To place realistic scars on any surface you can use the combination of maps.
Firstly there s a normal map which can be placed on any surface.
Than there s a psd file (scar_partition_layers.psd) with layered map. Use it to assign the partition, and decide upon specularity and stuff
The preview images are pics rendered with map generated scar and the model.
There s also a source model in case you need polygonal geometry.
Please keep in mind that two UV channels are assigned to the model - one for stitches and one for surface