Take your saw and cut through the pelvis. Be very careful not to cut into the gut or the bladder. Then go back to the bottom of the ribs and use the saw to cut alongside the breast bone all the way up to the neck.
Why ? do so many people rip the deer wide open ??? I was always told by a butcher that the smallest opening is the best because any meat that is exposed to the air is basically wasted meat ! I start at the bottom and just make a cut up to the breast bone, no further. I NEVER cut thru the pelvic bone...I just cut the poop chute out from the rear of the deer, that way all that meat on the hind quarter is protected by the skin yet. It takes a time or two and a little practice, but once it's done properly, it gets easier.
My brother only makes a cut in the belly about 12" long and he gets everything out of there and very little wasted meat.