View this excellent image of a fighting Anakin from the new AOTC Trading Cards. Warning: this is a great SPOILER!
If you want to read some speculations, here it is (SPOILER ALERT):
Apparently Anakin loses his arm in this battle, and not – according to the Expanded Universe novel Splinter of the Mind’s Eye – in a battle with Luke and Leia between A New Hope and The Empire Strikes Back. Yet another proof that Lucas writes his own story without caring for the stories of the other authors.