World War I slaughtered and mutilated soldiers on a scale the world had never seen. It's little wonder that its vast numbers of returning crippled veterans led to major gains in the technology of prosthetic limbs.

Virtually every device produced today to replace lost body function of soldiers returning from our modern wars -- as well as accident victims, or victims of criminal acts, such as the Boston Marathon bombings -- has its roots in the technological advances that emerged from World War I.

The war, which began nearly 100 years ago, produced its own crop of bionic men. In previous wars, severely injured soldiers often succumbed to gangrene and infection. Thanks to better surgery, many now survived. On the German side alone, there were 2 million casualties, 64 percent of them with injured limbs. Some 67,000 were amputees. Over 4,000 amputations were performed on U.S. service personnel according to the U.S. Department of Veterans Affairs.