Effects of Venous Superdrainage and Arterial Supercharging on Dorsal Perforator Flap in a Rat Model

Standardized Pre-clinical Surgical Animal Model Protocol to Investigate the Cellular and Molecular Mechanisms of Ischemic Flap Healing

BACKGROUND

Some of the most complex surgical interventions to treat trauma and cancer include the use of locoregional pedicled and free autologous tissue transfer flaps. While the techniques used for these reconstructive surgery procedures have improved over time, flap complications and even failure remain a significant clinical challenge. Animal models are useful in studying the pathophysiology of ischemic flaps, but when repeatability is a primary focus of a study, conventional in-vivo designs, where one randomized subset of animals serves as a treatment group while a second subset serves as a control, are at a disadvantage instigated by greater subject-to-subject variability. Our goal was to provide a step-by-step methodological protocol for creating an alternative standardized, more economical, and transferable pre-clinical animal research model of excisional full-thickness wound healing following a simulated autologous tissue transfer which includes the primary ischemia, reperfusion, and secondary ischemia events with the latter mimicking flap salvage procedure.

RESULTS

Unlike in the most frequently used classical unilateral McFarlane's caudally based dorsal random pattern skin flap model, in the herein described bilateral epigastric fasciocutaneous advancement flap (BEFAF) model, one flap heals under normal and a contralateral flap-under perturbed conditions or both flaps heal under conditions that vary by one within-subjects factor. We discuss the advantages and limitations of the proposed experimental approach and, as a part of model validation, provide the examples of its use in laboratory rat (Rattus norvegicus) axial pattern flap healing studies.

CONCLUSIONS

This technically challenging but feasible reconstructive surgery model eliminates inter-subject variability, while concomitantly minimizing the number of animals needed to achieve adequate statistical power. BEFAFs may be used to investigate the spatiotemporal cellular and molecular responses to complex tissue injury, interventions simulating clinically relevant flap complications (e.g., vascular thrombosis) as well as prophylactic, therapeutic or surgical treatment (e.g., flap delay) strategies in the presence or absence of confounding risk factors (e.g., substance abuse, irradiation, diabetes) or favorable wound-healing promoting activities (e.g., exercise). Detailed visual instructions in BEFAF protocol may serve as an aid for teaching medical or academic researchers basic vascular microsurgery techniques that focus on precision, tremor management and magnification.

Conjoined thoracodorsal perforator-supercharged dorsal intercostal artery perforator propeller flap for reconstruction of a complex upper back defect: Case report and review of the literature on supercharged pedicled perforator flaps

The reported complications' rate of perforator propeller flaps is variably high, but the etiology of distal flap necrosis, potentially linked to vascular insufficiency, is yet to be clarified. Vascular augmentation procedures have been previously described involving an extra anastomosis of a superficial vein, while a perforator-to-perforator supercharging approach has been only sporadically documented in literature. We present a case of perforator-to-perforator vascular supercharging of an extended dorsal intercostal artery perforator (DICAP) propeller flap to provide a salvage option for pedicled flap complicated by venous congestion. A 71-year-old male patient underwent Dermatofibrosarcoma Protuberans resection in the upper back, leading to a 17 × 17 cm defect with bone exposure. A 30 × 9 cm DICAP propeller flap was planned, with the distal third of the flap designed over the adjacent Thoracodorsal artery perforasome, in a conjoined fashion. Considering the small DICAP pedicle caliber and the flap lateral extension, a thoracodorsal artery perforator vein was dissected and included in the distal flap. Once the flap was raised on its main pedicle, the skin paddle turned blue, showing signs of venous insufficiency. Indocyanine green angiography (ICG) showed a viable proximal half of the flap. Hence, after rotating the skin paddle to reach the upper margin of the defect, an additional anastomosis between the perforating thoracodorsal vein and the perforating vein of the dorsal scapular pedicle was performed according to the perforator-to-perforator approach. Doing so, both clinical and ICG examinations showed a well perfused flap, with normal capillary refill. The postoperative course was uneventful, and the patient obtained a good oncological and reconstructive result 4 months postoperatively. The second Vasconez law ("all of the flap will survive except the part that you need") is often encountered in propeller flaps surgery. Our case shows that it is possible to prevent or overcome this problem by planning appropriate vascular augmentation procedures according to the perforator-to-perforator approach, being guided by advanced vascular imaging tools like ICG.

Rat Perforator and Skin Vessels Vascular Mapping: An Original Anatomical Study About 140 Vessels and Literature Review

INTRODUCTION

Recent microsurgical reconstruction techniques benefit from the use of skin and perforator flaps that spare the donor sites. Studies on these skin flaps in rat models are numerous but there is currently no reference regarding the position of the perforators, their caliber, and the length of the vascular pedicles.

METHODS

We performed an anatomical study on 10 Wistar rats and 140 vessels: cranial epigastric (CE), superficial inferior epigastric (SIE), lateral thoracic (LT), posterior thigh (PT), deep iliac circumflex (DCI) and posterior intercostal (PIC) vessels. The evaluation criteria were the external caliber, the length of the pedicle, and the position of the vessels reported on the skin surface.

RESULTS

Data from the six perforator vascular pedicles are reported, with figures illustrating the orthonormal reference frame, the representation of the vessel's position, the cloud of points corresponding to the various measurements, and the average representation of the collected data. The analysis of the literature does not find similar studies; the different vascular pedicles are discussed as well as the limitations of our study: evaluation of cadaver specimen, presence of the very mobile panniculus carnosus, other perforator vessels not evaluated as well as the precise definition of perforating vessels.

CONCLUSIONS

Our work describes the vascular calibers, pedicle lengths, and location of birth and arrival at the skin of the perforator vessels PT, DCI, PIC, LT, SIE, and CE in rat animal models. This work, without an equivalent in the literature, lays the foundation for future studies about flap perfusion, microsurgery, and super microsurgery learning.

Effects of Distal Arterial Supercharging and Distal Venous Superdrainage on the Survival of Multiterritory Perforator Flaps in Rats

BACKGROUND

Which one of the two measures, distal arterial supercharging (DAS) and distal venous superdrainage (DVS), is better to enhance flap survival? No consistent conclusions have been reached.

METHODS

All flaps were pedicled on the deep circumflex iliac vessels. Seventy-two healthy male rats were distributed to four groups randomly: DAVS group (distal arteriovenous supercharging group), the thoracodorsal (TD) artery and TD vein were preserved; DAS group (distal arterial supercharging group), the TD vein was ligated; DVS group (distal venous superdrainage group), the TD artery was ligated; control group, the TD artery and TD vein were ligated. Flap survival rate was evaluated on postoperative day 7. Flap angiography was performed to assess vascular changes of the flap. Microvascular density (MVD) was evaluated by hematoxylin and eosin staining, and CD34-positive microvessel density was measured by immunohistochemistry. Vascular endothelial growth factor (VEGF) level was measured by western blot. The levels of superoxide dismutase (SOD) and malondialdehyde (MDA) were evaluated using specialized commercial kits.

RESULTS

The mean flap survival rate was increased significantly in DAVS and DAS groups than in DVS and control groups. DAVS and DAS groups had higher flap vascularization, MVD, CD34-positive microvessel density, VEGF expression and SOD level compared to DVS and control groups. DAVS and DAS groups also had lower MDA level relative to DVS and control groups.

CONCLUSION

DAS is more conducive to improving the survival rate of the multiterritory perforator flap compared to DVS, mainly by enhancing angiogenesis and preventing ischemia-reperfusion (I/R) injury.

Which one is better for multi-territory perforator flap survival, central perforator artery or central perforator vein?

BACKGROUND

The survival of multi-territory perforator flap is associated with the position of the perforators. This study aimed to explore whether use of the central perforator artery or vein was better for flap survival.

METHODS

75 male Sprague-Dawley rats were randomly divided into three groups (n=25 per group). The flap contained the right and left iliolumbar, left posterior intercostal, and left thoracodorsal angiosomes, termed angiosomes Ⅰ to Ⅳ, respectively. The anastomosis between angiosomes Ⅱ and Ⅲ was termed choke 2. In experimental group 2, only the right iliolumbar vein and the left iliolumbar artery were preserved; in experimental group 1, only the right iliolumbar artery and the left iliolumbar vein were preserved; and in the control group, only the right iliolumbar artery and vein were preserved. On day-7 after the operation, the flap arteriography, intraluminal diameter, average microvascular density, vascular endothelial growth factor (VEGF) expression and flap survival were compared among groups. Moreover, the percentages of the angiosomes were measured.

RESULTS

The dilation of the choke 2 artery was most pronounced in experimental group 2, followed by experimental group 1, and, finally, the control group (p<0.05). Similar results regarding average microvascular density, VEGF expression, and survival rate were found among the three groups. The percentages of angiosomes Ⅰ to Ⅳ were 23.1%, 23.0±3.1%, 23.0±1.9%, and 31.0±3.1%, respectively.

CONCLUSIONS

Compared with the central perforator vein, the central perforator artery was more beneficial in enhancing flap survival. A multi-territory perforator flap with the central perforator artery could capture 3 angiosomes safely.

Perivascular Injections of Botulinum Toxin Type A Versus Low Concentration of Ethanol

BACKGROUND

This study aimed to investigate the effect of low concentration ethanol in increasing flap viability by perioperative perivascular application and compared it with that of botulinum toxin type A (BTX-A).

MATERIALS AND METHODS

Twenty-seven Wistar albino rats weighing 300-350 g were used in this study. The subjects were randomly divided into three equal groups: group E (ethanol, n = 9), group B (BTX-A, n = 9), and group S (saline, n = 9). In rats, the dorsal multi-territory perforator flap was elevated, and the agents were injected. In postoperative 1 wk, flap viability and vascular endothelial growth factor levels were evaluated. Also, blood flow, microvascular density, and inflammation degree of both choke zones were assessed.

RESULTS

The mean flap survival area and vascular endothelial growth factor level were significantly higher in group E than in group B and S (P < 0.001). Similarly, blood flow (first choke zone, P < 0.012, and second choke zone, P < 0.001) and microvascular density (first choke zone and second choke zone, P < 0.001) were found to be higher in Group E compared to Group B and S in the evaluation performed from both choke zones. Also, significant inflammation was detected in the ethanol group.

CONCLUSIONS

The positive effects of BTX-A on flap viability were achieved with a low concentration of ethanol. The fact that a low concentration of ethanol increases blood flow, angiogenesis, and flap viability more than BTX-A in the first postoperative week indicates that it can be an alternative agent for perioperative use.

Effect of Venous Superdrainage on Colon Interposition for Esophageal Reconstruction

When performing esophageal reconstruction, a colonic pedicle graft is chosen as the next candidate to the stomach because of complications arising from the operation time and vascular anastomosis. Vascular anastomosis is not necessarily required for pedicle grafts, but it is necessary to perform additional vascular anastomosis in some cases. We herein report a case of superdrainage in which anastomosis of the colonic vein and the right internal thoracic vein was effective against congestion. A 68-year-old man with thoracic esophageal cancer and pyloric antrum gastric cancer was referred to our hospital. Complete resection was performed with subtotal esophageal resection and total gastrectomy. We added superdrainage (right internal thoracic vein - ileocolic vein) to the colonic pedicle graft, which showed congestion, and performed esophageal reconstruction. Venous superdrainage using a colonic pedicle graft is effective for esophageal reconstruction.

Improvement of multiterritory perforator flap survival supported by a hybrid perfusion mode: A novel strategy and literature review

Perforator flaps have been widely used in clinical Settings, however, unexpected necrosis was still commonly encountered in the distal portions of multiterritory flaps known as Choke zone III. In this study, we introduced a novel hybrid perfusion technique which is different from the established one of arterial supercharging or venous superdrainage to improve multiterritory flap survival with success. In order to ensure the entire flap survival of multiterritory flaps extending to choke zone III, a "hybrid perfusion" mode by anastomosing a distal vein of the flap with a recipient artery was carried out in two cases based on our previous basic study. In addition, a systematic literature review regarding the established microsurgical assistant techniques of arterial supercharging and venous superdrainage techniques were performed. Both flaps survived uneventfully. At a minimal follow-up of six months, both patients were satisfied with the results. This novel hybrid perfusion technique provides a simple new concept in solving partial necrosis of multiterritory flaps. Further practice is guaranteed for better understanding this unconventional attempt.

Effects of oxidative stress and apoptosis on vascularity and viability of perforator flaps

We investigated lateral thoracic and posterior thigh perforator flaps for viability, vascularization, perfusion and apoptosis in a rat model. Wistar albino rats were divided into six groups: lateral thoracic artery perforator flap (LTPF) sham, 3 × 2 cm² LTPF, 3 × 6 cm² LTPF, posterior thigh perforator flap (PTPF) sham, 3 × 2 cm² PTPF, and 3 × 6 cm² PTPF. Flap viability was determined on postoperative days 1 and 7. On day 7, flaps were photographed and their viability was measured using two-dimensional planimeter paper. Tissue samples were harvested for examination by histology and immunohistochemistry. Viability differences were statistically significant. Epithelial thickness, vascularity and number of fibroblasts were reduced in the 3 × 6 cm² groups. Neovascularization and apoptosis based on molecular tests were not significantly different among groups. Flap size and location are important factors for closure of surgical or traumatic defects. We suggest that for clinical application, wound complications will occur less frequently with perforators that nourish large areas of flaps.

Comparison of arterial supercharging and venous superdrainage on improvement of survival of the extended perforator flap in rats

BACKGROUND

Arterial supercharging and venous superdrainage have been the commonly used vascular augmentation techniques for resolving partial loss of flaps in reconstructive surgery. It remains controversial which one of them is more effective in improving flap survival. The purpose of this study was to compare the effect of distal venous superdrainage and arterial supercharging on the survival of an extended dorsal perforator flap in rats.

MATERIALS AND METHODS

Sixty Sprague-Dawley rats were randomly divided into three groups (n = 20 in each group). An extended dorsal perforator flap with the size of 3 × 12 cm based on the deep circumflex iliac artery and vein was elevated in each rat. In arterial supercharging group, the thoracodorsal artery was retained as the distal supercharging vessel; In venous superdrainage group, the thoracodorsal vein was retained as the distal superdrainage vessel. In control group, no other arteries and veins were retained except the main vascular pedicle. On the seventh day after operation, the survival area of flap was calculated as a percentage of viable area to the total flap. Vascular changes in the choke zones were assessed by angiography. Microvascular density and diameter were assessed via immunohistochemistry staining of CD31 on the fifth day after operation.

RESULTS

The flap survival area in arterial supercharging group was significantly higher than that in venous superdrainage group (98.9 ± 0.8% vs. 81.5 ± 3.5%, p < .001). By gross observation, the extent of dilation of choke zone vessels in venous superdrainage group was smaller compared with that in arterial supercharging group. The density of CD31-positive vessels and the diameter of choke zone vessels in arterial supercharging group were significantly larger than that in venous superdrainage group (23.4 ± 4.6 mm^-2 vs. 13.1 ± 4.2 mm^-2 , p < .05; and 37.5 ± 5.8 μm vs. 27.8 ± 4.9 μm, p < .05).

CONCLUSION

Compared with venous superdrainage, distal arterial supercharging in the potential territory resulted in better survival of an extended dorsal perforator flap in a rat model.

Diametric Comparison between the Thoracodorsal Vessel and Deep Inferior Epigastric Vessel in Breast Reconstruction

Background

In microvascular anastomosis, size discrepancy is common and can increase thrombotic complications. If size differences can be predicted, then vessels of the appropriate size can be selected. This study documented the difference in diameter between the thoracodorsal (TD) vessel and deep inferior epigastric perforator (DIEP) pedicle in each patient who underwent breast reconstruction using free tissue transfer. Patients and Methods. This retrospective study included 32 anastomoses (27 breasts including five cases of supercharged anastomosis) of breast reconstruction with the free DIEP flap and TD recipient between August 2018 and June 2019. In the microscopic view, the caliber of the TD vessel, the largest branch to the serratus anterior muscle, the descending branch, the largest and the second largest branches to the latissimus dorsi muscle, and the DIEP pedicle were measured.

Results

The diameter of the deep inferior epigastric artery was similar to that of the descending branch, and their anastomosing rate was 56.3%. The diameter of the deep inferior epigastric vein was similar to the branch to the serratus anterior muscle and the descending branch, and their anastomosing rates were 29.3% and 29.3%, respectively. All flaps were survived; however, in one case, a reoperation was needed to remove the hematoma, in which case fat necrosis occurred as the only complication.

Conclusion

TD branches of similar size to the DIEP pedicle were prioritized in anastomosis. The descending branch and the branch to the serratus anterior muscle are expected to be good candidates as recipients in breast reconstruction with DIEP free flap. Moreover, supercharged anastomosis of DIEP pedicles can be achieved within TD branches.

The effects of optimizing blood inflow in the pedicle on perforator flap survival: A pilot study in a rat model

Background

Perforator flaps have led to a revolution in reconstructive surgery by reducing donor site morbidity. However, many surgeons have witnessed partial flap necrosis. Experimental methods to increase inflow have relied on adding a separate pedicle to the flap. The aim of our study was to experimentally determine whether increasing blood flow in the perforator pedicle itself could benefit flap survival.

Methods

In 30 male Lewis rats, an extended posterior thigh perforator flap was elevated and the pedicle was dissected to its origin from the femoral vessels. The rats were assigned to three groups: control (group I), acute inflow (group II) and arterial preconditioning (group III) depending on the timing of ligation of the femoral artery distal to the site of pedicle emergence. Digital planimetry was performed on postoperative day (POD) 7 and all flaps were monitored using laser Doppler flowmetry perioperatively and postoperatively in three regions (P1-proximal flap, P2-middle of the flap, P3-distal flap).

Results

Digital planimetry showed the highest area of survival in group II (78.12%±8.38%), followed by groups III and I. The laser Doppler results showed statistically significant higher values in group II on POD 7 for P2 and P3. At P3, only group II recorded an increase in the flow on POD 7 in comparison to POD 1.

Conclusions

Optimization of arterial inflow, regardless if performed acutely or as preconditioning, led to increased flap survival in a rat perforator flap model.

Effects of arterial blood supply and venous return on multi-territory perforator flap survival

This study aimed to design arterial ischemic and venous congested areas on the same multi-territory perforator flap, assessing the effects of arterial blood supply and venous return on flap survival. Totally 68 rats were randomly divided into the experimental (Exp) and control (Con) groups. In the Exp group, flaps were based on left superficial epigastric artery and right superficial epigastric vein. In the Con group, flaps were based on the left superficial epigastric artery and vein. Immediate postoperative ink-gelatin angiography, epidermal metabolite levels detection, tissue edema measurement, survival rate evaluation in half of the flaps and average microvessel density assessment were performed. Blood in the Exp group flowed through most angiosomes, but only flowed around pedicled vessels in the Con group; metabolite levels of left halves in the Con and Exp groups were comparable with those of right halves. Angiosomes with high water contents occurred in the Exp group. Survival rates of left halves in the Con and Exp groups were higher than those of right halves, and more microvessels were found in the left ventral areas of both groups compared with the right ventral area in the Exp group. These findings revealed that on the same multi-territory perforator flap, arterial blood supply, affected by venous return, is a prerequisite for flap survival.

Which is the Pivotal Vessel in Vascular Supercharging? An Assessment of Three Forms of Vascular Supercharging Models Using Indocyanine Green Fluorescence Angiography

BACKGROUND

The study aimed to perform continuous and dynamic observation on the blood flow changes in a rat abdominal model of supercharged flaps to examine the roles of arterial and venous supercharging in preventing distal flap necrosis.

MATERIALS AND METHODS

Eighteen rats were divided into three experimental groups. The left-sided flaps in all groups were used as controls such that the subxiphoid perforator vessels served as the only pedicle. Experimental groups I, II, and III consisted of supercharged right-sided flaps. Group I, the arteriovenous supercharging group, had flaps supercharged by the suprapubic perforator arteries and veins. Group II, the arterial supercharging group, had flaps supercharged by the suprapubic perforator arteries. Group III, the venous supercharging group, had flaps supercharged by the suprapubic perforator veins. Laser-induced near-infrared fluorescence angiography was performed before and after surgery.

RESULTS

As revealed by near-infrared fluorescence angiography, the control group and venous supercharging group exhibited rapid reductions in blood supply and loss of arterial perfusion in distal areas. The distal flap necrosis was much smaller in the venous supercharging group than in the control group. Both the arteriovenous supercharging group and the arterial supercharging group exhibited adequate perfusion and resulted in full postoperative survival of the flaps.

CONCLUSIONS

These findings indicated that the distal arterial hypoperfusion is the major cause of the distal venous stasis and necrosis in the flaps. Sufficient arterial supercharging ensures the distal arterial perfusion and therefore diminishes the occurrence of distal flap necrosis.

Material-Induced Venosome-Supported Bone Tubes

The development of alternatives to vascular bone grafts, the current clinical standard for the surgical repair of large segmental bone defects still today represents an unmet medical need. The subcutaneous formation of transplantable bone has been successfully achieved in scaffolds axially perfused by an arteriovenous loop (AVL) and seeded with bone marrow stromal cells or loaded with inductive proteins. Although demonstrating clinical potential, AVL-based approaches involve complex microsurgical techniques and thus are not in widespread use. In this study, 3D-printed microporous bioceramics, loaded with autologous total bone marrow obtained by needle aspiration, are placed around and next to an unoperated femoral vein for 8 weeks to assess the effect of a central flow-through vein on bone formation from marrow in a subcutaneous site. A greater volume of new bone tissue is observed in scaffolds perfused by a central vein compared with the nonperfused negative control. These analyses are confirmed and supplemented by calcified and decalcified histology. This is highly significant as it indicates that transplantable vascularized bone can be grown using dispensable vein and marrow tissue only. This is the first report illustrating the capacity of an intrinsic vascularization by a single vein to support ectopic bone formation from untreated marrow.

Free Bipedicled Radial Forearm and Posterior Interosseous Artery Perforator Flap Phalloplasty

INTRODUCTION

The free radial forearm (FRFA) flap is universally still considered as the gold standard technique in penile reconstruction. Typically, a considerably large flap is required, often involving almost the entire circumference of the forearm. Partial necrosis may occur at the distal-most (dorsoradial) part of the flap as a result of insufficient perfusion.

AIM

To describe a new technique using the posterior interosseous artery (PIOA) to supercharge FRFA phalloplasty.

METHODS

In a 12-month period, all patients having FRFA flap phalloplasty were enrolled. Perioperative, after complete flap dissection, an indocyanine green perfusion scan was performed. In case of insufficient perfusion at the distalmost part of the flap, a supramicrosurgical anastomosis was performed between the FRFA pedicle and the PIOA (artery only).

MAIN OUTCOME MEASURES

Studied outcomes included the rate of marginal necrosis, surgical time, postoperative posterior interosseous nerve damage and urethral complications (fistula, stenosis or necrosis).

RESULTS

A total of 27 FRFA flap phalloplasties was performed. Anastomosis of the PIOA was needed in 15 cases. No marginal necrosis was observed in these cases. There were no cases of postoperative posterior interosseous nerve damage. There were no significant differences in urethral complications (fistula, stenosis or necrosis) between the 2 groups.

CLINICAL IMPLICATIONS

In selected cases where insufficient perfusion of the dorsoradial part of the flap is present, patients may benefit from arterial supercharging to prevent postoperative marginal necrosis.

STRENGTH & LIMITATIONS

Strengths include a single surgeon, thus lending continuity of skill and technique, a consecutive series, and 100% short-term follow-up. Limitations include single institution series and a limited number of patients.

CONCLUSION

Arterial supercharging is effective in improving perfusion of large FRFA flaps used in phalloplasty when dorsoradial hypoperfusion is detected on an indocyanine green perfusion scan. It is a technically challenging addition to the standard technique because of the small size of the vessels, the close relationship between the PIOA and the posterior interosseous nerve, and the vulnerability of the newly constructed intra-flap anastomosis. De Wolf E, Claes K, Sommeling CE, et al. Free Bipedicled Radial Forearm and Posterior Interosseous Artery Perforator Flap Phalloplasty. J Sex Med 2019;16:1111-1117.

ONO-1301 Enhances in vitro Osteoblast Differentiation and in vivo Bone Formation Induced by Bone Morphogenetic Protein

STUDY DESIGN

In vitro and in vivo assessment of osteogenic effect by prostacyclin agonist (ONO-1301).

OBJECTIVE

The aim of this study was to investigate the effects of ONO-1301 on in vitro osteoblastic differentiation and in vivo bone formation induced by bone morphogenetic protein (BMP).

SUMMARY OF BACKGROUND DATA

Among prostaglandins (PGs), PGE2 is the most abundant in bone tissue and its effects on bone formation have been well studied. PGI2 (prostacyclin) is the second most abundant PG in bone tissue and plays important roles in hemodynamics. However, the effects of PGI2 on osteoblast differentiation and bone regeneration have not been elucidated.

METHODS

The effects of PGI2 agonist (ONO-1301), with and without recombinant human (rh) BMP-2, on osteoblastic differentiation and cell proliferation were investigated in vitro using alkaline phosphatase (ALP) and WST-1 assays. Murine primary osteoblasts and cell lines (ST2, MC3T3-E1, C2C12, and CH310T1/2) were used for the study. The effects of ONO-1301 on rhBMP-2 induced bone formation were investigated in a mouse model of muscle pouch transplantation (ectopic model) and in a rat model of spinal fusion (orthotopic model).

RESULTS

ONO-1301 significantly increased ALP activity in the primary osteoblasts and ST2 cells. In addition, cotreatment with ONO-1301 and rhBMP-2 significantly increased ALP activity in the primary osteoblasts, as well as in ST2 and MC3T3-E1 cells. Cell proliferation was not affected by both ONO-1301 and ONO-1301 as well as rhBMP-2. In the ectopic model, ONO-1301 significantly increased the volume of ectopic bone whose formation was induced by BMP. In addition, in the orthotopic model, ONO-1301 significantly increased bone volume and fusion rate.

CONCLUSION

This study has demonstrated that the PG IP agonist ONO-1301 improves in vitro BMP-2 induced osteoblast differentiation and in vivo ectopic and orthotopic bone formation. The results suggest that ONO-1301 has a potential clinical application as an enhancer of BMP-induced bone formation.

LEVEL OF EVIDENCE

N/A.

Dual Vascular Free Anterolateral Thigh Flap

Background:

The optimum number of microvascular anastomoses for safe free tissue transfer is controversial. Although the case for 2 venous anastomoses versus 1 anastomosis has been argued, the use of an additional arterial anastomosis has not been examined in detail.

Methods:

Twelve patients who underwent 2 arterial anastomoses for a free flap transfer were identified retrospectively from the medical records of patients undergoing reconstruction for head and neck cancer. The free flaps were limited to anterolateral thigh (ALT) flaps.

Results:

All flaps survived. Complications included venous thrombosis (n = 1), reexploration (n = 1), and leakage (n = 3). The vascular patterns of dual-arterialized ALT flaps were classified into 3 groups. Types 1 and 2 were ALT flaps that had 2 vascular sources from the descending and lateral branches of the lateral circumflex femoral artery. The number of accompanying veins differed between type 1 (3 veins) and type 2 (2 veins). Type 3 differed from a conventional ALT flap nourished by the descending branch of the lateral circumflex femoral artery (1 vein) by the addition of anastomosis of an artery branching from the descending branch to the vastus medialis muscle. The total operation times for these 3 types of ALT were similar.

Conclusions:

An additional arterial anastomosis to the free cutaneous flap did not cause any congestion or disturb the balance between inflow and outflow. If the surgeon considers that the first arterial anastomosis is unreliable, an additional anastomosis might be an option in ALT transfer.