Board Thread:Naruto Discussions/@comment-24824859-20150716001406/@comment-5407586-20150716045950

Kabuto basically rejuvenated Madara's Edo Tensei body (Edos are revived at the age they died) and gave him Hashirama's face on his chest (or maybe it was Hashiface that rejuvenated Madara, like Gyūki's chakra did to Nagato). Doing so also empowered Madara's Wood Release almost to Hashirama's level without Sage Mode. Edo Madara's Rinnegan wasn't the result of Kabuto's experiments (as Madara himself stated). When Madara was truly revived, his true body probably was decomposed to the point it couldn't return to life (since it was 15-20 years since he died), while the Rinnegan did not; so one could say that Madara's Edo body became his true body while the fake Rinnegan vanished into dust.