| BackgroundClinical research and application of skin flaps can be mainly divided into four stages:Before the twentieth Century50’s, they were mainly random pattern skin flap transferred with pedicle; In twentieth Century50-60years, muscle flap and axial pattern skin flap appeared; Seventies of last century, with the birth and development of microsurgical technique, the free flap tallied the blood vessels, musculocutaneous flap and musculoskeletal skin flap came to use; since1980s, clinical application of skin flaps got unprecedented development, the main artery flap, reverse island skin flap, distal pedicled flap, fascial cutaneous flap, muscular septal vascular flap, venous flap, subdermal vascular network flap, neurocutaneous flap pedicled with superficial vein and perforator flap are successive developed.In the80’s in20centuries, with the development of fine microsurgical operating instrument and the actual need of clinical, perforator flap, a new type of flap occurred.It was the new development of microsurgical flap transplantation. Stepanov first reported the clinical application of perforator flap in1980. Because the original was Russian, it did not cause the micro plastic surgery industry colleagues attention at that time. In1984, China’s anatomy scholar Shen Huailiang reported "buttock musculocutaneous perforator" positioning and quantitative results, and clearly pointeds out: The superior gluteal artery and the inferior gluteal artery perforators are the main blood supply of the skin in gluteal region. This perforator vessel axis may be considered for the design of flap. However, unfortunately because of the technology and equipment constraints, the report did not cause the attention of peer. The transfer flap of musculocutaneous perforator pedicle was reported by Kroll in1988. The skin flap pedicled with deep inferior epigastric artery musculocutaneous perforator was reported by Koshima in1989. The technology did not damage the deep inferior epigastric artery, and did not carry the rectus abdominis. The flap obtained was thin, and the repair effect was perfect. Until the operation modes were reported, the plastic surgeons began to recognize muscle was not necessary component for maintaining skin tissue survival. The small perforator can also be used as a vascular pedicle to support a certain amount of tissue, and the clinical repair effect is very good. So the plastic surgery field really ushered in the era of perforator flaps.However, the simple perforator flap was obtained pedicled with the usually only with diameter smaller musculocutaneous perforator or septocutaneous perforator flap. Therefore, the donor area is relatively small. With the development of modern agriculture and Industry, there are more and more trauma patients, such as traffic accident injury, severe burns and severe skin avulsion. These patients were often associated with a large area of skin and other tissues defects. While the early, good coverage for the wound is an important link of surgical repair. Therefore, the extended large perforator flap which has small injury to the donor site has become the key for repair.The skin in anterolateral abdominal wall is usually large expanses, relative concealment, and the fat layer is usually richer than other parts of the body. These characteristics make this region easy access to large area, large volume of extended flaps in clinical. The most typical clinical application of extended perforator flap in anterolateral abdominal wall is used for breast reconstruction. It was the first reported that the application of lower abdominal free transverse rectus abdominis myocutaneous flap (TRAM flap) to reconstruct the breast in1979by Holmstrom. Hartrampf successfully applied the pedicled TRAM flap for breast reconstruction in1982. Along with the research and technical progress, Blondeel and Allen successfully used deep inferior epigastric artery perforator flap (DIEP flap) for breast reconstruction in1994. Since then, a DIEP flap for clinical breast, vagina, penis reconstruction and head, neck, upper limb and lower limb defect repair reaches a climax30years. This also logically made the DIEP flap became outstanding representative of extended perforator flap in clinical application. In stark contrast to the research and application of the modified various flap with vigour and vitality is that the study on the flap anatomy, especially the theoretical basis of extended perforator flap is relatively lack. Therefore, in order to provide anatomical reference for extended perforator flap on the anterolateral abdominal wall for the clinical, we carried on research about blood supply and their acompanied nerves of the perforator flap on the anterolateral abdominal wall in detail.Objectives1. Provide applied and digital anatomical basis of acquiring extended perforator flap or compound flap for clinical use through the study of perforating vessels and acompanied nerves by applied anatomy and3D Mimics reconstruction in anterolateral abdominal wall.2. Design extended perforator flap of anterolateral abdominal wall by using3D reconstruction perforators.3. Provide a new safe and convenient method for the micrangium morphology research by exploring the best proportion of perfusion liquid latex-bismuth oxide in microvascular perfusion technique.Methods1. Applied anatomy and three dimensional reconstruction of extended perforator flaps in anterolateral abdominal wall5Formalin soaked specimens were used and underwent red latex injection and dissected layer by layer in anterolateral abdominal wall. The systemic arteriography using the modified mixture of lead oxide-gelatine was performed on10fresh adult voluntarily donated cadavers (mail8, female2). All of the cadavers were serially scanned by a spiral CT. Then perforates and their source arteries of anterolateral abdominal wall were3D reconstructed by Mimics. The relevant information of perforates were also observed by layers dissection combined with X-ray examination. Lead oxide-gelatine solution formula:gelatine5g,40℃warm water100ml, lead oxide100g. That was volume to weight ratio of the solution and contrast agent is1:1. Perfusion fluid volume:20-30ml/kg.1.1Applied anatomy of extended perforator flap in anterolateral abdominal wallBefore perfusion, spiral CT scanning was underwent; after perfusion, and then the whole body X-ray and spiral CT scanning was done. Next anterolateral abdominal wall was dissected layer by layer. The skin and subcutaneous tissue of anterolateral abdominal wall were full intercepted on surgical plane. The cadavers were striped in the superficial layer of the external abdominal oblique fascia and the rectus sheath from lateral to medial. Near the posterior axillary line to the anterior axillary line, attention should be paid to1-3columns posterior intercostal (subcostal) vessels and their accompanied lateral branches of intercostal (subcostal) nerve pireing through the external abdominal oblique to superficial layer. Near the anterior axillary line, attention should be paid to the perforators of superficial circumflex iliac artery and superficial epigastric artery. The perforators should be observed, measured and marked off, then cut off. The dissection was continued medially. When close to the semilunar line near the lateral edge of rectus abdominis sheath, it should be carefully dissected. The lateral row perforators and medial row perforators of deep inferior epigastric artery, vein and superior epigastric artery, vein, and their acompanied nerves should be observed and preserved. They should be marked before cut. According to this method, rectus abdominis, obliquus externus abdominis, obliquus internus abdominis, the transversus abdominis and extraperitoneal organization were dissected by layers, at the same time x-ray was took. The diameter≥0.5mm perforators should be observated and dissected especially. The origin, number, diameter, route, density, nutrition area and cross regional anastomosis of cutaneous arteries were payed attention and meseaured.Statistical method:The data were analyzed by using SPSS13.0software in descriptive statistics analysis. Results were expressed in the form of (x±s).1.2Three dimensional reconstruction and flaps design of extended perforator flaps in anterolateral wall abdominal1.2.1The skeleton reconstruction before non-perfusion imaging agent After perfusion imaging agent lead oxide skeletal imagings were affected by artery angiography agent, segmentation of skeletal reconstructions was difficult. In order to solve this problem, a CT scan could be done before perfusion and the bones could be reconstructed first. Then arteries, skin, subcutaneous tissue and part bones were reconstructed after perfusion imaging agent. The two times reconstruction bones would be registered.The skeletal threshold should be setted appropriately, and threshold segmentation would be done by Mimics segmentation tools. Continuous skeletal structures would be selected by using region growing tool for new mask. At last "calculate3D from mask" could be done. Finally the skeletal3D reconstruction model was exported out with STL format file for registration.When3D reconstruction was done by using Mimics, it was a crucial point that seting the appropriate threshold to extract tissue should be paid attention to. If left interval of threshold was set too low, many noise points would be extracted. If left interval was set too high, a lot of bone tissue would be lost.1.2.2Related structures were reconstructed after perfusion imaging agent1.2.2.1The perforators of anterolateral abdominal wall were reconstructed by the fast direct volume rendering (VR) method3D images of vascular reconstruction could be showed by using "Show/hide the volume rendering" tool.1.2.2.2The perforators and other related structures of anterolateral abdominal wall were reconstructed by dynamic reconstruction (DR) methodI Related bones were reconstructed Firstly, all layers data in axis view should be erased all gray value by using multiple slice edit of segmentation tools button. Secondly, the skeletal outline according to the shape of bones would be drawn in the axial view. At last, the added new Mask could be3D reconstruction. Next, the saved STL file bones could be imported to register.Ⅱ Perforators in anterolateral abdominal wall were reconstructed by dynamic reconstructionIn order to reduce the3D dynamic reconstruction workload of the computer and editing time of manual extraction of single perforator, first CTA data imported into Mimics software should be cut by "Crop Project" tool.It was very important to set the appropriate threshold to extract vessels. The proper threshold was the necessary precondition of clearly showing cutaneous perforators anastomosis. After repeated experiments, contrast, the lowest threshold was set to350-450.All the gray value of each independent organization structure should be wiped by using "Remove" tool of "Multiple Slice Edit".Then the new Mask erased irrelevant tissue could be reconstructed.It was relatively simple to3D editor when threshold lower bound was selected high (such as2976) to dynamic reconstruction. But only the artery trunk and a few large perforators could be reconstructed by this method. Redundant structure or noise points should be gradually removed by using the lasso and erase (Remove) tools of "Edit Mask in3D".The3D reconstruction should be done to the edited corresponding plane Mask after the3D edit toolbar was closed. All the trunks and a little big perforator’s3D model of the anterolateral abdominal wall could be obtained as threshold lower bound was selected2976. It was relatively complex to3D editor when threshold lower bound was selected low (such as400) to dynamic reconstruction. But the perforators and extended anastomosis could be clearly shown by this method. The reconstruction methods were same as that set high threshold. Just that it was more difficult to erase independent structure or noise when3D edited. At the same time, the vascular distribution knowledge in the anterolateral abdominal wall was required.Ⅲ Reconstruction of the skin, superficial fascia in anterolateral abdominal wallThe threshold settings were adjusted to the threshold range of skin or superficial fascia. The new Mask was established respectively. All the gray value of independent structure should be erased in the axial view. Then3D reconstruction was done respectively. Wrapping operation could be done if the skin or superficial fascia presented intermittent phenomenon.2. Study on latex-bismuth oxide micro-vascular perfusion techniqueIn this experiment contrast agent bismuth oxide was instead of lead oxide. They have similar density and similar development effect. But bismuth oxide is the green heavy metal with very low toxicity.2.1Vascular perfusion simulation experiment30scalp intravenous needles (0.6mm) were divided into5groups, each group of3. Latex-lead oxide and latex-bismuth oxide (volume to weight ratio was all1:1) were injected, at the same time just adjust the latex concentration to test the suspension effect of contrast agents of different concentrations of liquid latex.2.2Explore the best dilution ratio of latex 12rabbits were randomly divided into4groups,3rats in each group. The volume to weight ratio of latex solution containing60%natural latex and bismuth oxide was all1:1. Just the latex dilution ratio with ammonia was adjusted to test optimal dilution ratio when the latex suspension was the best.2.3Explore the best ratio of latex, bismuth oxide9rabbits were randomly divided into3groups,3rats in each group. The concentration of the latex solution containing60%natural latex was constant. The ratio of bismuth oxide was adjusted to test the best ratio of latex and bismuth oxide.Results1. Morphology of perforators in the anterolateral abdominal wall(1) The medial row perforators of deep inferior epigastric artery are located in the medial1/3of rectus abdominis muscle, and lateral row perforators are located in the lateral1/3of the muscle. The perforators are mainly distributed from the last tendinous upper the umbilical to below the umbilicus within8.0cm, especially in the range4.0cm under umbilical or on both sides of paraumbilicus. There are constant diameter≥0.8mm perforators accompanied with nerves within this region. X-ray shows there are rich transverse true anastomoses of DIEP running over midline of anterolateral abdominal wall. The total number of observed diameter≥0.5mm perforators is182, each side about6in15(30sides) specimens of this paper. Perforator pedicle length is (2.4±0.7) cm. Perforator diameter is (0.7±0.2) mm. Single perforator supply area is (32.9±14.8) cm2. The medial row perforators are the dominant perforators of DIEP.(2) Superior epigastric artery sends out a big perforator (diameter≥1.0mm) in the ending point of the rectus abdominis to provide nutrition to the skin. The total number of observed diameter≥0.5mm perforators is142, each side about5in15(30sides) specimens of this paper. These perforators exite mainly located from the sixth intercostal space to the first intersectio tendinea of rectus abdominis. Perforator pedicle length is (2.5±1.0) cm. Perforator diameter is (0.6±0.1) mm. Single perforator supply area is (34.4±8.9) cm2.(3) Superficial epigastric artery forming direct cutaneous perforator distributes the skin in lower part of anterolateral abdominal wall. There is a large range of variability of this artery.25cases single branch type and5cases double branch type in15(30sides) specimens of this paper. The vascular diameter has a great variation. When the dominent superficial epigastric artery appears, the diameter is up to2.0mm. The main trunk running11.0cm in the superficial fascia is divided into medial and lateral branches. Perforator pedicle length is (8.6±3.3) cm. Perforator diameter is (1.3±0.5) mm. Single perforator supply area is (116.5±44.1) cm2.(4) Superficial iliac circumflex artery usually divided into superficial and deep branches. The diameter of superficial branch of superficial iliac circumflex artery is up to1.2mm. The superficial branch supplies flexion region skin of the hip joint by direct cutaneous perforator, and there is considerable variation in its nutrient area. Perforator pedicle length is (8.1±2.0) cm. Perforator diameter is (1.1±0.3) mm. Single perforator supply area is (55.1±18.3) cm2.(5) Deep iliac circumflex artery is divided into three sections:inguinal segment, inner iliac crest segment and upper iliac crest segment. According to the artery branch distribution area, its branches can be divided into three types:abdominal wall muscular branches, iliac crest branches and muscular perforators.1-3muscular perforators from upper iliac crest segment are located near the middle axillary line. They are in (5.5±0.6) cm range above anterior superior iliac spine. There is important value of clinical application of these perforators. The iliac crest branches come from deep iliac circumflex artery, diameter0.3-0.7mm, have important clinical significance. Perforator pedicle length is (2.9.±0.9) cm. Perforator diameter is (0.6±0.2) mm. Single perforator supply area is (42.8±13.7) cm2.(6) Lateral branches of posterior intercostal artery and subcostal artery are near the midaxillary line and pire through the external abdominal oblique fascia to subcutaneous. And instantly they send out anterior branches and posterior branches. The musclar branches of lateral branches of posterior intercostal muscle and subcostal artery is parallel to the anterior edge of latissimus dorsi longitudinal arranged in1-3rows. The first row is in the midaxillary line to subcutaneous layer. The second is in the anterior axillary line, and the third row is in the midclavicular line. Perforator pedicle length is (3.0±1.0) cm. Perforator diameter is (0.7±0.2) mm. Single perforator supply area is (37.8±11.7) cm2.(7) The superior branch of external pudendal artery, as direct cutaneous perforator, crosses the pubic crest and distributes in the skin near the symphysis pubis. Perforator pedicle length is (7.1±1.8) cm. Perforator diameter is (0.8±0.3) mm. Single perforator supply area is (19.6±5.8) cm2.2.3D reconstruction and extended flaps design of perforators in anterolateral abdominal wall(1) We can fast and roughly show the positions and source arteries of the main perforators in the anterolateral abdominal wall by fast direct volume rendering (VR) reconstruction method.(2) We can acquire three-dimensional images of perforators by dynamic reconstruction (DR) method. By seting higher threshold to segmentate and reconstruct we can obtain the arteries trunks and little large perforators. By seting appropriate lower threshold we can extract, modele and color-separated the single perforator. At the same time, we can combine the adjacent perforators freely. Further more, we can clearly show the position and anastomosis of the ectended branches.(3) Through setting appropriate threshold we can obtain3D reconstruction models of the pelvis, femur and anterior thorax wall without perfusion imaging agent. And then we registrate the bones to part corresponds bones reconstructed by "Multiple Slice Edit". At the same time we can obtain skin and superficial fascia in anterolateral abdominal wall by reconstruction.(4) We can take advantage of the3D model of perforators and their related structures obtained by using VR method and DR method of Mimics software to design free combination extended perforator flaps. It is very convenient, fast and intuitive.This method is ready to provide direct, reliable, convenient and useful digital anatomy data for clinical flap operation.Especially we can obtain a single perforator with its sourse vascular and related structures. After color separation processing, we will be very easy to realize the free combination of extended perforators under3D view, which provides more choices for the design of clinical extended perforator flaps.3. The best ratio of latex and bismuth oxide in microvascular perfusion technique(1) Vascular perfusion simulation experiment:Through deposition observation, injector bolus conditions, and X-ray radiography, we can find that the suspension force is more and more smaller with the latex solution being diluted.(2) If volume to weight ratio of latex and bismuth oxide unchanged, with the increase of the dilution ratio of latex with ammonia, rabbit skin perforators’ development effect is more and more worse. (3) If latex concentration is constant, it is the optimal proportion that volume to weight ratio of latex and bismuth oxide is1:1.Conclusions1. Myocutaneous perforators of deep inferior epigastric artery, superior epigastric artery and lateral braches of posterior intercostal artery have the superiority to obtain large extended perforator flaps, because of reliable deep vascular pedicle, easy expansion of subcutaneous vascular anastomosis net, relaxation skin in abdominal wall and rich tissue content.2. The medial row perforators are the dominant vessels of deep inferior epigastric artery. The perforator close to umbilicus should be first choosed when DIEP flap is designed. It is reasonable to take a transverse DIEP flap.3. Big muscular branches of inguinal segment and inner iliac crest segment of deep iliac circumflex artery, iliac crest branches of inner iliac crest segment and muscular perforators of upper iliac crest segment are the important anatomic basises to design deep iliac circumflex artery chimeric perforator flap.4. Superficial epigastric artery forming direct cutaneous perforator distributes the skin in lower part of anterolateral abdominal wall. When there is a dominant superficial epigastric artery, the perforator pedicled flap is a good choice.5. We can clearly and perfectly realizate the3D modeling of perforators in anterolateral abdominal wall by using VR and DR. methods of Mimics software.6. Latex-bismuth oxide microvascular perfusion technique is a good development, safe and convenient microvascular perfusion method. The optimal ratio of latex and bismuth oxide is100ml latex and100g bismuth oxide (volume to weight ratio of latex and bismuth oxide is1:1).The innovative point of the study1. Two times CT scans are taken before and after perfusion imaging agent and two reconstruction of the skeleton is registered, the reconstruction of the vascular tree and bone can be perfectly and clearly showed at the same time;2. Traditional anatomy is combined with digital anatomy, it can be solved the problem that small nerve can not be displayed by angiography and3D reconstruction;3. Anterolateral abdominal wall perforators are analyzed accurately in3D positioning and quantitative data;4. Clear display of the anterolateral abdominal wall artery anastomosis between the vascular (Choke vessels), to provide the anatomical basis for the characteristics flap design, such as:DIEP flap transverse cross (across the ventral midline), deep iliac circumflex artery perforator chimeric flap etc..5. Optimization of latex and bismuth oxide micro angiography. |
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