Make sure you can get your feet flat on the floor and be comfortable sat upright in that position (some good lower back support helps). I broke my pelvis, snapped my coccyx off and had compression fractures in my lumbar vertebrae last year (as well as fractures in both knees, breaking my left humerus and fracturing/dislocating my right thumb). After all that, I needed something comfortable to sit on!
My solution was to continue using the really crappy beat-up wooden chair I found in a skip over 20 years ago, but I added a 1" pressure relieving cushion (e.g. like you find in wheelchairs) and use a pillow to support my lower back. Most comfortable thing I've ever sat in (the pressure relieving cushions are really amazing).