluated for biocompatibility in subcutaneous tissue in rats and appears to undergo degradation primarily by surface erosion. The inflammatory response to the semi-IPN implants was minimal at both short (3 and 6 weeks) and long (28 weeks) time points and the fibrotic response was largely absent throughout the duration of this study. Furthermore, the OrthoCure implant material integrated well with the surrounding tissue and was invaded with vascularized connective tissue. For reference, linear PA controls were tested and showed a foreign body response culminating in the formation of relatively avascular fibrous capsule several cell layers thick, which became thicker over time, a response similar to what is typically observed in FDA approved implantable polymeric device systems.

Absorbable Implants↗