You might be able to use RecBoot. Here is some information quoted from their web site:
RecBoot is a free utility for Windows and Mac users which allow you to put your iPhone / iPod Touch in recovery mode easily. Its a
great utility for for those iPhone users who's iPhone Home or
Sleep/Wake button is not fully functional. Moreover this utility saves
you from learning the 3-4 steps of putting your iPhone into recovery
mode manually. Normally you need to put your iPhone into recovery mode
when your want to do a firmware restore.
Once you put it in Recovery Mode, you see a popup on your computer screen saying "iTunes has detected an iPhone in recovery mode". From here, you should be able to restore.