The team says a special diagnostic scan on its leader turned up a broken bone in his left palm from an injury sustained in Stage 2 on July 5.
An X-ray right after the crash didn't show the full extent of the damage.
Karpets said in a team statement before Tuesday's ninth stage that he had trouble holding the handlebars and "in such conditions it be no sense to continue."
Karpets took home the best young rider's jersey at the Tour in 2004, and after Sunday's eight stage was 57th - 26 minutes, 1 second behind race leader Cadel Evans.
Other riders to drop out on Monday's rest day included Markus Eibegger, Simon Gerrans, Roger Kluge and Fabio Felline. There are now 180 riders left out of the 197 who started.
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