Pedicled Transplantation of Axially Vascularized Bone Constructs in a Critical Size Femoral Defect.

INTRODUCTION: Axial vascularization represents a mandatory requirement for clinically applied larger scale vascularized bone grafts. The aim of this study was to combine the arteriovenous (AV) loop model in the rat with a critically sized femoral bone defect and to successfully transplant axially vascularized bone constructs into the defect. MATERIALS AND METHODS: In Groups A and C, an AV loop together with a clinically approved hydroxyapatite and beta-tricalcium phosphate (HA/ß-TCP) matrix, mesenchymal stem cells, and recombinant human bone morphogenetic protein 2 were implanted into a newly designed porous titanium chamber with an integrated osteosynthesis plate in the thighs of rats, whereas in Groups B and D, the same matrix composition without AV loop and, in Group E, only the HA/ß-TCP matrix were implanted. After 6 weeks, the constructs were transplanted into a 10 mm femoral defect created in the same leg, in Groups A and C, under preservation of the AV loop pedicle. Group F served as a control group with an empty chamber. Ten days (Groups A and B) and 12 weeks (Groups C-F) after transplantation, the femora together with the constructs were explanted and investigated using computed tomography (CT), micro-CT, X-ray, histology, and real-time polymerase chain reaction (RT-PCR). RESULTS: Ten days after transplantation, Group A showed a maintained vascular supply leading to increased vascularization, cell survival in the scaffold center, and bone generation compared to Group B. After 12 weeks, there was no difference detectable among all groups regarding total vessel number, although Group C, using the AV loop, still showed increased vascularization of the construct center compared to Groups D and E. In Group C, there was still enhanced bone generation detectable compared to the other groups and increased bony fusion rate at the proximal femoral stump. CONCLUSIONS: This study shows the combination of the AV loop model in the rat with a critically sized femoral defect. By maintenance of the vascular supply, the constructs initially showed increased vascularization, leading to increased bone formation and bony fusion in the long term.

Treatment of standardised wounds with pure epidermal micrografts generated with an automated device.

In this study, we analysed the effects of pure epidermal micrografts generated with an automated device in a standardised human wound model. Epidermal micrografts were harvested using an automated device. Micrografts were then transplanted onto split-skin donor sites. The target area was only partially covered with transplants to create an intra-individual control area. Wounds were evaluated by subjective assessment as well as measurements with combined laser and white light spectroscopy and cutometry. The epidermal graft sites remained completely stable, whereas control sites offered partially unstable and blistering areas. Statistically, no measurable difference in the speed of initial reepithelialisation could be shown. However, there was an increased pliability and softness of the treated areas that correlated with the subjective impression of both investigators and patients. There was a significantly higher relative haemoglobin concentration, measurable in treated and untreated areas at 4 weeks and 6 months. Cutometry showed no differences in skin properties between treated and untreated areas. This study shows an effect of epidermal micrografts in a standardised human wound model and supports the positive impact of keratinocytes on early wound healing as described in literature. Long-term effects of epidermal grafting deserve further studies.

Reconstruction of Extensive Volar Finger Defects with Double Cross-Finger Flaps.

Cross-finger flaps still represent a viable option to reconstruct small- to medium-sized full-thickness finger defects but they are not commonly used if larger areas have to be covered. We present 2 cases showing a simple and pragmatic approach with homodigital double cross-finger flaps to reconstruct extensive volar finger soft-tissue defects. We observed very low donor-site morbidity and excellent functional and aesthetic outcomes. Furthermore, there is no need for microsurgical techniques or equipment when using this method. Although this case report only addresses volar defects, one might also think of applying this concept to dorsal defects using reversed double cross-finger flaps.

Intraoperative flap design using ICG monitoring of a conjoined fabricated anterolateral thigh/tensor fasciae latae perforator flap in a case of extensive soft tissue reconstruction at the lower extremity.

In this report, we present a case of the use of a conjoined fabricated free anterolateral thigh (ALT)/tensor fascia latae (TFL) perforator flap for reconstruction of the lower extremity with intraoperative flap design using intraoperative indocyanine green (ICG) monitoring. The flap was used for reconstruction of a 16 cm × 28 cm sized defect of the lower leg in a 24-year-old man. The defect was caused by a third degree open fracture to the tibia. Upon dissection of the ALT perforators, ICG monitoring showed that both dominant ALT perforators did not yield a sufficient perforasome (∼16 cm × 17 cm) for the larger flap needed. An adjacent TFL perforator also supplied a large perforasome (∼15 cm × 11 cm), so a conjoined fabricated flap was harvested and transplanted to cover an extensive lower leg defect. The artery of the TFL perforator pedicle was being in-flap anastomosed to a side branch of the ALT pedicle. Postoperative course was uneventful and there were no complications. Length of follow-up was 6 months, aesthetic and functional outcome was good. The patient was very satisfied with the aesthetic outcome. Both legs were fully mobile after intensive physiotherapy for the reconstructed leg. The leg where the flap had been harvested showed full strength in knee joint flexion. This case could show that identification of the supplying vessels may be possible by ICG monitoring. © 2015 Wiley Periodicals, Inc. Microsurgery 36:684-688, 2016.

Combination of BMP2 and MSCs significantly increases bone formation in the rat arterio-venous loop model.

INTRODUCTION: In this study the induction of bone formation in an axially vascularized bone matrix using mesenchymal stem cells (MSCs) and application of bone morphogenetic protein 2 (BMP2) was analyzed in the arteriovenous loop (AVL) model. MATERIALS AND METHODS: An AVL was created in the medial thigh of 42 rats and placed in a porous titanium chamber filled with a particulated porous hydroxyapatite and beta-tricalcium phosphate matrix and fibrin. In group A the fibrin was loaded with 5×10(6) DiI-stained fibrin gel-immobilized primary MSCs from syngenic Lewis rats, in group B the matrix was loaded with 60 µg/mL BMP2 and in group C both, BMP2 and MSCs were applied at implantation time point. After 6 and 12 weeks, specimens were investigated by means of histological, morphometrical, and micro-computed tomography analysis. RESULTS: After implantation of an AVL a dense vascular network was visible in all groups. In group A, newly generated bone islands were detected in the periphery of the main vascular axis. Using BMP2 alone (group B), small islands of newly formed bone were visible evenly distributed in all parts of the constructs. In group C nearly the whole matrix was interspersed with bone formations. In all groups there was an increase of bone formation between the 6 and 12 weeks explantation time points. CONCLUSIONS: This study demonstrates for the first time the successful generation of axially vascularized bone substitutes using MSCs and BMP2 in the AVL rat model using a one step procedure. Using the combination of BMP2 and MSCs there was a significant increase of bone formations detectable compared to the BMP2 or MSCs alone groups.

Evaluation of angiogenesis of bioactive glass in the arteriovenous loop model.

In this study, the angiogenetic effect of sintered 45S5 Bioglass® was quantitatively assessed for the first time in the arteriovenous loop (AVL) model. An AVL was created by interposition of a venous graft from the contralateral side between the femoral artery and vein in the medial thigh of eight rats. The loop was placed in a Teflon isolation chamber and was embedded in a sintered 45S5 Bioglass® granula matrix filled with fibrin gel. Specimens were investigated 3 weeks postoperatively by means of microcomputed tomography, histological, and morphometrical techniques. All animals tolerated the operations well. At 3 weeks, both microcomputed tomography and histology demonstrated a dense network of newly formed vessels originating from the AVL. All constructs were filled with cell-rich, highly vascularized connective tissue around the vascular axis. Analysis of vessel diameter revealed constant small vessel diameters, indicating immature new vessel sprouts. This study shows for the first time axial vascularization of a sintered 45S5 Bioglass® granula matrix. After 3 weeks, the newly generated vascular network already interfused most parts of the scaffolds and showed signs of immaturity. The intrinsic type of vascularization allows transplantation of the entire construct using the AVL pedicle.