You can work as little or as hard as you want. If you want details you need to talk to multiple ortho docs in varying practice environments.
For myself, starting my third year of practice, I work a four day week. Two full days in the office and two full days in the OR. I go in around 7:15 am and on clinic days I am home by 5:30 and on OR days I am usually home by 4:00 pm. So roughly, I work about 40 hours each week, but you must also add the four days of month of call I take which adds a few hours in there. So probably no more than 45-50 hours per week, unless I have a weekend of call. Now I practice where reimbursement is still fairly good, except Medicare, so we don't work as hard as docs in other areas of the country. I also chose my practice knowing that I would have a full day off every week. Many of my friends do not, so their hours are probably more. Also, my friends who practice where reimbursement is lower tend to work alot more hours, running longer clinics to make the same amount of money.
The question comes down to how much money do you want to make? The more you work, the more you get paid in most practices. If you want to make more than $500,000/yr, you're going to need to work everyday of the week and log in long days. If you are happier with $350,000 then you'll be home for dinner every night and may even have a day off every week. So as I said before, it is what you make of it. There is a job out there for everyone's lifestyle. You just have to pick the group right that allows you to practice and to work as hard or as little as you like.