A great source for Yoga Postures by Mark Giubarelli.
Translation: Revolved Lunge Pose
From the Lunge posture above bring the opposite elbow over the front bent leg. Use the elbow to help in the rotation of the spine.
It may be tempting to bring the hands in line with the sternum. (In the middle of the chest.) If an enjoyable twist can be achieved then this will look better as far as alignment is concerned. It may be a better idea to place slightly higher. Feel the twist in the spine and stop when rotating if comfort is lost or if breathing becomes shallow and difficult.
It is easy for a posture to have negative effects if it is approached too aggressively. Finding gentle boundaries is usually more therapeutic and quite a refined art.
It is nice to blend the standing posture with spinal twists. Twisting the body many times in a yoga Vinyasa can result in a great freedom and looseness in the spine. As a result Shakti energy (energy that moves up and down the spine) can also move more freely.
Vinyasa Yoga postures to transition from and to: