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Results for “Absorbable Implants”

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PubMed2005

Resorbable polylactic acid interbody spacers with vertebral autograft for anterior cervical discectomy and fusion.

OBJECTIVE: Resorbable polylactic acid spinal implants have recently become commercially available. These spacers carry the advantages of allowing for clear visualization of new bone growth, eliminating the risk of pathogen transmission, and providing for consistent biomechanical quality. However, previously published reports on the use of these spacers have all utilized bone morphogenetic proteins to supplement the fusion. This report describes our early experience with the use of these devices for interbody reconstruction in anterior cervical discectomy with fusion. METHODS: Twenty patients underwent an anterior cervical discectomy with fusion at 30 levels during an 18-month period. All patients were implanted with polylactic acid interbody spacers using the Smith-Robinson technique. Supplementary anterior cervical plating was applied using unicortical semiconstrained screws, and the spacers were filled with vertebral endplate autograft bone shavings. Seven of the patients were smokers, and three were diabetics. Radiographic fusion was determined with dynamic cervical spine x-rays, and clinical responses were determined using the Medical Outcomes Study Short-Form 36-Item Health Survey, Odom's criteria, Nurick scores, and functional outcome swallowing score dysphagia scores. Follow-up averaged 11.6 months. RESULTS: Of the 9 patients with myelopathy, all experienced clinical improvement, with the mean Nurick score improving from 2.7 to 1.3. Of the 14 patients who had radiculopathy, 9 had complete resolution of symptoms, 4 experienced some improvement, and 1 had no improvement. All 20 patients demonstrated radiographic fusion at last follow-up as demonstrated by bridging bone between the vertebral bodies and the absence of motion on dynamic x-rays. CONCLUSION: Resorbable polylactic acid interbody spacers are safe and effective for anterior cervical discectomy and fusion. Use of locally harvested vertebral endplate bone packed within the spacer is sufficient to promote fusion in anterior cervical discectomy with fusion.

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PubMed2005

Biomechanical comparison of bioabsorbable sutureless screw anchor versus suture anchor fixation for rotator cuff repair.

PURPOSE: Anchors that directly fix the rotator cuff to bone without using sutures may simplify the challenges associated with arthroscopic rotator cuff repair. This study compared a bioabsorbable screw fixation device to a standard suture anchor fixation method. TYPE OF STUDY: Randomized trial. METHODS: A poly-L-lactide acid (PLLA), bioabsorbable screw anchor was compared with a metallic suture anchor loaded with No. 2 braided polyester suture in 12-week-old fresh-frozen bovine shoulders. Twelve specimens were randomly assigned to the 2 repair groups (6 per group). A 1 x 2-cm defect was created at the insertion site of the infraspinatus tendon. Two anchors were implanted 1 cm apart in the anatomic insertional area of the infraspinatus tendon. After preconditioning to 10 N, each construct was cycled between 10 and 180 N for up to a maximum of 2,500 cycles at a rate of 33 mm/second using a materials testing machine. The number of cycles to 5- and 10-mm gap formation at the repair site and mode of failure were recorded. Clinically, 10-mm gap formation defines complete fixation failure. Data were evaluated using an analysis of variance with significance set at P < .05. RESULTS: Mattress suture fixation had significantly higher number of cycles to 10-mm failure compared with the PLLA device (P = .015). Failure occurred by tissue pullout in half the specimens and by device failure in the other half, without differences in failure modalities between groups. CONCLUSIONS: This anchor provides low-profile fixation of the rotator cuff and eliminates suture placement and knot tying during arthroscopic and mini-open cuff repair. However, these data suggest that this anchor may not perform adequately under cyclic loading conditions in patients during postoperative rehabilitation. CLINICAL RELEVANCE: This bioabsorbable anchor may not provide sufficient fixation for rotator cuff repair in humans.

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PubMed2002

Bone regeneration of localized chronic alveolar defects utilizing cell binding peptide associated with anorganic bovine-derived bone mineral: a clinical and histological study.

BACKGROUND: Osteoinduction to treat osseous defects has been attempted by several means. Some clinical studies have demonstrated that a synthetic cell binding peptide (P-15) with anorganic bovine derived bone matrix (ABM) has the ability to enhance bone regeneration. These studies suggest that more histological data are necessary to better understand this process. We have developed a Class III chronic alveolar defect animal model to investigate space-maintaining regenerative materials. The objective of this study was to clinically and histologically evaluate the use of P-15/ABM with or without a bioabsorbable membrane (M) to regenerate localized chronic alveolar ridge defects in dogs. METHODS: Six adult, male mongrel dogs were used in this study. Bilateral, Class III, alveolar defects were surgically produced following extraction of the mandibular second premolar teeth and local reduction of the alveolar ridge. After an 8-week healing interval, mucoperiosteal flaps were elevated. P-15/ABM with or without bioabsorbable membranes were implanted into contralateral defects in 10 sites. Two sites received no biomaterial (controls). Mucoperiosteal flaps were advanced over the P-15/ABM or P-15/ABM/M constructs and sutured. Pre- and postaugmentation clinical evaluation was done utilizing periodontal probes and calipers. The animals were sacrificed 12 weeks postaugmentation and block specimens processed for histologic evaluation. RESULTS: Clinical results showed no significant statistical augmentation on the control group (0.0 +/- 0.6 mm). In all experimental sites utilizing P-15/ABM or P-15/ABM/M, relevant ridge augmentation was observed (3.6 +/- 2.0 mm and 2.9 +/- 1.9 mm, respectively). Histologically, all experimental sites showed active bone formation with plump osteoblast and osteoid matrix deposition in the treated area. Bone ingrowth filled the area of the defects treated with P-15/ABM/M. Few P-15/ABM particles were seen in the cellular fibrous tissue surrounding the new formed bone trabeculae. CONCLUSIONS: P-15/ABM with or without membranes can produce a significant clinical ridge augmentation. Bone formation was histologically observed in all test areas. The association of a membrane with P-15/ABM seemed to enhance the process of bone formation.

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PubMed2002

Synthesis, characterization, and cytocompatibility of elastomeric, biodegradable poly(ester-urethane)ureas based on poly(caprolactone) and putrescine.

The engineering of tissue for mechanically demanding applications in the cardiovascular system is likely to require mechanical conditioning of cell-scaffold constructs prior to their implantation. Scaffold properties amenable to such an application include high elasticity and strength coupled with controllable biodegradative and cell-adhesive properties. To fulfill such design criteria, we have synthesized a family of poly(ester-urethane)ureas (PEUUs) from polycaprolactone and 1,4-diisocyanatobutane. Lysine ethyl ester (Lys) or putrescine was used as chain extenders. To encourage cell adhesion, PEUUs were surface modified with radio-frequency glow discharge followed by coupling of Arg-Gly-Asp-Ser (RGDS). The synthesized PEUUs were highly flexible, with breaking strains of 660-895% and tensile strengths from 9.2-29 MPa. Incubation in aqueous buffer for 8 weeks resulted in mass loss, from >50% (Lys chain extender) to 10% (putrescine chain extender). Human endothelial cells cultured for 4 days with medium containing the degradation products from PEUUs with either the Lys or putrescine chain extender showed no toxic effects. Cell adhesion was 85% of that measured on tissue-culture polystyrene for unmodified PEUU surfaces (p < 0.01) and >160% (p < 0.001) of polystyrene on RGDS-modified PEUUs. These biodegradable PEUUs demonstrate potential for future application as cell scaffolds in cardiovascular tissue-engineering or other soft-tissue applications.

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PubMed2004

Decreased fibroblast cell density on chemically degraded poly-lactic-co-glycolic acid, polyurethane, and polycaprolactone.

Select prolonged functions of fibroblasts leading to extensive fibrous tissue encapsulation can be detrimental to numerous implant applications, including materials designed for the bladder, vasculature, and bone. Specifically, overextended functions of fibroblasts at the tissue-implant interface for orthopedic applications lead to callus formation, fibrous encapsulation events, and ultimately soft (not desirable hard-bony) tissue juxtaposition. Such events result in insufficient regeneration of bone and compromise the overall success of the implant. The objective of the present in vitro study was to determine, for the first time, fibroblast densities on NaOH-treated poly-lactic-co-glycolic acid co-polymers (PLGA), HNO(3)-treated polyurethane (PU), and NaOH-treated polycaprolactone (PCL). Previous studies have demonstrated increased bladder, vascular, and bone cell densities on chemically treated compared to unaltered PLGA, PU, and PCL films. Results of this study provided evidence of decreased fibroblast numbers on chemically treated PLGA, PU, and PCL after time periods of up to 5 days. Examination of these substrates revealed that all chemically modified polymers possessed a high degree of nanometer surface roughness compared to their respective unaltered polymers. In contrast, other material properties (such as chemistry and wettability) were different when comparing chemically treated PLGA, PU, and PCL films. Since fibroblasts are anchorage-dependent cells whose adhesion is a critical prerequisite to the prolonged, extensive formation of a fibrous-tissue containing extracellular matrix, the present in vitro results of decreased fibroblast densities on chemically degraded PLGA, PU, and PCL suggest that these materials may be suitable materials for numerous tissue-engineering applications and, thus, deserve further investigation.

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PubMed2004

Non-conventional injection molding of poly(lactide) and poly(epsilon-caprolactone) intended for orthopedic applications.

Biodegradable polymers such as poly(lactide) (PLA) and poly(epsilon-caprolactone) (PCL) are increasingly used in biomedical applications as temporary implants. However, melt processing of these materials in particular of PLA is difficult due to the temperature sensitivity. Within this study, PLA and PCL were injection molded conventionally and by using the process shear controled orientation in injection molding (SCORIM) in order to investigate the effect of processing parameters on the physical properties of the moldings. Therefore, flexural testing, differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), molecular weight (MW) and orientation measurements were performed. PLA showed high sensitivity to melt temperature. In the case of amorphous poly(DL-lactide), the molecular weight and subsequently the ductility is substantially reduced by processing at higher melt temperatures. In the case of crystallizable poly(L-lactide), higher melt temperatures and shear induced by the SCORIM process resulted in enhanced crystallinity, which compromised the mechanical properties. Generally, SCORIM processing improved the mechanical properties, in particular the ductility, by orientating the molecular structure. PCL was shown to be less sensitive to shear and temperature than PLA. Stress at yield and stiffness are more improved by SCORIM processing. However, the processing temperature in combination with the grade used proved to be influential for the mechanical properties of resulting moldings.

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PubMed2005

[An experimental study on repairing bone defect with the biodegradable polycaprolactone material].

OBJECTIVE: To investigate the ability of the biodegradable polycaprolactone (PCL) material to repair bone defect and to evaluate the feasibility of using the PCL as the scaffold in tissue engineering bone. METHODS: The bone defect models of 4. 5 mm x 12 mm were made in the bilateral femoral condyle of 65 New Zealand white rabbits. The PCL cylinder was implanted into the right side of defect (experimental group, n = 60), the high dense hydroxyapatite was implanted into the left side of defect (control group, n = 60), and the incision was sutured without any implants (blank group, n = 5). The samples were harvested and observed by examinations of gross, X-ray, bone density, 99mTc-MDP bone scanning, gamma-display ratio and scanning electron microscope (SEM) after 3, 6, 9 and 12 months of operation. The results were compared between the experimental group and control group. RESULTS: At 3, 6, 9 and 12 months after operation, the gross and X-ray examinations indicated that the bone defect filled with the new bone on the PCL-tissue surface, and no delayed inflammatory reaction appeared. The average bone mineral density was greater in the experimental group than that in the control group, and the difference had statistical significance (P< 0. 05). The results of 99mTc-MDP bone scanning and gamma-display ratio showed that the nuclide uptake was more in the PCL group than that in the control group. The SEM result proved that the new compact bone formed on the PCL migrating surface as the PCL degraded gradually,but the collagen fiber sheath formed around the hydroxyapatite in the control group. CONCLUSION: PCL possesses good biocompatibility and high bone inductive potentiality, it can be used to repair bone defect.

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PubMed2002

Fixation of distal femoral osteotomies with self-reinforced poly(desamino tyrosyl-tyrosine ethyl ester carbonate) rods: an experimental study on rats.

Self-reinforced poly(desamino tyrosyl-tyrosine ethyl ester carbonate) poly(DTE carbonate) rods (diameter, 2 mm; length, 26 mm) were implanted into the dorsal subcutaneous tissue of 16 rats. Osteotomies of the distal femur were fixed with these rods (2 mm by 15 mm) in 64 other rats. The follow-up times varied from 1 week to 1 year. After sacrifice, three-point bending and shear tests and molecular weight measurements were performed for subcutaneously placed rods. Radiological, histological, histomorphometrical, microradiographic, and oxytetracycline-fluorescence studies of the osteotomized and intact control femurs were performed. At 36 weeks, the bending strength of the rods was nearly at the same level as the initial value, and the shear strength was decreased to about one quarter of the initial value. One of the 64 evaluated osteotomies showed signs of infection at 24 weeks, and there were five failures of fixation. Fifty-eight osteotomies healed uneventfully. No gross signs of inflammatory or foreign-body reactions were observed. The present investigation showed that the mechanical strength and fixation properties of SR-poly(DTE carbonate) rods are suitable for fixation of cancellous bone osteotomies in rats. The present article is the first report on successful application of SR-poly(DTE carbonate) rods for fixation of cancellous bone osteotomies.

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PubMedDate not supplied

[Biomechanical evaluation of biointegrable suture anchors composed of bovine compact bone in a pull-to-failure test in porcine tibial head specimens].

AIM: Suture anchors of various designs have gained wide acceptance for securing soft tissues to bone. The biointegrable Tutofix CB anchors derived from bovine compact bone are available with diameters of 3 mm (CB3 anchor), 4 mm (CB4 anchor) and 5 mm (CB5 anchor). The CB anchors are push-in anchors and, from the biomechanical standpoint, they are a combination of press-fit and angulation anchors. The purpose of this study was to evaluate the CB anchors for singular pull load-to-failure strength using porcine tibial head specimens as a test model. METHODS: In all specimens, the joint surface was removed by performing a subchondral osteotomy. Axial PQ-CT scans of 12 specimens were obtained to determine the trabecular BMD. The anchors were implanted posteromedially and centrolaterally in the porcine tibial head specimens. After threading the anchors with a steel suture and predrilling of the anchor holes perpendicular to the osteotomy surface they were inserted 4 mm below the osteotomy surface. A universal testing machine applied tensile loads parallel to the axis of insertion at rates of 10 mm/min and 500 mm/min until pull-out failure or anchor breakage and mean anchor fixation strengths were calculated. RESULTS: The fixation strength of the CB anchors was found to be much higher at the dorsomedial implantation site than at the centrolateral implantation site. The CB4 anchors and CB5 anchors provided nearly the same fixation strength at a level much higher than that of the CB3 anchors. Bone mineral density had a strong influence on axial pull-out force of the anchors, especially the CB4 anchors and CB5 anchors. The overall correlation coefficient for bone mineral density with ultimate load-to-failure was 0.869 for the CB4 anchors and 0.716 for the CB5 anchors. Differences in failure strengths were also seen between the low and high extraction rates. With the high extraction rate much higher failure strengths were obtained than with the low extraction rate. The sudden pull eccentrically on the anchors caused a better fixation due to angulation of the anchor within the drill holes. CONCLUSION: In spite of the double worst-case scenario in the testing conditions, the CB anchors provided a high fixation strength in the trabecular bone of porcine tibial head specimens with the CB4 anchors and CB5 anchors being nearly equal and both being superior to the CB3 anchors. Bone mineral density had a strong influence on the axial pull-out force. Our results show that the CB anchors seem to be a reasonable alternative to metal and bioabsorbable suture anchors.

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PubMed2005

Biocompatibility and resorption of a brushite calcium phosphate cement.

A hydraulic calcium phosphate cement with beta-tricalcium phosphate (TCP) granules embedded in a matrix of dicalcium phosphate dihydrate (DCPD) was implanted in experimentally created defects in sheep. One type of defect consisted of a drill hole in the medial femoral condyle. The other, partial metaphyseal defect was located in the proximal aspect of the tibia plateau and was stabilized using a 3.5 mm T-plate. The bone samples of 2 animals each per group were harvested after 2, 4, 6 and 8 weeks. Samples were evaluated for cement resorption and signs of immediate reaction, such as inflammation, caused by the cement setting in situ. Differences regarding these aspects were assessed for both types of defects using macroscopical, radiological, histological and histomorphometrical evaluations. In both defects the brushite matrix was resorbed faster than the beta-TCP granules. The resorption front was followed directly by a front of new bone formation, in which residual beta-TCP granules were embedded. Cement resorption occurred through (i) extracellular liquid dissolution with cement disintegration and particle formation, and (ii) phagocytosis of the cement particles through macrophages. Signs of inflammation or immunologic response leading to delayed new bone formation were not noticed at any time. Cement degradation and new bone formation occurred slightly faster in the femur defects.

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PubMed2003

Scleral plug of biodegradable polymers containing tacrolimus (FK506) for experimental uveitis.

PURPOSE: To evaluate the efficacy of a biodegradable polymeric scleral plug containing the immunosuppressive agent, FK506, in a rabbit model for experimental uveitis. METHODS: The scleral plugs were prepared by dissolving poly(DL-lactide-co-glycolide; PLGA) and FK506 (weight, 8.5 mg; length, 5 mm; 1% FK506). The release of FK506 was evaluated in vitro by spectrophotometry on days 1, 3, 7, 14, 21, and 35. In vivo, FK506 concentrations of the vitreous were measured by high performance liquid chromatography 2 and 4 weeks after intravitreous plug implantation in pigmented rabbits. Sixteen pigmented rabbits were immunized twice subcutaneously with 10 mg of Mycobacterium tuberculosis H37Ra antigen. Twelve days later, the right eyes of all rabbits were challenged with an intravitreal injection of 50 micro g of antigen. After the first challenge, the 16 eyes of 16 pigmented rabbits were divided into two groups. Scleral plugs were implanted into the vitreous of the right eye of eight rabbits. Eight control rabbits received a sham device. The aqueous protein concentrations and cell counts were determined on postchallenge days 7, 14, and 28. To simulated chronic inflammation, the eyes were rechallenged with intravitreal antigen on day 14 and were observed for 1 month. Inflammation of the anterior chamber and the vitreous were graded clinically by two masked observers. Retinal function was evaluated by electroretinography (ERG) and histologic examination. RESULTS: Clinical scores (anterior chamber cells, flare, and vitreous opacity) showed that treated eyes had significantly less inflammation than untreated eyes (P<0.001). Quantitative analysis of inflammatory cells (P<0.001) and protein concentrations (P<0.0001) in the anterior chamber showed significant decreases in treated eyes. Histopathologic examination showed marked inflammation and tissue disorganization in the untreated eyes. No retinal toxicity was detected, histopathologically and electroretinographically. After antigen rechallenge, inflammation in experimental eyes was still less than in control eyes. CONCLUSIONS: Intravitreal sustained-release of FK506 from a biodegradable polymeric scleral plug was highly effective in suppressing the inflammation of experimental uveitis in a rabbit model for at least 6 weeks. This device may be useful in the management of patients with severe chronic uveitis.

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PubMed2004

The use of high-resolution magnetic resonance imaging for monitoring interbody fusion and bioabsorbable cages: an ex vivo pilot study.

OBJECT: Interbody fusion is a gradual process of graft resorption and tissue formation, ideally resulting in a bone bridge between two adjacent vertebral bodies. Initially, fibrous tissue and cartilage are formed, which subsequently are replaced by bone through the process of endochondral ossification. When cages and/or their contents are made of resorbable polymers like lactic or glycolic acids, there is a simultaneous process of implant degradation, which is eventually accompanied by reactions in the surrounding tissues. The purpose of this study was to explore the use of highresolution magnetic resonance (MR) imaging for monitoring tissue differentiation, spinal fusion, cage degradation, and eventually tissue reactions as a function of time. METHODS: Lumbar vertebral segments obtained in 14 goats with 3, 6, and 12 months of follow up (three, four, and seven animals, respectively) were available from a study of the feasibility of poly(L,D-lactic acid) cages for spinal fusion. Plain x-ray films, MR images, and histological sections were used to evaluate spinal fusion and cage resorption. The first follow-up tests revealed that MR imaging noninvasively provided three-dimensional information on cage placement, cage degradation and bone formation, and that it has potential to differentiate between the various soft tissues. CONCLUSIONS: Although the magnetic field strength and thus the resolution used were higher than normal in clinical practice, MR imaging appears to be a promising modality for the noninvasive clinical follow up of patients who undergo fusion with resorbable cages. Tissue reactions were not encountered in this study, and thus could not be evaluated.

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PubMed2004

Using resorbable screws for fixation of cortical onlay bone grafts: an in vivo study in rabbits.

PURPOSE: The purpose of this study is to test bioresorbable screws as an alternative to titanium screw graft fixation. When cortical onlay grafts are used, it is necessary to rigidly immobilize them with titanium screws into the recipient site. The screws must be removed before placing implants into this site. Bioresorbable screws may be an alternative to titanium fixation, eliminating the additional morbidity associated with this. MATERIALS AND METHODS: Fifteen New Zealand White rabbits were divided into 3 groups. Bilateral tibial onlay bone grafts were placed in the mandible and secured using titanium fixation, bioresorbable fixation, or no fixation. After 6 weeks, all grafted sites were harvested. Hematoxylin-eosin and Giemsa staining were performed to evaluate inflammation, graft integration, and thickness. RESULTS: The treatment groups showed evidence of consolidation under light microscopy. Smooth integration of the graft borders with the recipient bone was identified. No integration was seen in the control group. The average thickness of the grafted sites was: 1) bioresorbable, 2.28 mm; 2) titanium, 1.87 mm; and 3) control, 1.06 mm. The differences were statistically significant (P = .0004) between the titanium group and the control group, as well as between the bioresorbable and the control group (P = .01). There was no statistically significant difference between the 2 treatment groups (P = .19). CONCLUSION: The overall thickness of the treatment specimens was greater than that of the control group. The bioresorbable group showed graft integration equal to that of the titanium group, making it an adequate alternative for graft fixation.

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PubMed1998

Effects of bioabsorbable and non-resorbable barrier membranes on bone augmentation in rabbit calvaria.

The aim of this study was to compare the effects of bioabsorbable and non-resorbable membranes on experimental guided bone augmentation in 8 Japanese white rabbits. A cutaneous flap was demarcated and raised from the forehead of each animal, the periosteum was lifted, and the calvarial bone on both sides of the midline was exposed. A titanium screw was inserted into the bone on each side of the midline and one screw was covered with a bioabsorbable (polylactic acid) membrane and the other with a non-resorbable (expanded polytetrafluoroethylene) membrane. The implanted screws and membranes were then covered with the periosteum and cutaneous flap. After healing for 6 months, the animals were euthanized and the experimental area was prepared for histological investigation. New bone had formed under both membranes with no sign of infection or membrane exposure. The amount of newly generated bone (89.0 +/- 17.3% versus 54.7 +/- 14.0%, P <0.05) and the percentage of newly generated bone height (81.5 +/- 6.3% versus 58.9 +/- 7.8%, P <0.05) in the space beneath the non-resorbable membrane was greater than that beneath the bioabsorbable membrane. However, there were no statistically significant differences between the bioabsorbable and non-resorbable membranes with respect to the percentage areas of mineralized bone (52.3 +/- 11.3% versus 47.1 +/- 6.7%, P = 0.8658) and bone marrow (47.7 +/- 11.3% versus 52.9 +/- 6.7%, P = 0.4838) and bone contact with the screw (88.3 +/- 6.9% versus 89.2 +/- 7.3%, P = 0.9999). In conclusion, at least within the limitations of this rabbit model, we suggest that non-resorbable membranes with sufficient stiffness should be used to obtain greater bone volume and height instead of bioabsorbable membranes for the GBR procedure, and that this will facilitate predictable bone augmentation in spaces beyond the bone surface. Therefore, the bioabsorbable membrane could not replace the non-resorbable membrane used in this model.

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PubMed2002

The effect of cage stiffness on the rate of lumbar interbody fusion: an in vivo model using poly(l-lactic Acid) and titanium cages.

STUDY DESIGN: A goat interbody fusion model using poly-(L-lactic acid) and titanium cages was designed to evaluate the effect of cage stiffness on lumbar interbody fusion. OBJECTIVE: To investigate the effect of cage stiffness on the rate of interbody fusion. SUMMARY OF BACKGROUND DATA: Various types of cages considerably exceed the stiffness of vertebral bone, which ultimately may lead to postoperative complications. To avoid these complications, poly-(L-lactic acid) cages with limited stiffness have been designed. The mechanical integrity of the cages remains intact for at least 6 months. METHODS: Interbody fusions were performed at L3-L4 of 15 Dutch milk goats, and one of three cages was randomly implanted: 1) a titanium cage (n = 3), 2) a stiff poly-(L-lactic acid) cage (n = 6), or 3) a flexible poly-(L-lactic acid) cage (n = 6). Interbody fusion was assessed radiographically by three independent observers 3 and 6 months after surgery. RESULTS: At 3 months, all the poly-(L-lactic acid) specimens showed ingrowth of new bone, but with radiolucency in the fusion mass. At 6 months, solid arthrodesis was observed in four of six poly-(L-lactic acid) specimens, advanced ingrowth in one specimen, and infection in one specimen. Titanium cages showed ingrowth of bone, but with radiolucency in the fusion mass. Interbody fusion using poly-(L-lactic acid) cages showed a significantly higher rate statistically (P = 0.016) and more complete fusion than titanium cages of the same design. CONCLUSIONS: The reduced stiffness of poly-(L-lactic acid) cages showed enhanced interbody fusion, as compared with titanium cages after 6 months. Bioabsorbable poly-(L-lactic acid) cages thus may be a viable alternative to current interbody cage devices, thereby avoiding the concomitant problems related to their excessive stiffness. However, the bioabsorbability of the poly-(L-lactic acid) cages awaits investigation in a long-term study currently underway.

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PubMed2003

Scanning electron microscopic observations of 'fractured' biodegradable plates and screws.

BACKGROUND: We encountered two out of 100 cases in which implanted biodegradable plates and screws had fractured within 1 month postoperatively. MATERIAL: Failure of the material was confirmed through clinical symptoms, radiographs or CT findings. In addition, four specimens obtained from these two cases were examined with regard to their ultrastructure using scanning electron microscopy. RESULTS: Several principal patterns of the fractured surface were found: (1) gradual cracking, i.e. 'circular stair' and, (2) tortuous threads, i.e. a wavy line. It is conceivable that the material may not have been hit by major sudden forces but a disproportion between the thread configuration and the drilled hole may have led to screw loosening and torsion. Subsequently, the threads were deformed in a 'wavy' manner, finally leading to cracking and fracture of plates and screws. Fractures of plates and screws due to these instabilities are thought to be distinguishable from material resorption. CONCLUSION: In the application of biodegradable materials, more than two screws per single bone segment should be used as a principle of plate-fixation technique in order to avoid a stability-compromising situation, particularly in the stress-bearing areas of the maxillofacial region. Moreover, three-dimensional fixation using more than two plates is recommended in the facial skeleton e.g. zygomatic tripod. Intermaxillary fixation should also be considered to reinforce initial stability in stress-bearing areas.

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PubMedDate not supplied

In vitro antibiotic release from poly(3-hydroxybutyrate-co-3-hydroxyvalerate) rods.

Provision and maintenance of adequate concentrations of antibiotics at infection sites is very important in treating highly resistant infections. For diseases like implant related osteomyelitis (IRO) it is best to provide this locally via implanted drug formulations, as systemic administration of the antibiotic may not be effective due to damaged vasculature. In this study, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) rods containing 7, 14 and 22% (mol) 3-hydroxyvalerate were loaded with sulbactam:cefoperazone or gentamicin, and their antibiotic release behaviours were studied under in vitro conditions in physiological phosphate buffer at room temperature. The release patterns were representative of release from monolithic devices where a rapid early release phase is followed by a slower and prolonged release. With PHBV 22 rods, the latter phase continued for approximately 2 months. This duration is critical because a proper antibiotic therapy of IRO requires the minimal effective concentration for at least 6 weeks. After in vitro release, voids with sharp edges were detected on the rods, indicating that the drug crystals dissolved but the polymer did not undergo erosion within this test period. Changing the polymer:drug ratio from 2:1 to 20:1 substantially decreased the drug release rate. A change of polymer type, however, did not lead to any detectable changes in the release patterns. Gentamicin release also followed a similar pattern, except that the concentration of the drug in the release medium exhibited a decrease after long release periods, indicating degradation (or decomposition) of the antibiotic in the release medium.

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PubMed2004

Prototype testing for a new bioabsorbable Le Fort III distraction device: a pilot study.

PURPOSE: The goal of the study was to design and test prototypes for a new, internal resorbable Le Fort III distractor in the minipig model. MATERIALS AND METHODS: Le Fort III osteotomies were performed on 3 juvenile minipigs, followed by implantation of the bioabsorbable distractors. After a 5-day latency period, the distraction progressed at a rate of 1 mm/day in 2 equal increments for 12 days. This was followed by a 6-week consolidation phase. Cephalometric radiographs were taken postoperatively, on completion of distraction and after the consolidation phase, to evaluate the amount of distraction that was obtained. Necropsy was performed at the completion of each experiment. RESULTS: The first minipig was sacrificed at the end of the distraction period because of device failure. On necropsy, it was noted that the anterior footplate on either side had failed. The second minipig was sacrificed during the latency period because of severe pneumonia. On necropsy, it was noted that none of the footplates had failed but that the distraction barrels on either side had become dislodged from the anterior bioabsorbable footplates. The third minipig was sacrificed at the end of the distraction period because of device failure. On necropsy, it was noted that the posterior bioabsorbable footplates on either side were fractured across the posterior screw lines. CONCLUSIONS: The bioabsorbable devices evaluated in this study could not withstand the forces generated during distraction osteogenesis in the minipig model. Experience with the prototypes may help in designing internal bioresorbable Le Fort III distraction devices.

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