A similar question has been addressed in a previous post concerning this functionality in SimMechanics. The same workaround must be used in the current version of Simscape Multibody, which is the new name since the R2016a release. Here is a link to that post:
You will need to model the limits as input torques to the revolute joint and make that actuation conditional upon the joint position, such as 0 and 90 degrees.
