Comparison of Collagen and Human Amniotic Membrane Nerve Wraps and Conduits for Peripheral Nerve Repair in Preclinical Models: A Systematic Review of the Literature

Introduction Collagen and human amniotic membrane (hAM) are Food and Drug Administration (FDA)-approved biomaterials that can be used as nerve wraps or conduits for repair of peripheral nerve injuries. Both biomaterials have been shown to reduce scarring and fibrosis of injured peripheral nerves. However, comparative advantages and disadvantages have not been definitively shown in the literature. The purpose of this systematic review is to comprehensively evaluate the literature regarding the roles of hAM and collagen nerve wraps and conduits on peripheral nerve regeneration in preclinical models. Methods The MEDLINE database was queried using the PubMed search engine on July 7, 2019, with the following search strategy: (“amniotic membrane” OR “amnion”) OR (“collagen conduit” OR “nerve wrap”)] AND “nerve.” All resulting articles were screened by two independent reviewers. Nerve type, lesion type/injury model, repair type, treatment, and outcomes were assessed. Results Two hundred and fifty-eight articles were identified, and 44 studies remained after application of inclusion and exclusion criteria. Seventeen studies utilized hAM, whereas 27 studies utilized collagen wraps or conduits. Twenty-three (85%) of the collagen studies utilized conduits, and four (15%) utilized wraps. Six (35%) of the hAM studies utilized conduits and 11 (65%) utilized wraps. Two (9%) collagen studies involving a conduit and one (25%) involving a wrap demonstrated at least one significant improvement in outcomes compared with a control. While none of the hAM conduit studies showed significant improvements, eight (73%) of the studies investigating hAM wraps showed at least one significant improvement in outcomes. Conclusion The majority of studies reported positive outcomes, indicating that collagen and hAM nerve wraps and conduits both have the potential to enhance peripheral nerve regeneration. However, relatively few studies reported significant findings, except for studies evaluating hAM wraps. Preclinical models may help guide clinical practice regarding applications of these biomaterials in peripheral nerve repair.

Color Doppler Ultrasound versus Computed Tomography Angiography for Preoperative Anterolateral Thigh Flap Perforator Imaging: A Systematic Review and Meta-Analysis

Background The anterolateral thigh (ALT) perforator flap is a commonly used flap with a predictable, though often variable, perforator anatomy. Preoperative imaging with color Doppler ultrasound (CDU) and computed tomography angiography (CTA) of ALT flap perforators can be a useful tool for flap planning. This study provides a complete review and analysis of the relevant preoperative ALT imaging literature. Methods Studies related to preoperative CDU and CTA imaging were reviewed, and information related to imaging method, sensitivity, false-positive rates, and perforator course identification (musculocutaneous vs. septocutaneous) were analyzed. Results A total of 23 studies related to preoperative ALT flap CDU and CTA imaging were included for review and analysis. Intraoperative perforator identification was compared with those found preoperatively using CDU (n = 672) and CTA (n = 531). Perforator identification sensitivity for CDU was 95.3% (95% CI: 90.9–97.6%) compared with the CTA sensitivity of 90.4% (95% confidence interval [CI]: 74.4–96.9%). The false-positive rate for CDU was 2.8% (95% CI: 1.1–4.5%) compared with 2.4% (95% CI: 0.7–4.1%) for CTA. Accuracy of perforator course identification was 95.5% (95% CI: 93.6–99.2%) for CDU and 96.9% (95% CI: 92.7–100.1%) for CTA. Conclusion CDU provides the reconstructive surgeon with greater preoperative perforator imaging sensitivity compared with CTA; however, false-positive rates are marginally higher with preoperative CDU. Preoperative imaging for ALT flap design is an effective tool, and the reconstructive surgeon should consider the data presented here when selecting a flap imaging modality.

Application of Photoacoustic Imaging for Lymphedema Treatment

Background Lymphatic vessels are difficult to identify using existing modalities as because of their small diameter and the transparency of the lymph fluid flowing through them. Methods Here, we introduce photoacoustic lymphangiography (PAL), a new modality widely used for lymphedema treatment, to observe limb lymphatic vessels. The photoacoustic imaging system used in this study can simultaneously visualize lymphatic vessels and veins with a high resolution (0.2 mm) and can also observe their three-dimensional relationship with each other. Results High-resolution images of the lymphatic vessels, detailed structure of the dermal back flow, and the three-dimensional positional relationship between the lymphatic vessels and veins were observed by PAL. Conclusion The clear image provided by PAL could have a major application in pre- and postoperative use during lymphaticovenular anastomosis for lymphedema treatment.

Perforator-Based Flap Reconstruction after Melanoma Resection: Evaluation of Oncological, Aesthetic, and Functional Outcomes

Background Evidence in literature about the best reconstructive approach after melanoma resection is controversial, with some authors advocating that tissue rearrangement flap techniques might hinder the early detection of local relapses. The aim of the present study is to evaluate oncological, aesthetic, and functional outcomes following melanoma reconstruction using pedicled perforator-based flaps. Methods The authors reviewed all patients affected by melanoma treated during a 6-year period. Demographic data, tumor characteristics, and operative variables were evaluated. Locoregional recurrence was assessed with clinical and radiological follow-up. One-year postoperatively patients rated on a 5-point Likert scale the aesthetic and functional outcomes of the procedure. Three blind observers examined preoperative and 1-year postoperative photographs and rated the aesthetic outcome of the reconstructive procedure. Results One-hundred sixty-five patients were treated with wide excision and delayed reconstruction, including pedicled perforator-based flaps in 70 patients (group A) and primary closure in 95 patients (group B). Mean Breslow thickness was 2.972 and 2.189 mm in group A and B, respectively. There was no statistically significant difference in locoregional recurrence (chi-squared test, p = 0.8333; Fisher's exact test, p > 0.9999) between the two groups. Group A reported a higher satisfaction with both the aesthetic (mean rating 4.390 in group A and 4.094 in group B) and functional (mean rating 4.732 in group A and 4.170 in group B) outcomes of the procedure, the latter being statistically significant (p = 0.0006). Conclusion This series suggests that pedicled perforator-based flaps provide optimal aesthetic and functional outcomes in melanoma reconstruction without impairing the locoregional control of the disease.

Preoperative Computed Tomography Angiography for ALT Flaps Optimizes Design and Reduces Operative Time

Background Computed tomography angiography (CTA) has been widely used for perforator mapping in abdominal-based reconstruction, but it is less widespread in the anterolateral thigh (ALT) flap. However, CTA may be quite useful for ALT planning, as this flap has demonstrated substantial variability in intrapatient bilateral vascular anatomy. This study investigated whether standard use of preoperative CTA resulted in selection of the donor extremity with preferential perforator anatomy, and whether this affected operative time and postoperative outcomes. Methods A retrospective review of 105 patients who underwent proposed ALT flap reconstruction was performed. Seventy-nine patients received bilateral lower extremity CTAs, which were evaluated for dominant perforator anatomy (septocutaneous, musculoseptocutaneous, or musculocutaneous). Donor extremity selection was noted, and predicted perforator anatomy was compared with that encountered intraoperatively. Results Among the 73 patients who received bilateral imaging and ultimately received an ALT, congruent findings between imaging and surgical exploration were observed in 51 (69.8%) patients. Thirty (37.9%) patients had asymmetric perforator anatomy between their bilateral extremities on imaging. Among these, the leg with optimal perforator anatomy was selected in 70% of cases. There were no significant reductions among postoperative complication rates, but selection of the donor site with preferential anatomy was associated with a decrease in operative time (p = 0.049) among patients undergoing extremity reconstruction. Conclusion CTA is a useful tool for optimizing donor site selection for ALT flaps and reducing operative time. We believe that standard use of preoperative CTA in ALTs warrants further consideration.

Microsurgical Scalp Reconstruction: An Overview of the Contemporary Approach

Background Microsurgical scalp reconstruction has evolved immensely in the last half-century. The core concepts of microsurgical scalp reconstruction have always been to transfer soft tissue of a sufficient quality to within the defect while minimizing donor site morbidity. Refinements in scalp reconstruction consist of both improvement in reducing donor site morbidity and enhancing recipient site contour and balance. Furthermore, technical advancements and the vast experience within our field have allowed for preoperative evaluation of recipient vessels that are more favorable in proximity to the scalp. Methods In this review, we aim to describe the contemporary approach to microsurgical scalp reconstruction. This is to include the indications of choosing free flaps as well as how to select the ideal flap based on patient-oriented factors. The need for cranioplasty, recipient vessel selection, operative technique, and reoperations is also reviewed. In addition, our considerations and the nuances within each category are also described. Summary Scalp reconstructions involve the fundamental tenants of plastic surgery and demand application of these principles to each case on an individual basis and a successful reconstruction must consider all aspects, with backup options at the ready. Two workhorse free flaps, the anterolateral thigh perforator and latissimus dorsi muscles flaps, serve a primary role in the contemporary approach to microsurgical scalp reconstruction. Conclusion We hope this review can lay the foundation for which future plastic surgeons may continue to build and advance the approach to complex microsurgical scalp reconstruction.

Recent Advances in Ultrasound Technology: Ultra-High Frequency Ultrasound for Reconstructive Supermicrosurgery

Background Currently, microsurgeons are in the era of supermicrosurgery and perforator flap reconstruction. As these reconstructions frequently utilize vessels that are smaller than a single millimeter, understanding of location of lymphatic vessels and perforator anatomy preoperatively is essential. To change with the times, the role of ultrasound has changed from just an adjunct to primary imaging of the choice in reconstructive supermicrosurgery. Recently, a novel ultrasonographic technique involving the use of ultra-high frequency ultrasound (UHFUS) frequencies has entered the scene, and appears a promising tool in surgical planning. Methods The literatures on the applications of UHFUS in reconstructive supermicrosurgery were retrieved and reviewed from more than 60 literatures have been published on the surgical applications of UHFUS. Results Nine studies were retrieved from the literature on the applications of UHFUS in reconstructive supermicrosurgery. The articles report both application for lymphatic surgery and perforator flaps. Conclusions UHFUS application involves an increasing number of reconstructive supermicrosurgery field. UHFUS is a valuable and powerful tool for any reconstructive surgeons who are interested in performing supermicrosurgery.

Designing Anterolateral Thigh Flap Using Ultrasound

Background Preoperative knowledge of themicrovascular anatomy of a patientmay improve safetyand efficacy and reduce morbidity. Today, with the advancement in technology, ultrasound can provide minute details of the structures within the body, which makes this technology very helpful in preoperative evaluation of the traditional perforator flaps as well as thin, superthin, and pure skin perforator flaps. Methods In this article, we will describe the design of one of the most popular perforator flaps, the anterolateral thigh (ALT) flap, using high-frequency and ultrahigh-frequency ultrasound technology. Results Ultrasound technology allows to study preoperatively the ALT donor-site and its microvascular anatomy by using different US modalities in order to provide a virtual surgical plan to the operating surgeon. Conclusion Ultrasound technology allow to expand preoperative knowledge of flap microvascular anatomy and its course within the subcutaneous tissue up to and within the dermis, allowing to select the best perforator for the given reconstruction and the plane of elevation for thin, superthin and pure skin perforator flap.

A Comparative Analysis of Immediate and Delayed-immediate Breast Reconstruction after Postmastectomy Radiation Therapy

Background Postmastectomy radiation therapy (PMRT) is an important component in the treatment of locally advanced breast cancer. Optimal timing of therapy in relation to autologous breast reconstruction (ABR) remains clinically debated. Herein, we comparatively analyze short- and long-term outcomes between immediate ABR (I-ABR) and delayed-immediate ABR (DI-ABR) in the setting of PMRT. Methods Adult patients undergoing ABR with PMRT were separated into cohorts based on reconstructive timeline: I-ABR or DI-ABR. The groups were propensity matched 1:1 by age, body mass index, and comorbidities. Surgical site events and long-term clinical outcomes (readmissions, reoperations, and revision procedures) were collected. Univariate analyses were completed using Pearson's chi-squared tests and Fisher's exact tests, and statistical significance was set at p < 0.05. Results One hundred and thirty-two flaps (66 in each cohort) were identified for inclusion. Patients with I-ABR were more likely to experience fat necrosis (p = 0.034) and skin necrosis (p < 0.001), require additional office visits (p < 0.001) and outpatient surgeries (p = 0.015) to manage complications, and undergo revision surgery after reconstruction (p < 0.001). DI-ABR patients, however, had a 42.4% incidence of complications following tissue expander placement prior to reconstruction, with 16.7% of patients requiring reoperation during this time. Only one patient (I-ABR) experienced flap loss due to a vascular complication. Conclusion The complications encountered in both of these groups were not prohibitive to offering either treatment. Patients should be made aware of the specific and unique risks of these reconstruction timelines and involved throughout the entire decision-making process. Plastic surgeons should continue to strive to elucidate innovative approaches that facilitate enhanced quality of life without compromising oncologic therapy.

Abdominal Wall Vascularized Composite Allotransplantation: A Scoping Review

Background Abdominal wall vascularized composite allotransplantation (AW-VCA) is a novel reconstructive technique used for large abdominal wall defects in combination with intestinal transplantation (ITx) or multivisceral abdominal transplantation (MVTx). Since the introduction of this procedure, several studies have been published reporting their experience. This study aims to present a scoping review looking at all available evidence-based medicine information to understand the most current surgical techniques and clinical outcomes. Methods This scoping review followed the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) extension for scoping reviews checklist. A comprehensive research strategy of several databases was conducted. Results A total of 31 studies were included in this review, which comprised animal, cadaveric, and human studies. In human studies, four surgical techniques with high flap survival rates and low complication rates were found. In cadaveric studies, it was shown that the use of iliofemoral cuff-based flaps provided adequate tissue perfusion to the abdominal wall graft. Also, the use of thoracolumbar nerves have been described to provide functionality to the AW-VCA and prevent long-term muscle atrophy. Conclusion AW-VCA is a safe and efficient alternative for patients with large and complex abdominal wall defects. The future holds a promising evolution of a functional AW-VCA, though surgeons must face and overcome the challenge of distorted anatomy frequently present in this population. Forthcoming studies with a better level of evidence are required to evaluate functionality and differences between surgical techniques.