Demarcation Procedure: An Effective and Safe Method before Definitive Resection of Large Arteriovenous Malformations.

Objectives: Surgical resection of large arteriovenous malformations (AVMs) is challenging owing to its prolonged operative time and massive bleeding, particularly in anatomically complex regions. This study aimed to evaluate the efficacy of a staged "demarcation procedure," a partial incision designed to interrupt blood flow and form a scar plane, in reducing intraoperative bleeding and operative time during definitive resection. Methods: Between 2014 and 2021, six patients diagnosed with Schöbinger stage III AVMs were treated using our demarcation procedure, followed by definitive resection. Lesion locations included the head and neck (n = 5) and the hand (n = 1). Operative time and intraoperative blood loss were analyzed for both demarcation procedures and definitive resections. Reconstructive procedures were also performed during the final definitive resection. Results: The demarcation procedure was performed once in two patients, twice in three, and three times in one. Fascial grafts were used in two patients and artificial dermis in three. At definitive resection, free flaps (n = 5) or a pedicled flap (n = 1) were applied, often with additional skin grafting. The median blood loss was 95 mL for demarcation and 510.5 mL for definitive resection with reconstruction. Median operative time was 220 minutes for demarcation and 236 minutes for definitive resection. No recurrences were observed during follow-up. Conclusions: The demarcation procedure, which establishes a fibrous boundary and controls feeder vessels, reduces blood loss and operative time during definitive resection of AVMs. Although this method requires multiple surgeries under general anesthesia and relatively prolonged hospitalization, it may serve as a safe and effective option for the resection of large AVMs, particularly in the head and neck.