Moving from the O-Z flap to the O-S flap for scalp reconstruction: A new geometrical model.

The O-Z flap is the most commonly used local flap technique to repair round and oval scalp defects in clinical practice. Preoperative flap marking is one of the major technical issues of this reconstructive method and it is essential to achieve an optimal outcome. Nevertheless, the absence of a unified arc design scheme could significantly limit the use of this useful and reliable technique, and flap drawing is sometimes based more on the surgeon's experience than on a real geometrical model. Our aim was to describe an intuitive and standardizable method for O-Z flap marking, that we called "O-S flap," based on a simple and easily replicable geometrical pattern. We reported our experience in this case series of eight patients with skin tumors of the scalp who underwent scalp reconstruction with the "O-S flap" technique at our university hospital. Most patients had defects located on the vertex or parieto-occipital regions of the scalp. The area of the defects ranged from 7 to 78.5 cm. There were no cases of flap necrosis, wound infection, or positive margins, and no patients required revision surgery. We believe that our technical refinement represents a safe, easy, and reproducible method for O-Z flap marking. It follows a simple geometrical model which could be customized according to different clinical needs.