The screen is mounted on a round column.

If the column has internal structure that can be bolted to, any standard VESA wall mount would suffice (examples: Ergotron: Wall Mounts (http://www.ergotron.com/tabid/157/language/en-US/default.aspx)). Otherwise, metal clamps (http://www.hooksandlattice.com/sign-clamps.html) or straps used for street sign posts could possibly be adapted to a standard mount, or a specialty mount (http://www.peerlessmounts.com/dyn/Products/BrowseProduct.aspx/tn/241/u/t/categoryID/403) used. How big is the column and of what material and how pretty does it need to be?

Even if you manage to attach the LCD to the column, there is still the problem of routing power and signal cables neatly down or inside the column. The typical hack is to enclose the wires in a surface mount raceway which is attached to the column with foam backed adhesive tape which inevitably peels. A hanging ceiling mount (http://www.ergoindemand.com/ceiling-mounts-lcd.htm) avoids this problem and the human apes that would paw at the raceway and cables if the screen is located in a public venue.

On the other hand, if it is a strictly decorative column, most likely it is hollow, in which case, you can actually embed it into the column, fish your electric and low voltage upp through the column, and fabricate an acrylic cover or something similar th match the arc of the column so it doesn't look like there is a hole in it.