Certainly finances should be one consideration before deciding to pursue a career in medicine. Just don't make it the only consideration.
The amount of your loan payments will of course depend on how much you borrow and what the interest rate is. Unfortunately, the standard federal government loans (Stafford loans) have a variable interest rate and therefore it is always tough to determine exactly how much you would have to pay back. However, there is an interest rate cap, the interest does not compound while you are in school, there are various payback methods, and deferments are available.
Just to give you a worst case scenario as far as Stafford loans, I'll throw some numbers out there. Let us say you borrow the maximum unsubsudized Stafford loan each year, $38,500. The interest rate is 8.25 percent (currently it is less than half that). Upon completion of medical school, your total loan amount (including principal and accrued interest) would be about $186,000. Ortho is a five year residency, and therefore the interest would accrue for 60 months before you begin your ten year payback. This will yield a final principal loan amount of about $280,000. At 8.25 percent and a 10 year payment period, your monthly payments would be $3437 per month or a total of about $42,000 per year. According to salary.com (a poor resource for determining salary, but it is something) the median income for an orthopedic surgeon in the midwest is about $292,000 per year. Lets say after federal and state taxes, you are left with 40 percent or $116,000. Minus the $42,000 needed for loan repayment leaves you with $74,000 take home -- not too shabby (another way to look at is that you would still be making about $250,000 per year before taxes once you make your loan payments). And this is all worst case for the loan (probably one of the best cases for career choice as orthopedic surgeons make a killing). If you lower the interest rate to something a bit more reasonable (like 6.3 percent...the average of the past 6 years Stafford loan rates) your loan payments drop to about $2700 per month or $10,000 less per year than at the higher rate.
Right now is a nice time to borrow money (if you need it) as the rates are so low.