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Results for “Absorbable Implants”

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PubMed2003

Rotator cuff repair with bioabsorbable screws: An in vivo and ex vivo investigation.

PURPOSE: The purpose of this study was to evaluate in vivo the clinical outcomes of rotator cuff repairs with bioabsorbable screws compared with metal suture anchors, and to compare the ex vivo initial load to failure of rotator cuff repairs using 3 different bioabsorbable screws, suture anchors, and transosseous sutures. TYPE OF STUDY: In vivo clinical outcomes investigation, and ex vivo biomechanical study. METHODS: Three cohorts of patients with rotator cuff tears that measured less than 4 cm(2), were sequentially repaired with Mitek Rotator Cuff QuickAnchors (Mitek Surgical Products, Norwood, MA) (n = 9), Arthrex Headed Bio-Corkscrews (n = 9) (Arthrex, Naples, FL), and Mitek Rotator Cuff QuickAnchors (n = 9). Patients were systematically assessed with a specific shoulder questionnaire and 23 shoulder tests performed preoperatively and at 1 and 6 weeks, 3 and 6 months, and 1 year postoperatively. A correlative ex vivo biomechanical study was performed on 53 ovine shoulders to evaluate the initial failure load properties of bioabsorbable screws compared with fixation with suture anchors and transosseous sutures. RESULTS: In the in vivo portion of the study, the cohort treated with the Headed Bio-Corkscrew demonstrated no improvement on any measured parameter until 1-year after rotator cuff repair. In contrast, shoulders repaired with Mitek Rotator Cuff QuickAnchors demonstrated improved overall shoulder function as early as 6 weeks postoperatively (P =.002), had a better constant score at 1-year after repair (88 +/- 9 v 73 +/- 17; P =.016), and a lower rate of revision rotator cuff repair (P =.029). In the ex vivo portion of the study, the bioabsorbable headed screws, Headed Bio-Corkscrew (100 +/- 30 N) and BioTwist (76 +/- 35 N), had inferior initial failure load properties compared with suture anchors (140 +/- 36 N) and transosseous sutures (147 +/- 68 N). In contrast, the BioCuff (190 +/- 56 N), a bioabsorbable implant that used a screw and serrated washer design, had equivalent initial failure load properties as the suture repairs. CONCLUSIONS: This investigation had poorer early outcomes, a lower shoulder functional score 1-year after repair, and a higher rate of repeat surgery in patients who had their rotator cuff repaired with a bioabsorbable screw than in patients who had their shoulders repaired with a standard metal suture anchor. Furthermore, the biomechanical testing demonstrated a lower tensile load to failure in the tendons repaired with a simple screw design compared to suture anchors with a mattress stitch. Of note, the implant that used a screw and washer design demonstrated a greater ability to resist initial tensile load.

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PubMed2005

FK506 in a biodegradable glycolide-co-clatide-co-caprolactone polymer for prolongation of corneal allograft survival.

PURPOSE: FK506 has been extensively used in preventing immune rejection for human organ transplantation. This study aimed to evaluate the effects of a biodegradable FK506 drug delivery system (DDS) implanted into anterior chamber for the prolongation of corneal allograft survival in high-risk keratoplasty. METHODS: Biodegradable glycolide-co-clatide-co-caprolactone polymer (PGLC) was used as drug carrier to be incorporated with 0.5 mg of FK506 powder. The drug release from the FK506-PGLC DDS was evaluated in vitro and in vivo. The FK506-PGLC DDS was implanted into the anterior chamber of 12 high-risk keratoplasty rabbits. The graft survival time and clinical features of the FK506-PGLC DDS group were compared with the untreated, PGLC DDS, cyclosporin A-PGLC DDS, and 0.5% FK506 drops groups. The histopathological examination was performed to evaluate the safety of the FK506-PGLC DDS. RESULTS: The mean graft survival time was longest (> 180 days) in the FK506-PGLC DDS group. In vivo, the FK506 concentration in aqueous humor peaked on day 28 (17.9 +/- 2.3 ng/ml) and kept a sustained release for at least 168 days. No adverse reactions were observed in the FK506-PGLC DDS group. CONCLUSIONS: Biodegradable FK506-PGLC DDS implanted into anterior chamber can effectively prevent immune rejection in high-risk keratoplasty model, presenting a promising approach for the prolongation of corneal allograft survival.

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PubMed2001

Resorption kinetics of eggshell: an in vivo study.

Eggshell has been recently introduced as a bone substitute candidate in reconstructive surgery. The aim of this experimental study study was to determine its degradation rate in both a skeletal and extraskeletal site. In experiment 1, eggshell particles with four different sizes (50, 75, 150, and 300 microns in diameter) were implanted in subcutaneous pouches of 30 rats. In experiment 2, a fragment of ostrich eggshell was implanted on the nasal dorsum of 10 rats. Animals were sacrificed at 1 (N = 10), 2 (N = 10), and 4 months (N = 10) during the first stage of the study, and at 1 year during the second stage of the study. The results were assessed by X-ray examination and routine histological techniques. In experiment 1, all animals healed uneventfully. At 1 month, only 50-micron particles had undergone resorption. At 2 months, both 50- and 75-micron particles had undergone resorption. At 4 months, the 150- and 300-micron particles were resorbed incompletely. Histologically, the eggshell elicited a mild inflammatory reaction at 1 month that decreased progressively at further stages. In experiment 2, all animals except one healed uneventfully. Radiologically, the eggshell implant displayed a noticeable stability. Histologically, seven of nine implants were encapsulated, but two of them were surrounded by a bony rim. In conclusion, eggshell is a resorbable implant, but the degradation kinetic is size dependent. Large ostrich grafts are also suitable as onlay graft, but a complementary osteosynthesis is recommended to enhance osteointegration.

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PubMed2003

Reconstruction of the immature craniofacial skeleton with a carbonated calcium phosphate bone cement: interaction with bioresorbable mesh.

Calcium phosphate cements have been recently introduced for use in craniofacial reconstruction. In the clinical setting, however, pulsations of the underlying brain and dura may interfere with the crystallization of these cements, thereby rendering their use in cranioplasty problematic. To circumvent such problems, many clinicians have interposed synthetic resorbable plates or mesh between the dura and the cement. At the present time, however, little is known about the influence of such materials or their breakdown products on the fate of calcium phosphate cements. The specific aim of this project was to evaluate the biocompatibility, osteoconductivity, and remodeling capacity of a calcium phosphate cement after implantation into experimental calvarial defects when combined with a resorbable mesh underlay. Four 10-mm diameter full-thickness calvarial defects (two frontal, two parietal) were created in each of six 3-week-old Yorkshire pigs. The defects were treated as follows: 1) empty control, 2) macroporous polylactic acid (70/30 L/DL polylactic acid [PLA]) mesh, 3) Norian CRS calcium phosphate cement, and 4) Norian CRS over PLA mesh underlay. Animals were divided into two groups. Half of the animals were killed 30 days after surgery, and half were killed 180 days after surgery, and the graft recipient sites were examined histologically. At 30 days, minimal bone ingrowth was observed in untreated calvarial defects or in those that were treated with PLA plates alone. Defects treated with the cement alone demonstrated a modest amount of new woven bone deposition, primarily at the periphery of the implants. Defects treated with calcium phosphate cement over PLA mesh underlays were characterized by remodeling and woven bone deposition at 30 days, with complete or near-complete osseous bridging of the ectocranial implant surfaces. Progressive bone ingrowth was noted in all defects at 180 days, with near-complete replacement of all Norian CRS implants by host bone. The PLA mesh remained incompletely resorbed at 180 days. No inflammatory response to the implants was observed at either time point. Calcium phosphate cement may be safely used for craniofacial reconstruction in the presence of PLA implants without compromise to its biocompatibility, osteoconductivity, or remodeling capacity.

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PubMedDate not supplied

Regeneration of segmental diaphyseal defects in sheep tibiae using resorbable polymeric membranes: a preliminary study.

OBJECTIVE: To investigate whether a long bone cortex of well-defined thickness can be regenerated by using an anatomically designed membranous resorbable "tube-in-tube" implant and to establish the functions of membranes in the healing of segmental diaphyseal bone defects larger than the "critical size." DESIGN: Bone healing in segmental diaphyseal defects larger than the critical size in the sheep tibiae covered with a single porous tubular membrane or implanted with anatomically shaped porous double tube-in-tube membranes was evaluated. Membranes with different pore structures were applied alone and/or in combination with autogenous bone graft. BACKGROUND: Healing of segmental diaphyseal bone defects in animals can be enhanced by covering the defects with resorbable polylactide membranes. Based on the results of bone healing in defects ten millimeters long in the rabbit radii, it was suggested that the membrane prevents muscle and soft tissue from invading the defect and maintains osteogenic cells and osteogenic substances within the space covered with membrane, thus promoting new bone formation. The functions of membranes may differ, however, depending on the size and the location of the defect and on the experimental species used. Bone defects larger than the critical size may not heal at all, even if membranes are used. The critical-size defect is defined as the smallest bone defect that does not heal spontaneously when covered with polymeric membranes. To heal such defects, it is mandatory that membranes are used in combination with autogenic bone graft and/or a suitable bone substitute. If bone graft is used to fill the defect, the structure and geometry of the covering membrane will determine whether the graft will be vascularized and/or nourished from the surrounding soft tissue and, in consequence, survive. It can be appreciated that bone healing in areas of good vascularity should be more efficient than bone healing in poorly vascularized areas. The influence of all these factors on healing of bone in segmental diaphyseal defects covered with membranes is not known. METHODS: Four-centimeter-long diaphyseal segmental defects in the tibiae of six- to seven-year-old Swiss mountain sheep were covered with resorbable membranes from poly(LDL-lactide). In Group 1, a single microporous external membrane was used. In Group 2, one microporous membrane was inserted into the medullary cavity at the cut ends of the tibiae (internal membrane), and the other microporous membrane was placed on the outer surface of the cortex (external membrane). In Group 3, a single microporous external membrane was also laser-perforated to produce openings with a diameter in the range of 800 to 900 micrometers. In Group 4, the defect was filled with autogenous cancellous bone graft and covered with a single perforated membrane. In Group 5, one perforated internal membrane was inserted into the medullary cavity at the cut ends of the tibiae, and the other perforated membrane was placed on the outer surface of the cortex. Group 6 was identical to Group 5, except that cancellous bone graft was placed in the space between these two membranes. RESULTS: There was no bone healing in Groups 1, 2, 3, and 5. Only in Groups 4 and 6 did the defects heal. In Group 4, new bone was dispersed across the "medullary canal" formed by the membrane. In Group 6, the new bone had grown into the space between the outer and inner membranes, forming the "neocortex." CONCLUSIONS: The resorbable polymeric implant consisting of two concentric perforated membranes (the tube-in-tube implant) used in combination with cancellous bone graft to treat segmental diaphyseal defects in sheep tibiae allows for the reconstitution of the "neocortex" with well-defined thickness. (ABSTRACT TRUNCATED)

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PubMed2005

Implantation of esterified hyaluronic acid in microdissected Reinke's space after vocal fold microsurgery: first clinical experiences.

OBJECTIVE: In this pilot study are presented the first clinical experiences of the use of a resorbable bioimplant made of esterified hyaluronic acid inserted in the microdissected superficial layer of the lamina propria (SLLP), also called Reinke's space, after a flap excision procedure for a benign vocal fold lesion. Laryngeal and vocal evolution of implanted patients are depicted and discussed. STUDY DESIGN: Eleven bio-implants have been inserted in microdissected SLLP of 11 cases presenting with benign vocal fold lesions. The surgical procedure consisted of the excision of primary lesion by a microflap technique immediately followed by implantation of esterified hyaluronic acid in Reinke's space. METHODS: All patients underwent rigid laryngoscopy and a microsurgical procedure under general anesthesia. The cordal lesion was treated with cold instrumentation of Bouchayer (7 cases) or with a mixed technique using CO(2) laser (4 cases). After the classical freeing-up of Reinke's space and the creation of a mucosal flap, a few fibers of esterified hyaluronic bioimplant are gently arranged in Reinke's space before redraping the ligament and closing the cordal incision with a few drops of fibrin glue. Laryngeal and vocal assessments were performed pre- and postoperatively in all patients using videostroboscopy as well as perceptual and objective voice evaluation. All patients were followed in a longitudinal manner: between two and five postoperative evaluations were performed. The longest follow-up was 19 months and the shortest 2 months. RESULTS: All cases exhibited postsurgical improvement of the pliability of the SLLP. None of them developed an adverse scarring process. Improvement of SLLP's pliability was maintained in time in all cases. Vocal improvement was observed in all. Temporary inflammation was noted in one case. There were no serious adverse effects apparent during the follow-up period. CONCLUSION: Bio-implantation of esterified hyaluronic acid in Reinke's space is technically easy and well tolerated. All treated cases exhibited postoperative good pliability of the SLLP compared with their preoperative evaluation.

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PubMed2001

A novel approach to temporary stenting: degradable cardiovascular stents produced from corrodible metal-results 6-18 months after implantation into New Zealand white rabbits.

OBJECTIVE: To determine whether corrodible materials may be safely used as biodegradable cardiovascular implants. DESIGN: Corrodible iron stents (> 99.8% iron) were produced from pure iron and laser cut with a stent design similar to a commercially available permanent stent (PUVA-AS16). A total of 16 NOR-I stents were implanted into the native descending aorta of 16 New Zealand white rabbits (mean luminal diameter at the implantation site 3.4 mm, balloon diameter to vessel diameter ratio 1.13). RESULTS: No thromboembolic complications and no adverse events occurred during the follow up of 6-18 months. All stents were patent at repeat angiography after 6 (n = 9), 12 (n = 5), and 18 months (n = 2) with no significant neointimal proliferation, no pronounced inflammatory response, and no systemic toxicity. CONCLUSIONS: This initial in vivo experience suggests that degradable iron stents can be safely implanted without significant obstruction of the stented vessel caused by inflammation, neointimal proliferation, or thrombotic events.

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PubMed2002

Liquid photocurable biodegradable copolymers: in vivo degradation of photocured poly(epsilon-caprolactone-co-trimethylene carbonate).

Liquid photoreactive poly(epsilon-caprolactone-co-trimethylene carbonate)s endcapped with a coumarin group [coumarinated poly(CL/TMC)s] were prepared using tetra-functional hydroxylated substances such as pentaerythritol or four-branched poly(ethylene glycol), b-PEG. These coumarinated copolymers are tetra-branched and exist as a viscous liquid (MW 5 x10(3) approximately 7 x 10(3)). They were photocured by ultraviolet (UV) light irradiation to obtain a swelling or nonswelling solid under water, depending on the type of initiator used. The resultant films were implanted into the subcutaneous tissues of rats for up to 5 months. The photocured b-PEG-based copolymer was completely degraded and sorbed within a 1 month. On the other hand, surface-eroding degradation of pentaerythritol-based, coumarinated poly(CL/TMC) progressed with implantation time, and minimal recruitment of neutrophils, macrophages, and multinucleated giant cells was observed over the implantation period. Among the pentaerythritol-based copolymers, the fastest surface erosion was observed for the copolymer with the highest epsilon-caprolactone content. Microfabricated films with microarrays in which photoconstructs were stereolithographically prepared, using three different coumarinated copolymers at different regions, showed that upon implantation there was regionally differentiated biodegradation of microarrays, and the degree of region-specific biodegradation depended on the type of photocured copolymer. The observed tendency for biodegradation was in good agreement with that observed during implantation of individual films in vivo. This study also demonstrates that the use of multi-material-arrayed films enables the determination of different responses in vivo using only one sample.

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PubMed2006

Arthroscopic collagen meniscus implant results at 6 to 8 years follow up.

Meniscal substitution is a fundamental procedure to prevent osteoarthritis of the knee after massive meniscectomy. Stone, Steadman and Rodkey have developed a bioreadsorbable collagen matrix (CMI) which acts as a scaffold to restore the original medial meniscal. The objective of this study was to prospectively evaluate the results of CMI implantation at a follow up from a minimum of 6 to a maximum of 8 years. Eight patients (mean age 25) were evaluated at a final observation point from 6 to 8 years after CMI implantation. Inclusion criteria were an irreparable meniscal tear or a previous meniscectomy involving the medial meniscus. Follow up evaluation included Cincinnati Knee Rating Scale (CKRS), IKDC, subjective evaluation and X-ray and MRI control. There were no complications related to the device. All patients were able to return to day activities without limitations 3 months after surgery. Both subjective CKRS score and objective IKDC score showed improvement in all cases except one patient with an ACL re-injury. In two cases scores were slightly worse from 2 years after surgery to the final observation point. The other five cases obtained maximum score at final follow-up. In four cases the absence of pain remained until the final observation point, while in four cases a low entity of pain was described at long term follow-up. MRI showed in five cases mixoid degeneration signal, two had normal signal with reduced size, while one patient had no recognizable implant. Six patients had preserved cartilage and articular space, with no changes respect to pre-op control. Arthroscopic second look evaluation has been performed in three cases, revealing in two cases the presence of the implant, although with a reduced size respect to the original one, while in one case the CMI was almost disappeared. Our small series of eight patients prospectively followed from 6 to 8 years of follow-up has shown highly satisfactory results. Although the aspect of the implant was mostly abnormal, the implant may have helped reduce the deterioration of the knee joint at final observation time.

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PubMed2004

Orbital floor reconstruction with poly-L/D-lactide implants: clinical, radiological and immunohistochemical study in sheep.

In this study the reconstruction capacity of orbital wall in sheep was evaluated when poly-L/D-lactide (PLDLA96) implants were used for large blow-out defects in 18 sheep. The contralateral side, where the defects healed spontaneously, served as controls. The follow-up was 12, 16, 22 and 36 weeks. Healing was evaluated clinically, radiologically, histologically and immunohistochemically. Physiochemical properties of the implants were also studied. At first, the implants were surrounded by elastic capsules, which gradually ossified. At 36 weeks, 60% were still visible and deformed but surrounded by bone. Light microscopy revealed a low grade inflammatory reaction. Expression of Tn-c and cFn was intense throughout the study. Shear strength decreased gradually and was not measurable after 16 weeks. Crystallinity increased steadily from 1.5 to 29.30% and molecular weight decreased from 49,000 to 4186. In CT, the final bony defect was smaller in the reconstructed sides than in the controls. Based on this study it can be concluded that PLDLA96 implant provokes a local inflammation, which does not prevent bone healing. The deformation of the implant, however, indicates that this PLDLA96 plate is not suitable for orbital floor reconstruction.

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PubMed2005

Biodegradable polydioxanone and poly(l/d)lactide implants: an experimental study on peri-implant tissue response.

Several implants for orbital wall fracture treatment are available at the present, but they have drawbacks: resorption, risk for migration and foreign body reaction. Alloplastic resorbable implants would be advantageous: no removal operation and no donor side morbidity. The purpose of this study was to evaluate the foreign body reaction, capsule formation and mechanical properties of two bioresorbable implants. PDS and SR-P(L/DL)LA mesh sheet (70/30) with solid frame (96/4) implants (SR-P(L/DL)LA 70,96) were placed into subcutaneous tissue of 24 rats. Immunohistochemistry was used to evaluate reactivity for Tn-C, alpha-actin, type I and III collagens and two mononuclear cells: T-cells and monocyte/ macrophage. GPC, DSC and SEM were performed. Student's t-test or nonparametric Kruskall-Wallis test were used for statistical analysis. Histology of peri-implant capsule exhibited an inner cell-rich zone and an outer connective tissue zone around both materials. Tn-C reactivity was high in the inner and alpha-actin in the outer zone. At the end of the study, the difference of type I collagen versus type III collagen reactivity in inner zone was statistically significant (P<0.0001) as was the difference of type I collagen versus type III collagen reactivity in outer zone (P<0.0001). Immunohistochemistry did not reveal any statistical differences of T-cell and monocyte/macrophage reactivity around PDS versus SR-P(L/DL)LA 70,96 implants, nor any differences as a function of time. PDS were deformed totally after 2 months. SR-P(L/DL)LA 70,96 implants were only slightly deformed during the follow up of 7 months. PDS degraded rapidly in SEM observation. Particles were detaching from surface. SEM observation revealed that polylactide implant was degrading from the surface and the inner porous core became visible. The degradation came visible at 7 months. There were cracks in perpendicular direction towards to the long axis of the filaments. M(w) of PDS decreased fast compared to the polylactide implant. Foreign body reaction was minimal to both materials but continued throughout the whole observation period. Mechanically PDS was poor, it looses its shape totally within 2 months. It cannot be recommended for orbital wall reconstruction. New mesh sheet-frame structure (SR-P(L/DL)LA 70,96) approved to be mechanically adequate for orbital wall reconstruction. It seems not to possess intrinsic memory and retains its shape. The resorption time is significantly longer compared to PDS and is comparable to other studied P(L/DL)LA copolymers. Thus, the new polylactide copolymer implant may support the orbital contents long enough to give way to bone growth over the wall defect.

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PubMed2005

Instrumented transforaminal lumbar interbody fusion with bioresorbable polymer implants and iliac crest autograft.

STUDY DESIGN: Twenty-seven patients underwent instrumented transforaminal lumbar interbody fusion (TLIF) procedures using bioresorbable implants as interbody spacers. The greater than 2-year clinical and radiographic results of this series are presented along with as a review of relevant preclinical and preliminary clinical studies of bioresorbables. OBJECTIVE: To determine the clinical suitability of bioresorbable implants used as interbody spacers in spinal fusion surgery applications, particularly in the TLIF procedure. SUMMARY OF BACKGROUND DATA: Bioresorbable technology has been in clinical use by surgeons of a variety of specialties for over 35 years. The use of bioresorbable implants in spine surgery, however, has only been widely investigated in the last several years. The use of slowly degrading bioresorbable implants has the potential for load sharing during fusion when used for interbody applications, retaining imaging quality after fusion, obviating later implant removal, providing biologic barriers as well as other various applications. Animal studies and early clinical series with the use of these materials for a variety of indications have been encouraging. METHODS: This study evaluates the use of bioresorbable polymer spacers manufactured with a 70:30 copolymer of poly-L-lactide and D,L-lactide as interbody spacers in 27 of 31 patients with 2 years or more follow-up who underwent instrumented TLIF for primarily degenerative indications. RESULTS: At a mean of 31.9 months follow-up, 25 patients (92.6%) were judged to have solid fusions and 22 patients (81.5%) had good to excellent results. Three patients (11.1%) experienced complications, none of which were directly or indirectly attributable to the use of the bioresorbable polymer implant. Only one implant in 1 patient (3.7%) demonstrated mechanical failure on insertion, and that patient exhibited no clinical sequelae. CONCLUSIONS: Bioresorbable implants have significant potential for use in spine surgery. This potential is realized in this first published clinical series using bioresorbable implants as interbody spacers with a minimum follow-up of 2 years, significantly exceeding the biologic "life expectancy" (12-18 months) of the implant material. Both the clinical and radiographic results of this study support the use of interbody devices manufactured from bioresorbable polymers for structural interbody support in the TLIF procedure.

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PubMed2002

Composite poly(lactide)/hydroxylapatite screws for fixation of osteochondral osteotomies. A morphometric, histologic and radiographic study in sheep.

The aim of this study was to evaluate the healing of an osteochondral fragment created in the distal sheep femur in response to fixation with a biodegradable polylactide/hydroxylapatite composite screw. Poly(L-lactide) screws were used for comparison. At follow-up times of 4 and 8 weeks, the specimens were examined with standard radiography and computed tomography, as well as with macro- and micro-histomorphometry. The intact contralateral femur served as a control. Only minimal signs of degradation of the polymer could be seen in the histologic specimens. At 8 weeks, nearly all osteotomies had healed completely and an association between implant type and delayed osteotomy healing was found. The width of the repair tissue at the tissue-implant interface was 250 +/- 48 microm, representing a clear transition zone of newly formed trabecular bone separating the implant from the surrounding plexiform bone. This study showed that large polylactide implants which are buffered with hydroxylapatite show benign tissue responses and good implant osteointegration. The osteotomy healing in a weight-bearing osteochondral fragment model in sheep utilizing a composite polylactide/hydroxylapatite screw was equivalent to a similar polylactide screw implant, indicating that hydroxylapatite-buffered screw implants could be used for similar indications in current clinical use.

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PubMed2006

Transplantation of cultured progenitor cells to the mammalian retina.

Multipotent progenitor cells have now been isolated from the brain and retina, expanded in culture, and transplanted to the central nervous system (CNS). Work in rodent models has shown that progenitor cells derived from the CNS readily engraft in the diseased retina of mature recipients, where they develop morphologies appropriate to the local microenvironment and express mature markers, including the photoreceptor protein rhodopsin. There is also evidence for graft-associated rescue of host photoreceptors and preservation of light sensitivity in the degenerating retina. Graft survival does not necessarily require immune suppression, as CNS progenitors can behave as an immunoprivileged cell type. The use of biodegradable polymers results in an organised implant and further improves graft survival. Efforts are underway at present to extend this work to the pig, with initial results showing engraftment in both the neural retina and retinal pigment epithelium (RPE).

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PubMed2001

[Guided bone regeneration around dental implants using a bioabsorbable membrane. A pilot investigation in experimental animals].

The aim of this experimental investigation was to evaluate the effect of guided bone regeneration around immediately placed implants using different barrier membranes. Five adult fox hounds were used in this investigation. After extraction of all premolars in the lower jaw, implant osteotomies in the regions of the former premolars and additional buccal bone defects (5 mm x 5 mm) were created. Subsequently, the implants were placed. The defects were treated with one of the following three modalities: (a) guided bone regeneration, using a bioinert expanded polytetrafluoroethylene membrane, (b) no membrane application and (c) guided bone regeneration, using a bioabsorbable membrane made from a synthetic copolymer of lactide and glycolide. After a healing period of six months, the animals were sacrificed and the implants with the surrounding tissues processed for histologic evaluation. The clinical pretreatment defects between the different treatment groups were not statistically different (bioinert membrane group: 4.8 mm; control group: 4.3 mm; bioabsorbable membrane group: 4.9 mm). The remaining histological defects after a healing period of 6 months amounted to 3.2 mm for the nonresorbable group, to 5.6 mm for the control and to 6.3 mm for the bioabsorbable group. A significant difference was observed between the bioinert membrane group and the other two groups. The mineralized bone-to-implant contact in the bioinert membrane group was 52%, in the control group 47% and in the bioabsorbable membrane group 43.3%. The values were not statistically significant different. The results of this study indicate that a partial bone regeneration with bioinert e-PTFE membranes around immediately placed implants is possible. The utilized bioabsorbable polylactide/polyglycolide membrane did not show any bone regenerative effect, and the results did not differ from the control group without membrane application.

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PubMed2004

Tissue-engineered grafts matured in the right ventricular outflow tract.

Autologous smooth muscle cell (SMC)-seeded biodegradable scaffolds could be a suitable material to repair some pediatric right ventricular outflow tract (RVOT) cardiac anomalies. Adult syngenic Lewis rat SMCs (2 x 10(6)) were seeded onto a new biodegradable copolymer sponge made of epsilon-caprolactone-co-L-lactide reinforced with poly-L-lactide fabric (PCLA). Two weeks after seeding, the patch was used to repair a surgically created RVOT defect in an adult rat. At 8 weeks after implantation the spongy copolymer component was biodegraded, and SM tissue and extracellular matrices containing elastin fibers were present in the scaffolds. By 22 weeks more fibroblasts and collagen were present (p < 0.05). The number of capillaries in the grafts also increased (p < 0.001) between 8 and 22 weeks. The fibrous poly-L-lactide component of the PCLA scaffold remained. The 22-week grafts maintained their thickness and surface area in the RVOT. The SMCs prior to implantation were in a synthetic phenotype and developed in vivo into a more contractile phenotype. By 8 weeks the patches were endothelialized on their endocardial surfaces. Future work to increase the SM tissue and elastin content in the patch will be necessary before implantation into a pediatric large-animal model is tested.

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PubMed2004

[Prevention of alveolar ridge resorption after tooth extraction--a review].

Alveolar bone resorption is frequently observed after tooth extraction. Atrophy of the alveolar ridge may cause esthetic and surgical problems in prosthetic dentistry. Augmentative measures may thus be required to guarantee optimal prosthetic replacement of the lost tissues. Augmentative bone treatment may result in extensive surgical interventions and increased treatment costs. Alveolar ridge prophylaxis immediately upon tooth extraction may reduce such sequelae for both, the treating dentist and the patient. Attempts to reduce alveolar bone resorption have included the placement of natural roots, root analogues, and immediate implants into the extraction socket, sometimes in combination with membrane or graft techniques. In the current review of the literature, techniques for alveolar ridge preservation are discussed.

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PubMed2006

False magnetic resonance imaging persistence of a biodegradable anterior cruciate ligament interference screw with chronic inflammation after 4 years in vivo.

Surgeons should be aware that the degradation kinetics of biodegradable implants likely influence the rate of osseous integration, and depend on numerous factors such as polymer weight, crystallinity, and stereocopolymer ratio. We present a case of inflammatory reaction at a polylactide tibial interference screw site more than 4 years after primary anterior cruciate ligament (ACL) reconstruction. This inflammation was presumptively treated as an infection with surgical irrigation and debridement. Preoperatively, the screw was clearly delineated by magnetic resonance imaging (MRI), yet was grossly absent at surgery. Postoperative MRI confirmed thorough debridement and complete absence of the screw. This report shows that not only can a late inflammatory reaction occur, after up to 4 years in vivo, but that the MRI may show a persistent screw despite significant biodegradation. False MRI-persistent screws should be considered when critically reviewing studies that use MRI in the methods for evaluating biodegradable implants. More importantly, false MRI-persistent screws may have significant ramifications when planning revision surgery after primary ACL reconstruction having used interference screws that can degrade over several years.

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