How to dpkg -i on broken system

[Ross Boylan <RossBoylan@stanfordalumni.org>]

My system got in a broken state in which it could not mount some
disks.  I had patched the evms libraries to correct a problem, and
then overwrote them with an updated Debian package (which
unfortunately lacked the patch).

I wanted to dpkg -i my_old.deb (that will work, even for a downgrade,
won't it?), but dpkg said
dpkg: unable to access dpkg status area: No such file or directory

The status area was on one of the evms disks.

I used dpkg-deb to unpack the .deb file and copied the single file I
needed over the newer one.  Is there a better way to do this?  Is
there any way to run dpkg -i when the directory it needs is gone?

Thanks.