The Psychological Inflexibility in Pain Scale (PIPS) assesses both avoidance of pain and cognitive fusion with pain.
Reference:
Wicksell, R. K., Renöfält, J., Olsson, G. L., Bond, F.W. & Melin, L. (2008). Avoidance and cognitive fusion - central components in pain related disability? Development and preliminary validation of the Psychological Inflexibility in Pain Scale (PIPS). European Journal of Pain, 12, 491-500.