Incision Patterns Research Articles

Review of morphotectonic studies in the East African Rift System: Insights from legacy research to modern advances

The East African Rift System (EARS) is a prime example of continental rifting, characterized by its iconic topographic features, which are significantly shaped by the interplay of tectonic and climatic forces. This review synthesizes past decades of morphotectonic studies (recent studies) on the plateau landscapes of the EARS, focusing particularly on their interiors and margins, and highlights their crucial role in advancing our understanding of landscape evolution. The paper revisits the legacy of geologic research in the EARS and delves into recent morphotectonic studies that quantify the rates and patterns of plateau incision, exhumation, and uplift through advanced thermochronological and topographic analyses. Additionally, the review identifies key unresolved questions, such as the origins of the plateau topography–whether from volcanic activity or mantle plume influence and explores how these plateaus maintained high elevations during the humid Oligocene Epoch without significant incision. The recent work described in this paper alongside legacy perspectives, continues to refine our geological understanding of the EARS, with broader implications for studies worldwide.

Incision and rock uplift along the Lower Seine River since Marine Isotope Stage 8

ABSTRACTThe study of alluvial terraces helps in reconstructing the past geometries of rivers and makes it possible to assess the rate and pattern of fluvial incision and bedrock uplift. The fluctuations of river base levels are particularly variable and complex during the Late Quaternary in the lower course of rivers due to the interplay of responses to sea‐level fluctuations, tectonics and glacio‐isostasy. In this paper, the geometry and chronology of Manoir Brésil, an outcrop of alluvial terraces of the Lower Seine River, northern France, are investigated through a multidisciplinary study. Fluvial incision during MIS 8 in the Lower Seine in relation to sea‐level drop is recorded by an erosional surface cut into the chalk bedrock. This surface is covered by MIS 7 tidal deposits and then by younger, mostly periglacial colluvium (head). Manoir Brésil is therefore considered to be a chronological equivalent of the nearby, well‐studied Tourville‐la‐Rivière outcrop. The deposits are affected by post‐MIS 7 cryoturbation processes. Based on the local elevation of MIS 7 tidal deposits and erosional surfaces at Manoir Brésil, a minimum bedrock uplift rate of 25–40 m/Ma and an erosion rate of 125 m/Ma during glacial periods can be proposed. A regional correlation of the MIS 8 erosional surface is increasingly deformed by uplift towards the North, making it difficult to correlate the fluvial deposits along the Seine without precise chronological control. We interpret this regional tilt as the result of isostasy rebound after glaciations, consistent with the distribution of the elevations of MIS 5e and MIS 7 marine deposits along the English Channel.

A salty snapshot: extreme variations in basal erosion patterns preserved in a submarine channel

The bases of active submarine channels are marked by large erosional features, such as knickpoints and plunge pools. However, their presence in ancient channel-fills has rarely been documented, so their importance in submarine channel morphodynamics requires investigation. Using seismic reflection data calibrated by wells from a buried submarine channel-fill, we document erosional features hundreds of metres long and tens of metres deep, here interpreted as knickpoints and a plunge pool, and provide a mechanistic process for their transfer into the stratigraphic record. Channel incision patterns are interpreted to record a transient uplift in an otherwise subsiding depocentre. Local structural complexities in the channel slope formed zones of preferential scouring. A switch to a depositional regime preserved the irregular channel base, inhibiting both the upstream migration of scours and smoothing of the channel base. The formation and preservation of these scours record the responses to salt tectonics and provide a unique snapshot of the formative processes of an ancient submarine channel. The presence of these exceptional basal scours indicates that headward erosion processes did not operate rapidly, challenging the paradigm that knickpoint migration controls channel evolution. Our results show that the primary erosion of the main channel surface and long-term channel evolution are both dominated by far more gradual processes.

Analysis of cytosine deamination events in excision repair sequencing reads reveals mechanisms of incision site selection in NER.

Nucleotide excision repair (NER) removes helix-distorting DNA lesions and is therefore critical for genome stability. During NER, DNA is unwound on either side of the lesion and excised, but the rules governing incision site selection, particularly in eukaryotic cells, are unclear. Excision repair-sequencing (XR-seq) sequences excised NER fragments, but analysis has been limited because the lesion location is unknown. Here, we exploit accelerated cytosine deamination rates in UV-induced CPD (cyclobutane pyrimidine dimer) lesions to precisely map their locations at C to T mismatches in XR-seq reads, revealing general and species-specific patterns of incision site selection during NER. Our data indicate that the 5' incision site occurs preferentially in HYV (i.e. not G; C/T;not T) sequence motifs, a pattern that can be explained by sequence preferences of the XPF-ERCC1 endonuclease. In contrast, the 3' incision site does not show strong sequence preferences, once truncated reads arising from mispriming events are excluded. Instead, the 3' incision is partially determined by the 5' incision site distance, indicating that the two incision events are coupled. Finally, our data reveal unique and coupled NER incision patterns at nucleosome boundaries. These findings reveal key principles governing NER incision site selection in eukaryotic cells.

Kirigami-based inverse design for 3D surfaces formed by mechanically guided method

The mechanically guided assembly method utilizes the compressive buckling behavior of thin-film structures to transform two-dimensional (2D) precursors into three-dimensional (3D) structures. Previous research has shown that by inverse designing thickness and width distributions in 2D precursors, various 3D surfaces with target geometries can be accurately assembled. However, the variation in thickness poses significant challenges for the fabrication of the 2D precursor, especially on a small scale. In this paper, we propose a Kirigami-based inverse design framework that utilizes pre-specified incision patterns as critical parameters to control the bending stiffness distribution of 2D precursors. This enables the fabrication of target 3D structures with constant thickness, which greatly simplifies the production of 2D precursors. By studying the deformation characteristics of beam models during pure bending, we have established an analytical relationship between incision patterns and bending stiffness distribution. To validate the effectiveness of our inverse design theory, we conducted a series of simulations and experiments on 3D structures, yielding favorable comparison results. Moreover, guided by this inverse design theory, we have developed a microneedle structure through conceptual design, demonstrating the capability of Kirigami patterns in the inverse design of complex 3D structures, and highlighting the potential application of our method in the biomedical field.

A prospective randomized comparison of functional and cosmetic outcomes of a coronal zigzag incision versus a conventional straight incision pattern for craniotomy.

Wound healing problems after neurosurgical procedures can lead to serious complications and may require complex revision or even reconstructive surgery. Therefore, optimal surgical management is critical to prevent complications. In a recent experimental study in animals, the authors demonstrated the superiority of a zigzag skin incision over a straight incision pattern. In this study, the authors applied these findings to clinical situations of neurosurgical patients with an indication for a coronal skin incision. The aim of this study was to objectively assess the functional and cosmetic outcomes between straight coronal and zigzag incisions in neurosurgical procedures. This prospective, randomized, controlled, single-center trial included adult patients undergoing frontal craniotomy for cerebrovascular or tumor pathologies. The study primarily included patients who were not expected to receive adjuvant radiation or chemotherapy. The zigzag incision was standardized using a template. A common straight skin incision behind the hairline served as a control. Complication rates, functional (2-point discrimination, width of the wound, Vancouver Scar Scale [VSS], and Patient and Observer Scar Assessment Scale [POSAS]), and cosmetic outcomes were assessed postoperatively and at 3-month follow-up evaluations. Additionally, all patients answered a wound-specific questionnaire and the SF-36 questionnaire. Twenty-eight patients were randomized to the zigzag and 29 to the straight incision groups. Indications for surgery were cerebrovascular in 16 cases and tumors in 41 cases. Risk factors for wound healing were equally distributed in both groups. One patient in the zigzag group with poor postoperative compliance required surgery for secondary wound healing problems. Overall, the width of the scar was significantly smaller (p = 0.001) and local 2-point discrimination better (p = 0.005) in the zigzag group. Scores on the VSS (p = 0.003) and POSAS (p = 0.005) proved to be significantly superior in the zigzag group as well. A zigzag coronal skin incision pattern leads to significantly superior functional and cosmetic outcome scores. For certain patient groups, these findings may prove to be practice-changing.

Head-to-Head Analysis of Vertical vs Horizontal Incision Patterns in Breast Reconstruction: Surgical Outcomes and Aesthetic Implications.

Modern aesthetically optimized breast reconstruction requires collaboration between the patient, breast surgeon, and plastic surgeon. To optimize both surgical outcome and aesthetic results, incision patterns must be carefully planned. We aimed to determine whether vertical or horizontal orientation of mastectomy incision was preferred in the general population and to analyze corresponding complication profiles. A retrospective review was performed of all patients undergoing bilateral mastectomy followed by autologous breast reconstruction utilizing either vertical or horizontal incision from January 2011 to November 2022. Postoperative complications of the 2 incision patterns were analyzed. Additionally, crowdsourcing was utilized to assess aesthetic implications of horizontal and vertical incision patterns on postoperative pictures of completed breast reconstruction. Survey rater demographics were also analyzed to assess differences in scoring based on voter characteristics. There were no significant differences in postoperative breast complications between patients with horizontal or vertical incisions when considering wound, infection, seroma, hematoma, fat necrosis, or overall complications (P > .05). Crowdsourcing showed that, regardless of voter demographics, vertical incisions were preferred over horizontal incisions (P < .001). Additionally, voters who knew someone who had undergone breast reconstruction were more likely to rate all incision patterns higher than other voters (P < .001). Although there are no significant differences in complication profiles between vertical and horizontal incisions in autologous breast reconstruction patients, vertical incision patterns are preferred aesthetically by the general population.

Modeling of metamaterial based incision patterns for generating high expansions in skin grafts

BackgroundSplit-thickness skin grafting is a widely used treatment for burn patients. It requires removing a small portion of healthy skin, making parallel incisions on it, stretching it, and surgically implanting it into the burn site. Although skin graft mesher companies claim to significantly expand the size of the skin graft, in reality, the amount of expansion achieved is much smaller. MethodsThis study aimed to improve the expansion potential of skin grafts by designing new incision patterns with auxetic properties, using a skin simulant material and additive manufacturing. The mechanical properties and digital image correlation was used to analyze the strain, effective Poisson's ratio, local strains, void area, and meshing ratio of the auxetic skin graft simulants. FindingsThe results showed that the Y-shaped skin graft simulant had the highest effective negative Poisson's ratio, largest areal expansions, lowest maximum induced stresses and strains, and uniform strain distribution properties, making it the best choice for generating high expansions in skin grafts. IntrepretationThe study found that the expansions were highly strain sensitive, with higher auxeticity observed at lower strains. The novel findings with auxetic skin graft simulants are expected to provide valuable insights for developing skin grafts with higher expansion potential in the future.

Tension Reduction With Force Modulating Tissue Bridges Reduces Wounds in Breast Surgery.

Tension on healing wounds increases the risk of dehiscence and poor or pathologic scar formation. Force modulating tissue bridges (FMTBs) represent a new class of wound closure and support devices designed to offload tension on healing wounds to improve wound healing and scar outcomes. The study was undertaken to assess the efficacy of FMTBs to reduce the risk of wound healing complications in elective breast surgery. One hundred twenty-two consecutive patients undergoing bilateral aesthetic breast surgery underwent intraoperative placement of FMTBs on the vertical limb closure site. A matched case-control cohort of 121 consecutive patients was established for comparison. Wounds were considered significant if larger than 3 mm in diameter. The primary outcome of breast wounds >3 mm was reported with a relative risk, and all outcomes were framed with number needed to treat. The control and intervention cohorts had similar demographics, comorbidities, type of operation, and incision pattern utilized. Within the FMTB group, 96.7% (n = 118) patients completed treatment per protocol. Significant wounds occurred in 1.7% (n = 2) of patients in the tissue bridge vs 15.2% (n = 19) in controls on a per patient/per protocol basis (89% reduction, P < .001). Statistically significant improvements were maintained on sensitivity analyses with intention to treat, even when minor wounds were included. There were no complications noted related to FMTBs. FMTBs are safe and highly effective at reducing the risk of wound formation in elective breast surgery. Results are consistent with sensitivity analyses based on clinical and methodological factors. Further research will assess long-term scar outcomes.

Finite Element Analysis of Hierarchical Metamaterial-Based Patterns for Generating High Expansion in Skin Grafting

Burn injuries are very common due to heat, accidents, and fire. Split-thickness skin grafting technique is majorly used to recover the burn sites. In this technique, the complete epidermis and partial dermis layer of the skin are used to make grafts. A small amount of skin is passed into the mesher to create an incision pattern for higher expansion. These grafts are transplanted into the burn sites with the help of sutures for recovering large burn areas. Presently, the maximum expansion possible with skin grafting is very less (&lt;3), which is insufficient for covering larger burn area with a small amount of healthy skin. This study aimed to determine the possibility of employing innovative auxetic skin graft patterns and traditional skin graft patterns with three levels of hierarchy. Six different hierarchical skin graft designs were tested to describe the biomechanical properties. The meshing ratio, Poisson’s ratio, expansion, and induced stresses were quantified for each graft model. The computational results indicated that the expansion potential of the 3rd order auxetic skin graft was highest across all the models. These results are expected to improve burn surgeries and promote skin transplantation research.

Auxetic incisions with alternating slit shapes: a promising technique for enhancing synthetic skin grafts expansion

Split thickness skin grafts are widely used in treating burn injuries. To date, with limited availability of donor skin and minimal expansions offered by conventional skin grafting, it is challenging to cover large and severe burns. In this study, novel synthetic skin grafts with alternating slit (AS) shaped cut patterns were developed and tested to evaluate the expansion potentials offered by auxetic or negative Poisson’s ratio structures in skin grafting. A range of auxetic incision patterns were designed with varying unit cell dimensions, and these were projected onto skin using 3D printing. The mechanical properties and digital image correlation of the created synthetic skin grafts were used to determine stress, effective Poisson’s ratio, meshing ratio (MR), and generated strains for strain loadings of up to 150%. The AS graft simulant with equal slit lengths and low slit spacings exhibited the maximum negative Poisson’s effect, expansion, and Mr Expansions were inversely related with the spacing between slits. The lowest value for the MR and highest stress was observed with high spacing, high horizontal slit length, and low vertical slit length. The expansions were highly sensitive to the applied strain, with low strains exhibiting high auxeticity. Such an extensive experimental investigation of the expansion potentials and stress estimations of skin grafts with varying AS dimensional parameters have not been conducted previously. The findings would be crucial for advancing research on mitigation of large burn injuries using high expansion skin grafts.

Morphological and architectural evolution of submarine channels: An example from the world's largest submarine fan in the Bay of Bengal

The characteristics and evolution of different types of channel-complex sets (CCSs) have long attracted attention from both academia and the oil industry. 3D seismic data from the world's largest submarine fan in the Bay of Bengal allow the exploration of morphology, architecture, and evolution of a Pleistocene submarine channel system from inception to abandonment. Four types of architectural elements are recognized, including feeder and distributary channel-complex set (CCS), levees, bend cutoffs, and incised and unincised crevasse splays. Three types of CCSs are recognized: (1) erosional non-leveed CCSs with the lowest values of channel width (W), thickness (T), and cross-sectional area (Ca) (mean values of W = 153 m, T = 20 m, and Ca = 2613 m2); (2) graded CCSs with the highest values of W, T and Ca (mean values of W = 745 m, T = 89 m, and Ca = 49183 m2); (3) aggradational leveed CCSs with intermediate values of W, T and Ca (mean values of W = 476 m, T = 56 m, and Ca = 21968 m2). Graded CCSs and aggradational leveed CCSs have overbank levees, crevasse splays and bend cutoffs, whereas erosional non-leveed CCSs lack these features. Such architectural difference in overbank deposits suggests a channel evolution pattern of initial incision (erosional non-leveed CCSs) and then aggradation (graded and aggradational leveed CCSs), resulting in a pattern of incision-to-aggradation channel evolution. An increase-then-decrease in channel morphometrics (represented by W, T, and Ca) from erosional non-leveed CCSs with the lowest mean values of W, T, and Ca, to graded CCSs with the highest mean values of W, T, and Ca, and finally to aggradational leveed CCSs with the intermediate mean values of W, T, and Ca suggest that the incision-to-aggradation channel evolution is related to waxing-then-waning energy cyclicity. Submarine channel turbidity flows during the waxing energy phase became progressively more energetic and increasingly more erosional, producing erosional non-leveed CCSs. Instead, submarine channel turbidity flows during the waning energy phase were more diluted and increasingly more depositional, thereby producing aggradational leveed CCSs. The phase of peak environmental energy was most likely accompanied by most energetic turbidity currents, resulting in graded CCSs. Results and observations from the current study contribute to a better understanding of architectural complexity and evolution of submarine channels.

Gutta percha, natural rubber and balata-chemical characterization of polyisoprenes in the context of cultural heritage

Gutta percha, natural rubber, and balata are latexes produced by tropical trees that since the mid-nineteenth century have been extensively used commercially and in the creation of artworks and daily use objects. All three latexes are stereoisomers of polyisoprene that differ in their molecular structure. In gutta percha and balata, the molecular functional group is in the trans- position; in natural rubber, it is in the cis- position. This difference in their molecular structure affects the physical properties of these materials and their aging, turning natural rubber tacky and gutta percha brittle. Commercially focused analysis of natural polyisoprenes has typically used chemically modified materials. The present study characterizes natural, chemically unadulterated latex harvested from trees, aiming to differentiate the cis- and trans-forms. The analysed materials comprised fresh latexes harvested in Malaysia and Indonesia, naturally aged botanical samples, some over 100 years old, and minimally processed 10-year-old commercial stock; a total of 50 samples were examined, out of which 23 are discussed in detail. The harvesting practices of latexes were recorded during fieldwork in Southeast Asia in 2015–2019, in Cipetir (Tjipetir), on Lingga Island in Indonesia, and in Malay rubber plantations. The harvesting methods are the first indicators as to the type of latex harvested based on the pattern of incisions and time of coagulation upon exposure to air. The interviews of tappers, especially of gutta percha and balata, serve as a record of a disappearing craft. Therefore, this fieldwork report contributing to a general knowledge of working methods with natural latexes is of particular value considering the scarcity of published records. The laboratory analytical study of trans- and cis- forms relied on nuclear magnetic resonance (NMR) spectroscopy, which is the most accurate method to unambiguously determine the stereo chemistry of each polyisoprene. The characteristic spectroscopic features of cis- and trans-positions were clearly shown in all samples, in fresh latex, in over 100-year-old material, and in early twentieth century artifacts. This result indicated that the aging of the polyisoprenes does not prevent the identification of their stereochemistry. This analytical work is the first thorough examination of gutta percha, natural rubber and balata in the context of cultural heritage to guide preservation strategies for objects made of these materials.

Patterns of valley incision beneath the Greenland Ice Sheet revealed using automated mapping and classification

The Greenland Ice Sheet covers an area of 1.7 million km2, equivalent to ∼79 % of the surface of Kalaallit Nunaat (Greenland) and ∼1.2 % of the Earth's land surface. The macro-scale geomorphology beneath the ice can provide a valuable record of past ice sheet behaviour, particularly during warm periods that may serve as analogues for present and future climates. However, despite extensive mapping of the landscape by airborne radar surveying, Greenland's subglacial geomorphology remains comparatively understudied. Here we construct an automated workflow to identify, extract, and quantify the morphology of valley cross-sectional profiles across Greenland, as observed in NASA Operation IceBridge radar data. We identify 5335 cross-sectional profiles and apply a supervised machine learning method to classify valleys based on their morphological similarity to those formed by glacial or fluvial incision elsewhere in the Northern Hemisphere. Approximately two thirds of the valleys are classified as ‘glacial’, some of which reflect active incision at the modern ice sheet margin, whereas others are situated beneath cold-based, slow-moving ice, indicating that they were incised under a different ice configuration earlier in Greenland's glacial history. The presence of ‘fluvial’ valleys in the low-lying interior of northern Greenland and in mountainous southern Greenland suggests parts of the inherited landscape formed under ice-free conditions during pre- or inter-glacial times have been preserved due to negligible long-term subglacial erosion rates. Some low-lying catchments show hallmarks of a combination of fluvial, glacial, and glacio-fluvial incision, hinting at complex interplays between valley-forming processes over the history of the Greenland Ice Sheet.

Wise Pattern versus Transverse Pattern Mastectomy in Two-Stage Implant-Based Breast Reconstruction: A Propensity Score-Matched Analysis.

The Wise pattern adapted to mastectomy incisions has become a valuable asset for breast reconstruction in patients with large and ptotic breasts. The authors compared the time for exchange, time to initiate postmastectomy radiotherapy, and complication rates between Wise pattern and transverse incision pattern reconstructions. Records of patients who underwent immediate, two-stage, implant-based breast reconstruction (IBBR) between January of 2011 and December of 2020 were retrospectively reviewed. Two cohorts were compared according to the incision pattern: Wise pattern versus transverse incision pattern. Complications were compared after propensity score matching. The authors initially analyzed 393 two-stage immediate IBBRs in 239 patients [91 IBBRs (23.2%) in the Wise pattern group and 302 (76.8%) in the transverse pattern group]. Expansion time (53 days versus 50 days, P = 0.9), time for tissue expander-to-implant exchange (154 versus 175 days, P = 0.547), and time to initiate postmastectomy radiotherapy (144 days versus 126 days, P = 0.616) were not different between groups. Before propensity score matching, the 30-day rate of wound-related complications (32% versus 10%, P < 0.001) and the 30-day rate of wound complications requiring excision/débridement and closure procedures (20% versus 7%, P < 0.001) were significantly higher in the Wise pattern group. After propensity score matching, the 30-day rate of wound complications was persistently higher (25% versus 10%, P = 0.03) in the Wise pattern group. The Wise pattern mastectomy independently increases the incidence of wound-related complications versus only transverse patterns during two-stage IBBR, even after propensity score matching. Delayed tissue expander placement may improve the safety profile of this procedure. Therapeutic, III.

Development and Characterization of Novel Anisotropic Skin Graft Simulants

Split-thickness skin grafting is a well-known procedure for the treatment of small- and medium-sized burns. However, its effectiveness has been reported to be limited in the case of large and severe burns due to much lower real expansion offered by the grafts than the claimed expansion by graft mesh manufacturers. Recent computational studies have indicated that the collagen fiber orientation within the skin layers have a significant effect on the skin graft expansion. In this study, biofidelic anisotropic synthetic skin with one and two layers and all possible fiber orientations were developed, and incision patterns used in traditional graft meshing techniques were projected to fabricate novel synthetic skin grafts with a theoretical meshing ratio of 3:1. A biaxial tensile testing device was designed to simulate skin graft stretching in clinical settings, and a wide range of synthetic skin graft variants were mechanically tested. The measured quantities included induced nonlinear stress–strain, void area, and meshing ratio. In addition, the stress–strain responses were characterized using nonlinear hyperelastic models. The key observations include the generation of higher induced stresses in two-layer grafts. In the one-layer graft models, a 15° fiber orientation produced the highest expansion at a minimal stress value of 0.21 MPa. In the two-layer graft models, the 45°–15° fiber orientation generated the maximum expansion with minimum stress. A range of such findings were analyzed to determine the graft orientations that may allow enhanced expansion without generating much stress. This information would be indispensable not only for understanding the expansion potential of skin grafts, but also for further research and the development of skin grafts with enhanced expansion for severe burn injury treatment.

61. Wise-pattern Versus Transverse Pattern Mastectomy in Two-stage Implant-Based Breast Reconstruction: A Propensity Score-matched Analysis

PURPOSE: The wise pattern adapted to the mastectomy incisions has become a valuable asset for breast reconstruction in patients with large and ptotic breasts. Herein, we compared the time for exchange, time to initiate postmastectomy radiotherapy (PMRT) and complications rate between reconstructions performed with wise pattern versus a transverse incision pattern. METHODS: We retrospectively reviewed the record of patients who underwent immediate two-stage implant-based reconstruction (IBBR) between January 2011 and December 2020. Two cohorts were compared according to the incision pattern: wise versus transverse incision pattern. Complications were compared after propensity score matching. RESULTS: We initially analyzed 393 two-stage immediate IBBR in 239 patients, 91 (23.2%) in the wise-pattern group and 302 (76.8%) in the transverse pattern group. The expansion time (53 days versus 50 days, p=0.9), the time for TE-to-implant exchange (154 versus 175 days, p=0.547), and the time to initiate PMRT (144 days versus 126 days, p=0.616) were not different between groups. Before propensity score matching, the 30-day rate of wound-related complications (32% versus 10%, p<.001) and 30-day rate of wound complications requiring E/D+C procedures (20% versus 7%, p<.001) were significantly higher in the wise-pattern group. After propensity score matching, the 30-day rate of wound-related complications persisted significantly higher (25% versus 10%, p=0.03) in the wise-pattern group. CONCLUSION: The wise pattern mastectomy independently increases the incidence of wound-related complications versus only transverse patterns during two-stage IBBR, even after propensity score matching. Delayed TE placement may improve the safety profile of this procedure.

Development of novel hierarchical designs for skin graft simulants with high expansion potential

Skin graft designs play an essential role in healing severe burn injuries. Split-thickness skin grafting (STSG) is one of the commonly used techniques for treating large burn injuries. In STSG, parallel cuts are projected onto a small portion of excised healthy skin for expansion and covering a larger burn area. To date, expansions reported for STSG are very low and insufficient to cover large burn areas. In this work, novel traditional and auxetic hierarchical cuts were designed on skin graft simulants, which were mechanically tested to study their expansion potential. Additive manufacturing and a two-part polymeric material were employed to fabricate the skin graft simulants. The nonlinear mechanical behavior of the hierarchical skin graft simulants was characterized using hyperelastic models. The effective Poisson’s ratio, meshing ratios, and induced stresses in first and second-order hierarchical cut patterns were estimated across all skin graft simulants for up to 300% strain. Also, Statistical analysis was performed to calculate the significance among the groups. From the analysis, the skin graft simulants with second-order auxetic incision patterns were found to exhibit the lowest induced stresses and maximum expansion of approximately four times, at 300% strain. To date, traditional skin grafts have only been able to achieve up to three times expansion. Therefore, the expansions realized with the novel hierarchical skin graft simulants is unprecedented, with the potential to generate ground-breaking advances in burn injury treatment.

Expansion potential of novel skin grafts simulants with I-shaped auxetic incisions

Skin grafts play an important role in treatment of severe burn injuries. Split-thickness skin grafting is one of the most common grafting technique, in which, parallel incision patterns are projected onto a small portion of excised skin for generating expansions and covering a larger burn site. However, to date, expansions reported through experiments on such grafts, have been much lower than claimed, which inhibits their application in severe burn injury mitigation. In this work, novel skin graft simulants were developed to study the expansion potential of skin grafts with I-shaped auxetic incision patterns. A range of I-shape dimensional parameters were tested, and the effective Poisson's effect, meshing ratios, and generated stresses, biaxial deformation and stress were estimated across all skin graft simulants, with strain loadings up to 200%. High spacing between I-shaped unit cells, was found to generate high negative Poisson's ratio and meshing ratio (MR). With high spacing, lowest stresses were generated for the maximum edge lengths of the I-shape. Maximum negative Poisson's ratio of -1.12 and meshing ratio of 3.84 were produced by the skin graft simulants, indicating expansions much higher than traditional skin grafts. Such results have not been realized with skin grafts to date, which would be indispensable for further research into skin graft expansions and treatment of severe burn injuries.

Finite element analysis of effect of incision pattern on stress analysis in brain tissue constrained in infancy

Finite element analysis of effect of incision pattern on stress analysis in brain tissue constrained in infancy