Development of a mathematical formula and online tool to calculate the potential maximum flap width to allow for primary anterolateral thigh donor-site closure in Caucasians.

BACKGROUND: Primary anterolateral thigh (ALT) flap donor-site closure is crucial to achieve patient satisfaction, avoid burdensome secondary surgeries, and avert poor outcomes. Only vague maximum flap width recommendations have been suggested, which fall short of acknowledging individual patient habitus and thigh morphology. Therefore, we aimed at identifying a user-friendly preoperative calculation of maximum flap width for primary closure. METHODS: A total of 429 ALT free flaps performed between 2009 and 2020 were analyzed. A total of 350 donor-sites were closed primarily (82%) and 79 (18%) were split-thickness skin-grafted (STSG). Patient demographics including sex, age, and BMI, operative details, and flap characteristics were compared to assess their impact on the outcome variable. Receiver operating characteristic (ROC) curves were plotted for all significant predictors discriminating between closure and STSG. Areas under the curve (AUCs) were calculated for each parameter combination and optimal cutoffs were determined using Youden's Index. RESULTS: Sex, age, BMI, and flap width alone were poor discriminators. Dividing flap width by BMI and logarithmized BMI yielded AUCs of 0.91 and 0.94, respectively. Including patient sex yielded the best fitting regression model (χ2  = 251.939, p < .0001) increasing the AUC to 0.96 (95% CI: 0.93-0.98, p < .0001). The optimal cutoff value discriminated between primary closure and STSG with 90% sensitivity and 89% specificity. An online calculator of patient-individual maximum ALT width was then programmed. CONCLUSIONS: Sex and BMI are reliable predictors of successful primary ALT donor-site closure in Caucasians. We devised a novel formula for calculating patient-individual maximum ALT widths preoperatively, predicting failure of primary closure with 90% sensitivity in our cohort, available at: https://kitteltaschenbuch.com/altwidth/calculate.htm.

Revisionary soft tissue reconstruction of posterior midline defects after spinal surgery-plastic reconstructive options including perforator flaps.

BACKGROUND: Chronic prevertebral soft tissue defects with exposed metal hardware following spinal surgery represent a challenging complication. Frequently patients underwent multiple previous operations due to wound complications. Surrounding soft tissues are often compromised due to malperfusion, severe subcutaneous scarring, previous local advancement flaps and therefore impair stable wound closure. METHODS: Patients after spinal surgery who received complex soft tissue reconstructions between 2011 and 2015 were analyzed retrospectively. Patient`s age, risk factors, wound size, cause and defect location as well as complication rates were evaluated. A focus was set on therapeutic strategies and decision-making concerning reconstructive techniques. RESULTS: Fourteen patients receiving 27 pedicled and one free flap were included in the study. Patients mean age was 51.1 years, mean wound size was 144 cm2. Defects were located in the lumbar spine [8], cervical spine [2] and thoracic spine [1], respectively. Three patients suffered from extensive defects affecting more than one area. Mean time of flap surgery was 213 minutes. Fifteen perforator-based flaps and 11 non-perforator (classic rotation-flaps), 1 pedicled and 1 free latissimus dorsi flap were used. In 9 patients (64.3%) different flaps had to be combined in a single-staged procedure due to large wounds. Implant material was removed completely in six patients (42.9%), whereas in five patients (35.7%) implants were replaced within the operation for soft tissue reconstruction. In three patients (21.4%) initial implant removal or replacement was not possible which leads to prolonged postoperative wound infections. CONCLUSIONS: Most patients with exposed spinal hardware suffered from multiple comorbidities and showed a poor general condition. Due to the reduced soft tissue quality wound healing is significantly impaired. Exposed implant material should be replaced or removed when possible. Therefore, the complete armamentarium of plastic reconstructive techniques is required for wound closure. Today, perforator flaps play a prominent role due to the variability, excellent vascularization and sufficient subcutaneous filling capacities.

Perforator-Based Flaps for Defect Reconstruction of the Posterior Trunk.

INTRODUCTION: Full-thickness soft tissue defects of the back remain challenging clinical problems for reconstructive surgeons. Among a vast variety of local flap options, perforator-based local flaps gain increasing popularity lately. Because mostly heterogeneous patient cohort comparison of different perforator flaps is difficult and decision-making algorithms are lacking. METHODS: Patients, who received a local perforator-based soft tissue reconstruction between 2012 and 2019, were evaluated retrospectively. Patients' data were evaluated in terms of flap type and dimension, wound size and cause, surgery time, postoperative complications, and hospitalization. A focus was set on decision making concerning reconstructive techniques and flap choice for defect closure. RESULTS: Thirty-six patients (17 women, 19 men) were included, who received 40 perforator-based local flaps to reconstruct extended defects of the posterior trunk. Mean patient age was 56.3 years and mean hospitalization was 29 days. Average time of flap surgery was 179.7 minutes. Mean flap size was 160.8 cm and average defect size was 110 cm. Defects occurred because of tumor resection (50%), orthopedic/trauma surgery (16.7%), or pressure sores (33.3%). Twenty-eight propeller flaps (PPFs, 70%) and 12 perforator-based VY-advancement flaps (P-VYF, 30%) were transferred. In 4 patients, a bilateral approach using more than one flap was necessary. Revision surgery was required in 9 patients (25%) because of postoperative hematoma (n = 3), postoperative wound infection (n = 3), partial flap necrosis (1× P-VYF) and 2 flap losses (2× PPFs). CONCLUSIONS: Pedicled perforator flaps are a reliable option for soft tissue reconstruction of complex wounds of the posterior trunk. A flexible surgical strategy is mandatory, and the individual perforator anatomy has to be considered. In most cases, P-VYFs or PPFs are reliably possible and allow sufficient defect reconstruction. However, skin incisions should always be performed in a way that classic random pattern flaps are still possible. Even in large defects combined, local perforator flaps may lead to sustainable soft tissue reconstructions without functional donor site deficits.

Feasibility and safety of enzymatic debridement for the prevention of operative escharotomy in circumferential deep burns of the distal upper extremity.

BACKGROUND: Burn-induced compartment syndrome is a severe sequela after circumferential burns of the extremities and is avoidable by immediate release of the underlying pressure under the eschar. Although the current gold standard is operative escharotomy, this procedure carries considerable morbidity. Our study evaluates the safety and effectiveness of immediate enzymatic debridement to prevent the need for operative escharotomy because of burn-induced compartment syndrome in selected patients. PATIENTS AND METHODS: From 2015 to 2017, all patients suffering from deep circumferential burns of the upper extremities requiring operative escharotomy were potential candidates for the treatment algorithm evaluated by this study. Exclusion criteria involved burn trauma > 12 hours, clinically established burn-induced compartment syndrome, intolerance to the enzymatic debriding agent, dry burns requiring presoaking, as well as blast and electrical injuries requiring fasciotomy or carpal tunnel release. All patients with the inclusion criteria received enzymatic debridement with Nexobrid immediately after admission to our burn center. Enzymatic debridement was applied according to the manufacturer's recommendations. After enzymatic debridement, extremities were revisited every 2 hours for 24 hours to determine the need for conversion to conventional operative escharotomy. The indication for and time to skin grafting was reviewed, and functional outcomes assessed during follow-up examination. RESULTS: Included in this sturdy were 13 patients with 20 burned upper extremities. Enzymatic debridement provided a sufficient eschar removal in all patients. Conversion to conventional operative escharotomy was thus not necessary in any patient. Secondary skin grafting was required in 9 patients. Functional outcomes were favorable 11.9 months after burn trauma. CONCLUSION: If the specific contraindications are respected, enzymatic debridement is safe and effective for the prevention of burn-induced compartment syndrome after deep circumferential burns at the upper extremity, and thus making operative escharotomy unnecessary.

Pyoderma gangrenosum following complex reconstruction of a large-scale lower limb defect by combined Parascapular and latissimus dorsi flap.

A female patient with a critical soft tissue defect after elective knee replacement surgery was transferred to our department for reconstruction. As wounds were rapidly progressing, necrotizing fasciitis was initially suspected but eventually ruled out by histopathological analysis. A 50 × 15 cm defect was then reconstructed by means of a combined Parascapular and latissimus dorsi flap before, a couple days later, the patient developed tender pustules and ulcers involving the flap as well as the donor site. Attempts of excising necrotic areas not only continued to fail but seemed to worsen the patient's wound and overall condition. Eventually, pyoderma gangrenosum (PG) was diagnosed and local and systemic therapy was initiated but treatment proved to be challenging and insufficient at first. Being an extremely aggressive disease, early diagnosis is crucial and PG should always be suspected when rapidly progressive ulceration on surgical sites is observed.

Enzymatic debridement for the treatment of severely burned upper extremities - early single center experiences.

BACKGROUND: Severe burns of hands and arms are complex and challenging injuries. The Standard of care (SOC) - necrosectomy with skin grafting - is often associated with poor functional or aesthetic outcome. Enzymatic debridement (ED) is considered one promising alternative but, until recently, results proved to be highly variable. METHODS: Between 04/2014 and 04/2015, 16 patients with deep partial- to full-thickness burns of the upper extremities underwent enzymatic debridement (ED) in our Burn Center and were evaluated for extent of additional surgery, wound healing, pain management and functional parameters. RESULTS: Following ED, no further surgical intervention was required in 53.8 % of the study population. In patients who required surgical treatment, the the skin-grafted area could be reduced by 37.0 % when compared to initial assessment. Time from injury to ED was 24.4 h and patients were able to start physical therapy after 2.0 days but suffered from prolonged wound closure (28.0 days). Regionally administered anesthesia proved to be superior to pain medication alone as pain levels and consumed morphine-equivalent were lower. Post-demission follow-up showed good functional results and pain levels with low scores in two self-report questionnaires (DASH, PRWE-G) but 3 patients reported increased susceptibility to shear stress. Based on these early experiences, we developed a 3-step algorithm for consecutive patients allowing appropriate and individualized treatment selection. CONCLUSIONS: We see a potential benefit for ED in the treatment of severely burned hands and forearms but further investigations and proper prospective, randomized controlled trials are needed to statistically support any outlined assumptions.

mTORC2 critically regulates renal potassium handling.

The mTOR pathway orchestrates cellular homeostasis. The rapamycin-sensitive mTOR complex (mTORC1) in the kidney has been widely studied; however, mTORC2 function in renal tubules is poorly characterized. Here, we generated mice lacking mTORC2 in the distal tubule (Rictorfl/fl Ksp-Cre mice), which were viable and had no obvious phenotype, except for a 2.5-fold increase in plasma aldosterone. Challenged with a low-Na+ diet, these mice adequately reduced Na+ excretion; however, Rictorfl/fl Ksp-Cre mice rapidly developed hyperkalemia on a high-K+ diet, despite a 10-fold increase in serum aldosterone levels, implying that mTORC2 regulates kaliuresis. Phosphorylation of serum- and glucocorticoid-inducible kinase 1 (SGK1) and PKC-α was absent in Rictorfl/fl Ksp-Cre mice, indicating a functional block in K+ secretion activation via ROMK channels. Indeed, patch-clamp experiments on split-open tubular segments from the transition zone of the late connecting tubule and early cortical collecting duct demonstrated that Ba2+-sensitive apical K+ currents were barely detectable in the majority of Rictorfl/fl Ksp-Cre mice. Conversely, epithelial sodium channel (ENaC) activity was largely preserved, suggesting that the reduced ability to maintain K+ homeostasis is the result of impaired apical K+ conductance and not a reduced electrical driving force for K+ secretion. Thus, these data unravel a vital and nonredundant role of mTORC2 for distal tubular K+ handling.

Influences of Macrohemodynamic Conditions on Systemic Microhemodynamic Changes in Burns.

PURPOSE: The clinical course after major burns is characterized by microcirculatory changes and consecutive capillary leakage. However, current clinical monitoring does not properly assess microcirculation, whereas macrohemodynamic changes are continuously evaluated. Here, we assess if macrohemodynamic and microhemodynamic parameters after burn trauma are correlated in a rat model. METHODS: Burn plasma harvested from donor rats 4 hours after thermal injury (30% total body surface area, 100 °C water, 12 seconds) was administered intravenously to healthy animals during 2 hours of intravital microscopy (burn group [BG]). Shamburn plasma (same procedure but water at 37°C) was transferred for negative controls (shamburn group [SBG]). Intravital microscopy was performed at 0, 60, and 120 minutes to assess capillary leakage measuring fluorescein isothiocyanate-albumin extravasation. Macrocirculation was assessed using mean arterial pressure and heart rate, whereas microcirculation was evaluated using red blood cell velocity, venular diameter, venular wall shear rate and plasma extravasation at 0, 60, and 120 minutes in postcapillary venules. RESULTS: Thirty mesenteric venules (16 animals) in SBG and 31 mesenteric venules (15 animals) in BG were observed during intravital microscopy. Mean arterial pressure and heart rate remained within acceptable margins and showed no significant differences, neither within nor between groups. Significant correlations between macrohemodynamic and microhemodynamic conditions were neither observed for BG nor SBG, except from a significant correlation of MAP and plasma extravasation at T60. However, at T120 mesenteric venules in the BG clearly showed microvascular burn edema, whereas venules in SBG did not. CONCLUSIONS: Stabilization of macrohemodynamic conditions may not necessarily have positive effects on microcirculatory derangements-a fact that has not been shown for burns yet, that is-however, well described for sepsis. Further studies are required to show whether distinct monitoring of microcirculation may offer new approaches for burn trauma treatment.

mTORC1 maintains renal tubular homeostasis and is essential in response to ischemic stress.

Mammalian target of rapamycin complex 1 (mTORC1) is a key regulator of cell metabolism and autophagy. Despite widespread clinical use of mTORC1 inhibitors, the role of mTORC1 in renal tubular function and kidney homeostasis remains elusive. By using constitutive and inducible deletion of conditional Raptor alleles in renal tubular epithelial cells, we discovered that mTORC1 deficiency caused a marked concentrating defect, loss of tubular cells, and slowly progressive renal fibrosis. Transcriptional profiling revealed that mTORC1 maintains renal tubular homeostasis by controlling mitochondrial metabolism and biogenesis as well as transcellular transport processes involved in countercurrent multiplication and urine concentration. Although mTORC2 partially compensated for the loss of mTORC1, exposure to ischemia and reperfusion injury exaggerated the tubular damage in mTORC1-deficient mice and caused pronounced apoptosis, diminished proliferation rates, and delayed recovery. These findings identify mTORC1 as an important regulator of tubular energy metabolism and as a crucial component of ischemic stress responses.