Answer:
The BAT (bilateral advancement transposition) flap is a technique for surgical treatment of male pattern hair loss in the anterior scalp. It employs bilateral temporal flaps which are posteriorly based and oriented in an obliquely vertical fashion with the tip of the flap roughly corresponding to the area of the sideburns. The flaps are advanced anteriorly and rotated so that the tips of the bilateral flaps meet in the midfrontal area.
The TAT (triple advancement transposition) flap is a refinement of the BAT flap technique. In addition to the bilateral vertical temporal flaps, a scalp expansion is first performed of the posterior scalp over a three-month period using 1000 cc to 1200 cc of inflation. Once tissue expansion is accomplished, the BAT procedure is then performed with the addition of a third advancement using a TPO (temporoparieto-occipital) flap created from the area of the posterior scalp expansion. This third flap is advanced forward to cover the vertex. The advantages of this technique include: anterior direction of frontal hair, recreation of crown-vertex whorl, maintenance of temporal recession, ease of donor closure, dense hair coverage of entire scalp, reliability of flaps, and the avoidance of a need for flap delay. The primary morbidity is the discomfort and deformity of the expander during the inflation period.
The TAT flap: