A 20-year-old male suffered a severe facial segment amputation in a motor vehicle accident involving a metal pole, resulting in extensive tissue loss encompassing the nose, most of the right cheek, part of the upper lip, and most of the hard palate [Figure 1A]. The avulsed tissue, measuring 12 cm × 11 cm × 3 cm, was preserved and brought to the emergency department [Figure 1B]. Additionally, the patient had open extremity fractures and cervical spine lesions requiring immediate attention. Following examination and tracheotomy, successful revascularization was completed after seven hours of ischemia time. The flap-side did not have any viable arterial vessels for artery-to-artery anastomosis after thorough examination on the back table. The flap was ischemic for 7 h. Therefore, to vascularize the flap, an arteriovenous (AV) anastomosis was performed from the patient-side facial artery to the flap-side facial vein, relying on the valveless nature of the facial venous system to allow retrograde perfusion to the flap. This AV anastomosis was performed using 9-0 nylon suture in an end-to-end fashion. This created an AV flow-through with perfusion of oxygenated blood from the patient-side facial artery to the flap-side superior facial vein to perfuse the flap . The flap-side inferior facial vein stump was anastomosed to a branch of the patient-side facial vein with a 2.5 mm coupler to bring venous blood out of the flap back to the patient’s circulation. This created an AV flow-through with perfusion from the patient-side facial artery to the flap-side facial vein leading to retrograde perfusion, and a standard veno-venous anastomosis to relieve venous congestion.

While the flap was perfusing, inset was performed. The posterior septum was first identified on the patient and the flap tissue; Doyle splints were secured to the remaining bony septum. These splints were passed retrograde through the patient’s nasal passage to secure the nose to the face at a known landmark while maintaining nasal patency. The radix and left cheek tissue were then secured using absorbable suture.

At the right side of the defect, there was a fractured piece of mandible without periosteum lying underneath the newly anastomosed facial vessels. Risk of infection or migration of this bone leading to damage to the anastomosis prompted removal of the mandible without a reconstructive bar or bone graft. The mucosal and cutaneous tissues were then closed.

Post-procedure, the patient showed immediate improvement in facial distention, indicating successful perfusion [Figure 2]. After insetting, the patient was transferred to the intensive care unit with a heparin drip to prevent flap site thrombosis.

On post-operative day 6, the flap developed venous congestion, necessitating drainage of a hematoma and removal of the AV anastomosis. Exploration of the flap was performed and a suitable artery on the flap was identified which was not encountered on the initial exploration. An artery-to-artery anastomosis was performed using 10-0 Nylon, connecting a 1 mm branch of the previously identified patient side facial artery to the newly identified flap side facial branch to provide anterograde perfusion to the flap. Tension was noted on the venous anastomosis so a portion of the parotid tail was removed, the retromandibular vein (RMV) was dissected cephalad then clipped and mobilized anteriorly [Figure 3]. The superior vein was clipped and the inferior vein carefully trimmed before anastomosing it to the RMV. Leech therapy was temporarily initiated to address venous congestion, and on post-operative day 42, the patient was discharged with a well-perfused flap. Over three months, partial flap necrosis led to a 2 cm × 1 cm oronasal fistula, treated with an osteocutaneous free fibula flap using proximal superficial temporal vessels for anastomosis. Six months later, exposed maxillary hardware was debrided and arterial anastomosis was performed. Subsequent procedures involved scar revisions, orbit and nasal reconstruction with split calvarial grafts, and rib grafting overlay for dorsum elevation. Four years post-injury, concerns include right lower eyelid malposition, facial asymmetry, and right facial nerve paralysis, with planned medial canthopexy and temporalis transfer; however, the patient has not pursued further surgical treatments. Final reparative outcomes are shown in Figure 4.

A 21-year-old female caught her hair in an industrial machine, completely degloving her entire scalp, forehead, both eyebrows and eyelids, and both ears superior to the external auditory canals [Figure 5A-C]. The amputated tissue was preserved and brought to the emergency department without associated cervical or intracranial injuries. Before exploration, the scalp was shaved and irrigated to check for concealed lacerations. Tension-free arterial anastomosis with a 1 mm branch of the superficial temporal artery (STA) was followed by venous anastomosis with the superficial temporal vein (STV) using a 2.0 mm coupler [Figure 6A and B]. Bleeding from the donor side was observed before clamping the artery. The same procedure was performed on the left side. Arterial anastomosis was completed first using a one-to-one match with 10-0 Nylon, followed by venous anastomosis using a 1.5 mm coupler.

The patient’s eyebrows were realigned and secured to the frontal bone periosteum. Nasal bone reconstruction involved re-suspension from the periosteum. Eyelids were reconstructed with 5-0 fast-absorbing sutures. Ears were reconstructed using 3-0 chromic and 5-0 fast absorbing gut sutures, and auricular cartilage was approximated with chromic suture. Doppler signals were strong bilaterally, with good scalp capillary refill. Total ischemia time was around 5 h, and total operative time was 8 h. Two months post-surgery, the entire scalp remained viable other than a 1.5 cm border along the occiput. Necrotic tissue was debrided and closed with local tissue arrangement [Figure 7A]. One year following the injury the patient had full hair growth from the scalp with thin scarring along the repair [Figure 7B].

Confusion often exists because the nomenclature “AV shunt” does not differentiate whether the inflow is from the arterial or venous side of the capillaries (Case 1). In 1992, Morris et al. successfully anastomosed the STA to the STV in a partially amputated scalp^[8]. Seven years later, Hallock described another replantation of a partial scalp using the frontal branch of the STA anastomosed to the unnamed scalp vein and achieved excellent aesthetic results^[6]. In 2020, Lee et al. used a right posterior tibial vein as a venous graft to connect the STA to STV of the amputated scalp^[10]. Hendrick and Tiwari achieved the first successful lip replantation by connecting the superior labial artery to a facial branch at the nasolabial fold. They suggested the absence of venous valves at this level might have enabled successful replantation, or insufficient valve function under arterial perfusion^[11].

The viability risk of venous-perfused tissues depends on anastomotic site, flow direction, and venous valve density^[6]. Valve scarcity within the scalp and ear replantations with valve trimming may contribute to their success^[9]. The midface does have a lower density of valves compared to other anatomical regions of the body and face, which may partly explain why the vast majority of the amputated midface in Case 1 survived in our report^[11]. Studies show severed rabbit auricles can survive through arterialization of the venous system^[9,12]. Some argue nutrient flow occurs via AV shunts, while others suggest retrograde perfusion from artery to vein, reaching capillaries through arterialized venules^[8]. From there, blood returns centrally through venules of the low-pressure system. Artery-to-vein anastomosis is a valid technique for replanting non-salvageable maxillofacial tissue, supported by clinical and basic science experiments. Our report’s first case uniquely employs AV inflow anastomosis to salvage osteocutaneous tissue in a facial and maxillary artery watershed region.

The lip receives consistent arterial inflow but variable venous outflow, making venous anastomoses challenging. Lip replantations have a high success rate (approximately 95%), with common complications including diminutive venous vasculature and fragility of small lip veins. Venous drainage occurs through plexuses, with over 50% of replantations lacking venous anastomoses^[13]. In a review of sizable lip defects (n = 13; mean defect 10.6 cm²), the most important factor for survival was re-establishment of arterial (typically labial) flow^[7].

Nose replantations are less frequent than lip ones but are vital for facial aesthetics. Like lips, over half of these cases do not involve venous anastomosis, with various techniques used for venous congestion relief, such as open venous drainage, nasal tip abrasion, pin-pricking, stab incisions, medicinal leeches, AV outflow fistulas, intra-replant subcutaneous heparin, and heparin sponges^[14]. Arterial anastomosis in nose replantations involves various arteries, including the labial, facial, supratrochlear, angular, and anterior ethmoidal arteries^[5]. To our knowledge, there have been no reported cases where artery-to-artery anastomosis was not performed in the initial replantation attempt.

Scalp amputations often result from hair getting caught in industrial machines^[5]. The scalp played a crucial role both cosmetically and physiologically, influencing appearance, social standing, and regulating body temperature^[15]. One-stage scalp replantation has a 90%-95% success rate in large-scale reviews. While the entire scalp can survive on a single artery and vein, two sets are typically considered safer. The STA is commonly used in such procedures, as in the second case cited^[5]. The occipital artery is an option but may be problematic with cervical spine injuries^[3]. If artery-to-artery anastomosis is not possible, AV inflow anastomosis is reported^[6,8]. Independent of anastomosis technique, partial necrosis is relatively common and may occur in as high as a third of cases^[5].

Because of their common muscular connections to the galea aponeurotica, scalp avulsions often involve the ears and eyebrows. The eyebrows and associated frontalis muscle usually survive, allowing for gradual brow elevation. Revascularization of the ears is less predictable, with partial or complete loss possible, mainly due to venous insufficiency. Patient satisfaction with ear position and angulation can pose challenges, as can correcting issues such as right lagophthalmos post-replantation^[4].