There have been other people who have had to self-amputate one of their limbs to extricate themselves. For example,
this article mentions Doug Goodale, a lobster fisherman from Maine used a knife to cut his arm off at the elbow after getting it caught in a winch, and
Bill Jeracki, a fisherman who in October 1993 used a bait knife to cut his left leg off at the knee after getting it trapped under a boulder while fishing in a stream in Colorado. Also in 1993,
Donald Wyman amputated his own left leg when it was not pinned down by a huge tree that fell on him while he was clearing timber. However, none of them received the media attention that Aron Ralston has received.