Clinical flap prefabrication

A New Concept in Peripheral Nerve Repair: Incorporating the Tunica Adventitia

BACKGROUND

 Pedicled, prefabricated, and free nerve flaps have several drawbacks, such as requiring microsurgical anastomosis, the need for secondary operations and the risk of developing thrombosis. In this study, we aimed to vascularize the repaired nerve in a single session by establishing a connection between the epineurium of the repaired median nerve and the tunica adventitia of the brachial artery.

METHODS

 The technique was performed on the median nerves of a total of 42 rats over 13 weeks. While group 1 didn't receive any intervention, the following three groups (2, 3, and 4) received classic treatments (coaptation, graft, and vein conduit). In addition to classic treatments, the other three groups (5, 6, and 7) were vascularized by attaching the adventitia of the brachial artery to the repaired nerves. Nerve regeneration was evaluated using functional tests, immunohistochemical analysis, and electron microscope.

RESULTS

 The vascularized groups (5, 6, and 7) showed earlier functional recovery (p < 0.05). Vascularization reduced inflammation in the coaptation group, reduced fibrosis and degeneration in the nerve graft group, and reduced fibrosis, degeneration and disorganization while increased the number of passing fibers and myelination in the vein conduit group (p < 0.05). Vascularization provided superior ultrastructural findings. Microscopic analysis revealed a novel finding of "zone of neurovascular interaction" between the adventitia and the regenerating nerve.

CONCLUSION

 Vascularizing the repaired nerves with this new technique provided faster functional and better histological healing. Unlike classic vascularization techniques, this method does not require microsurgical anastomosis, does not carry the risk of thrombosis, and does not necessitate secondary operations. The "zone of neurovascular interaction" identified in this study revealed regenerating axon clusters alongside newly developed blood vessels. This important finding highlights a potential role of the tunica adventitia in nerve regeneration.

Biliverdin improved angiogenesis and suppressed apoptosis via PI3K/Akt-mediated Nrf2 antioxidant system to promote ischemic flap survival

Plastic and reconstructive surgeons frequently utilize random skin flap transplantation to repair skin defects. However, the procedure carries a substantial risk of necrosis. Previous research has suggested that Biliverdin (Bv), the main component of Calculus Bovis, possessed potent anti-ischemic properties, making it a potential therapeutic agent for skin flap survival. Hence, in this study, the potential of Bv in promoting flap survival has been comprehensively investigated. Network pharmacology analysis revealed that the pharmacological effects of Bv on ischemic diseases may be attributed to its modulation of various signaling molecules, including the PI3K-Akt pathway. In vitro results demonstrated that Bv treatment significantly promoted angiogenesis in human umbilical vein endothelial cells (HUVEC), even in the presence of H2O2. This was evident by the increased cell proliferation, enhanced migration, and improved tube formation. Bv also effectively attenuated the intracellular generation of reactive oxygen species (ROS) induced by H2O2, which was achieved by suppressing mitochondrial ROS production through the PI3K/Akt-mediated activation of Nrf2/HO-1 signaling pathway. Consequently, Bv treatment led to a significant reduction in apoptosis and an increase in cell viability of HUVEC. Furthermore, in vivo experiment demonstrated that Bv treatment vastly elevated flap survival through enhancing angiogenesis while decreasing oxidative stress and apoptosis, which was comparable to the results of positive control of N-acetylcysteine (Nac). In conclusion, this study not only established a solid foundation for future study on therapeutic potential of Bv, but also proposed a promising treatment approach for enhancing the success rate of flap transplants and other ischemic-related tissue repair.

Arteriovenous Shunts: Their Location and Role in Physiology, Pathology, and Tissue Transfer. A Preliminary Report in the Upper Limb

Background

Tiny arteriovenous (AV) shunts of 10-150 µm (0.01-0.15 mm) are documented in the hands and feet. Larger shunts up to 0.5 mm (500 µm) have been discovered by the authors in the inner canthus and the human eye. This study seeks their possible existence in the upper limb.

Methods

Radiographic lead oxide cadaver injection and dissection studies of 14 archival and six new upper limbs were examined.

Results

AV shunts of 0.1-0.5 mm were discovered between the brachial, ulnar, and radial arteries and their venae comitantes and between their arterial perforators and the subcutaneous veins.

Conclusion

This pilot study provides insight into the possible function of these large AV shunts associated with blood flow variation in temperature, blood pressure, tissue transfer, flap prefabrication, and flap necrosis.

The Role of Microsurgery in Burn Surgery

Acute burn reconstruction involves intricate strategies such as skin grafting and innovative technologies, addressing challenges in coverage and minimizing donor site morbidity. Despite being rarely used, flap reconstruction becomes necessary when critical structures are exposed, offering robust coverage and reducing complications. However, free flaps in acute burns face challenges, including a higher failure rate attributed to hyperinflammatory states and hypercoagulability. Surgical optimization strategies involve careful timing, patient preparation, and meticulous postoperative care. In delayed burn reconstruction, free flaps proved effective in functional and aesthetic restoration, with low flap loss rates and minimal contracture recurrence. Prefabricated and prelaminated flaps emerged as a solution for complex cases, ensuring the best functional and aesthetic possible outcomes in challenging facial burn reconstructions.

Intraoperative Indocyanine Green Angiography Facilitates Flap Fenestration and Facial Organ Fabrication in Total Facial Restoration

BACKGROUND

Because of a lack of effective measures to visualize flap vasculature and perfusion, flap fenestration and facial organ fabrication cannot be performed effectively, preventing the transition from two-dimensional coverage to restoration of the three-dimensional (3D) structure of facial organs. This study aimed to evaluate the efficacy of indocyanine green angiography (ICGA) in guiding flap fenestration and facial organ fabrication in total facial restoration.

METHODS

Ten patients with total facial scarring after burn injury were enrolled in the study. They were treated with preexpanded, prefabricated monoblock flaps for total face restoration. The openings of nostrils and oral and palpebral orifices, together with organ fabrication, were conducted under the guidance of intraoperative ICGA by hemodynamic evaluation of flap perfusion. Postoperative follow-up measures include vascular crisis, infection, flap necrosis, and aesthetic and functional recovery.

RESULTS

The opening of facial organ orifices was performed at the stage of flap transfer in nine patients. To avoid damaging the major nourishing vessels, the left palpebral orifice was opened 8 days after the flap transfer in one patient, as observed by ICGA. Based on ICGA evaluation, the decision to perform additional vascular anastomosis before flap fenestration was made in six patients. Hemodynamic analysis of flap perfusion after fenestration revealed no significant change. Follow-up showed satisfactory aesthetic recovery and well-restored 3D structures of facial organs.

CONCLUSION

This pilot study demonstrates how intraoperative ICGA can enhance the safety of flap fenestration, thereby transforming full facial restoration from the two-dimensional to the 3D realm by facilitating facial organ fabrication.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Total Face Reconstruction with Flap Prefabrication and Soft-Tissue Expansion Techniques

SUMMARY

Total facial deformities always lead to psychological and functional consequences, making plastic and reconstructive surgery a great challenge. The skin of the anterior chest area is matched in thickness, texture, and color to the head and face. The purpose of this article was to discuss and evaluate reconstructive surgeons' experiences with obtaining a monoblock flap from the anterior thoracic area for entire face reconstruction using flap prefabrication, soft-tissue expansion, and facial plastic surgery following skin flap transplantation. Two patients underwent prefabricated expanded anterior thoracic flap reconstructions for total facial deformities; data collection included face defect size, flap type, the shape of the expander, expansion time, and complications. All the face flaps that were transplanted survived without major complications. It is concluded that using a prefabricated expanded flap to reconstruct an entire facial soft-tissue defect can provide a high degree of matching, a wide enough covering area, and a thin enough skin thickness to cover the face. Autologous flap grafting is easy to implement and has a high application value.

Prelamination of Anterolateral Thigh Osseocutaneous Flap With Fibula for the Reconstruction of Zygomatic Arch Defects After Facial Trauma

Complex facial trauma usually results in significant physical, esthetical, functional, and psychological damage. Nowadays, tissue flap transfer is the most effective and common treatment for the reconstruction of facial defects. Among them, the prelaminated flap has a bigger role in reconstructing massive facial defects. In this report, the authors have described a case of a 48-year-old man who presented a complex defect of tissue and deformity in the oral and maxillofacial region because of traffic accident trauma. Given the complexity of this case, it was impossible to complete the reconstruction in a single operation. The authors used a vascularized fibula-free flap (VFFF) to reconstruct the right mandible during the first operation and implanted a segment of fibula into the subcutaneous tissue of the right anterolateral thigh, which was used during the second operation for the reconstruction of zygomatic arch. This individualized treatment plan achieved a final satisfactory surgical outcome.

The use of the chimeric conjoint flap technique for complex defects reconstruction throughout the body: Clinical experience with 28 cases

BACKGROUND

Large soft tissue defects reconstruction represents a frequent and complex challenge in plastic surgery. A critical point regards the equilibrium between the need of large amount of tissue, while minimizing donor site morbidity. This is a common issue that plastic surgeons face in their clinical practice. In this context, the chimeric conjoint flap technique can be a valuable option, allowing to better exploit many well-known procedures. The purpose of the present work is to show the reconstructive efficacy and reliability of this technique resorting to many different well-known flaps. No such a comprehensive collection of cases is available so far dealing with this procedure.

PATIENTS AND METHODS

Twenty-eight patients presenting large defects throughout the body were treated by means of different flaps, designed according to the chimeric conjoint flap concept. Patients' mean age was 61.9 years old (range 18-82 years), 20 were males and 8 females. The size of the defects ranged from 7 cm × 6 cm to 25 cm × 18 and presented shapes or localizations that were complex to be covered with a regular flap. The defects were located in 11 cases in the lower limbs, in 9 cases in the head and neck region, in 5 cases in the groin, and in 2 cases in the thorax. Cause of the defect was tumor resection in 20 cases, trauma-induced necrosis in 5 cases, Fournier's gangrene in 2 cases, and a chronic ulcer in 1 case. Fourteen flaps were free flaps while 14 were pedicled flaps. The chimeric conjoint flap technique consists in splitting the skin paddle a flap into two smaller island that can be rearranged in order to match the particular requirements of the recipient site. Different flaps were employed: the anterolateral thigh (ALT) flap was used in 19 cases, latissimus dorsi (LD) musculocutaneous flap in 4 cases, deep inferior epigastric (DIEP) in 3 cases, medial sural artery perforator (MSAP) in 1 case, free radial forearm flap (RFFF) in 1 case.

RESULTS

All the 28 patients were successfully treated. In 6 cases minor complications were encountered, 5 at recipient site and 1 at donor site, who were all managed conservatively. No second procedures were required. The mean follow-up period was 8.4 months (range 3-12 months). At the last follow-up evaluation all the patients reached an acceptable cosmetic result and, when limbs were affected, complete range of motion restoration.

CONCLUSIONS

The present case series provide promising evidence regarding the reliability and versatility of the chimeric conjoint flap technique for large and delicate defect reconstructions throughout the body.

Techniques and Innovations in Flap Engineering: A Review

Currently, the gold standard for complex defect reconstruction is autologous tissue flaps, with vascularized composite allografts as its highest level. Good clinical results are obtained despite considerable obstacles, such as limited donor sites, donor site morbidity, and complex operations. Researchers in the field of tissue engineering are trying to generate novel tissue flaps requiring small or no donor site sacrifice. At the base of existing technologies is the tissue’s potential for regeneration and neovascularization.

Prelaminated Temporoparietal Osteofascial Flap: A Novel Nasal Reconstruction Technique

Nasal reconstruction can be a difficult task to perform. It is a challenge when the defect to be reconstructed is extensive and involves the entire thickness of the nose. The difficulty is further increased when a recurrent tumor is removed, where other flaps were previously used to reconstruct the initial defect. A therapeutic option is microsurgical reconstruction; however, sometimes this cannot be performed. Furthermore, free flaps such as the anterolateral thigh or the antebrachialis radial tend to be very thick for the integuments of the face. Therefore, it is important to think of another reconstructive option to solve this problem. We present a case of nasal reconstruction with a prelaminated temporoparietal osteofascial flap, after full-thickness excision for recurrent carcinoma.

Enhanced vascularization andde novotissue formation in hydrogels made of engineered RGD-tagged spider silk proteins in the arteriovenous loop model

Due to its low immunogenic potential and the possibility to fine-tune their properties, materials made of recombinant engineered spider silks are promising candidates for tissue engineering applications. However, vascularization of silk-based scaffolds is one critical step for the generation of bioartificial tissues and consequently for clinical application. To circumvent insufficient vascularization, the surgically induced angiogenesis by means of arteriovenous loops (AVL) represents a highly effective methodology. Here, previously established hydrogels consisting of nano-fibrillary recombinant eADF4(C16) were transferred into Teflon isolation chambers and vascularized in the rat AVL model over 4 weeks. To improve vascularization, also RGD-tagged eADF4(C16) hydrogels were implanted in the AVL model over 2 and 4 weeks. Thereafter, the specimen were explanted and analyzed using histology and microcomputed tomography. We were able to confirm biocompatibility and tissue formation over time. Functionalizing eADF4(C16) with RGD-motifs improved hydrogel stability and enhanced vascularization even outperforming other hydrogels, such as fibrin. This study demonstrates that the scaffold ultrastructure as well as biofunctionalization with RGD-motifs are powerful tools to optimize silk-based biomaterials for tissue engineering applications.

Closing an Intractable Tracheoesophageal Fistula Caused by a Tracheoesophageal Shunt Using a Myocutaneous Flap and a Hinged Flap With Skin Graft in a Two-Step Procedure

Total laryngectomy involves removal of the vocal cords resulting in the loss of vocal function. After laryngectomy, the patient's vocal function can be restored in several ways, including the insertion of a tracheoesophageal (TE) shunt. A TE shunt is considered an effective means of restoring speech due to its high efficacy, low requirement for training, and no need for any equipment while speaking. However, complications such as saliva inflow into the trachea, caused by the widening of the shunt opening, have also been reported. Moreover, the optimal treatment for an enlarged fistula has not yet been established.

A fistula may also form at sites of hypopharyngeal reconstruction with free jejunal transplantation. Following its formation, the influx of saliva, infections, and pressure exerted by the act of swallowing make a fistula resistant to closure, and most patients require closure surgery using myocutaneous flaps.

We encountered a case where an intractable TE fistula formed due to a TE shunt after the patient underwent total pharyngolaryngeal resection for hypopharyngeal cancer and hypopharyngeal reconstruction with a free jejunum flap. Since the optimal method for the TE fistula closure remains uncertain, we attempted to close the fistula according to the fistula closure of the free jejunal transplantation.

Failure to close a TE fistula using a myocutaneous flap necessitates a re-closure procedure. However, because the surgical field around the trachea can be limited in such patients, creating an additional myocutaneous flap may not be feasible. In addition to the myocutaneous flap, ventilation control using a conventional intubation tube may further narrow the surgical field during the re-closure surgery. Based on our experience and existing literature, in this article, we summarize several ways of managing TE fistula when the surgical field around the trachea is limited.

Augmentation of Perforator Flap Blood Supply with Vascular Supercharge or Flap Prefabrication: Evaluation in a Rat Model

BACKGROUND

Vascular supercharge and flap prefabrication are two surgical maneuvers to improve flap blood supply. Although these techniques have been studied intensively, few studies have focused on the differences between supercharge and prefabricated flaps regarding their flap survival areas, vasculatures, and hemodynamics.

METHODS

In this study, 21 male Sprague-Dawley rats were divided into three groups as follows: group A, single perforator flap; group B, supercharge flap; and group C, prefabricated flap. Flap survival was measured 1 week after flap elevation. Indocyanine green angiography was applied to visualize flap vascularity and to analyze flap hemodynamics. Von Willebrand factor immunohistochemical staining was applied to assess the number of microvessels in the choke zone of the abdominal wall.

RESULTS

The flap survival areas were expanded significantly in the arteriovenous supercharge group and the vascular bundle prefabricated group compared with that in the single-perforator group (81.34 ± 8.12 percent and 75.51 ± 8.08 percent versus 46.27 ± 10.01 percent, respectively; p < 0.05). Hemodynamic analysis suggested that although a significant increase in arterial infusion could be achieved with flap prefabrication, the venous effusion of the prefabricated flap was the worst among the three groups, indicating greater susceptibility to compromised venous return. Active neovascularization was confirmed by an increased number of microvessels in group C. Specifically, the dilatation of choke vessels and the newly formed vessels of the prefabricated pedicle could be appreciated by indocyanine green angiographic mapping.

CONCLUSIONS

Both vascular supercharge and flap prefabrication can augment the blood supply of the perforator flap but by means of different mechanisms. Because a supercharge flap is less susceptible to venous compromise, it is suggested to first consider the use of vascular supercharging when feasible.

Total nasal reconstruction with pre-laminated, super-thin anterolateral thigh flap: A case report

Many techniques for nasal reconstruction have been described to achieve aesthetically and functionally favorable results. Local tissues, specifically the forehead flap, provide the best tissue match with the nose. However, when local tissue donor sites are limited, alternative options such as free tissue transfers should be considered. Herein, we describe a case of a 72-year-old male patient who had a total nasal and left malar defect reconstructed with a two-staged, pre-laminated, super-thin anterolateral thigh (ALT) flap. The patient's nasectomy was performed 15 years ago. The adjacent left malar defect was due to recent squamous cell carcinoma excision. Local tissues were unavailable for reconstruction due to previous tumor excisions. For the 8.5 × 5 cm defect, a 12.5 × 8 cm ALT flap was planned, with 7.5 × 8 cm for nasal reconstruction and 5 × 4 cm for malar reconstruction. During the first stage, a super-thin fascial ALT flap was raised without dissecting the perforators, and the nasal skeleton was laminated between these two flaps. Costal cartilages were harvested for the nasal skeleton and positioned between the suprafascial and the fascial ALT flaps. During the second stage, two perforators were dissected to the pedicle on the pre-laminated flap, and the flap was divided from the donor site. The nasal skeleton was fixed and anastomosis with the facial vessels was established. After both stages, no complications were observed. After one month, a revision surgery was performed to enhance the transition between the reconstructed nose and the cheek, and improve the nasal projection. Postoperatively, after one year, the patient had a stable nasal reconstruction with good breathing. Prelaminated, super-thin ALT flaps provide the advantages of a wide and versatile donor site and an acceptable donor site scar. They may be an option for patients who are not amenable to traditional reconstruction methods.

Total scrotal reconstruction following Fournier's gangrene with bilateral prelaminated superior medial thigh flaps

The patient is a 45-year-old man diagnosed with Fournier's gangrene and underwent treatment for septic shock, broad-spectrum antibiotic therapy and extensive surgical debridement of perineum, including total scrotectomy, ischiorectal fossa, abdomen and left superior thigh and flank. The patient required multiple staged complex reconstruction of the scrotum utilising prelaminated superior medial thigh flaps with use of dermal matrix, split-thickness skin grafting and pedicled gracilis muscle flap for coverage of the ischiorectal wound. The patient had full recovery and followed up 1 year postoperatively. This report discusses our technique for total scrotal reconstruction and provides review of surgical reconstructive techniques for wounds due to Fournier's gangrene.

Prefabricated Expanded Flap Combined With Expanded Scalp Flap for Total Face Resurfacing

ABSTRACT

Reconstruction of total facial deformities and defects has been a major challenge of reconstructive surgery. Allotransplantation is limited by the number of donors and the need for life-long immunosuppression. Autotransplantation, where multiple autogenous tissue grafts from various donor sites are used to repair facial defects, inevitably leaves conspicuous patchwork scars. A prefabricated monoblock flap, although the preferred treatment modality, is limited by insufficient blood supply and the large size of the flap. In the Journal of Craniofacial Surgery (2014;25:21-25), Li et al applied the technique of flap prefabrication and stem cell-assisted tissue expansion to reconstruct total facial injuries, but the operations were complicated and the final expanded flap area was also uncertain. This article introduces an approach to reconstruct total facial injuries with a prefabricated expanded thoracic flap combined with an expanded scalp flap (called combined flaps), which not only solves the limitations of blood supply and expanded volume but also reduces patchwork scars. The approach is a simple, feasible, and effective surgical method for total face resurfacing.

Partial Ear Reconstruction with a Prelaminated Induced Expanded Radial Artery Flap

A 76-year-old man underwent an extensive resection for squamous cell carcinoma 2 years before, resulting in the loss of the superior half of the right ear, without any attempt at reconstruction. The decision was to reconstruct with a combined suprafascial tissue expansion, an alloplastic framework fabricated with porous polyethylene, and a radial artery free flap. At 1-year follow-up, the patient was satisfied with the result. We believe this represents a novel approach to be considered for partial ear reconstruction.

Prelaminated paramedian forehead flap for subtotal nasal reconstruction using three-dimensional printing

Nasal reconstruction following a total or subtotal resection presents a challenging clinical scenario. Ample external skin coverage is readily available using the paramedian forehead flap (PMFF), but restoring adequate internal lining of sufficient size and pliability is a major limitation. Intranasal mucosal flaps or free tissue transfer is often employed for this purpose, each with their own sets of limitations. Prelamination of the PMFF with a skin graft prior to transfer is a method to create a composite flap with both internal and external lining. Another challenge in subtotal nasal reconstruction centres around restoring adequate dimensions to the nose without an existing template to work from. Three-dimensional (3D) printing has become an increasingly popular tool in reconstructive surgery as it captures precise patient-specific dimensions to guide reconstruction. Herein, we describe a case of subtotal nasal reconstruction using a prelaminated PMFF using a patient-specific 3D printed model as a template for reconstruction.

Total Nasal Reconstruction With Prefabricated and Prelaminated Free Flap

Nasal reconstruction is a complex staged procedure. When optimal donor areas are unavailable, flap prefabrication and prelamination techniques can be used for total nasal reconstruction. A technique of total nasal reconstruction using neovascularization of the supraclavicular skin from a skin free flap used for internal lining, along with prelamination of the cartilage framework and surgical delays, is described in 2 patients with adverse anatomical conditions.

Augmentation of Perforator Flap Blood Supply with Sole or Combined Vascular Supercharge and Flap Prefabrication for Difficult Head and Neck Reconstruction

Importance: The strategic option between vascular supercharge and flap prefabrication in the fabrication of multipedicle flaps for difficult head and neck reconstruction has not been reported. Objectives: To summarize our 13-year experience in the design of multipedicle pre-expanded perforator flaps for extensive head and neck defect reconstruction, with vascular supercharge and flap prefabrication, either solely or in combination. To discuss the strategy for judicious selection between these techniques in the design of multipedicle flaps at different donor sites. Design, Setting, and Participants: A retrospective study was performed in patients with severe head and neck deformities and treated with multipedicle pre-expanded perforator flaps between May 2005 and May 2018. Intraoperative indocyanine green angiography was utilized for visualization of flap perfusion and analysis of the hemodynamics of pre-existing perforator and prefabricated vessels. Main Outcomes and Measures: The main outcomes measured were (1) features of deformities, (2) multipedicle flap designs, and (3) postoperative complications and long-term functional and aesthetic outcomes. Results: Seventy-five multipedicle pre-expanded perforator flaps were harvested, including 44 supercharged, 26 prefabricated, and 5 tripedicle, combining both techniques, with sizes ranging from 22 × 12 to 45 × 27 cm². Hemodynamic analysis demonstrated slower arterial inflow (0.60 ± 0.29 U/s vs. 2.65 ± 1.29 U/s, p < 0.05) and venous outflow (0.10 U/s vs. 0.23 ± 0.11 U/s) in prefabricated vessels, compared to the pre-existing perforator, namely the internal mammary arterial perforator. Partial necroses were observed in three patients with only one requiring skin grafting. The aesthetic and functional outcomes were satisfying after reconstruction. Conclusions and Relevance: Multipedicle pre-expanded perforator flaps fabricated by vascular supercharge and flap prefabrication, either solely or in combination in various donor sites, are powerful reconstructive tools for extensive head and neck defects. For a more reliable design, vascular supercharging should be considered a priority strategy, and flap prefabrication an alternative when suitable supercharging vessels are unavailable.

The efficacy of dermofat grafts from the groin for correction of acquired facial deformities

Background

Posttraumatic acquired facial deformities require surgical treatment, with options including scar revision, fat grafts, implant insertion, and flap coverage. However, each technique has specific advantages and disadvantages.

Methods

From 2016 to 2018, 13 patients (eight with scar contracture and five with a depressed scar) were treated using dermofat grafts from the groin. The harvested dermofat was then inserted into the undermined dead space after the contracture was released, and a bolster suture was done for fixation considering the patient’s contour and asymmetry. A modified version of the Vancouver Scar Scale and satisfaction survey were used to compare deformity improvements before and after surgery.

Results

In most cases, effective volume correction and an aesthetically satisfactory contour were maintained well after dermofat grafting, without any major complications. In some cases, however, lipolysis proceeded rapidly when inflammation and infection were not completely eliminated. A significant difference was found in the modified Vancouver Scar Scale before and after surgery, with a p-value of 0.001. The average score on the satisfaction survey was 17.07 out of 20 points.

Conclusion

A dermofat graft with the groin as the donor site can be considered as an effective surgical option that is the simplest and most cost-effective method for the treatment of acquired facial deformities with scar contracture.

The feasibility and survival mechanism of a large free flap supported by a novel hybrid perfusion mode

OBJECTIVES

In this study, we presented a novel hybrid perfusion mode in an attempt to provide a new strategy to improve the survival of an extended large flap and discuss its possible mechanisms.

MATERIALS AND METHODS

A 14 × 10 cm flap was designed on the rabbit abdomen. Ninety-six rabbits were randomly divided into three groups based on the flap perfusion mode: control group I (CON 1, physiological perfusion mode with bilateral deep inferior epigastric vascular pedicles intact), control group II (CON 2, physiological perfusion mode with single deep inferior epigastric vascular pedicle intact), hybrid nourished group (physiological perfusion as in CON 2 combined with arterialized venous nonphysiological perfusion mode, referred to as a hybrid perfusion mode). Flap survival, status of vascular perfusion, microvasculature, histopathology, expression of CD34, eNOs, VEGF and metabolic status of the flaps by LC-MS were assessed in each group.

RESULTS

The results of "hybrid nourished" flaps were similar to the traditional flaps in terms of flap survival, level of vascular perfusion and microvasculature except the status of metabolites.

CONCLUSIONS

The feasibility of this novel hybrid perfusion mode will greatly extend the indications of flap transfer and efficiently improve the survival reliability of large flaps. In a sense, this mode will be an ideological emancipation for the field of flap surgery.

Tissue Engineering of the Microvasculature

The ability to generate new microvessels in desired numbers and at desired locations has been a long-sought goal in vascular medicine, engineering, and biology. Historically, the need to revascularize ischemic tissues nonsurgically (so-called therapeutic vascularization) served as the main driving force for the development of new methods of vascular growth. More recently, vascularization of engineered tissues and the generation of vascularized microphysiological systems have provided additional targets for these methods, and have required adaptation of therapeutic vascularization to biomaterial scaffolds and to microscale devices. Three complementary strategies have been investigated to engineer microvasculature: angiogenesis (the sprouting of existing vessels), vasculogenesis (the coalescence of adult or progenitor cells into vessels), and microfluidics (the vascularization of scaffolds that possess the open geometry of microvascular networks). Over the past several decades, vascularization techniques have grown tremendously in sophistication, from the crude implantation of arteries into myocardial tunnels by Vineberg in the 1940s, to the current use of micropatterning techniques to control the exact shape and placement of vessels within a scaffold. This review provides a broad historical view of methods to engineer the microvasculature, and offers a common framework for organizing and analyzing the numerous studies in this area of tissue engineering and regenerative medicine. © 2019 American Physiological Society. Compr Physiol 9:1155-1212, 2019.

Unconventional Perfusion Flaps in the Experimental Setting: A Systematic Review and Meta-Analysis

Supplemental Digital Content is available in the text.

Background:

Unconventional perfusion flaps offer multiple potential advantages compared with traditional flaps. Although there are numerous experimental articles on unconventional perfusion flaps, the multiple animal species involved, the myriad vascular constructions used, and the frequently conflicting data reported make synthesis of this information challenging. The main aim of this study was to perform a systematic review and meta-analysis of the literature on the experimental use of unconventional perfusion flaps, to identify the best experimental models proposed and to estimate their global survival rate.

Methods:

The authors performed a systematic review and meta-analysis of all articles written in English, French, Italian, Spanish, and Portuguese on the experimental use of unconventional perfusion flaps and indexed to PubMed from 1981 until February 1, 2017.

Results:

A total of 68 studies were found, corresponding to 86 optimized experimental models and 1073 unconventional perfusion flaps. The overall unconventional perfusion flap survival rate was 90.8 percent (95 percent CI, 86.9 to 93.6 percent; p < 0.001). The estimated proportion of experimental unconventional perfusion flaps presenting complete survival or nearly complete survival was 74.4 percent (95 percent CI, 62.1 to 83.7 percent; p < 0.001). The most commonly reported animal species in the literature were the rabbit (57.1 percent), the rat (26.4 percent), and the dog (14.3 percent). No significant differences were found in survival rates among these species, or among the diverse vascular patterns used.

Conclusion:

These data do not differ significantly from those reported regarding the use of unconventional perfusion flaps in human medicine, suggesting that rabbit, rat, and canine experimental unconventional perfusion flap models may adequately mimic the clinical application of unconventional perfusion flaps.

Preformed Vascular Networks Survive and Enhance Vascularization in Critical Sized Cranial Defects

Vascular networks provide nutrients, oxygen, and progenitor cells that are essential for bone function. It has been proposed that a preformed vascular network may enhance the performance of engineered bone. In this study vascular networks were generated from human umbilical vein endothelial cell and mesenchymal stem cell spheroids encapsulated in fibrin scaffolds, and the stability of preformed vascular networks and their effect on bone regeneration were assessed in an in vivo bone model. Under optimized culture conditions, extensive vessel-like networks formed throughout the scaffolds in vitro. After vascular network formation, the vascularized scaffolds were implanted in a critical sized calvarial defect in nude rats. Immunohistochemical staining for CD31 showed that the preformed vascular networks survived and anastomosed with host tissue within 1 week of implantation. The prevascularized scaffolds enhanced overall vascularization after 1 and 4 weeks. Early bone formation around the perimeter of the defect area was visible in X-ray images of samples after 4 weeks. Prevascularized scaffolds may be a promising strategy for engineering vascularized bone.

Collagen-Elastin and Collagen-Glycosaminoglycan Scaffolds Promote Distinct Patterns of Matrix Maturation and Axial Vascularization in Arteriovenous Loop-Based Soft Tissue Flaps

INTRODUCTION

Autologous free flaps are the criterion standard for reconstructions of complex soft tissue defects; however, they are limited by donor-site morbidities. The arteriovenous (AV) loop model enables the generation of soft tissue constructs based on acellular dermal matrices with a functional microvasculature and minimal donor site morbidity. The ideal scaffold for AV loop-based tissue engineering has not been determined.

METHODS

AV loops were placed into subcutaneous isolation chambers filled with either a collagen-elastin scaffold or a collagen-glycosaminoglycan scaffold in the thighs of rats. Matrix elasticity, neoangiogenesis, cell migration, and proliferation were compared after 14 and 28 days.

RESULTS

Mean vessel count and area had increased in both matrices at 28 compared with 14 days. Collagen-elastin matrices showed a higher mean vessel count and area compared with collagen-glycosaminoglycan matrices at 14 days. At 28 days, a more homogeneous vascular network and higher cell counts were observed in collagen-elastin matrices. Collagen-glycosaminoglycan matrices, however, exhibited less volume loss at day 28.

CONCLUSIONS

Collagen-based scaffolds are suitable for soft tissue engineering in conjunction with the AV loop technique. These scaffolds exhibit distinct patterns of angiogenesis, cell migration, and proliferation and may in the future serve as the basis of tissue-engineered free flaps as an individualized treatment concept for critical wounds.

Reconstruction of a 10-mm-long median nerve gap in an ischemic environment using autologous conduits with different patterns of blood supply: A comparative study in the rat

The aim of this study was to evaluate in the Wistar rat the efficacy of various autologous nerve conduits with various forms of blood supply in reconstructing a 10-mm-long gap in the median nerve (MN) under conditions of local ischemia. A 10-mm-long median nerve defect was created in the right arm. A loose silicone tube was placed around the nerve gap zone, in order to simulate a local ischemic environment. Rats were divided in the following experimental groups (each with 20 rats): the nerve Graft (NG) group, in which the excised MN segment was reattached; the conventional nerve flap (CNF) and the arterialized neurovenous flap (ANVF) groups in which the gap was bridged with homonymous median nerve flaps; the prefabricated nerve flap (PNF) group in which the gap was reconstructed with a fabricated flap created by leaving an arteriovenous fistula in contact with the sciatic nerve for 5 weeks; and the two control groups, Sham and Excision groups. In the latter group, the proximal stump of the MN nerve was ligated and no repair was performed. The rats were followed for 100 days. During this time, they did physiotherapy. Functional, electroneuromyographic and histological studies were performed. The CNF and ANVF groups presented better results than the NG group in the following assessments: grasping test, nociception, motor stimulation threshold, muscle weight, and histomorphometric evaluation. Radial deviation of the operated forepaw was more common in rats that presented worse results in the other outcome variables. Overall, CNFs and ANVFs produced a faster and more complete recovery than NGs in the reconstruction of a 10-mm-long median nerve gap in an ischemic environment in the Wistar rat. Although, results obtained with CNFs were in most cases were better than ANVFs, these differences were not statistically significant for most of the outcome variables.

Engineering a microcirculation for perfusion control of ex vivo-assembled organ systems: Challenges and opportunities

Donor organ shortage remains a clear problem for many end-stage organ patients around the world. The number of available donor organs pales in comparison with the number of patients in need of these organs. The field of tissue engineering proposes a plausible solution. Using stem cells, a patient's autologous cells, or allografted cells to seed-engineered scaffolds, tissue-engineered constructs can effectively supplement the donor pool and bypass other problems that arise when using donor organs, such as who receives the organ first and whether donor organ rejection may occur. However, current research methods and technologies have been unable to successfully engineer and vascularize large volume tissue constructs. This review examines the current perfusion methods for ex vivo organ systems, defines the different types of vascularization in organs, explores various strategies to vascularize ex vivo organ systems, and discusses challenges and opportunities for the field of tissue engineering.

Haemodynamically stimulated and in vivo generated axially vascularized soft-tissue free flaps for closure of complex defects: Evaluation in a small animal model

The arteriovenous (AV) loop model permits the creation of significant volumes of axially vascularized tissue that represents an alternative to conventional free flaps, circumventing their common limitations. However, such AV loop-based flaps have never before been examined in standardized animal models with respect to their suitability for reconstruction of critical bone-exposing defects. In the course of our preliminary studies, we implemented a novel defect model in rats that provides standardized and critical wound conditions and evaluated whether AV loop-generated flaps are suitable for free microsurgical transfer and closure of composite defects. We compared three groups of rodents with similar scapular defects: one received the AV flap, whereas controls were left to heal by secondary intention or with supplementary acellular matrix alone. To create the flaps, AV loops were placed into subcutaneous Teflon chambers filled with acellular matrix and transferred to the thigh region. Flap maturation was evaluated by histological analysis of angiogenesis and cell migration at days 14 and 28 after loop creation. Flap transfer to the scapular region and microsurgical anastomoses were performed after 14 days. Postoperative defect closure and perfusion were continually compared between groups. Within the AV flap chamber, the mean vessel number, cell count and the proportion of proliferating cells increased significantly over time. The novel defect model revealed that stable wound coverage with homogeneous vascular integration was achieved by AV loop-vascularized soft-tissue free flaps compared with controls. In summary, our study indicates for the first time that complex composite defects in rats can successfully be treated with AV loop-based free flaps.

Soft Tissue Engineering

There is a recognized need to reconstruct and restore complex craniomaxillofacial soft tissues. The objective of this article is to focus on the role that tissue engineering/regenerative medicine can play in addressing various barriers (vascularity, tissue bulk, volitional control, and esthetics) and impediments (timing, regional applicability/dissemination, and regulation by the US Food and Drug Administration) to optimal tissue reconstruction of complex soft tissue structures. We will use the lips as an example to illustrate our points.

Axially vascularised mandibular constructs: Is it time for a clinical trial?

Applying regenerative therapies in the field of cranio-maxillofacial reconstruction has now become a daily practice. However, regeneration of challenging or irradiated bone defects following head and neck cancer is still far beyond clinical application. As the key factor for sound regeneration is the development of an adequate vascular supply for the construct, the current modalities using extrinsic vascularization are incapable of regenerating such complex defects. Our group has recently introduced the intrinsic axial vascularization technique to regenerate mandibular defects using the arteriovenous loop (AVL). The technique has shown promising results in terms of efficient vascularization and bone regeneration at the preclinical level. In this article, we have conducted a narrative literature review about using the AVL to vascularize tissue-engineering constructs at the preclinical level. We have also conducted a systematic literature review about applying the technique of axial vascularization in the field of craniofacial regeneration. The versatility of the technique and the possible challenges are discussed, and a suggested protocol for the first clinical trial applying the AVL technique for mandibular reconstruction is also presented.

Engineering clinically relevant volumes of vascularized bone

Vascularization remains one of the most important challenges that must be overcome for tissue engineering to be consistently implemented for reconstruction of large volume bone defects. An extensive vascular network is needed for transport of nutrients, waste and progenitor cells required for remodelling and repair. A variety of tissue engineering strategies have been investigated in an attempt to vascularize tissues, including those applying cells, soluble factor delivery strategies, novel design and optimization of bio-active materials, vascular assembly pre-implantation and surgical techniques. However, many of these strategies face substantial barriers that must be overcome prior to their ultimate translation into clinical application. In this review recent progress in engineering vascularized bone will be presented with an emphasis on clinical feasibility.

A method for constructing vascularized muscle flap

Abdominal wall reconstruction following extensive tissue loss is essential and can be achieved using autologous flaps. However, their use is limited due to their inadequate availability and due to post-operative donor site scarification. This work presents a step-by-step technique for fabrication of a vascularized muscle flap, to be applied in full-thickness abdominal wall defect reconstruction. Poly L-lactic acid/poly lactic-co-glycolic acid scaffolds, prepared using a salt leaching technique, were used as the supporting matrix in vitro for simultaneously seeded endothelial cells, fibroblasts and myoblasts. The cell-embedded graft was then implanted around femoral artery and vein vessels, which provided a central blood supply. Vascularization and perfusion were achieved by capillary sprouting from the main host vessel into the graft. A thick and vascularized tissue was formed within one week, and was then transferred as an autologous flap together with its main vessels, to a full-thickness abdominal wall defect. The flap remained viable after transfer and featured sufficient mechanical strength to support the abdominal viscera. Thus, this engineered muscle flap can be used as an alternative source for autologous flaps to reconstruct full-thickness abdominal wall defects.

Successful human long-term application of in situ bone tissue engineering

Tissue Engineering (TE) and Regenerative Medicine (RM) have gained much popularity because of the tremendous prospects for the care of patients with tissue and organ defects. To overcome the common problem of donor-site morbidity of standard autologous bone grafts, we successfully combined tissue engineering techniques for the first time with the arteriovenous loop model to generate vascularized large bone grafts. We present two cases of large bone defects after debridement of an osteomyelitis. One of the defects was localized in the radius and one in the tibia. For osseus reconstruction, arteriovenous loops were created as vascular axis, which were placed in the bony defects. In case 1, the bone generation was achieved using cancellous bone from the iliac crest and fibrin glue and in case 2 using a clinically approved β-tricalciumphosphate/hydroxyapatite (HA), fibrin glue and directly auto-transplanted bone marrow aspirate from the iliac crest. The following post-operative courses were uneventful. The final examinations took place after 36 and 72 months after the initial operations. Computer tomogrphy (CT), membrane resonance imaging (MRI) and doppler ultrasound revealed patent arterio-venous (AV) loops in the bone grafts as well as completely healed bone defects. The patients were pain-free with normal ranges of motion. This is the first study demonstrating successfully axially vascularized in situ tissue engineered bone generation in large bone defects in a clinical scenario using the arteriovenous loop model without creation of a significant donor-site defect utilizing TE and RM techniques in human patients with long-term stability.

An engineered muscle flap for reconstruction of large soft tissue defects

Large soft tissue defects involve significant tissue loss, requiring surgical reconstruction. Autologous flaps are occasionally scant, demand prolonged transfer surgery, and induce donor site morbidity. The present work set out to fabricate an engineered muscle flap bearing its own functional vascular pedicle for repair of a large soft tissue defect in mice. Full-thickness abdominal wall defect was reconstructed using this engineered vascular muscle flap. A 3D engineered tissue constructed of a porous, biodegradable polymer scaffold embedded with endothelial cells, fibroblasts, and/or myoblasts was cultured in vitro and then implanted around the femoral artery and veins before being transferred, as an axial flap, with its vascular pedicle to reconstruct a full-thickness abdominal wall defect in the same mouse. Within 1 wk of implantation, scaffolds showed extensive functional vascular density and perfusion and anastomosis with host vessels. At 1 wk posttransfer, the engineered muscle flaps were highly vascularized, were well-integrated within the surrounding tissue, and featured sufficient mechanical strength to support the abdominal viscera. Thus, the described engineered muscle flap, equipped with an autologous vascular pedicle, constitutes an effective tool for reconstruction of large defects, thereby circumventing the need for both harvesting autologous flaps and postoperative scarification.

Evolution and limitations of conventional autologous reconstruction of the head and neck

Conventional reconstruction in the head and neck has undergone a revolution as microsurgery has evolved and expanded our ability to reconstruct the most difficult defects. Vascularized composite allotransplantation (VCA) has provided a new paradigm of options to restore in 1 stage what in the past has been performed in multiple stages with multiple combinations of free flaps and local flap options. This review demonstrates an evolving perspective of head and neck reconstructive surgery incorporating the indications and advantages gained over a career that has developed in parallel with microsurgery, prefabrication, prelamination, and face transplant. All current conventional reconstructions for the most severe defects often involve multistage procedures, using every rung of the reconstructive ladder, and the end results can still be lacking despite our best efforts. Despite all the tailoring and planning of these multiple flap and multiple-stage reconstructions, in our experience, these interventions never quite exactly recapitulate the face and fall short of full restoration. The early experience with VCA has been very promising and yields results that are superior to those achieved using conventional methods of reconstruction. However, it will be synergistic efforts in both VCA and conventional reconstruction to take us to the next level of full face restoration.

Prefabricated bone flap: an experimental study comparing deep-frozen and lyophilized-demineralized allogenic bones and tissue expression of transforming growth factor β

BACKGROUND

Extensive bone defects are still a challenge for reconstructive surgery. Allogenic bones can be an alternative with no donor area morbidity and unlimited amount of tissue. Better results can be achieved after allogenic bone preparation and adding a vascular supply, which can be done along with flap prefabrication. The purpose of this study was to evaluate demineralized/lyophilized and deep-frozen allogenic bones used for flap prefabrication and the tissue expression of transforming growth factor β (TGF-β) in these bone fragments.

METHODS

Fifty-six Wistar rat bone diaphyses were prepared and distributed in 4 groups: demineralized/lyophilized (experimental group 1 and control group 2) and deep freezing (experimental group 3 and control group 4). Two bone segments (one of each group) were implanted in rats to prefabricate flaps using superficial epigastric vessels (experimental groups) or only transferred as grafts (control groups). These fragments remained in their respective inguinal regions until the death that occurred at 2, 4, and 6 weeks after the operation. Semiquantitative histologic (tetracycline marking, cortical resorption, number of giant cells, and vascularization) and histomorphometrical quantitative (osteoid thickness, cortical thickness, and fibrosis thickness) analyses were performed. Transforming growth factor β immunohistochemistry staining was also performed.

RESULTS

Group 1 fragments presented an osteoid matrix on their external surface in all periods. Cartilage formation and mineralization areas were also noticed. These findings were not observed in group 3 fragments. Group 1 had more mineralization and double tetracycline marks, which were almost not seen in group 3. Cortical resorption and the number of giant cells were greater in group 3 in all periods. Vascularization and fibrosis thickness were similar in both experimental groups. Group 1 had more intense TGF-β staining within 2 weeks of study. Nevertheless, from 4 weeks onward, group 3 presented statistically significant stronger staining.

CONCLUSIONS

Although there are some differences between the preparation methods of allogenic bone, it is possible to prefabricate flaps with demineralized/lyophilized and deep-frozen bones.

Flap prefabrication using high-density porous polyethylene in an animal model – an experimental study

BACKGROUND

The search for new surgical flap techniques and modifications of already existing ones is gaining increasing popularity. Progress in flap designing and harvesting have improved the functional and aesthetic results, especially in head and neck reconstruction.

MATERIAL/METHODS

Ten pigs were used in this study. In the first operation, high-density porous polyethylene prefabrication was performed bilaterally in all pigs. After 8 weeks, each prefabricated complex was explored, resected, and macroscopically evaluated.

RESULTS

All of 20 prefabricated flaps survived. No serious surgical complications were observed. In 2 cases there was chronic inflammation and in 4 cases there was instability of the implant.

CONCLUSIONS

After this experimental study, we believe that the use of high-density porous polyethylene in flap prefabrication may be a good option for reconstruction of 3-dimensional defects, especially in patients with limited donor tissues.

The use of prefabrication technique in microvascular reconstructive surgery

AIM OF THE STUDY

The aim of the study was to develop standards for the prefabrication of free microvascular flaps in an animal model, followed by their application in clinical practice, and quantitative/qualitative microscopic assessment of the extent of development of a new microvascular network.

MATERIAL AND METHODS

The study was carried out in 10 experimental pigs. As the first stage, a total of 20 prefabricated flaps were created using polytetrafluoroethylene (PTFE) as a support material, placed horizontally over an isolated and distally closed vascular pedicle based on superficial abdominal vessels. After completing the animal model study, one patient was selected for the grafting of the prefabricated free flap.

RESULTS

All 20 free flaps prefabricated in the animal model were analyzed microscopically, exhibiting connective tissue rich in fibroblasts and small blood vessels in the porous areas across the entire thickness of the PTFE element.

CONCLUSIONS

Flap prefabrication is a new and fast developing reconstruction technique. The usefulness of prefabrication techniques and their status in reconstructive surgery still needs to be investigated experimentally and clinically. The method based on prefabricated free flaps is the first step towards anatomical bioengineering that will make it possible to replace missing organs with their anatomically perfect equivalents.