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Pomahac, Bohdan

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Pomahac

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Pomahac, Bohdan
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Now showing 1 - 10 of 10
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    Noninvasive Vascular Images for Face Transplant Surgical Planning
    (Open Science, 2011) Soga, Shigeyoshi; Wake, Nicole; Bueno, Ericka M.; Steigner, Michael; Mitsouras, Dimitrios; Schultz, Kurt; Diaz-Siso, J. Rodrigo; Sisk, Geoffroy Courcelle; Prior, Richard; Powers, Sara L.; Signorelli, Jason; Jania, Camille K.; Pomahac, Bohdan; Rybicki, Frank John
    Objective: Face transplantation replaces substantial defects with anatomically identical donor tissues; preoperative vascular assessment relies on noninvasive imaging to separate and characterize the external carotid vessels and branches. The objective is to describe and illustrate vascular considerations for face transplantation candidates. Methods: Novel noninvasive imaging using computed tomography and magnetic resonance imaging over 3 spatial dimensions plus time was developed and tested in 4 face transplant candidates. Precontrast images assessed bones and underlying metal. Contrast media was used to delineate and separate arteries from veins. For computed tomography, acquisition over multiple time points enabled the computation of tissue perfusion metrics. Time-resolved magnetic resonance angiography was performed to separate arterial and venous phases. Results: The range of circulation times for the external carotid system was 6 to 14 seconds from arterial blush to loss of venous enhancement. Precontrast imaging provided a roadmap of bones and metal. Among the 4 patients, 3 had surgical clips, metal implants, or both within 1 cm of major vessels considered for surgery. Contrast-enhanced wide area detector computed tomographic data acquired in the axial mode separated these structures and provided arterial and venous images for planning the surgical anastomoses. Magnetic resonance imaging was able to distinguish between the large vessels from the external carotid systems. Conclusions: Vascular imaging maps are challenging in face transplantation because of the rapid circulation times and artifact from the initial injury, prior reconstructive attempts, or both. Nevertheless, face transplant candidates require high spatial and temporal resolution vascular imaging to determine those vessels appropriate for surgical anastomoses.
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    A Bio-Inspired Swellable Microneedle Adhesive for Mechanical Interlocking with Tissue
    (2013) Yang, Seung Yun; O'Cearbhaill, Eoin D.; Sisk, Geoffroy Courcelle; Park, Kyeng Min; Cho, Woo Kyung; Villiger, Martin; Bouma, Brett; Pomahac, Bohdan; Karp, Jeffrey
    Achieving significant adhesion to soft tissues while minimizing tissue damage poses a considerable clinical challenge. Chemical-based adhesives require tissue-specific reactive chemistry, typically inducing a significant inflammatory response. Staples are fraught with limitations including high-localized tissue stress and increased risk of infection, and nerve and blood vessel damage. Here, inspired by the endoparasite Pomphorhynchus laevis which swells its proboscis to attach to its host’s intestinal wall, we have developed a biphasic microneedle array that mechanically interlocks with tissue through swellable microneedle tips, achieving ~ 3.5 fold increase in adhesion strength compared to staples in skin graft fixation, and removal force of ~ 4.5 N/cm2 from intestinal mucosal tissue. Comprising a poly(styrene)-block-poly(acrylic acid) swellable tip and non-swellable polystyrene core, conical microneedles penetrate tissue with minimal insertion force and depth, yet high adhesion strength in their swollen state. Uniquely, this design provides universal soft tissue adhesion with minimal damage, less traumatic removal, reduced risk of infection and delivery of bioactive therapeutics.
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    Upper Extremity Composite Tissue Allotransplantation Imaging
    (Open Science Company, LLC, 2013) George, Elizabeth; Mitsouras, Dimitrios; Kumamaru, Kanako K.; Shah, Nehal; Smith, Stacy; Schultz, Kurt; Deaver, Pamela M.; Mullen, Katherine M.; Steigner, Michael L.; Gravereaux, Edwin C.; Demehri, Shadpour; Bueno, Ericka M.; Talbot, Simon; Pomahac, Bohdan; Rybicki, Frank J.
    Objective: Upper extremity (UE) transplantation is the most commonly performed composite tissue allotransplantation worldwide. However, there is a lack of imaging standards for pre- and posttransplant evaluation. This study highlights the protocols and findings of UE allotransplantation toward standardization and implementation for clinical trials. Methods: Multimodality imaging protocols for a unilateral hand transplant candidate and a bilateral mid-forearm level UE transplant recipient include radiography, computed tomography (CT), magnetic resonance (MR) imaging, catheter angiography, and vascular ultrasonography. Pre- and posttransplant findings, including dynamic CT and MR performed for assessment of motor activity of transplanted hands, are assessed, and image quality of vessels and bones on CT and MR evaluated. Results: Preoperative imaging demonstrates extensive skeletal deformity and variation in vascular anatomy and vessel patency. Posttransplant images confirm bony union in anatomical alignment and patency of vascular anastomoses. Mild differences in rate of vascular enhancement and extent of vascular networks are noted between the 2 transplanted limbs. Dynamic CT and MR demonstrate a 15° to 30° range of motion at metacarpophalangeal joints and 90° to 110° at proximal interphalangeal joints of both transplanted hands at 8 months posttransplant. Image quality was slightly better for CT than for MR in the first subject, while MR was slightly better in the second subject. Conclusion: Advanced vascular and musculoskeletal imaging play an important role in surgical planning and can provide novel posttransplantation data to monitor the success of the procedure. Implementation of more standardized protocols should enable a more comprehensive assessment to evaluate the efficacy in clinical trials.
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    Face Time: Educating Face Transplant Candidates
    (Open Science Company, LLC, 2013) Lamparello, Brooke M.; Bueno, Ericka M.; Diaz-Siso, Jesus Rodrigo; Sisk, Geoffroy Courcelle; Pomahac, Bohdan
    Objective: Face transplantation is the innovative application of microsurgery and immunology to restore appearance and function to those with severe facial disfigurements. Our group aims to establish a multidisciplinary education program that can facilitate informed consent and build a strong knowledge base in patients to enhance adherence to medication regimes, recovery, and quality of life. Methods: We analyzed handbooks from our institution's solid organ transplant programs to identify topics applicable to face transplant patients. The team identified unique features of face transplantation that warrant comprehensive patient education. Results: We created a 181-page handbook to provide subjects interested in pursuing transplantation with a written source of information on the process and team members and to address concerns they may have. While the handbook covers a wide range of topics, it is easy to understand and visually appealing. Conclusions: Face transplantation has many unique aspects that must be relayed to the patients pursuing this novel therapy. Since candidates lack third-party support groups and programs, the transplant team must provide an extensive educational component to enhance this complex process. Practice Implications: As face transplantation continues to develop, programs must create sound education programs that address patients’ needs and concerns to facilitate optimal care.
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    High-dose-rate Interstitial Brachytherapy Boost with a Pedicled Latissimus Dorsi Myocutaneous Flap for Myxofibrosarcoma of the Arm
    (Wolters Kluwer Health, 2014) Lane, Jordan D.; Pomahac, Bohdan; Raut, Chandrajit; Baldini, Elizabeth; Devlin, Phillip
    Summary: A 71-year-old man was found to have a 7.4 × 2.9 × 7.0 cm myxofibrosarcoma of the right medial arm close to neurovascular structures. He received 50 Gray (Gy) of preoperative external beam radiation. Radical resection resulted in a 15 × 10 cm defect. Nine brachytherapy catheters were placed, and a pedicled latissimus dorsi myocutaneous flap was used in reconstruction. Final pathology confirmed myxofibrosarcoma, high grade. The tumor was <1 mm from 2 margins. A total of 17.5 Gy of brachytherapy was delivered to the surgical bed from postoperative days 7 to 9. The flap developed fat necrosis distally which eventually required surgical debridement on postoperative day 58. It subsequently healed well and maintained good function of the limb. The patient remains under surveillance without evidence of recurrence.
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    Three Patients with Full Facial Transplantation
    (New England Journal of Medicine (NEJM/MMS), 2012) Pomahac, Bohdan; Pribaz, Julian; Eriksson, Elof; Bueno, Ericka M.; Diaz-Siso, J. Rodrigo; Rybicki, Frank John; Annino, Donald James; Orgill, Dennis; Caterson, Edward; Caterson, Stephanie; Carty, Matthew; Chun, Yoon; Sampson, Christian; Janis, Jeffrey E.; Alam, Daniel S.; Saavedra, Arturo; Molnar, Joseph A.; Edrich, Thomas; Marty, Francisco; Tullius, Stefan
    Unlike conventional reconstruction, facial transplantation seeks to correct severe deformities in a single operation. We report on three patients who received full-face transplants at our institution in 2011 in operations that aimed for functional restoration by coaptation of all main available motor and sensory nerves. We enumerate the technical challenges and postoperative complications and their management, including single episodes of acute rejection in two patients. At 6 months of follow-up, all facial allografts were surviving, facial appearance and function were improved, and glucocorticoids were successfully withdrawn in all patients.
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    Craniofacial Measurements of Donors and Recipients Correlate with Aesthetic Outcome in Virtual Face Transplantation
    (Wolters Kluwer Health, 2015) S. Wallins, Joseph; Chandawarkar, Akash A.; Dobry, Allison S.; Diaz-Siso, J. Rodrigo; Bueno, Ericka M.; Caterson, Edward; Jania, Camille; Hevelone, Nathanael D.; Lipsitz, Stuart; Mukundan, Srinivasan; Pomahac, Bohdan
    Background: Face transplantation is an increasingly feasible option for patients with severe disfigurement. Donors and recipients are currently matched based on immune compatibility, skin characteristics, age, and gender. Aesthetic outcomes of the match are not always optimal and not possible to study in actual cases due to ethical and logistical challenges. We have used a reproducible and inexpensive three-dimensional virtual face transplantation (VFT) model to study this issue. Methods: Sixty-one VFTs were performed using reconstructed high-resolution computed tomography angiographs of male and female subjects aged 20–69 years. Twenty independent reviewers evaluated the level of disfigurement of the posttransplant models. Absolute differences in 9 soft-tissue measurements and 16 bony cephalometric measurements from each of the VFT donor and recipient pretransplant model pairs were correlated to the reviewers’ evaluation of disfigurement after VFT through a multivariate logistic regression model. Results: Five soft-tissue measurements and 3 bony measurements were predictive of the rating of disfigurement after VFT (odds ratio; 95% confidence interval): trichion-to-nasion facial height (1.106; 1.066–1.148), endocanthal width (1.096; 1.051–1.142), exocanthal width (1.067; 1.036–1.099), mouth/chelion width (1.064; 1.019–1.110), subnasale-to-menton facial height (1.029; 1.003–1.056), inner orbit width (1.039; 1.009–1.069), palatal plane/occlusal plane angle (1.148; 1.047–1.258), and sella-nasion/mandibular plane angle (1.079; 1.013–1.150). Conclusions: This study provides early evidence for the importance of soft-tissue and bony measurements in planning of facial transplantation. With future improvements to immunosuppressive regimens and increased donor availability, these measurements may be used as an additional criterion to optimize posttransplant outcomes.
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    Efficacy and Safety of the Collagenase of the Bacterium Clostridium Histolyticum for the Treatment of Capsular Contracture after Silicone Implants: Ex-Vivo Study on Human Tissue
    (Public Library of Science, 2016) Fischer, Sebastian; Hirche, Christoph; Diehm, Yannick; Nuutila, Kristo; Kiefer, Jurij; Gazyakan, Emre; Bueno, Ericka M.; Kremer, Thomas; Kneser, Ulrich; Pomahac, Bohdan
    Background: The fibrotic capsule that surrounds silicone implants consists mainly of collagen. The FDA-approved collagenase of the bacterium clostridium histolyticum provides a reasonable treatment option. Safety and efficacy at the female breast site must be evaluated before clinical utilization. Materials and Methods We incubated 20 samples of fibrotic capsule as well as 12 full thickness skin grafts harvested from the female breast site for 24 hours with different doses of collagenase. Outcome measures involved histological assessment of thickness and density of the capsule tissue as well as the skin grafts. Furthermore, we performed a collagen assay and immunohistochemistry staining for collagen subtypes. Results: Collagenase treatment was able to degrade human capsule contracture tissue ex-vivo. The remaining collagen subtype after degradation was type 4 only. 0.3 mg/ml of collagenase was most effective in reducing capsule thickness when compared with higher concentrations. Of note, effectiveness was inversely related to capsule density, such that there was less reduction in thickness with higher capsule densities and vice versa. Furthermore, the application of 0.3mg/ml collagenase did not lead to thinning or perforation of full thickness skin grafts. Conclusion: Adjustment of collagenase dose will depend on thickness and density of the contracted capsule. A concentration of 0.3mg/ml seems to be safe and effective in an ex-vivo setting. The remaining collagen subtype 4 is suitable to serve as a neo-capsule/acellular tissue matrix. Collagenase treatment for capsular contracture may soon become a clinical reality.
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    Silicone Implants with Smooth Surfaces Induce Thinner but Denser Fibrotic Capsules Compared to Those with Textured Surfaces in a Rodent Model
    (Public Library of Science, 2015) Fischer, Sebastian; Hirche, Christoph; Reichenberger, Matthias A.; Kiefer, Jurij; Diehm, Yannick; Mukundan, Srinivasan; Alhefzi, Muayyad; Bueno, Ericka M.; Kneser, Ulrich; Pomahac, Bohdan
    Purpose Capsular contracture is the most frequent long-term complication after implant-based breast reconstruction or augmentation. The aim of this study was to evaluate the impact of implant surface properties on fibrotic capsule formation in an animal model. Materials and Methods Twenty-four rats received 1 scaled down silicone implant each; 12 of the rats received implants with textured surfaces, and the other 12 received implants with smooth surfaces. After 60 and 120 days, rats in each group underwent 7-Tesla Magnetic Resonance Imaging (MRI) and high-resolution ultrasound (HR-US), and specimens of the capsules were acquired and used to measure capsule thickness through histology, collagen density through picro sirius red staining, and analyses of expression of pro-fibrotic and inflammatory genes (Collagen1-4, TGFb1, TGFb3, Smad3, IL4, IL10, IL13, CD68) through qRT-PCR. Furthermore, MRI data were processed to obtain capsule volume and implant surface area. Results: On day 60, histology and HR-US showed that fibrotic capsules were significantly thicker in the textured implant group with respect to the smooth implant group (p<0.05). However, this difference did not persist on day 120 (p=0.56). Capsule thickness decreased significantly over the study period in both smooth and textured implant groups (p<0.05). Thickness measurements were substantiated by MRI analysis and volumes changed accordingly. Implant surface area did not vary between study dates, but it was different between implant types. On day 60, the density of collagen in the fibrotic capsules was significantly lower in the textured implant group with respect to the smooth group (p<0.05), but again this difference did not persist on day 120 (p=0.67). Collagen 1 and CD68 were respectively over- and under expressed in the textured implant group on day 60. Significant differences in the expression of other genes were not observed. Conclusion: Silicone implants with textured surfaces led to temporarily thicker but less dense fibrotic capsules compared with smooth surfaces. 7-Tesla MRI and HR-US are capable for non-invasive in-vivo assessment of capsular fibrosis in an animal model and can provide unique insights into the fibrotic process by 3D reconstruction and surface area measurement.
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    Reduced Radiation Exposure for Face Transplant Surgical Planning Computed Tomography Angiography
    (Public Library of Science, 2013) Schultz, Kurt; George, Elizabeth; Mullen, Katherine; Steigner, Michael; Mitsouras, Dimitrios; Bueno, Ericka M.; Pomahac, Bohdan; Rybicki, Frank John; Kumamaru, Kanako
    Objective: To test the hypothesis that wide area detector face transplant surgical planning CT angiograms with simulated lower radiation dose and iterative reconstruction (AIDR3D) are comparable in image quality to those with standard tube current and filtered back projection (FBP) reconstruction. Materials and Methods The sinograms from 320-detector row CT angiography of four clinical candidates for face transplantation were processed utilizing standard FBP, FBP with simulated 75, 62, and 50% tube current, and AIDR3D with corresponding dose reduction. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured at muscle, fat, artery, and vein. Image quality for each reconstruction strategy was assessed by two independent readers using a 4-point scale. Results: Compared to FBP, the median SNR and CNR for AIDR3D images were higher at all sites for all 4 different tube currents. The AIDR3D with simulated 50% tube current achieved comparable SNR and CNR to FBP with standard dose (median muscle SNR: 5.77 vs. 6.23; fat SNR: 6.40 vs. 5.75; artery SNR: 43.8 vs. 45.0; vein SNR: 54.9 vs. 55.7; artery CNR: 38.1 vs. 38.6; vein CNR: 49.0 vs. 48.7; all p-values >0.19). The interobserver agreement in the image quality score was good (weighted κ = 0.7). The overall score and the scores for smaller arteries were significantly lower when FBP with 50% dose reduction was used. The AIDR3D reconstruction images with 4 different simulated doses achieved a mean score ranging from 3.68 to 3.82 that were comparable to the scores from images reconstructed using FBP with original dose (3.68–3.77). Conclusions: Simulated radiation dose reduction applied to clinical CT angiography for face transplant planning suggests that AIDR3D allows for a 50% reduction in radiation dose, as compared to FBP, while preserving image quality.