The search for ways of reducing the amount of transverse shortening without significantly affecting the amount of lengthening has led to the development of the multiple Z-plasty, and its advantages are such that it has replaced the single Z-plasty in many clinical situations. In the single Z-plasty one large Z extends along virtually the entire length of the contrac-ture; in the multiple Z-plasty the contracture is viewed as having a number of segments, on each of which a small Z-plasty is constructed.
The contrast between the two types of Z-plasty can best be appreciated by using a concrete example. If we construct a single Z-plasty which is going to achieve 2 cm of lengthening, and at the same time construct a series of four small Z-plasties, each equal in size to a quarter of the single Z-plasty, they can be compared from the point of view of lengthening and shortening.
The single Z-plasty achieves 2 cm of lengthen-ing and at the same time there is 2 cm of shorten-ing in the transverse axis. In the multiple Z-plasty, each of the four Z- plasties achieves 0.5 cm of lengthening with a corresponding 0.5 cm of shortening at each transverse axis.
The lengthening which occurs is in series and consequently is additive, giving an overall lengthening of 2 cm, while the shortening is in parallel, and remains 0.5 cm at each Z. The amount of lengthening achieved by each is thus the same, but the shortening has been greatly reduced by the use of the multiple Z-plasty. Many clinical situations exist where a Z-plasty could be used to advantage, but the tissues cannot stand 2 cm of shortening, though they could tole-rate 0.5 cm with ease, and for these the multiple Z-plasty is a possible solution.
The change from single to multiple Z-plasty also alters the form of the lateral tension. From being concentrated in the line of the transverse limb of the single Z, it is spread over the several transverse limbs of the multiple Z-plasty in addition to being reduced. These differences have obvious advantages from a vascular point of view.
In the multiple Z-plasty, as in the single Z-plasty, the theoretical lengthening is probably unattainable. Quite apart from the effect of scarring, etc., there tends to be some loss of Ieng thening in passage from one Z to the next. Nevertheless the comparison between the two, and the advantages of the multiple over the single, are still valid.