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PubMed2005

Four-year follow-up of poly-L-lactic Acid cages for lumbar interbody fusion in goats.

BACKGROUND: New applications of bioabsorbable polymer implants demand for histologic evaluation because a host tissue response is elicited and late complications after polymer implantation have been reported. Furthermore, in load-bearing regions an accelerated polymer degradation and foreign body reaction may be observed. METHODS: Lumbar interbody fusion procedures were performed using poly-L-lactic acid (PLLA) and titanium cages in 43 goats. At 3, 6, 12, 24, 36, and 48 months after surgery, sequential histologic analysis of instrumented motion segments, lymph nodes, and nervous structures was performed. Blood samples were retrieved for laboratory analysis. RESULTS: No adverse local or distant histologic or systemic effects were observed during the absorption of the poly-L-lactic acid cages. Interbody fusion was maintained, and only a very mild inflammatory response was observed. In half the specimens complete absorption was observed, and in the remaining specimens an estimated 1-10% of the original PLLA was present at the 3-year follow-up. At the 4-year follow-up, five out of seven PLLA specimens showed no PLLA particles under polarized light microscopy. In the remaining two specimens an estimated 1% of the original PLLA could be observed. CONCLUSIONS: Poly-L-lactic acid cages are feasible for lumbar interbody fusion, and the biocompatibility under high load bearing conditions is excellent during the complete absorption of the PLLA interbody fusion cages.

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PubMed1998

Biodegradable rods in adult osteochondritis dissecans of the knee.

Symptomatic osteochondritis dissecans of the knee in skeletally mature patients does not follow a predictable natural history and there has been a trend toward internal fixation of the unstable fragment(s) where possible. Biodegradable implants are enticing for intraarticular use: implant removal is unnecessary and its degradation potentially allows a gradual shift of loading stress to the fracture site. Nine patients with a mean age of 18.6 years (range, 14-23 years) deemed skeletally mature by plain film radiography underwent internal fixation of fragments by 2-mm self reinforced polylactic rods. Six procedures were completed arthroscopically and three required arthrotomy. All fragments were of the medial femoral condyle. The procedure was tolerated well although three patients had early postoperative serosanguinous effusions develop that did not recur after one aspiration. At a mean followup of 33 months (range, 24-54 months), eight fragments radiographically were united whereas one remained ununited at 26 months, accounting for the one poor result in this series. Seven patients had good to excellent results according to Hughston's criteria and were satisfied with the procedure. One of these seven patients had a spontaneous effusion develop at 5 months that did not recur after aspiration and intraarticular steroid injection. Severe, unremitting synovitis did not occur in any patient. Internal fixation of osteochondritis dissecans of the knee with biodegradable polylactic rods provided satisfactory control of symptoms in the short term and resulted in radiographically stable lesions in eight of nine patients. These rods may be suited best for fragmented lesions with intact articular cartilage as an adjunct to drilling.

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PubMed2003

Bioabsorbable miniplating versus metallic fixation for metacarpal fractures.

Bioabsorbable implants offer an attractive alternative to metallic implants to stabilize small bone fractures in the hand. Self-reinforced bioabsorbable miniplating for metacarpal fractures was studied in bones from cadavers and compared with standard metallic fixation methods. One hundred twelve fresh-frozen metacarpals from humans had three-point bending and torsional loading after transverse osteotomy followed by fixation using seven methods: (1) dorsal and (2) dorsolateral 2-mm self-reinforced polylactide-polyglycolide 80/20 plating, (3) dorsal and (4) dorsolateral 2-mm self-reinforced poly-L/DL-lactide 70/30 plating, (5) dorsal 1.7-mm titanium plating, (6) dorsal 2.3-mm titanium plating, and (7) crossed 1.25-mm Kirschner wires. In apex dorsal and palmar bending, dorsal self-reinforced polylactide-polyglycolide and poly-L/DL-lactide plates provided stability comparable with dorsal titanium 1.7-mm plating. When the bioabsorbable plates were applied dorsolaterally, apex palmar rigidity was increased and apex dorsal rigidity was decreased. Bioabsorbable platings resulted in higher torsional rigidity than 1.7-mm titanium plating and in failure torque comparable with 2.3-mm titanium plating. Low-profile selfreinforced polylactide-polyglycolide and poly-L/DL-lactide miniplates provide satisfactory biomechanical stability for metacarpal fixation. These findings suggest that bioabsorbable miniplating can be used safely in the clinical stabilization of metacarpal and phalangeal fractures.

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PubMed2005

Mandibular defect repair by TGF-beta and IGF-1 released from a biodegradable osteoconductive hydrogel.

PURPOSE: Bone regeneration is crucial in the healing of defects in the craniofacial complex. The ability of transforming growth factor-beta1 (TGF-beta1) and insulin-like growth factor-1 (IGF-1), incorporated into a hydrogel scaffold to induce bone regeneration, was evaluated in a rat mandible defect model. MATERIAL AND METHODS: Hydrogel scaffolds containing either transforming growth factor-beta1 (TGF-beta1), insulin-like growth factor-1 (IGF-1), TGF-beta+ IGF-1, or saline, were implanted in rat mandibular bone defects. In a control group the defects were treated by saline alone. Bone defect healing was tested after 3 and 6 weeks by radiology and morphology. RESULTS: Soft tissue radiographs indicated that the area of new bone formation increased gradually after 3 and at 6 weeks. The percentage of closure after 3 weeks was less than the percentage closure after 6 weeks. The amount of calcified material in the TGF-beta and TGF-beta+IGF-1-treated groups had increased more than in the saline-containing hydrogel and control (saline-treated) defects. The percentages of defect closures were 37, 38, 24, 14, and 11% after 3 weeks, and 94, 91, 84, 72, and 29% after 6 weeks, in the TGF-beta+IGF-1, TGF-beta, IGF-1, saline containing hydrogel and saline-treated animals, respectively. Three-dimensional computerized tomography (3D CT) images showed that the 3D shape of the bones was restored. Morphological analysis of the defects treated with hydrogel containing TGF-beta, IGF-1 or TGF-beta+IGF-1 revealed significant bone formation after 6 weeks. CONCLUSION: It is concluded that the hydrogel scaffold impregnated with growth factors can induce bone regeneration and is therefore a promising surgical tool for enhancement of surgical repair of bone defects.

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PubMed2003

Biodegradable gelatin hydrogel potentiates the angiogenic effect of fibroblast growth factor 4 plasmid in rabbit hindlimb ischemia.

OBJECTIVES: We investigated the potentiation of gene therapy using fibroblast growth factor 4 (FGF4)-gene by combining plasmid deoxyribonucleic acid (DNA) with biodegradable gelatin hydrogel (GHG). BACKGROUND: Virus vectors transfer genes efficiently but are biohazardous, whereas naked DNA is safer but less efficient. Deoxyribonucleic acid charges negatively; GHG has a positively charged structure and is biodegradable and implantable; FGF4 has an angiogenic ability. METHODS: The GHG-DNA complex was injected into the hindlimb muscle (63 mice and 55 rabbits). Gene degradation was evaluated by using (125)I-labeled GHG-DNA complex in mice. Transfection efficiency was evaluated with reverse-transcription nested polymerase chain reaction and X-Gal histostaining. The therapeutic effects of GHG-FGF4-gene complex (GHG-FGF4) were evaluated in rabbits with hindlimb ischemia. RESULTS: Gelatin hydrogel maintained plasmid in its structure, extending gene degradation temporally until 28 days after intramuscular delivery, and improving transfection efficiency. Four weeks after gene transfer, hindlimb muscle necrosis was ameliorated more markedly in the GHG-FGF4 group than in the naked FGF4-gene and GHG-beta-galactosidase (control) groups (p < 0.05, Kruskal-Wallis test). Synchrotron radiation microangiography (spatial resolution, 20 microm) and flow determination with microspheres confirmed significant vascular responsiveness to adenosine administration in the GHG-FGF4 group, but not in the naked FGF4-gene and the control. CONCLUSIONS: The GHG-FGF4 complex promoted angiogenesis and blood flow regulation of the newly developed vessels possibly by extending gene degradation and improving transfection efficiency without the biohazard associated with viral vectors.

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PubMed2006

Radiographic, histologic, and chemical evaluation of bioresorbable 70/30 poly-L-lactide-CO-D, L-lactide interbody fusion cages in a goat model.

STUDY DESIGN: A study of lumbar interbody fusion using polylactic acid-based bioresorbable fusion cages in a goat model. OBJECTIVE: To evaluate the effect of polylactic acid polymer composition, and internal stabilization on the rate and quality of interbody fusion. SUMMARY OF BACKGROUND DATA: A spinal cage should provide an appropriate biomechanical environment to facilitate interbody fusion. Previous studies have shown that bioresorbable polylactic acid-based cages can provide adequate stability for spinal fusion. However, at present and to our knowledge, the best bioresorbable materials, optimal cage stiffness, and desired period over which the cage should biodegrade are unknown. METHODS: Interbody fusions were performed at L3-L4 level in 35 skeletally mature Dutch milk goats. Titanium and poly-L-lactide-CO-D,L-lactide (PLDLLA) cages were implanted at random as stand-alone cages. In addition, PLDLLA cages were implanted with anterior fixation. The goats were euthanized at 3, 6, or 12 months. Radiographic, magnetic resonance imaging, histologic, and histomorphometric analyses were performed on retrieved segments. Chemical analysis was used to assess degradation of the retrieved PLDLLA cages. Beforehand, chemical and mechanical degradation of the PLDLLA cages were assessed in vitro. RESULTS: At 3 months, bone graft was almost completely remodeled. Endochondral bone formation was observed in all specimens. At 6 months, 50% of the PLDLLA stand-alone cages and 83% of the PLDLLA anterior fixation cages were fused. At 12 months, 38% of the PLDLLA stand-alone and 83% of the titanium cages realized fusion. A very mild and dispersed foreign body reaction was seen in all PLDLLA specimens. E-beam sterilized PLDLLA cages degraded more rapidly in vivo as compared to both, PLDLLA cages in vitro, and ethylene oxide sterilized poly-L-lactic acid cages in vivo. CONCLUSIONS: Within the 3-6-month period, PLDLLA stand-alone cages provided insufficient mechanical stability, which manifested as cracking and deformation of the cages and lower fusion rates. This result implies that within this time, additional stabilization is required; supplemental internal fixation proved sufficient to obtain successful fusion. In all cases, only a mild host response was seen, indicating good biocompatibility.

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PubMed2000

Bone regeneration by transforming growth factor beta1 released from a biodegradable hydrogel.

This paper describes the sustained release of transforming growth factor beta1 (TGF-beta1) from a biodegradable hydrogel based on polyion complexation for the enhancement of bone regeneration activity. Basic TGF-beta1 was adsorbed onto the biodegradable hydrogel of acidic gelatin with an isoelectric point of 5.0 by an electrostatic interaction. The TGF-beta1 could not be adsorbed onto basic gelatin. When acidic gelatin hydrogels incorporating 125I-labeled TGF-beta1 were implanted into the back subcutis of mice, the radioactivity decreased with time and the in vivo retention of TGF-beta1 was prolonged with a decrease in the water content of hydrogels. The higher the water content of hydrogels, the faster their biodegradation. The in vivo retention of TGF-beta1 correlated well with that of gelatin hydrogels, indicating that TGF-beta1 was released from the gelatin hydrogel as a result of hydrogel biodegradation. The ability of TGF-beta1-incorporated into acidic gelatin hydrogels to induce bone regeneration was evaluated in a rabbit calvarial defect model. Eight weeks after treatment, the gelatin hydrogels with water contents of 90 and 95 wt% induced significantly high bone regeneration compared with those with lower and higher water contents and free TGF-beta1. This indicates that the sustained release of TGF-beta1 from the hydrogel with suitable in vivo degradability is necessary to effectively enhance its osteoinductive function. Rapid hydrogel degradation will result in a retention time of TGF-beta1 which is too short to induce bone regeneration. It is possible that the slow degradation of the hydrogel physically blocked TGF-beta1-induced bone regeneration at the skull defect. It can be concluded that the gelatin hydrogel is a promising matrix of TGF-beta1 release to induce skull bone regeneration.

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PubMedDate not supplied

Theoretical prediction of the hemodynamic performance of slow resorbing polyester protein impregnated arterial prostheses after implantation: a plea for fast resorption of the coating.

The clinical literature cites cases where slow, incomplete, or nonuniform protein resorption from protein impregnated arterial prostheses produces undesirable localized internal capsule proliferation leading to a significant reduction of the internal diameter of the prosthesis. In an attempt to describe the hemodynamic response to this phenomenon, the blood flow in such stenotic regions was simulated and characterized numerically using FIDAP computational fluid dynamics software to determine the Navier-Stokes and continuity equations for simple channel flow. To simulate various stages of internal capsule development, numeric computations were made in an idealized tubular expansion at stenosis ratios ranging from 0.9 to 0.5 and stenosis length ratios from 10 to 40. The results indicated that a triangular annular ring vortex was formed immediately distal to the stenosis at all Reynolds numbers (Re) studied. The size of the vortex increased almost linearly with the Reynolds number. The pressure drop through the stenosis was affected by blood flow rate, severity, and stenosis length. When the stenosis ratio was low, the pressure drop through the stenosis increased gradually and almost linearly with blood flow rate. In a severe stenosis, the pressure drop was no longer a linear function of flow rate, but increased significantly with increasing flow rate. In conclusion, satisfactory healing of the internal capsule requires fast resorption of any impregnated protein. If the resorption is slow, incomplete, or nonuniform, there is a tendency for the lumen to narrow, causing stenosis, an increased pressure drop through the narrowed graft and disturbed flow distal to the stenosis. This phenomenon therefore constitutes a major limitation for using this type of graft in small diameter arterial reconstruction.

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PubMed2005

Biocompatibility and implantation properties of 2 differently braided, biodegradable, self-reinforced polylactic acid urethral stents: an experimental study in the rabbit.

PURPOSE: Biodegradable urethral stents have been in clinical use for more than 10 years. To solve the problems connected with the helical spiral configuration of the stents used to date we developed a new tubular mesh configuration and evaluated the biocompatibility properties and degradation time of 2 differently braided stents in the rabbit urethra. MATERIALS AND METHODS: The biodegradable, self-expanding stents were made of self-reinforced polylactic acid polymer blended with BaSO4 (Alfa Chem, Kings Point, New York). Two braiding patterns, namely a diamond 1/1 and a regular 2/2 + 1 (Prodesco, Perkasie, Pennsylvania), were used to produce a tubular mesh configuration. Stainless steel stents with 1/1 braiding served as controls. The stents were inserted into the posterior urethra of 36 male rabbits. The animals were sacrificed after 1 week, 1 month, 6 months or 12 months. Light microscopy and scanning electron microscopy analyses were done. RESULTS: Tissue reactions to operative trauma were seen in all specimens at week 1. The changes gradually abated in the biodegradable stent groups, whereas chronic inflammatory changes and fibrosis were increasingly seen with metallic stents after 6 months. Epithelial hyperplasia increased with time for all stent types and materials. As expected, stent fragmentation started at 6 months. CONCLUSIONS: Biodegradable polymers are suitable materials for braided urethral stents. However, the braided configuration of the stent with a decreased mass of material does not prevent the development of epithelial hyperplasia. The biodegradable, self-expanding, braided stents functioned well in the rabbit urethra and are suitable for clinical studies.

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PubMed2006

Living autologous heart valves engineered from human prenatally harvested progenitors.

BACKGROUND: Heart valve tissue engineering is a promising strategy to overcome the lack of autologous growing replacements, particularly for the repair of congenital malformations. Here, we present a novel concept using human prenatal progenitor cells as new and exclusive cell source to generate autologous implants ready for use at birth. METHODS AND RESULTS: Human fetal mesenchymal progenitors were isolated from routinely sampled prenatal chorionic villus specimens and expanded in vitro. A portion was cryopreserved. After phenotyping and genotyping, cells were seeded onto synthetic biodegradable leaflet scaffolds (n=12) and conditioned in a bioreactor. After 21 days, leaflets were endothelialized with umbilical cord blood-derived endothelial progenitor cells and conditioned for additional 7 days. Resulting tissues were analyzed by histology, immunohistochemistry, biochemistry (amounts of extracellular matrix, DNA), mechanical testing, and scanning electron microscopy (SEM) and were compared with native neonatal heart valve leaflets. Fresh and cryopreserved cells showed comparable myofibroblast-like phenotypes. Genotyping confirmed their fetal origin. Neo-tissues exhibited organization, cell phenotypes, extracellular matrix production, and DNA content comparable to their native counterparts. Leaflet surfaces were covered with functional endothelia. SEM showed cellular distribution throughout the polymer and smooth surfaces. Mechanical profiles approximated those of native heart valves. CONCLUSIONS: Prenatal fetal progenitors obtained from routine chorionic villus sampling were successfully used as an exclusive, new cell source for the engineering of living heart valve leaflets. This concept may enable autologous replacements with growth potential ready for use at birth. Combined with the use of cell banking technology, this approach may be applied also for postnatal applications.

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PubMed2002

Controlled release of an osteogenic peptide from injectable biodegradable polymeric composites.

Poly(D,L-lactic-co-glycolic acid)/poly(ethylene glycol) (PLGA/PEG) blend microparticles loaded with the osteogenic peptide TP508 were added to a mixture of poly(propylene fumarate) (PPF), poly(propylene fumarate)-diacrylate (PPF-DA), and sodium chloride (NaCl) for the fabrication of PPF composite scaffolds that could allow for tissue ingrowth as well as for the controlled release of TP508 when implanted in an orthopedic defect site. In this study, PPF composites were fabricated and the in vitro release kinetics of TP508 were determined. TP508 loading within the PLGA/PEG microparticles, PEG content within the PLGA/PEG microparticles, the microparticle content of the PPF composite polymer component, and the leachable porogen initial mass percent of the PPF composites were varied according to a fractional factorial design and the effect of each variable on the release kinetics was determined for up to 28 days. Each composite formulation released TP508 with a unique release profile. The initial release (release through day 1) of the PLGA/PEG microparticles was reduced upon inclusion in the PPF composite formulations. Day 1 normalized cumulative mass release from PPF composites ranged from 0.14+/-0.01 to 0.41+/-0.01, whereas the release from PLGA/PEG microparticles ranged from 0.31+/-0.02 to 0.58+/-0.01. After 28 days, PPF composites released 53+/-4% to 86+/-2% of the entrapped peptide resulting in cumulative mass releases ranging from 0.14+/-0.01 microg TP508/mm(3) scaffold to 2.46+/-0.05 microg TP508/mm(3) scaffold. The results presented here demonstrate that PPF composites can be used for the controlled release of TP508 and that alterations in the composite's composition can lead to modulation of the TP508 release kinetics. These composites can be used to explore the effects varied release kinetics and dosages on the formation of bone in vivo.

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PubMed2005

Periodontal repair in dogs: guided tissue regeneration enhances bone formation in sites implanted with a coral-derived calcium carbonate biomaterial.

BACKGROUND: Previous studies suggest that a bioresorbable calcium carbonate coral implant (CI) supports space provision and bone formation for guided tissue regeneration (GTR). However, it could not be discerned whether observed effects were because of GTR or whether the CI possessed osteoconductive properties enhancing bone formation. The objective of this study was to evaluate bone formation associated with the CI biomaterial in the presence and absence of provisions for GTR. METHODS: Routine, critical size, 6 mm, supra-alveolar periodontal defects were created in 12 young adult Beagle dogs. Five animals received the CI alone (Biocoral 1000). Seven animals received the CI/GTR combination using an expanded polytetrafluoroethylene barrier (GORE-TEX Regenerative Material). The animals were euthanized at 4 weeks postsurgery and tissue blocks of the experimental sites were collected and processed for histometric analysis. RESULTS: Clinical healing was uneventful. The histopathologic and histometric analysis revealed significantly increased bone formation (height and area) in sites receiving the CI/GTR combination compared with CI alone (2.3+/-0.6 versus 1.2+/-0.9 mm; and 3.1+/-0.8 versus 1.2+/-1.1 mm2; p<0.05). The CI biomaterial appeared to be mostly unassociated with new bone formation; the CI particles were observed sequestered in newly formed bone, fibrovascular marrow, and in the supra-alveolar connective tissue. Cementum formation was limited and observed in few sites for both treatment protocols. CONCLUSION: While GTR promoted new bone formation, the CI contributed limited, if any, osteoconductive effects.

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PubMed2000

Treatment of subcapital femoral neck fractures with bioabsorbable or metallic screw fixation. A preliminary report.

BACKGROUND AND AIMS: Cancellous bone fractures and arthrodeses have been treated successfully with bioabsorbable polyglycolide and poly-L-lactide implants. In this study bioabsorbable poly-L-lactide lag screws and metallic screws were compared in the fixation of subcapital femoral neck fractures. PATIENTS AND METHODS: Forty patients with femoral neck fractures were treated by internal fixation using three bioabsorbable self-reinforced poly-L-lactide (SR-PLLA) lag screws of 6.3 mm in diameter and 38 patients using three metallic screws of 7 mm in diameter. In addition, one patient was operated on using two and one using four metallic screws. The patients did not differ in age, body weight or primary dislocation of the fracture. There were six males in the lactide group versus 14 in the metallic fixation group. There were two Garden Stage I, 27 Garden Stage II, nine Garden Stage III, and two Garden Stage IV fractures in both groups. RESULTS: In the Garden I and II fractures there were 5/29 redislocations after SR-PLLA fixation and 8/29 after metallic fixation. In the Garden III fractures there were 4/9 and in the Garden IV fractures 2/2 redislocations in both groups. The ability to walk and the range of movement were better after bioabsorbable fixation. CONCLUSION: Self-reinforced poly-L-lactide lag screws can be used safely to fix subcapital femoral neck fractures in Garden Stage I and II fractures and in younger patients in Garden III fractures.

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PubMed2005

Drug-eluting biodegradable poly-D/L-lactic acid vascular stents: an experimental pilot study.

PURPOSE: To evaluate in vivo a new drug-eluting biodegradable vascular stent with respect to biocompatibility, neointimal hyperplasia formation, and reliability. METHODS: Self-expanding biodegradable poly-96L/4D-lactic acid (PLA) stents with 2 drugs (PLA + dexamethasone [DEX] and PLA + simvastatin [SIM]) and 2 different coatings (PLA + P(D,L)LA and PLA + polycaprolactone [PCL]) were compared with a self-expanding stainless steel Wallstent. The stents were implanted in both common iliac arteries of 8 pigs. Prior to sacrifice at 1 month, angiography was performed to determine patency. Specimens were harvested for quantitative histomorphometry; vascular injury and inflammation scores were assigned to the stented iliac segments. RESULTS: All stented arteries were angiographically patent. The mean luminal diameter (3.05 mm) and area (30.36 mm2) of DEX-eluting PLA stents were decreased compared to other stents (PLA + P(D,L)LA: 3.66 mm and 43.92 mm2; PLA + SIM: 4.21 mm and 56.48 mm2; PLA + PCL: 4.19 mm and 54.64 mm2; Wallstent: 5.01 mm and 81.19 mm2). Wallstents and DEX-eluting PLA stents induced minimal intimal hyperplasia: PLA + DEX: 0.16 mm, PLA + P(D,L)LA: 0.35 mm, PLA + SIM: 0.33 mm, PLA + PCL: 0.29 mm, and Wallstent: 0.18 mm. The vascular injury scores demonstrated only mild vascular trauma for all stents. Only mild to moderate inflammatory reaction was noted around stent struts with a vascular inflammation score. CONCLUSIONS: Biodegradable polymer stents appear to be biocompatible and reliable, causing minimal neointimal hyperplasia. Furthermore, the new biodegradable poly-D/L-lactic acid stent can be used as a local drug delivery vehicle. The DEX-eluting PLA stent reduces neointimal hyperplasia. The findings show a need for further investigation to prove the efficacy and safety of this new biodegradable drug-eluting stent.

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PubMed2005

A biomechanical and histological evaluation of a bioresorbable lumbar interbody fusion cage.

Novel spinal interbody fusion cages made of bioactive and bioresorbable composites by a unique forging process were developed. Previous in vitro study demonstrated that these cages marked excellent biomechanical values. The purpose of the present in vivo study was to evaluate the viability and advantage of this forged composite of uncalcined hydroxyapatite/poly L-Lactide (F-u-HA/PLLA) cage radiographically, biomechanically, and histologically, when compared to conventional autologous iliac bone (AIB) and carbon fiber cage (CFC). Twenty-five mature sheep underwent posterior lumbar interbody fusion at L2-3 level with pedicle screws system made of titanium. Three types of interbody fusion implants were grafted: AIB (n = 7), CFCs (n = 9), F-u-HA/PLLA cages (n = 9). Two types of cages were packed with autologous fragmented cancellous bone harvested locally. All animals were euthanized at 120 days after surgery. The fusion scoring using the coronal view CT scans was designed to three-dimensionally evaluate fusion quality within and around cages. The mean CT scores of three groups were 33.3 points, 35.0 points, and 33.6 points in AIB, CFC, and F-u-HA/PLLA cage groups, respectively (full-score: 56 points). Statistical differences were not detected among the three groups. The mean range of motion values among fused groups had no significant difference under all pure loadings. The range of motion showed strong and significant correlation with the CT fusion scores. Histologic results demonstrated that F-u-HA/PLLA cages contacted with the surrounding bone directly, and CFC was encircled with thick fibrous tissue layers without any sign of inflammation around cages. The fusion quality of fused spinal segment using F-u-HA/PLLA cages was equal to that of AIB or CFCs both radiographically and biomechanically. In the histological observation, biocompatibility of F-u-HA/PLLA cage was obviously superior to CFC. It has been confirmed that the novel bioactive and bioresorbable cages had valuable advantages over existing CFC for use in spinal reconstructive surgery.

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PubMed2004

A comparative study of barrier membranes as graft protectors in the treatment of localized bone defects. An experimental study in a canine model.

Guided bone regeneration is a predictable and well-documented surgical approach for the treatment of deficient alveolar ridges prior to endosseous implant placement. The purpose of this study was to compare a new resorbable membrane (GORE RESOLUT ADAPT Regenerative Membrane, i.e. 67% glycolide (PGA) : 33% trimethyline carbonate (TMC)) with Bio-Gide, a resorbable collagen membrane. Five canines were used in the study. Three saddle-type osseous defects were created bilaterally in edentulous areas of the mandible. The defects were filled with assayed, canine demineralized freeze-dried bone (DFDB) in a thermoplastic gelatin matrix. Using a randomized block design, four sites were covered with PGA : TMC membranes of four different porosities, one site was covered with a collagen membrane and one site consisted of DFDB alone (control). At 3 months, the animals were euthanized and the mandibles were removed en bloc for laboratory processing. A total of 30 sites were reviewed microradiographically and underwent histomorphometric analysis for bone regeneration, soft tissue presence and remaining graft material. All sites exhibited uneventful healing. A significantly higher percentage of bone regeneration was seen in the sites protected by the PGA : TMC membrane. A higher component of soft tissue was visible beneath the collagen membrane as compared with the PGA : TMC membrane. The control sites exhibited noticeable deformation of the regenerated bone secondary to collapse of the overlying periosteum. The authors conclude that the PGA : TMC membrane protected the DFDB-filled defect and allowed a greater amount of bone regeneration than the defect protected by the collagen membrane or the control.

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PubMedDate not supplied

Ex vivo strength comparison of bioabsorbable tendon plates and bioabsorbable suture in a 3-loop pulley pattern for repair of transected flexor tendons from horse cadavers.

OBJECTIVE: To test the failure strength and energy of 2 bioabsorbable implants applied to transected deep digital flexor tendons (DDFT) from adult horses. STUDY DESIGN: Ex vivo biomechanical experiment. SAMPLE POPULATION: Twelve pairs of deep digital flexor tendons harvested from the forelimbs of fresh equine cadavers. METHODS: Poly-L-lactic acid tendon plates were custom manufactured for application to the cylindrical surface of an adult equine deep digital flexor tendon. Twelve pairs of DDFTs were transected 2 cm distal to the insertion of the distal check ligament of the deep digital flexor tendon. One tendon of each pair was randomly selected for repair with a biodegradable plate or a 3-loop pulley method. Size 2 polydioxanone suture was used in both repairs. Repairs were tested in tension to failure, with peak force (PF) and total energy (TE) at repair failure recorded in Newtons (N) and Joules (J), respectively. A paired t-test was used for statistical evaluation with a significant level set at P< or = .05. RESULTS: Mean+/-SD PF for failure of plated tendons (1507.08+/-184.34 N) was significantly greater than for sutured tendons (460.86+/-60.93 N). TE was also significantly greater for failure of plated tendons versus sutured tendons. CONCLUSIONS: Plate fixation of transected cadaver DDFTs appear to have superior immediate failure strength than 3-loop pulley repairs. CLINICAL RELEVANCE: Whereas in vivo testing is required, a bioabsorbable tendon plate may provide initial increased strength to support tendon healing and decrease external coaptation requirements.

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PubMed2005

Alveolar ridge augmentation with a prototype trilayer membrane and various bone grafts: a histomorphometric study in baboons.

Barrier membranes have become a standard treatment option in alveolar ridge augmentation prior to implant placement. However, non-resorbable membranes require secondary surgery and resorbable membranes show an unfavorable degradation profile. The purpose of this study was to evaluate the potential of a slowly biodegradable/bioresorbable prototype trilayer membrane (PTLM) for supporting bone regeneration in alveolar ridge augmentation. Clinically relevant cavities were made 3 months after the extraction of the first and second molars in each jaw of six baboons. Each animal was treated with four different regimens: (1) autogenous bone block (ABB) alone, (2) ABB+PTLM, (3) deproteinized bovine bone mineral (DBBM)+PTLM and (4) no treatment. After 9 months, the baboons were sacrificed and block sections of the augmented area were subjected to histologic and histomorphometric analyses. Newly formed bone areas were determined at a distance of 1, 3, 7 and 10 mm from crestal. The data showed a well-preserved ridge profile at the membrane-protected sites, whereas non-protected bone blocks and control sites underwent severe resorption resulting in knife-edge ridge profiles. Significant differences were found between ABB+PTLM and ABB (P=0.0137-0.0232). DBBM+PTLM also produced a larger bone area compared with ABB alone (P=0.0396-0.0439). No significant difference in bone area was detectable between ABB+PTLM and DBBM+PTLM (P>0.05). The present study supports the use of the slowly biodegradable/bioresorbable PTLM with autografts and DBBM for lateral ridge augmentation in this type of bone defects.

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