Bone flap prefabrication: an experimental study in rabbits

The usual method to prefabricate a bone flap is to harvest a nonvascularized bone graft and to implant the artery and vein bundle between segments of bone graft. The basic problem of this method is sacrificing an artery for prefabrication. Another method for creating flap donor sites without using an artery is venous flap prefabrication. There are a few articles describing bone flap prefabrication, and these include implantation of both artery and vein as a vascular bundle. Also, there is no experimental study in the literature using a vein or an arterialized vein pedicle for bone flap prefabrication. As an experimental model for bone flap prefabrication, the rabbit ear vascular model was chosen. For the experiments 3 groups were formed. Each group contained 5 rabbits. In the first experimental group a vein was implanted between the halves of bone graft. In the second experimental group an arterialized vein was implanted between the halves of bone graft. To compare the viability of the bone graft of the 2 prefabrication groups, a bone graft was implanted into the subcutaneous pocket of the posterior auricular area in the third group. The authors examined 5 rabbits in each group by microangiography at the end of 6 weeks except for group 3. On microangiographic analysis, groups 1 and 2 showed patency of the vascular pedicle. There was no difference between these 2 groups from the point of view of vascular patency and bone appearance. Bone scintigraphy was performed for 5 rabbits in each group. On bone scintigraphic scans, the bone component of the flaps was visualized in groups 1 and 2, but not in group 3. A quantitative analysis of images was performed by drawing symmetric spherical regions of interest (ROIs) over both the implanted area and cranial bone. The uptake ratios were computed by dividing the mean counts in the implanted ROI by mean counts in the cranial bone ROI. The mean value was 0.86 +/- 0.02 in group 1 and 0.86 +/- 0.04 in group 2. A statistically significant uptake difference was not seen between venous and arterialized venous groups (P < 0.01). Histologic examination was performed all rabbits in each group, and demonstrated that the bony component was viable, showing osteocytes containing lacunae, osteoblasts along bony trabeculae, and vascular channels in groups 1 and 2. In group 3, the bony architecture of the graft was still apparent, but all bone within it was dead. There were no significant microangiographic, histologic, and scintigraphic differences between the 2 experimental methods.     

Fat prefabrication using a fascial flap in the rat model.

Prefabrication of fat tissue using a fascial flap based on the superficial inferior epigastric artery was studied in rats. First, the superficial inferior epigastric fascia was transposed over the inguinal fat pad. Two weeks later fascia and fat were elevated together as a prefabricated composite flap. At this stage, a pilot study was done in ten rats and perfusion of the flaps was tested with fluorescein. After confirming fluorescein staining of the prefabricated flaps, the study continued with experimental and control groups of rats. In the experimental group, prefabricated flaps were transposed to the subcostal area. In the control group, the pedicles of the flaps were severed, creating composite grafts. These grafts were transferred to the subcostal area in the same manner as in the experimental group. One week later the flaps were re-elevated and grafts were exposed. Fluorescein tests and Indian ink microangiography were carried out. In the experimental group, the flaps were stained, while grafts in the control group were not stained. Fat and fascia were found to be viable in the experimental group, while they were necrotic in the control group on histopathological examination. Based on these findings, we can conclude that the prefabrication of fat by vascular fascia is successful and may have application in plastic surgery.     

Preserving osseous viability in osteocutaneous flap prefabrication: experimental study in rabbits

This study presents a technique that preserves osseous viability in prefabricated osteocutaneous flaps with a soft-tissue vascular carrier, with a pedicled skin flap acting as the vascular carrier to neovascularize a partially devascularized bone segment before its transfer. Using a total of 50 New Zealand White rabbits, two groups were randomized as experimental and control animals. In the experimental group (n = 30), a bipedicled dorsal scapular skin flap was anchored with sutures to the scapular bone, by bringing it into contact with the exposed dorsal surface of the bone after stripping the dorsal muscular attachments. Following 4 weeks of neovascularization, the prefabricated composite flaps were harvested, based on the caudally-based dorsal skin flap, after stripping the ventral muscular attachments of the bone. In the control group (n = 20), non-vascularized scapular bone grafts were implanted under bipedicled dorsal scapular skin flaps with sutures. After 4 weeks, prefabricated composite flaps were harvested, based on the caudally-based dorsal skin flap. In both groups, on day 7 after the second stage, the viability of the bony component of the flaps was evaluated by direct observation, scintigraphy, measurement of bone metabolic activity, microangiography, dye injection study, and histology. Results indicated that the bone segments in the experimental group demonstrated a greater survival than in the control group. The authors conclude that this technique of osteocutaneous flap prefabrication preserves the viability of the bony component with a soft-tissue vascular carrier, in contrast to the conventional method of pre-transfer grafting. The technique may be useful clinically in selected cases.     

Impact of tissue expansion on flap prefabrication: An experimental study in rabbits

This study was designed to determine whether tissue expansion after vascular pedicle implantation would increase the survival area of prefabricated skin flaps. In 20 New Zealand white rabbits, the vascular pedicle consisting of the central artery and vein of the left ear was implanted into the neck. At the time of pedicle implantation a subcutaneous pocket was created measuring 5 × 14 cm beneath the implantation site. Tissue expanders of three different sizes and volumes were implanted in the rabbits of three treatment groups. No tissue expander was implanted in the animals of the control group. All flaps were transposed after 3 weeks to the contralateral ear, and flap survival was assessed 1 week later. The increased area of the flap survival was statistically significant in all three treatment groups compared to the nonexpanded flaps (P = 0.003, P = 0.004, P < 0.0001, respectively). In addition there was a statistically significant larger area of survival using a 100-cc expander measuring 5 × 14 cm (the same size as the elevated flap) compared to 40-cc (3 × 5 cm) or to 60-cc (4 × 8 cm) expanders (P < 0.001, P = 0.004, respectively). The one-way analysis of variance and the t-test were used to show statistical differences. We conclude that the time necessary for neovascularisation of the skin flap could be used to expand the tissue, not only increasing the amount of available tissue, but also enhancing the vascularity. © 1996 Wiley-Liss, Inc.     

Bare dorsal thoracic fascial flap for esophageal defects: an experimental study with dogs

Background

Reconstruction of esophageal defects has challenged reconstructive surgeons for a long time. Problems that affect the continuity of the orogastic tract influence the patient’s quality of life and general health. Bare free fascial flaps are used to restore soft tissue defects of the oral cavity because they provide thin, pliable tissues with a high capacity for epithelialization to preserve the local anatomy. An experimental study was planned to investigate reconstruction of anterior cervical esophageal defects using a pedicled dorsal thoracic fascial flap.

Methods

Eight hybrid dogs were used in the study. All operations were planned in three steps and performed with the animals under general anesthesia. For the two-layered reconstruction, the bare dorsal thoracic fascial flap was harvested and adapted like a patch to the defect.

Results

No partial or total flap loss was observed. On postoperative day 20 surgery, a complete epithelial lining on the same plane as the esophageal mucosa was observed over the flap tissue. A 4- to 5-mm longitudinal scar that did not form even a minimal stricture in any dog also was observed. No significant changes from postoperative day 20 to postoperative days 40 and 60 were observed.

Conclusion

Bare fascial flaps in the oral cavity heal with spontaneous epithelialization and with no need for skin and mucosal grafts. Fascial flaps are easy to harvest and do not cause any functional loss because they are nonfunctional units. Their thin constitution helps the surgeon to shape the tissue and even form tubed flaps.     

皮瓣延迟后对皮瓣预制时间影响的实验研究

为了探寻缩短皮瓣预制时间的新方法，作者设计了两组皮瓣预制方法进行比较。Ａ组为皮瓣延迟实验组，Ｂ组为正常皮瓣预制对照组。皮瓣预制后２周进行血管灌注检查和皮瓣移植。结果：Ａ组皮瓣成活范围大，植入血管与原皮瓣之间血管吻合支多；Ｂ组皮瓣成活面积小，血管网形成范围小，吻合支少。结论：皮瓣延迟后皮瓣预制时间可大大缩短，从而缩短了手术周期。     

异体骨预制骨皮瓣的实验研究

目的 探讨异体骨异位埋置预制骨皮瓣的可行性. 方法 从2010年11月至2011年7月,用广西巴马小型猪为实验动物,先制作深低温冷冻异体骨备用;异体骨经复温后置于旋髂浅动脉供养的皮瓣组织内,按植入部位不同分3组:皮下组(A组)、深筋膜下组(B组)、肌内组(C组),术后培养观察.指标:异体骨ECT显像(分别于术后第4周、第8周、第12周),血管造影检查、异体骨病理学检查(术后第12周). 结果 3组预制骨皮瓣术后ECT扫描显示:第8周和第12周异体骨植入部位放射性较4周时增高,差异有统计学意义(P＜0.05);血管造影显示在皮下组织、筋膜下组织、肌肉组织内的异体骨均有血管化,并与相应区域旋髂浅动脉建立血管联系;病理检查可见异体骨在筋膜下组织和肌肉组织内血管化作用和诱导新骨形成较明显. 结论 可以用异体骨异位埋置预制骨皮瓣.     

Principles of flap prefabrication.

Clinical flap prefabrication can be classified according to the basic technique of plastic surgery used for the prefabrication. There are currently three methods: (1) delay or expansion; (2) grafting; and (3) vascular induction by staged transfer. Illustrative cases are given to point out the advantages and indications for each method. A fourth, still experimental, method is based on cell biology advances that are looming on the horizon and may have revolutionary future clinical applications.     

大鼠隐血管束全腹壁预制皮瓣模型的实验研究

目的:探讨一种以大鼠隐血管束为预制血管蒂的全腹壁预制皮瓣模型的设计及应用价值。方法:将18只SD大鼠按Ⅰ期手术与Ⅱ期手术之间的间隔时间2、4、6周分为三组。Ⅰ期手术制备大鼠后肢隐血管束预制血管蒂,Ⅱ期手术切开皮瓣四边,形成以预制隐血管束为蒂的岛状皮瓣。Ⅰ期、Ⅱ期术后观察皮瓣血运,记录皮瓣成活面积及成活率。检测Ⅱ期皮瓣血管蒂旁局部组织中血管内皮生长因子(VEGF)含量,取成活皮瓣制作病例切片,HE染色,计算血管密度(血管数/mm2)。运用统计学方法比较各组间差异。结果:Ⅰ期术后各组大鼠腹部皮瓣全部成活;Ⅱ期术后1周,Ⅰ组皮瓣全部坏死,Ⅱ组、Ⅲ组皮瓣平均成活率分别为(14.68±1.02)%,(16.19±1.71)%(P<0.05);Ⅱ期皮瓣局部组织VEGF平均含量:Ⅰ组243.95±4.37,Ⅱ组240.89±3.11,Ⅲ组239.19±2.61(P>0.05);大鼠平均血管密度6周组较4周组略有增多,但差别不大(P>0.05)。结论:大鼠隐血管束全腹壁预制皮瓣模型,可以作为研究提高预制皮瓣成活率的基础,Ⅰ期手术与Ⅱ期手术之间的时间间隔至少需4周。     

大鼠隐血管束全腹壁预制皮瓣模型的实验研究

目的:探讨一种以大鼠隐血管束为预制血管蒂的全腹壁预制皮瓣模型的设计及应用价值。方法:将18只SD大鼠按Ⅰ期手术与Ⅱ期手术之间的间隔时间2、4、6周分为三组。Ⅰ期手术制备大鼠后肢隐血管束预制血管蒂,Ⅱ期手术切开皮瓣四边,形成以预制隐血管束为蒂的岛状皮瓣。Ⅰ期、Ⅱ期术后观察皮瓣血运,记录皮瓣成活面积及成活率。检测Ⅱ期皮瓣血管蒂旁局部组织中血管内皮生长因子(VEGF)含量,取成活皮瓣制作病例切片,HE染色,计算血管密度(血管数/mm2)。运用统计学方法比较各组间差异。结果:Ⅰ期术后各组大鼠腹部皮瓣全部成活;Ⅱ期术后1周,Ⅰ组皮瓣全部坏死,Ⅱ组、Ⅲ组皮瓣平均成活率分别为(14.68±1.02)%,(16.19±1.71)%(P<0.05);Ⅱ期皮瓣局部组织VEGF平均含量:Ⅰ组243.95±4.37,Ⅱ组240.89±3.11,Ⅲ组239.19±2.61(P>0.05);大鼠平均血管密度6周组较4周组略有增多,但差别不大(P>0.05)。结论:大鼠隐血管束全腹壁预制皮瓣模型,可以作为研究提高预制皮瓣成活率的基础,Ⅰ期手术与Ⅱ期手术之间的时间间隔至少需4周。     

Use of free interpositional vein grafts as pedicles for prefabrication of skin flaps

Pedicles created from a long vein graft increase the scope and applications of prefabricated skin flaps. This study reports the survival and pattern of neovascularization of lower abdominal skin flaps in rabbits based on a pedicle formed by interposition of a long vein graft between the divided ipsilateral femoral artery and vein. Flaps were elevated 2–5 weeks after pedicle implantation and the surviving area quantitated and vascular patterns examined 1 week later. Only 8 out of 35 flaps were greater than 50% alive, the most frequent cause of flap failure being pedicle non-patency. If the pedicle remained patent, complete flap survival was possible as early as 2 weeks after implantation. In non-patent pedicles, recanalization or formation of a new vascular network may, given at least 4 weeks, be sufficient to ensure partial flap survival. The findings indicate that implantation of a long, skeletonized vein graft is an unreliable method of prefabrication of abdominal skin flaps in this model. © 1994 Wiley-Liss, Inc.     

The ideal rotation flap: an experimental study.

BACKGROUND/PURPOSE: Numerous modifications exist and opinions vary between surgeons with regard to the design of the ideal rotation flap. A literature review revealed inconsistencies as well as three different designs of rotation flap (standard rotation flap, Ahuja's modified rotation flap, divine rotation flap) based on entirely different concepts. It is not clear which of these designs serves its purpose best in wound reconstruction since they have not been previously examined experimentally and directly compared. The aim of this study is to determine the optimal rotation flap design in wound reconstruction. Several modifications of the standard rotation flap are examined and the three different rotation flap designs are directly compared. METHODS: This study tests the ability of various rotation flaps to close triangulated defects on sheets of neoprene, a synthetic rubber compound. Section A examines four important features in the design of the standard rotation flap: triangulation of a lesion, rotation flap circumference, pivot point and the back cut. Section B compares the standard rotation flap, Ahuja's modified rotation flap and the divine rotation flap. Tension resulting from wound closure is measured and the length of scar calculated. RESULTS/CONCLUSION: The standard rotation flap remains superior in comparison to the modified rotation flap and the divine rotation flap. Triangulation of a lesion should be performed with care and, in particular, the apex of the triangle should coincide with the geometrical pivot point. A flap circumference more than five times the width of the defect is of minimal benefit. The back cut is an effective modification and should be used if necessary.     

Revascularisation of costochondral grafts: an experimental study in domestic pigs.

Mandibular condyles are reconstructed immediately with costochondral grafts (CCGs) in children for several temporomandibular conditions, including ankylosis, benign neoplasia, and chronic arthritis. A prerequisite for growth of CCGs is that they are properly revascularised, but the revascularisation process has not to our knowledge so far been examined. The aim of the present study was therefore to investigate the revascularisation of CCGs when they were used for immediate reconstruction of the mandibular condyle in juvenile domestic pigs. Eleven mandibular condyles were experimentally resected and immediately reconstructed with CCGs. Microangiograms with an Indian ink solution were done 2, 4, 8, and 12 weeks after the reconstructions. The density of vessels was higher in measurement zones facing soft tissues than in those facing mandibular bone at all time points. Revascularisation of the growth plate originated from the surrounding recipient soft tissues and not from an endosteal blood supply from the host mandible ramus.     

Revascularization of nerve grafts: an experimental study

The time course of revascularization of grafted nerves, and the possible dependence of this revascularization on the length of the graft are two related questions that are addressed. Survival of Schwann cells in the nerve graft and a timely revascularization must be seen as a precondition for an optimal regeneration process. The revascularization process after different postoperative intervals is demonstrated in the sciatic nerve of rabbits by the use of microangiography, with Roentgen-positive water-soluble contrast medium. The third postoperative day is the earliest point in time for revascularization of the autologous graft from surrounding tissues. On the fourth postoperative day, a hyperemia with extension to all sides of the intraneural vessel system exists that still persists on the fifth and sixth days. In one experimental group, revascularization was allowed to occur only in a longitudinal direction. Revascularization under these conditions proved to be poor, slow, and obviously dependent on the length of the graft. Survival and subsequent function of free autologous nerve grafts may depend on the diameter of the grafts and the quality of the recipient site, but not on the length of the grafts, when timely revascularization from the surrounding tissues is present.     

Vascularization of skin following implantation of an arteriovenous pedicle: implications in flap prefabrication.

In a rat model, a skin flap was fabricated by implantation of a distally ligated arteriovenous pedicle. The femoral artery and vein were implanted as a unit beneath the abdominal skin, a portion of which was later raised as an island flap, based on these vessels. Percentage area of survival, tissue blood flow, and pattern of vascularity were compared in two groups of flaps. In group I, the pedicle to be implanted was dissected with a cuff of surrounding muscle still attached; in group II, the pedicle was skeletonized to the level of adventitia. Flap survival in the two groups was similar (73% vs. 77%), as was skin blood flow (5.4 vs. 5.7 ml/100 g/min). Angiography demonstrated two principal patterns of vascularization: connection between donor and recipient vessels (inoculation), and sprouting and arborization of new vessels. Strengths and limitations of this and other models of flap "prefabrication" are discussed.     

Comparative electrophysiologic evaluation of nerve grafts and autogenous vein grafts as nerve conduits: an experimental study

This study was carried out to compare electrophysiologically the efficacy of autogenous vein grafts, with autogenous nerve grafts as conduits for nerve regeneration. A 0.75-cm segment of sciatic nerve was resected in two groups of Sprague-Dawley rats of equivalent maturity. The nerve gaps were bridged with an autogenous vein graft in the first group (31 rats), and an autogenous nerve graft in the second group (24 rats). Serial in vivo nerve conduction velocity studies and terminal in vitro nerve conduction velocity and nerve action potential measurements were performed. An additional group of 21 animals who had undergone no surgical procedures, were similarly studied to establish an age-adjusted baseline for comparison. Twelve animals in the first group, 14 in the second group, and 13 in the baseline group survived the full year of study. In vivo conduction velocities between the two experimental groups compared favorably. Nerve conduction velocity determined by in vitro technique confirmed this finding and measured similarly at about 78 percent of the baseline. Nerve action potential amplitude in the vein-grafted group was 12.0 percent of the baseline, while the nerve-grafted group was 23.9 percent of the baseline. This study demonstrated that the vein graft compares well with the nerve graft in nerve conduction velocity, but only one-half as well in nerve action potential.     

Retrograde arterialized venous flap: an experimental study

An experimental model was established to study circulation in retrograde arterialized venous flaps (RAVF). Venous flaps measuring 7 x 4 cm with a matching venous system were harvested from both forearms of 10 fresh human cadavers. In each trial, both flaps were simultaneously perfused with heparinized human blood driven by a pulsatile circulation model. In each trial there was one flap with retrograde perfusion, and one flap with antegrade perfusion. Clinical assessment, measurement of outflow, and angiographic examination with digitally assisted assessment after 3 h of perfusion showed better results for retrograde perfusion in 8 of the 10 trials. This study indicates that blood circulation in the periphery of arterialized venous flaps can be enhanced by retrograde arterialization.     

Experimental study on axial pedicled composite flap prefabrication with high density porous polyethylene implants: medporocutaneous flap.

Composite flaps including soft tissues with bone or cartilage are widely used in reconstruction of three-dimensional defects, but have some disadvantages. Flap prefabrication with alloplastic implants is an alternative procedure. Axial pattern vascularised high density porous polyethylene (HDPP) implants are capable of sustaining skin grafts. The purpose of this study was to examine the vascularisation pattern of the skin island in a composite flap prefabrication model prepared with vascularised HDPP implants. Forty male Wistar rats divided into four groups were used. A 9.5 x 6 x 2 mm HDPP block was centered on the dissected saphenous pedicle and anchored under the abdominal skin in the experimental group I (n=10). In experimental group II (n=10) saphenous artery and vein were put between the skin and the implant. Thus, the structures were laid as skin, HDPP block, pedicle in experimental group I and skin, pedicle, HDPP block in experimental group II. HDPP block-implanted and pedicle-implanted only groups served as control groups I and II, respectively. Eight weeks after prefabrication, skin islands 1.5 x 5 cm in size incorporated with implants were elevated based on saphenous vessels in the experimental groups and skin islands only based on the pedicle in control group II. Skin islands of the same dimensions were raised as grafts in control group I. Nylon sheets were put under the flaps and grafts to prevent vascularisation from the recipient bed. Flap viability was assessed by measuring the surface area on the 7th day. Total necrosis developed in composite grafts of control group I. Flap survival was higher in experimental group II and control group II (45% and 46.8%) than in group I (29.28%). Histologic studies demonstrated fibrovascular ingrowth into the HDPP implants, except in control group I, with significant inflammatory response and necrosis. Vascularisation of skin and implants from the pedicle was seen also microangiographically. In conclusion, a composite flap prefabrication model including vascularised HDPP implant, skin and vascular carrier was developed. This new flap was termed a 'medporocutaneous flap'.     

Musculocutaneous grafts with draining vein: an experimental study

Venous drainage of a musculocutaneous graft was shown to be of importance for the prevention of necrosis and successful graft take. An experimental model was provided in which the iliolumbar veins were used as draining veins in creating musculocutaneous grafts 4 X 3 cm and 4 X 6 cm in size. In the study, it was demonstrated that necrosis could be prevented by preserving draining veins. The number and size of these veins were of some significance in the survival of the grafts.