You can get a job in Canada while you're still in Nigeria by checking jobbank.gc.ca, and narrowing down your search to temporary foreign employers with LMIA.
Another way you can get a job in Canada is through study pathway; by applying to further your degree in the country and when you're done with your degree, you will be eligible to apply for a post graduate work permit and that will enable you get a job in the specified field.
These two schools: George brown college of applied Arts and Technology in Toronto and British Columbia Institute of Technology offers a post graduate diploma in Prosthetics and Orthotics.
Note: check the Canada immigration official website (cic.gc.ca) to get more information if you decide to go through the school route.
All the best.
Bordering countries, like Canada, tend to have more lenient requirements for bordering countries. Keep that in mind.
I recommend checking with your local embassy located in the country you plan on living - in this case Canada. Speak to their consular section or the part that handles visa requirements. Tell them of your desire to work in that country and ask them what the visa requirements are.
You can also contact their embassy, in this case Canada, within your home country and ask them the same questions. Tell them about your situation and they can give you the information too.
Best of luck!!