Creating and Transferring an Innervated, Vascularized Muscle Flap Made from an Elastic, Cellularized Tissue Construct Developed In Situ.

Reanimating facial structures following paralysis and muscle loss is a surgical objective that would benefit from improved options for harvesting appropriately sized muscle flaps. The objective of this study is to apply electrohydrodynamic processing to generate a cellularized, elastic, biocomposite scaffold that could develop and mature as muscle in a prepared donor site in vivo, and then be transferred as a thin muscle flap with a vascular and neural pedicle. First, an effective extracellular matrix (ECM) gel type is selected for the biocomposite scaffold from three types of ECM combined with poly(ester urethane)urea microfibers and evaluated in rat abdominal wall defects. Next, two types of precursor cells (muscle-derived and adipose-derived) are compared in constructs placed in rat hind limb defects for muscle regeneration capacity. Finally, with a construct made from dermal ECM and muscle-derived stem cells, protoflaps are implanted in one hindlimb for development and then microsurgically transferred as a free flap to the contralateral limb where stimulated muscle function is confirmed. This construct generation and in vivo incubation procedure may allow the generation of small-scale muscle flaps appropriate for transfer to the face, offering a new strategy for facial reanimation.

Development of a Novel Scar Screening System with Machine Learning.

BACKGROUND: Hypertrophic scars and keloids tend to cause serious functional and cosmetic impediments to patients. As these scars are not life threatening, many patients do not seek proper treatment. Thus, educating physicians and patients regarding these scars is important. The authors aimed to develop an algorithm for a scar screening system and compare the accuracy of the system with that of physicians. This algorithm was designed to involve health care providers and patients. METHODS: Digital images were obtained from Google Images (Google LLC, Mountain View, Calif.), open access repositories, and patients in the authors' hospital. After preprocessing, 3768 images were uploaded to the Google Cloud AutoML Vision platform and labeled with one of the four diagnoses: immature scars, mature scars, hypertrophic scars, and keloid. A consensus label for each image was compared with the label provided by physicians. RESULTS: For all diagnoses, the average precision (positive predictive value) of the algorithm was 80.7 percent, the average recall (sensitivity) was 71 percent, and the area under the curve was 0.846. The algorithm afforded 77 correct diagnoses with an accuracy of 77 percent. Conversely, the average physician accuracy was 68.7 percent. The Cohen kappa coefficient of the algorithm was 0.69, while that of the physicians was 0.59. CONCLUSIONS: The authors developed a computer vision algorithm that can diagnose four scar types using automated machine learning. Future iterations of this algorithm, with more comprehensive accuracy, can be embedded in telehealth and digital imaging platforms used by patients and primary doctors. The scar screening system with machine learning may be a valuable support tool for physicians and patients. CLINICAL QUESTION/LEVEL OF EVIDENCE: Diagnostic, II.

A Novel Technique to Lengthen the Reverse Latissimus Dorsi Muscle Flap Arc.

Reconstruction of the lower lumbar region is challenging for surgeons due to limited locoregional flap choices. The latissimus dorsi muscle flap is a mainstay for this area; however, there are several limitations, including that the dominant thoracodorsal artery and vein pedicle-based flaps are not reachable for reconstruction of the lumbar region, while perforator of intercostal artery and veins pedicle-based reverse latissimus dorsi (RLD) flap mobility is limited by including multiple perforators. Here, we describe a novel operative technique that lengthens the rotation arc of RLD muscle flaps. The surgical technique is as follows: RLD is elevated based on lower perforator of intercostal artery and veins (usually including two of the eighth-11th perforators); thoracodorsal artery and vein are ligated; and the flap is mobilized toward the defect. When RLD was not reachable to the defect, the far aspect of the intercostal artery and vein from the defect was ligated and the perforator was elevated with the near aspect of the intercostal artery and vein from intercostal space. Because the intercostal space measured between approximately 3 cm and 4 cm, this dissection gained 3-4 cm of rotational arc per intercostal space. Moreover, because the lower ribs follow a medio-cranial to latero-caudal direction, this dissection enabled the flap to extend latero-caudally or medio-cranially while maintaining its blood supply. Other applications using this technique may involve expanding the RLD flap arc caudally, ventrally, and ipsilaterally. We believe this new technique provides a reliable alternative for lower back reconstruction.

Multiple Thrombi during Microvascular Anastomosis Caused by Decreased Antithrombin Activity: A Case Report.

With recent advances in microsurgical instruments and technique, microvascular anastomosis has become a universal surgical technique; however, thrombosis still presents in a number of cases. Tension, twisting, and compression to the anastomotic site are the main causes of thrombus; however, disorder of the coagulation-fibrinolysis system also need to be considered. To date, only few reports exist regarding thrombosis caused by disorder of coagulant system in microvascular anastomosis. Here we report our 3 cases in which multiple thrombus formation occurred intraoperatively caused by decrease of antithrombin (AT) activity. AT activity was measured twice a day after vascular anastomosis: after surgery and up to 3 days after surgery. Thrombosis was not observed in any of the 3 patients intraoperatively after the transfusion, or thrombosis was not observed in any of 3 patients intraoperatively after the transfusion or postoperatively, and no other complications were observed. In these 3 cases, the thrombus was not caused by technical error or other previously described factors. The observed intraoperative decrease in AT activity was thought to be caused by thrombus formation. It is important that microsurgeons are reminded that disorders of the coagulation-fibrinolysis system could cause thrombosis.

Correlation between blood flow, tissue volume and microvessel density in the flap.

The purpose of this study was to assess the correlation between tissue volume and blood flow of the flap in an animal model. Using animal model, tissue volume can be attenuated, and precise change of blood flow could be evaluated. We further investigate the relationship between blood flow and vascular density in the tissue. In this study, we assessed flap conductance (ml/min/mm Hg) as to evaluate the conductivity of blood flow into the flap. Japanese white rabbit was used (n = 7) for this study. The amount of blood flow of jejunal and latissimus dorsi muscle (LD) flaps was measured while removing the distal portion of the flap sequentially. Conductance at each time was calculated from blood pressure and blood flow volume. The tissue volume at each time was also measured. The correlation between conductance and volume was analyzed using a linear mixed model. Immunohistochemical evaluation of microvessel densities (MVD) in these tissues was also performed for CD31/PECAM1 positive area. Conductance and tissue volume were significantly correlated in both jejunal and LD flaps. As the volume increases by 1 cm3, the conductance increased significantly by 0.012 ml/min/mm Hg in jejunum, and by 0.0047 ml/min/mm Hg in LD. Mean MVD was 1.15 ± 0.52% in the jejunum and 0.37 ± 0.29% in the LD muscle. In this study, we revealed that flap conductance is proportional to volume and proportional constant is different between the type of tissue. It suggests that the difference of MVD creates the unique conductance of each tissue.

Intramyocardial injection of a fully synthetic hydrogel attenuates left ventricular remodeling post myocardial infarction.

Intramyocardial hydrogel injection is an innovative and promising treatment for myocardial infarction (MI) and has recently entered clinical trials. By providing mechanical support to the ventricular wall, hydrogel injectate may act to preserve cardiac function and slow the remodeling process that leads to heart failure. However, improved outcomes will likely depend on the use of hydrogels specifically designed for this unique application, and better understanding of the mechanisms affected by the intervention. In this work, we present the first large animal study achieving functional and geometrical improvements in treating MI using a relatively stiff, fully synthetic hydrogel designed for intramyocardial injection. In addition, the renin-angiotensin system coincided with the mechanical effects of hydrogel injection and attenuated left ventricular remodeling, even after significant hydrogel degradation had occurred in vivo. These results may inspire further optimization of hydrogel materials used in intramyocardial hydrogel injection therapy and a better description of physiologic pathways affected by its implementation to facilitate successful clinical translation.

Nuss procedure for patients with pectus excavatum with a history of intrathoracic surgery.

BACKGROUND: The aim of this study was to demonstrate the feasibility and safety of the Nuss procedure for patients with pectus excavatum (PE) with a history of intrathoracic surgery. PATIENTS: From April 2010 to December 2013, we performed 6 cases of PE repair in patients with a history of intrathoracic surgery. The causes of previous operations were congenital cystic adenomatoid malformation in 4 patients and congenital diaphragmatic hernia in 2. The patients' median age was 5 years (range, 4-9 years) and median preoperative pectus severity index was 4.63 (range, 3.42-10.03). Their intraoperative and postoperative courses were reviewed retrospectively. RESULTS: The mean overall operation time was 127.5 ±â€¯17.0 minutes, and the mean operation time for endoscopic pneumolysis was 28.8 ±â€¯12.3 minutes. Intraoperative exploration for pleural adhesion revealed that the endoscopic approach in the previous operation was associated with low pleural adhesion, and the open thoracotomy or laparotomy approach was associated with low to high pleural adhesion. One patient developed a pneumothorax on the first postoperative day. All the other patients had uneventful postoperative courses. All the patients received bar removal 2-3 years after bar insertion. One patient developed atelectasis after bar removal. All the other patients had an uneventful postoperative course. The mean postoperative follow-up time after bar removal was 20.1 ±â€¯14.7 months. CONCLUSIONS: History of intrathoracic surgery seems not a contraindication for the Nuss procedure. However, perioperative complications should be carefully monitored in both the bar insertion and removal operations.

Use of a pedicled omental flap to reduce inflammation and vascularize an abdominal wall patch.

BACKGROUND: Although a variety of synthetic materials have been used to reconstruct tissue defects, these materials are associated with complications such as seromas, fistulas, chronic patient discomfort, and surgical site infection. While alternative, degradable materials that facilitate tissue growth have been examined. These materials can still trigger a foreign body inflammatory response that can lead to complications and discomfort. MATERIALS AND METHODS: In this report, our objective was to determine the effect of placing a pedicled omental flap under a biodegradable, microfibrous polyurethane scaffold serving as a full-wall thickness replacement of the rat abdominal wall. It was hypothesized that the presence of the omental tissue would stimulate greater vascularization of the scaffold and act to reduce markers of elevated inflammation in the patch vicinity. For control purposes, a polydimethylsiloxane sheet was placed as a barrier between the omental tissue and the overlying microfibrous scaffold. Both groups were sacrificed 8 wk after the implantation, and immunohistological and reverse transcription polymerase chain reaction (RT-PCR) assessments were performed. RESULTS: The data showed omental tissue placement to be associated with increased vascularization, a greater local M2/M1 macrophage phenotype response, and mRNA levels reduced for inflammatory markers but increased for angiogenic and antiinflammatory factors. CONCLUSIONS: From a clinical perspective, the familiarity with utilizing omental flaps for an improved healing response and infection resistance should naturally be considered as new tissue engineering approaches that are translated to tissue beds where omental flap application is practical. This report provides data in support of this concept in a small animal model.

Design of a Coupled Thermoresponsive Hydrogel and Robotic System for Postinfarct Biomaterial Injection Therapy.

BACKGROUND: In preclinical testing, ventricular wall injection of hydrogels has been shown to be effective in modulating ventricular remodeling and preserving cardiac function. For some approaches, early-stage clinical trials are under way. The hydrogel delivery method varies, with minimally invasive approaches being preferred. Endocardial injections carry a risk of hydrogel regurgitation into the circulation, and precise injection patterning is a challenge. An epicardial approach with a thermally gelling hydrogel through the subxiphoid pathway overcomes these disadvantages. METHODS: A relatively stiff, thermally responsive, injectable hydrogel based on N-isopropylacrylamide and N-vinylpyrrolidone (VP gel) was synthesized and characterized. VP gel thermal behavior was tuned to couple with a transepicardial injection robot, incorporating a cooling feature to achieve injectability. Ventricular wall injections of the optimized VP gel have been performed ex vivo and on beating porcine hearts. RESULTS: Thermal transition temperature, viscosity, and gelling time for the VP gel were manipulated by altering N-vinylpyrrolidone content. The target parameters for cooling in the robotic system were chosen by thermal modeling to support smooth, repeated injections on an ex vivo heart. Injections at predefined locations and depth were confirmed in an infarcted porcine model. CONCLUSIONS: A coupled thermoresponsive hydrogel and robotic injection system incorporating a temperature-controlled injectate line was capable of targeted injections and amenable to use with a subxiphoid transepicardial approach for hydrogel injection after myocardial infarction. The confirmation of precise location and depth injections would facilitate a patient-specific planning strategy to optimize injection patterning to maximize the mechanical benefits of hydrogel placement.