Multiple sessions of therapeutic electrical stimulation using implantable thin-film wireless nerve stimulators improve functional recovery after sciatic nerve isograft repair.

INTRODUCTION/AIMS: Although therapeutic electrical stimulation (TES) of injured peripheral nerve promotes axon regeneration and functional recovery, clinical applications of this therapy are limited to the intraoperative timeframe. Implantable, thin-film wireless nerve stimulators offer a potential solution to this problem by enabling delivery of electrical stimuli to an injured nerve over a period of several days post-surgery. The aim of this study was to determine the optimal time course of stimulation for maximizing functional recovery in a rat sciatic nerve isograft repair model. METHODS: Adult male Lewis rats underwent thin-film wireless nerve stimulator implantation following sciatic nerve transection and 40 mm nerve isograft repair. Immediately after surgery, animals began a daily regimen of TES for up to 12 consecutive days. Functional recovery was assessed by compound muscle action potential (CMAP), evoked muscle force, wet muscle mass, and axon counting. RESULTS: Serial CMAP measurements increased in amplitude over the course of the study, yet no significant difference between cohorts for serial or terminal CMAPs was observed. Axon counts and wet muscle mass measurements were greatest in the 6-day stimulation group, which correlated with a significant increase in evoked muscle force for the 6-day stimulation group at the terminal time point. DISCUSSION: Six daily sessions of TES were found to be most effective for augmenting functional recovery compared to other time courses of stimulation. Future studies should incorporate additional subjects and track axonal sprouting or measure neurotrophin levels during the therapeutic window to further elucidate the mechanisms behind, and ideal amount of, TES.

Intramuscular Microvascular Flow Sensing for Flap Monitoring in a Porcine Model of Arterial and Venous Occlusion.

BACKGROUND: Commercially available near infrared spectroscopy devices for continuous free flap tissue oxygenation (StO2) monitoring can only be used on flaps with a cutaneous component. Additionally, differences in skin quality and pigmentation may alter StO2 measurements. Here, we present a novel implantable heat convection probe that measures microvascular blood flow for peripheral monitoring of free flaps, and is not subject to the same issues that limit the clinical utility of near-infrared spectroscopy. METHODS: The intratissue microvascular flow-sensing device includes a resistive heater, 4 thermistors, a small battery, and a Bluetooth chip, which allows connection to a smart device. Convection of applied heat is measured and mathematically transformed into a measurement of blood flow velocity. This was tested alongside Vioptix T.Ox in a porcine rectus abdominis myocutaneous flap model of arterial and venous occlusion. After flap elevation, the thermal device was deployed intramuscularly, and the cutaneous T.Ox device was applied. Acland clamps were alternately applied to the flap artery and veins to achieve 15 minutes periods of flap ischemia and congestion with a 15 minutes intervening recovery period. In total, five devices were tested in three flaps in three separate pigs over 16 vaso-occlusive events. RESULTS: Flow measurements were responsive to both ischemia and congestion, and returned to baseline during recovery periods. Flow measurements corresponded closely with measured StO2. Cross-correlation at zero lag showed agreement between these two sensing modalities. Two novel devices tested simultaneously on the same flap showed only minor variations in flow measurements. CONCLUSION: This novel probe is capable of detecting changes in tissue microcirculatory blood flow. This device performed well in a swine model of flap ischemia and congestion, and shows promise as a potentially useful clinical tool. Future studies will investigate performance in fasciocutaneous flaps and characterize longevity of the device over a period of several days.

Intramuscular Near-Infrared Spectroscopy for Muscle Flap Monitoring in a Porcine Model.

BACKGROUND: Current near-infrared spectroscopy (NIRS)-based systems for continuous flap monitoring are limited to flaps which carry a cutaneous paddle. As such, this useful and reliable technology has not previously been applicable to muscle-only free flaps where other modalities with substantial limitations continue to be utilized. METHODS: We present the first NIRS probe which allows continuous monitoring of local tissue oxygen saturation (StO2) directly within the substance of muscle tissue. This probe is flexible, subcentimeter in scale, waterproof, biocompatible, and is fitted with resorbable barbs which facilitate temporary autostabilization followed by easy atraumatic removal. This novel device was compared with a ViOptix T.Ox monitor in a porcine rectus abdominus myocutaneous flap model of arterial and venous occlusions. During these experiments, the T.Ox device was affixed to the skin paddle, while the novel probe was within the muscle component of the same flap. RESULTS: The intramuscular NIRS device and skin-mounted ViOptix T.Ox devices produced very similar StO2 tracings throughout the vascular clamping events, with obvious and parallel changes occurring upon vascular clamping and release. The normalized cross-correlation at zero lag describing correspondence between the novel intramuscular NIRS and T.Ox devices was >0.99. CONCLUSION: This novel intramuscular NIRS probe offers continuous monitoring of oxygen saturation within muscle flaps. This experiment demonstrates the potential suitability of this intramuscular NIRS probe for the task of muscle-only free flap monitoring, where NIRS has not previously been applicable. Testing in the clinical environment is necessary to assess durability and reliability.

A Wireless Near-Infrared Spectroscopy Device for Flap Monitoring: Proof of Concept in a Porcine Musculocutaneous Flap Model.

BACKGROUND: Current near-infrared spectroscopy (NIRS)-based systems for continuous flap monitoring are highly sensitive for detecting malperfusion. However, the clinical utility and user experience are limited by the wired connection between the sensor and bedside console. This wire leads to instability of the flap-sensor interface and may cause false alarms. METHODS: We present a novel wearable wireless NIRS sensor for continuous fasciocutaneous free flap monitoring. This waterproof silicone-encapsulated Bluetooth-enabled device contains two light-emitting diodes and two photodetectors in addition to a battery sufficient for 5 days of uninterrupted function. This novel device was compared with a ViOptix T.Ox monitor in a porcine rectus abdominus myocutaneous flap model of arterial and venous occlusions. RESULTS: Devices were tested in four flaps using three animals. Both devices produced very similar tissue oxygen saturation (StO2) tracings throughout the vascular clamping events, with obvious and parallel changes occurring on arterial clamping, arterial release, venous clamping, and venous release. Small interdevice variations in absolute StO2 value readings and magnitude of change were observed. The normalized cross-correlation at zero lag describing correspondence between the novel NIRS and T.Ox devices was >0.99 in each trial. CONCLUSION: The wireless NIRS flap monitor is capable of detecting StO2 changes resultant from arterial vascular occlusive events. In this porcine flap model, the functionality of this novel sensor closely mirrored that of the T.Ox wired platform. This device is waterproof, highly adhesive, skin conforming, and has sufficient battery life to function for 5 days. Clinical testing is necessary to determine if this wireless functionality translates into fewer false-positive alarms and a better user experience.

What is Normal? Neuromuscular junction reinnervation after nerve injury.

INTRODUCTION: In this study we present a reproducible technique to assess motor recovery after nerve injury via neuromuscular junction (NMJ) immunostaining and electrodiagnostic testing. METHODS: Wild-type mice underwent sciatic nerve transection with repair. Hindlimb muscles were collected for microscopy up to 30 weeks after injury. Immunostaining was used to assess axons (NF200), Schwann cells (S100), and motor endplates (α-bungarotoxin). Compound motor action potential (CMAP) amplitude was used to assess tibialis anterior (TA) function. RESULTS: One week after injury, nearly all (98.0%) endplates were denervated. At 8 weeks, endplates were either partially (28.3%) or fully (71.7%) reinnervated. At 16 weeks, NMJ reinnervation reached 87.3%. CMAP amplitude was 83% of naive mice at 16 weeks and correlated with percentage of fully reinnervated NMJs. Morphological differences were noted between injured and noninjured NMJs. DISCUSSION: We present a reproducible method for evaluating NMJ reinnervation. Electrodiagnostic data summarize NMJ recovery. Characterization of wild-type reinnervation provides important data for consideration in experimental design and interpretation.

Comparison of the Ottawa Surgical Competency Operating Room Evaluation (O-SCORE) to a Single-Item Performance Score.

Construct: We compared a single-item performance score with the Ottawa Surgical Competency Operating Room Evaluation (O-SCORE) for their ability in assessing surgical competency. BACKGROUND: Surgical programs are adopting competency-based frameworks. The adoption of these frameworks for assessment requires tools that produce accurate and valid assessments of knowledge and technical performance. An assessment tool that is quick to complete could improve feasibility, reduce delays, and result in a higher volume of assessments of learners. Previous work demonstrated that the 9-item O-SCORE can produce valid results; the goal of this study was to determine if a single-item performance rating (Is candidate competent to independently complete procedure: yes or no) completed at a separate viewing would correlate to the O-SCORE, thus increasing feasibility of procedural competence assessment. APPROACH: Nineteen residents and 2 staff orthopedic surgeons from the University of Ottawa volunteered for a 2-part OSCE-style station including a written questionnaire and videotaped simulated open reduction and internal fixation midshaft radius fracture. Each performance was rated independently by 3 orthopedic surgeons using a single-item performance score (Time 1). The performances were assessed again 6 weeks later by the 3 raters using the O-SCORE (Time 2). Correlation between the single-item performance score and the O-SCORE were evaluated. RESULTS: Three orthopedic surgeons completed 21 ratings each resulting in 63 orthopedic ratings. There was a high level of correlation and agreement between the single-item performance score at Time 1 and Time 2 (κ correlation =0.72-1.00; p < .001; percentage agreement =90%-100%). The reliability of the O-SCORE at Time 2 with three raters was 0.83 and the internal consistency was 0.89. There was a tendency for each rater to assign more yes responses to the more senior trainees. CONCLUSIONS: A single-item performance score correlated highly with the O-SCORE in an orthopedic setting. A single-item score could be used to supplement a multi-item score with similar results in orthopedics. There is still benefit in completing multi-item scores such as the O-SCORE evaluations to guide specific areas of improvement and direct feedback.

Serial assessment of functional recovery following nerve injury using implantable thin-film wireless nerve stimulators.

INTRODUCTION: Comprehensive assessment of the time course of functional recovery following peripheral nerve repair is critical for surgical management of peripheral nerve injuries. This study describes the design and implementation of a novel implantable wireless nerve stimulator capable of repeatedly interfacing peripheral nerve tissue and providing serial evaluation of functional recovery postoperatively. METHODS: Thin-film wireless implants were fabricated and subcutaneously implanted into Lewis rats. Wireless implants were used to serially stimulate rat sciatic nerve and assess functional recovery over 3 months following various nerve injuries. RESULTS: Wireless stimulators demonstrated consistent performances over 3 months in vivo and successfully facilitated serial assessment of nerve and muscle function following nerve crush and nerve transection injuries. CONCLUSIONS: This study highlights the ability of implantable wireless nerve stimulators to provide a unique view into the time course of functional recovery in multiple motor targets. Muscle Nerve 54: 1114-1119, 2016.

Continued Validation of the O-SCORE (Ottawa Surgical Competency Operating Room Evaluation): Use in the Simulated Environment.

UNLABELLED: CONSTRUCT: The Ottawa Surgical Competency Operating Room Evaluation (O-SCORE) is a 9-item surgical evaluation tool designed to assess technical competence in surgical trainees using behavioral anchors. BACKGROUND: The initial development of the O-SCORE produced evidence for valid results. Further work is required to determine if the use of a single surgeon or an unblinded rater introduces bias. In addition, the relationship of the O-SCORE to other currently used technical assessment tools should be explored to provide validity evidence related to the relationship to other measures. We have designed this project to provide continued validity evidence for the O-SCORE related to these two issues. APPROACH: Nineteen residents and 2 staff Orthopedic Surgeons from the University of Ottawa volunteered to participate in a 2-part OSCE style station. Participants completed a written questionnaire followed by a videotaped 10-minute simulated open reduction and internal fixation of a midshaft radius fracture. Videos were rated individually by 2 blinded staff orthopedic surgeons using an Objective Structured Assessment of Technical Skills (OSATS) global rating scale, an OSATS checklist, and the O-SCORE in random order. RESULTS: O-SCORE results appeared sensitive to surgical training level even when raters were blinded. In addition, strong agreement between two independent observers using the O-SCORE suggests that the measure captures a performance easily recognized by surgical observers. Ratings on the O-SCORE also were strongly associated with global ratings on the currently most validated technical evaluation tool (OSATS). Collectively, these results suggest that the O-SCORE generates accurate, reproducible, and meaningful results when used in a randomized and blinded fashion, providing continued validity evidence for using this tool to evaluate surgical trainee competence. CONCLUSIONS: The O-SCORE was able to differentiate surgical trainee level using blinded raters providing further evidence of validity for the O-SCORE. There was strong agreement between two independent observers using the O-SCORE. Ratings on the O-SCORE also demonstrated equivalence to scores on the most validated technical evaluation tool (OSATS). These results suggest that the O-SCORE demonstrates accurate and reproducible results when used in a randomized and blinded fashion providing continued validity evidence for this tool in the evaluation of surgical competence in the trainees.

Schwann cells seeded in acellular nerve grafts improve functional recovery.

INTRODUCTION: This study evaluated whether Schwann cells (SCs) from different nerve sources transplanted into cold-preserved acellular nerve grafts (CP-ANGs) would improve functional regeneration compared with nerve isografts. METHODS: SCs isolated and expanded from motor and sensory branches of rat femoral and sciatic nerves were seeded into 14mm CP-ANGs. Growth factor expression, axonal regeneration, and functional recovery were evaluated in a 14-mm rat sciatic injury model and compared with isografts. RESULTS: At 14 days, motor or sensory-derived SCs increased expression of growth factors in CP-ANGs versus isografts. After 42 days, histomorphometric analysis found CP-ANGs with SCs and isografts had similar numbers of regenerating nerve fibers. At 84 days, muscle force generation was similar for CP-ANGs with SCs and isografts. SC source did not affect nerve fiber counts or muscle force generation. CONCLUSIONS: SCs transplanted into CP-ANGs increase functional regeneration to isograft levels; however SC nerve source did not have an effect.

Synergistic clinical application of synthetic electrospun fiber wound matrix in the management of a complex traumatic wound: degloving left groin and thigh auger injury.

BACKGROUND: Managing complex traumatic soft tissue wounds involving a large surface area while attempting to optimize healing, avoid infection, and promote favorable cosmetic outcomes is challenging. Regenerative materials such as ECMs are typically used in wound care to enhance the wound healing response and proliferative phase of tissue formation. CASE REPORT: The case reported herein is an example of the efficacious use of an SEFM in the surgical management of a large complex traumatic wound involving the left lower extremity and lower abdominal region. The wound bed was successfully prepared for skin grafting over an area of 1200 cm2, making this among the largest applications of the SEFM reported in the literature. CONCLUSION: This case report demonstrates the clinical versatility of the SEFM and a synergistic approach to complex traumatic wound care. The SEFM was successfully used to achieve tissue granulation for a successful skin graft across a large surface in an anatomic region with complex topography.

Histopathologic Analysis of a Recalcitrant Calcaneal Wound Treated Using a Synthetic Hybrid-scale Fiber Matrix.

Traditionally, full-thickness wounds with exposed structures are treated with flap coverage or dermal regenerative templates. Most dermal regenerative templates are biologic in origin, but recently synthetic options have become available. One such product is a synthetic hybrid-scale fiber matrix (SHSFM). In this case, SHSFM was used to treat a recalcitrant calcaneal wound. After the wound granulated, it was biopsied, and histopathologic analysis was conducted. A 16-year-old woman involved in a motor vehicle collision sustained multiple traumatic injuries which were stabilized. Postoperatively, she developed a calcaneal infection and associated wound, which developed into a chronic, nonhealing wound. Failed treatments included removal of hardware, multiple debridements, and advanced wound therapies. An SHSFM was then trialed, which led to granulation of the wound without infection. Despite wound healing, the patient subsequently elected to undergo a below-the-knee amputation due to pain and functional disability from posttraumatic ankle arthritis. The heel was biopsied at the time of amputation for analysis. Pathologists noted excellent granulation tissue formation and complete coverage of the wound surface area and 75% of the wound depth, which included epithelialization and decreasing inflammation at wound edges. Collagen deposition and numerous interspersed blood vessels were present. Foreign material and bacteria were absent. No osteomyelitis was observed. This analysis provided the opportunity to investigate the in vivo regenerate from a novel synthetic SHSFM. Given the uniqueness and challenges presented in this case, the usage of this relatively new product warrants further investigation with larger populations and assorted wound etiologies.

Bioresorbable, wireless, passive sensors for continuous pH measurements and early detection of gastric leakage.

Continuous monitoring of biomarkers at locations adjacent to targeted internal organs can provide actionable information about postoperative status beyond conventional diagnostic methods. As an example, changes in pH in the intra-abdominal space after gastric surgeries can serve as direct indicators of potentially life-threatening leakage events, in contrast to symptomatic reactions that may delay treatment. Here, we report a bioresorbable, wireless, passive sensor that addresses this clinical need, designed to locally monitor pH for early detection of gastric leakage. A pH-responsive hydrogel serves as a transducer that couples to a mechanically optimized inductor-capacitor circuit for wireless readout. This platform enables real-time monitoring of pH with fast response time (within 1 hour) over a clinically relevant period (up to 7 days) and timely detection of simulated gastric leaks in animal models. These concepts have broad potential applications for temporary sensing of relevant biomarkers during critical risk periods following diverse types of surgeries.

Bioresorbable shape-adaptive structures for ultrasonic monitoring of deep-tissue homeostasis.

Monitoring homeostasis is an essential aspect of obtaining pathophysiological insights for treating patients. Accurate, timely assessments of homeostatic dysregulation in deep tissues typically require expensive imaging techniques or invasive biopsies. We introduce a bioresorbable shape-adaptive materials structure that enables real-time monitoring of deep-tissue homeostasis using conventional ultrasound instruments. Collections of small bioresorbable metal disks distributed within thin, pH-responsive hydrogels, deployed by surgical implantation or syringe injection, allow ultrasound-based measurements of spatiotemporal changes in pH for early assessments of anastomotic leaks after gastrointestinal surgeries, and their bioresorption after a recovery period eliminates the need for surgical extraction. Demonstrations in small and large animal models illustrate capabilities in monitoring leakage from the small intestine, the stomach, and the pancreas.

Nerve allografts supplemented with schwann cells overexpressing glial-cell-line-derived neurotrophic factor.

INTRODUCTION: We sought to determine whether supplementation of acellular nerve allografts (ANAs) with Schwann cells overexpressing GDNF (G-SCs) would enhance functional recovery after peripheral nerve injury. METHODS: SCs expanded in vitro were infected with a lentiviral vector to induce GDNF overexpression. Wild-type SCs (WT-SCs) and G-SCs were seeded into ANAs used to repair a 14-mm nerve gap defect. Animals were harvested after 6 and 12 weeks for histomorphometric and muscle force analysis. RESULTS: At 6 weeks, histomorphometry revealed that ANAs supplemented with G-SCs promoted similar regeneration compared with isograft at midgraft. However, G-SCs failed to promote regeneration into the distal stump. At 12 weeks, ANAs with G-SCs had lower maximum and specific force production compared with controls. CONCLUSIONS: The combined results suggest that consistent overexpression of GDNF by G-SCs trapped axons in the graft and prevented functional regeneration.

Antimicrobial Effectiveness Testing of Resorbable Electrospun Fiber Matrix per United States Pharmacopeia (USP) <51>.

Contamination of surgical, traumatic, and chronic wounds with microorganisms presents a challenge to successful wound healing. In the present in vitro study, a synthetic electrospun fiber matrix (SEFM) cleared for use in the management of chronic, surgical, and traumatic wounds underwent USP (United States Pharmacopeia) <51> Antimicrobial Effectiveness Testing to determine its in vitro effectiveness against various microorganisms commonly found in non-healing wounds. The SEFM was tested in both sheet (s-SEFM) and micronized form (m-SEFM) against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Aspergillus brasiliensis, Candida albicans, Proteus mirabilis, and Enterococcus faecalis. Testing was performed per the USP <51> standard on days 7, 14, and 28. Both the s-SEFM and m-SEFM met the USP <51> acceptance criteria for all microorganisms. The results obtained for s-SEFM demonstrated >1-log10 reduction against E. coli, S. aureus, P. aeruginosa, P. mirabilis, E. faecalis, and C. albicans at day 7; >3-log10 reduction with no detection of these microbes at days 14 and 28, and no increase from initial inoculum at days 7, 14, and 28 against A. brasiliensis. The results obtained for m-SEFM demonstrated >3-log10 reduction with no detectable microorganisms at day 7. The results observed in this study indicate that the SEFM is effective in vitro at inhibiting bacterial and fungal growth and colonization per USP <51> testing.

Clinical application of a synthetic hybrid-scale fiber matrix in a pediatric trauma patient.

INTRODUCTION: Large soft tissue defects resulting from trauma in the pediatric population are common. MLLs are a rare subset of these injuries with no standard treatment regimen. Thorough surgical debridement of these lesions is often warranted to remove necrotic tissue and contamination, which results in a large, open soft tissue defect. STSGs may be used to provide tissue coverage; however, they have limitations, including donor site morbidity and additional surgical time and cost. CASE REPORT: A 12-year-old female with a cutaneous thermal contact burn and an MLL of the right lower medial thigh declined STSG to avoid additional operations. The wound was treated with an SHSFM that is engineered to mimic the structure and architecture of human extracellular matrix and supports cellular infiltration and proliferation with minimal inflammatory response. Over a 4-month period, the SHSFM was applied 6 times at 2- to 3-week intervals, resulting in complete regranulation and wound closure with no further surgical procedures required. CONCLUSIONS: This case demonstrates the utility of the SHSFM in the management of pediatric surgical wounds and highlights the flexibility of the SHSFM in achieving the goals of both patient and physician alike.

Electroactive Spinal Instrumentation for Targeted Osteogenesis and Spine Fusion: A Computational Study.

BACKGROUND: Direct current electrical stimulation may serve as a promising nonpharmacological adjunct promoting osteogenesis and fusion. The aim of this study was to evaluate the utility of electroactive spine instrumentation in the focal delivery of therapeutic electrical stimulation to enhance lumbar bone formation and interbody fusion. METHODS: A finite element model of adult human lumbar spine (L4-L5) instrumented with single-level electroactive pedicle screws was simulated. Direct current electrical stimulation was routed through anodized electroactive pedicle screws to target regions of fusion. The electrical fields generated by electroactive pedicle screws were evaluated in various tissue compartments including isotropic tissue volumes, cortical, and trabecular bone. Electrical field distributions at various stimulation amplitudes (20-100 µA) and pedicle screw anodization patterns were analyzed in target regions of fusion (eg, intervertebral disc space, vertebral body, and pedicles). RESULTS: Electrical stimulation with electroactive pedicle screws at various stimulation amplitudes and anodization patterns enabled modulation of spatial distribution and intensity of electric fields within the target regions of lumbar spine. Anodized screws (50%) vs unanodized screws (0%) induced high-amplitude electric fields within the intervertebral disc space and vertebral body but negligible electric fields in spinal canal. Direct current electrical stimulation via anodized screws induced electrical fields, at therapeutic threshold of >1 mV/cm, sufficient for osteoinduction within the target interbody region. CONCLUSIONS: Selective anodization of electroactive pedicle screws may enable focal delivery of therapeutic electrical stimulation in the target regions in human lumbar spine. This study warrants preclinical and clinical testing of integrated electroactive system in inducing target lumbar fusion in vivo. CLINICAL RELEVANCE: The findings of this study provide a foundation for clinically investigating electroactive intrumentation to enhance spine fusion.

Percutaneously introduced wireless intramuscular near-infrared spectroscopy device detects muscle oxygenation changes in porcine model of lower extremity compartment syndrome.

Serial examination and direct measurement of intracompartmental pressure (ICP) are suboptimal strategies for the detection of acute compartment syndrome (CS) because they are operator-dependent and yield information that only indirectly reflects intracompartmental muscle perfusion. As a result, instances of unnecessary fasciotomy and unrecognized CS are relatively common. Recently, near-infrared spectroscopy (NIRS)-based systems for compartment monitoring have generated interest as an adjunct tool. Under ideal conditions, NIRS directly measures the oxygenation of intracompartmental muscle (StO2 ), thereby obviating the challenges of interpreting equivocal clinical examination or ICP data. Despite these potential advantages, existing NIRS sensors are plagued by technical difficulties that limit clinical utility. Most of these limitations relate to their transcutaneous design that makes them susceptible to both interference from intervening skin/subcutaneous tissue, underlying hematoma, and instability of the skin-sensor interface. Here, we present a flexible, wireless, Bluetooth-enabled, percutaneously introducible intramuscular NIRS device that directly and continuously measures the StO2 of intracompartmental muscle. Proof of concept for this device is demonstrated in a swine lower extremity balloon compression model of acute CS, wherein we simultaneously track muscle oxygenation, ICP, and compartment perfusion pressure (PP). The observed StO2 decreased with increasing ICP and decreasing PP and then recovered following pressure reduction. The mean change in StO2 as the PP was decreased from baseline to 30 mmHg was -7.6%. The mean difference between baseline and nadir StO2 was -17.4%. Cross-correlations (absolute value) describing the correspondence between StO2 and ICP were >0.73. This novel intramuscular NIRS device identifies decreased muscle perfusion in the setting of evolving CS.

Development of novel electrospun absorbable polycaprolactone (PCL) scaffolds for hernia repair applications.

INTRODUCTION: Permanent/nonresorbable hernia repair materials rely on profibrotic wound healing, and repair sites are commonly composed of disorganized tissue with inferior mechanical strength and risk of reherniation. Resorbable electrospun scaffolds represent a novel class of biomaterials, which may provide a unique platform for the design of advanced soft tissue repair materials. These materials are simple, inexpensive, nonwoven materials composed of polymer fibers that readily mimic the natural extracellular matrix. The primary goal of the present study was to evaluate the physiomechanical properties of novel electrospun scaffolds to determine their suitability for hernia repair. Based on previous experimentation, scaffolds possessing ≥ 20 N suture retention strength, ≥ 20 N tear resistance, and ≥ 50 N/cm tensile strength are appropriate for hernia repair. METHODS: Six novel electrospun scaffolds were fabricated by varying combinations of polymer concentration (10-12 %) and flow rate (3.5-10 mL/h). Briefly, poly(ε-caprolactone) (PCL) was dissolved in a solvent mixture and electrospun onto a planar metal collector, yielding sheets with randomly oriented fibers. Physiomechanical properties were evaluated through scanning electron microscopy, laser micrometry, and mechanical testing. RESULTS: Scanning electron micrographs demonstrated fiber diameters ranging from 1.0 ± 0.1 µm (10 % PCL, 3.5 mL/h) to 1.5 ± 0.2 µm (12 % PCL, 4 mL/h). Laser micrometry demonstrated thicknesses ranging from 0.72 ± 0.07 mm (12 % PCL, 10 mL/h) to 0.91 ± 0.05 mm (10 % PCL, 3.5 mL/h). Mechanical testing identified two scaffolds possessing suture retention strengths ≥ 20 N (12 % PCL, 10 mL/h and 12 % PCL, 6 mL/h), and no scaffolds possessing tear resistance values ≥ 20 N (range, 4.7 ± 0.9 N to 10.6 ± 1.8 N). Tensile strengths ranged from 35.27 ± 2.08 N/cm (10 % PCL, 3.5 mL/h) to 81.76 ± 15.85 N/cm (12 % PCL, 4 mL/h), with three scaffolds possessing strengths ≥ 50 N/cm (12 % PCL, 10 mL/h; 12 % PCL, 6 mL/h; 12 % PCL, 4 mL/h). CONCLUSIONS: Two electrospun scaffolds (12 % PCL, 10 mL/h and 12 % PCL, 6 mL/h) possessed suture retention and tensile strengths appropriate for hernia repair, justifying evaluation in a large animal model. Additional studies examining advanced methods of fabrication may further improve the unique properties of these scaffolds, propelling them into applications in a variety of clinical settings.

GDNF overexpression fails to provoke muscle recovery from botulinum toxin poisoning: a preliminary study.

Glial cell line-derived neurotrophic factor (GDNF) has potent axonal growth and survival effects on motoneurons. This study used transgenic Myo-GDNF mice to assess the effects of targeted GDNF overexpression on functional recovery after botulinum toxin type A (BTxA) chemodenervation. BTxA (0.1 U) was injected into the tibialis anterior (TA) muscle of wild-type CF1 and transgenic Myo-GDNF mice. On days 1, 7, 14, and 21 after injection, evoked muscle force production and muscle mass were measured (n = 6, for each group at each time point). Greater maximal tetanic force and calculated specific force were evoked in Myo-GDNF animals when compared with control CF1 animals at days 1, 7, and 21. However, the differences were not statistically significant. Similarly, modest reductions in muscle atrophy in the Myo-GDNF group at all time points were not statistically significant. Targeted overexpression of GDNF in the muscles of Myo-GDNF mice did not improve motor recovery in the first 21 days after BTxA chemodenervation.