Abstract Photons are described by particle and wave theories. It is accepted photons do not possess mass, charge nor are deflected by a magnetic field. A 2005 review concluded photon mass was mathematically feasible, but lacked experimental evidence [1]. During electron-spin-resonance experiments, hair containing melanin was 694 nm laser-irradiated. An ‘off-resonance’ at laser-firing was observed in a time-scan at constant magnetic field, whilst monitoring laser-induced radical formation [2]. It was hypothesised coherent photons interacted with the field, suggesting charge, magnetism and mass. The radical g-value was invariant in successive field-scans, although the hair melted. Melanin in the solid state in hair, does not exhibit temperature-dependent paramagnetism [3]. 2.2 – 3.6 x 1019 photons in 6 – 10 J were calculated to be absorbed, and a mean 72% ‘off resonance’ signal-drop determined from the time-scan, translates to a field-shift of 4 G or 4 x 10-4 T. If the pulse is a point charge (Nphoton .qphoton) with Nphoton the photon number and qphoton the charge per photon, then from the Biot-Savart equation qphoton can be calculated from 0.0004.(Nphoton x 29.98/r2)-1, where r is 1 m, and is 3.6 – 6.1 x 10-25 coulombs. The calculated collision photon : electron charge (q/e) approaches 3 x 10-6. If qphoton is extrapolated for photons moving in air/space by a ‘dilution factor’ of 106 then q/e would be 10-13 and comparable to laboratory-based measurements of 10-14-10-17. The observation and calculations suggest photons are charged; discrepancies in the measured values reflect differences in photon speed at the point of measurement.[1] Liang-Cheng Tu, Jun Luo and George T Gillies. The Mass of the Photon. Rep. Prog Phys 2005: 68; 77-130.[2] Rachel M. Haywood and Claire Linge. Differences in Production of Melanin Radicals by 694 nm Ruby Laser and UVA Radiation. Lasers Surg Medicine 2004: 35; 77-83.[3] Shiu-Shin Chio, James S. Hyde and Roger C. Sealy. Temperature-Dependent Paramagnetism in Melanin Polymers. Arch Biochem Biophys 1980: 199; 133-139.

Although emergence of bone tissue engineering techniques has revolutionized the field of maxillofacial reconstruction, the successful translation of such products, especially concerning larger sized defects, still remains a significant challenge. Light-curable methacrylate-based polymers have ideal properties for bone repair. These materials are also suitable for 3D printing which can be applicable for restoration of both function and aesthetics. The main objective of this research was to synthesize a mechanically stable and biologically functional polymer for reconstruction of complex craniofacial defects. The experimental work initially involved synthesis of (((3R,3aR,6S,6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl)bis(oxy))bis(ethane-2,1-diyl)bis((4-methyl-3-oxopent-4-en-1-yl)carbamate), CSMA-1, and ((((((((((((3R,3aR,6S,6aR)-hexahydrofuro[3,2-b]furan-3,6-diyl)bis(oxy))bis(ethane-2,1 diyl))bis(oxy))bis(carbonyl))bis(azanediyl))bis(methylene))bis(3,3,5-trimethylcyclohexane-5,1-diyl))bis(azanediyl))bis(carbonyl))bis(oxy))bis(ethane-2,1-diyl)bis(2-methylacrylate), CSMA-2; nuclear magnetic resonance analysis confirmed formation of the monomers, and composite samples were fabricated respectively by exposing 11 mm diameter discs to blue light. Modulus of elasticity was determined using a biaxial flexural test and the values were found to be between 1 and 3 GPa in CSMA-1, CSMA-2, and their composites. In vitro cell culture, using human bone marrow-derived mesenchymal stem cells, confirmed nontoxicity of the samples and finally 3D printing allowed direct photo-polymerization and setting of the bio ink into a 3D construct.

The superficial femoral artery and medial thigh region has been an underused donor site for perforator flaps. This study evaluated perforasomes of the superficial femoral artery and its principal branches to review the clinical applications for locoregional reconstruction. Twenty-six fresh cadaveric lower extremities were dissected. Perforator size and anatomical course from the superficial femoral artery, descending genicular artery, and saphenous artery branch were documented. Perforators were selectively injected with iodinated contrast to assess vascular territories using computed tomography. A retrospective chart review was conducted on consecutive patients (2014 to 2015). One hundred thirty perforators were mapped in the medial thigh region. Eleven extended medial thigh perforator flaps and 15 hemicircumferential flaps were harvested. The mean distance from the joint line was 16.7 ± 7.3 cm. Perforators arose from the superficial femoral artery (62 percent), saphenous artery branch (23 percent), and descending genicular artery (15 percent). Superficial femoral artery perforators were located around the mid and proximal thigh region (p < 0.001). The median perforasome surface area was 244 cm, representing 36 percent in hemithigh flaps with preferential filling in the anteromedial region. Proximal perforasomes were the smallest. Perforasome areas based on vessel origin were comparable; however, saphenous artery perforators had a broader perforasome compared with descending genicular (p = 0.01) and superficial femoral artery perforators (p = 0.04). Six clinical case examples were presented for knee, thigh, and lower leg reconstruction. The superficial femoral artery or its branches can provide nontraditional reconstructive perforator flap options in regional reconstruction. They can be simple to harvest using a free-style approach, do not require preoperative imaging, offer a one-stage reconstructive method with low morbidity, and obviate the need for microsurgery or muscle flaps.

This study aimed to delineate and compare the hot spots and three-dimensional vascular territories of dominant profunda artery perforators in the posterior thigh region, and modifications in flap design are discussed. Twenty-nine posterior thigh flaps were raised in fresh cadaveric specimens, and profunda artery perforators were documented. Dominant perforators were injected with iodinated contrast to assess perforasomes using computed tomographic angiography. Analysis with three-dimensional rendering and volume calculations of perfusion patterns was performed. In total, 316 perforators were mapped and 33 perforators were injected for analysis. The hot spot for dominant perforators was the proximal medial quadrant, 5 to 10 cm from the inferior gluteal crease, with two smaller hot spots in the upper lateral and distal posterior midline. Although 69 percent were musculocutaneous, distal perforators were predominantly septocutaneous in the posterior midline, 5 to 8 cm from the popliteal crease. Proximal perforators were classified into first (most proximal) and second perforators, and their median perforasome was 233 and 286.4 cm, respectively (p = 0.86). There were no significant differences between proximal and distal perforators in perforasome surface areas, percentage areas perfused, and perforasome volumes. Large linking vessel networks were attributed to a broader perforasome and greater overlap between adjacent or distal perforators. Dominant linking vessels and recurrent flow through the subdermal plexus contribute to the robust vascular supply of profunda artery perforator flaps. Posterior thigh region perforator hot spots and their perfusion characteristics can inform the potential limits, orientation, and modifications of flap or skin paddle designs.

This reconstructive microsurgery course will run yearly and was borne and popularized from its infant meeting the year before, primarily focused on perforator flaps. It is a 2-day course updating residents/registrars to attending physicians/consultants about the most topical advancements in microvascular reconstructive surgery. The course is held at the New York University Langone Hospital in the United States.The timetable is primarily lecture based with the advantage of live-surgical procedures by world-renowned faculty. The timetable includes, but not limited to, facial/hand vascularized composite allotransplantation, upper/lower limb, breast, head and neck, transgender, and lymphedema surgery. Lectures were highly informative and there was ample time for case discussion with the appreciation that managing complex situations often requires input from other colleagues. The faculty focused on the lessons they have learned and potential pitfalls to avoid. The faculty was comprised of leading experts in reconstructive microsurgery from Europe, Korea, and throughout the United States.The primary emphasis of the course was to appreciate the global recognition in advances in microsurgery.

Perforator selection is critical to deep inferior epigastric perforator (DIEP) flap harvest. Commitment to a single perforator has the potential benefit of a simpler dissection, but may increase fat necrosis or perfusion-related complications compared with multiple perforator harvest. A 3-year retrospective study was carried out of all patients who underwent DIEP flap breast reconstruction performed by the senior author (M.S.-C). Data were collected on patient demographics and surgical outcomes. One hundred eighty-three flaps were performed (105 patients) over 3 years. One hundred fifty-six bilateral (78 patients) and 24 unilateral flaps were included in the final study. Mean age was 47.8 ± 8.4 years and mean body mass index was 29.1 ± 5.3 kg/m. Seventy-five percent of flaps were based on single dominant perforators. Single perforators were used in 33.3 percent of flaps weighing over 1000 g, 80 and 74 percent of flaps weighing 500 to 1000 g and less than 500 g, respectively (p = 0.01). There were no differences in overall complications between single- versus multiple-perforator DIEP flaps. Neither body mass index nor flap weight posed additional risk to overall complications. Conversion to a muscle-sparing flap was 9.4 percent. The authors present an algorithm for perforator selection, stepwise approach to flap harvest, and considerations for intraoperative decision-making in DIEP flap reconstruction. Single-dominant perforator flaps can be safely performed, but inclusion of the largest perforator is critical to flap perfusion. Additional perforators must be weighed against the associated tradeoff with donor-site morbidity. The threshold for conversion to a muscle-sparing flap is reduced with increased clinical experience. Therapeutic, III.

After studying this article, the participant should be able to: 1. Understand the history and physiology of perforator flaps. 2. Understand the concept of "free-style" perforator flaps and principles in design and harvest. 3. Understand the uses of perforator flaps in reconstruction and applications in new settings. 4. Understand new principles in single and multiple perforator flap harvest and adjunct techniques that can be used in perforator flaps. 5. Highlight pertinent anatomy and techniques for selected perforator flaps described. Extended knowledge of vascular anatomy has propagated the development of perforator flaps, which preserve muscle function and reduce morbidity. This has been achieved through the exemplary works of Manchot, Salmon, Milton, Taylor, and many others. With over 350 clinically relevant perforators in the body, this has created new flap options and a sense of creative freedom for reconstruction tailored toward a specific defect, without constraints of specific landmarks and using a "free-style" approach. Dominant perforators may be found in zones of high perforator density or "hot spots," which can help to conceptualize local flap options and aid flap design. This article aims to outline the history, physiology, and principles of flap design and harvest, and highlight traditional and evolving concepts and modifications of contemporary and traditional flaps that are changing reconstructive practice. This is a broad overview focusing on clinical applications, highlighting key concepts in a selection of new or evolving flaps being used in clinical practice and providing source references to acquire detailed flap descriptions.

Keystone flaps have demonstrated growing clinical applications in reconstructive surgery in the past decade. This article highlights flap modifications and their versatility for clinical applications and management of complex defects. A retrospective chart review was conducted of consecutive patients undergoing keystone flap reconstruction at the authors' institution from January of 2012 to December of 2014. Patient demographics, indications, and operative and postoperative details were abstracted. Forty-two keystone flaps were performed in 36 patients. Indications included malignant melanoma (n = 14), soft-tissue sarcoma (n = 12), benign pathologic conditions (e.g., exposed hardware, enterocutaneous fistula, tissue necrosis) (n = 6), and nonmelanoma skin cancer (n = 4). Twenty-eight percent received neoadjuvant irradiation, and 70 percent of these were for sarcoma. Locoregional adjunct flaps were performed in eight patients. The deep fascia was nearly completely in a circumferential manner in 18 of 36 patients (50 percent), in 92 percent of the sarcoma reconstructions, and located mainly in the lower extremity. Average defect size was 215 cm (range, 4 to 1000 cm). Average defect size was 474 cm and 35.8 cm after sarcoma and malignant melanoma resection, respectively. Average flap size was 344 cm (range, 5 to 1350 cm). Ninety percent of cases had flap sizes exceeding the traditional 1:1 ratio. There was no flap loss or partial necrosis. Mean time to mobilization was 1.8 days, and mean hospital length of stay was 6.8 days. Keystone flaps offer an excellent versatile tool for reconstructive surgeons. Fundamental principles behind the vascular basis of the keystone flap and its modifications permit their greater utility in complex wounds in the settings of large oncologic resections, irradiation, and trauma. Therapeutic, IV.

The area perfused by a single perforator depends on its perforasome and its unique interperforator flow pattern. The purpose of this study was to clarify the interperforator flow patterns of the peroneal and posterior tibial artery perforators using three-dimensional computed tomographic angiography. Thirteen whole-leg skin flaps were harvested in the subfascial plane from fresh cadavers. Peroneal, posterior tibial, anterior tibial, and sural artery perforators with a diameter greater than 0.5 mm were documented. Three-dimensional computed tomographic angiography with an injection of iodinated contrast medium into the peroneal or posterior tibial artery perforator was used to investigate the percentages of the area and the perforators that were perfused. The mean percentage of the total area perfused was as follows: peroneal artery perforator, 42.0 percent; posterior tibial artery perforator, 38.0 percent (p = 0.084). The mean percentage of the total perforators perfused was as follows: peroneal artery perforator, 55.0 percent; posterior tibial artery perforator, 44.2 percent (p = 0.004). Although the mean percentages of same-source artery perforators perfused by a peroneal artery perforator (73.6 percent) and by a posterior tibial artery perforator (77.2 percent) did not differ (p = 0.513), the mean percentages of other-source artery perforators perfused by a peroneal artery perforator (49.9 percent) and by a posterior tibial artery perforator (32.3 percent) were significantly different (p < 0.001). This study demonstrated that a single peroneal or posterior tibial artery perforator perfused approximately 40 percent of the whole leg surface and that peroneal and posterior tibial artery perforators had different interperforator flow patterns. The results of this study may improve preoperative planning for pedicled perforator flap surgery. Therapeutic, V.

Tissue expander-based two-stage reconstruction remains the most commonly used technique in immediate breast reconstruction. This study compares the subcutaneous expander placement to the traditional submuscular placement and describes our early experience with the expander insertion plane-choosing algorithm. A retrospective study of patients who underwent two-stage immediate breast reconstruction from May 2012 to October 2014 was conducted. All expander insertion planes were chosen using the same algorithm. Expansion, pain, and complications were compared between two groups. The study included 88 patients (158 expanders; 50 subcutaneous and 108 submuscular). The subcutaneous group had a higher intraoperative expansion ratio (p<0.001), high first postoperative expansion ratio (p<0.001), shorter duration of expansion (p=0.02), less number of expansion visits (p=0.002), and less average pain during admission (p=0.004). Significant differences in the intraoperative and first postoperative expansion ratios in patients with postmastectomy radiation therapy were also found between the two groups (p=0.005 and 0.01, respectively). Complications during expansion and after second-stage autologous flap reconstruction were comparable between two groups. The subcutaneous expander placement was associated with greater intraoperative and first postoperative expansion, shorter expansion duration, less expansion visits, and less pain. With the expander insertion plane-choosing algorithm, subcutaneous expander placement could be performed with comparable complications rates with the submuscular placement during expansion and after second-stage autologous flap reconstruction. Further studies can be performed due to the lack of long-term complications following second-stage implant reconstruction in the subcutaneous approach.