Trapdoor effect in nasolabial flaps. Causes and corrections.

The trapdoor effect is an elevated and bulging deformity of tissue within the semicircular confines of a U-, C-, or V-shaped scar. Various theories to explain this phenomenon are lymphatic and venous obstruction, hypertrophy of the scar, excessive fatty and redundant tissue, beveled wound edges, and contracture of the scar. Our data suggest that scar contracture is the predominant cause of the trapdoor effect in nasolabial flaps. For mild to moderately severe trapdoor deformities, multiple, small Z-plasties about the periphery of the nasolabial flap are indicated. Intralesional triamcinolone acetonide injections may produce a "pharmacologic Z-plasty" effect in some trapdoor deformities. For marked trapdoor deformities, the combination of multiple, small Z-plasties along the semicircular scar and peripheral undermining about the trapdoor defect is the corrective procedure. The trapdoor deformity may be prevented or lessened by peripheral undermining about the recipient site of the flap equal to or greater in area than the recipient site.