There are two ways to do it.
1) If you can get a visa to the US, you can fly to the US with your US visa, get to the US/Canada land border and cross in a rental car, private car or on foot and take your chances at the border with your expired card. If they let you enter without reporting you for not meeting the residency requirements, you can stay in Canada for 2 years straight and this will put your PR status back in good standing. If they report you for not meeting the requirements, they will still let you enter but in that case, you have 30 days to appeal for your PR stating your health as a reason for not being able to meet the requirements. Include medical records.
2) You can apply for a PR travel document at a Canadian embassy in Europe where you are. You will have to tell them that you do not meet the requirements and why and hope they will let you keep your PR. If they deny you, you can appeal but if you lose the appeal, you lose your PR. If you get the travel document, you can return to Canada.
Personally, I think you have better chances with 1) because immigration officers often do not report people even if they should. By saying when you enter that yes, you know your PR card expired a year ago and you do not meet the residency requirements but you have a good reason, your medical reasons, they might not report you and that will save you the trouble of having to appeal for your PR and even if they report you, you will be in the same situation as if you had applied for the PR travel document to begin with.
