the search for new techniques and modifications of already existing ones is gaining increasing attention .
progress in flap designing and harvesting have improved the functional and aesthetic results , especially in head and neck reconstruction .
surgical technique has shifted from simply obtaining flap survival and wound coverage , to better flap selection and more sophisticated reconstruction , due to the possibility of making the transfer of thinner flaps , flaps matching the recipient site s color and texture , and complex flaps for 3-dimmensional reconstructions .
flap prefabrication is defined as implantation of separated vascular pedicle in a new territory , followed by a transfer of the flap neovascularized by this pedicle .
these flaps are mainly used in head and neck reconstruction to achieve similar texture , shape , and color to those of recipient site ; however , prefabrication is usually reserved for individual cases in which conventional techniques are unreliable or unavailable .
prefabrication is the process of making flaps to fulfill specific requirements by designing them with only required components in new vascular areas while minimizing donor site morbidity . instead of secondary corrections for a standard flap ,
vascular induction by implantation of a pedicle allows designing the flaps in discrete donor sites or in areas of skin excess .
it is possible to establish new flaps with any desired components from anatomical regions that do not have defined axial vessels .
prefabrication allows almost any tissue volume to be transferred to any specified recipient site , thus expanding the options of microsurgical reconstructions .
autologous cartilage and bone are commonly used as a framework in reconstructive surgery . however , their disadvantages ( e.g. , limited availability and the morbidity and high risk of resorption ) are quite serious . the advantages of microporous materials include decreased specific implantation weight and absence of capsular reaction .
porous high - density polyethylene is an alloplastic material used by surgeons for over 50 years , and it has been shown to be well tolerated .
it induces a minimal reaction when implanted into human tissues , and fibrovascular tissue not only anchors the implant but also imparts certain biological qualities to the implant , including the availability to support neoepithelialization and skin grafting .
the main advantage of ptfe is the interweaving and ingrowth of loose connective tissue and vasculature .
the inferior epigastric artery and vein were chosen as vascular carriers because of ease of dissection and sufficient diameter . in the first operation ,
after 8 weeks , each prefabricated complex was explored , resected , and macroscopically evaluated .
the samples obtained for histopathologic study were fixed in 10% formaldehyde solution for 24 h. the tissues were routinely processed and embedded in paraffin blocks and 5-um - thick sections were obtained and evaluated microscopically ( figure 3 ) . the research protocol for this investigation
all 20 prefabricated flaps survived and no serious surgical complications were observed . in 2 cases
nearly 90% of the pores were invaded by soft tissue after 8 weeks . in some areas ,
the fibroneovascular tissue invading the pores had reached up to the outer surfaces of the implant .
the inner parts of the implant were invaded with more mature and loose connective tissue compared with newly vascularized outer parts .
inflammatory cells and active fibroblasts were present in some spots where the fibroneovascular tissue formation was taking place .
flap prefabrication was used for the first time in 1971 by orticochea , who described vascular implantation in the retroauricular region for delayed nasal reconstruction .
the introduction of a new blood supply into subcutaneous territory in an attempt to create new vascularized flaps was first described by washio , who implanted a section of pedicled dog intestine into the abdominal skin .
those experimental studies were based on the theory that thin skin flaps can be created based on implanted vascular pedicles .
voy reported an application of proplast ii for framework for prefabricated flaps , covering the implant with omentum and a skin graft .
this pioneering research stimulated many investigators to consider the possibility of creating custom - designed donor sites by implantation of a nourishing vascular pedicle in the target tissues prior to harvest .
this vascular carrier could be mesenteric vascular pedicle , vascular bundle , or musculovascular pedicle .
based on the same concept , morrison et al prefabricated a thin axial - pattern skin flap in a rabbit model by implanting the femoral artery and vein directly into subdermal layers of skin .
this research suggested that vascular implantation provokes an extensive outgrowth of new vessels from the implanted artery and vein , and that a neovascularization process begins within a few days of implantation and progresses rapidly by 8 to 12 weeks . without doubt , the ideal approach in reconstruction of the 3-dimensional structures of the face is the use of autogenous tissue .
for this purpose , while providing inner lining with different tissues , a framework was usually formed by cartilage and bone to support these tissues . however , the difficulty of shaping autogenous tissues , the limited amount of donor - site tissues , and donor - site morbidity limit their use as a framework . for this reason , the use of alloplastic materials that can be shaped in detail 3-dimensionally and that are safer because they do not show resorption or deformation is becoming more popular .
porous materials , like polytetrafluoroethylene , are invaded by a fibroneovascular tissue and become a single unit with vascular bed and tissues after they are implanted .
because the instability and infection that are the most important risk factors for implant exposition are decreased , these materials are safer than nonporous ones . for reconstruction of 3-dimensional defects ,
in particular on the face , the most popular alloplastic material is high - density porous polyethylene .
the most important factors that reduce the long - term biocompatibility of alloplastic materials are the presence of a chronic inflammation and the instability of the implant .
even a subacute inflammation may cause detachment of the fibrovascular capsule from the implant surface and therefore trigger the chain of events that results in implant exposure and extrusion .
prefabricated flaps are a useful tool for the reconstructive surgeon because of specific preferred tissue composite , regardless of their native vascular origin , can be transferred as free or pedicled flaps , donor - site morbidity is reduced , and the functional outcome for patients may by more satisfactory .
based on the results of our study , we believe that the use of high - density porous polyethylene in flap prefabrication may be a good option for reconstruction of 3-dimensional defects , especially in patients with limited donor tissues .
 backgroundthe search for new surgical flap techniques and modifications of already existing ones is gaining increasing popularity . 
 progress in flap designing and harvesting have improved the functional and aesthetic results , especially in head and neck reconstruction.material/methodsten pigs were used in this study . in the first operation , high - density porous polyethylene prefabrication was performed bilaterally in all pigs . 
 after 8 weeks , each prefabricated complex was explored , resected , and macroscopically evaluated.resultsall of 20 prefabricated flaps survived . 
 no serious surgical complications were observed . in 2 cases 
 there was chronic inflammation and in 4 cases there was instability of the implant.conclusionsafter this experimental study , we believe that the use of high - density porous polyethylene in flap prefabrication may be a good option for reconstruction of 3-dimensional defects , especially in patients with limited donor tissues . 
Background
Material and Methods
Results
Discussion
Conclusions