Can I use the phrase "annually" instead of "every year"?
Yes, I believe you can use "annually" instead of "every year" here. However, you would have to change the sentence slightly for the sentence to make sense. It would have to be "Thousands of Canadians lose a limb annually." Ex: We go on a camping trip every year. = We go on an annual camping trip. Ex: The convention takes place in Los Angeles every year. = The convention takes place annually in Los Angeles.