Improvement of Predictive Scores in Burn Medicine through Different Machine Learning Approaches.

The mortality of severely burned patients can be predicted by multiple scores which have been created over the last decades. As the treatment of burn injuries and intensive care management have improved immensely over the last years, former prediction scores seem to be losing accuracy in predicting survival. Therefore, various modifications of existing scores have been established and innovative scores have been introduced. In this study, we used data from the German Burn Registry and analyzed them regarding patient mortality using different methods of machine learning. We used Classification and Regression Trees (CARTs), random forests, XGBoost, and logistic regression regarding predictive features for patient mortality. Analyzing the data of 1401 patients via machine learning, the factors of full-thickness burns, patient's age, and total burned surface area could be identified as the most important features regarding the prediction of patient mortality following burn trauma. Although the different methods identified similar aspects, application of machine learning shows that more data are necessary for a valid analysis. In the future, the usage of machine learning can contribute to the development of an innovative and precise predictive score in burn medicine and even to further interpretations of relevant data regarding different forms of outcome from the German Burn registry.

Pharmacological elevation of sphingosine-1-phosphate by S1P lyase inhibition accelerates bone regeneration after post-traumatic osteomyelitis.

Posttraumatic osteomyelitis and the ensuing bone defects are a debilitating complication after open fractures with little therapeutic options. We have recently identified potent osteoanabolic effects of sphingosine-1-phosphate (S1P) signalling and have now tested whether it may beneficially affect bone regeneration after infection. We employed pharmacological S1P lyase inhibition by 4-deoxypyrodoxin (DOP) to raise S1P levels in vivo in an unicortical long bone defect model of posttraumatic osteomyelitis in mice. In a translational approach, human bone specimens of clinical osteomyelitis patients were treated in organ culture in vitro with DOP. Bone regeneration was assessed by µCT, histomorphometry, immunohistology and gene expression analysis. The role of S1P receptors was addressed using S1PR3 deficient mice. Here, we present data that DOP treatment markedly enhanced osteogenesis in posttraumatic osteomyelitis. This was accompanied by greatly improved osteoblastogenesis and enhanced angiogenesis in the callus accompanied by osteoclast-mediated bone remodelling. We also identified the target of increased S1P to be the S1PR3 as S1PR3-/- mice showed no improvement of bone regeneration by DOP. In the human bone explants, bone mass significantly increased along with enhanced osteoblastogenesis and angiogenesis. Our data suggest that enhancement of S1P/S1PR3 signalling may be a promising therapeutic target for bone regeneration in posttraumatic osteomyelitis.

Case report: Generalized bullous fixed drug eruption mimicking epidermal necrolysis.

Generalized bullous fixed drug eruption (GBFDE) is the most severe form of fixed drug eruption and can be misdiagnosed as epidermal necrolysis (EN). We report the case of a 42-year-old male patient presenting with more than 50% skin detachment without defined areas of exanthema or erythema and a history of one prior event of EN caused by acetaminophen (paracetamol), allopurinol, or amoxicillin 1.5 years ago. The initial diagnosis was GBFDE or EN. The histology of a skin biopsy was unable to distinguish between the two diseases. The course of the disease, the later clinical presentation, and the medical and medication history, however, were in favor of a diagnosis of GBFDE with two potentially culprit drugs: metamizole and ibuprofen. Moxifloxacin, enoxaparin sodium, hydromorphone, and insulin human were administered concomitantly, which makes them suspicious as well. Unfortunately, the patient received an additional dose of metamizole, one of the possible causative drugs, and he developed another bullous reaction within 1 month. This led to the diagnosis of GBFDE due to metamizole. This report highlights the challenges of distinguishing two rare diseases and elucidates the importance of distinct clinical presentation and detailed medication history.

[Aggressive Fibromatosis: Retrospective Analysis of 110 Patients]. / Die Aggressive Fibromatose. Eine retrospektive Analyse von 110 Patienten.

Aggressive fibromatosis, histologically classified as benign due to the absence of metastasis, is characterised by locally invasive and destructive growth with high recurrence rates after resection. For this reason, prognostic recurrence factors, in particular the extent of resection, are much debated, and treatment decisions seem challenging for interdisciplinary tumour conferences. Between the years 2000 and 2020, 110 patients with aggressive fibromatosis of the extremities or trunk received surgical treatment at BG University Hospital Bergmannsheil (Bochum, Germany). Univariate analyses were performed to detect any potential prognosis factors. The median follow-up time was 5.9 years. A total of 57 (51.8%) of these patients developed recurrence during this period. The 5-year recurrence-free survival was 52.9% (95% CI: 42.4-62.3) in the entire cohort. In R0-resected patients, the 5-year recurrence-free survival (RFS) was significantly better (p<0.001) at 69.2% compared with patients with R1 or R2-resected tumours (32.6%). Beyond that, no other significant influencing factors were identified. The results of this study indicate that R0 resection or R0 resectability were associated with a significantly better local control. The therapeutic recommendation for resection should be made individually by an interdisciplinary tumour board in due consideration of tumour progression, possible therapeutic alternatives, and foreseeable functional impairment.

The Partner Perspective on Autologous and Implant-Based Breast Reconstruction.

INTRODUCTION: Partner involvement in the decision-making process concerning breast reconstruction (BR) after a breast cancer diagnosis may be very supportive for the patient. So far, no study evaluates partner satisfaction with the outcome after BR and the relationship to patient satisfaction. The aim of this study was to assess and compare partner satisfaction of BR with autologous tissue (ABR) and prosthetic implants (IBR), respectively, and compare it to patient-reported outcomes. PATIENTS AND METHODS: All patients undergoing ABR and IBR between January 2014 and December 2020 were asked to participate with their partners. Patient and partner satisfaction with breast reconstruction, overall outcome as well as patient's perceived and self-reported psychosocial well-being were evaluated using the Breast-Q and a modified partner questionnaire, respectively. RESULTS: Fifty-three couples participated (IBR: n=30, ABR: n = 23). Patient and partner satisfaction with breast (r = 0.552), outcome (r = 0.465) as well as patient's perceived and self-report psychosocial well-being (r = 0.495) were highly correlated with partners scoring significantly higher (p<0.001). In terms of partner satisfaction, both reconstructive procedures achieved satisfactory results. ABR scored higher in terms of softness of breast and how natural the breast feels to touch whereas IBR was rated superior evaluating the breast size. CONCLUSION: Both reconstructive procedures achieve satisfactory results in terms partner satisfaction whereas patient's psychosocial well-being was highly overestimated by their partners. Hence, partner inclusion in the regular psycho-oncological support might further sensitize them of the high psychological burden of a breast cancer diagnosis and therefore stabilize patients private support system. LEVEL OF EVIDENCE III: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Digital Media Play a Key Role in Influencing Female Breast Perception.

The female breast is a symbol of femininity and plays a key role in the female body image. However, factors influencing the preferences for different breast shapes and sizes are still not elucidated. In particular, the role of the emerging social media in breast perception has not been analyzed yet. A representative cohort of 1,049 adults completed a web-based questionnaire containing hyperrealistic 3D models of the female breast in the United States. A machine-learning algorithm (Classification and Regression Tree [CART]) was implemented to identify the most influential factors. The study was able to identify the frequency of pornographic and social media consumption as the most influencing factor for altered breast preferences. Although digital media exposure did not alter satisfaction with the own breast among female participants, the tendency to undergo or history of conducted aesthetic surgery correlated with higher access frequency to digital media. Taken together, the overpowering impact of social media and pornographic consumption on the own body image was shown in preference alterations for different anatomical aspects of the breast in the whole population and distorted self-perception about the breast in female participants.

Free-flap reconstruction of the lower limb in octogenarians - A comparative analysis of indications, management, and outcomes.

INTRODUCTION: Impaired microcirculation, along with an increase in chronic medical conditions in the geriatric cohort, may favor the development of soft-tissue defects in the lower extremity and equally impair the options for plastic-reconstructive surgery. In particular, outcome analyses in the increasing patient cohort ≥ 80 years (octogenarians) are limited. METHODS: Setting 80 years as the cutoff, we conducted an age-related outcome analysis of all patients undergoing free-flap reconstruction of the lower extremity from 2014 to 2020, comprising the American Society of Anesthesiologists (ASA) score and Charlson Comorbidity Index (CCI) as the possible outcome predicting factors. RESULTS: During the study period, a total of 424 free flaps were performed in 385 patients (∅: 54.7 years ± 16.1; range: 9-89), including 19 octogenarians. Compared with the younger patient cohort, there was a significantly higher rate of early flap revision (p = 0.023) and flap loss (p = 0.028). Furthermore, the mean length of hospital (60.6 ± 37.6 vs. 51.1 ± 37.0) and intensive care unit/intermediate care stay (6.5 ± 15.0 vs. 3.5 ± 8.5) was extended (n.s.). The ASA score presented an independent predictor for major surgical [odds ratio (OR): 1.66; p = 0.041) and medical complications (OR: 3.97; p<0.001). Neither the CCI nor the ASA served as an independent predictor for total flap loss. CONCLUSION: Free-flap reconstruction of the lower extremity in octogenarians is associated with a higher risk of flap revision and flap loss. Considering the prolonged immobilization associated with increased morbidity following limb amputation, it presents still a reasonable option to achieve limb salvage in carefully chosen patients. An adequate tool to predict the success of free-flap survival is still unavailable.

Inhibition of Pathological Increased Matrix Metalloproteinase (MMP) Activity for Improvement of Bone Regeneration in Diabetes.

Patients with diabetes suffer from poor fracture healing. Molecular reasons are not fully understood and our previous gene expression microarray analyses of regenerating bones from mice with type 2 diabetes (db-/db-) revealed accelerated activation of pathways concerning matrix metalloproteases (MMPs). Thus, we picked out the pathological MMP acceleration as a target for profound gene expression analyses and additional therapeutic intervention in the present study. In the first part, gene expression of ECM degrading proteinases and inhibitors was investigated three and seven days postoperatively. Mmp3, Mmp9, Mmp13 and gene expression of MMP inhibitor Timp2 was significantly higher in regenerating bone fractures of db-/db- compared to wild type animals. Timp1 and metalloproteinase AdamTS4 showed no differences. In the second part, we locally applied a single dose (1 µL of 5 µM solution) of the broad-spectrum molecular MMP inhibitor Marimastat on tibial defects in db-/db-. We performed immunohistochemical and histological stainings seven days post operation. Impaired bone healing, collagen content, angiogenesis, and osteoclast invasion in db-/db- were restored significantly by application of Marimastat compared to PBS controls (n = 7/group). Hence, local intervention of bone defects by the molecular MMP inhibitor Marimastat might be an alternative therapeutic intervention for bone healing in diabetes.

Role of Autonomous Neuropathy in Diabetic Bone Regeneration.

Diabetes mellitus has multiple negative effects on regenerative processes, especially on wound and fracture healing. Despite the well-known negative effects of diabetes on the autonomous nervous system, only little is known about the role in bone regeneration within this context. Subsequently, we investigated diabetic bone regeneration in db-/db- mice with a special emphasis on the sympathetic nervous system of the bone in a monocortical tibia defect model. Moreover, the effect of pharmacological sympathectomy via administration of 6-OHDA was evaluated in C57Bl6 wildtype mice. Diabetic animals as well as wildtype mice received a treatment of BRL37344, a ß3-adrenergic agonist. Bones of animals were examined via µCT, aniline-blue and Masson-Goldner staining for new bone formation, TRAP staining for bone turnover and immunoflourescence staining against tyrosinhydroxylase and stromal cell-derived factor 1 (SDF-1). Sympathectomized wildtype mice showed a significantly decreased bone regeneration, just comparable to db-/db- mice. New bone formation of BRL37344 treated db-/db- and sympathectomized wildtype mice was markedly improved in histology and µCT. Immunoflourescence stainings revealed significantly increased SDF-1 due to BRL37344 treatment in diabetic animals and sympathectomized wildtypes. This study depicts the important role of the sympathetic nervous system for bone regenerative processes using the clinical example of diabetes mellitus type 2. In order to improve and gain further insights into diabetic fracture healing, ß3-agonist BRL37344 proved to be a potent treatment option, restoring impaired diabetic bone regeneration.

The Search for the Ideal Female Breast: A Nationally Representative United-States-Census Study.

INTRODUCTION: Many studies have started to search for the perfect aesthetic breast in order to create a pars-pro-toto for reconstruction, but especially for aesthetic surgery. To date, no representative study with anatomically accurate models was performed. METHODS: In an online based United-States-census-representative survey with 1049 participants, questions regarding the preferred breast were asked utilizing lifelike morphed 3D-generated female models for the first time. Attributes such as breast pole ratio, areola size, breast direction and projection were asked. RESULTS: The results show that, contrary to what has been claimed in previous studies, an upper-pole-to-lower-pole ratio of 55:45 is preferred by both female and male participants. When it comes to breast size, on the other hand, there are clear gender-specific differences. While women opted for a cup size around B, the men preferred larger cup sizes. Moreover, the smallest depicted areola size of 30 mm was favored among all groups in the survey. DISCUSSION: Most publications used rather detrimental models for their surveys. We therefore opted for computer-generated 3D models and varied their naturalness. This enabled us to ensure a more aesthetic and accurate illustration and thus obtained more comparable and reliable results paired with the representation of the US-population. Taken together this study unveiled unexpected insights into the population favored breast attributes that might change operative planning in breast surgery. LEVEL OF EVIDENCE V: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors http://www.springer.com/00266 .

Wnt3a and ASCs are capable of restoring mineralization in staph aureus-infected primary murine osteoblasts.

INTRODUCTION: Bone infections are one of the main reasons for impaired bone regeneration and non-union formation. In previous experimental animal studies we could already demonstrate that bone defects due to prior infections showed a markedly reduced healing capacity, which could effectively be enhanced via application of Wnt3a and Adipose-derived stromal cells (ASCs). For a more in-depth analysis, we investigated proliferation and mineralization of cultured osteoblasts infected with staph aureus and sought to investigate effects of Wnt3a and ASCs on infected osteoblasts. MATERIALS AND METHODS: Primary murine osteoblasts were isolated from calvariae and infected with staph aureus. Infected osteoblasts received treatment via application of recombinant Wnt3a, ASC conditioned medium and were furthermore cocultured with ASCs. Osteoblasts were evaluated by Alamar blue assay for metabolic activity, TUNEL-assay for apoptosis, ALP and Alizarin Red staining for mineralization. In addition, immunoflourescent staining (IF) and qRT-PCR analyses were performed. RESULTS: Infected osteoblasts showed a markedly reduced ability for mineralization and increased apoptosis, which could be restored to physiological levels by Wnt3a and ASC treatment. Interestingly, metabolic activity of osteoblasts seemed to be unaffected by staph aureus infection. Additional analyses of Wnt-pathway activity revealed effective enhancement of canonical Wnt-pathway activity in Wnt3a-treated osteoblasts. CONCLUSIONS: In summary, we gained further osteoblast-related insights into pathomechanisms of reduced bone healing capacity upon infections.

TGF-beta pathway inhibition as the therapeutic acceleration of diabetic bone regeneration.

Bone regeneration and fracture healing are impaired in diabetic patients due to defective functions of associated cells. Thus, the search for molecular causes and new treatment strategies are of particular clinical relevance. We investigated the gene expression profile of bones from type 2 diabetic (db- /db- ) mice and wild-type (wt) mice by comparative microarray analyses before and after placing tibial defects and examined the expression of several osteogenesis- and osteoclastogenesis-related markers by quantitative real-time polymerase chain reaction. In regenerating wt bones, pathways related to, for example, inhibition of matrix metalloproteases were activated, whereas in db- /db- bones activation of pathways related to, for example, osteoarthritis, transforming growth factor-beta (Tgfb), or hypoxia-inducible factor 1a were detected during regeneration. We defined the Tgfb pathway as a potential therapeutic target and locally applied a single dose (0.5 µg) of the Tgfb 1, 2, and 3 neutralizing antibody 1D11 on tibial defects in db- /db- mice (n = 7). Seven days postoperation, histological and immunohistochemical stainings were performed. Decreased bone regeneration, osteogenic differentiation, osteoclast invasion, and angiogenesis in db- /db- mice were significantly restored by local 1D11 application in comparison to the phosphate-buffered saline controls. Thus, local treatment of db- /db- bony defects with Tgfb neutralizing antibody 1D11 might be considered a good candidate for the successful acceleration of bone regeneration.

Posttraumatic Lymphedema after Open Fractures of the Lower Extremity-A Retrospective Cohort Analysis.

Secondary lymphedema is a very common clinical issue with millions of patients suffering from pain, recurrent skin infections, and the constant need for a decongestive therapy. Well-established as a consequence of oncologic procedures, secondary lymphedema is also a well-known phenomenon after trauma. However, precise epidemiological data of lymphedema progress upon severe extremity injuries are still missing. In the present work, we analyzed a patient cohort of 94 individuals who suffered open fractures of the lower extremity and soft tissue injury, of 2nd and 3rd grade according to Tscherne classification, between 2013 and 2019. Typical symptoms of lymphedema have been obtained via interviews and patient medical records in a retrospective cohort analysis. Of all patients, 55% showed symptoms of secondary lymphedema and 14% reported recurrent skin infections, indicating severe lymphedema. Furthermore, comparing patients with and without lymphedema, additional parameters, such as obesity, total number of surgeries, infections, and compartment syndrome, related to lymphedema progress could be identified. According to these data, posttraumatic secondary lymphedema has a highly underestimated clinical prevalence. Further prospective studies are needed to validate this first observation and to identify high-risk groups in order to improve patient's health care.

A Highly Reliable Convolutional Neural Network Based Soft Tissue Sarcoma Metastasis Detection from Chest X-ray Images: A Retrospective Cohort Study.

INTRODUCTION: soft tissue sarcomas are a subset of malignant tumors that are relatively rare and make up 1% of all malignant tumors in adulthood. Due to the rarity of these tumors, there are significant differences in quality in the diagnosis and treatment of these tumors. One paramount aspect is the diagnosis of hematogenous metastases in the lungs. Guidelines recommend routine lung imaging by means of X-rays. With the ever advancing AI-based diagnostic support, there has so far been no implementation for sarcomas. The aim of the study was to utilize AI to obtain analyzes regarding metastasis on lung X-rays in the most possible sensitive and specific manner in sarcoma patients. METHODS: a Python script was created and trained using a set of lung X-rays with sarcoma metastases from a high-volume German-speaking sarcoma center. 26 patients with lung metastasis were included. For all patients chest X-ray with corresponding lung CT scans, and histological biopsies were available. The number of trainable images were expanded to 600. In order to evaluate the biological sensitivity and specificity, the script was tested on lung X-rays with a lung CT as control. RESULTS: in this study we present a new type of convolutional neural network-based system with a precision of 71.2%, specificity of 90.5%, sensitivity of 94%, recall of 94% and accuracy of 91.2%. A good detection of even small findings was determined. DISCUSSION: the created script establishes the option to check lung X-rays for metastases at a safe level, especially given this rare tumor entity.

Myostatin Deficiency Protects C2C12 Cells from Oxidative Stress by Inhibiting Intrinsic Activation of Apoptosis.

Ischemia reperfusion (IR) injury remains an important topic in clinical medicine. While a multitude of prophylactic and therapeutic strategies have been proposed, recent studies have illuminated protective effects of myostatin inhibition. This study aims to elaborate on the intracellular pathways involved in myostatin signaling and to explore key proteins that convey protective effects in IR injury. We used CRISPR/Cas9 gene editing to introduce a myostatin (Mstn) deletion into a C2C12 cell line. In subsequent experiments, we evaluated overall cell death, activation of apoptotic pathways, ROS generation, lipid peroxidation, intracellular signaling via mitogen-activated protein kinases (MAPKs), cell migration, and cell proliferation under hypoxic conditions followed by reoxygenation to simulate an IR situation in vitro (hypoxia reoxygenation). It was found that mitogen-activated protein kinase kinase 3/6, also known as MAPK/ERK Kinase 3/6 (MEK3/6), and subsequent p38 MAPK activation were blunted in C2C12-Mstn-/- cells in response to hypoxia reoxygenation (HR). Similarly, c-Jun N-terminal kinase (JNK) activation was negated. We also found the intrinsic activation of apoptosis to be more important in comparison with the extrinsic activation. Additionally, intercepting myostatin signaling mitigated apoptosis activation. Ultimately, this research validated protective effects of myostatin inhibition in HR and identified potential mediators worth further investigation. Intercepting myostatin signaling did not inhibit ROS generation overall but mitigated cellular injury. In particular, intrinsic activation of apoptosis origination from mitochondria was alleviated. This was presumably mediated by decreased activation of p38 caused by the diminished kinase activity increase of MEK3/6. Overall, this work provides important insights into HR signaling in C2C12-Mstn-/- cells and could serve as basis for further research.

Deficiency of myostatin protects skeletal muscle cells from ischemia reperfusion injury.

Ischemia reperfusion (IR) injury plays a pivotal role in many diseases and leads to collateral damage during surgical interventions. While most studies focus on alleviating its severity in the context of brain, liver, kidney, and cardiac tissue, research as regards to skeletal muscle has not been conducted to the same extent. In the past, myostatin (MSTN), primarily known for supressing muscle growth, has been implicated in inflammatory circuits, and research provided promising results for cardiac IR injury mitigation by inhibiting MSTN cell surface receptor ACVR2B. This generated the question if interrupting MSTN signaling could temper IR injury in skeletal muscle. Examining human specimens from free myocutaneous flap transfer demonstrated increased MSTN signaling and tissue damage in terms of apoptotic activity, cell death, tissue edema, and lipid peroxidation. In subsequent in vivo MstnLn/Ln IR injury models, we identified potential mechanisms linking MSTN deficiency to protective effects, among others, inhibition of p38 MAPK signaling and SERCA2a modulation. Furthermore, transcriptional profiling revealed a putative involvement of NK cells. Collectively, this work establishes a protective role of MSTN deficiency in skeletal muscle IR injury.

TNF-α modulation via Etanercept restores bone regeneration of atrophic non-unions.

Treatment of atrophic non-unions, especially in long bones is a challenging problem in orthopedic surgery due to the high revision and failure rate after surgical intervention. Subsequently, there is a certain need for a supportive treatment option besides surgical treatment. In our previous study we gained first insights into the dynamic processes of atrophic non-union formation and observed a prolonged inflammatory reaction with upregulated TNF-α levels and bone resorption. In this study we aimed to improve bone regeneration of atrophic non-unions via TNF-α modulation in a previously established murine femoral segmental defect model. Animals that developed atrophic non-unions of the femur after 5 and 10 weeks were treated systemically for 10 and 5 weeks with Etanercept, a soluble TNF-α antibody. µCT scans and histology revealed bony bridging of the fracture gap in the treatment group, while bone formation in control animals without treatment was not evident. Moreover, osteoclasts were markedly decreased via modulation of the RANKL/OPG axis due to Etanercept treatment. Additionally, immunomodulatory effects via Etanercept could be observed as further inflammatory agents, such as TGF-ß, IL6, MMP9 and 13 were decreased in both treatment groups. This study is the first showing beneficial effects of Etanercept treatment on bone regeneration of atrophic non-union formation. Moreover, the results of this study provide a new and promising therapeutic option which might reduce the failure rate of revision surgeries of atrophic non-unions.

Local Wnt3a treatment restores bone regeneration in large osseous defects after surgical debridement of osteomyelitis.

Impaired bone homeostasis caused by osteomyelitis provokes serious variations in the bone remodeling process, thereby involving multiple inflammatory cytokines to activate bone healing. We have previously established a mouse model for post-traumatic osteomyelitis and studied bone regeneration after sufficient debridement. Moreover, we could further characterize the postinfectious inflammatory state of bony defects after debridement with elevated osteoclasts and decreased bone formation despite the absence of bacteria. In this study, we investigated the positive effects of Wnt-pathway modulation on bone regeneration in our previous established mouse model. This was achieved by local application of Wnt3a, a recombinant activator of the canonical Wnt-pathway. Application of Wnt3a could enhance new bone formation, which was verified by histological and µ-CT analysis. Moreover, histology and western blots revealed enhanced osteoblastogenesis and downregulated osteoclasts in a RANKL-dependent manner. Further analysis of Wnt-pathway showed downregulation after bone infections were reconstituted by application of Wnt3a. Interestingly, Wnt-inhibitory proteins Dickkopf 1 (DKK1), sclerostin, and secreted frizzled protein 1 (sFRP1) were upregulated simultaneously to Wnt-pathway activation, indicating a negative feedback for active form of Beta-catenin. In this study, we could demonstrate enhanced bone formation in defects caused by post-traumatic osteomyelitis after Wnt3a application. KEY MESSAGES: Osteomyelitis decreases bone regeneration Wnt3a restores bone healing after infection Canonical Wnt-pathway activation with negative feedback.

Inflammatory processes and elevated osteoclast activity chaperon atrophic non-union establishment in a murine model.

BACKGROUND: Delayed bone healing, especially in long bones poses one of the biggest problems in orthopeadic and reconstructive surgery and causes tremendous costs every year. There is a need for exploring the causes in order to find an adequate therapy. Earlier investigations of human scaphoid non-union revealed an elevated osteoclast activity, accompanied by upregulated levels of TGF-beta and RANKL. Interestingly, scaphoid non-union seemed to be well vascularized. METHODS: In the current study, we used a murine femur-defect model to study atrophic non unions over a time-course of 10 weeks. Different time points were chosen, to gather insights into the dynamic processes of non-union establishment. RESULTS: Histological analyses as well as western blots and qRT-PCR indicated enhanced osteoclast activity throughout the observation period, paralleled by elevated levels of TGF-beta, TNF-alpha, MMP9, MMP13 and RANKL, especially during the early phases of non-union establishment. Interestingly, elevated levels of these mediators decreased markedly over a period of 10 weeks, as inflammatory reaction during non-union establishment seemed to wear out. To our surprise, osteoblastogenesis seemed to be unaffected during early stages of non-union establishment. CONCLUSION: Taken together, we gained first insights into the establishment process of atrophic non unions, in which inflammatory processes accompanied by highly elevated osteoclast activity seem to play a leading role.