Free Flap Model Research Articles

Mandibular reconstruction system reliability analysis using probabilistic finite element method

The aim of this study was to design for mandibular reconstruction of large lateral defect with minimum target reliability with designated confidence interval under bite force range of 300 ± 102 N. The performance of the models has been evaluated by numerical analysis considering the uncertainty of input parameters. Computer-Aided design was used to develop the models of three designs according to the patient's anatomy and to achieve to near symmetry of the mandible. Stress-strength modeling was utilized for the probabilistic physics of failure analysis under assumption of a quasi-static load. Monte-Carlo simulation was also applied for probabilistic finite element analysis and reliability assessment. The sensitivity analysis of the models was developed to reflect the significance of the variables in the models. The deterministic stress analysis shows that the highest stress and the second maximum stress are 110 MPa and 85 MPa for cortical bone around the screws, respectively. Also, it is determined that the maximum plate stress of the titanium conventional plate model is 580 MPa. The reconstruction system success rate was improved in all models by observing the anatomy of the patient's mandible in the plate designs by computer-aided design and additive manufacturing techniques. Based on the results, the reliability of plate strength and pull-out screws strength are 99.99% and 96.71% for the fibula free flap model, respectively, and 99.99% and 94.17%, respectively, for the customized prosthesis model. Probability sensitivity factors showed that uncertainty in the elastic modulus of the cortical bone has the greatest effect on the probability of screws loosening.

Effect of Simvastatin Use in Free Tissue Transfer: An Experimental Study in a Rat Epigastric Free Flap Model.

Statins are traditionally used in lowering cholesterol and low-density lipoprotein biosynthesis, but recent reports show their beneficial effect on microcirculation. The aim of this study was to investigate the effect of simvastatin on the microcirculation and in conjunction with aspirin in a rat free epigastric flap model. Thirty-six Sprague-Dawley rats were divided into group A (control, n = 12), group B (simvastatin treated, n = 12), and group C (simvastatin and aspirin, n = 12). Bilateral free epigastric skin flap was used to evaluate the effect. At 48 hours, flaps biopsies were evaluated for inflammatory activity, nitric oxide content, and thrombomodulin regulation in the endothelial lining of microvessels. Flap survival was evaluated on day 7. The diameter of microvessels and nitric oxide activity in groups B and C were significantly higher than in group A (p < 0.005 and 0.015, respectively). The perivascular inflammatory cell infiltrates and intravascular adhesions were predominant in group A compared with groups B and C (p < 0.005). Groups B and C demonstrated significant higher degree of thrombomodulin expression. The flap survival rate on day 7 was 70.8% for group A, and 87.5% and 91.7%, respectively, for groups B and C without significance between the two (p = 0.675). Simvastatin significantly improves the free flap survival by effective anti-inflammatory, vasodilator, and anticoagulant activities. Combined therapy did not have an antagonistic effect and further study is needed to see synergistic action through different mechanisms.

A Pre-clinical Rat Model for the Study of Ischemia-reperfusion Injury in Reconstructive Microsurgery.

Ischemia-reperfusion injury is the main cause of flap failure in reconstructive microsurgery. The rat is the preferred preclinical animal model in many areas of biomedical research due to its cost-effectiveness and its translation to humans. This protocol describes a method to create a preclinical free skin flap model in rats with ischemia-reperfusion injury. The described 3 cm x 6 cm rat free skin flap model is easily obtained after the placement of several vascular ligatures and the section of the vascular pedicle. Then, 8 h after the ischemic insult and completion of the microsurgical anastomosis, the free skin flap develops the tissue damage. These ischemia-reperfusion injury-related damages can be studied in this model, making it a suitable model for evaluating therapeutic agents to address this pathophysiological process. Furthermore, two main monitoring techniques are described in the protocol for the assessment of this animal model: transit-time ultrasound technology and laser speckle contrast analysis.

Effects of autologous platelet-rich plasma in the repair of soft tissue defects of rabbits with free flap

Objective: To explore the effects of autologous platelet-rich plasma (PRP) in the repair of soft tissue defects of rabbits with free flap. Methods: Thirty 6-month-old New Zealand white rabbits, male and female unlimited, were used to harvest blood from the heart. PRP was prepared by Aghaloo method, then free flap model with size of 5 cm×3 cm was reproduced on each ear of the rabbit. According to the random number table, one ear of each rabbit was recruited to PRP group, and the other ear was recruited to normal saline group. The base of flap on rabbit ear in PRP group was evenly spread with 1.0 mL autologous PRP, and equivalent volume of normal saline was applied to that in normal saline group. Then, the flap was replanted in situ. On post surgery day (PSD) 2, 3, 5, 7, and 14, 6 rabbits in each group were taken. The survival of flap was observed and recorded. The morphology of the basal tissue of flap was observed by hematoxylin-eosin staining. The expressions of CD31 and α smooth muscle actin (α-SMA) in the basal tissue of flap were detected by immunofluorescence method. Another 6-month-old male New Zealand white rabbit without making flap under the same experimental conditions was used for harvesting whole blood and preparing PRP. Then blood platelet count in whole blood and PRP was determined, and the content of vascular endothelial growth factor (VEGF) and transforming growth factor β (TGF-β) was detected by double-antibody sandwich enzyme-linked immunosorbent assay. Data were processed with analysis of variance of factorial design, paired sample t test, and Bonferroni correction. Results: (1) On PSD 2, the flaps of wounds of rabbits in PRP group were reddish and adhered well to the basal tissue; the flaps of wounds of rabbits in normal saline group were dark red and poorly attached to the basal tissue. On PSD 3, the flaps of wounds of rabbits in PRP group were ruddy and closely adhered to the basal tissue; the flaps of wounds of rabbits in normal saline group were scattered in the plaque-like dark red and generally attached to the base. On PSD 5, the flaps of wounds of rabbits in PRP group were reddish and closely adhered to the basal tissue, and the flaps were alive; while flaps of wounds of rabbits in normal saline group were rosy and closely adhered to the basal tissue. On PSD 7, the surface of flaps of wounds of rabbits in PRP group was covered with a medium amount of rabbit hair. The color of flap was similar to that of the surrounding skin. The flaps of wounds of rabbits in normal saline group were generally attached to the base, and the surface was only covered with a small amount of fluff. On PSD 14, the incisions were healed well in PRP group, while small wounds in normal saline group were not healed. (2) On PSD 2, inflammatory cell infiltration was observed in flaps of wounds of rabbits in both groups. On PSD 3, the flaps of wounds of rabbits in PRP group showed neovascularization, with less interstitial hemorrhage; while there were less neovascularization in the flaps of wounds of rabbits in normal saline group. On PSD 5, a medium number of inflammatory cell infiltration and a small amount of new microvessels were observed in flaps of wounds of rabbits in normal saline group. Many fibroblasts, a small amount of inflammatory cells, and scattered new microvessels were observed in flaps of wounds of rabbits in PRP group. On PSD 7, the number of new microvessels in normal saline group was significantly lower than that in PRP group. On PSD 14, the new microvessels in the flaps of wounds of rabbits in PRP group gradually matured, and a large number of fibroblasts distributed around them. Some of the newly formed microvessels in the flaps of wounds of rabbits in normal saline group were mature, and the healing was slower than that of PRP group. (3) On PSD 2, 3, 5, 7, and 14, the expressions of CD31 and α-SMA in the basal tissue of flaps of wounds of rabbits in PRP group were significantly higher than those in normal saline group (t=10.133, 5.444, 9.450, 6.986, 8.394, 14.896, 10.328, 9.295, 13.902, 10.814, P<0.01). (4) The platelet count in activated PRP of rabbits was (2 863±962)×10(9)/L, which was significantly higher than (393±49)×10(9)/L in whole blood (t=7.690, P<0.05). (5) The content of VEGF and TGF-β in activated PRP of rabbits was (564.3±3.2) and (1 143±251) pg/mL, which was significantly higher than (99.7±0.4) and (274±95) pg/mL in whole blood, respectively (t=287.390, 9.648, P<0.05 or P<0.01). Conclusions: PRP of rabbits contains high concentrations of VEGF and TGF-β. Therefore, PRP can effectively promote microvascular regeneration in free flap tissue and accelerate the survival of free flap.

Ischemia-reperfusion injury in a rat microvascular skin free flap model: A histological, genetic, and blood flow study.

Ischemia reperfusion injury is associated with tissue damage and inflammation, and is one of the main factors causing flap failure in reconstructive microsurgery. Although ischemia-reperfusion (I/R) injury is a well-studied aspect of flap survival, its biological mechanisms remain to be elucidated. To better understand the biological processes of ischemia reperfusion injury, and to develop further therapeutic strategies, the main objective of this study was to identify the gene expression pattern and histological changes in an I/R injury animal model. Fourteen rats (n = 7/group) were randomly divided into control or ischemia-reperfusion group (8 hours of ischemia). Microsurgical anastomoses were objectively assessed using transit-time-ultrasound technology. Seven days after surgery, flap survival was evaluated and tissue samples were harvested for anatomopathological and gene-expression analyses.The I/R injury reduced the survival of free flaps and histological analyses revealed a subcutaneous edema together with an inflammatory infiltrate. Interestingly, the Arginase 1 expression level as well as the ratio of Arginase 1/Nitric oxide synthase 2 showed a significant increase in the I/R group. In summary, here we describe a well-characterized I/R animal model that may serve to evaluate therapeutic agents under reproducible and controlled conditions. Moreover, this model could be especially useful for the evaluation of arginase inhibitors and different compounds of potential interest in reconstructive microsurgery.

Tissue-engineered submillimeter-diameter vascular grafts for free flap survival in rat model

Vascular grafts for free flap transfers should be of very small diameter and remain patent for approximately three weeks to supply blood until the revascularization from the surrounding tissue is established, with the autologous vein grafts acting as the gold standard. Artificial submillimeter-diameter vascular grafts with clinically useful size of 0.6 mm inner diameter and 5 cm length were prepared and evaluated by replacing the axial artery of free flap in rats. The rat tail artery, selected as a novel bioscaffold material, was decellularized using ultrahigh-hydrostatic pressure (UHP) method and compared with the detergent-based conventional method. To induce rapid endothelialization, the graft lumen was modified with synthesized peptides, having high affinity to the endothelial progenitor cells. The UHP method and peptide modification at 37 °C were found to preserve the extracellular matrix structure well, leading to the stable immobilization of the peptide at the luminal surface. These grafts showed the neointima formation, even at the center position far from the native vessels, remained patent for three weeks, and resulted in the flap survival in the rat free-flap model. The tissue-engineered vascular grafts with functionalized lumen have great future potential as an alternative to autologous vein grafts in free flap transfers.

Adipose-Derived Stem Cells Ameliorate Ischemia-Reperfusion Injury in a Rat Skin Free Flap Model.

Ischemia-reperfusion (I/R) injury is inevitable during free tissue transfers. When the period of ischemia exceeds the tissue tolerance, it causes necrosis and flap failure. The aim of this study was to investigate the effects of adipose-derived stem cells (ASCs) embedded in a collagen type I scaffold on the survival of free skin flaps to counteract I/R injury. Left superficial caudal epigastric skin flaps (3 × 6 cm) were performed in 28 Wistar rats that were divided into four groups. The flaps elevated in the animals of the control group did not suffer any ischemic insult, and the vascular pedicle was not cut. All other flaps were subjected to 8 hours of ischemia prior to revascularization: I/R control group (8 hours of ischemia), I/R scaffold group (8 hours of ischemia + collagen type I scaffold), and I/R scaffold-ASCs group (8 hours of ischemia + collagen type I scaffold with rat ASCs embedded). Transit-time ultrasound blood flow measurements were performed. After 7 days, the areas of flap survival were measured and tissues were stained with hematoxylin/eosin and Masson's trichrome stain for histological analysis. The mean percentage flap survival area was significantly higher in the ASCs-treated flaps (I/R scaffold-ASCs group) compared with the ischemic controls (I/R control group and I/R scaffold group). Higher vascular proliferation and lower severity of necrosis and inflammatory changes were seen histologically in the samples of the ASCs-treated group. No significant difference in blood flow was detected between groups. Subcutaneous administration of ASCs embedded on a collagen type I scaffold reduces tissue damage after I/R injury in microvascular free flaps.

Detection of free flap pedicle thrombosis by infrared surface temperature imaging

BackgroundReliable detection of any circulatory issue threatening flap viability after free flap surgery is essential for prompt flap salvage. Currently, the gold standard of flap monitoring is clinical monitoring. However, this method presents logistical challenges to insufficient trained personnel. Auxiliary methods are becoming increasingly vital. Materials and methodsTwelve swine pedicle myocutaneous flaps were harvested and monitored using infrared cameras to investigate the developed monitoring parameters and vascular thrombosis in the free flap model. ResultsThe mean flap surface temperature after vein or artery occlusion decreased significantly, but the differences were relatively small. As a result, the difference between recorded (flap surface temperature [Ts]) and predicted (estimated surface temperature [Tes]) flap surface temperature (ΔT = Ts− Tes) was used as the parameter for pedicle thrombosis. A ΔT of <0.86°C was used as a vascular occlusion criterion; the sensitivity and specificity of this parameter were 90% and 81%, respectively. The standard deviation of the surface temperature (SDT) was another indicator of vascular occlusion; the estimated sensitivity and specificity for vessel occlusion of SDT < 0.48°C were 84% and 73%, respectively. ConclusionsInfrared thermal imaging has the advantages of being noninvasive, contact-free, continuous, and able to detect the whole flap surface area. Two indicators, ΔT and SDT, can be used with high sensitivity and specificity for early prediction of flap pedicle thrombosis. Further human studies are necessary to validate clinical application of infrared thermal imaging.

The Chicken Thigh Adductor Profundus Free Muscle Flap: A Novel Validated Non-Living Microsurgery Simulation Training Model.

BackgroundSimulation training is becoming an increasingly important component of skills acquisition in surgical specialties, including Plastic Surgery. Non-living simulation models have an established place in Plastic Surgical microsurgery training, and support the principles of replacement, reduction and refinement of animal use. A more sophisticated version of the basic chicken thigh microsurgery model has been developed to include dissection of a type 1-muscle flap and is described and validated here.MethodsA step-by-step dissection guide on how to perform the chicken thigh adductor profundus free muscle flap is demonstrated. Forty trainees performed the novel simulation muscle flap on the last day of a 5-day microsurgery course. Pre- and post-course microvascular anastomosis assessment, along with micro dissection and end product (anastomosis lapse index) assessment, demonstrated skills acquisition.ResultsThe average time to dissect the flap by novice trainees was 82±24 minutes, by core trainees 90±24 minutes, and by higher trainees 64±21 minutes (P=0.013). There was a statistically significant difference in the time to complete the anastomosis between the three levels of training (P=0.001) and there was a significant decrease in the time taken to perform the anastomosis following course completion (P<0.001). Anastomosis lapse index scores improved for all cohorts with post-test average anastomosis lapse index score of 3±1.4 (P<0.001).ConclusionsThe novel chicken thigh adductor profundus free muscle flap model demonstrates face and construct validity for the introduction of the principles of free tissue transfer. The low cost, constant, and reproducible anatomy makes this simulation model a recommended addition to any microsurgical training curriculum.

Novel diffuse optics system for continuous tissue viability monitoring - extended recovery in vivo testing in a porcine flap model.

In reconstructive surgery, tissue perfusion/vessel patency is critical to the success of microvascular free tissue flaps. Early detection of flap failure secondary to compromise of vascular perfusion would significantly increase the chances of flap salvage. We have developed a compact, clinically-compatible monitoring system to enable automated, minimally-invasive, continuous, and quantitative assessment of flap viability/perfusion. We tested the system's continuous monitoring capability during extended non-recovery surgery using an in vivo porcine free flap model. Initial results indicated that the system could assess flap viability/perfusion in a quantitative and continuous manner. With proven performance, the compact form constructed with cost-effective components would make this system suitable for clinical translation.

Local tolerance evaluation of fibrin and thrombin solution in a free-flap model in the juvenile Sprague-Dawley rat

Local tolerance evaluation of fibrin and thrombin solution in a free-flap model in the juvenile Sprague-Dawley rat

Application of fibrin glue in microvascular anastomoses: comparative analysis with the conventional suture technique using a free flap model

Application of fibrin glue in microvascular anastomoses: comparative analysis with the conventional suture technique using a free flap model

The Effect of Ischemic Preconditioning on Secondary Ischemia in Myocutaneous Flaps

We sought to determine the effect of ischemic preconditioning (IPC) on secondary ischemia in myocutaneous flaps in a rat model. Forty rectus abdominis myocutaneous flaps were elevated in 40 rats, and the animals were randomized into control or IPC groups (20 flaps each group). All flaps were then subject to primary ischemia for 2 hours via pedicle clamping. Twenty-four hours later, the control and IPC flaps were randomized to two groups each of 1 or 2 hours of secondary ischemia (4 groups, 10 flaps per group). Flap survival was evaluated on postoperative day 5 by measuring the percentage area of flap survival by a blinded observer. Mean flap survival area and total necrosis rates were compared between the groups. In the 1-hour secondary ischemia groups, IPC improved mean flap survival area from 11 +/- 7% to 36 +/- 22%, and the total necrosis rates from 40 to 0%. These differences were statistically significant (p < 0.006, p < 0.05, respectively). In the 2-hour secondary ischemia groups, differences were not statistically significant (p = 0.2, p = 0.4, respectively). IPC improves the survival of myocutaneous flaps subjected to secondary ischemia of 1 hour in this rat free flap model.

Vascular Anatomy of the Hamster Retractor Muscle with Regard to Its Microvascular Transfer

Background: The hamster retractor muscle (RET) is used as an in vivo model in studies of skeletal muscle ischemia-reperfusion injury. The RET is unique in that the muscle can be isolated while preserving the primary vascular supply so that its contractile function can be measured simultaneously with local microvascular responses to experimental interventions. The goal of this study was to understand the anatomical origin of the vascular supply to the RET and determine whether the RET can be used as a free flap after surgical isolation of the thoracodorsal vessels. Methods: Microdissection was performed to determine the anatomy of the vasculature that supplies and drains the RET. Results: Distinct numbers and patterns of feed arteries (2–4) and collecting veins (1–3) were identified (n = 26 animals). Dye injection (n = 8) of the thoracodorsal artery demonstrated that the RET remains perfused following its isolation on the thoracodorsal pedicle. Heterotopic allograft transplantation of the RET (n = 2) was performed by anastomosing the thoracodorsal vessels to the femoral vessels using the end-to-side technique. Conclusions: The anatomical relationships indicate that the RET can be used as a free flap model for evaluating the effect of preservation strategies and transplantation on skeletal muscle microcirculation and contractile function.

Free Pectoral Skin Flap in the Rat Based on the Long Thoracic Vessels

The purpose of this study was to investigate the vascular anatomy of the pectoral region of the rat to develop a free pectoral skin flap model. In Experiment 1 (n = 6), we performed anatomic dissection and angiographic study of the pectoral region. In Experiment 2 (n = 20), we performed microsurgical free transfer of a pectoral skin flap to the cervical or groin region. Half of the flaps were transferred with flow-though arterial anastomoses. All flaps survived except for 2 cases of autocannibalization. We conclude that the free pectoral skin flap model in the rat is simple and reliable, and can be used as an alternative experimental and training model to the superficial epigastric flap.

Comparative Study of Different Combinations of Microvascular Anastomoses in a Rat Model: End-to-End, End-to-Side, and Flow-Through Anastomosis

This study aimed to compare several microvascular anastomotic techniques by patency rate using a free flap model in rats. A microsurgical transfer model of a pectoral skin flap to the cervical region was used. In experiment 1, 120 rats were divided into four groups (n = 30 in each group) depending on the type of microvascular anastomotic technique. For group 1, end-to-end anastomoses were performed for arteries and veins. For group 2, end-to-side anastomoses were performed for arteries and end-to-end anastomoses were performed for veins. For group 3, flow-through anastomoses were performed for arteries and end-to-end anastomoses were performed for veins. For group 4, end-to-end anastomoses were performed for arteries and end-to-side anastomoses were performed for veins. Flap survival was assessed on day 3 and the success rates of the four groups compared. In experiment 2 (n = 10), postoperative blood flows of end-to-end and flow-through arterial anastomoses were measured. : In experiment 1, the success rates in groups 1, 2, 3, and 4 were 76.7, 83.3, 100, and 83.3 percent, respectively. Differences between group 3 and the other groups were statistically significant. In experiment 2, the blood flow of flow-through arterial anastomosis (1.8 ml/minute) was much higher than that of end-to-end anastomosis (0.18 ml/minute). : Flow-through arterial anastomosis presented a higher blood flow through the anastomotic site, resulting in a higher success rate than conventional anastomoses. In veins, end-to-side anastomosis was equivalent to end-to-end anastomosis even though the diameter of the donor vein was larger than the recipient vein.

Effect of Recipient Arterial Blood Inflow on Free Flap Survival Area

The influence of using different recipient arteries on free flap survival area has not been well studied. The purpose of the authors' present study was to compare the survival areas of free flaps transferred to different recipient arteries with different blood inflow and to investigate the vascular structural changes in the flaps. The authors developed a free three-territory flap model on the back of a rat. This three-territory flap was elevated based on the thoracodorsal vessels, which were dissected to the axillary vessels. In group 1, the control group (n = 16), the flap was transferred to the abdominal skin defect as a pedicled flap after 60 minutes of clamp ischemia. Groups 2 (n = 24) and 3 (n = 24) were free flap models that were transferred to different recipient vessels. The axillary vessels were anastomosed to the common carotid artery and the external jugular vein in group 2, and to the femoral vessels in group 3. On day 5, evaluation of the survival area of the flap, whole-body angiography, and measurement of arterial inflow to the flap were performed. The greatest mean flap survival was seen in group 2 (94.3 percent). The differences between groups 1 and 2 and groups 2 and 3 were statistically significant. Angiographic studies demonstrated that the second choke zone in group 2 dilated extensively, but in groups 1 and 3, the second choke zone dilated only slightly or remained unopened. The results suggest that augmenting the arterial inflow of a free flap could open the second choke zone and improve flap survival area.

Application of fibrin glue in microvascular anastomoses: Comparative analysis with the conventional suture technique using a free flap model

Several studies have already reported the utilization of fibrin glue in microvascular anastomoses to minimize the number of sutures and to decrease the operative time. Despite the good results obtained in most of these experiments, its clinical application has not launched. The aim of this study was to clarify the controversies around the safeness of fibrin glue application in microvascular anastomoses, and also to demonstrate the potential benefits of fibrin glue application in a realistic free flap model. Twenty-seven rabbits were used in this study. The experimental model consisted of a free groin flap transfer to the anterior cervical region. The flap's circulation was restored by means of an end-to-side anastomosis between the femoral and carotid arteries, and an end-to-end anastomosis between the femoral and external jugular veins. The animals were divided into two groups (n = 10) according to the anastomosis technique: Group I (conventional suture) and group II (fibrin glue). The number of sutures required to complete the arterial and venous anastomoses was reduced in 39 and 37% in group II, respectively. Despite this reduction, the anastomoses maintained adequate patency rates and mechanical strength. Both arterial and venous anastomoses benefited from fibrin glue application, which made them easier and faster to perform. The flaps' ischemic time and the total operative time were also significantly shortened. In this study, the application of fibrin glue in microvascular anastomoses was safe and reliable. The risk-benefit ratio of fibrin glue application in microvascular anastomoses is favorable for its use.

Effect of Celecoxib on Fasciocutaneous Flap Survival and Revascularization

To study the effect of celecoxib (Celebrex; Pfizer, Cambridge, Mass) on (1) primary ischemic time and (2) revascularization of fasciocutaneous free flaps in a rat model. In the ischemia study, 50 male Sprague-Dawley rats were divided into 2 groups of 25 rats each, a control group and a celecoxib group. Five rats in each treatment group were exposed to ischemic times of 4, 6, 8, 10, and 12 hours. Survival of the flap was assessed 7 days after reversal of the ischemia. Probit curves and the critical ischemic time were calculated. In the revascularization study, 30 male Sprague-Dawley rats were divided into 2 groups of 15 rats each. One group was fed celecoxib, while the other was fed a normal diet. All rats had a 3 x 6-cm fasciocutaneous flap based on the inferior epigastric artery elevated and exposed to 2 hours of primary ischemia. The flap was then sutured back into the wound bed. Each of these groups was then divided into 3 groups of 5 rats whose pedicles were divided on postoperative day 5, 6, or 7. Percentage survival of the flap was measured 7 days later. In both parts of the study, the experimental group was fed celecoxib, 1500 ppm, throughout the interoperative period. In each animal, a 3 x 6-cm ventral fasciocutaneous groin flap based on the left superficial epigastric artery was elevated. In the ischemia study, respective flap survival rates from the control and celecoxib groups at the various ischemic times were as follows: 4 hours, 100% and 100%; 6 hours, 80% and 100%; 8 hours, 80% and 80%; 10 hours, 60% and 60%; and 12 hours, 20% and 10%. The median lethal ischemic times were 9.7 and 9.6 hours, respectively. There was no statistical difference in flap survival between the celecoxib and control groups. In the revascularization study, ligation of the flap pedicle on day 5, 6, or 7 did not result in any difference in the percentage of flap survival among the 3 groups. Celecoxib appears to have no deleterious effect on free tissue transfer survival or healing, as evidenced by revascularization in a fasciocutaneous free flap model.

Intratissular Lymphaticovenous Anastomoses Demonstrated by Perioperative Intramuscular Injection of 99mTc-Colloids

The existence of intratissular lymphaticovenous anastomoses has often been suggested, but it has never been demonstrated. This study aims at demonstrating the presence of such anastomoses. The free flap model was used to investigate the drainage of radiolabeled colloid particles whose size prevents direct passage to the blood vessels. The tracer was injected into the muscle or the skin during the surgical procedure. Blood samples were sequentially drawn from the venous pedicle over the 30 minutes that followed the tracer injection. The blood samples were counted using a gamma well-counter. In all 14 patients, the venous blood radioactivity steadily increased over time. Radiochemical analyses performed on the blood samples demonstrated that the radioactivity is related to the labeled colloids and not to free pertechnetate. Planar imaging performed 24 hours after the surgical procedure showed a significant liver uptake, and no accumulation in the area of normal lymphatic relays. As, in the free flap model, there is no lymphatic drainage through the classical pathways whatsoever, and since the size of the radiolabeled particles prevents them from directly entering the blood stream, the results strongly suggest the presence of functional intratissular lymphovenous anastomoses.