Known to me steps of reproduction:
1. Get wound.
2. lie on the ground, so the wall was right side.
3. Use self-treatment.
4. Get Hiead in the wall.
Video example: http://www.youtube.com/watch?v=1_N_6WKyTvE&feature=youtu.be
Or:
1. Get wound.
2. Sit in the crouch position, so the wall was right side.
3. Do self-treatment and during self-medication, turn your character with the mouse to the right.
4. Get Hiead in the wall.
Video example: http://www.youtube.com/watch?v=m5dEaZBPRR0