Einheilung vaskularisierter Knochenallotransplantate

Background

Living bone allotransplants (ATs) currently require long-term immunosuppression (IS), but this is impractical for extremity-preserving procedures. An alternative method to maintain viability of the transplant uses host-derived neoangiogeneic vessels combined with short-term IS.

Materials and Methods

Diaphyseal femoral defects in Dutch-Belted rabbits were reconstructed with a free microvascular AT from New Zealand White rabbits. Additionally, a host-derived intramedullary pedicled fascial flap was placed and short-term IS administered to two of four groups. Neovascularization and bone healing were quantified by microangiography and a custom radiographic score.

Results

Bone ATs with perfused fascial flaps achieved bone healing equivalent to autotransplant controls, even when they received IS only until host-derived neoangiogenesis replaced the original perfusion. Vascularized ATs without this combination achieved significantly inferior results.

Summary

This rabbit model demonstrated that increased bone turnover allows good healing but may temporarily weaken the allotransplant. However, by the more intense replacement of the graft with host-derived cells, this process may, in the long-term, ultimately result in a better transplant than an avascular graft.     

Host-derived angiogenesis maintains bone blood flow after withdrawal of immunosuppression

A novel method of living bone allotransplantation combining microvascular repair of the nutrient circulation, implantation of host-derived arteriovenous (AV) bundles, and short-term immunosuppression is described. We hypothesized that neoangiogenesis from the implanted vessels would maintain graft viability and circulation after withdrawal of FK506 (Tacrolimus) immunosuppression. Vascularized femoral transplantation was performed between DA and PVG rats. In addition to microsurgical pedicle anastomoses, a saphenous AV bundle from the recipient animal was implanted in the medullary space. Ninety-seven rats were randomly allocated to groups differing in immunosuppression and AV bundle patency. Implanted vessels significantly improved capillary density and bone blood flow in nonimmunosuppressed and immmunosuppressed groups, respectively. A lower incidence of spontaneous AV bundle thrombosis was found with Tacrolimus treatment. More viable osteocytes were seen at 4 weeks when the AV bundle was patent. Further investigations may confirm host-derived neoangiogenesis as an alternative to tolerance induction or immunosuppression in bone allotransplantation.     

Short-term immunosuppression and surgical neoangiogenesis with host vessels maintains long-term viability of vascularized bone allografts.

Currently available methods to reconstruct large skeletal defects have limitations. These include nonunion and stress fractures in structural allografts, and inability to match the size, shape, and/or strength of most recipient sites using vascularized fibular autografts. Prosthetic diaphyseal replacements may loosen or produce periprosthetic fractures. Transplantation of living allogenic bone would enable matching donor bone to the recipient site, combined with the desirable healing and remodeling properties of living bone. We propose a novel method by which the transplantation of such tissue might be done without the risks of life-long immunosuppression, using surgical neoangiogenesis to develop a new host-derived osseous blood supply. We performed vascularized femoral allografts from 86 female Dark Agouti donor rats to male Piebald Virol Glaxo recipients across a major histocompatibility (MHC) barrier. In addition to microvascular reconstruction of the nutrient vessel, we surgically implanted a host arteriovenous (AV) bundle into the medullary canal to promote host vessel neoangiogenesis. Independent variables included patency of the implanted AV bundle, and use of 2 weeks' FK-506 immunosuppression. After 18 weeks, bone blood flow was measured, and neoangiogenic capillary density quantified. Bone blood flow and capillary density were significantly greater in transiently immunosuppressed recipients with a patent AV pedicle. We conclude that neoangiogenesis from implanted host-derived AV-bundles, combined with short-term immunosuppression maintains blood flow in vascularized bone allografts, and offers potential for clinical application.     

The superficial inferior epigastric artery fascia flap in the rabbit

In reconstructive surgery, fascial flaps provide thin, pliable tissue for mucosal closure or serve as a highly vascularized support for skin grafts. Their angiogenic potential is used for experimental neovascularization of avascular tissue grafts. However, most fascial flaps in animal surgery have random pattern design with short reach. As a pilot study for a femur revascularization project in rabbits, a new axial fascial flap is described based on the superficial inferior epigastric (SIE) vessels. They were used in this species previously only as ligated bundles or in fasciocutaneous flaps. The topographical anatomy of the SIE-vessels, lower abdominal fascia, and panniculus carnosus are outlined. The angiogenic capabilities are demonstrated microangiographically by abundant vessel formation in a femur allograft. Used in a pedicled fashion, this flap is an alternative to femoral and saphenous vessels for prefabrication or revascularization procedures in the lower abdomen, genital area, and thigh. Distant recipient sites seem possible with microsurgical transfer.     

Neo-Angiogenesis,Transplant Viability,and Molecular Analyses of Vascularized Bone Allotransplantation Surgery in a Large Animal Model

Vascularized composite allotransplantation of bone is a possible alternative treatment for large osseous defects but requires life-long immunosuppression. Surgical induction of autogenous neo-angiogenic circulation maintains transplant viability without this requirement, providing encouraging results in small animal models [1–3]. A preliminary feasibility study in a swine tibia model demonstrated similar findings [4, 5]. This study in swine tibial allotransplantation tests its applicability in a pre-clinical large animal model. Previously, we have demonstrated bone vascularized composite allotransplantation (VCA) survival was not the result of induction of tolerance nor an incompetent immune system [1]. Fourteen tibia vascularized bone allotransplants were microsurgically transplanted orthotopically to reconstruct size-matched tibial defects in Yucatan miniature swine. Two weeks of immunosuppression was used to maintain allotransplant pedicle patency during angiogenesis from a simultaneously implanted autogenous arteriovenous bundle. The implanted arteriovenous bundle was patent in group 1 and ligated in group 2 (a neo-angiogenesis control). At twenty weeks, we quantified the neo-angiogenesis and correlated it with transplant viability, bone remodeling, and gene expression. All patent arteriovenous bundles maintained patency throughout the survival period. Micro-angiographic, osteocyte cell count and bone remodeling parameters were significantly higher than controls due to the formation of a neo-angiogenic autogenous circulation. Analysis of gene expression found maintained osteoblastic and osteoclastic activity as well as a significant increase in expression of endothelial growth factor-like 6 (EGFL-6) in the patent arteriovenous bundle group. Vascularized composite allotransplants of swine tibia maintained viability and actively remodeled over 20 weeks when short-term immunosuppression is combined with simultaneous autogenous neo-angiogenesis. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:288-296, 2020     

Transplantation of a vascularized rabbit femoral diaphyseal segment: mechanical and histologic properties of a new living bone transplantation model

A new vascularized bone transplantation model is described, including the anatomy and surgical technique of isolating a rabbit femoral diaphyseal segment on its nutrient vascular pedicle. The histologic and biomechanical parameters of pedicled vascularized femoral autotransplants were studied following orthotopic reimplantation in the resulting mid-diaphyseal defect. Vascularized femur segments were isolated in 10 rabbits on their nutrient pedicle, and then replaced orthotopically with appropriate internal fixation. Postoperative weightbearing and mobility were unrestricted, and the contralateral femora served as no-treatment controls. After 16 weeks, the bone flaps were evaluated by x-ray (bone healing), mechanical testing (material properties), microangiography (quantification of intraosseous vasculature), histology (bone viability), and histomorphometry (bone remodeling). Bone healing occurred by 2 weeks, with further callus remodeling throughout the survival period. Eight transplants healed completely, while two had a distal pseudarthrosis. Microangiography demonstrated patent pedicles in all transplants. Intraosseous vessel densities were comparable to nonoperated (control) femora. We found ultimate strength and elastic modulus to be significantly reduced when compared to normal controls. Viable bone, increased mineral apposition rate, and bone turnover were demonstrated in all transplants. The method described, and the data provided will be of value for the further study of isolated segments of living bone, and in particular, for investigations of reconstruction of segmental bone loss in weight-bearing animal models. This study also provides important normative data on living autologous bone flap material properties, vascularity, and bone remodeling. We intend to use this method and data for comparison in subsequent studies of large bone vascularized allotransplantation.     

Vascularized bone grafts for upper limb reconstruction: defects at the distal radius, wrist, and hand

Vascularized bone grafts have been successfully applied for the reconstruction of bone defects at the forearm, distal radius, carpus, and hand. Vascularized bone grafts are most commonly used in revision cases in which other approaches have failed. Vascularized bone grafts can be obtained from a variety of donor sites, including the fibula, the iliac crest, the distal radius (corticocancellous segments and vascularized periosteum), the metacarpals and metatarsals, and the medial femoral condyle (corticoperiosteal flaps). Their vascularity is preserved as either pedicled autografts or free flaps to carry the optimum biological potential to enhance union. The grafts can also be transferred as composite tissue flaps to reconstruct compound tissue defects. Selection of the most appropriate donor flap site is multifactorial. Considerations include size matching between donor and defect, the structural characteristics of the graft, the mechanical demands of the defect, proximity to the donor area, the need for an anastomosis, the duration of the procedure, and the donor site morbidity. This article focuses on defects of the distal radius, the wrist, and the hand.     

Fibroblast growth factor‐2 and vascular endothelial growth factor mediated augmentation of angiogenesis and bone formation in vascularized bone allotransplants

We previously demonstrated recipient‐derived neoangiogenesis to maintain viability of living bone allogeneic transplants without long‐term immunosuppression. The effect of cytokine delivery to enhance this process is studied. Vascularized femur transplantation was performed from Dark Agouti to Piebald Virol Glaxo rats. Poly(d,l ‐lactide‐co‐glycolide) microspheres loaded with buffer (N = 11), basic fibroblast growth factor (FGF2) (N = 10), vascular endothelial growth factor (VEGF) (N = 11), or both (N = 11) were inserted intramedullarly alongside a recipient‐derived arteriovenous bundle. FK‐506 was administered for 2 weeks. At 18 weeks, bone blood flow, microangiography, histologic, histomorphometric, and alkaline phosphatase measurements were performed. Bone blood flow was greater in the combined group than control and VEGF groups (P = 0.04). Capillary density was greater in the FGF2 group than in the VEGF and combined groups (P < 0.05). Bone viability, growth, and alkaline phosphatase activity did not vary significantly between groups. Neoangiogenesis in vascularized bone allotransplants is enhanced by angiogenic cytokine delivery, with results using FGF2 that are comparable to isotransplant from previous studies. Further studies are needed to achieve bone formation similar to isotransplants. © 2014 Wiley Periodicals, Inc. Microsurgery 34:301–307, 2014.     

Autogenous Arteriovenous Bundle Implantation Maintains Viability Without Increased Immune Response in Large Porcine Bone Allotransplants

BackgroundTransplantation of living allogeneic bone segments may permit reconstruction of large defects, particularly if viability is maintained without immunosuppression. Development of a new autogenous osseous blood supply accomplishes this goal in rodent experimental models. This study evaluates potential systemic and local inflammatory responses to this angiogenesis in a large-animal model.MethodsVascularized allogeneic tibia segments were transplanted orthotopically into matched tibial defects in Yucatan minipigs. Microvascular anastomoses of bone nutrient artery and vein were supplemented by intramedullary placement of an autogenous arteriovenous (AV) bundle in group 1. Group 2 served as a no-angiogenesis control. A 3-drug immunosuppression regimen was withdrawn after 2 weeks. During the 20-week survival period, periodic leukocyte counts and inflammatory cytokine levels were measured. Thereafter, osteocyte survival was quantified and transplant rejection graded by histologic examination and quantitative real-time polymerase chain reaction of immunologic markers.ResultsBoth groups developed an initial systemic response, which resolved after 4 to 6 weeks. No differences were seen in blood cytokine levels. Interleukin 2 expression was diminished in group 1 tibiae. As expected, nutrient pedicles had thrombosed without sustained immunosuppression, occluded by intimal hyperplasia. In group 1, angiogenesis from the autogenous AV bundle resulted in significantly less osteonecrosis (P = .04) and fibrosis (P = .02) than group 2 allotransplants.ConclusionsSystemic immune responses to large-bone allotransplants were not increased by generation of an autogenous osseous blood supply within porcine tibial bone allotransplants. Implanted AV bundles diminished inflammation and fibrosis and improved bone viability when compared to no-angiogenesis controls.     

指背神经筋膜蒂逆行皮瓣蒂部不同处理修复指端缺损

目的探讨指背神经筋膜蒂逆行皮瓣蒂部不同处理修复指端缺损的临床疗效。方法对39例39指指端皮肤软组织缺损患者,设计指背神经筋膜蒂皮瓣逆行转移修复皮肤缺损,术中根据皮瓣血运情况,采用不同的蒂部处理方法转移皮瓣。蒂部创面直接缝合8例。蒂部带皮蒂10例,蒂部创面全厚皮片植皮21例．其中包括蒂部创面直接缝合及带皮蒂皮瓣发生血运障碍后,采用蒂部皮片植皮分别为4例和5例。结果39例皮瓣均成活。4例皮瓣其中蒂部创面直接闭合2例,蒂部单纯带皮蒂2例,术后发生静脉危象,明显肿胀并出现水疱,经抽吸水疱减张及小切口放血后皮瓣转为红润。术后随访5～8个月,皮瓣外形、手指功能均较满意。结论根据术中皮瓣血运情况．采用不同蒂部处理方式的指背神经筋膜蒂逆行皮瓣修复指端缺损．能明显降低皮瓣肿胀及血管危象的发生。     

逆行腓浅血管筋膜蒂皮瓣修复小腿中下段软组织缺损

目的探讨采用逆行腓浅血管筋膜蒂皮瓣修复小腿中下段软组织缺损的临床效果。方法对10例小腿中下段软组织缺损患者(缺损面积5 mm×3 cm~8 cm×6 cm)采用逆行腓浅血管筋膜蒂皮瓣移位治疗。结果术后皮瓣完全成活。患者均获随访,时间3周~2年,皮瓣外形满意,质地良好。结论逆行腓浅血管筋膜蒂皮瓣血供可靠,切取方便,不牺牲主干血管,基本可满足小腿中下段创伤修复的需要,临床疗效满意。     

Repopulation of vascularized bone allotransplants with recipient‐derived cells: Detection by laser capture microdissection and real‐time PCR

Mechanisms underlying successful composite tissue transplantation must include an analysis of transplant chimerism, which is little studied, particularly in calcified tissue. We have developed a new method enabling determination of lineage of selected cells in our model of vascularized bone allotransplantation. Vascularized femoral allotransplantation was performed from female Dark Agouti (DA) donor rats to male Piebald Virol Glaxo (PVG) recipients, representing a major histocompatibility mismatch. Four groups differed in use of immunosuppression (±2 weeks Tacrolimus) and surgical revascularization, by implantation of either a patent or a ligated saphenous arteriovenous (AV) bundle. Results were assessed at 18 weeks. Bone blood flow was measured by the hydrogen washout technique and transverse specimens were prepared for histology. Real‐time PCR was performed on DNA from laser capture microdissected cortical bone regions to determine the extent of chimerism. To do so, we analyzed the relative expression ratio of the sex‐determining region Y (Sry) gene, specific only for recipient male rat DNA, to the cyclophilin housekeeper gene. Substantial transplant chimerism was seen in cortical bone of all groups (range 77–97%). Rats without immunosuppression and with a patent AV bundle revealed significantly higher chimerism than those with immunosuppression and a ligated AV bundle, which maintained transplant cell viability. We describe a new method to study the extent of chimerism in rat vascularized bone allotransplants, including a sex‐mismatched transplantation model, laser capture microdissection of selected bone regions, and calculation of the relative expression ratio. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:1514–1520, 2009     

Transplant options for patients undergoing total pancreatectomy for chronic pancreatitis

BACKGROUND: Total pancreatectomy to treat chronic pancreatitis is associated with severe diabetic control problems in 15% to 75% of patients, causing up to 50% of deaths late postoperatively. We report our experience with islet autotransplants at the time of, or with pancreas allotransplants after, total pancreatectomy. STUDY DESIGN: Between February 1, 1977, and June 30, 2003, we performed 112 islet autotransplants at the time of total pancreatectomy; we also performed 20 pancreas allotransplants in 13 patients who had already undergone total pancreatectomy months to years earlier. RESULTS: Islet autotransplants at the time of total pancreatectomy in patients who had not had previous operations on the body and tail of the pancreas were associated with a high islet yield (>2,500 islet equivalents/kg body weight), and >70% of the recipients achieved complete insulin independence. In contrast, a previous distal pancreatectomy or a Puestow drainage procedure was associated with a low islet yield in 75% of them and with complete insulin independence in <20%. A pancreas allotransplant after total pancreatectomy was not associated with any transplant-related mortality at 1 and 3 years posttransplant. The pancreas graft survival rate at 1 year posttransplant was 77% with tacrolimus-based immunosuppression (versus 67% with cyclosporine). Enteric (over bladder) drainage was preferred to manage exocrine graft secretions, to cure pancreatectomy-induced endocrine and exocrine insufficiency. CONCLUSIONS: Our series shows that pancreas allotransplants can be performed without transplant-related mortality and, when tacrolimus-based immunosuppression is used, with 1-year pancreas graft survival rates >75%. In contrast to a simultaneous islet autotransplant, a pancreas allotransplant has the disadvantage of requiring lifelong immunosuppression, but the advantage of not only curing endocrine but also exocrine insufficiency. Both transplant options, if successful, improve the recipient's quality of life.     

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.     

腓浅动脉岛状筋膜蒂皮瓣在小腿皮肤缺损中的应用

目的探讨采用腓浅动脉岛状筋膜蒂皮瓣治疗小腿皮肤缺损的临床效果。方法对31例膝关节至足踝部皮肤缺损患者采用腓浅动脉岛状筋膜蒂皮瓣移位治疗。结果随访31例，时间3周-5年。27例皮瓣完全成活，4例皮瓣远端部分坏死。结论采用腓浅动脉岛状筋膜蒂皮瓣治疗小腿皮肤缺损，该皮瓣血供可靠，切取方便，不牺牲主干血管，基本可满足小腿前外侧创伤修复的需要。     

血管内皮祖细胞和血管内皮生长因子促进预构皮瓣血管新生作用的比较

目的 比较血管内皮祖细胞(endothelial progenitor cells,EPCs)与血管内皮生长因子(vascular endothelial growth factor,VEGF)在促进预构皮瓣血管新生作用上的差异,探讨EPCs移植提高预构皮瓣存活面积的可行性.方法 分离雄性Wistar大鼠(45只)一侧股血管柬,转位植入腹部皮下,建立预构皮瓣实验模型.将体外诱导分化的EPCs(组Ⅰ,n=15)和VEGF(组Ⅱ,n=15)分别注射于皮瓣局部,对照组仅注射PBS溶液(组Ⅲ,n=15).4周后形成以植入血管为蒂的岛状皮瓣,原位缝合;术后7 d对皮瓣存活率、血管密度计数进行检测.结果 组Ⅰ、组Ⅱ、组Ⅲ的皮瓣存活率分别为(87.26±10.13)%、(66.13±9.9)%、(55.59±13.06)%,组Ⅰ分别与组Ⅱ和组Ⅲ比较,差异均有统计学意义(P<0.001);微血管密度分别为:(38.67±9.52)个/mm~2、(25.83±6.33)个/mm~2、(26.5±5.61)个/mm~2(P<0.05).结论 EPCs促进预构皮瓣血管新生的作用优于VEGF,局部应用骨髓来源的EPCs可以有效地提高预构皮瓣存活面积.     

A modified vascularized whole knee joint allotransplantation model in the rat

Previous papers have shown surgical neoangiogenesis to allow long‐term bone allotransplant survival without immunosuppression. Whole joint composite tissue allotransplants (CTA) might be treated similarly. A novel rat knee CTA model is described for further study of the roles of neoangiogensis in joint allotransplant survival and adjustment of immunosuppression. Microvascular knee CTA was performed in nine rats across a major histocompatibility barrier with both pedicle repair and implantation of host‐derived arteriovenous (“a/v”) bundles. In the control group (N = 3), the pedicle was ligated. Immunosuppression was given daily. Joint mobility, weight‐bearing, pedicle patency, bone blood flow, and sprouting from a/v bundles were assessed at 3 weeks. All but the nonrevascularized control knees had full passive motion and full weight bearing. One nutrient pedicle thrombosed prematurely. Blood flow was measurable in transplants with patent nutrient pedicles. Implanted a/v bundles produced new vascular networks on angiography. This new rat microsurgical model permits further study of joint allotransplantation. Patency of both pedicles and implanted a/v bundles was maintained, laying a foundation for future studies. © 2010 Wiley‐Liss, Inc. Microsurgery, 2010.     

Surgical angiogenesis: a new approach to maintain osseous viability in xenotransplantation

Chung Y‐G, Bishop AT, Giessler GA, Suzuki O, Platt JL, Pelzer M, Friedrich PF, Kremer T. Surgical angiogenesis: a new approach to maintain osseous viability in xenotransplantation. Xenotransplantation 2010; 17: 38–47. © 2010 John Wiley & Sons A/S. Abstract: Background: Large segmental osseous defects are challenging clinical problems. Current reconstructive methods, using non‐viable allografts, vascularized autografts or prostheses have significant rates of serious complications and failure. These include infection, stress fracture and non‐union (frozen structural allogenic bone); loosening and implant failure (prosthetic replacement); limited availability, poor match of size and shape and donor site morbidity (vascularized autograft bone). In the future, microvascular transplantation of living allogenic or xenogenic bone could solve some of these issues, combining the advantages of living bone autografts (capability of primary osseous healing, remodeling, and fracture resistance) with the ability to match size and shape, provide immediate stability and avoid donor site morbidity. Xenotransplants would be particularly attractive, as they could be readily available, if long‐term bone survival could be achieved without unacceptable morbidity. Here, we present a preliminary study to evaluate a new and unique method to maintain xenogenic bone circulation without need for long‐term immune modulation that depends upon generation of a neo‐angiogenic circulation within the transplanted bone from recipient‐derived vessels. Thus, only short‐term immunosuppression would be required to achieve bone survival. Methods: One hundred and forty‐one hamster femora were microsurgically transplanted to rats, restoring nutrient vessel circulation with standard microvascular anastomoses. At the same time, a host‐derived arteriovenous bundle (AVB) was placed within the medullary canal. Two independent variables were evaluated: use of tacrolimus/cyclophosmamid immunosuppression (IS) and patency of the implanted AVB. Rats were therefore randomized to four groups; group 1—no IS + patent AVB; group 2—no IS + ligated AVB; group 3—IS + patent AVB; group 4—IS + ligated AVB. Rats were sacrificed after 1 or 2 weeks. We evaluated bone blood flow (microsphere entrapment), neoangiogenesis (microangiography and quantification of capillary density), bone necrosis rate (osteocyte counts) and nutrient pedicle rejection (microsurgical anastomotic patency). Statistical Analysis was performed with two‐way ANOVA with Bonferroni adjustment. Differences were considered significant when P < 0.05. Results: Capillary density was significantly increased with a patent intramedullary AVB (groups 1/3) compared to groups with ligated AVBs (groups 3/4). Capillary sprouting was predominantly restricted to the endosteal layer. Most nutrient pedicles (78.7%) stayed patent in groups with IS (groups 3 and 4). Consequently, bone blood flow was significanty higher in groups 3 and 4 compared to groups 1 and 2. Similary, a patent AV bundle improved flow in group 1 when compared to group 2. The bone necrosis rate was not influenced by the presence of patent AVBs but was significantly reduced in groups 3 and 4. Conclusions: Surgical angiogenesis occurs when patent arteriovenous bundles are placed in the medullary canal of xenogenic bone and leads to increased bone blood flow. Bone viability was not significantly influenced by neoangiogenesis. Although capillary sprouting was restricted to the endosteal layer in this short term study, more complete cortical revascularization might be observed in a long‐term study. Such a study should further evaluate whether these new vessels supply sufficient blood flow to maintain long‐term bone viability and allow remodeling.     

Histological and immunohistochemical study of the bronchial stump with flap coverage in an animal model

OBJECTIVE: The purpose of our study was to evaluate the healing process of the bronchial stump after pneumonectomy reinforced with different pedicled flaps in an animal model. The specimens were analyzed by means of histology and immunohistochemistry. MATERIALS AND METHODS: We have considered 45 New Zealand White male rabbits that underwent a left pneumonectomy under general anesthesia. Nine animals had no bronchial coverage and represented the controls. The other 36 rabbits were divided into three groups of 12 and had bronchial coverage with either diaphragmatic, intercostal or pericardial flaps. The histological examinations were performed on the animals sacrificed 7, 14 and 30 days after surgery. Immunohistochemical analyses were done on the specimens on postoperative day 7 and 14. On postoperative day 7, the specimens were examined for expression of proliferating cell nuclear antibody (PCNA) expression. On postoperative day 14, neoangiogenesis was measured by CD31 expression. The measurements of antibody expression were done with a computer-assisted morphometric count and analyzed with the t test. RESULTS: On postoperative day 14, standard histology showed more evident neoangiogenesis in the bronchial stump specimens covered with intercostal and diaphragmatic flaps compared to pericardial flaps and controls. The immunohistochemical evaluation of PCNA by morphometric computer-assisted analysis did not show any statistically significant differences among the groups. The CD31 morphometric count revealed a higher and statistically significant antibody expression in muscular flaps compared to pericardial flaps and controls. CONCLUSIONS: Our study showed that bronchial coverage with a pedicled muscular flaps promotes the production of new vessels and gives the possibilities to optimize the healing process of a bronchial stump after pneumonectomy.     

Restoration of facial contour in Romberg's disease and hemifacial microsomia: experience with 118 cases

The experience with free flaps and conventional reconstructive procedures for 118 patients with Rombergapos;s disease and hemifacial microsomia over a 10-year period is presented. The groin free flap was used most frequently for patients with Rombergapos;s disease, whereas the scapular free flap was used for patients with hemifacial microsomia. The rectus abdominis or the latissimus dorsi free flap was chosen only when additional volume was required. To achieve better contour, secondary procedures, such as defatting the flap, pedicled temporal fascial flaps, cartilage and bone grafts, orthognathic surgery, and bone distraction were performed in severe cases. For patients with Rombergapos;s disease, excellent results were achieved in 35% (n = 28) of mild cases, in 72% (n = 27) out of 38 moderately and in 41% (n = 5) out of 12 severely affected patients. In hemifacial microsomia group (n = 40) excellent results were obtained in 66% of cases.