Cadaveric Pigs Research Articles

Characterization of Induced Current Density During Transcorneal Electrical Stimulation to Promote Neuroprotection in the Degenerating Retina.

Transcorneal electrical stimulation (TES) is a promising approach to delay retinal degeneration by inducing extracellular electric field-driven neuroprotective effects within photoreceptors. Although achieving precise electric field control is feasible in vitro, characterizing these fields becomes intricate and largely unexplored in vivo due to uneven distribution in the heterogeneous body. In this paper, we investigate and characterize electric fields within the retina during TES to assess the potential for therapeutic approaches Methods: We developed a computational model of a rat's head, enabling us to generate predictive simulations of the voltage and current density induced in the retina. Subsequently, an in vivo experimental setup involving Royal College of Surgeon (RCS) rats was implemented to measure the voltage across the retina using identical electrode configurations as employed in the simulations. A stimulation amplitude of 0.2-0.3 mA may be necessary during TES in rats to induce a current density of at least 20 A/m2 in the retina, which is the lower limit for triggering neuroprotective effects according to culture studies on neural cells. Measurement taken from cadaveric pigs' eyes revealed that a stimulation amplitude of 1 mA is necessary for achieving the same current density. The computational modeling approach presented in this study was validated with experimental data and can be leveraged for predictive simulations to optimize the electrode design and stimulation parameters of TES. Once validated, the flexibility and low research cost of computational models are valuable in optimization studies where testing on live subjects is not feasible.

Favorable clinical application for segmental bronchial closure based on experiment results.

We previously reported the clinical application of powered vascular staple (PVS) for closure of subsegmental or segmental bronchus (SSB). This study aimed to measure breakdown pressure in experiment and to investigate bronchopleural fistula (BPF) after thoracoscopic segmentectomy (TS). Part 1: a total of 30 cadaveric pigs were used, and bronchi were categorized into the following four groups: small [S, bronchial outer diameter (BOD) of 4-8 mm, n=8], medium (M, 9-10 mm, n=9), and large (L, >10 mm, n=13). We additionally added a single additional suture to compensate for weak sites with large BOD (group R, n=6). The pressure was slowly increased, and stump breakdown was observed. Part 2: we investigated the morbidity of BPF formation at follow-up of at least 6 months in a total of 217 patients. Part 1: the mean leak pressure was the highest in M, followed by groups S, R and L'. However, the significant difference was not found between S and R. Part 2: no BPF was observed, clinically. Based on experimental results and clinical experience, the proper selection of PVS should contribute to the safety, feasibility, and success as SSB closure.

Perforator Dissection Simulation: A High-Fidelity Five-Flap Porcine Training Model.

Perforator dissection can be technically demanding with a steep learning curve. Inadvertent perforator damage during dissection can be minimized with practice and familiarity with tissue-handling techniques unique to perforator dissection. There currently lacks a simulation model that mimics the human perforator in size and course. We present a porcine training model with five consistent perforator flaps per side that can be readily harvested and is a reproducible simulation model. Five fresh cadaveric pigs were used in this study to evaluate the feasibility and location of the perforators. Ten perforators were dissected out in each pig (five per side) by the same surgeon. The length of perforator was measured and intramuscular route was noted. The ease of dissection was graded, and its similarity to actual surgery was graded as well. Five consistent perforators were identified across each side of five fresh cadaveric pigs. The perforators were located, namely in the neck, anterior flank, posterior flank, rectus and hindlimb. They were fasciocutaneous and had an intramuscular course of each (average 2.5cm length). The perforators were found to be on each side of the pig, giving ten perforators for dissection practice in total. The five perforators named in this porcine model are easily replicated and can be performed for perforator dissection simulation and practice.

Ultrasound-guided spinal stereotactic system for intraspinal implants.

OBJECTIVE The overall goal of this study was to develop an image-guided spinal stereotactic setup for intraoperative intraspinal microstimulation (ISMS). System requirements were as follows: 1) ability to place implants in various segments of the spinal cord, targeting the gray matter with a < 0.5-mm error; 2) modularity; and 3) compatibility with standard surgical tools. METHODS A spine-mounted stereotactic system was developed, optimized, and tested in pigs. The system consists of a platform supporting a micromanipulator with 6 degrees of freedom. It is modular and flexible in design and can be applied to various regions of the spine. An intraoperative ultrasound imaging technique was also developed and assessed for guidance of electrode alignment prior to and after electrode insertion into the spinal cord. Performance of the ultrasound-guided stereotactic system was assessed both in pigs (1 live and 6 fresh cadaveric pigs) and on the bench using four gelatin-based surrogate spinal cords. Pig experiments were conducted to evaluate the performance of ultrasound imaging in aligning the electrode trajectory using three techniques and under two conditions. Benchtop experiments were performed to assess the performance of ultrasound-guided targeting more directly. These experiments were used to quantify the accuracy of electrode alignment as well as assess the accuracy of the implantation depth and the error in spatial targeting within the gray matter of the spinal cord. As proof of concept, an intraoperative ISMS experiment was also conducted in an additional live pig using the stereotactic system, and the resulting movements and electromyographic responses were recorded. RESULTS The stereotactic system was quick to set up (< 10 minutes) and provided sufficient stability and range of motion to reach the ISMS targets reliably in the pigs. Transverse ultrasound images with the probe angled at 25°-45° provided acceptable contrast between the gray and white matter of the spinal cord. In pigs, the largest electrode alignment error using ultrasound guidance, relative to the minor axis of the spinal cord, was ≤ 3.57° (upper bound of the 95% confidence interval). The targeting error with ultrasound guidance in bench testing for targets 4 mm deep into the surrogate spinal cords was 0.2 ± 0.02 mm (mean ± standard deviation). CONCLUSIONS The authors developed and evaluated an ultrasound-guided spinal stereotactic system for precise insertion of intraspinal implants. The system is compatible with existing spinal instrumentation. Intraoperative ultrasound imaging of the spinal cord aids in alignment of the implants before insertion and provides feedback during and after implantation. The ability of ultrasound imaging to distinguish between spinal cord gray and white matter also improves confidence in the localization of targets within the gray matter. This system would be suitable for accurate guidance of intraspinal electrodes and drug or cell injections.

Abstract: Vascular Anatomy of Facial Units for Vascularized Composite Tissue Transplantation Design in a Large Animal Model: An in-Vivo and Radiological Study

INTRODUCTION: A large animal model for composite face transplantation is necessary to better understand the immunologic processes and nerve regeneration. Current porcine models of facial transplantation fail to include all major branches of the facial nerve, and have not demonstrated long-term survival.1,2 A better understanding and detailed evaluation of vascular anatomy and microvascular territories in facial subunits and bone can help effectively develop a reliable porcine composite tissue flap model for experimental reconstructive or transplantation studies. METHODS: Eleven 10kg domestic pigs were used for in-vivo studies. Vascular anatomy was assessed by Intra-operative anatomical dissections of 11 hemi-facial composite tissue flaps including the auricle. In addition Computed Tomographic Angiography (CTA) and Laser-assisted Indocyanine Green Fluorescence Angiography (LA-ICGFA) were used to assess vascular architecture preoperatively and flap perfusion. In addition, 8 cadaveric pigs were used for selective angiography of branches of the external carotid artery using a barium sulfate and latex mixture to provide detailed qualitative and quantitative analysis of the vascular territories using ultra-high resolution 3D CTA followed by a detailed anatomical dissection. Perforator distributions in facial subunits and the relationship of vascular territories to the facial nerve branches were documented. RESULTS: A composite tissue flap of the hemi-face including the auricle was elevated and auto-transplanted in eleven 2 months old domestic pigs. Three pigs underwent preoperative CTA. We demonstrated two principal vessels supplying the hemifacial tissues: Internal maxillary artery (IMA) and superficial temporal artery (STA), with less significant contribution from the facial artery. Use of 3D volume rendering of the CTAs and the anatomical dissections demonstrated the vasculature and potential angiosomes of dominant and minor branches from the external carotid artery. We have been able to categorize facial subunit vascularity to delineate safe vascular territories for flap design in facial transplantation or reconstructive surgery. CONCLUSION: We describe a new swine facial transplantation model with successful outcomes and reliable vascularity confirmed with anatomic, in-vivo CTA studies. Novel detailed vascular injection studies provide understanding of 3D vascular territories paramount to flap design, therefore enabling successful long-term modeling of hemi-facial composite tissue transplantation. DISCLOSURE/FINANCIAL SUPPORT:None of the authors has a financial interest in any of the products, devices, or drugs mentioned in this manuscript. REFERENCES: 1. Kuo, Y. R., Shih, H. S., Lin, C. C., et al. (2009). Swine hemi-facial composite tissue allotransplantation: a model to study immune rejection. Journal of Surgical Research, 153(2), 268–273. 2. Gordon, C. R., Murphy, R. J., Coon, D., et al. (2014). Preliminary development of a workstation for craniomaxillofacial surgical procedures: introducing a computer-assisted planning and execution system. The Journal of craniofacial surgery, 25(1), 273.

Tu1401 Prospective Evaluation of Endoscopic Submucosal Dissection Training Models: Which Is Better?

Endoscopic submucosal dissection (ESD) has a steep learning phase, during which major complications are common. For this reason, ESD is best learned in the safety of a training model. To evaluate the optimal training model, we compared ESD in explanted porcine stomachs, recently cadaveric pigs, and human cadavers, models commonly available for surgical training.

Laparoscopic Surgery for Kidney Orthotopic Transplant in the Pig Model

Laparoscopic surgery has rapidly expanded in surgical practice with well-accepted benefits of minimal incision, less analgesia, better cosmetics, and quick recovery. The surgical technique for kidney transplantation has remained unchanged since the first successful kidney transplant in the 1950s. Over the past decade, there were only a few case reports of kidney transplantation by laparoscopic or robotic surgery. Therefore, the aim of this study is to develop a laparoscopic technique for kidney transplantation at the region of the native kidney. After initial development of the laparoscopic technique for kidney transplant in cadaveric pigs, 5 live pigs (Sus scrofa, weighing 45-50 kg) underwent laparoscopic kidney transplant under general anesthesia. First, laparoscopic donor nephrectomy was performed, and then the kidney was perfused and preserved with cold Ross solution. The orthotopic auto-transplant was subsequently performed using the laparoscopic technique. The blood flow of the kidney graft was assessed using Doppler ultrasonography, and urine output was monitored. The laparoscopic kidney transplant was successful in 4 live pigs. Immediate urine output was observed in 3 pigs. The blood flow in the kidney was adequate, as determined using Doppler ultrasonography. It has been shown that laparoscopic kidney orthotopic transplant is feasible and safe in the pig model. Immediate kidney graft function can be achieved. A further study will be considered to identify the potential surgical morbidity and mortality after recovery in a pig model before translating the technique to clinical human kidney transplantation.

Disc Volume Reduction with Percutaneous Nucleoplasty in an Animal Model

Study DesignWe assessed volume following nucleoplasty disc decompression in lower lumbar spines from cadaveric pigs using 7.1Tesla magnetic resonance imaging (MRI).PurposeTo investigate coblation-induced volume reductions as a possible mechanism underlying nucleoplasty.MethodsWe assessed volume following nucleoplastic disc decompression in pig spines using 7.1-Tesla MRI. Volumetry was performed in lumbar discs of 21 postmortem pigs. A preoperative image data set was obtained, volume was determined, and either disc decompression or placebo therapy was performed in a randomized manner. Group 1 (nucleoplasty group) was treated according to the usual nucleoplasty protocol with coblation current applied to 6 channels for 10 seconds each in an application field of 360°; in group 2 (placebo group) the same procedure was performed but without coblation current. After the procedure, a second data set was generated and volumes calculated and matched with the preoperative measurements in a blinded manner. To analyze the effectiveness of nucleoplasty, volumes between treatment and placebo groups were compared.ResultsThe average preoperative nucleus volume was 0.994 ml (SD: 0.298 ml). In the nucleoplasty group (n = 21) volume was reduced by an average of 0.087 ml (SD: 0.110 ml) or 7.14%. In the placebo group (n = 21) volume was increased by an average of 0.075 ml (SD: 0.075 ml) or 8.94%. The average nucleoplasty-induced volume reduction was 0.162 ml (SD: 0.124 ml) or 16.08%. Volume reduction in lumbar discs was significant in favor of the nucleoplasty group (p<0.0001).ConclusionsOur study demonstrates that nucleoplasty has a volume-reducing effect on the lumbar nucleus pulposus in an animal model. Furthermore, we show the volume reduction to be a coblation effect of nucleoplasty in porcine discs.

Development of an Intrabiliary MR Imaging-monitored Local Agent Delivery Technique: A Feasibility Study in Pigs

To investigate the feasibility of using magnetic resonance (MR) imaging to monitor intrabiliary delivery of motexafin gadolinium (MGd) into pig common bile duct (CBD) walls. Animal studies were approved by the Institutional Animal Care and Use Committee. Initially, human cholangiocarcinoma cells were treated with various concentrations of MGd, a compound serving as a T1-weighted MR imaging contrast agent, chemotherapy drug, and cell marker. These cells were then examined by means of confocal microscopy to confirm the intracellular uptake of MGd. In addition, an MGd/trypan blue mixture was locally infused into CBD walls of six cadaveric pigs using a microporous balloon catheter. CBDs of six pigs were infused with saline to serve as controls. Ex vivo T1-weighted MR imaging of these CBDs was performed. For in vivo technical validation, the microporous balloon catheter was placed in the CBD by means of a transcholecytic access to deliver MGd/trypan blue into CBD walls of six living pigs. T1-weighted images were obtained with both a surface coil and an intrabiliary MR imaging guidewire, and contrast-to-noise ratios of CBD walls before and after MGd/trypan blue infusions were compared in the two groups by means of paired t test, with subsequent histologic analysis to confirm the penetration and distribution of the MGd/trypan blue agent into CBD walls. In vitro experiments confirmed uptake of MGd by human cholangiocarcinoma cells. The ex vivo experiments demonstrated the penetration of MGd/trypan blue into the CBD walls. The in vivo experiment confirmed the uptake of MGd/trypan blue, showing an increased contrast-to-noise ratio for the CBD after administration of the mixture, compared with images obtained prior to MGd/trypan blue administration (11.6 ± 4.2 [standard deviation] vs 5.7 ± 2.8; P = .04). Histologic results depicted the blue dye stains and red fluorescence of MGd in CBD walls, confirming the imaging findings. It is feasible to use MR imaging to monitor the penetration of locally delivered MGd into pig CBD walls.

Structural health monitoring to detect the presence, location and magnitude of structural damage in cadaveric porcine spines

Structural health monitoring has been used successfully to identify defects in civil infrastructure and aerospace applications. Given that the majority of low back pain is thought to be mechanical in nature, our objective was to determine if structural health monitoring techniques could be employed successfully to identify the presence, location and magnitude of structural alterations within the spine. In six eviscerated cadaveric pigs, bone screws were drilled into the anterior bodies of L1-L5 and tri-axial accelerometers fixed to each spinous process. Vibration was then applied to the L3 spinous and frequency response functions obtained from each sensor axis before and after specific alterations of spinal structure. These alterations were produced at four unique locations and included (1) use of a cable tie to link anterior bone pins together and (2) progressive disc sectioning. Eighty percent of all data were used to train a neural network while the remaining data were used to test the network's ability to distinguish between structural states. The presence, location and magnitude of structural change within the spine was identified correctly in 5030 5040 possible neural network decisions. The diagnostic sensitivity and specificity of this technique ranged from 0.994 to 1.000. These results indicate that there is sufficient information embedded in frequency response data to identify the presence, location and magnitude of specific structural changes in the spine. If these techniques can be evolved for human use, structural health monitoring may provide a new approach toward understanding the underlying relations between spinal structure and function.

The feasibility of vibration as a tool to assess spinal integrity

As the majority of back pain is thought to be mechanical in origin, quantitative tests designed to assess spinal mechanics may provide information about its etiology and treatment. This paper describes the application of structural vibration testing in the spine, its reliability and ability to discriminate between different structural states. In each of five cadaveric pigs, tri-axial accelerometers were fixed to the spinouses of L1–5 and short-duration vibrations (0–2000 Hz) were applied to the L3 spinous exclusively. The frequency response function (FRF) of each sensor axis was calculated and the process repeated. Additional FRF data were obtained after the creation of multiple structural alterations including joining of adjacent vertebrae and scalpel transections of each lumbar disc. To assess the reliability of structural vibration testing, the intra-class correlation coefficient was calculated for FRFs obtained from each structural state in each specimen. To determine if structural vibration testing could distinguish between different structural states, correlation coefficients were calculated between FRFs from each structural state and a baseline condition. Most intra-class correlation coefficients ( 37 40 ) were in the excellent range (>0.75), while FRF data from each structural state were found to be significantly different from that of the baseline state ( p<0.05). These results indicate that structural vibration testing can be used to obtain reliable FRFs that are sensitive to alterations in the spine's structure. In the future, we hope to refine this technique to obtain specific diagnoses of, and/or assess therapies for, common spinal disorders.

Cochlear implant integrity after adenoidectomy with Coblation and monopolar electrosurgery

Purpose Conventional electrosurgical adenoidectomy has been deemed contraindicated in subjects with cochlear implants (CIs) because of risk to the CI and the auditory neurons. No published studies have evaluated the safety of electrosurgical adenoidectomy techniques with CIs. The goal of this study was to compare the impact of monopolar electrosurgery and Coblation radiofrequency bipolar electrosurgery on CI integrity. Methods Twelve fresh, cadaveric pigs received unilateral CIs, then the nasopharynx was treated for 15 to 30 minutes with continuous monopolar electrosurgery or Coblation. CIs were tested by the manufacturer for device integrity before and after treatment. Results Integrity was maintained in all CIs treated with either monopolar or Coblation electrosurgery. Conclusions Although the safety of electrosurgical adenoidectomy after CI placement remains unproven, these observations suggest that judicious use of conventional monopolar and Coblation electrosurgery in adenoidectomy does not convey a serious risk to CI integrity. Theoretical considerations favor the use of Coblation over monopolar electrosurgery in CI recipients.