Maybe it happened to you to be as unlucky or careless as me and you dropped your SP on the floor. Or you slipped on ice and you dropped on your SP, that was in your pocked. Both happened to me.
Now my SP is bent slightly and has a chipped frame. So I asked how much does it cost to fix this at the SONY service: 100$. Now, thinking myself smart, I bought a frame from a seller on eBay. Frame is fine, good looking, nice finish quality, did not expect that from a 10$ frame.
But there's a problem: you can change the frame only and together with the digitizer. They are glued together! So don't make my mistake to buy the frame only if you have a broken, bent or chipped frame. Buy both the frame and digitizer already assembled. This guys seems to selling a decent product: http://www.ebay.com/itm/281204540953
Here are some videos about dissassembling Xperia SP:
Hope I helped somebody today