The size of the Y: the multiple Y-V plasty revisited.

Background: The multiple Y-V plasty is often used in the release of burn scar contracture bands. Although there are established views regarding its design, no attempts have yet been made to describe the mathematical principles upon which it is based. An understanding of the mathematics, however, should incur a greater ability to "fine tune" or "tailor" the outcome.

Method: Our standard method of design and execution is presented, and the mathematical properties underlying the technique are elucidated, using a simple trigonometric model.

Results: In a Euclidian plane, the equation describing the gain in length for a rectangular scar or contracture of length l and width a, to which the technique of multiple Y-V plasty has been applied, can be simplified to lx/a, where x is the only variable and represents the distance by which the component triangular V-shaped flaps have been advanced relative to one another.

Conclusion: This equation illustrates that (a) neither the angles of the Ys nor the number of triangles in the design play a role in the ultimate length gained and (b) the distance of advancement of the individual triangular flaps is the sole determinant of final length.