I found this while reading Grady Booch's blog.
http://www-03.ibm.com/developerworks/blogs/page/gradybooch?entry=patents_gone_wild
I didn't see the images for the patent, but based upon the description it's a simple alternate index, perhaps doubly linked list that's discussed.
Nothing more than what I saw in a C class at AT&T back in the 1980's or which was probably discussed in Knuth's series(http://www-cs-faculty.stanford.edu/~knuth/taocp.html) , perhaps even in K&R's original C book (http://cm.bell-labs.com/cm/cs/cbook/).
Soon, we'll see a patent for a wheel issued I guess. The US Patent Office is amazingly behind the times on vetting real intellectual property vs. prior art.
Link to United States Patent: 7028023