frogza

Change the angle of the pullup. Instead of doing straight up and down, try setting a chair a few feet away from the bar, rest your feet on the chair and start doing your pullups. It won't hit your lats the same way normal pullups would but it will work several of the "support" muscles. Since the weight won't be as high you should be able to do a few more. Slowly work your way to the real thing.