HI, here is what I found to be the difference between your two codes
10140 - incision in the skin to decompress and drain a hematoma, etc. A hemostat bluntly penetrates the fluid pockets, allowing the fluid to evacuate, a drain may be placed, the incision may or may not be closed.
27603- Incision in the leg over the site of the hematoma, etc. Dissection is carried down throught the deep subq. and may be continued into the fascia or muscle to expose the hematoma, finally when the hematoma is identified it is incised and drained, irrigated and repaired in layers, or left open to continue to draining.
descriptions are taken from the 2008 coders' desk reference - Procedures
It will depend on how Deep the Incision is, skin level or further down.
Hope this helps,
Gina