In Pursuit of the "Perforator" in the Perforator Skin Flap.

Another congress of the World Society for Reconstructive Microsurgery (WSRM) this past year in Bologna was magnificent not just for the presentation of so many keynote lectures by the giants of our field nor the novel and innovative ideas shown by those who will someday follow in those footsteps, but by making all of us realize how many capable microsurgeons there are now practically everywhere in this world, doing incredibly important surgical management of challenges that previously were unmet and resulted in sheer devastation for so many of our patients. How much we are the same in our goals, aspirations, and abilities could not be overlooked, but it is amazing how much we also want to learn more together-each relying on the other. To do so, we must not forget our origins as we appropriately plan for the future. All this we philosophized in our WSRM panel on lower extremity reconstruction, while emphasizing on the surface the perforator flap that at the least today has caught everyone's attention. In this overview to follow, we once again tell two stories, starting with the beginnings of the concept of flaps in showing how the nomenclature has evolved over time according to our various surgical manipulations. Often overlooked, though, is a parallel timeline by the anatomists who have better elucidated the circulation to these flaps, where it will become obvious that often long ago the existence of perforators was recognized by them long before known by the surgeons. At least today, these two paths have at least temporarily intersected. Our pursuit of the "perforator" in the perforator skin flap has come full circle, following the course of the history of the flap itself-a pursuit of excellence.

The quadriceps Femoris allograft as an extension of the Angiosome concept: A cadaveric-based anatomical feasibility study.

BACKGROUND: Vascularised composite allo-transplantation (VCA) is emerging as a tailored approach for complex tissue reconstruction. This study focuses on the quadriceps VCA as a potential solution for tissue repair, following trauma, necrotising fasciitis/myositis, or tumor ablation. METHODS: Dissections were undertaken in 10 adult cadaveric lower limbs to characterize the blood supply to the quadriceps femoris for en bloc muscle allo-transplantation. A mock cadaveric transplantation was performed to (a) define the best neurovascular VCA design and (b) test the feasibility of the procedure. A review of 54 archival radiograph studies from the institution was also performed to further evaluate the muscle vasculature. RESULTS: In two lower limbs, the quadriceps VCA was harvested designed on the common and superficial femoral vessels and nerve, which revealed a lengthy and bloody dissection, especially of the veins, which could increase clinically with the inability to use a tourniquet for most of the dissection. However, review of our previous archival studies showed that all four quadriceps muscles are supplied within the lateral circumflex femoral angiosome. In a further eight lower limbs, the quadriceps femoris muscle group consistently received its blood supply from the lateral circumflex femoral angiosome, verified by selective lead oxide injections of this artery. The vastus medialis appeared to have a more tenous blood supply distally based on this angiosome. A successful mock cadaveric transplant was performed based on this data. CONCLUSIONS: We suggest that the best neuromuscular quadriceps VCA should be (a) designed on the lateral circumflex femoral pedicle, (b) should be raised from distal to proximal, and (c) should include the descending genicular vessels as a potential supplemental supply to vastus medialis, should all four muscles be required.

Arteriovenous Shunts: Their Location and Role in Physiology, Pathology, and Tissue Transfer. A Preliminary Report in the Upper Limb.

Background: Tiny arteriovenous (AV) shunts of 10-150 µm (0.01-0.15 mm) are documented in the hands and feet. Larger shunts up to 0.5 mm (500 µm) have been discovered by the authors in the inner canthus and the human eye. This study seeks their possible existence in the upper limb. Methods: Radiographic lead oxide cadaver injection and dissection studies of 14 archival and six new upper limbs were examined. Results: AV shunts of 0.1-0.5 mm were discovered between the brachial, ulnar, and radial arteries and their venae comitantes and between their arterial perforators and the subcutaneous veins. Conclusion: This pilot study provides insight into the possible function of these large AV shunts associated with blood flow variation in temperature, blood pressure, tissue transfer, flap prefabrication, and flap necrosis.

Thermoregulation, Not Just Camouflage: The Unique Vasculature of Giraffe Patches. A Cadaver Study with Clinical Implications.

BACKGROUND: Serendipitously, a dead giraffe provided opportunity to study its vascular anatomy. Comparative animal studies have revealed important information for designing new flaps and new microsurgical techniques. So, do giraffe's patches support a thermal window concept, do animals with similar markings and habitat have a similar thermoregulatory role, and could results offer new insight into human thermoregulation and free tissue transfer? METHODS: Previously described lead-oxide arterial-only injection studies, of a single giraffe, zebra, Africa wild dog, and spotted jaguar, all with wire-encircled pigmented patches; and archival human, pig, dog, cat, and rabbit studies, were compared. RESULTS: Each giraffe patch was supplied by just a single artery (angiosome) averaging 0.9 mm diameter, that divided near its center and sent dense, long, parallel, radiating spoke-wheel branches averaging 0.62 mm diameter to the patch margin, continuing as reduced-caliber choke anastomoses averaging 0.8 mm to link adjacent patch angiosomes. Uniquely arranged large veins, with an average of 1.66 mm, encircled the patches in the pale skin paralleled by arteriae comitantes averaging 0.22 mm. These arteries, connected to patch angiosomes, filled the veins intermittently by means of arteriovenous (A-V) shunts averaging 0.12 mm in diameter of magnitude never seen before in any species studied. None of the other three animals had angiosome territories matching their pigmented fur, or significant A-V filling. CONCLUSIONS: This study supports the "thermostatic" concept of the giraffe skin patches, with A-V shunts playing a major role. It affirms the need for further studies of these shunts in human thermoregulation and other flow regulations in physiology, pathology, and free tissue transfer.

Lymphatic vessel density in primary melanomas predicts sentinel lymph node status and risk of metastasis.

AIMS: Important prognostic factors in patients with cutaneous melanoma include primary tumour thickness/depth of invasion, ulceration and mitotic rate, and the presence of tumour cells in regional lymph nodes. More recently, features of stromal components, such as blood and lymphatic vessel density, have been suggested as additional indicators of metastatic potential. Our aim was to investigate the relationship between tumour lymphatic vessels and lymph node metastasis. METHODS AND RESULTS: Metastasizing (n = 11) and non-metastasizing (n = 11) primary melanoma samples matched for depth/thickness, mitotic rate and ulceration were examined for lymphatic vessel density (LVD) in the primary tumour, using an antibody to podoplanin. Significant differences were found between LVD (vessels/unit area) in the peripheral (5.73 ± 0.67) versus central (1.72 ± 0.42) regions of the metastasizing tumour group (P < 0.001), and between LVD in the peripheral areas of metastasizing (5.73 ± 0.67) versus non-metastasizing (4.21 ± 0.37) tumours (P < 0.01). No overall difference was found between total average LVD in the two tumour groups or between their vessel morphology. CONCLUSION: Our results show that LVD is associated with risk of lymph node metastasis. Furthermore, the ratio of peripheral LVD:central LVD is a useful marker of primary melanomas that are likely to metastasize to lymph nodes.

The Functional Anatomy of the Ophthalmic Angiosome and Its Implications in Blindness as a Complication of Cosmetic Facial Filler Procedures.

BACKGROUND: Blindness following facial filler procedures, although rare, is devastating, usually acute, permanent, and attributed to an ophthalmic artery embolus. However, blindness may be delayed for up to 2 weeks, sometimes following injection at remote sites, suggesting alternative pathways and pathogenesis. METHODS: Seeking solutions, fresh cadaver radiographic lead oxide injection, dissection, and histologic studies of the orbital and facial pathways of the ophthalmic angiosome, performed by the ophthalmic artery and vein, both isolated and together, and facial artery perfusions, were combined with total body archival arterial and venous investigations. RESULTS: These revealed (1) arteriovenous connections between the ophthalmic artery and vein in the orbit and between vessels in the inner canthus, allowing passage of large globules of lead oxide; (2) the glabella, inner canthi, and nasal dorsum are the most vulnerable injection sites because ophthalmic artery branches are anchored to the orbital rim as they exit, a plexus of large-caliber avalvular veins drain into the orbits, and arteriovenous connections are present; (3) choke anastomoses between posterior and anterior ciliary vessels supplying the choroid and eye muscles may react with spasm to confine territories impacted with ophthalmic artery embolus; (4) true anastomoses exist between ophthalmic and ipsilateral or contralateral facial arteries, without reduction in caliber, permitting unobstructed embolus from remote sites; and (5) ophthalmic and facial veins are avalvular, allowing reverse flow. CONCLUSION: The authors' study has shown potential arterial and venous pathways for filler embolus to cause blindness or visual field defects, and is supported clinically by a review of the case literature of blindness following facial filler injection.

Increasing Perfusion Pressure Does Not Distend Perforators or Anastomoses but Reveals Arteriovenous Shuntings.

BACKGROUND: It has been proposed that hyperperfusion of perforators and distension of anastomotic vessels may be a mechanism by which large perforator flaps are perfused. This study investigates whether increasing perfusion pressure of radiographic contrast in cadaveric studies altered the radiographic appearance of vessels, particularly by distending their anastomotic connections. METHODS: From 10 fresh cadavers, bilateral upper limbs above the elbow were removed. Three cadavers were excluded. Seven pairs of limbs were injected with lead oxide solutions via the brachial artery while distally monitoring intravascular pressure in the radial artery using a pressure transducer. One limb was injected slowly (0.5 mL/s) and the other rapidly (1.5 mL/s) to produce low and high perfusion pressures, respectively. Skin and subcutaneous tissue were then removed and radiographed. RESULTS: The filling of perforators and their larger caliber branches appeared unchanged between low- and high-pressure injections, with no significant increase in true anastomoses (P = 0.32) and no association between maximum perfusion pressure and number (P = 0.94) or caliber (P = 0.10). However, high-pressure injections revealed arteriovenous shunting with filling of the tributaries of the major veins. CONCLUSIONS: This study demonstrated that increased perfusion pressure of the cutaneous arteries (1) did not change the caliber of vessels; (2) did not convert choke to true anastomoses; and (3) revealed arteriovenous shunting between major vessels with retrograde filling of venous tributaries as pressure increased. This suggests that it is not possible to distend anastomotic connections between vascular territories by increasing perfusion alone.

Advances in the pre-operative planning of deep inferior epigastric artery perforator flaps: magnetic resonance angiography.

Imaging of the abdominal wall vasculature prior to deep inferior epigastric artery (DIEA) perforator (DIEP) flaps has been shown to significantly improve surgical outcomes. Although computed tomography angiography (CTA) has been shown to be highly accurate, it is associated with radiation exposure, and as such modalities without radiation exposure have been sought. Magnetic resonance angiography (MRA) has been proposed as such an option. We conducted a pilot study comparing MRA with CTA and with operative findings in six consecutive patients undergoing DIEP flaps for breast reconstruction. The DIEA, superficial inferior epigastric artery (SIEA) and perforators were all assessed with each modality. We found that the DIEA and SIEA were accurately imaged with both CTA and MRA, but that while MRA could identify some major perforators, CTA was more accurate than MRA for perforator mapping. As such, while MRA does have a role in the imaging of DIEA perforators, CTA is still the preferred modality. On the basis of these findings, a larger study into the role for MRA in this setting is warranted.

Historical review of breast lymphatic studies.

The gross anatomy of the lymphatic system is one of the least studied areas of anatomy, primarily because of the technical difficulties encountered in demonstrating this almost invisible yet vast system. Similarly, there have been very few studies of the gross lymphatic anatomy of the adult human breast. Previous studies used young pregnant female cadavers. When mercury was injected into the lactiferous ducts or breast lymphatic channels, these cadavers enabled early anatomists to see the breast lymphatics. Both Cruikshank (1786) and Cooper (1840) located the axillary lymph pathway as well as accessory pathways directly from the breast. Sappey (1874) concluded that all lymphatics arising from the breast drained into the axilla via the subareolar plexus. Current descriptions of the breast lymphatics may be traced back to the diagram made by Poirier and Cuneo (1902). However, it is apparent that this diagram is a composite of adult breast studies by Sappey, their fetal studies and even clinical feedback. This study provides an historical perspective of the methods that have been previously used to study the lymphatics of the breast and introduces an update on current investigative approaches.

The effect of anterior abdominal wall scars on the vascular anatomy of the abdominal wall: A cadaveric and clinical study with clinical implications.

The anterior abdominal wall integument is frequently used in a range of reconstructive flaps. These tissues are supplied by the deep and superficial inferior epigastric arteries (DIEA and SIEAs) and the deep and superficial superior epigastric arteries (DSEA and SSEAs). Previous abdominal wall surgery alters this vascular anatomy and may influence flap design. One hundred and sixty-eight patients underwent abdominal wall computed tomographic angiography (CTA) for preoperative imaging. Fifty-eight of these patients had undergone previous abdominal surgery, and were assessed for scar pattern and relationship to the course and distribution of all major axial vessels and perforators. Two cadaveric abdominal wall specimens with midline abdominal scars underwent contrast injection of the DIEAs and DSEAs, with subsequent CTA. The course and distribution of all cutaneous vessels were assessed. In all clinical and cadaveric cases, the vasculature of the abdominal wall had been altered by previous surgery. In the clinical cases, vascular architecture was universally altered in the region of the scar, often modifying the filling patterns of the abdominal wall and occasionally precluding the use of an abdominal wall flap. In both cadaveric specimens, regions of non-filling were evident upon contrast injection, highlighting the angiosomes not supplied by the DIEA or DSEA. Previous abdominal wall surgery necessarily alters the vascular architecture of the abdominal wall, and may alter the source vessels supplying cutaneous tissues. CTA was useful in identifying and delineating these changes, and may be used as a preoperative tool in this role.

The arterial anatomy of the Achilles tendon: anatomical study and clinical implications.

The Achilles tendon is the most frequently ruptured tendon in the lower limb and accounts for almost 20% of all large tendon injuries. Despite numerous published studies describing its blood supply, there has been no uniformity in describing its topography. The current study comprises a detailed anatomical study of both the intrinsic and extrinsic arterial supply of the Achilles tendon, providing the detail sought from studies calling for improved planning of surgical procedures where damage to the vascularity of the Achilles tendon is likely. A dissection, microdissection, histological, and angiographic study was undertaken on 20 cadaveric lower limbs from 16 fresh and four embalmed cadavers. The Achilles tendon is supplied by two arteries, the posterior tibial and peroneal arteries. Three vascular territories were identified, with the midsection supplied by the peroneal artery, and the proximal and distal sections supplied by the posterior tibial artery. The midsection of the Achilles tendon was markedly more hypovascular that the rest of the tendon. The Achilles tendon is at highest risk of rupture and surgical complications at its midsection. Individuals with particularly poor supply of the midsection may be at increased risk of tendon rupture, and approaches to the tendon operatively should consider the route of supply by the peroneal artery to this susceptible part of the tendon.

The arterial supply of the patellar tendon: anatomical study with clinical implications for knee surgery.

The middle-third of the patellar tendon (PT) is well-established as a potential graft for cruciate ligament reconstruction, but there is little anatomical basis for its use. Although studies on PT vascular anatomy have focused on the risk to tendon pedicles from surgical approaches and knee pathophysiology, the significance of its blood supply to grafting has not been adequately explored previously. This investigation explores both the intrinsic and extrinsic arterial anatomy of the PT, as relevant to the PT graft. Ten fresh cadaveric lower limbs underwent angiographic injection of the common femoral artery with radio-opaque lead oxide. Each tendon was carefully dissected, underwent plain radiography and subsequently schematically reconstructed. The PT demonstrated a well-developed and consistent vascularity from three main sources: antero-proximally, mainly by the inferior-lateral genicular artery; antero-distally via a choke-anastomotic arch between the anterior tibial recurrent and inferior medial genicular arteries; and posteriorly via the retro-patellar anastomotic arch in Hoffa's fat pad. Two patterns of pedicles formed this arch: inferior-lateral and descending genicular arteries (Type-I); superior-lateral, inferior-lateral, and superior-medial genicular arteries (Type-II). Both types supplied the posterior PT, with the majority of vessels descending to its middle-third. The middle-third PT has a richer intrinsic vascularity, which may enhance its ingrowth as a graft, and supports its conventional use in cruciate ligament reconstruction. The pedicles supplying the PT are endangered during procedures where Hoffa's fat pad is removed including certain techniques of PT harvest and total knee arthroplasty.

Abdominal wall CT angiography: a detailed account of a newly established preoperative imaging technique.

Institutional review board approval was obtained for this study, and all patients gave written informed consent. Autologous surgical breast reconstruction with use of abdominal wall donor flaps based on the deep inferior epigastric artery (DIEA) and one or more of its anterior musculocutaneous perforating branches (DIEA perforator flap) is being used with increasing frequency instead of breast reconstruction with use of traditional transverse rectus abdominus musculocutaneous and modified muscle-sparing flaps. Preoperative mapping of the DIEA perforators with abdominal wall computed tomographic (CT) angiography may improve patient care by providing the surgeon with additional information that will lead to optimization of the surgical technique, shorter procedure time, and reduction in the frequency of surgical complications. The branching patterns of the DIEA, the segmental anatomy of the anterior adipocutaneous perforating branches of the DIEA, and the importance of these features in pre- and intraoperative surgical planning necessitate a different approach to abdominal wall CT angiography than that used with other abdominal CT angiographic techniques. In abdominal wall CT angiography, the common femoral artery is used as the bolus trigger, CT scanning is performed in the caudocranial direction, the automatic exposure control feature is disabled, a scaled grid overlay tool is used to present information to the surgeons, and radiation dose is minimized (average dose, 6 mSv). The anatomic accuracy of abdominal wall CT angiography has been investigated in cadaveric and surgical studies, with sensitivity of 96%-100% and specificity of 95%-100%. This detailed description will allow other radiologists and surgeons interested in free DIEP flap surgery to incorporate this useful tool into their practice.

The lymphatic anatomy of the breast and its implications for sentinel lymph node biopsy: a human cadaver study.

BACKGROUND: Current understanding of the lymphatic system of the breast is derived mainly from the work of the anatomist Sappey in the 1850s, with many observations made during the development and introduction of breast lymphatic mapping and sentinel node biopsy contributing to our knowledge. METHODS: Twenty four breasts in 14 fresh human cadavers (5 male, 9 female) were studied. Lymph vessels were identified with hydrogen peroxide and injected with a lead oxide mixture and radiographed. The specimens were cross sectioned and radiographed to provide three dimensional images. Lymph (collecting) vessels were traced from the periphery to the first-tier lymph node. RESULTS: Lymph collecting vessels were found evenly spaced at the periphery of the anterior upper torso draining radially into the axillary lymph nodes. As they reached the breast some passed over and some through the breast parenchyma, as revealed in the cross-section studies. The pathways showed no significant difference between male and female specimens. We found also perforating lymph vessels that coursed beside the branches of the internal mammary vessels, draining into the ipsilateral internal mammary lymphatics. In some studies one sentinel node in the axilla drained almost the entire breast. In most more than one sentinel node was represented. CONCLUSION: These anatomical findings are discordant with our current knowledge based on previous studies and demand closer examination by clinicians. These anatomical studies may help explain the percentage of false-negative sentinel node biopsy studies and suggest the peritumoral injection site for accurate sentinel lymph node detection.

Defining the role for autologous breast reconstruction after mastectomy: social and oncologic implications.

Breast reconstruction plays a significant role in the management of breast cancer. The removal of a breast has implications for the psychologic, social, and sexual well-being of the patient, establishing the need for discussion of postmastectomy breast reconstruction with suitable patients. However, operative morbidity and the potential for diminished oncologic safety are ongoing issues of contention. A Medline literature review was performed to evaluate the interplay between the psychosocial need for breast reconstruction in patients after mastectomy and the issues surrounding its oncologic safety. Immediate breast reconstruction does not impair the oncologic safety of breast cancer management, with no increase in local recurrence rates, and no delays in the initiation of adjuvant chemotherapy or radiation therapy (RT). Immediate breast reconstruction in the setting of chemotherapy is not associated with greater complication rates; however, there is some evidence for increased complications in the setting of adjuvant RT. Breast reconstruction has a positive effect on the psychosocial outcomes of mastectomy and is oncologically safe in the immediate and delayed settings. Ultimately, the decision-making process of whether to reconstruct, how to reconstruct, and when to reconstruct requires a multidisciplinary approach, with the patient, plastic surgeon, oncologic surgeon, medical oncologist, and radiation oncologist all contributing.

Senile changes in human lymph nodes.

BACKGROUND: The degenerative process of lymph nodes is poorly documented. METHODS: 161 lymph nodes of seven fresh and one embalmed human cadavers in the head and neck were studied. We used 6% hydrogen peroxide, lead oxide injectant, and radiographs to demonstrate lymphatic vessels, and found both solidified and transparent lymph nodes. They were removed, fixed in 10% formalin and sent for histopathology cross section. RESULTS: Thirty-eight solidified and 123 transparent lymph nodes were found. A series of histopathological sections show the degenerative process is variable and continuous. Senile involution affects all elements of the lymph node including the cortex, the medulla, and the architecture. CONCLUSION: This study provides actual anatomical and histopathological images of lymph nodes in different degenerative stages in the head and neck region. It may help explain some clinical conditions in the elderly, especially their diminished immunological response to infection and cancer metastasis.

The angiosome territories of the spinal cord: exploring the issue of preoperative spinal angiography. Laboratory investigation.

OBJECT: The angiosome concept has been the subject of extensive research by the senior author (G.I.T.), but its specific applicability to the spinal cord was hitherto unknown. The aim of this study was to see if the spinal cord vasculature followed the angiosome concept and to review the usefulness of preoperative spinal angiography in surgery for spinal disorders. Spinal cord infarction and permanent paraplegia may result from inadvertent interruption of the artery of Adamkiewicz. Spinal angiography, which may enable avoidance of this catastrophic complication, is still not commonly used. METHODS: Two fresh cadavers were injected with a gelatin-lead oxide mixture for detailed comparative study of spinal cord vasculature. One cadaver had insignificant vascular disease, whereas the other had extensive aortic atherosclerosis, presenting a unique opportunity for study. After removal from each cadaver, radiographs of the spinal cords were obtained, then photographed, and the vascular territories of the cords were defined. RESULTS: Four angiosome territories were defined: vertebral, subclavian, posterior intercostal, and lumbar. These vascular territories were joined longitudinally by true anastomotic channels along the anterior and posterior spinal cord. Anastomosis between the anterior and posterior vasculature was poor in the thoracolumbar region. The anterior cord relied on fewer feeder arteries than the posterior, and the anterior thoracolumbar cord depended on the artery of Adamkiewicz for its supply. In chronic aortic disease with intercostal artery occlusion at multiple levels, a rich collateral circulation supporting the spinal cord was found. CONCLUSIONS: The arterial supply of the spinal cord follows the angiosome concept. The atherosclerotic specimen supports the suggestion that the blood supply is able to adapt to gradual vascular occlusion through development of a collateral circulation. Nevertheless, the spinal cord is susceptible to ischemia when faced with acute vascular occlusion. This includes inadvertent interruption of the artery of Adamkiewicz. The authors recommend the use of preoperative spinal angiography to prevent possible paraplegia in removal of thoracolumbar spinal tumors.

Does the preoperative imaging of perforators with CT angiography improve operative outcomes in breast reconstruction?

BACKGROUND: Breast reconstruction is increasingly performed with the use of the abdominal wall donor site, with potential complications including donor site morbidity and impaired flap viability. As a tool for selecting the optimal perforators which will ultimately supply the flap, preoperative imaging with computed tomography angiography (CTA) has become increasingly popular. Potential benefits include reduced intramuscular dissection, with faster and safer dissection, reduced donor site morbidity and improved flap vascularity and survival. Despite the potential for improvements in operative outcome, any benefits are yet to be established. METHODS: A cohort study of 104 breast reconstructions in 88 patients was conducted. All patients underwent breast reconstruction based on an abdominal wall free flap. Of these, 40 patients undergoing preoperative imaging with CTA and 48 patients not undergoing CTA were included, with all CTAs undertaken at a single institution. Length of operation, length of stay, and operative complications were assessed. An evaluation of operative stress was achieved with the use of visual analogue scales (VAS) administered to the surgeons. RESULTS: The use of CTA was associated with decreased operating time (mean: 77 min for bilateral cases), significantly decreased complications related to flap viability (particularly partial flap loss), and a statistically significant reduction in donor site morbidity. Psychometric testing of surgeons revealed a statistically significant decrease in operative stress (41% decrease) with the use of preoperative CTA. CONCLUSION: The use of CTA for preoperative imaging in breast reconstruction is associated with improved operative outcomes.

The Role of Anastomotic Vessels in Controlling Tissue Viability and Defining Tissue Necrosis with Special Reference to Complications following Injection of Hyaluronic Acid Fillers.

BACKGROUND: Most target areas for facial volumization procedures relate to the anatomical location of the facial or ophthalmic artery. Occasionally, inadvertent injection of hyaluronic acid filler into the arterial circulation occurs and, unrecognized, is irreparably associated with disastrous vascular complications. Of note, the site of complications, irrespective of the injection site, is similar, and falls into only five areas of the face, all within the functional angiosome of the facial or ophthalmic artery. METHODS: Retrospective and prospective studies were performed to assess the site and behavior of anastomotic vessels connecting the angiosomes of the face and their possible involvement in the pathogenesis of tissue necrosis. In vivo studies of pig and rabbit, and archival human total body and prospective selective lead oxide injections of the head and neck, were analyzed. Results were compared with documented patterns of necrosis following inadvertent hyaluronic acid intraarterial or intravenous injection. RESULTS: Studies showed that the location of true and choke anastomoses connecting the facial artery with neighboring angiosomes predicted the tissue at risk of necrosis following inadvertent intraarterial hyaluronic acid injection. CONCLUSION: Complications related to hyaluronic acid injections are intimately associated with (1) the anatomical distribution of true and choke anastomoses connecting the facial artery to neighboring ophthalmic and maxillary angiosomes where choke vessels define the boundary of necrosis of an involved artery but true anastomoses allow free passage to a remote site; or possibly (2) retrograde perfusion of hyaluronic acid into avalvular facial veins, especially in the periorbital region, and thereby the ophthalmic vein, cavernous sinus, and brain.