The SNAP Trial: SPRINT® Peripheral Nerve Stimulation for the Treatment of Neuropathic Post-Amputation Pain

Question 9 of the Brief Pain Inventory-Short Form (BPI-9) is a 7-part question that assesses the level of interference that subjects experience in their daily lives due to pain. The 7 categories are general activity, mood, walking ability, normal work, relations with other people, sleep, and enjoyment of life. Subjects were asked to rate how much their post-amputation residual and/or phantom limb pains interfere with each aspect on an 11-point numerical scale where 0 represents "Does Not Interfere" and 10 represents "Completely Interferes." The average of these 7 scores was calculated for each subject at each time point. Percent reduction was then calculated for each subject's qualifying region of pain (residual limb and/or phantom limb pain with qualifying average pain intensity at baseline). To be considered a success, subjects must have experienced ≥ 50% reduction in all qualifying regions of pain compared to baseline. The number of successes is presented.

The Pain Disability Index (PDI) is a validated survey measuring the degree to which pain disrupts 7 categories of life activities on a scale from 0 to 10, with higher scores indicating greater disability. The 7 scores were summed for each subject to provide an overall pain disability score ranging from 0 to 70. A score of 0 indicates no disability while a score of 70 signifies that all of the activities in which the individual would normally be involved have been totally disrupted or prevented by pain. To be considered a success, subjects must have a ≥ 10-point reduction in their total PDI score at each time point compared to their baseline score. The number of subjects successful at each time point is reported.

The Patient Global Impression of Change (PGIC) Survey asks subjects to rate their improvement with treatment on a 7-point scale ranging from -3 to 0 to +3, where -3 represents "very much worse," 0 is "no change," and +3 represents "very much improved" as compared to before stimulation treatment. The subjects combine all the components of their experience into one overall score. The mean rank score of each group was calculated for each time frame.

The Pain Catastrophizing Scale (PCS) questionnaire has 13 questions that assess rumination, magnification, and helplessness. Subjects are asked to think back on painful experiences in the past and reflect on how often they had specific thoughts or feelings. Each of the 13 questions is scored on a 5-point scale where 0 represents "not at all," and 4 represents "all the time." The scores from each question were summed for each subject to provide a total PCS score, with a possible range from 0 to 52 with higher scores indicating a greater tendency to catastrophize pain (i.e. a higher score indicates a worse outcome). The mean score for each time point is presented.

Subjects completed 7-day diaries in which they tracked their daily use of analgesic medications. Opioid analgesic usage was converted into a morphine equivalent dosage (MED), which is measured in units of morphine milligram equivalents (MME), for subjects who were using opioid analgesics at baseline. The average MED was calculated for each subject at each time point.

All subjects were asked to complete daily diaries to record their average residual limb pain and/or phantom pain intensities during the past 24 hours on each day of a 7-day period using an 11-point numerical rating scale where 0 represents "No Pain" and 10 represents "Pain as bad as you can imagine." The average pain scores were calculated across the 7-day period for each region of pain at baseline and across weeks 1 to 4 post-start of treatment (i.e., the first half of the 8-week treatment period). Percent reduction was then calculated for each subject's qualifying region of pain (residual limb and/or phantom limb pain with qualifying average pain intensity at baseline). To be considered a success, subjects must have experienced ≥ 50% reduction in all qualifying regions of pain compared to their 7-day baseline diary average pain score(s). The number of successes is presented.

All subjects were asked to complete daily diaries to record their average residual limb pain and/or phantom pain intensities during the past 24 hours on each day of a 7-day period using an 11-point numerical rating scale where 0 represents "No Pain" and 10 represents "Pain as bad as you can imagine." The average residual limb pain scores were calculated across the 7-day period at baseline and for weeks 5 to 8 post-start of treatment (for subjects with qualifying residual limb average pain intensity at baseline). Percent reduction from baseline was then calculated, and the number of subjects that experienced ≥ 50% reduction in residual limb pain are reported.

All subjects were asked to complete daily diaries to record their average residual limb pain and/or phantom pain intensities during the past 24 hours on each day of a 7-day period using an 11-point numerical rating scale where 0 represents "No Pain" and 10 represents "Pain as bad as you can imagine." The average phantom limb pain scores were calculated across the 7-day period at baseline and for weeks 5 to 8 post-start of treatment (for subjects with qualifying phantom limb average pain intensity at baseline). Percent reduction from baseline was then calculated, and the number of subjects that experienced ≥ 50% reduction in phantom limb pain are reported.

All subjects were asked to complete daily diaries to record their average residual limb pain and/or phantom limb pain intensities during the past 24 hours on each day of a 7-day period using an 11-point numerical rating scale where 0 represents "No Pain" and 10 represents "Pain as bad as you can imagine." The average pain scores were calculated across the 7-day period for each region of pain at baseline and at 3, 6, and 12 months post-start of treatment. Percent reduction was then calculated for each subject's qualifying region of pain (residual limb and/or phantom limb pain with qualifying average pain intensity at baseline) at each time point. To be considered a success, subjects must have experienced ≥ 50% reduction in all qualifying regions of pain compared to their 7-day baseline diary average pain score(s). The number of successes is presented.