Electrical Stimulation for the Treatment of Pain Following Total Knee Arthroplasty (TKA) Using the SPRINT System

Subjects were asked to complete daily diaries to track their average pain intensity in the past 24 hours over a 7-day period on an 11-point numerical rating scale where 0 represents "No Pain" and 10 represents "Pain as bad as you can imagine." The average score for each diary period was calculated across subjects, and the mean score for weeks 1-4 is reported.

Subjects were asked to complete daily diaries to track their average pain intensity at rest in the past 24 hours over a 7-day period on an 11-point numerical rating scale where 0 represents "No Pain" and 10 represents "Pain as bad as you can imagine." The average score for each diary period was calculated across subjects, and the mean score for weeks 1-4 is reported.

The amount and type of analgesics used by subjects was recorded in daily diaries. Narcotic usage was converted into a morphine equivalent dosage (MED), which is measured in units of morphine milligram equivalents (MME). Diaries were collected at various visits throughout the study, and for consistency, these data were translated into post-operative days. The average MED was calculated for each subject for the first 42 days (6 weeks) following surgery, and the median of these averages was determined across subjects.

Throughout the study, subjects were asked if they experienced any side effects related to opioid pain medications. The occurrences of these side effects were recorded and were not reported as Adverse Events. The number of subjects that experienced at least one opioid-related side effect at each visit is reported.

Active range of motion (AROM; no assistance from clinical staff) and passive range of motion (PROM; assisted by clinical staff) was assessed with both stimulation on and off. The time that it took subjects to achieve the milestone of 90 degrees of knee flexion in their affected leg is reported.

Subjects began this test from a seated position in a standard chair and were timed while they stood up, walked to a marked point 10 feet away (at a normal, safe pace), returned to the chair, and sat down. Timed Up and Go (TUG) test times are expected to be greater immediately after surgery as compared to baseline.

The total distance that a subject could walk in 6 minutes was recorded, and the mean distance was determined across subjects. 6 Minute Walk Test distances are expected to be reduced immediately after surgery as compared to baseline.

The amount of time it took subjects to walk a fixed distance of 20 meters was recorded.

The Western Ontario McMaster University Osteoarthritis Index (WOMAC) questionnaire consists of 24 items that evaluate pain, stiffness, and physical functional disability. Each item is scored on an 11-point numerical rating scale from 0 to 10, where higher scores indicate greater pain, stiffness, and disability. For each subject, the scores from each of the 24 items were summed to calculate the subject's total score, with a minimum score of 0 and a maximum score of 240. Percent change from baseline was calculated for each subject at each time point (i.e., value at Visit 5 vs. Baseline rating, value at Visit 7 vs. Baseline rating, value at Visit 11 vs. Baseline rating, and value at Visit 13 vs. Baseline rating). The median percent change across subjects was determined. Negative values indicate worsening since Baseline, while positive values indicate improvement from Baseline.

Percent improvement = 100 x ([rating at each study visit]-[rating at baseline]) / [rating at baseline].

Subjects were asked to rate the degree to which their knee pain has interfered with 7 different aspects of their daily life on a scale from 0 to 10, with higher scores indicating greater interference. Those 7 scores were averaged for each subject to provide an overall pain interference score, with a possible range of 0 to 10 with higher scores indicating greater interference. The median score was then calculated across subjects.

The Patient Global Impression of Change (PGIC) asks subjects to rate their improvement with treatment on a 7-point scale ranging from "very much worse" to "very much improved" as compared to before their knee replacement surgery. The subjects combine all the components of their experience into one overall score. Ratings of Much- or Very Much Improved are considered Meaningful Improvements; similarly, ratings of Much- or Very Much Worse are categorized as Meaningfully Worse.

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 median scores were then calculated across all subjects.

Participants were queried weekly from the date of their Total Knee Arthroplasty (TKA) until they met specific, post-surgical recovery milestones. Participants were queried up through the time at which they meet each milestone or through their completion of the study, whichever came first (up to three months post-surgery).

Subjects completed a sponsor-developed survey with questions pertaining to their feelings about the SPRINT Stimulation System as a method for managing post-surgical pain.