10-Year single center experience in lower limb reconstruction with free muscle flaps - factors influencing complications in 266 consecutive cases

The anatomy and technique of free muscle flaps - in particular gracilis flap and latissimus dorsi flap - in lower extremity reconstruction have been well described. There is a paucity of data on potential risk factors in larger patient series that affect the outcome. The objective of this study was to address this lack of knowledge by reporting outcomes and complications of free muscle flaps as a primary option in lower extremity reconstruction. From 2009 to 2020, a total of 253 consecutive patients with soft tissue defects of the lower limb from trauma, infection or malignancies underwent lower extremity reconstructive surgery with 266 free muscle flaps. Complications requiring revision surgery were noted in 36.1% of cases. Total flap loss occurred in 10.5% of cases. Patients requiring revision surgery were older, more likely to be female, more likely to be active smokers, and more likely to have a higher ASA score. Lower extremity reconstruction with free muscle flaps has a relevant complication rate that both patient and reconstructive surgeon need to be aware of. Prospective studies should try to further assess the factors affecting the outcome.

Basic science approaches to common hand surgery problems

The field of hand surgery is constantly evolving to meet challenges of populations with increasing age and higher demands for active living. While our surgical care has improved over the last decades, it seems that future major improvement in outcomes of clinical treatment will come through advances in biologics and the translation of major discoveries in basic science. This article aims to provide an update on where basic science solutions may answer some of the most critical issues in hand surgery, with a focus on augmentation of tissue repair.

Adipose tissue-derived microvascular fragments promote lymphangiogenesis in a murine lymphedema model

Chronic lymphedema after cancer treatment is common and there is still no cure for this disease. We herein investigated the lymphangiogenic capacity of adipose tissue-derived microvascular fragments (MVF), which contain stem cells and lymphatic vessel fragments. Secondary lymphedema was induced in the hindlimbs of C57BL/6J mice. Green fluorescence protein (GFP)+ MVF were isolated from transgenic C57BL/6Tg (CAG-EGFP)1Osb/J mice, suspended in collagen hydrogel, and injected in the lymphadenectomy defect of wild-type animals. This crossover model allowed the detection of MVF-derived blood and lymphatic vessels after transplantation. The MVF group was compared with animals receiving collagen hydrogel only or a sham intervention. Lymphangiogenic effects were analyzed using volumetry, magnetic resonance (MR) lymphography, histology, and immunohistochemistry. MVF injection resulted in reduced hindlimb volumes when compared to non-treated controls. MR lymphography revealed lymphatic regeneration with reduced dermal backflow after MVF treatment. Finally, MVF transplantation promoted popliteal angiogenesis and lymphangiogenesis associated with a significantly increased microvessel and lymphatic vessel density. These findings indicate that MVF transplantation represents a promising approach to induce therapeutic lymphangiogenesis.

[Pain In the Thumb and Other Fingers]

Pain In the Thumb and Other Fingers Abstract. As the population ages, symptoms of osteoarthritis in the hand are seen with increasing frequency. It can lead to substantial pain, physical disability and impair the patient's capacity to work in a population with an increasing retirement age. This article gives an overview about the most prevalent forms of osteoarthritis in the hand, its diagnosis and current treatment options, stressing that the multimodal form of therapy is the most effective.

[Tendinopathies - Common Diagnoses in Hand Surgery]

Tendinopathies - Common Diagnoses in Hand Surgery Abstract. Tendinopathies are among the most frequent reasons for consulting a hand surgeon. The diagnosis can usually be made clinically. A supplementary ultrasound examination helps to visualize the pathology. Most of these diseases respond to non-surgical treatment. If surgical treatment is necessary, it can usually be performed as an outpatient procedure under local anesthesia. This article provides an overview of the most common tendinopathies of the hand and wrist, their diagnosis and treatment.

[The Painful Wrist]

The Painful Wrist Abstract. Wrist pain is a problem that can significantly limit patients in their daily activities. The causes are manifold, and treatment is often challenging. A systematic approach is therefore helpful in working up the correct diagnosis. This article aims to demonstrate a straightforward approach to the evaluation of wrist pain in adults.

[Neuropathic Pain - Differential Diagnosis and Treatment from the Hand Surgeon's Perspective]

Neuropathic Pain - Differential Diagnosis and Treatment from the Hand Surgeon's Perspective Abstract. Neuropathic pain of the wrist and hand can be caused by a multitude of pathologies, such as trauma, iatrogenic damage, local peripheral nerve compression, nerve tumors and systemic diseases. Neuropathic pain can lead to chronification and disability, severely affecting the patients' quality of life and the ability to work. A precise diagnosis is the key to an adequate therapy with satisfactory functional results. An interdisciplinary and multimodal approach is a prerequisite when treating neuropathic pain. This review article provides an insight into the diagnosis and therapy of pathologies associated with neuropathic pain of the wrist and hand.

Intraneural fibrosis and loss of microvascular architecture - Key findings investigating failed human nerve allografts

BACKGROUND

Processed nerve allografts are increasingly used in clinical nerve reconstruction with promising results. However, allograft failure has been reported, leading to chronic pain and persistent loss of function. In the present work, we performed a histological and immunohistochemical analysis of two failed allograft reconstructions of a sensory human nerve one year after primary surgery.

METHODS

Two patients with a superficial radial nerve injury underwent nerve reconstruction with processed nerve allografts. The clinical follow-up was complicated by severe neuropathic pain and absent sensory reinnervation. Consequently, the failed allografts were excised with subsequent histological and immunohistochemical examinations. For that purpose, the collagen content and neurofilament network as well as the blood and lymphatic vasculature were analysed in the center of the specimens.

RESULTS

Histology revealed increased fibrosis, fatty degeneration, and disorganised proliferation of nerve fibres. Moreover, the microvascular network within the allografts was characterised by increased numbers of microvessels, whereas no difference was found concerning the lymphatic vasculature.

CONCLUSION

The herein presented histological and immunohistochemical findings indicate that the failure of human allografts is associated with loss of the physiological microvascular architecture. Future studies elucidating the complex interplay of angiogenesis, lymphangiogenesis and axonal regeneration are required to better understand the mechanisms of human allograft failure.

Fluorescence angiography-assisted debridement of critically perfused glabrous skin in degloving foot injuries: Two case reports

RATIONALE

Degloving foot injuries are challenging to treat and associated with life-long sequelae for patients. An appropriate debridement of ischemic soft tissues with maximal preservation of glabrous skin is key during the reconstruction of these injuries. Indocyanine green (ICG) fluorescence angiography is an established technique for the intraoperative evaluation of tissue perfusion.

PATIENT CONCERNS

Two patients sustained complex foot injuries in traffic accidents, including multiple fracture dislocations and extensive degloving of the plantar skin.

DIAGNOSIS

Clinical inspection revealed significant degloving of the glabrous skin in both patients.

INTERVENTIONS

After fracture fixation, ICG fluorescence angiography-assisted debridement with immediate latissimus dorsi free flap reconstruction was performed.

OUTCOMES

In both cases, this technique allowed a precise debridement with maximal preservation of the glabrous skin. The healing of the remaining glabrous skin was uneventful and the 6-month follow-up was characterized by stable soft tissues and satisfying ambulation.

LESSONS

ICG fluorescence angiography is a safe, user-friendly, and quick procedure with minimal risks, expanding the armamentarium of the reconstructive surgeon. It is highly useful for the debridement of extensive plantar degloving injuries and may also help to minimize the number of procedures and the risk of infection.

Improvement of islet transplantation by the fusion of islet cells with functional blood vessels

Pancreatic islet transplantation still represents a promising therapeutic strategy for curative treatment of type 1 diabetes mellitus. However, a limited number of organ donors and insufficient vascularization with islet engraftment failure restrict the successful transfer of this approach into clinical practice. To overcome these problems, we herein introduce a novel strategy for the generation of prevascularized islet organoids by the fusion of pancreatic islet cells with functional native microvessels. These insulin-secreting organoids exhibit a significantly higher angiogenic activity compared to freshly isolated islets, cultured islets, and non-prevascularized islet organoids. This is caused by paracrine signaling between the β-cells and the microvessels, mediated by insulin binding to its corresponding receptor on endothelial cells. In vivo, the prevascularized islet organoids are rapidly blood-perfused after transplantation by the interconnection of their autochthonous microvasculature with surrounding blood vessels. As a consequence, a lower number of islet grafts are required to restore normoglycemia in diabetic mice. Thus, prevascularized islet organoids may be used to improve the success rates of clinical islet transplantation.

Intramedullary compression screw fixation of metacarpal and phalangeal fractures

The intramedullary headless compression screw (IMCS) technique represents a reliable alternative to percutaneous Kirschner-wire and plate fixation with minimal complications.

Transverse fractures of the metacarpal shaft represent a good indication for this technique. Non-comminuted subcapital and short oblique fractures can also be treated with IMCS.

This technique should not be used in the presence of an open epiphysis, infection and, most of all, in subchondral fractures, because of the lack of purchase for the head of the screw.

A double screw construct is recommended for comminuted subcapital fractures of the metacarpal to avoid metacarpal shortening. IMCS can even be applied for peri-articular fractures of the proximal third of the phalanx and in some multi-fragmentary proximal and middle phalangeal fractures.

Usually the intramedullary screws are not removed. The main indications for screw removal are joint protrusion, infection and screw breakage after new fracture.

Cite this article: EFORT Open Rev 2020;5:624-629. DOI: 10.1302/2058-5241.5.190068

Short-term molecular and cellular effects of ischemia/reperfusion on vascularized lymph node flaps in rats

Vascularized lymph node (VLN) transfer is an emerging strategy to re-establish lymphatic drainage in chronic lymphedema. However, the biological processes underlying lymph node integration remain elusive. This study introduces an experimental approach facilitating the analysis of short-term molecular and cellular effects of ischemia/reperfusion on VLN flaps. Lymph node flaps were dissected pedicled on the lateral thoracic vessels in 44 Lewis rats. VLN flaps were exposed to 45 or 120 minutes ischemia by in situ clamping of the vascular pedicle with subsequent reperfusion for 24 hours. Flaps not exposed to ischemia/reperfusion served as controls. Lymph nodes and the perinodal adipose tissue were separately analyzed by Western blot for the expression of lymphangiogenic and angiogenic growth factors. Moreover, morphology, microvessel density, proliferation, apoptosis and immune cell infiltration of VLN flaps were further assessed by histology and immunohistochemistry. Ischemia for 120 minutes was associated with a markedly reduced cellularity of lymph nodes but not of the perinodal adipose tissue. In line with this, ischemic lymph nodes exhibited a significantly lower microvessel density and an increased expression of VEGF-D and VEGF-A. However, VEGF-C expression was not upregulated. In contrast, analyses of the perinodal adipose tissue revealed a more subtle decrease of microvessel density, while only the expression of VEGF-D was increased. Moreover, after 120 minutes ischemia, lymph nodes but not the perinodal adipose tissue exhibited significantly higher numbers of proliferating and apoptotic cells as well as infiltrated macrophages and neutrophilic granulocytes compared with non-ischemic flaps. Taken together, lymph nodes of VLN flaps are highly susceptible to ischemia/reperfusion injury. In contrast, the perinodal adipose tissue is less prone to ischemia/reperfusion injury.

Intramedullary screw fixation for metacarpal shaft fractures: a biomechanical human cadaver study

Intramedullary cannulated compression screws have been introduced for the fixation of unstable metacarpal fractures. In the present study, this technique was compared with dorsal compression plating to evaluate its biomechanical performance in stabilizing metacarpal shaft fractures. In a first set of experiments, the biomechanical characteristics of the screws were analysed in an artificial bone model. In subsequent experiments, midshaft osteotomies were performed in human cadaver metacarpals, followed by plating or intramedullary screw osteosynthesis. The metacarpals were tested to failure in cantilever bending, following a stepwise increasing cyclic loading protocol. We found a significantly lower load at failure and a significantly lower number of cycles to failure in the intramedullary screw group, but both methods offered sufficient stability under these loads. With reference to published loads on the metacarpals during use of the hand, we conclude that intramedullary osteosynthesis yields sufficient strength and stiffness for early active motion. A difference in its fixation stability is noted compared with plate fixation, which may not be clinically relevant.

Flexor tendon grafts for pulley reconstruction - Morphological aspects

BACKGROUND

Pulleys are crucial to convert flexor tendon excursion into angular motion at the metacarpophalangeal and interphalangeal joints. Loss of pulley function can lead to significant impairment of hand function and may require surgical reconstruction. This reconstruction can be achieved using different flexor tendons grafts, such as the intrasynovial flexor digitorum superficialis (FDS) or the extrasynovial palmaris longus (PL). However, there is limited knowledge on the micromorphology of human pulleys and the suitability of flexor tendon grafts for their reconstruction remains elusive.

METHODS

In the present cadaver study A2 and A4 pulleys were compared with FDS and PL tendons by means of scanning electron microscopy (SEM), histology and immunohistochemistry. Surface morphology, core structure and vascularization of the specimens were analyzed.

RESULTS

SEM imaging of the gliding surfaces revealed morphological differences between tendons and pulleys. Moreover, the core structure of FDS samples was characterized by bundles of individual collagen fibrils whereas PL tendons exhibited a less hierarchical microstructure. In contrast, pulleys consisted of lamellar sheets of densely packed collagen fibrils. Finally, immunohistochemical analyses revealed that the flexor tendons and pulleys contain similar numbers of CD31⁺ microvessels, indicating a comparable tissue vascularization.

CONCLUSION

This study provides novel SEM and immunohistochemical insights into the micromorphology of human pulleys and flexor tendon grafts. Intrasynovial flexor tendons may be particularly suitable for pulley reconstruction and preserving the paratenon may be crucial for graft revascularization.

Finger reconstruction with dorsal metacarpal artery perforator flaps and dorsal finger perforator flaps based on the dorsal branches of the palmar digital arteries - 40 consecutive cases

Since the first description many variations of the dorsal metacarpal reverse island flap have been published but there is still uncertainty about which vascular component should be included for an optimal result. Therefore, it was the aim of this study to analyze vascular reliability and ischemic complications of dorsal metacarpal artery perforator (DMAP) flaps and dorsal finger perforator (DFP) flaps in our patient collective. We performed 40 of these flaps from the dorsum of hand and fingers for finger injuries. The choice of donor site was made according to the defect's location. Patients were analyzed with respect to flap necrosis, ischemic complications and achievement of overall reconstruction goals. In addition, we divided our patients in two groups, one group where we raised the flap from the dorsum of the proximal phalanx and a second one where the flaps were raised from the intermetacarpal space to identify complication rates based on the pedicles location. Of the 40 flaps, 36 survived completely. 4 partial necroses were observed in flaps transferred to more distal defects and in one flap that was used in a wrap-around technique for both dorsal and palmar proximal phalanx. These perforator flaps are a reliable method to cover finger defects and the dorsal metacarpal artery is not necessary for their survival, since the blood supply comes from perforating branches of the palmar vascular system. There is a clear trend for a higher complication rate in flaps raised from the dorsum of the fingers compared to the intermetacarpal space.

Adipose tissue and the vascularization of biomaterials: Stem cells, microvascular fragments and nanofat-a review

Tissue defects in the human body after trauma and injury require precise reconstruction to regain function. Hence, there is a great demand for clinically translatable approaches with materials that are both biocompatible and biodegradable. They should also be able to adequately integrate within the tissue through sufficient vascularization. Adipose tissue is abundant and easily accessible. It is a valuable tissue source in regenerative medicine and tissue engineering, especially with regard to its angiogenic potential. Derivatives of adipose tissue, such as microfat, nanofat, microvascular fragments, stromal vascular fraction and stem cells, are commonly used in research, but also clinically to enhance the vascularization of implants and grafts at defect sites. In plastic surgery, adipose tissue is harvested via liposuction and can be manipulated in three ways (macro-, micro- and nanofat) in the operating room, depending on its ultimate use. Whereas macro- and microfat are used as a filling material for soft tissue injuries, nanofat is an injectable viscous extract that primarily induces tissue remodeling because it is rich in growth factors and stem cells. In contrast to microfat that adds volume to a defect site, nanofat has the potential to be easily combined with scaffold materials due to its liquid and homogenous consistency and is particularly attractive for blood vessel formation. The same is true for microvascular fragments that are easily isolated from adipose tissue through collagenase digestion. In preclinical animal models, it has been convincingly shown that these vascular fragments inosculate with host vessels and subsequently accelerate scaffold perfusion and host tissue integration. Adipose tissue is also an ideal source of stem cells. It yields larger quantities of cells than any other source and is easier to access for both the patient and doctor compared with other sources such as bone marrow. They are often used for tissue regeneration in combination with biomaterials. Adipose-derived stem cells can be applied unmodified or as single cell suspensions. However, certain pretreatments, such as cultivation under hypoxic conditions or three-dimensional spheroids production, may provide substantial benefit with regard to subsequent vascularization in vivo due to induced growth factor production. In this narrative review, derivatives of adipose tissue and the vascularization of biomaterials are addressed in a comprehensive approach, including several sizes of derivatives, such as whole fat flaps for soft tissue engineering, nanofat or stem cells, their secretome and exosomes. Taken together, it can be concluded that adipose tissue and its fractions down to the molecular level promote, enhance and support vascularization of biomaterials. Therefore, there is a high potential of the individual fat component to be used in regenerative medicine.

Differential regulation of macrophage activation by the MIF cytokine superfamily members MIF and MIF-2 in adipose tissue during endotoxemia

Sepsis is a leading cause of death worldwide and recent studies have shown white adipose tissue (WAT) to be an important regulator in septic conditions. In the present study, the role of the inflammatory cytokine macrophage migration inhibitory factor (MIF) and its structural homolog D-dopachrome tautomerase (D-DT/MIF-2) were investigated in WAT in a murine endotoxemia model. Both MIF and MIF-2 levels were increased in the peritoneal fluid of LPS-challenged wild-type mice, yet, in visceral WAT, the proteins were differentially regulated, with elevated MIF but downregulated MIF-2 expression in adipocytes. Mif gene deletion polarized adipose tissue macrophages (ATM) toward an anti-inflammatory phenotype while Mif-2 gene knockout drove ATMs toward a pro-inflammatory phenotype and Mif-deficiency was found to increase fibroblast viability. Additionally, we observed the same differential regulation of these two MIF family proteins in human adipose tissue in septic vs healthy patients. Taken together, these data suggest an inverse relationship between adipocyte MIF and MIF-2 expression during systemic inflammation, with the downregulation of MIF-2 in fat tissue potentially increasing pro-inflammatory macrophage polarization to further drive adipose inflammation.

[Leg ulcers (ulcus cruris): The frequent macrovascular causes]

Leg ulcers (ulcus cruris): The frequent macrovascular causes Abstract. Four pathologies make up the macrovascular etiologies of leg uclers: Venous leg ulcers (50 %), mixed venous-arterial leg ulcers (20 %), arterial leg ulcers (5 %), and Martorell hypertensive ischemic leg ulcer (5 %). The remaining 20 % concern a large array of other etiologies. Every leg ulcer requires vascular (arterial and venous) work-up, that can be completed with microbiology, biopsy, and more in-depth internal diagnostics, as indicated. Venous leg ulcers are treated with compression therapy. Incompetent saphenous veins and tributaries are abolished if the deep venous system is patent. Occluded iliac veins are recanalised and stented, as possible. Refractory venous leg ulcers are grafted with split skin or punch grafts, depending on their surface. Extensive dermatolipofasciosclerosis may be tangentially removed by shave therapy or fasciectomy, that can be combined with negative pressure wound treatment (NPWT). Skin equivalents are an alternative to treat superficial venous leg ulcers that fail to epithelialise. Their indication in the treatment of more complex leg ulcers still needs to be better investigated and understood. The use of dermal matrices leads to more stable scars. Mixed venous-arterial leg ulcers heal slower and recur more frequently. Compression needs to be reduced. Refractory cases require arterial revascularisation, to transform the mixed venous-arterial into a venous leg ulcer. Arterial leg ulcers require arterial revascularization and split skin graft. Martorell hypertensive ischemic leg ulcer is still underrecognised and often confounded with with pyoderma gangrenosum, which leads therapy into a wrong direction. Necrosectomy, antibiotic treatment in the presence of relevant bacterial superinfection, and repeated split skin grafts eventually heal the vast majority of these extremely painful and potentially mortal wounds.

Prevascularization of collagen-glycosaminoglycan scaffolds: stromal vascular fraction versus adipose tissue-derived microvascular fragments

Background

The seeding of scaffolds with the stromal vascular fraction (SVF) of adipose tissue is a common prevascularization strategy in tissue engineering. Alternatively, adipose tissue-derived microvascular fragments (ad-MVF) may serve as vascularization units. In contrast to SVF single cells, they represent a mixture of intact arteriolar, capillary and venular vessel segments. Therefore, we herein hypothesized that the ad-MVF-based prevascularization of scaffolds is superior to the conventional SVF single cells-based approach.

Results

SVF single cells and ad-MVF were enzymatically isolated from epididymal fat pads of green fluorescent protein (GFP)⁺ donor mice to assess their viability and cellular composition using fluorescence microscopy and flow cytometry. Moreover, collagen-glycosaminoglycan matrices (Integra®) were seeded with identical amounts of the isolates and implanted into full-thickness skin defects within dorsal skinfold chambers of GFP⁻ recipient mice for the intravital fluorescent microscopic, histological and immunohistochemical analysis of implant vascularization and incorporation throughout an observation period of 2 weeks. Non-seeded matrices served as controls. While both isolates contained a comparable fraction of endothelial cells, perivascular cells, adipocytes and stem cells, ad-MVF exhibited a significantly higher viability. After in vivo implantation, the vascularization of ad-MVF-seeded scaffolds was improved when compared to SVF-seeded ones, as indicated by a significantly higher functional microvessel density. This was associated with an enhanced cellular infiltration, collagen content and density of CD31⁺/GFP⁺ microvessels particularly in the center of the implants, demonstrating a better incorporation into the surrounding host tissue. In contrast, non-seeded matrices exhibited a poor vascularization, incorporation and epithelialization over time.

Conclusions

The present study demonstrates that ad-MVF are highly potent vascularization units that markedly accelerate and improve scaffold vascularization when compared to the SVF.

Electronic supplementary material

The online version of this article (10.1186/s13036-018-0118-3) contains supplementary material, which is available to authorized users.

Seeding density is a crucial determinant for the in vivo vascularisation capacity of adipose tissue-derived microvascular fragments

Adipose tissue-derived microvascular fragments (ad-MVF) represent effective vascularisation units for the seeding of dermal substitutes. However, particularly in case of extensive skin defects, the required amounts of donor fat tissue for the harvesting of ad-MVF may not always be available. Therefore, we herein determined the lowest ad-MVF density needed to induce a sufficient vascularisation and incorporation of seeded implants. Collagen-glycosaminoglycan matrices (Integra®; diameter: 4 mm) were seeded with 15,000 (HD), 10,000 (MD) and 5,000 (LD) ad-MVF and implanted into full-thickness skin defects within mouse dorsal skinfold chambers, to analyse their in vivo vascularisation and incorporation. Intravital fluorescence microscopy showed a comparable vascularisation of HD and MD ad-MVF-seeded Integra®, which was significantly higher when compared to LD ad-MVF-seeded Integra®. As assessed by photoacoustic imaging, this was associated with an increased oxygenation of the implants. Additional histological and immunohistochemical analyses revealed an enhanced cellular infiltration, collagen content, microvessel density and epithelialisation of HD and MD ad-MVF-seeded Integra®, indicating a better incorporation compared to LD ad-MVF-seeded implants. These findings demonstrate that 80,000 ad-MVF/cm² is the least required density to guarantee an effective vascularisation of the dermal substitute.

Isolation of Murine Adipose Tissue-derived Microvascular Fragments as Vascularization Units for Tissue Engineering

A functional microvascular network is of pivotal importance for the survival and integration of engineered tissue constructs. For this purpose, several angiogenic and prevascularization strategies have been established. However, most cell-based approaches include time-consuming in vitro steps for the formation of a microvascular network. Hence, they are not suitable for intraoperative one-step procedures. Adipose tissue-derived microvascular fragments (ad-MVF) represent promising vascularization units. They can be easily isolated from fat tissue and exhibit a functional microvessel morphology. Moreover, they rapidly reassemble into new microvascular networks after in vivo implantation. In addition, ad-MVF have been shown to induce lymphangiogenesis. Finally, they are a rich source of mesenchymal stem cells, which may further contribute to their high vascularization potential. In previous studies we have demonstrated the remarkable vascularization capacity of ad-MVF in engineered bone and skin substitutes. In the present study, we report on a standardized protocol for the enzymatic isolation of ad-MVF from murine fat tissue.

Potentials and limitations of Integra® flowable wound matrix seeded with adipose tissue-derived microvascular fragments

Adipose tissue-derived microvascular fragments (ad-MVF) represent promising vascularisation units for bioengineered Integra® matrix wound dressing (MWD). However, due to the sheet-like structure with small pore sizes, the seeding of this matrix with ad-MVF is mainly limited to its surface. Integra® flowable wound matrix (FWM) may be suitable to achieve a more homogeneous distribution and, thus, improved vascularisation, because this gel-like matrix allows for the direct admixture of ad-MVF during sample preparation. To test this hypothesis, we seeded MWD and FWM with an identical number of ad-MVF and assessed their distribution and inter-fragment distance within both matrices. Moreover, ad-MVF-seeded MWD and FWM were implanted into full-thickness skin defects within mouse dorsal skinfold chambers to analyse their vascularisation, epithelialisation and tissue incorporation using intravital fluorescence microscopy, histology and immunohistochemistry. Seeded FWM exhibited a more homogeneous ad-MVF distribution, when compared to MWD. This resulted in a significantly increased inter-fragment distance, preventing the reassembly of ad-MVF into new microvascular networks. Accordingly, the vascularisation of FWM was diminished after implantation, as indicated by a reduced functional microvessel density and blood perfusion. This was associated with a decreased tissue incorporation and epithelialisation of the matrix, when compared to ad-MVF-seeded MWD. Hence, the use of FWM as a carrier system may require a tremendous amount of ad-MVF to shorten their inter-fragment distance and, thus, to maintain their vascularisation capacity for tissue engineering applications.

High-resolution 3D volumetry versus conventional measuring techniques for the assessment of experimental lymphedema in the mouse hindlimb

Secondary lymphedema is a common complication of cancer treatment characterized by chronic limb swelling with interstitial inflammation. The rodent hindlimb is a widely used model for the evaluation of novel lymphedema treatments. However, the assessment of limb volume in small animals is challenging. Recently, high-resolution three-dimensional (3D) imaging modalities have been introduced for rodent limb volumetry. In the present study we evaluated the validity of microcomputed tomography (μCT), magnetic resonance imaging (MRI) and ultrasound in comparison to conventional measuring techniques. For this purpose, acute lymphedema was induced in the mouse hindlimb by a modified popliteal lymphadenectomy. The 4-week course of this type of lymphedema was first assessed in 6 animals. In additional 12 animals, limb volumes were analyzed by μCT, 9.4 T MRI and 30 MHz ultrasound as well as by planimetry, circumferential length and paw thickness measurements. Interobserver correlation was high for all modalities, in particular for μCT analysis (r = 0.975, p < 0.001). Importantly, caliper-measured paw thickness correlated well with μCT (r = 0.861), MRI (r = 0.821) and ultrasound (r = 0.800). Because the assessment of paw thickness represents a time- and cost-effective approach, it may be ideally suited for the quantification of rodent hindlimb lymphedema.

Current and emerging vascularization strategies in skin tissue engineering

Vascularization is a key process in skin tissue engineering, determining the biological function of artificial skin implants. Hence, efficient vascularization strategies are a major prerequisite for the safe application of these implants in clinical practice. Current approaches include (i) modification of structural and physicochemical properties of dermal scaffolds, (ii) biological scaffold activation with growth factor-releasing systems or gene vectors, and (iii) generation of prevascularized skin substitutes by seeding scaffolds with vessel-forming cells. These conventional approaches may be further supplemented by emerging strategies, such as transplantation of adipose tissue-derived microvascular fragments, 3D bioprinting and microfluidics, miRNA modulation, cell sheet engineering, and fabrication of photosynthetic scaffolds. The successful translation of these vascularization strategies from bench to bedside may pave the way for a broad clinical implementation of skin tissue engineering.

[Not Available]

Zusammenfassung. Das Extremitätentrauma mit Weichteilschaden ist eine Herausforderung für die behandelnden Chirurgen. Für das Outcome entscheidend ist ein effizienter interdisziplinärer Behandlungsansatz durch Unfallchirurgen/Orthopäden und Plastische Chirurgen, die so früh wie möglich eine gemeinsame Strategie festlegen. Das Ziel dieses orthoplastischen Vorgehens ist die frühe definitive Frakturstabilisation kombiniert mit Weichteildeckung (fix and flap). Die Weichteilrekonstruktion erfolgt heute nach einem modularen Prinzip und nicht mehr linear gemäss der rekonstruktiven Leiter. Die Vielzahl unterschiedlicher Verletzungsmuster bedingt sehr variable Vorgehensweisen in der Rekonstruktion der Weichteildefekte. Dies erschwert eine standardisierte Behandlung und erfordert massgeschneiderte Lösungen, häufig unter Zuhilfenahme mikrochirurgischer Techniken. Eine funktionelle Wiederherstellung verlangt vielfach eine Kombination von Hauttransplantaten, lokoregionalen und freien Lappenplastiken. Die Vakuumtherapie hat sich als nützliches Werkzeug in der Behandlung komplexer Extremitätenverletzungen erwiesen.

Animal models in surgical lymphedema research--a systematic review

BACKGROUND

Chronic secondary lymphedema is a well-known complication in oncologic surgery. Autologous lymph node transplantation, lymphovenous anastomosis, and other lymphatic surgeries have been developed in the last decades with rising clinical application. Animal models to explore the pathophysiology of lymphedema and microsurgical interventions have reached great popularity, although the induction of stable lymphedema in animals is still challenging. The aim of this review was to systematically assess lymphedema animal models and their potential use to study surgical interventions.

MATERIALS AND METHODS

A systematic review according to the PRISMA guidelines was performed without time or language restriction. Studies describing new or partially new models were included in chronological order. Models for primary and secondary lymphedema were assessed, and their potential for surgical procedures was evaluated.

RESULTS

The systematic search yielded 8590 discrete articles. Of 180 articles included on basis of title, 84 were excluded after abstract review. Ninety-six were included in the final analysis with 24 key articles.

CONCLUSIONS

No animal model is perfect, and many models show spontaneous lymphedema resolution. The rodent limb appears to be the most eligible animal model for experimental reconstruction of the lymphatic function as it is well accessible for vascularized tissue transfer. There is a need for standardized parameters in experimental lymphedema quantification. Also, more permanent models to study the effect of free vascularized lymph node transfer are needed.

The hemi-hamate autograft arthroplasty in proximal interphalangeal joint reconstruction: a systematic review

Palmar lip injuries of the proximal interphalangeal joint with dorsal fracture-dislocation are difficult to treat and often require major reconstruction. A systematic review was performed and yielded 177 articles. Thirteen articles on hemi-hamate autograft were included in full-text analysis. Results of 71 cases were summarized. Mean follow-up was 36 months and mean proximal interphalangeal joint range of motion was 77°. Overall complication rate was around 35%. Up to 50% of the patients showed radiographic signs of osteoarthritis. However, few of those patients complained about pain or impaired finger motion. Based on this systematic analysis and review, hemi-hamate autograft can be considered reliable for the reconstruction of acute and chronic proximal interphalangeal joint fracture-dislocations with joint involvement >50%, but longer-term follow-up studies are required to evaluate its outcome, especially regarding the rate of osteoarthritis.

Perforated sigmoid diverticulitis in a lumbar hernia after iliac crest bone graft--a case report

Background

The combination of perforated diverticulitis in a lumbar hernia constitutes an extremely rare condition.

Case presentation

We report a case of a 66 year old Caucasian woman presenting with perforated sigmoid diverticulitis localized in a lumbar hernia following iliac crest bone graft performed 18 years ago. Emergency treatment consisted of laparoscopic peritoneal lavage. Elective sigmoid resection was scheduled four months later. At the same time a laparoscopic hernia repair with a biologic mesh graft was performed.

Conclusion

This case shows a very seldom clinical presentation of lumbar hernia. Secondary colonic resection and concurrent hernia repair with a biologic implant have proven useful in treating this rare condition.