Microsurgical Free Tissue Transfer Research Articles

Impact of Resident and Attending Surgeon Training Level on Free Tissue Transfer Ischemia Time and Complications.

Microsurgical free tissue transfer has become an essential method for reconstruction of complex surgical defects, making the level of training an important factor to consider. There is little published regarding the impact of training level on microsurgical outcomes. This study investigates microsurgical free tissue transfer ischemia time and post-operative complications based on resident and attending surgeon experience level. A retrospective review of all free flaps at a single institution from 1/1/2013 to 12/31/2021 was performed. Linear regression was performed analyzing ischemia time of 497 free flaps and attending surgeon experience defined by years in practice and resident level defined as post graduate year (PGY). Logistic regression model was used to analyze complications based on attending experience and resident level. The average resident PGY was 3.5 +/- 0.8; the average attending has been practicing 6.4 +/- 5.1 years. There was no statistically significant difference in ischemia time or complication rates based on resident PGY or attending surgeon experience level. Lower PGY residents were not found to increase ischemia time or increase complication rates. Lower attending surgeon year was not found to increase ischemia time or increase complication rates compared to surgeons who had been practicing for longer. Microsurgical free tissue transfer is considered a safe procedure in residency training and trainee involvement should be encouraged to improve resident education and enhance technical skills.

Limb Salvage Using Microsurgical Free Tissue Transfer in Severe Frostbite.

Frostbite is often managed conservatively; however, in severe cases, microsurgical free tissue transfer is required for soft tissue coverage and limb salvage. Given its rarity, the techniques and outcomes of these cases are not well described. The purpose of this report is to present the largest case series, to date, of frostbite injuries requiring microsurgical reconstruction for limb salvage. A single-center retrospective review was conducted of all patients who underwent free tissue transfer by a single surgeon from 2008 to 2022. Patients of all ages were included if they suffered a frostbite injury requiring free tissue transfer. Demographics, operative details, and surgical outcomes were recorded. Eight patients with frostbite injuries were included in the report. Patients had frostbite injuries either to the lower extremities (n = 4) or to both upper and lower extremities (n = 4). Sixteen free flaps were done in total including four paired chimeric and eight single free flaps. Flap recipient sites included knees (n = 5), foot/ankle (n = 3), dorsal hands (n = 2), and thumbs (n = 2). All 16 flaps survived. Five patients had complications: four with major complications requiring operative management and two with minor complications requiring conservative management. Mean follow-up time was 505.7 days (range 115-1564). All lower extremity reconstructions were able to weight-bear at an average of 125.2 days post-injury (range 87-164). This case series demonstrates that free tissue transfer is a robust option for soft tissue coverage and functional limb salvage in patients with severe frostbite injuries to both upper and lower extremities.

Managing Vascular Pedicle Exposure in Free Tissue Transfer Using a Reprocessed Micronized Dermal Substitute in Lower Extremity Reconstructions.

Lower extremity reconstruction is challenging because of its intricate anatomy and dynamic biomechanics. Although microsurgical free tissue transfer offers pivotal solutions to limited local tissue availability, vascular pedicle exposure after free tissue transfer is common. We evaluated a novel method of managing pedicle exposure after free tissue transfer using a reprocessed micronized dermal substitute. Ten patients who underwent lower-extremity reconstruction using free tissue transfer and micronized dermal substitute between January and December 2023 were retrospectively reviewed. When native tissue could not be closed over the pedicle, reprocessed micronized artificial dermal matrix (rmADM) was cut and stacked to protect and stabilize it. Epithelialization was achieved by secondary skin grafting or healing by secondary intention. Flap dimensions, recipient artery and vein, ADM size, time required for granulation tissue maturation and complete epithelialization, and flap outcomes were analyzed. The mean age was 55.80 ± 20.70 years, and six patients (60%) were diabetic. The mean rmADM coverage area was 8.70 ± 8.41 cm2, and the average time required for complete epithelialization was 50.89 ± 14.21 days. Except for one total necrosis due to bypass graft failure, nine limbs were successfully salvaged. Application of rmADM offers numerous advantages, including vascular collapse prevention, moisture maintenance, granulation tissue growth promotion, and pedicle stabilization.

Diagnostical accuracy of hyperspectral imaging after free flap surgery.

Microsurgical free-tissue transfer has been a safe option for tissue reconstruction. This study aimed to analyze the diagnostic accuracy of hyperspectral imaging (HSI) after free-tissue transfer surgery. From January 2017 to October 2019, 42 consecutive free-flap surgeries were performed, and their outcomes were analyzed via HSI. Clinical examination of free-flap perfusion was initially performed. Clinical examination findings were subsequently compared with those of HSI. Potential venous congestion with subsequent necrosis was defined as a tissue hemoglobin index of ≥53%. Student's t-test was used to compare the results of the analysis. The evaluation of sensitivity and specificity for flap failure detection was time dependent using the Fisher's exact test. A p-value of ≤0.05 was considered statistically significant. Microsurgical tissue transfer success rate was 84%. Seven patients presented with venous congestion that caused total flap necrosis. Overall, 124 assessments were made. HSI accurately identified 12 out of 19 pathological images: four as false positive and seven as false negative. The sensitivity and specificity of HSI were 57 and 94%, respectively, compared to those of clinical examination that were 28 and 100%, respectively, within 24 h following tissue transfer. The sensitivity and specificity of HSI were 63 and 96%, respectively, compared to those of clinical examination that were 63 and 100%, respectively, within the first 72 h. A tissue hemoglobin index of ≥53% could predict venous congestion after free-flap surgery. HSI demonstrated higher sensitivity than clinical examination within the first 24 h; however, it was not superior compared to clinical findings within 72 h.

The posterior approach to the thoracodorsal vessels for microsurgical free tissue transfer

The latissimus dorsi (LD) muscle is a workhorse flap in reconstructive surgery (e.g., breast reconstruction, chest wall defects, and lower limb trauma). The thoracodorsal artery and its venae comitantes supply this muscle. Recipient vessel options for microsurgical free flap reconstruction of the posterior thorax and lower back are limited. The thoracodorsal vessels are an excellent option due to their reliable anatomy and ease of access. In circumstances when the patient is best positioned prone, the posterior approach to access the thoracodorsal vessels is advantageous. We describe the technique to identify and isolate these vessels via a posterior approach.

Functional and contour restoration in severely injured extremities - our approach to reconstruct composite (Multizonal) injuries of foot and ankle

BackgroundCoverage of ankle and foot defects has been challenging. This study highlights the importance of microsurgical free tissue transfer as an opportunity for a surgeon to deal with composite foot defects with variable etiology. MethodA retrospective case review of 28 patients with large Multizonal foot defects resulting from trauma and tumor resections presented to tertiary care hospitals from 2008-to 2021. All defects were reconstructed by free flaps. 14 patients had ALT flaps, 4 underwent free fibula flaps, and 6 had LD flaps and 4 Rectus Abdominis free flaps. Different modalities have been reviewed by literature for the type of flap used, zone involvement, and age groups. Result26 patients were male and 2 females. Most of our patients were adults presenting post-trauma including n ​= ​21 (75%) road traffic accidents n ​= ​17 (60.7%), mine blast injury n ​= ​4 (14.2%), and malignancy in n ​= ​3 (10.7%). Age range was from 5 years to 75 years. Most of the patients had involvement of subunits 3 and 4 followed by a combination with other sub-units. After free microsurgical tissue transfer, 2 patients needed immediate exploration, one had arterial compromise and one had venous insufficiency. All flaps survived. 3 patients underwent flap debulking in the follow-up period. All patients were followed for 2 years and returned to daily activities and near to normal ambulation. ConclusionMicrosurgical free tissue transfer has not only proven its role in post-traumatic composite foot defects but also in malignancies where resection with free margins followed by foot reconstruction poses a major challenge.

131. The Impact of Intraoperative Temperature on Venous Thromboembolism and Flap Pedicle Thrombosis in Patients Undergoing Head and Neck Microsurgical Reconstruction

PURPOSE: In vitro studies on platelet function have shown that lower temperatures encourage aggregation and overexpression of the adhesion molecules. Anesthesia guidelines recommend the prevention of hypothermia (T < 36 º). This study aims to explore the impact of intraoperative body temperature on venous thromboembolism (VTE) and flap pedicle thrombosis within 30 days of microsurgical free tissue transfer surgery to the head and neck. METHODS: All patients who underwent head and neck reconstruction with free tissue transfer from January 2012 through March 2022 in a tertiary center were included in this study. Data were collected from a retrospective and prospective held database. Intraoperative temperature readings were extracted electronically in one-minute intervals for each surgery. Non-physiologic readings less than 30 or more than 42 were discarded. A median was calculated for every five consecutive readings to create a five-minute temperature reading. A median value under 36 º was considered an onset of hypothermia. VTE events and thrombosis of the free flap pedicle (arterial or venous) that require revision surgery were the study outcomes, and they were recorded within 30 days of the index surgery. RESULTS: 895 patients were included, and out of those n=300, 34% were females. The mean intraoperative body temperature and Caprini score for the whole cohort were 36.13 ± 1.08 º and 6.54 ± 1.74. The VTE and pedicle thrombosis rates were (n=37, 4.0%) and (n=58, 6%), respectively. The incidence of patients developing at least one onset of hypothermia was (n=720, 80%). The mean number of hypothermia onsets and the mean length of surgery were 52.40 ± 84.80 and 685.12 ± 144.31 minutes, respectively. The mean for Caprini score in those who developed at least one onset of hypothermia did not differ significantly from those who were normothermic (≥ 36 º) for the whole surgery (6.55±1.76 vs. 6.46±1.60, p=0.533). The rate of VTE in those who experienced at least one onset of hypothermia was significantly higher than in those who were normothermic for the whole surgery (n=35/720, 3.9% vs. n=2/175, 0.22%, p=0.026). This association persisted even after controlling for the Caprini score, the number of hypothermic onsets, and the length of surgery in a multivariable regression model (OR, 5.478, 95%CI: 1.222-24.557). In contrast, the rate of free flap pedicle thrombosis was lower in patients who experienced hypothermia than others in the cohort (n=9/175, 1.01% vs. n=49/720, 5.47%). However, the difference failed to reach a statistical significance (p=0.422). CONCLUSIONS: Hypothermia onset is associated with an increased rate of VTE postoperative, even after controlling for the number of hypothermia onsets, Caprini score, and length of surgery. Patients who experienced hypothermia during surgery had a lower incidence of free flap pedicle thrombosis than those who were normothermic throughout the surgery. However, no conclusion can be made about the impact of hypothermia on pedicle thrombosis since the difference failed to reach statistical significance.

Evidence based recommendations for perioperative vasopressor use and fluid resuscitation in microsurgery.

Blood pressure regulation is critical in patients undergoing microsurgical free tissue transfer; however, guidelines for addressing and preventing perioperative hypotension remain highly debated, with two current thought paradigms: (1) intravenous fluid administration with a balanced salt solution (e.g., lactate ringer and normal saline) and/or colloid (e.g., albumin) and (2) vasoactive pharmacological support with vasopressors (e.g., dobutamine, norepinephrine, epinephrine), with fluid administration being the preferred conventional approach. Here, we review the most up to date available literature and summarize currents perspectives and practices for fluid resuscitation and vasopressor use, while offering evidence-based guidelines to each.

Secondary Surgery after Lower Extremity Free Flap Reconstruction.

Microsurgical free tissue transfer may be the only reconstructive option for lower extremity limb salvage. However, the functional and aesthetic results following free tissue transfer after initial salvage may be suboptimal, thus requiring secondary operations to facilitate definitive wound healing and/or refinement. A multi-institutional retrospective cohort study was performed including patients who underwent lower extremity free tissue transfer from January of 2002 to December of 2020. The authors' primary outcome variable was the presence of secondary surgery after free tissue transfer for lower extremity reconstruction. Independent variables (eg, wound cause, flap, donor type, recipient, comorbidities) were collected. Secondary surgery was categorized as (1) procedures for definitive wound closure and (2) refinement procedures. Multivariable logistic regression was performed to determine which variables were independently associated with the outcome. A total of 420 free tissue transfers for lower extremity reconstruction were identified. Secondary surgery was performed in over half (57%) of the patients. Presence of diabetes (OR, 2.0; P = 0.01; 95% CI, 1.2 to 3.5) and use of a latissimus dorsi donor (OR, 2.4; P = 0.037; 95% CI, 1.1 to 5.4) were predictors of wound closure procedures. Fasciocutaneous (OR, 3.6; P < 0.001; 95% CI, 1.8 to 7.2) and myocutaneous (OR, 3.0; P = 0.005; 95% CI, 1.5 to 9.9) flaps were predictors of refinement procedures when compared with muscle-only flaps with skin grafts. The majority of lower extremity free tissue reconstructions required secondary procedures to provide definitive wound closure and/or refinement. Overall, this study provides predictors of secondary surgery that will help formulate patients' expectations of lower extremity limb salvage. Risk, III.

Deep Learning for Personalized Preoperative Planning of Microsurgical Free Tissue Transfers

Breast reconstruction surgery requires extensive planning, usually with a CT scan that helps surgeons identify which vessels are suitable for harvest. Currently, there is no quantitative method for preoperative planning. In this work, we successfully develop a Deep Learning algorithm to segment the vessels within the region of interest for breast reconstruction. Ultimately, this information will be used to determine the optimal reconstructive method (choice of vessels, extent of the free flap/harvested tissue) to reduce intra- and postoperative complication rates.

Systematic Review and Guidelines for Perioperative Management of Pediatric Patients Undergoing Major Plastic Surgery Procedures, with a Focus on Free Tissue Transfer.

Microsurgical free tissue transfer has been successfully implemented for various reconstructive applications in children. The goal of this study was to identify the best available evidence on perioperative management of pediatric patients undergoing free tissue transfer and to use it to develop evidence-based care guidelines. A systematic review was conducted in the PubMed, Embase, Scopus, and Cochrane Library databases. Because a preliminary search of the pediatric microsurgical literature yielded scant data with a low level of evidence, pediatric anesthesia guidelines for healthy children undergoing major operations were also included. Exclusion criteria included vague descriptions of perioperative care, case reports, and studies of syndromic or chronically ill children. Two hundred four articles were identified, and 53 met inclusion criteria. Management approaches specific to the pediatric population were used to formulate recommendations. High-quality data were found for anesthesia, analgesia, fluid administration/blood transfusion, and anticoagulation (Level I Evidence). Lower quality evidence was identified for patient temperature (Level III Evidence) and vasodilator use (Level IV Evidence). Key recommendations include administering sevoflurane for general anesthesia, implementing a multimodal analgesia strategy, limiting preoperative fasting, restricting blood transfusions until hemoglobin level is less than 7 g/dl unless the patient is symptomatic, and reserving chemical venous thromboembolism prophylaxis for high-risk patients. Pediatric-specific guidelines are important, as they acknowledge physiologic differences in children, which may be overlooked when extrapolating from adult studies. These evidence-based recommendations are a key first step toward standardization of perioperative care of pediatric patients undergoing plastic surgical procedures, including free tissue transfer, to improve outcomes and minimize complications.

Potential application of dental stem cells in regenerative reconstruction of oral and maxillofacial tissues: a narrative review.

Background and Objective:Oral and maxillofacial (OMF) defects caused by congenital conditions, injuries, ablative surgery for benign and malignant head & neck tumor, can often lead to OMF deformities and malfunctions in speech, mastication/chewing, and swallowing as well as have deleterious psychological effects and socioeconomic burdens to patients. Due to the unique complex 3D geometry of the head and neck region, reconstruction and rehabilitation of OMF defects remain a major challenge for OMF surgeons.The purpose of this narrative review is to update the information on the biological properties and functions of mesenchymal stem cells derived from various dental tissues (dental-MSCs) and their potential application in tissue engineering (TE) and regenerative reconstruction of OMF tissues.Methods:A data-based search was performed by using PubMed database whereby articles published between 2000 and 2021 in English were included in the search with the following key words: dental stem cells, OMF reconstruction, OMF TE and regeneration.Key Content and Findings:Currently, the advancement in stem cell biology, biomaterial science, and TE technology has demonstrated the significant potential application of stem cell-based therapy in regenerative reconstruction and rehabilitation of OMF defects. However, no stem cell-based product or device has been translated into clinical application to replace microsurgical free tissue transfer, the current mainstay of care in the reconstruction of OMF defects.Conclusions:Currently, microsurgical free tissue transfer remains the gold standard mainstay of care for the reconstruction of OMF defects due to their abundant blood supply and flexibility for transplantation. However, several major challenges, such as the limited availability, the requirement of a second surgery, donor site morbidity, and the risk of free flap failure, have promoted the development of novel approaches. Due to the advancement in stem cell biology, biomaterial science, and TE technology, stem cell-based regenerative therapy is emerging as a promising therapeutic approach for a variety of diseases, including regenerative reconstruction and rehabilitation of OMF defects. In this narrative review, we update on the characteristics and biological functions of mesenchymal stem cells derived from various dental tissues (dental-MSCs) and their released cell-free products, extracellular vesicles (EVs). We also highlighted their potential application in TE and regenerative reconstruction of OMF defects in animal models and clinical studies and the potential challenges in this field.

Wireless implantable optical probe for continuous monitoring of oxygen saturation in flaps and organ grafts

Continuous, real-time monitoring of perfusion after microsurgical free tissue transfer or solid organ allotransplantation procedures can facilitate early diagnosis of and intervention for anastomotic thrombosis. Current technologies including Doppler systems, cutaneous O2-sensing probes, and fluorine magnetic resonance imaging methods are limited by their intermittent measurements, requirements for skilled personnel, indirect interfaces, and/or their tethered connections. This paper reports a wireless, miniaturized, minimally invasive near-infrared spectroscopic system designed for uninterrupted monitoring of local-tissue oxygenation. A bioresorbable barbed structure anchors the probe stably at implantation sites for a time period matched to the clinical need, with the ability for facile removal afterward. The probe connects to a skin-interfaced electronic module for wireless access to essential physiological parameters, including local tissue oxygenation, pulse oxygenation, and heart rate. In vitro tests and in vivo studies in porcine flap and kidney models demonstrate the ability of the system to continuously measure oxygenation with high accuracy and sensitivity.

Use of arteriovenous loop vein graft in the microsurgical free tissue transfer: A Case Report

In reconstructions after severe traumatic injuries of the lower extremity, free tissue transfers are essentially used to cover the defects and accepted as extremity saving procedures. When major vessels of the lower extremity are patent or uninjured, these vessels can be used for anastomoses in free tissue transfers, however, in some injuries, only one major vessel remains intact and concomitant endothelial damage might also be present in this vessel. In such cases, since the nourishment of the extremity is dependent on this single vessel, its use as a recipient vessel may be risky for the perfusion of the extremity. In such cases, bringing an additional and healthy recipient vessel to the field is a useful option. Loop vein grafts are normally created by vascular surgeons for dialysis patients, and reconstructive surgeons often do not have much experience in this procedure. In this study, it was aimed to give information about the decision making progress that we used during and after the operation by presenting a 32-year-old case who had been admitted with a mangled extremity severity score (MESS) score of seven and a Gustilo-Anderson Type 3C lower extremity injury after a traumatic motorcycle accident injury. It is considered to be helpful for our colleagues who have not used loop grafts in reconstructive microsurgery operations before.

Microvascular Free Tissue Transfer for Reconstruction of Complex Abdominal Wall Defects.

Patients with significant loss of abdominal wall soft tissue represent a reconstructive challenge. The purpose of this study was to describe the authors' experience using microvascular free tissue transfer to repair complex abdominal wall defects with insufficient overlying soft tissue. In this report, the authors highlight their techniques and experiences in performing microvascular free tissue transfer to the abdominal wall for these massive, complex defects. In total, 14 patients who underwent 16 free-flap reconstructions were included in the series. The patients' mean age was 50 ± 14 years, and mean body mass index was 27 ± 5 kg/m2. The mean hernia defect size was 412 ± 149 cm2. Ten flaps were fasciocutaneous anterolateral thigh flaps, one myocutaneous anterolateral thigh flap, two subtotal thigh flaps, one myocutaneous latissimus dorsi flap, one parascapular/latissimus dorsi flap, and one free filet of the lower leg. Five cases (36 percent) developed hernia recurrence, and seven developed surgical site complications. All flaps survived, with no total flap loss. This report highlights that microsurgical free tissue transfer in combination with mesh repair is a safe and reliable method for restoring complex, large, full-thickness abdominal wall defects. This case series illustrates a number of techniques and considerations that are of importance to achieve a favorable outcome when faced with these complex defects. Therapeutic, IV.

75 Years of Excellence: The Story of Reconstructive Surgery

75 Years of Excellence: The Story of Reconstructive Surgery

One or two venous pedicles by anastomoses for free flaps in reconstruction of the lower extremity: A systematic review and meta-analysis.

Microsurgical free tissue transfers are a mainstay of lower extremity reconstruction. Despite being a reliable source of soft tissue, complications do arise. Venous congestion is among the most common causes of flap failure in lower extremity reconstruction, an issue that is attributed to venous stasis and impaired venous return in this region. There remains significant debate whether dual venous drainage improves outcomes. The aim of this study was thus to compare one versus two venous anastomoses in lower limb free flap reconstruction. A systematic review of Medline, EMBASE, EBSCO CINAHL, SCOPUS, Proquest Dissertations and Theses Global, Cochrane Library, and PROSPERO from inception to May 20, 2020, was conducted. Two independent reviewers screened titles and extracted data. Our primary outcome was total free flap necrosis. Secondary outcomes were partial flap necrosis, minor complications, flap reoperation, venous thrombosis, and amputation. Methodological quality was assessed using the MINORS criteria and level of evidence. Three-hundred and fourteen unique titles were identified. All studies were level VI evidence and had a mean MINORS score of 16.1/24. Seven studies (comprising 1499 patients, 910 single venous anastomoses, and 579 double venous anastomoses) met criteria for inclusion. The mean (SD) patient age was 46.5 (7.1) years. Double venous anastomoses did not reduce the rate of minor complications, flap takeback, venous thrombosis, total flap necrosis, or partial flap necrosis when compared to a single vein (all p > .05). In microvascular lower extremity reconstruction, two venous anastomoses did not reduce the rate of minor or major complications.

Protocol for a systematic review of outcomes from microsurgical free-tissue transfer performed on short-term collaborative surgical trips in low-income and middle-income countries

BackgroundIn many units around the world, microsurgical free-tissue transfer represents the gold standard for reconstruction of significant soft tissue defects following cancer, trauma or infection. However, many reconstructive units in low-income and middle-income countries (LMICs) do not yet have access to the resources, infrastructure or training required to perform any microsurgical procedures. Long-term international collaborations have been formed with annual short-term reconstructive missions conducting microsurgery. In the first instance, these provide reconstructive surgery to those who need it. In the longer-term, they offer an opportunity for teaching and the development of sustainable local services.MethodsA PRISMA-compliant systematic review and meta-analysis will be performed. A comprehensive, predetermined search strategy will be applied to the MEDLINE and Embase electronic databases from inception to August 2021. All clinical studies presenting sufficient data on free-tissue transfer performed on short-term collaborative surgical trips (STCSTs) in LMICs will be eligible for inclusion. The primary outcomes are rate of free flap failure, rate of emergency return to theatre for free flap salvage and successful salvage rate. The secondary outcomes include postoperative complications, cost effectiveness, impact on training, burden of disease, legacy and any functional or patient reported outcome measures. Screening of studies, data extraction and assessments of study quality and bias will be conducted by two authors. Individual study quality will be assessed according to the Oxford Evidence-based Medicine Scales of Evidence 2, and risk of bias using either the ‘Revised Cochrane risk of bias tool for randomized trials’ (Rob2), the ‘Risk of bias in non-randomized studies of interventions’ (ROBINS-I) tool, or the National Institute for Health Quality Assessment tool for Case Series. Overall strength of evidence will be assessed according to the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach.DiscussionTo-date the outcomes of microsurgical procedures performed on STCSTs to LMICs are largely unknown. Improved education, funding and allocation of resources are needed to support surgeons in LMICs to perform free-tissue transfer. STCSTs provide a vehicle for sustainable collaboration and training. Disseminating microsurgical skills could improve the care received by patients living with reconstructive pathology in LMICs, but this is poorly established. This study sets out a robust protocol for a systematic review designed to critically analyse outcomes.Systematic review registrationPROSPERO 225613

Toward Adipose Tissue Engineering Using Thiol-Norbornene Photo-Crosslinkable Gelatin Hydrogels.

Nowadays, breast implants, lipofilling, and microsurgical free tissue transfer are the most often applied procedures to repair soft tissue defects resulting from mastectomies/lumpectomies following breast cancer. Due to the drawbacks and limitations associated with these conventional clinical practices, there is a need for alternative reconstructive strategies. The development of biomimetic materials able to promote cell proliferation and adipogenic differentiation has gained increasing attention in the context of adipose reconstructive purposes. Herein, thiol-norbornene crosslinkable gelatin-based materials were developed and benchmarked to the current commonly applied methacryloyl-modified gelatin (GelMA) with different degrees of substitutions focussing on bottom-up tissue engineering. The developed hydrogels resulted in similar gel fractions, swelling, and in vitro biodegradation properties compared to the benchmark materials. Furthermore, the thiol-ene hydrogels exhibited mechanical properties closer to those of native fatty tissue compared to GelMA. The mechanical cues of the equimolar GelNB DS55% + GelSH DS75% composition resulted not only in similar biocompatibility but also, more importantly, in superior differentiation of the encapsulated cells into the adipogenic lineage, as compared to GelMA. It can be concluded that the photo-crosslinkable thiol-ene systems offer a promising strategy toward adipose tissue engineering through cell encapsulation compared to the benchmark GelMA.

Reconstruction of traumatic and non-traumatic lower extremity defects with local or free flaps

Summary Background Despite continuous surgical advances, reconstruction of complex lower extremity wounds remains challenging. The indication of local flaps or microsurgical free tissue transfer depends on the anatomical location and size of the defect, as well as the comorbidities and general condition of the patient. In this study, local and free flap reconstruction of distal lower extremity defects was assessed, and postoperative complications and limb salvage were analyzed. Methods A total of 34 patients were included in this retrospective study. Distal lower extremity defects were of traumatic (29%) and non-traumatic (71%) etiologies. Patient characteristics, flap selection, postoperative complications, and limb preservation within the first 12 months were assessed and compared by reconstructive treatment concept. Statistical analysis included parametric and non-parametric tests. The two-sided alpha was set at 5% for all statistical tests. Results While 21 patients were treated with local flaps, 13 patients underwent microsurgical free flap reconstruction. The most common comorbidities were peripheral vascular disease and diabetes. Local flaps included the gastrocnemius muscle flap, soleus flap, sural flap, and plantaris medialis flap. The most commonly used free flaps for soft tissue reconstruction were latissimus dorsi and gracilis muscle flaps. The overall lower extremity preservation rate was 94.1%. There was one case of below-knee amputation 1 month after free flap reconstruction, and one case of first-ray amputation of the foot after local flap coverage. Conclusion Reconstruction of lower extremity defects can be achieved by local or free flap reconstruction. Flap selection is influenced by anatomical location, defect size, and patient factors.