Arndt, Alexander Roediger, Kevin Korona and Ben Heber flipped over at high speed onto their side in a curve during their first run. The German suffered a cut, bruises and suspected concussion.
Walther and his team of Andreas Bredau, Marko Huebenbecker and Christian Poser were fastest in the first run and quick enough in the second to win in 1:48.11, edging Latvia's Oskars Melbardis, Daumants Dreiskens, Arvis Vilkaste and Janis Strenga by four hundredths of a second.
Switzerland's Rico Peter, Janne Bror van der Zijde, Thomas Amrhein and Simon Friedli were third, 0.67 seconds back.
Two Canadian sleds finished in the top 10.
Justin Kripps of Summerland, B.C., Ben Coakwell of Saskatoon, Joey Nemet of Hamilton, Ont., and Bryan Barnett of Edmonton were seventh, 1.22 seconds back. Calgary's Chris Spring, Alexander Kopacz of London, Ont., Derek Plug and Joshua Kirkpatrick, both from Calgary, were 10th, 1.55 seconds behind.
"The boys all did well today and put in a really tough effort," said Canadian coach Tom De La Hunty. "It is very encouraging to have both sleds in the top 10. That means you are in the mix and anything can happen. But we are suffering big time on the start and we must work on that."
With files from The Canadian Press.