Fenestration Improves Acellular Dermal Matrix Biointegration: An Investigation of Revascularization with Photoacoustic Microscopy

Reconstructive breast implant-related infections: Prevention, diagnosis, treatment, and pearls of wisdom

Implant-based reconstructions are increasingly utilized following mastectomy in the prevention and treatment of breast cancer. However, these implants are associated with a high rate of infection, which is a major complication that can lead to implant removal, delay in adjuvant radiation and chemotherapy, and increase in health care costs. Early clinical signs and symptoms of infection, such as erythema, warmth, and tenderness, are challenging to discern from expected postsurgical responses. Furthermore, when atypical features are present or the patient's condition does not improve on adequate antimicrobials, the clinician should be prompted to consider an alternative noninfectious etiology. Herein we highlight the key elements of the preventive, diagnostic, and multidisciplinary therapeutic approach to salvaging the infected breast implant; review several infectious disease mimickers; and provide many pearls of wisdom that the practicing clinician must be familiar with and be able to manage in an effective and successful manner.

Longitudinal Monitoring of Angiogenesis in a Murine Window Chamber Model In Vivo

Angiogenesis induced by growth factor administration, which can augment the blood supply in regenerative applications, has drawn wide attention in medical research. Longitudinal monitoring of vascular structure and development in vivo is important for understanding and evaluating the dynamics of involved biological processes. In this work, a dual-modality imaging system consisting of photoacoustic microscopy (PAM) and optical coherence tomography (OCT) was applied for noninvasive in vivo imaging of angiogenesis in a murine model. Fibrin scaffolds, with and without basic fibroblast growth factor (bFGF), were implanted in a flexible imaging window and longitudinally observed over 9 days. Imaging was conducted at 3, 5, 7, and 9 days after implantation to monitor vascularization in and around the scaffold. Several morphometric parameters were derived from the PAM images, including vessel area density (VAD), total vessel length (TVL), and vessel mean diameter (VMD). On days 7 and 9, mice receiving bFGF-laden fibrin gels exhibited significantly larger VAD and TVL compared to mice with fibrin-only gels. In addition, VMD significantly decreased in +bFGF mice versus fibrin-only mice on days 7 and 9. Blood vessel density, evaluated using immunohistochemical staining of explanted gels and underlying tissue on day 9, corroborated the findings from the PAM images. Overall, the experimental results highlight the utility of a dual-modality imaging system in longitudinally monitoring of vasculature in vivo with high resolution and sensitivity, thereby providing an effective tool to study angiogenesis.

Acellular Dermal Matrix Favorably Modulates the Healing Response after Surgery

SUMMARY

When first described for breast reconstruction, the presence of acellular dermal matrices (ADM) was associated with increased seroma formation and infection. However, clinical safety data has gradually improved with surgeon experience to an acceptable outcomes profile of ADM-assisted reconstruction when compared to submuscular implant coverage. In fact, ADM use potentially decreases capsular contracture rates and facilitates expansion for staged pre-pectoral breast reconstruction. Due to new regulatory requirements, the collection of unbiased, well-powered pre-market approval data summarizing long-term clinical outcomes will be essential over the coming years to understand the clinical performance of ADM usage in breast reconstruction.Currently, we can highlight the physiologic benefits of ADM use in breast reconstruction by evaluating the components of surgical wound healing that are favorably augmented by the implanted collagen substrate. ADM takes advantage of the wound healing cascade to incorporate into the patient's tissues - a process that requires a coordinated inflammatory infiltrate and angiogenesis. The presence of ADM augments and modulates the wound healing process to its advantage by simultaneously increasing the invasion of appropriate cellular constituents to facilitate expeditious healing and accelerate angiogenesis. Herein, we summarize the wound healing literature to demonstrate the mechanisms ADM use to biointegrate and the literature in which cellular constituents and soluble growth factors are upregulated in the presence of ADM. Lastly, we use our experimental observations of ADM incorporation to corroborate the literature.

Immunomodulation of Acellular Dermal Matrix Through Interleukin 4 Enhances Vascular Infiltration

BACKGROUND

Acellular dermal matrix (ADM) supported implant-based reconstruction remains the most commonly performed mode of reconstruction after breast cancer. Acellular dermal matrix clinical usage has reported benefits but requires rapid and efficient vascular and cellular incorporation into the recipient to have the best outcomes. Orderly transition from M1 to M2 macrophage phenotypic profile, coordinated in part by interleukin 4 (IL-4), is an important component of vascular stabilization and remodeling. Using the ADM substrate as a delivery device for immunomodulation of macrophage phenotype holds the potential to improve integration.

METHODS

Interleukin 4 was adsorbed onto ADM samples and drug elution curves were measured. Next, experimental groups of 8 C57BL/6 mice had 5-mm ADM discs surgically placed in a dorsal window chamber with a vascularized skin flap on one side and a plastic cover slip on the other in a model of implant-based breast reconstruction. Group 1 consisted of IL-4 (5 μg) adsorbed into the ADM preoperatively and group 2 consisted of an untreated ADM control. Serial gross examinations were performed with histology at day 21 for markers of vascularization, mesenchymal cell infiltration, and macrophage lineage.

RESULTS

Drug elution curves showed sustained IL-4 release for 10 days after adsorption. Serial gross examination showed similar rates of superficial vascular investment of the ADM beginning at the periphery by day 14 and increasing through day 21. Interleukin-4 treatment led to significantly increased CD31 staining of vascular endothelial cells within the ADM over the control group (P < 0.05) at 21 days. Although vimentin staining did not indicate a significant increase in fibroblasts overall, IL-4 did result in a significant increase in expression of α-smooth muscle actin. The expression of macrophage phenotype markers Arginase1 and iNOS present within the ADM were not significantly affected by IL-4 treatment at the day 21 time point.

CONCLUSIONS

Acellular dermal matrix has the potential to be used for immunomodulatory cytokine delivery during the timeframe of healing. Using implanted ADM as a delivery vehicle to drive IL-4 mediated angiogenesis and vascular remodeling significantly enhanced vascularity within the ADM substrate.

Meshed Acellular Dermal Matrix for Two-Staged Prepectoral Breast Reconstruction: An Institutional Experience

The introduction of acellular dermal matrix (ADM) to breast reconstruction has allowed surgeons to reexplore the prepectoral implant placement technique in postmastectomy breast reconstruction. Our institution adopted a novel approach using meshed ADM to lessen the financial burden of increased ADM utilization with the prepectoral breast reconstruction. This is a retrospective, single-center review of two-stage prepectoral breast reconstruction using meshed human-derived ADM for anterior prosthesis coverage. Patient demographics, oncologic data, perioperative characteristics, and complications were examined and reported as means with standard deviations. Cost-saving with the meshed technique was evaluated. Forty-eight patients (72 breasts) with a mean age of 48.5 ± 15.0 years (range 26–70 years) were included in the study. The mean follow-up time was 13.2 ± 4.4 months (range 4.1–25.8 months). Nineteen breasts (24.6%) experienced complications, with seromas being the most common complication (12.5%, n  = 9). Expander removal and reoperation occurred at a rate of 8.3 and 9.7%, respectively. The average time to drain removal was 18.8 ± 6.6 days (range 8–32 days). Meshed ADM provided an average cost savings of $6,601 for unilateral and $13,202 for bilateral reconstructions. Our study found that human-derived meshed ADM can be safely used in two-staged prepectoral tissue expander-based breast reconstruction and can result in significant cost savings.

Understanding the Evidence and Improving Outcomes with Implant-Based Prepectoral Breast Reconstruction

LEARNING OBJECTIVES

After studying this article, the participant should be able to: 1. Describe the risks, benefits, and safety profile of prepectoral breast reconstruction. 2. Have knowledge of primary immediate and delayed prepectoral breast reconstruction techniques and secondary procedures required. 3. Describe data on outcomes of prepectoral breast reconstruction.

SUMMARY

Once considered to have an unacceptable complication profile, prepectoral breast reconstruction is increasing in popularity because of decreased surgical invasiveness and postoperative pain and the absence of animation deformity. Short-term outcomes studies comparing prepectoral breast reconstruction to partially submuscular techniques demonstrate similarly acceptable rates of postoperative complications. Aesthetic outcomes demonstrate similar rates of capsular contracture but increased rippling and implant palpability of the upper pole. Postoperative functional data are limited but overall show decreased pain and more rapid return of function but equivalent satisfaction on the BREAST-Q. Long-term aesthetic data and rates of revision are lacking.

Safety Profile and Predictors of Aesthetic Outcomes After Prepectoral Breast Reconstruction With Meshed Acellular Dermal Matrix

INTRODUCTION

Prepectoral acellular dermal matrix (ADM)-assisted breast reconstruction has demonstrated improved pain scores, faster return to full range of motion, and an appropriate postoperative safety profile when compared with cohorts with submuscular implant placement; however, there are limited data on aesthetic outcomes. Basic science biointegration research has previously demonstrated faster ADM incorporation with fenestrated compared with confluent ADM. We report the safety profile of anterior support meshed ADM prepectoral breast reconstruction and analyze predictive factors for aesthetic outcomes after gel implant placement.

METHODS

All consecutive immediate staged prepectoral expander-to-implant breast reconstructions with more than 6 months of follow-up were compared with a partially submuscular cohort for demographics, comorbidities, and postoperative complications. All patients 1 to 3.5 years after gel implant placement were evaluated for the impact of clinical characteristics on aesthetic outcomes.

RESULTS

Two hundred twenty-four prepectoral tissue expander placements were compared with 535 partially submuscular tissue expanders with no significant differences in demographics. There was increased wound dehiscence repaired in clinic and insignificantly decreased seromas with prepectoral expander placement. One hundred sixty breasts were reconstructed with gel implants, and 12 underwent autologous reconstruction during the conduct of the study. The remaining 21 patients were continuing expansion, and 3 succumbed to disease progression. Regression analysis of 86 breast reconstructions showed that a body mass index of greater than 30, fat grafting, and highly cohesive anatomic implants decreased rippling, whereas radiation increased capsular contracture (P < 0.05).

CONCLUSIONS

Prepectoral meshed ADM breast reconstruction has an equivalent safety profile to partially submuscular ADM-assisted reconstruction and early aesthetic ratings comparable with other published accounts of implant-based reconstruction. Radiated skin envelopes carry higher capsular contracture rates. Thin patients have a higher risk of visible rippling, whereas fat grafting and higher cohesivity implants are associated with less rippling.

Rabbit as an animal model for the study of biological grafts in pelvic floor dysfunctions

The aims of this study were to evaluate the feasibility of the New Zealand White (NZW) rabbit for studying implanted biomaterials in pelvic reconstructive surgery; and to compare the occurrence of graft-related complications of a commercial polypropylene (PP) mesh and new developed human dermal matrix implanted at vaginal and abdominal level. 20 white female NZW rabbits were randomized into two groups, experimental group (human acellular dermal matrices-hADM-graft) and control group (commercial PP graft). In each animal, grafts were surgically implanted subcutaneously in the abdominal wall and in the vaginal submucosa layer for 180 days. The graft segments were then removed and the surgical and clinical results were analyzed. The main surgical challenges during graft implantation were: (a) an adequate vaginal exposure while maintaining the integrity of the vaginal mucosa layer; (b) to keep aseptic conditions; (c) to locate and dissect the breast vein abdominal surgery; and (d) to withdraw blood samples from the ear artery. The most abnormal findings during the explant surgery were found in the PP group (33% of vaginal mesh extrusion) in comparison with the hADM group (0% of vaginal graft extrusion), p = 0.015. Interestingly, macroscopic observation showed that the integration of the vaginal grafts was more common in the hADM group (40%) than in the PP group, in which the vaginal mesh was identified in 100% of the animals (p = 0.014). The NZW rabbit is a good model for assessing materials to be used as grafts for pelvic reconstructive surgery and vaginal surgery. Animals are easily managed during the procedures, including surgical intervention and vaginal mucosa approach. Additionally, hADM is associated with fewer clinical complications, as well as better macroscopic tissue integration, compared to PP mesh.

The Biointegration of a Porcine Acellular Dermal Matrix in a Novel Radiated Breast Reconstruction Model

BACKGROUND

Ideal acellular dermal matrices (ADM) for breast reconstruction exhibit native extracellular matrix (ECM) structure to allow rapid biointegration and appropriate mechanical properties for desired clinical outcomes. In a novel in vivo model of irradiated breast reconstruction, we describe the cellular and vascular ingrowth of Artia, a porcine product chemically prepared to mimic the biomechanics of human ADM, with retained natural ECM structure to encourage cellular ingrowth.

METHODS

Utilizing the murine dorsal skinfold model, Artia was implanted into 16 C57bl/6 mice. Eight of the mice received a single dose 35 Gy radiation to the skin, followed by 12 weeks to produce radiation fibrosis and 8 mice served as nonradiated controls. Real-time photoacoustic microscopy of vascular integration and oxygen saturation within the ADM were made over 14 days. At 21 days, vascular ingrowth (CD31), fibroblast scar tissue formation (alpha smooth-muscle actin α-SMA, vimentin), and macrophage function (M2/M1 ratio) were evaluated. Scanning electron microscopy images of Artia were produced to help interpret the potential orientation of cellular and vascular ingrowth.

RESULTS

Repeated photoacoustic microscopy imaging demonstrated vascular ingrowth increasing over 14 days, with a commensurate increase in oxygen saturation within both radiated and nonradiated ADM-albeit at an insignificantly lower rate in the radiated group. By day 21, robust CD31 staining was seen that was insignificantly greater in the nonradiated group. Of the fibroblast markers, vimentin expression was significantly greater in the radiated group (P < 0.05). Macrophage lineage phenotype was consistent with remodeling physiology in both radiated and nonradiated groups. Scanning electron microscopy demonstrated transversely organized collagen fibrils with natural porous ECM structure to allow cellular ingrowth.

CONCLUSIONS

Artia demonstrates appropriate biointegration, with increased oxygen saturation by 14 days, consistent with the performance of other collagen substrates in this model. Radiation fibrosis resulted in higher vimentin expression yet did not impact macrophage phenotype while only modestly decreasing Artia biointegration suggesting that ADM may have a role in reconstructive efforts in a radiated setting. Taken together with its enhanced biomechanics, this porcine ADM product is well poised to be clinically applicable to breast reconstruction.

Complications after Perforated versus Nonperforated Acellular Dermal Matrix Use in Direct-to-Implant Breast Reconstruction: A Propensity Score Analysis

Acellular dermal matrices (ADMs) were first incorporated into direct-to-implant (DTI) breast reconstruction by the senior author in 2001 and have since become foundational to implant-based reconstruction. ADM composition has evolved recently and now includes perforated types, which some speculate decrease the likelihood of seroma. The authors performed a retrospective review of perforated (P-ADM) and nonperforated (NP-ADM) ADM-assisted direct-to-implant breast reconstruction patients to evaluate differences in complication rates.

In Vitro Characterization of a Novel Human Acellular Dermal Matrix (BellaCell HD) for Breast Reconstruction

In the past, acellular dermal matrices (ADMs) have been used in implant-based breast reconstruction. Various factors affect the clinical performance of ADMs since there is a lack of systematic characterization of ADM tissues. This study used BellaCell HD and compared it to two commercially available ADMs—AlloDerm Ready to Use (RTU) and DermACELL—under in vitro settings. Every ADM was characterized to examine compatibility through cell cytotoxicity, proliferation, and physical features like tensile strength, stiffness, and the suture tensile strength. The BellaCell HD displayed complete decellularization in comparison with the other two ADMs. Several fibroblasts grew in the BellaCell HD with no cytotoxicity. The proliferation level of fibroblasts in the BellaCell HD was higher, compared to the AlloDerm RTU and DermACELL, after 7 and 14 days. The BellaCell HD had a load value of 444.94 N, 22.44 tensile strength, and 118.41% elongation ratio, and they were higher than in the other two ADMs. There was no significant discrepancy in the findings of stiffness evaluation and suture retention strength test. The study had some limitations because there were many other more factors useful in ADM’s testing. In the study, BellaCell HD showed complete decellularization, high biocompatibility, low cytotoxicity, high tensile strength, high elongation, and high suture retention strengths. These characteristics make BellaCell HD a suitable tissue for adequate and safe use in implant-based breast reconstruction in humans.