Here is a breakdown of the study results:
Type of surgery % reporting significant pain
prior to surgery 6 months post-op 12 months post-op
Knee replacement 84 39 38
Breast surgery 0 20 18
The presence of memory impairment and/or executive function disorders predicted which individuals experienced post operative pain. These persons had findings on brain MRI that indicated some abnormalities of areas where the pain signal processing AND memory/executive function are located.
From the results of this study, it appears that there is some ability to forecast the risk of post operative chronic pain--simply by knowing the patient's mental functional ability. It's potentially a powerful tool in the war on chronic pain, don't you think?