MacBook Pro doesnt boot after systemupdate / repairing volume doesnt work
You can try boot your mac in recovery mode (hold command+R while booting), open Terminal, and running fsck to rebuild the btrees that hold the information of your files and directories structure.

To rebuild the catalog btree:

fsck -d -r /dev/disk0s2


Rebuild extents btree:

fsck -d -Re /dev/disk0s2


Rebuild attributes btree:

fsck -d -Ra /dev/disk0s2


Replace "disk0s2" by the id of the partition you want to fix. You can find out what's the id by running
    diskutil list

"-d" means show debugging information. This can be very useful to understand what the error is.