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Results for “Absorbable Implants”

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PubMed2004

Drug delivery systems for vitreoretinal diseases.

The eye has an environment that is specific unto itself in terms of pharmacokinetics: the inner and outer blood-retinal barriers separate the retina and the vitreous from the systemic circulation and vitreous body, which physiologically has no cellular components, occupies the vitreous cavity, an inner space of the eye, and reduces practical convection of molecules. Considering this, development of a drug delivery system (DDS) is becoming increasingly important in the treatment of vitreoretinal diseases not only to facilitate drug efficacy but also to attenuate adverse effects. The DDS has three major goals: enhances drug permeation (e.g., iontophoresis and transscleral DDS), controls release of drugs (e.g., microspheres, liposomes, and intraocular implants), and targets drugs (e.g., prodrugs with high molecular weight and immunoconjugates). Comprehensive knowledge of these should lead to development of innovative treatment modalities.

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PubMed2001

Programmable biodegradable implants.

Pulsatile release implants were developed that release substances up to 58 days post implantation. With a cylindrical size of 2 mm diameter and 1.8 mm height the matrices can carry as much as 1 mg of drug and allow even for intracranial implantation into a rodent model. The matrices are made of materials that have been used for parenteral applications in humans before such as surface eroding polyanhydrides and bulk eroding poly(D,L-lactic acid) or poly(D,L-lactic acid-co-glycolic acid). The onset of drug release is controlled by the degradation of bulk eroding polymers which are known to exhibit a certain stability over a defined period of time and which start eroding after they reach a critical degree of degradation. The time of drug release onset was found to depend on the molecular weight and the chemical state of the carboxylic acid end of the polymer chain. For testing the onset of release in vivo a nude mouse model was developed where the release of Evan's blue could be observed visually after subcutaneous application. By combining individual matrices with different release onset, a therapeutic system can be composed that releases drugs after implantation at predetermined time points in a preprogrammed way. Potential applications for such matrices is vaccination and local tumor therapy.

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PubMedDate not supplied

Failure of polymerized lactic acid tacks in shoulder surgery.

The purpose of this study was to evaluate 4 cases in which bioabsorbable polymerized lactic acid tacks failed after arthroscopic shoulder surgery. Four male elite athletes with recurrent shoulder pain were seen a mean of 7.5 months (range, 3-10 months) after initial arthroscopy. Three of the cases involved superior labrum anterior-to-posterior (SLAP) lesion stabilization, and the fourth case was a rotator cuff (RTC) repair. In the three labral repairs, the implant had broken and the unabsorbed fragments were visible with magnetic resonance imaging. The device used in the RTC repair showed no signs of absorption. All 4 patients underwent arthroscopic removal of the polymer tack fragments to alleviate their symptoms, 2 of whom had foreign-body reactions that required synovectomy. On the basis of clinical examination and magnetic resonance imaging, 2 of the SLAP lesions and the RTC tear had healed. The third patient with a SLAP lesion required arthroscopic debridement of a portion of the labrum. The intact RTC implant had backed out of its insertion point. In all 3 labral repairs, the polymerized lactic acid implant experienced a mechanical failure near the head-shaft junction. We theorize that the labral implants failed because of the variable rate of degradation along the shaft of the devices from the intraarticular to intraosseous regions.

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PubMed2002

Transplantation of embryonal spinal cord nerve cells cultured on biodegradable microcarriers followed by low power laser irradiation for the treatment of traumatic paraplegia in rats.

This pilot study examined the effects of composite implants of cultured embryonal nerve cells and laser irradiation on the regeneration and repair of the completely transected spinal cord. Embryonal spinal cord nerve cells dissociated from rat fetuses and cultured on biodegradable microcarriers and embedded in hyaluronic acid were implanted in the completely transected spinal cords of 24 adult rats. For 14 consecutive post-operative days, 15 rats underwent low power laser irradiation (780 nm, 250 mW), 30 min daily. Eleven of the 15 (73%) showed different degrees of active leg movements and gait performance, compared to 4 (44%) of the 9 rats with implantation alone. In a controlgroup of seven rats with spinal cord transection and no transplantation or laser, six (86%) remained completely paralyzed. Three months after transection, implantation and laser irradiation, SSEPs were elicited in 69% of rats (p = 0.0237) compared to 37.5% in the nonirradiated group. The control group had no SSEPs response. Intensive axonal sprouting occurred in the group with implantation and laser. In the control group, the transected area contained proliferating fibroblasts and blood capillaries only. This suggests: 1. These in vitro composite implants are a regenerative and reparative source for reconstructing the transected spinal cord. 2. Post-operative low power laser irradiation enhances axonal sprouting and spinal cord repair.

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PubMed2006

Synthetic nerve guide implants in humans: a comprehensive survey.

OBJECTIVE: Lesions of the peripheral nervous system result in the loss of sensory and motor function and may in addition be accompanied by severe neuropathic syndromes originating from aberrant axonal regrowth. The transplantation of autologous nerve grafts represents the current "gold standard" during reconstructive surgery, despite obvious side effects. Depending on the demands of the lesion site, various donor nerves may be used for grafting (e.g., the sural, saphenous), sacrificing native functions in their target areas. Recently, several synthetic nerve guide implants have been introduced and approved for clinical use to replace autologous transplants. This alternative therapy is based on pioneering studies with experimental nerve guides. METHODS: We present a comprehensive review of all published human studies involving synthetic nerve guides. RESULTS: Data from some 300 patients suggest that for short nerve defects of a few centimeters, resorbable implants provide promising results, whereas a number of late compression syndromes have been documented for nonresorbable implants. CONCLUSIONS: To treat longer defects, further implant development is needed, a goal that could be achieved, for example, by more closely imitating the intact nerve architecture and regulatory cell-cell interactions.

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PubMedDate not supplied

Four-year follow-up of larger-diameter implants placed in fresh extraction sockets using a resorbable membrane or a resorbable alloplastic material.

PURPOSE: The aim of this randomized study was to evaluate and compare the long-term success rates of cylindric, screw-type titanium implants with a larger diameter (5.9 mm) that were placed in fresh extraction sockets in association with resorbable bone substitutes or a resorbable membrane. MATERIALS AND METHODS: Eighty-three partially edentulous adult patients, selected from among those treated in 1997 and 1998 at the San Raffaele Institute in whom 1 or more implants had been placed into fresh posterior mandibular or maxillary sockets, were included in the study. A total of 111 implants were placed, 36 in mandibles and 75 in maxillae. Fifty-six implants were placed in combination with resorbable hydroxyapatite (HA group) and 55 with a resorbable membrane (MR group). Intraoral radiographs and follow-up examinations, including verification of implant stability via the Periotest, were carried out at second-stage surgery 3, 6, 9, and 12 months later; and then annually up to 4 years after placement of the definitive restoration. The radiographic examination was conducted by means of a standardized procedure to verify osseointegration. RESULTS: There was 100% attendance at the follow-up examination after 4 years. At second-stage surgery, which was performed after 4 to 6 months' healing time, none of the implants showed any signs of mobility, peri-implantitis, or bone loss. Two implants failed in the MR group, one at 3 months and one at 9 months after placement; 1 implant failed in the HA group at 4 months after placement. After 4 years, the implant success rate was 97.3% (108 of 111 implants were considered successful). The success rate did not differ significantly between the HA group (98.2%) and the MR group (96.4%). DISCUSSION: The use of larger-diameter implants served to minimize the anatomic discrepancies that would have evolved when substituting a molar with a standard-diameter implant. According to the accepted criteria for success, the 5-year success rate should be at least 85%; therefore both methods may be considered satisfactory. CONCLUSION: Implants placed in combination with a resorbable allogeneic material or with a resorbable membrane provided predictable long-term results when restored with a fixed partial denture.

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PubMed2006

Physical and biological performance of a novel block copolymer nerve guide.

Although the ability to regenerate is evident in the nervous system, lesioned neurites are unable to cross gaps in neuronal pathways. In order to bridge gaps, guiding cues are essential to direct neurite regrowth. To overcome many of the shortcomings of polymer-based nerve guides, we developed a bioresorbable nerve guide composed of a novel trimethylene carbonate-caprolacton block copolymer (TMC-CL). Pore formation was controlled by using special solvent/precipitation media compositions in combination with the pore forming agent poly ethylene glycol (PEG). NMR spectroscopy, shear force-, compression-, and permeation assays were used for conduit characterization. The polymer conduit has a semipermeable wall with submicron pores to allow free metabolite/drug exchange. In order to investigate the principle of temporally controlled expression of therapeutic proteins in nerve guides, Neuro-2a cells were genetically engineered to express the reporter gene product green fluorescent protein (GFP) under the control of the Tet-On system. When these transduced cells were encapsulated in nerve guides, GFP expression could be induced for days by adding the antibiotic tetracycline derivative doxycycline to the nerve guide environment. Furthermore, encapsulated dorsal root ganglia (DRG) produced long neurites in vitro. In subsequent in vivo experiments, nerve guides filled with Schwann cells (SC) were implanted into lesioned spinal cords of adult rats. Regeneration of spinal cord axons into nerve guides was promoted by co-implanted Schwann cells. The data suggest that the novel TMC-CL nerve guides provide a promising tool for neuroregeneration.

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PubMed2005

The natural history of a bioabsorbable interference screw used for anterior cruciate ligament reconstruction with a 4-strand hamstring technique.

PURPOSE: The purpose of this study was to assess radiologically the rate of absorption of the Arthrex poly L-lactide bioabsorbable interference screw (Arthrex, Naples, FL) used in anterior cruciate ligament reconstruction with a 4-strand hamstring technique. TYPE OF STUDY: Case series. METHODS: Eight sequential patients undergoing anterior cruciate ligament reconstruction with a 4-strand hamstring technique were assessed with magnetic resonance imaging (MRI) scans at 1, 2, and 4 years postoperatively. RESULTS: There was no radiologic evidence of absorption of the screw on any of the scans. The MRI appearance remained essentially unchanged from 1 to 4 years with the exception of the presence of a small cyst in the tibial tunnel of one of the patients. No edema was seen associated with the tibial tunnel in any of our patients. CONCLUSIONS: There are several quoted theoretical advantages to using bioabsorbable screws. The rate of absorption is dependent on material, weight, and degree of crystallization. In our series using an amorphous low crystallization poly L-lactide screw, there was no evidence of any progression to absorption 4 years after implantation. This may be because all series quoted to date look at absorption using a bone-patellar tendon-bone graft. LEVEL OF EVIDENCE: Level IV.

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PubMed2005

Fast setting calcium phosphate-chitosan scaffold: mechanical properties and biocompatibility.

Calcium phosphate cement (CPC) sets in situ to form hydroxyapatite and is highly promising for a wide range of clinical applications. However, its low strength limits its use to only non-stress applications, and its lack of macroporosity hinders cell infiltration, bone ingrowth and implant fixation. The aim of this study was to develop strong and macroporous CPC scaffolds by incorporating chitosan and water-soluble mannitol, and to examine the biocompatibility of the new graft with an osteoblast cell line and an enzymatic assay. Two-way ANOVA identified significant effects on mechanical properties from chitosan reinforcement and powder:liquid ratio (p<0.001). The flexural strength of CPC-chitosan composite at a powder:liquid ratio of 2 was (13.6+/-1.2) MPa, which was significantly higher than (3.2+/-0.6) MPa for CPC control without chitosan (Tukey's at 0.95). At a powder:liquid ratio of 3.5, CPC-chitosan had a strength of (25.3+/-2.9) MPa, which was significantly higher than (10.4+/-1.7) MPa for CPC control. The scaffolds possessed total pore volume fractions ranging from 42.0% to 80.0%, and macroporosity up to 65.5%. At total porosities of 52.2-75.2%, the scaffold had strength and elastic modulus values similar to those of sintered porous hydroxyapatite and cancellous bone. Osteoblast mouse cells (MC3T3-E1) were able to adhere, spread and proliferate on CPC-chitosan specimens. The cells, which ranged from about 20 to 50 microm including the cytoplasmic extensions, infiltrated into the 165-271 microm macropores of the scaffold. In summary, substantial reinforcement and macroporosity were imparted to a moldable, fast-setting, biocompatible, and resorbable hydroxyapatite graft. The highly porous scaffold may facilitate bone ingrowth and implant fixation in vivo. In addition, the two to three times increase in strength may help extend the use of CPC to larger repairs in moderately stress-bearing locations.

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PubMed2001

Versatility of biodegradable biopolymers: degradability and an in vivo application.

Biodegradable materials have various important applications in the biomedical field. There are basically two groups of polyesters which have significant importance in this field. These are polylactides and polyhydroxybutyrates. Both groups degrade via hydrolysis with the rates of degradation depending on medium properties such as pH, temperature, solvent and presence of biocatalysts, as well as on chemical compositions. In order for these biomaterials to be suitable for use in load bearing applications without deformation or warping their strengths and their capability to maintain their form must be improved. To insure dimensional stability during degradation and to match modulus and strength to that of bone, introduction of a reinforcing structure for those applications to plate fixation through the creation of an interpenetrating network might be a feasible approach. In this study, poly(lactide-co-glycolide) (PLGA), was the major structural element to be strengthened by a three-dimensional network or "scaffold" of another biodegradable polymer, poly(propylene fumarate) (PPF). PPF would be crosslinked with a biocompatible vinyl monomer, vinylpyrrolidone (VP). Three different approaches were tested to create dimensionally stable bone plates. First, via in situ crosslinking of PPF in the presence of PLGA. Secondly, by blending of precrosslinked PPF with PLGA. Finally, by simultaneous crosslinking and molding of the PLGA, PPF and VP. These were compared against extruded or compression molded PLGA controls. Results showed that compression molding at room temperature followed by crosslinking under pressure at elevated temperature and subsequently by gamma-irradiation appeared to yield the most favorable product as judged by swelling, hardness and flexural strength data. The composition of the implant material, PLGA(3):PPF(1):VP(0.7), appeared to be suitable and formed the compositional and procedural basis for in vivo biocompatibility studies.

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PubMed2001

Tissue engineering of small caliber vascular grafts.

OBJECTIVE: Previous tissue engineering approaches to create small caliber vascular grafts have been limited by the structural and mechanical immaturity of the constructs. This study uses a novel in vitro pulse duplicator system providing a 'biomimetic' environment during tissue formation to yield more mature, implantable vascular grafts. METHODS: Vascular grafts (I.D. 0.5 cm) were fabricated from novel bioabsorbable polymers (polyglycolic-acid/poly-4-hydroxybutyrate) and sequentially seeded with ovine vascular myofibroblasts and endothelial cells. After 4 days static culture, the grafts (n=24) were grown in vitro in a pulse duplicator system (bioreactor) for 4, 7, 14, 21, and 28 days. Controls (n=24) were grown in static culture conditions. Analysis of the neo-tissue included histology, scanning electron microscopy (SEM), and biochemical assays (DNA for cell content, 5-hydroxyproline for collagen). Mechanical testing was performed measuring the burst pressure and the suture retention strength. RESULTS: Histology showed viable, dense tissue in all samples. SEM demonstrated confluent smooth inner surfaces of the grafts exposed to pulsatile flow after 14 days. Biochemical analysis revealed a continuous increase of cell mass and collagen to 21 days compared to significantly lower values in the static controls. The mechanical properties of the pulsed vascular grafts comprised supra-physiological burst strength and suture retention strength appropriate for surgical implantation. CONCLUSIONS: This study demonstrates the feasibility of tissue engineering of viable, surgically implantable small caliber vascular grafts and the important effect of a 'biomimetic' in vitro environment on tissue maturation and extracellular matrix formation.

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PubMed2004

Expression of matrix metalloproteinase-2 and -9 in exudates associated with polydimethyl siloxane and gelatin tubes implanted in mice.

The expression of matrix metalloproteinases (MMPs), MMP-2 and -9, during the inflammatory response to two implanted biomaterials was determined. To illustrate this phenomenon, polydimethyl siloxane (PDMS), weakly crosslinked gelatin, and highly crosslinked gelatin tubes were implanted subcutaneously in mice for up to 3 weeks. Latent MMP-2 (pro-MMP-2) was seen in exudates throughout the experimental period and did not show any apparent changes in time or among the three biomaterials. The expression of MMP-9, however, showed a very different pattern. At days 4 and 8, the predominant form of MMP-9 is pro-MMP-9 (the latent form) and its level is much higher for the PDMS tube than either of the gelatin tubes. The active form of MMP-9, initially low, rose progressively over the 3-week period and reached its peak at week 2 for PDMS and highly crosslinked gelatin and at week 3 for the more degradable, weakly crosslinked gelatin. Data from the histological and cytological analysis also showed that the PDMS tube induced a much stronger cellular response than gelatin tubes, although endotoxin contamination precludes a conclusion related to biomaterial effects. We concluded that MMP-9 is a useful marker of the host inflammatory response to the implanted biomaterials and it may be useful in the assessment of biomaterial biocompatibility. Perhaps more importantly, the consequences of MMPs on matrix remodeling may become of concern in biomaterials used for tissue engineering.

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PubMed2007

Fabrication and mechanical and tissue ingrowth properties of unidirectionally porous hydroxyapatite/collagen composite.

This study investigated the effects of the three-dimensional (3-D) pore structure of a porous hydroxyapatite/collagen (HAp/Col) composite on their mechanical properties and in vivo tissue ingrowth. The unique 3-D pore structure, comprising unidirectionally interconnected pores, was fabricated by the unidirectional growth of ice crystals by using a cooling stage and a subsequent freeze-drying process. The unidirectional pores had a spindle-shaped cross section, and their size gradually increased from the bottom to the upper face. The porous composite showed an elastic property and anisotropic compressive strength for the pore directions. While the strength and modulus parallel to the pore axis were 1.3- and twofold higher than those of the porous composite with spherical pores formed randomly, the strength and modulus perpendicular to the pore axis showed the lowest values. The subcutaneous implantations revealed that when compared with the random pores, the unidirectional pores promote the ingrowth of the surrounding tissues into the pores.

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PubMed2006

Ectopic bone formation in mice associated with a lactic acid/dioxanone/ethylene glycol copolymer-tricalcium phosphate composite with added recombinant human bone morphogenetic protein-2.

A new putty-like material with bone-inducing capacity was made by combining a block copolymer of poly d,l-lactic acid with randomly inserted p-dioxanone and polyethylene glycol (PLA-DX-PEG) and beta-tricalcium phosphate (beta-TCP) powder with added recombinant human bone morphogenetic protein-2 (rhBMP-2). To optimize the material's efficacy for bone formation, we formulated the optimal composition ratio of the respective constituent that gives the greatest osteoinductive efficacy in a mouse model of ectopic bone formation. In this series of studies, we investigated the size of ectopic bone mass induced 3 and 6 weeks after implantation of the materials composed of 30 mg of PLA-DX-PEG with 2 microg of rhBMP-2 and 0, 15, 30, or 60 mg of beta-TCP powder. An additional experiment was designed to investigate how content ratios of beta-TCP powder in 30 mg-putty implants (0%, 16.7%, 33.3%, 50%, 66.7%, 83.3%, or 100%) for a fixed dose (5 microg) of the rhBMP-2 altered the size of the induced ossicle. The results from the first experiment indicated that the bone yields were linearly dependent on the amount of additional beta-TCP powder. In the second experiment, the largest ossicles induced by 5 microg of rhBMP-2 were obtained when the polymer/beta-TCP ratio was 1/2 in mice. The data provide important insights into the fabrication of implants that provide efficacious delivery of rhBMP-2. The new putty-like material may be valuable for repairing or regenerating bone in a clinical setting.

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PubMed2006

A comparative study of 2 implants used to repair inferior orbital wall bony defects: autogenous bone graft versus bioresorbable poly-L/DL-Lactide [P(L/DL)LA 70/30] plate.

PURPOSE: The purpose of this study was to compare our clinical findings on the use of autogenous bone grafts and bioresorbable poly-L/DL-Lactide [P(L/DL)LA 70/30] implants to repair inferior orbital wall defects. PATIENTS AND METHODS: Thirty-nine patients who suffered orbital blow-out fractures with >or=2 cm2 bony defect in the inferior orbital wall took part in the study. Each inferior orbital wall was reconstructed using either an autogenous bone graft or a triangle form plate of P(L/DL)LA 70/30. Computed tomography scans were taken before the operation and at 2 and 36 weeks postoperatively. To describe the distribution of complications and facilitate statistical analysis, we categorized our findings into diplopia, enophthalmos, numbness, gaze restrictions, size of bony defect after treatment, bone growth, and implant resorption. A comparative study was carried out using chi2 test and the Fisher exact test. We considered P < .05 to be statistically significant. RESULTS: The clinical outcome was excellent in 19 of the 24 (79%) cases treated with autogenous bone grafts and in 13 of the 15 (87%) cases treated with P(L/DL)LA 70/30. No statistically significant differences were found between the 2 groups in overall type or number of complications. The most frequent type of complication found in both groups was enophthalmos, with 5 cases (bone graft, 3; P(L/DL)LA plates, 2). Diplopia was the second most frequent type of complication; however, both complications caused no need for the removal of the implants in either group. CONCLUSION: Autogenous bone grafts and P(L/DL)LA 70/30 implant plates do not present statistically significant differences in the parameters studied. Taking into account the availability and the advantages of P(L/DL)LA 70/30 implants when compared with autogenous bone grafts, our results allow us to conclude that there is no compromise regarding successful bridging of orbital floor defects using biodegradable P(L/DL)LA 70/30 osteosyntheses.

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PubMed2004

Pattern of recurrence following local chemotherapy with biodegradable carmustine (BCNU) implants in patients with glioblastoma.

OBJECTIVE: Recently a randomized placebo-controlled phase III trial of biodegradable polymers containing carmustine has demonstrated a significant survival benefit for patients treated with local chemotherapy. A local chemotherapy applied directly to the resection cavity may act directly on residual tumor cells in adjacent brain possibly leading to a local control of the tumor and increased survival. METHODS: We have analyzed the pattern of recurrence using serial MRI studies of 24 patients treated with GLIADEL Wafers or placebo wafers following resection of glioblastomas. RESULTS: Of 24 patients 11 received carmustine wafers and 13 placebo. The age distribution and Karnowsky performance scores of the two populations were not different. However, the median survival (14.7 versus 9.5 months; P = 0.007) and the time to neurological deterioration (12.9 +/- 4.85 vs. 9.4 +/- 2.73 months; P = 0.035) was significantly longer in the treatment group versus the placebo treated control. Preoperative and follow up MRI studies were evaluated in a blinded fashion. Out of 24 patients that entered the analysis 11 showed clearance of all contrast enhancement following resection of glioblastomas. Seventeen tumors progressed locally and 7 showed different patterns of distant failure. Within the carmustine treated group 8 patients showed a local treatment failure with recurrent tumors immediately adjacent to the resection cavity or progression form a residual tumor. Three patients showed a multifocal distant and local pattern of failure after complete or subtotal removal. In no case the local chemotherapy resulted in a distant recurrence only. However, the time to radiographic progression was 165.1 +/- 80.75 days for the GLIADEL Wafer group and 101.9 +/- 43.06 days for the placebo group (P = 0.023). CONCLUSION: In this subgroup analysis of a phase III trial population both the clinical progression and radiological progression were significantly delayed in patients treated with local chemotherapy, resulting in an increased survival time. Local chemotherapy with carmustine containing wafer implants did not result in an altered pattern of recurrence and did not promote multifocal patterns of recurrence.

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PubMed2005

Bridging small-gap peripheral nerve defects using biodegradable chitin conduits with cultured schwann and bone marrow stromal cells in rats.

Nerve regeneration requires not only an autologous, allogenous, or biodegradable scaffolding, but additional interactions with regeneration-promoting Schwann cells. Considering the pluripotency of bone marrow stromal cells into different lineages, the authors compared biodegradable conduits with the application of cultured Schwann cells and bone marrow stromal cells in a rat sciatic injury model. Simple conduit bridging served as controls. Electrophysiologic evaluation and histologic morphometrical analysis were performed after 6 weeks; both groups with cultured cells showed a statistically significantly higher number of axons, more well-shaped remyelinated axons, and an advance in clinical functional recovery (SFI) than the simple conduit-bridging group. Confocal microscopy found that bone marrow stromal cells adopted the Schwann-cell phenotype, expressing S100 protein. Considering the ease of aspiration and greater resource of bone marrow stromal cells, the implantation of a biodegradable conduit with cultured bone marrow stromal cells was capable of presenting an alternative to conduits with Schwann cells for bridging nerve defects.

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PubMed2002

Evaluation of peripheral nerve regeneration across an 80-mm gap using a polyglycolic acid (PGA)--collagen nerve conduit filled with laminin-soaked collagen sponge in dogs.

We evaluated peripheral nerve regeneration using a novel artificial nerve conduit. The conduit was made of a polyglycolic acid(PGA) - collagen tube filled with laminin- soaked collagen sponge. We implanted this nerve conduit across an 80mm gap in the peroneal nerve of dogs. Histological observation 12 months after implantation showed numerous unmyelinated and myelinated nerve fibershad regenerated beyond the gap. Neurofilaments were widely observed immunohistochemically in the regenerated nerve segments. These findings indicated that newly regenerated axons had extended across the gap and connected into the distal nerve segments. Compound muscle action potentials(CMAPs) and somatosensory evoked potentials (SEPs) were recorded in all dogs. At 12 months, the CMAPs indicated complete recovery, while the SEPs showed incomplete but substantial recovery. Walking patterns had returned to near-normal 12 months after implantation. Use of this nerve conduit can lead to peripheral nerve elongation and favorable functional recovery across a wider nerve gap.

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