Scientific Abstract Presentations: Research & Technology Session 7 Saturday, September 28 Sat, Sep 28 10:30 a.m.-12:30 p.m. PDT

Purpose: Procedures such as replantation and allotransplantation are limited by short muscle ischemia time and hereby resulting in ischemia reperfusion injury and mitochondrial dysfunction with the development of oxygen radicals. The effect of the mitochondria targeting antioxidant drug MitoQ has not been assessed in a rodent hindlimb model before. Materials & Methods: Ischemia was induced through unilateral clamping of the iliac vessels in a rat. Two groups (A, B each n=5) received a MitoQ (4mg/kg) injection IV prior to or after 6 hours of ischemia. Ischemia was followed by 24 hours of reperfusion (endpoint of study). The uptake of MitoQ in the muscle, H/E staining of the muscle as well as blood levels of CK, CRP, WBC and release of mtDNA (via PCR) were assessed and compared to the untreated control group (C, n=5). Results: Preliminary median CK level findings at baseline, 6 hours and 24 hours did not reveal any statistical significance but a trend towards lower CK level after treatment with MitoQ compared to the untreated group (p=0.11, p=0.98, p=0.30). Preliminary mtDNA PCR results failed to show statistical significance (p=0.44, p=0.45, p=0.42) but indicate through all assessed genes a trend towards lower mtDNA content in the treated groups A and B after six hours of ischemia and after six hours of ischemia followed by 24 hours of reperfusion compared to the untreated control group. Conclusion: In summary, these preliminary results reveal a positive effect of MitoQ as compared to the untreated control group in terms of less muscle fiber disruption, lower mtDNA content and lower CK levels. Additional data and statistical tests may be needed to reach statistical significance. These preliminary results serve as a basis for ongoing research and discussion of antioxidant treatment in elective transplant/vascular surgery or trauma settings.

Background. Intervention to manage burn injuries and chronic wounds is a necessity. In these conditions, infection, especially from biofilm-forming bacteria, is a major challenge, because they are reluctant to respond to conventional therapeutic measures. Persister bacteria are antibiotic-tolerant bacterial cells. Mechanisms underlying biofilm formation of such subpopulation of bacteria are different from the general bacterial population. Extracellular DNA (eDNA) is a principal constituent within the biofilm matrix. DNase treatments can eradicate standard biofilms but not persister biofilms. We reported that a DNase resistant biofilm of Pseudomonas aeruginosa can be disrupted by aurine tricarboxylic acid (ATA), a chemical inhibitor of covalent binding between eDNA and protein1. In the current study, we incorporated ATA into a polymer-based gel (Elastogel) to develop a novel wound care dressing (GelATA) that was tested against polymicrobial persister biofilm infection in a preclinical porcine burn wound model. Methods. Standardized burner2 was used to create eight 2"x2" full thickness burn wounds on the dorsum of domestic white pigs (70-80lbs; n=5). The wounds were inoculated at day 3 post-burn with clinical isolates of persister biofilm strains of P. Aeruginosa (PAO1wspF) and S. Aureus (SArexB) at 108 CFU/ml. Wounds were treated with either a standard-of-care dressing (SoC) or GelATA once weekly starting at day 7 post inoculation. On day 28 postburn, GelATA treated wounds was switched to Elastogel alone until day 56. Progression of burn wound healing was followed using; Digital images, Ultrasound Imaging, and measurement of Trans Epidermal Water Loss (TEWL). Histopathology and Scanning Electron Microscopy (SEM) of the tissues were performed on day 56. Results. GelATA treated wounds showed disrupted biofilm formation in SEM images with limited bacterial colonization compared to SOC. Furthermore, GelATA significantly (p<0.05; n=5) enhanced the quality of healing that was evident from early wound closure and re-epithelialization of biofilm-infected wounds (p<0.05; n=5). Improved wound healing with inhibition of biofilm formation resulted in functional healing which was evident by significant decrease in TEWL (p<0.05) signifying improved restoration of skin barrier function. Conclusion. This work presents the first evidence for the efficacy of GelATA in disrupting persister biofilm and promoting functional wound closure in a pre-clinical porcine burn wound model.

References: 1- Deng B, Ghatak S, Sarkar S, et al. Novel Bacterial Diversity and Fragmented eDNA Identified in Hyperbiofilm-Forming Pseudomonas aeruginosa Rugose Small Colony Variant. iScience. 2020;23(2):100827. doi: 10.1016/j.isci.2020.100827 2- Roy S, Elgharably H, Sinha M, et al. Mixed-species biofilm compromises wound healing by disrupting epidermal barrier function. J Pathol. 2014;233(4):331-343. doi:10.1002/path.4360.

Introduction: There is an evolution towards minimally invasive surgery (mis) to treat patients with craniosynostosis with lower morbidity compared to open surgery [1]. These techniques involve suturectomy followed by helmeting or use of springs to mold the cranium. Although effective, certain types of patient presentations still require open surgery including those who present late and some surgeons reserving mis for single suture involvement. Helmet use can be burdensome to families [2] and springs require a second procedure for removal [3]. These limitations of mis approaches may be due to the less extensive osteotomies performed using currently available straight rigid tools with limited incisions. The objective of this research was to develop a novel articulating bone cutting tool that can perform extensive osteotomies along the cranium using a limited access approach, expanding the indications of mis to more patients with craniosynostosis without the need for a molding helmet or springs.

Methods: Computer-aided-design (CAD), three-dimensional (3D) printing and machining was used to develop a prototype of an articulating bone cutting tool. A craniosynostosis simulator that comprises a 3D printed sagittal craniosynostosis skull and silicone scalp was developed to test the tool. A reachability analysis was performed on the simulator comparing the distance between the tool tip and skull along all areas of the skull between a conventional straight instrument and the new tool using a simulated single access incision at the vertex. The ability of the tool to perform osteotomies was tested using biomechanical polyurethane foam sheets with 2 levels of density (30 and 40 pounds-per-cube-foot (PCF), Sawbones) at 2 mm thickness.

Results: A physical prototype was successfully developed that comprises an articulating bending section, a multi-functional end-effector, endoscope and driving unit. The end-effector comprises a scalp retractor, dural protector-dissector, manual bone punch and endoscopic channel for visualization at the tool tip. Simulator testing demonstrated an average tooltip-to-skull distance of 6.04 mm for the straight tool in comparison to the new tool with a range of 6.25 to -14.44 mm passing through 0 mm for 96% of all points. The tool successfully cut the simulated bone at different bending angles (0, 22.5 and 45 degrees).

Conclusions: A novel articulating bone cutting tool was developed. Preliminary ex-vivo testing demonstrated the ability of the new tool to access all areas of the cranium using a single vertex incision as well as the ability to cut simulated bone. The tool represents a potential paradigm shift in the surgical treatment of craniosynostosis expanding the indications of mis surgery to more patients with the integration of surgical robotics and navigation.

References:

1. Goyal A, Lu VM, Yolcu YU, Elminawy M, Daniels DJ. Endoscopic versus open approach in craniosynostosis repair: a systematic review and meta-analysis of perioperative outcomes. Child's Nervous System. 2018;34(9). doi:10.1007/s00381-018-3852-4

2. Uno K, Sakamoto Y, Miwa T. Is Postoperative Helmet Molding Therapy Necessary for Craniectomy for Sagittal Suture Synostosis? J Craniofac Surg. 2024;35(1):111-113. doi:10.1097/SCS.0000000000009819

3. Kalmar CL, Swanson JW, Shakir S, et al. Removal of cranial springs after spring-mediated cranioplasty. Neurosurgical Focus: Video. 2021;4(2). doi:10.3171/2021.1.FOCVID20102

Background The use of regenerative medicine-based approaches for non surgical facial rejuvenation is an emergent trend and many autologous treatments have been proposed with different degrees of invasiveness and results (1,2) Recently this author presented the first clinical report of a new concept for face and neck rejuvenation: a combined use of stem cells and two laser technologies, the wavelength 1450 nm for micro coagulation and the wavelength 980 for stimulation the production of neo-collagen and elastin ( 3)

Objective Objective of this new report was to verify if the results obtained with this technique can modify patients' requests for additional surgical corrections.

Methods We treated 450 patients with mild to high overall cutaneous photodamage and in particular with mild to severe degrees of upper eyelid dermatochalasis and of periorbital rhytides and with mild to severe skin laxity and horizontal skin wrinkles of the neck. Patients received 4 successive laser treatments and stem cells applications at 3 weeks intervals. Clinical improvement of treatment areas was determined by comparative analysis of photographs at baseline and 1, 6, 12 and 24 months post treatment. At each time a specific skin software allows to evaluate wrinkles density, skin dark and light, spot density etc. Skin elasticity measurements were obtained with a cutometer and general patient satisfaction surveys were also obtained at each follow-up visit. Further specific surveys were carried out at each time to monitor the patients' request for additional surgical correction.

Results A greater than 85% clinical improvement in photodamage at different months follow-ups was achieved in nearly 95% patients, confirming previous data. Patients also reported a statistically significant reduction of periocular wrinkles (85%) and dermatochalasis (80%), a statistically significant reduction of the horizontal neck wrinkles (90%) and an improvement of the skin laxity (80%) with stable results over time and a very high patient satisfaction rate. The percentage of patients considering additional surgical correction dropped from 40 % pre treatment to 4 % post treatment. No down time and no side effects were reported. Conclusions This study confirmed the great effectiveness of this new regenerative medicine technique for the rejuvenation of face and the neck with a great patient satisfaction rate and a significant reduction in the patients' request for additional surgical correction.

References

1) Jo H., Brito S., Kwak B.M., Park S., Lee M.G., Bin B.H. Applications of mesenchymal stem cells in skin regeneration and rejuvenation. Int J Mol Sci. 2021;22:2410. doi: 10.3390/ijms22052410.

2) Meruane M.A., Rojas M., Marcelain K. The use of adipose tissue–derived stem cells within a dermal substitute improves skin regeneration by increasing neoangiogenesis and collagen synthesis. Plast Reconstr Surg. 2012;130:53–63. doi: 10.1097/PRS.0b013e3182547e04.

3) Giardini E. Combined use of stem cells and two laser technologies: a new minimally invasive frontier in non surgical rejuvenation of face and neck and the key role of stem cells. Aesthetic Plast Surg. 2023; 47:S260-S261 doi.org10.1007/s00266-023-03449-1.

Background: Ischemic necrosis in the distal portion of the flap is a challengingcomplication in plastic surgery. We hypothesize a novel hybrid flap preconditioning(HFP) device combining foam-mediated external suction and non-surgical delay canpromote skin flap survival better than surgical delay. Method: Twenty-eight mouse were divided into four groups. Control group: a 4*1.5dorsal flap was made with no preconditioning. Surgical delay (SD) group: surgicaldelay was made 7 days before flap elevation. Foam-mediated external suction (FMES)group: foam-mediated external suction at -100mmHg was employed 5 hours per dayfor 6 days, and the flap was elevated on the seventh day. Hybrid Flap Preconditioning(HFP) group: silicone strips was applied along the contour of the foam interface. Samenegative pressure protocol was used as the FMES group. Seven days after flapelevation, macroscopic, histologic, and Western blot analyses were performed. Results: The flap survival rate was 46.25% (8.12%) in the control group, 68.72%(7.00%) in the SD group, 57.03% (8.17%) in the FMES group and 80.66% (3.27%) inthe HFP group. Immunohistologic analysis of CD 31+ cell in distal end of viable tissueprocured seven days after flap elevation showed a significantly higher angiogenesis inSD group and HFP group. Western Blot results showed an increased expression ofVEGF in SD group and HFP group. Conclusion: We have developed and fabricated a novel hybrid flap precondition (HFP)device combining foam-mediated external suction and non-surgical delay. The conceptof HFP is proved to promote flap survival better than surgical delay.

Abstract: Introduction: The last three decades have witnessed a monumental shift in regenerative medicine, with autologous fat grafting and adipose-derived stem cells (ASCs) at the forefront of transforming plastic surgery practices. This evolution is largely credited to the seminal contributions of Dr. Arnold Caplan in the field of mesenchymal stem cells (MSCs), which have bridged the gap between theoretical research and practical clinical application. Materials and Methods: We introduce the micro-autologous fat transplantation (MAFT) technique, an innovative approach devised to minimize central necrosis in fat grafts. This technique allows for the precise and uniform delivery of fat parcels, effectively addressing the challenges of central necrosis and enhancing overall graft viability. Our analysis of over 6,000 cases, encompassing both aesthetic and reconstructive surgeries, sheds light on the clinical advantages, navigates the complexities encountered, and highlights the critical role of the transplantation process in improving long-term outcomes. Results: The adoption of MAFT, coupled with the integration of ASCs and stromal vascular fractions (SVFs), has significantly elevated the success rate of fat grafting by promoting an environment favorable for neovascularization. Despite these advancements, the journey towards widespread adoption is impeded by regulatory barriers, procedural complexities, and the necessity for standardization and specialized equipment. Conclusion: Our findings advocate for a cutting-edge, integrated approach that merges the MAFT technique with compliant methods for SVF isolation to significantly advance regenerative outcomes in plastic surgery. This strategy not only highlights the synergy between volume restoration and cellular therapies but also establishes a new paradigm for achieving enduring and superior clinical results. Future research should focus on refining the MAFT technique to enhance graft survival and expand its application in diverse clinical scenarios. Embracing technologies such as artificial intelligence and 3D printing could further revolutionize the precision and outcomes of these procedures. Ongoing long-term and comparative studies are paramount in affirming MAFT's pivotal role in enriching aesthetic and regenerative surgery, ensuring safer, more efficient, and tailored patient care.

References: 1. Cartilage begets bone versus endochondral myelopoiesis. AI Caplan. Clin Orthop Relat Res 1990 Dec:(261):257-67. 2. Multilineage cells from human adipose tissue: implications for cell-based therapies. Zuk PA, Zhu M, Hedrick MH et al. Tissue Eng. 2001 Apr;7(2):211-28. 3. Cell-assisted lipotransfer: supportive use of human adipose-derived cells for soft tissue augmentation with lipoinjection. Daisuke Matsumoto, Katsujiro Sato, and Kotaro Yoshimura et al. Tissue Eng 2006 Dec;12(12):3375-82. 4. Accelerated growth and prolonged lifespan of adipose tissue-derived human mesenchymal stem cells in a medium using reduced calcium and antioxidants. Lin TM, Tsai JL, Lin SD, Lai CS, Chang CC. Stem Cells Dev. 2005 Feb;14(1):92-102. 5. The legacy of micro-autologous fat transplantation (MAFT) – Reality from evidence-based medicine. TM Lin, H Takahashi, CK Chou. In: Chapter 14: A Di Giuseppe, F Bassetto, F Nahai (eds): Fat Transfer in Plastic Surgery: Techniques, Technology and Safety. 2023.

Purpose: Burns have considerable potential to impact mental health due to associated pain, scarring, and disability. However, the long-term impact of burns on mental health is understudied. Our purpose was to assess the association between burns and mental health hospitalization up to 30 years later. Methods: Using a longitudinal cohort design, we compared 23,726 burn patients aged ≥10 years with 223,626 matched controls from Quebec, Canada, between 1989 and 2022. The main exposure was a burn severe enough to require hospital treatment. We identified future hospitalizations for psychiatric disorders, substance use disorders, and suicide attempts up to 30 years after the burn. We used adjusted Cox regression models to estimate hazard ratios (HR) with 95% confidence intervals (CI) for the association between burns and subsequent mental health hospitalization. Results: Compared with controls, burn patients were 1.76 times more likely to be hospitalized for mental health disorders over time (95% CI 1.72-1.81). Burns covering ≥50% of the body (HR 3.29, 95% CI 2.61-4.15), third degree burns (HR 2.04, 95% CI 1.94-2.14), and burns requiring skin grafts (HR 2.00, 95% CI 1.90-2.10) were more strongly associated with mental health hospitalization. Compared with controls, burn patients were more than two times as likely to be hospitalized for eating disorders (HR 3.14, 95% CI 2.50-3.95), substance use disorders (HR 2.27, 95% CI 2.17-2.39), and suicide attempts (HR 2.42, 95% CI 2.23-2.62). Risks were highest in the first 5 years following a burn, but associations remained present up to 30 years later. Conclusions: Burns are associated with the long-term risk of mental health hospitalization up to 30 years later, with more pronounced associations for patients with severe burns. Scarring, pain, and functional impairment may contribute to the impact that burns have on mental health. Involving mental healthcare teams early after a burn may prevent mental health complications over time.

Background: Chitosan oligosaccharides (COS), derived from the natural polysaccharide chitin in crustacean shells, are known for their biocompatibility, angiogenetic, anti-bacterial and anti-inflammatory effects in vitro. However, the intricacies of in vivo wound healing require further exploration. This study aimed to evaluate the effect of COS on wound healing and to assess their antimicrobial activity in vivo. Methods: Two types of COS, namely COS-h from high-molecular weight chitosan hydrolysis and COS-w from water-soluble chitosan, were investigated for their antibacterial efficacy against methicillin-resistant Staphylococcus aureus. Subsequently, 48 full-thickness wounds were created in the BALB/c nude mice. The wounds were treated with COS-h, COS-w, or phosphate-buffered saline as controls. After two weeks, the healing progress was evaluated by measuring the unhealed wound areas. Collagen synthesis and the production of vascular endothelial growth factor and transforming growth factor-β were quantified using enzyme-linked immunosorbent assays and immunohistochemistry. Results: COS application markedly improved the wound healing parameters. Notably, COS-h treatment significantly reduced unhealed wound areas (P < 0.05) and displayed potent antimicrobial activity. It also promoted higher collagen synthesis and more substantial wound contraction than COS-w. Conclusion: COS-h may have the potential to accelerate wound healing by enhancing antimicrobial activity, collagen synthesis, and wound contraction.

Acknowledgements: This study was supported by grants from a National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (No. 2021R1C1C1008674) and Korea University Guro Hospital grant (KOREA RESEARCH-DRIVEN HOSPITAL) funded by Korea University Medicine (No. K2210441). The author disclose no other financial relationships related to this article.

Conflict of Interest Statement The authors declare no conflicts of interest regarding this study.

References 1. Kim S. Competitive biological activities of chitosan and its derivatives: antimicrobial, antioxidant, anticancer, and anti-inflammatory activities. International journal of polymer science. 2018;2018 2. Abd El-Hack ME, El-Saadony MT, Shafi ME, et al. Antimicrobial and antioxidant properties of chitosan and its derivatives and their applications: A review. Int J Biol Macromol. 2020;164:2726-2744 3. Namgoong S, Yoon I-J, Han S-K, Son J-W, Kim J. A pilot study comparing a micronized adipose tissue niche versus standard wound care for treatment of neuropathic diabetic foot ulcers. Journal of Clinical Medicine. 2022;11(19):5887 4. You H-J, Namgoong S, Han S-K, Jeong S-H, Dhong E-S, Kim W-K. Wound-healing potential of human umbilical cord blood–derived mesenchymal stromal cells in vitro-a pilot study. Cytotherapy. 2015;17(11):1506-1513 5. Namgoong S, Lee H, Han SK, Lee HW, Jeong SH, Dhong ES. Effect of Panax ginseng extract on the activity of diabetic fibroblasts in vitro. Int Wound J. 2019;16(3):737-745

Purpose It is known that repeated deformation of skin tissue during the healing process, such as stretching and contraction, accelerates scar formation. Therefore, we conceived the idea of suppressing wound contraction by reinforcing the wound with a high-density collagen frame. We report the development of an artificial dermis with a reinforcing collagen frame (CF) that has an internal fixation effect on wounds and does not inhibit wound healing. Materials and methods Using only biodegradable collagen, we aimed to balance tissue replaceability and mechanical support. In this study, we created a Frame-reinforced Collagen Matrix (FCM) by incorporating a strengthened CF made using collagen densification technology as the skeletal structure within artificial dermis. The inhibitory effects of FCM on scar formation and scar contracture were evaluated through mouse experiments. FCM was implanted subcutaneously in ICR mice on their dorsal region, and histological changes were examined. Subsequently, 11 mm skin-defect wounds were created on the dorsal region of C57BL/6JJcl mice, and FCM along with full-thickness skin grafting was performed simultaneously. The engraftment, size, and histological changes of the grafts were examined at 7, 14, and 28 days post-transplantation, with existing artificial dermis and collagen without CF (CM) serving as the control group. Results We have successfully created porous artificial dermis by lyophilizing and cross-linking 3% and 20% collagen slurries (CM-3; density 30 mg/cm3, CM-20; density 200 mg/cm3). The incorporation of a high-density frame structure into a low-density collagen matrix improved the overall mechanical strength and shrinkage resistance. In a subcutaneous transplantation experiment in the back of a mouse, CM-3 showed approximately 50% degradation and resorption only one week after implantation, and cell and tissue infiltration was observed. On the other hand, CM-20 maintained its shape almost completely even after 8 weeks. When FCM incorporating honeycomb-shaped CF was transplanted into the skin defect layer of mouse back skin, granulation tissue formation and vascular infiltration were observed preferentially in CM-3 (low-density collagen matrix), while the skeletal structure of CM-20 maintained its shape even after 2 weeks. and significantly reduced scar contracture compared to existing CM at 2 weeks. Conclusions We have devoted ourselves to the development of an artificial dermis using only collagen, with an emphasis on safety and feasibility. Our results suggest the possibility of combining two types of collagen with different densities to achieve both tissue replacement and mechanical support. In other words, it was shown that it is possible to induce granulation tissue formation while expecting scar contracture suppression. Future studies are aimed at collaborating with engineering researchers to explore the optimal volume occupancy of reinforced collagen frames, cellular dynamics, and their effect on wound healing, and to compare long-term outcomes.

Background: Diabetic foot ulcers (DFUs) are recalcitrant to healing. However, the molecular mechanism causing this dysfunction is not fully understood. DNA methylation profiles change during the proliferation, differentiation, and development of an organism, resulting in tissue or disease identification. To elucidate the biomarkers for DFU prognosis, we hypothesized that differences in DNA methylation patterns could provide important therapeutic targets in the treatment of DFUs. Methods: We collected 48 blood samples from 36 DFU patients treated at Korea University Guro Hospital from October 2019 to November 2021. The Illumina MethylationEPIC (850k) DNA methylation microarray was used to determine the pattern between differentially methylated regions (DMRs) in DFU patients with good or poor prognoses. We then selected and visualized the DMRs in the form of heatmaps, and enriched terms associated with these DMRs were identified. By using the DMR list in two processes, Kyoto Gene and Genome Encyclopedia (KEGG) and gene ontology (GO) analysis, gene-concept network, GSEA, and decision tree were performed. Results: In total, 92 DMRs and 108 DMRs (|Log2 fold change| > 0.1 and P < 0.03) were hypermethylated and hypomethylated, respectively. In the good prognosis sample, 69 and 156 DMRs were hypermethylated and hypomethylated, respectively. In the KEGG analysis, the MAPK signaling pathway was commonly detected as the highest pathway. In the decision tree, MORN1 hypomethylation and NCOR2 hypermethylation were crucial classifiers by recurrence. Conclusion: Collectively, MORN1 and NCOR2 genes may be used as biomarkers for predicting the recurrences and prognosis in DFU patients. In DFUs, the clues of recurrence and prognosis prediction may be provided through DMRs and the molecular mechanisms related to inflammation.

Acknowledgments This study was supported by grants from a National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (No. 2021R1C1C1008674) and Korea University Guro Hospital grant (KOREA RESEARCH-DRIVEN HOSPITAL) funded by Korea University Medicine (No. K2210441). The author discloses no other financial relationships related to this article.

Background. Facial burn injuries cause scars and contractures that are not only responsible for disfigurement but also severe functional impairment affecting quality of life. The patients will suffer permanent facial disfigurements even with multiple complex reconstructive surgeries Conventional scar management has not worked for the management of face burn. We set up a pre-clinical face burn model. This was followed by genome wide sequencing studies which led to identification of novel molecular targets for intervention. FDA approved drugs were screened to identify two drugs (D1 & D2) for topical treatment during the early (day 14- 41) and late (day 42-84) post-burn phases.
Methods. White Yorkshire pigs (70-80lbs) were subjected to sever full thickness facial burn trauma (~50% face). Facial burn was treated with either a standard-of-care dressing (SoC) (n=5) or topical FDA repurposed drugs (n=5) twice weekly until d84. Progression of burn wound healing and scar formation was followed using a) digital photography b) laser speckle microperfusion imaging (LSI); c) Harmonic Ultrasound Imaging with Doppler (HUSD) for biomechanics; and d) CT for 3D reconstruction of the facial soft tissues and bone. Histopathological examination of the burn wounds and scar tissues was performed. Results. Severe facial burn with bone involvement showed raised scars/contractures, cicatricial ectropion, eversion of the oral mucosa and lip (drooling), and orofacial contracture. Vascular and bone deficits (n=5) were characterized using LSI, HUSD and CT imaging. Objective scar analysis revealed a significant improvement in wound healing, reduced total scar areas and less skin contractures in drug-treated group compared to the control (n=5; p<0.01). A significant reduction of cictertial ectropion and oral eversion (improved oral competence) was observed in drug treated pigs. Tissue analyses revealed significant decrease in myofibroblast formation with normally distributed blood vessels in drug-treated group compared to the control (n=5; p<0.01). Overall, the post-burn face appeared markedly better in response to treatment. Conclusion. This work presents a highly relevant preclinical model to study severe facial scar contractures and related outcomes. Bioinformatic studies led to identification of candidate pathways for intervention which was followed by the successful repurposing use of FDA-approved drugs towards marked improvement of burn outcomes.

Introduction: Wound healing is marked by an initial stage of inflammation, in which immature myeloid cells and neutrophils migrate to tissues in response to cytokines and chemokines secreted by cells within the wound. The immature cells then undergo differentiation into mature myeloid cells and neutrophils become activated. Serine/Threonine Protein Kinase 25 (STK25) is a positive regulator of pro-inflammatory cytokine release and myeloid activation and has been linked to an attenuated inflammatory response in STK25-deficient mice (1) (2). Inversely, an overactive neutrophil response can lead to prolonged inflammation and chronic wounds or scarring (3). While it is also thought to affect cell migration, this has not yet been proven.

Methods: STK25 deficient mice on a C57Bl/6 background, with corresponding, age- and sex-matched, wild-type littermate mice were wounded with two full-thickness punch biopsies. The wound area was calculated using the MolecuLight DXTM camera's wound measurement function. Wound healing was measured as wound area reduction at postoperative day 7. Wounds were collected en bloc on postoperative day 7 and then processed into a single cell suspension and stained for flow cytometry analysis.

Results: Wild-type mouse wounds were smaller in size on day 7 compared to STK25-deficient mice. Flow cytometry analysis revealed a significantly lower percentage of neutrophils in the STK25-deficient mice compared to wild-type mice. Absolute cell counts of macrophages, neutrophils, and inflammatory monocytes were decreased in STK25-deficient mice compared to wild-type mice.

Conclusion: Wound healing and the immune response are impaired in STK25-deficient mice compared to wild-type. Less immune cells had trafficked to the wound by day 7 with neutrophils appearing to be the most affected. While lack of initial neutrophil migration impairs wound healing, inhibition of neutrophils later in the wound healing process could be beneficial. Neutrophil apoptosis at the site of injury leads to the release of cytokines that further damage tissues and activate inflammatory cells (4). Inhibition of neutrophils in chronic wounds may therefore enable reprogramming of the wound to undergo healing, however, more study is needed.

Citations:

1. Matthew Rice, Bharati Matta, Betsy J Barnes. STK25 acts as a regulator of leukocyte migration. J Immunol. 1 May 2022; 208 (1 Supplement): 105.32. https://doi.org/10.4049/jimmunol.208.Supp.105.32
2. Matthew R Ricke, Cherrie D Sherman, Betsy J Barnes. STK25 functions as an IRF5 kinase to promote TLR7/8 mediated inflammation. J Immunol. 1 May 2022; 208 (1_Supplement): 52.15. https://doi.org/10.4049/jimmunol.208.Supp.52.15
3. Wilgus TA, Roy S, McDaniel JC. Neutrophils and Wound Repair: Positive Actions and Negative Reactions. Adv Wound Care (New Rochelle). 2013 Sep;2(7):379-388. doi: 10.1089/wound.2012.0383. PMID: 24527354; PMCID: PMC3763227.
4. Kruger P, Saffarzadeh M, Weber AN, et al. Neutrophils: Between host defence, immune modulation, and tissue injury. PLoS Pathog. 2015;11(3):e1004651. Published 2015 Mar 12. doi:10.1371/journal.ppat.1004651

Introduction  Severe volumetric muscle loss (VML) due to traumatic loss of skeletal muscle can result in permanent functional impairment and chronic disability in up to 65% of patients [1]. Therapies for muscle regeneration and functional recovery such as intensive physical therapy are limited in their effectiveness and clinical applicability in severe VML due to the polytraumatic nature of the injury [2]. Our prior work on rats demonstrated that mechanical stimulation of muscles promotes functional recovery (26% higher torque), improves angiogenesis, and decreases fibrosis following VML. Based on the outcomes obtained in the rodent study, we hypothesized that mechanical stimulation also improves recovery in a large animal model of VML.   

Materials and Methods  Surgically induced injury to the left peroneus tertius muscle (PTM) in female (36-42 kg) Yucatan pigs (n=4) served as the model for VML. Post-injury, animals either received no treatment (n=2) or were subjected to mechanical stimulation of the PT muscle (n=2). To evaluate functional recovery, this study utilized measurements of pre-operative and post-treatment isometric tetanic torque and resistance to fatigue. Weekly assessments of gait were scored using the modified Tarlov scale, and the animal's level of activity was measured by recording daily number of steps using a pedometer for approximately 6-weeks post the acclimatization period of the pig. Samples of the injured PTM were collected and are being processed for histology (Masson) to measure myocyte/fibrosis percentage composition.

Results  On post-injury day (PID) 35, the isometric tetanic torque in the treated (mechanically stimulated) group had a significantly higher recovery compared to the control (23% +/- 0.1 of pre-injury baseline vs. 12% +/- 0.2, p=0.0004). The resistance to fatigue in the treated group was higher than in controls (37% of pre-injury baseline vs. 26%). In the treated group, the activity levels during and after treatment were significantly higher than the first 2-days post-VML injury (497 steps and 477 steps, respectively compared to 100 steps post-VML, p-value=0.005). There was no significant difference in the post-VML gait score between the treated and control groups (4.4 +/- 0.1 vs. 4.3 +/- 0.1, p=0.8).  

Conclusions  Mechanical stimulation seems to promote functional recovery after VML injury in large animals. These outcomes should be validated in a larger cohort of animals, and in preliminary clinical trials. 

References: 1. Corona, Benjamin T., Jessica C. Rivera, Johnny G. Owens, Joseph C. Wenke, and Christopher R. Rathbone. "Volumetric Muscle Loss Leads to Permanent Disability Following Extremity Trauma." Journal of Rehabilitation Research and Development 52, no. 7 (2015): 785–92. https://doi.org/10.1682/jrrd.2014.07.0165. 2. Greising, Sarah M., Christopher L. Dearth, and Benjamin T. Corona. "Regenerative and Rehabilitative Medicine: A Necessary Synergy for Functional Recovery from Volumetric Muscle Loss Injury." Cells Tissues Organs 202, no. 3–4 (2016): 237–49. https://doi.org/10.1159/000444673.

Purpose: to evaluate whether responses from ChatGPT and other LLMs could provide comparable quality, accuracy, and empathy to physician answers after controlling for potentially confounding variables such as the length of responses.

Method: This cross-sectional study used RealSelf.com, an online public platform where patients pose questions publicly, which are answered by verified physicians in non-anonymous accounts. Questions from the site were entered as prompts into ChatGPT and Bard and the responses were compared to the responses from physicians on RealSelf.com. Three blinded physicians evaluated matchups between different response pairs (i.e. RealSelf vs. ChatGPT, RealSelf vs. Bard, or ChatGPT vs. Bard). They chose "which response was better" and rated the quality, accuracy, and empathy of each response. The next generation generative AI bot, MedLM was also tested. MedLM was designed for healthcare and built on Med-PalM2 that had previously scored an 85% on the USMLE.

Results: Initial data indicates that physician responses trended higher than ChatGPT scores, but did not show significant difference. Physician responses were significantly higher quality, more accurate, and more empathetic than Bard responses. However, ChatGPT responses, while trending higher than Bard responses, were not significantly higher. The proportion of responses with unacceptable quality, accuracy, and empathy was indistinguishable between physicians, ChatGPT and Bard. MedLM is currently being tested.

Conclusions: In this study, after accounting for verified physician responses and response length, ChatGPT and Bard generated acceptable quality, accurate and empathetic responses to patient questions posed in an online forum. However, overall the physician answers were preferred over chatbot responses in 1:1 matchups.

Purpose: Patient Reported Outcome Measures (PROMs) have shown high sensitivity in detecting lymphedema symptoms prior to current clinical metrics. However, a diagnostic threshold for lymphedema-specific PROMs has not been yet established. The purpose of this study was to suggest an optimal diagnostic cutoff and determine the sensitivity and specificity of lymphedema-specific PROMs in lymphedema diagnosis. Methods: Between 2014 and 2024, we performed arm volume and bioimpedance measurements in patients at a tertiary cancer center. The Lymphedema Life Impact Scale (LLIS) and ULL27, validated lymphedema-specific questionnaires were administered during each visit. Survey scores were compared to volume measurements (volume differential=10%) and bioimpedance scores (LDEX=6.5) to generate receiver operator characteristic (ROC). Youden's method was used to determine the optimal cutoff scores and the sensitivity and specificity of LLIS for lymphedema diagnosis. Results: 1482 patients were included. Using volume differential as diagnostic criteria, The LLIS was highly accurate (AUC=0.723, 95% CI 0.634-0.782, p<0.001) in diagnosing lymphedema with a sensitivity of 67.2%, and specificity of 68.9% at a cutoff of LLIS=37.2% overall percent impairment score. The same cutoff of was determined using bioimpedance scores as diagnostic criteria with high accuracy (AUC=0.782, 95% CI 0.673-0.799, p<0.001), sensitivity of 64.2% and specificity of 77.8%. The ULL27 was less accurate compared to the LLIS (AUC=0.613, 95% CI 0.438-0.882, p<0.001) with a sensitivity of 59.2%, and specificity of 62.9% at a cutoff of LLIS=32.1% physical impairment score. A slightly different cutoff was determined using bioimpedance scores as diagnostic criteria with similar accuracy (AUC=0.681, 95% CI 0.573-0.875, p<0.001), sensitivity of 55.2% and specificity of 62.8%. Conclusion: This is the largest study to date to provide a numeric diagnostic threshold for lymphedema-specific PROMs. Early-stage diagnosis by using PROMs prior to measurable volume changes would enable us to focus on secondary prevention efforts such as early referral to physical therapy and early surgical interventions.

Background: Plastic and reconstructive surgery is one of the most competitive residency programs. This is exacerbated by the increasing number of applicants for a relatively stagnant number of residency positions. The rate of successfully matching has declined since 2018, with a match rate of ~55% in 2022. Two common strategies before reapplying are a preliminary year of residency (preliminary year) or a research fellowship. The purpose of this study was to investigate which option is more beneficial for reapplicants pursuing a successful match and to analyze the impact of research fellowship duration, location of preliminary year or research fellowship, and if there are any nuances for international medical graduate (IMG) reapplicants.

Materials & Methods: This retrospective study included all applicants to an integrated plastic and reconstructive surgery residency from 2015-2023. Two cohorts based on reapplication strategy (research fellowship or preliminary year) were created. Demographic, applicant, and match data were collected. Pearson's Chi-squared, Fisher's exact, and Wilcoxon rank sum testing were performed.

Results: 125 reapplicants were included. 71 (56.8%) reapplicants pursued a preliminary year, and 29 (23.2%) completed a research fellowship. There was no statistically significant difference in demographic data between cohorts. Research fellowship reapplicants had a greater mean number of first author publications (8.8 vs 3.2, p < 0.001), non-first author publications (11.3 vs 5.9, p = 0.021), poster presentations (9.7 vs 6.0, p = 0.028), and oral presentations (11.8 vs 6.4, p < 0.001). There was no statistically significant difference between Step scores or number of application attempts between cohorts. Research fellowship reapplicants were more likely to match into plastic surgery than preliminary year reapplicants, with 72.4% (n = 21) of research fellowship reapplicants matching into plastic surgery compared to 39.4% (n = 28) of preliminary year reapplicants (p = 0.003). There was no statistically significant difference between research fellowship reapplicants who did one research year compared to two years in terms of match success. When compared to preliminary year reapplicants, both one-year (68.4% vs 39.4%, p = 0.024) and two-year (80.0% vs 39.4%, p = 0.020) research year reapplicants matched at a greater rate to a statistically significant degree. When analyzing IMG reapplicants who matched into any specialty, 30.0% (n = 3) of IMG preliminary reapplicants matched into plastic surgery compared to 100% (n = 6) of IMG research fellowship reapplicants (p = 0.011). All reapplicants were more likely to match at programs other than where they pursued either their preliminary year or research fellowship, as 71.4% (n = 35) of matched reapplicants matched at other institutions (p = 0.002).

Conclusions: Research fellowship reapplicants demonstrated greater research productivity and were almost twice as likely to match into plastic surgery compared to preliminary reapplicants. IMG research fellowship reapplicants also demonstrated increased match success compared to IMG preliminary year reapplicants. Simultaneously, the majority of reapplicants match at locations other than where they completed their research fellowship or preliminary year. Lastly, only one year of research appears necessary for reapplicants.

Background: Improving diversity within plastic and reconstructive surgery (PRS) trainees is a crucial step to reduce inequities at the provider level (1). Trends in minority representation among independent program match applicants are understudied. We analyzed gender, racial, and ethnic trends among independent PRS match applicants across 2013 to 2023.

Methods: With the approval of the American Council of Educators in Plastic Surgery, the San Francisco Match provided data for the independent PRS match from 2013 to 2023. Trends in the independent PRS match were reviewed, and a Cochran–Armitage test was conducted to evaluate the significance of match trends in minority applicants (Female, non-White, Hispanic) over time.

Results: A total of 1000 applicants participated in the independent plastic surgery match from 2013 to 2023, of whom 735 matched. The number of independent PRS programs decreased from 54 to 37. The match rate decreased from 86% to 60%. For the years 2014, 2016, and 2018, the proportion of non-White applicants was significantly higher than matched participants of the same year (p=0.001, p=0.027, p=0.023; respectively). The proportion of female applicants and Hispanic applicants correlated yearly to the number of matched females and Hispanics, respectively (p>0.05). Cochran–Armitage tests showed significant differences in match trends among female (p=0.004) participants over time.

Conclusions: We show a significant increase in female representation in the independent PRS match in the last decade. Non-White applicants remain underrepresented within the field. Ongoing efforts are needed to identify barriers and reduce inequities.

Reference: 1. Silvestre J, Serletti JM, Chang B. Racial and Ethnic Diversity of U.S. Plastic Surgery Trainees. J Surg Educ. 2017;74(1):117-123. doi:10.1016/j.jsurg.2016.07.014

Background:

Robot-assisted microsurgery is gaining increasing clinical importance as we push the boundaries of supermicrosurgery. With the ability to compensate for physiological limitations in microsurgical dexterity and potential to enable remote microsurgery in the future, robotics hold great promise to revolutionize the standards of microsurgery. However, successful clinical integration and optimization will strongly depend on specific user training and evaluation. This study aimed to develop and verify automated, practical tools that enable qualitative assessment of both manual and robotic microsurgical performance.

Methods:

Two deep convolutional neural network-based computer algorithms were developed to facilitate computer-assisted 1. tracking of microsurgical instruments and 2. evaluation of anastomosis quality. The first algorithm employed a combination of supervised and semi-supervised learning to train models to track both needle driver and forceps in recorded microsurgical videos. A trajectory was plotted based on the tracked area of interest and neighboring tracked points subsequently averaged to a smooth trajectory. Tremor-movements of both instruments at each instant in time were measured as the absolute deviation from the smooth trajectory. The second algorithm was trained to detect anastomosis stitches and tears as well as metrics of the stitches, while filtering out common nuisance variabilities, such as glares and noise, in images of the everted anastomoses. Both algorithms were used to verify 180 microvascular anastomoses (90 manual and 90 robot-assisted anastomoses) performed by participants with different levels of microsurgical experience in a two-center approach. For robot-assisted anastomoses the Symani surgical system (Medical Microinstruments Inc.) was used in combination with the RoboticScope (BHS Technologies).

Results: Both computer algorithms were successfully developed and verified, enabling both manual and robotic microsurgical self-assessment. Both models worked efficiently without the need for any tracking sensors or markers. Application of the microsurgical instrument tracking algorithm in our study population revealed a markedly higher overall degree of tremor in manually performed compared to robot-assisted anastomoses. The algorithm for anastomosis quality assessment allowed for reliable evaluation of 1) estimates of the anastomosis line, accounting for any disruptions, 2) distance between stitches, accounting for unequal distancing of sutures, 3) angles of each stitch, accounting for oblique stitches causing distortion, and 4) visible tears in vessel wall (Figure 1)

Conclusion: Microsurgical assessment is essential for microsurgical skill development, however, necessitates intensive time and personnel resources to be done effectively. Robotic microsurgery involves technology-related learning curves for surgeons of all experience levels, and thus requires time-efficient, practical, and accurate evaluation methods specific to robotic surgical paradigms. We established two completely automated algorithms for reliable skill self-assessment applicable to both conventional and robotic microsurgery. These algorithms not only make microsurgical assessment much more accessible but can substantially accelerate the process of robotic training and evaluation, ultimately promoting their integration in clinical microsurgery.

Introduction : The gold standard for ex vivo preservation of vascularized composite allotransplants (VCAs) remains immersion in 4°C solutions. The muscular component of VCAs is highly susceptible to ischemic injury after a few hours. The use of subnormothermic perfusion machine (SNPM) is a promising approach for VCA preservation. Numerous studies have been conducted in rats and pigs. For the first time, we report the use of SNMP on the upper limbs of cynomolgus monkeys for 24 hours.

Material and methods: The forearms were harvested in non-human primates (NHPs) weighing between 5 and 8 kg. Two perfusion protocols were implemented. In the first group (n=6), a recirculating Steen perfusate was used for 24 hours, aiming at a stable pressure of 40mmHg. After an intermediate analysis, a second group (n=6) was perfused under a stable low-flow regimen with an enhanced oncotic pressure Steen+ solution that was exchanged at mid-perfusion. Experiments were conducted at room temperature for 24 hours. Pressure, flow, weight, and arterial and venous metabolic parameters (lactates, pH, glucose, O2, CO2, ions) were measured. VCA biopsies were performed before and after perfusion in both groups, and in group 2, response to neurostimulation was also investigated.

Results : The mean warm ischemia time (WIT) of the limbs was 3 hours. After 24 hours of continuous SNMP, mean weight gain was 24,8 ± 5,5 % in group 1 and 8,0 ± 4,7 % in group 2. Perfusion and metabolic parameters indicated the onset of compartment syndrome in group 1 with an increase in resistance, lactate and potassium production at mid-perfusion after a mean weight increase of 11.3%. In group 2, resistance, oxygen consumption, lactate and potassium production remained stable for 24 hours, consistent with a state of metabolic equilibrium. Histological analysis proved to be within the normal range, with no difference before and after perfusion in group 2. In group 2, control limbs with only 3 hours of WIT didn't respond to median nerve stimulation, whereas all perfused limbs exhibited muscular contraction quantified at a mean 2,4/5 +/- 0,89 after 24 hours of SNMP.

Conclusions : We present the first application of continuous SNMP to the NHP forearm. These results contribute to a better understanding of the model's perfusion kinetics and physiology, showing promising outcomes in this clinically relevant experimental model. Limb preservation was achieved for 24 hours and muscular contractibility was restored by the SNMP.