Reconstruction of the Head and Neck region of recipient vessels, which includes branches of the thyrocervical trunk, thoracoacromial system, and internal mammary artery. It should be noted that these regions are meant to help reconstructive surgeons conceptualize the head and neck vasculature in an organized way, not to guide reconstructive decisions. The region of the planned reconstruction may or may not coincide with the zone of recipient vessel selection. For example, a scalp reconstruction in zone I may in fact also have recipient vessels in zone I (i.e., superficial temporal artery/vein); however, a fibular reconstruction of the mandible (zone I) is likely to have recipient vessels selected within zone II or III. In fact the majority of reconstructions often results in the selection of recipient vessels one or more zones removed from the reconstruction for the optimal pedicle configuration. Some detailed considerations of the recipient zones follow.
Zone I
M
Recipient vessels within zone I include the facial artery lateral to the mandible, the ascending palatine artery, the angular artery (distal facial artery), the maxillary artery, and the superficial temporal artery. Access to deeper systems, such as the ascending palatine or maxillary artery, generally requires an ablative procedure that exposes these vessels, and they are infrequently utilized due to their anatomic location. Knowledge of the available vessel options within zone I is critical for planning microvascular reconstructions of the nasal complex or anterior forehead/scalp and orbit. The facial artery and vein passing lateral to the body of the mandible provide excellent caliber and reliability within zone I for microvascular reconstruction. Location of these vessels is readily achieved by palpation of the mandibular notch and careful dissection to identify the vessels for vascular access as well as to identify and protect the marginal branch of the facial nerve, which overlies the facial vein in this region. Distally, the angular/nasolabial branch of the facial artery may be reliably located within the nasolabial fold and has been used successfully for microvascular reconstruction.1 Cadaveric investigation revealed that the average length of the artery was 28 mm and the mean diameter of the respective artery and vein (1.5 and 2.5 mm) was suitable for microvascular anastomosis in 85% of the sides investigated.2 Successful intraoral preparation and microvascular anastomosis has been reported as well and represents an option for intraoral reconstructions when extraoral incisions may be avoided.3 Reconstructive surgeons have utilized the superficial temporal system of the external carotid artery for the reconstruction of facial, scalp, and maxillary defects.4,5 This system is often avoided or ignored by many surgeons due to unfamiliarity with the anatomy or concerns about vessel diameter and reliability. The location of the superficial temporal artery is extremely consistent and is approximately 1 cm anterior to the external ear and is readily located with Doppler examination. Advantages of this recipient site include avoiding previously radiated areas, good anatomic reliability, and the avoidance of vein grafting for reconstructions of this region. Dissection of the vessels
often requires some dissection within the superior portion of the parotid gland, and careful attention to avoid damaging the frontal branch of the facial nerve is required. The superficial temporal vein is relatively thin, and careful dissection and avoiding excessive manipulation or kinking during microvascular anastomosis are required. Dissection should proceed immediately subcutaneously in this area until the superficial temporal vein is identified to avoid damaging the vein. Caution should be exercised when selecting these vessels for microvascular reconstruction if the region has received radiation.5
Zone II Recipient vessels located within zone II are the most commonly utilized vessels for microvascular reconstruction of the head and neck. The branches of the external carotid artery (and in some cases the external carotid artery itself) provide excellent caliber and flow characteristics for microvascular reconstruction and have proven to be very reliable in large series of microvascular reconstructions. It should be noted that vessels within zone II are often within the target region of previous radiotherapy for pharyngeal/laryngeal malignancies or metastatic cervical lymph nodes. Vessels that appear to have sufficient diameter may reveal significant intimal/medial thickening due to radiation, and the actual internal diameter may be quite attenuated under microscopic inspection. The reconstructive surgeon must verify adequate flow from the selected vessel prior to arterial anastomosis. As a general principle, selection of the artery with the strongest arterial flow rather than the largest diameter yields more reliable results. The facial artery is arguably the most commonly used vessel for head and neck microvascular reconstruction. Its favorable location, length, and diameter make it an ideal candidate for microvascular anastomosis within this region. Experienced microvascular surgeons have noted that the tethering of the facial artery by the digastric/stylohyoid muscles may preclude adequate access to the artery or introduce untoward positioning of the vascular pedicle. Division of the digastric muscle is recommended to address these issues.6 The lingual artery may be accessed in a similar fashion, and arises slightly inferior to the facial artery from the external carotid artery. Identification of the hypoglossal nerve in this area may be required to provide appropriate vascular access and avoid damaging the nerve. The superior thyroid artery provides excellent caliber and reliability for microvascular reconstructions. Cadaveric investigations have reported the outer diameter of the superior thyroid artery to be approximately 3.5 mm. It should also be noted that the reported location of the artery in relation to the carotid bifurcation is somewhat variable.7 The superior thyroid artery offers an additional advantage of having an inferior orientation relative to the superior orientation of all other branches of the external carotid. Excellent arterial length may be obtained by tracing the artery inferiorly until several branches supplying the thyroid gland are encountered and vessel diameter is compromised. Interestingly, using the superior thyroid artery in a reverse
160
Genden_5763_Chapter10_main.indd 160
2/24/2012 6:40:59 PM