Developing an International Framework for Informed Consent in Plastic Surgery: A Focus on Cosmetic Breast Augmentation.

Background: Informed consent is a fundamental pillar of patient rights and is an essential part of good clinical practice. In 2019, the International Confederation of Plastic Surgery Societies launched a survey to collect feedback on informed consent practices, with an aim to develop an international guideline for cosmetic surgery. Methods: A 15-question survey was sent to delegates of the International Confederation of Plastic Surgery Societies for dissemination to their national society members. The survey comprised a range of quantitative and qualitative questions. Descriptive and thematic analysis was performed. Results: There were 364 respondents. Over half of the respondents reported no local informed consent policy, whereas others noted national society, specialist college, or government policies. The majority of respondents believed that the performing surgeon should be responsible for obtaining informed consent with at least two face-to-face consultations. Most respondents agreed with a cooling-off period (duration based on procedure type and use of high-risk devices). Regarding cosmetic breast augmentation, the majority of respondents felt that the performing surgeon should be responsible for postoperative management, including cases that occur as part of surgical tourism. Some respondents incorporate financial consent as part of their informed consent practice. Most supported the development of an international informed consent guideline. Conclusions: Informed consent should result from face-to-face consultations with the performing surgeon. There should be a minimum cooling-off period. Postoperative surveillance should be available in all settings. The findings of this survey will help inform an international standardized informed consent guideline for cosmetic surgery.

BREAST trial study protocol: evaluation of a non-invasive technique for breast reconstruction in a multicentre, randomised controlled trial.

INTRODUCTION: Pioneers have shown that it is possible to reconstruct a full breast using just autologous fat harvested by liposuction or autologous fat transfer (AFT). This study describes the first multicentre randomised study protocol to thoroughly investigate the effectiveness of AFT to reconstruct full breasts following mastectomy procedures (primarily and delayed). METHODS AND ANALYSIS: This study is designed as a multicentre, randomised controlled clinical superiority trial with a 1:1 allocation ratio. A total of 196 patients (98 patients per treatment arm) are aimed to be included. Patients who wish to undergo breast reconstruction with either one of the two techniques are randomly allocated into the AFT group (intervention) or the tissue-expander/prosthesis group (control). The primary outcome measure for the quality of life is measured by the validated BREAST-Q questionnaire. ETHICS AND DISSEMINATION: Approval for this study was obtained from the medical ethics committee of Maastricht University Medical Centre/Maastricht University; the trial has been registered at ClinicalTrials.gov. The results of this randomised controlled trial will be presented at scientific meetings as abstracts for poster or oral presentations and published in peer-reviewed journals. TRIAL STATUS: Enrolment into the trial has started in October 2015. Data collection and data analysis are expected to be completed in December 2021. TRIAL REGISTRATION NUMBER: NCT02339779.

Vascularized bone transplant chimerism mediated by vascular endothelial growth factor.

BACKGROUND: Vascular endothelial growth factor (VEGF) induces angiogenesis and osteogenesis in bone allotransplants. We aim to determine whether bone remodeling in VEGF-treated bone allotransplants results from repopulation with circulation-derived autogenous cells or survival of allogenic transplant-derived cells. METHODS: Vascularized femoral bone transplants were transplanted from female Dark Agouti rats (DA;RT1(a) ) to male Piebald Viral Glaxo (PVG;RT1(c) ). Arteriovenous bundle implantation and short-term immunosuppression were used to maintain cellular viability. VEGF was encapsulated in biodegradable microspheres and delivered intramedullary in the experimental group (n = 22). In the control group (n = 22), no VEGF was delivered. Rats were sacrificed at 4 or 18 weeks. Laser capture microdissection of bone remodeling areas was performed at the inner and outer cortex. Sex-mismatched genes were quantified with reverse transcription-polymerase chain reaction to determine the amount of male cells to total cells, defined as the relative expression ratio (rER). RESULTS: At 4 weeks, rER was significantly higher at the inner cortex in VEGF-treated transplants as compared to untreated transplants (0.622 ± 0.225 vs. 0.362 ± 0.081, P = 0.043). At 4 weeks, the outer cortex in the control group had a significantly higher rER (P = 0.038), whereas in the VEGF group, the inner cortex had a higher rER (P = 0.015). Over time, in the outer cortex the rER significantly increased to 0.634 ± 0.106 at 18 weeks in VEGF-treated rats (P = 0.049). At 18 weeks, the rER was >0.5 at all cortical areas in both groups. CONCLUSIONS: These in vivo findings suggest a chemotactic effect of intramedullary applied VEGF on recipient-derived bone and could imply that more rapid angiogenesis of vascularized allotransplants can be established with microencapsulated VEGF.

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.

Harvesting free abdominal perforator flaps in the presence of previous upper abdominal scars.

PURPOSE: Subcostal scars pose a risk of upper abdominal flap ischaemia when raising a free abdominal flap. The aim of this study was to describe a clinical approach to increase flap reliability and donor site healing in the presence of transverse abdominal scars while harvesting lower abdominal free flaps. METHODS: A total of 11 patients who had subcostal scars and one who had an extended subcostal scar (rooftop or chevron incision) underwent free abdominal flaps for breast reconstruction. Preoperative radiological imaging was used to evaluate the blood supply to the planned flaps. A classification of clinical approaches (I-IV) was used. When the cranial (the abdominal closure) flap width was equal to or greater than half length, a caudal (the breast) flap could safely be harvested (Type I); if not, the cranial flap was enlarged by more caudal flap planning (Type II), an oblique design of the free flap (Type III) or by lowering the free flap marking more distally (Type IV) with a sparing of the peri-umbilical perforators to preserve blood supply to the caudal (abdominal closure) flap. RESULTS: Unilateral free deep inferior epigastric perforator (DIEP) and superficial inferior epigastric artery (SIEA) flaps were successfully harvested in eight and two cases, respectively. In two cases, a bipedicled DIEP/SIEA flap was harvested for unilateral breast reconstruction. Slight abdominal wound slough occurred in one patient; however, no ischaemia resulted in flaps or at donor sites. CONCLUSIONS: Using a pragmatic approach to flap design, based on clinical classification, we have found that both flap and donor site morbidity can be avoided in patients who have previous upper abdominal scars. LEVEL OF EVIDENCE: IV, Therapeutic.

Cell lineage in vascularized bone transplantation.

BACKGROUND: The biology behind vascularized bone allotransplantation remains largely unknown. We aim to study cell traffic between donor and recipient following bone auto-, and allografting. METHODS: Vascularized femoral transplantation was performed with arteriovenous bundle implantation and short-term immunosuppression. Twenty male Piebald Virol Glaxo (PVG; RT1(c) ) rats received isotransplants from female PVG (RT1(c) ) rats and 22 male PVG rats received allografts from female Dark Agouti rats (DA, RT1(a) ), representing a major histocompatibility mismatch. Both groups were randomly analyzed at 4 or 18 weeks. Bone remodeling areas (inner and outer cortical samples) were labeled and laser capture microdissected. Analysis of sex-mismatch genes by real-time reverse transcription-polymerase chain reaction provided the relative Expression Ratio (rER) of donor (female) to recipient (male) cells. RESULTS: The rER was 0.456 ± 0.266 at 4 weeks and 0.749 ± 0.387 at 18 weeks (p = 0.09) in allotransplants. In isotransplants, the rER was 0.412 ± 0.239 and 0.467 ± 0.252 at 4 and 18 weeks, respectively (p = 0.21). At 4 weeks, the rER at the outer cortical area of isotransplants was significantly lower in isotransplants as compared with allotransplants (0.247 ± 0.181 vs. 0.549 ± 0.184, p = 0.007). Cells in the inner and outer cortical bone remodeling areas in isotransplants were mainly donor derived (rER < 0.5) at 18 weeks, whereas allotransplants contained mainly recipient-derived cells (rER > 0.5) at 18 weeks. CONCLUSIONS: Applying novel methodology, we describe detailed cell traffic in vascularized bone transplants, elaborating our comprehension on bone transplantation.

Induction of angiogenesis and osteogenesis in surgically revascularized frozen bone allografts by sustained delivery of FGF-2 and VEGF.

Large conventional bone allografts are susceptible to fracture and nonunion due to incomplete revascularization and insufficient bone remodeling. We aim to improve bone blood flow and bone remodeling using surgical angiogenesis combined with delivery of fibroblast growth factor (FGF-2) and vascular endothelial growth factor (VEGF). Frozen femoral allografts were heterotopically transplanted in a rat model. The saphenous arteriovenous bundle was implanted within the graft medullary canal. Simultaneously, biodegradable microspheres containing phosphate buffered saline (control), FGF-2, VEGF, or FGF-2 + VEGF were placed within the graft. Rats were sacrificed at 4 and 18 weeks. Angiogenesis was determined by quantifying bone capillary density and measuring cortical bone blood flow. Bone remodeling was assessed by histology, histomorphometry, and alkaline phosphatase activity. VEGF significantly increased angiogenesis and bone remodeling at 4 and 18 weeks. FGF-2 did not elicit a strong angiogenic or osteogenic response. No synergistic effect of FGF-2 + VEGF was observed. VEGF delivered in microspheres had superior long-term effect on angiogenesis and osteogenesis in surgically revascularized frozen bone structural allografts as compared to FGF-2 or FGF-2 + VEGF. Continuous and localized delivery of VEGF by microencapsulation has promising clinical potential by inducing a durable angiogenic and osteogenic response in frozen allografts.

Revascularization and bone remodeling of frozen allografts stimulated by intramedullary sustained delivery of FGF-2 and VEGF.

Frozen bone allografts are susceptible to nonunion and fracture due to limited revascularization and incomplete bone remodeling. We aim to revascularize bone allografts by combining angiogenesis from implanted arteriovenous (AV) bundles with delivery of fibroblast growth factor (FGF-2) and/or vascular endothelial growth factor (VEGF) via biodegradable microspheres. Rat femoral diaphyseal allografts were frozen at -80°C, and heterotopically transplanted over a major histocompatibility mismatch. A saphenous AV bundle was inserted into the intramedullary canal. Growth factor was encapsulated into microspheres and inserted into the graft, providing localized and sustained drug release. Forty rats were included in four groups: (I) phosphate-buffered saline, (II) FGF-2, (III) VEGF, and (IV) FGF-2 + VEGF. At 4 weeks, angiogenesis was measured by the hydrogen washout method and microangiography. Bone remodeling was evaluated by quantitative histomorphometry and histology. Bone blood flow was significantly higher in groups III and IV compared to control (p < 0.05). Similarly, bone remodeling was higher in VEGF groups. FGF-2 had little effect on allograft revascularization. No synergistic effect was observed with use of both cytokines. Delivered in microspheres, VEGF proved to be a potent angiogenic cytokine, increasing cortical bone blood flow and new bone formation in frozen allografts revascularized with an implanted AV bundle.

Living bone allotransplants survive by surgical angiogenesis alone: development of a novel method of composite tissue allotransplantation.

BACKGROUND: Segmental bone defects pose reconstructive challenges. Composite tissue allotransplantation offers a potential solution but requires long-term immunosuppression with attendant health risks. This study demonstrates a novel method of composite-tissue allotransplantation, permitting long-term drug-free survival, with use of therapeutic angiogenesis of autogenous vessels to maintain circulation. METHODS: Ninety-three rats underwent femoral allotransplantation, isotransplantation, or allografting. Group-1 femora were transplanted across a major histocompatibility complex barrier, with microsurgical pedicle anastomoses. The contralateral saphenous artery and vein (termed the AV bundle) of the recipient animal were implanted within the medullary canal to allow development of an autogenous circulation. In Group 2, allotransplantation was also performed, but with AV bundle ligation. Group 3 bones were frozen allografts rather than composite-tissue allotransplantation femora, and Group 4 bones were isotransplants. Paired comparison allowed evaluation of AV bundle effect, bone allogenicity (isogeneic or allogeneic), and initial circulation and viability (allotransplant versus allograft). Two weeks of immunosuppression therapy maintained blood flow initially, during development of a neoangiogenic autogenous blood supply from the AV bundle in patent groups. At eighteen weeks, skin grafts from donor, recipient, and third-party rats were tested for immunocompetence and donor-specific tolerance. At twenty-one weeks, bone circulation was quantified and new bone formation was measured. RESULTS: Final circulatory status depended on both the initial viability of the graft and the successful development of neoangiogenic circulation. Median cortical blood flow was highest in Group 1 (4.6 mL/min/100 g), intermediate in Group 4 isotransplants (0.4 mL/min/100 g), and absent in others. Capillary proliferation and new bone formation were generally highest in allotransplants (15.0%, 6.4 µm³/µm²/yr) and isotransplants with patent AV bundles (16.6%, 50.3 µm³/µm²/yr) and less in allotransplants with ligated AV bundles (4.4%, 0.0 µm³/µm²/yr) or allografts (8.1%, 24.1 µm³/µm²/yr). Donor and third-party-type skin grafts were rejected, indicating immunocompetence without donor-specific tolerance. CONCLUSIONS: In the rat model, microvascular allogeneic bone transplantation in combination with short-term immunosuppression and AV bundle implantation creates an autogenous neoangiogenic circulation, permitting long-term allotransplant survival with measurable blood flow.

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.

Augmentation of surgical angiogenesis in vascularized bone allotransplants with host-derived a/v bundle implantation, fibroblast growth factor-2, and vascular endothelial growth factor administration.

We have previously shown experimental transplantation of living allogeneic bone to be feasible without long-term immunosuppression by development of a recipient-derived neoangiogenic circulation within bone. In this study, we examine the role of angiogenic cytokine delivery with biodegradable microspheres to enhance this process. Microsurgical femoral allotransplantation was performed from Dark Agouti to Piebald Virol Glaxo rats. Poly(D,L-lactide-co-glycolide) microspheres loaded with buffer, basic fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF), or both, were inserted intramedullarly along with a recipient-derived arteriovenous (a/v) bundle. FK-506 was administered daily for 14 days, then discontinued. At 28 days, bone blood flow was measured using hydrogen washout. Microangiography, histologic, and histomorphometric analyses were performed. Capillary density was greater in the FGF+VEGF group (35.1%) than control (13.9%) (p < 0.05), and a linear trend was found from control, FGF, VEGF, to FGF+VEGF (p < 0.005). Bone formation rates were greater with VEGF (p < 0.01) and FGF+VEGF (p < 0.05). VEGF or FGF alone increased blood flow more than when combined. Histology rejection grading was low in all grafts. Local administration of vascular and fibroblast growth factors augments angiogenesis, bone formation, and bone blood flow from implanted blood vessels of donor origin in vascularized bone allografts after removal of immunosuppression.

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.

Measurement of bone blood flow using the hydrogen washout technique-part II: Validation by comparison to microsphere entrapment.

Accurate and reproducible measurement of bone blood flow has important clinical and experimental applications. Hydrogen washout is simple, safe, and widely used, but its use in bone tissue has not been validated. To this end, we have compared cortical bone blood flow measurements obtained by radioactive-labeled microsphere entrapment with those from hydrogen washout. Blood flow was measured in tibial cortical bone of 12 New Zealand White rabbits by radioactive microsphere entrapment and by hydrogen washout. Besides a control group (n = 6), four animals were treated with systemic epinephrine (0.8 microg/kg/min) (group 2) and two with nitroprusside (100 microg/kg/min) (group 3). Furthermore, nine femora from seven rats were isolated on their vascular pedicles and repeated bone blood flow measurements were made at each location with the hydrogen washout method to confirm reproducibility of blood flow determinations by hydrogen washout. An average flow of 2.3 +/- 2.0 mL/min/100 g was obtained with the microsphere method and 2.0 +/- 0.5 mL/min/100 g with the hydrogen washout method. There was a significant correlation and agreement: R(2) = 0.97 (p < 0.01). No consistent flow variations were found with systemic vasoactive drug administration. Hydrogen washout provided reproducible results and showed high sensitivity to flow changes. Hydrogen washout is both sensitive and reproducible in measuring bone blood flow. Results agree well with flow values obtained by labeled microsphere entrapment.

Measurement of bone blood flow using the hydrogen washout Technique-Part I: quantitative evaluation of tissue perfusion in the laboratory rat.

The measurement of blood flow in bone is of interest in both clinical and experimental settings. Such determinations would ideally provide accurate, quantitative, and reproducible data with relatively simple and safe technology, even in the small bones of experimental animals. Methods that provide absolute or quantitative measurements include positron emission tomography, "isotope fractioning" using radioactive or fluorescent-labeled microspheres, and measurement of the rate of washout of diffusible tracers delivered either by injection or inhalation. In this article, we describe in detail a modification of the original Whiteside hydrogen washout technique, using modern hydrogen sensors, a micromanipulator for probe placement, and custom software that greatly simplifies blood flow determination and is effective in the small bones of experimental animals.

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.

An anatomic study of the spinal accessory nerve: extended harvest permits direct nerve transfer to distal plexus targets.

An anatomic study of the distal spinal accessory nerve (SAN) to determine the number of myelinated axons and feasibility of posterior harvest for direct neurotization of distal targets was performed. Ten fresh human cadavers were studied. A supraclavicular approach was performed followed by a posterior approach. The relationship of the SAN to bony landmarks (T1 spinous process, acromioclavicular joint, posterolateral corner of the acromium, and angle at the superior medial border of the scapula) as well as maximal harvestable length was recorded. After posterior dissection, the SAN was mobilized and the ability to reach both anterior infraclavicular and posterior targets was assessed. Axon counts were also performed at the proximal, mid, and distal points along the course of the nerve. The posteriorly harvested SAN was identified reliably with respect to bony landmarks. When harvested posteriorly, the SAN could reach the infraclavicular part of the brachial plexus (i.e., terminal branches), and posteriorly, the suprascapular nerve (SSN) both proximal and distal to the suprascapular ligament, the latter for selective reinnervation of the infraspinatus branch. The average number of myelinated fibers at the proximal end of the nerve was 1,328 axons, at the mid-way point was 1,021 axons, and at terminal end of the nerve was 817 axons. Harvest of the SAN from a posterior approach based on these landmarks is feasible, allowing direct transfer of the nerve to the infraclavicular brachial plexus and to the SSN both proximal and distal to the suprascapular ligament, without the use of interposition nerve grafts.

Epstein-Barr virus infection as a complication of transplantation of a nerve allograft from a living related donor. Case report.

Reconstruction of extensive nerve defects is hampered by the amount of autogenous nerve tissue available for transplantation and by donor site morbidity. Nerve allografts, being of foreign origin and potentially unlimited in supply, provide a solution to these problems. Studies have shown that nerve allotransplants require immunosuppression only until end-organ connections are made and that immunosuppressant therapy may be subsequently discontinued with no negative effect on functional outcome. Also, recent experimental and clinical focus has been on shorter periods of immunosuppression in order to reduce risk, even stopping immunosuppression after regeneration has reached the distal suture line rather than before recovery of end-organ connections. In the pediatric population, the increased disease burden and increased potential for nerve regeneration as well as the frequent availability of a living related donor make allografts all the more attractive as solutions to nerve reconstructive problems. Nevertheless, the risks of immunosuppression must not be underemphasized, and they deserve more attention in the current nerve transplantation literature. The authors report on a child who, at the age of 1 year, received a nerve allograft from a living related donor who was positive for Epstein-Barr virus (EBV). The child quickly developed a symptomatic EBV infection concurrent with immunosuppressant drug therapy. The immunosuppression regimen was stopped prematurely, and the patient suffered only a short illness, but the EBV infection could have developed into a life-threatening posttransplant lymphoproliferative disorder (PTLD). The patient is consequently predisposed to develop PTLD and will have to be monitored for the rest of his life. This case highlights the importance of considering the potentially fatal risks associated with this elective procedure. Future studies are needed to quantify and minimize this complication. Nevertheless, it should be weighed against the potential functional benefit from using nerve allografts.

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.