Bailey won in 10.19sec, well outside his world record of 9.84, and edged fellow Canadian Bruny Surin into second place by 0.03sec.
Bailey said he was still having problems with his back, which he injured in the accident in Toronto. Asked how far he was from total fitness, he replied: "Oh man, I'm not even close.
"I'm not really happy with my time but in the circumstances I think I should be," he said. "My back is still hurting and it's difficult to come out of the blocks. I just wanted to get through this race and run."
Bailey said he had spent five hours a day on the treatment table during his four days in Rio and that back home a staff of 20 were working to get him back to full fitness.
"I hope that this season I can get healthier and that will make me faster," said Bailey, whose next race is in Qatar.
Earlier, Algeria's Olympic champion Noureddine Morceli had wiped the sleep out of his eyes and easily won the men's 1,500 metres in a race dominated by his country.
Victory was never in doubt once Morceli sped clear of the pack just after the bell as Algeria took three of the first four places. Morceli won in 3min 34.99sec, more than a second clear of Kenya's David Lelei, who closed the gap slightly down the back straight but never looked like winning.
"I expected to go a bit faster but it was very early," Morceli said of the 11.15 a.m. start. "I haven't raced at this hour for a long time."
The Kenyans were also out of luck in the 3,000 metres as Allan Culpepper and Marc Davis completed a one-two for the United States, with the East African nation taking four of the next five places.