Effects of thinning the anterolateral thigh flap on the blood supply to the skin.

The anterolateral thigh (ALT) flap is becoming a popular option for reconstructing a variety of soft-tissue defects, especially in the head and neck. Thinning of the flap may extend its usefulness to situations requiring less bulk, and the successful use of this technique has previously been described in the Far East. However, similar results have not yet been produced in the West. To investigate this, it is proposed that 'one-stage thinning of the ALT flap does not disrupt the blood supply to any area of the flap skin'. A series of 10 ALT flaps were raised from Western European cadavers. The arteries of the flaps were injected with Indian ink and latex rubber, and six of the flaps were cleared by the Spalteholz technique. Patterns of dye filling were compared in full-thickness and thinned specimens, and the arterial organisation within the subcutaneous fat was studied. We saw 14 perforators in 10 ALT flap dissections. These arose from the descending branch of the lateral circumflex femoral artery in eight cases and from the transverse branch in two cases. Large branches from the perforator were seen to form an arterial plexus at the level of the deep fascia, which communicates with the subdermal plexus supplying the skin. Further branches arose from the perforator and travelled obliquely through the fat to reach the subdermal plexus. In the thinned cadaver ALT flaps, dye perfusion did not reach the distal portions of the subdermal plexus. There was reduced dye filling in comparison to the full-thickness specimens. Thinning of the ALT flap reduces arterial perfusion in cadaver specimens. This allows rejection of the null hypothesis. The fascial plexus and the oblique vessels supplying the subdermal plexus are likely to be damaged or removed during thinning. This may explain the observed reduction in subdermal-plexus filling in the thinned specimens. In the clinical setting, disruption of the arterial supply in this manner could lead to ischaemia and skin necrosis in thinned flaps. One-stage thinning of the ALT flap may not be advisable in the Western population.