Reconstructive surgeries often use topological manipulation of tissue to minimize postoperative
scarring. The most common version of this, Z-plasty, involves modifying a straight line cut into a
Z shape, followed by a rotational transposition of the resulting triangular pedicle flaps, and a final
restitching of the wound. This locally reorients the anisotropic stress field and reduces the potential for
scarring. We analyze the planar geometry and mechanics of the Z-plasty to quantify the rotation of the
overall stress field and the local forces on the restitched cut using theory, simulations, and simple physical
Z-plasty experiments with foam sheets that corroborate each other. Our study rationalizes the most typical
surgical choice of this angle, and opens the way for a range of surgical decisions by characterizing the
stresses along the cut.