Electrical Stimulation for the Treatment of Pain Following Total Knee Arthroplasty Using the SPRINT Beta System

Average Knee Pain Over the Last 24 Hours

All subjects were asked to complete daily diaries to track their average pain intensity during 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.

Time frame: Postoperative Day 0 to 28 (first 4 weeks following Total Knee Arthroplasty (TKA))

Average Knee Pain at Rest

All subjects were asked to complete daily diaries to track their average pain intensity at rest during 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.

Time frame: Postoperative Day 0 to 28 (first 4 weeks following Total Knee Arthroplasty (TKA))

Pain Right Now as Measured by the Brief Pain Inventory

Subjects were asked to rate their pain right now on an 11-point numerical scale where 0 represents "No Pain" and 10 represents "Pain as bad as you can imagine." The median score for each time point is reported. Baseline is considered Visit 2a (Lead Placement) for Treatment Group subjects and Visit 2b for Control Group subjects. For Treatment Group subjects for Visits 3, 4, 6, and 8, pain right now was assessed while peripheral nerve stimulation was on for at least one Lead. For Visit 4, the score reported during the last in-hospital day was used.

Time frame: Baseline (Visit 2a/2b), Visit 3 (Day of Total Knee Arthroplasty (TKA)), Visit 4 (in-hospital), Visit 6 (2-weeks post TKA), and Visit 8 (4-weeks post TKA)

Amount of Analgesic Usage

Subjects recorded the amount/type of analgesics used in daily diaries. Narcotic usage was converted into morphine milligram equivalents (MME). Diaries were collected at various visits and were translated into post-operative days. The average MME was calculated for each subject for the first 28 days (4 weeks) following surgery, and the median of these averages across subjects was determined. If subjects had ceased opioid use (per the Recovery Milestones log), then missing scores following the date of opioid cessation were replaced with 0 MME. If diary entries were missing but the subject had not yet reported opioid cessation, then the missing value was replaced with the mean usage of the available days for the corresponding week. Subjects missing data from one or more entire diaries (i.e., weeks) and had not yet reported opioid cessation by the date of any missing diary were not included in this analysis.

Time frame: Visits 5-8 (weeks 1-4 post-Total Knee Arthroplasty (TKA))

Number of Subjects That Experienced at Least One Opioid-Related Side Effect

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 considered Adverse Events. The number of subjects that experienced at least one opioid-related side effect at each visit is reported. Baseline is considered Visit 2a (Lead Placement) for Treatment Group subjects and Visit 2b for Control Group subjects.

Time frame: Baseline (Visit 2a/2b), Visits 4-11 (in-hospital days through 12-months post-Total Knee Arthroplasty (TKA))

Timed Up and Go (TUG) Test

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.

Time frame: Visit 1 (Baseline), Visit 4 (In-Hospital), Visit 6 (2-weeks Post-Total Knee Arthroplasty (TKA)), Visit 8 (4-weeks Post-TKA)

Six Minute Walk Test (6MWT)

The total distance that a subject could walk in 6 minutes was recorded, and subjects unable to walk at all were given a score of 0 meters. The median distance was then determined across subjects. 6 Minute Walk Test distances are expected to be reduced immediately after surgery as compared to baseline.

Time frame: Visit 1 (Baseline), Visit 6 (2-weeks Post-Total Knee Arthroplasty (TKA)), Visit 8 (4-weeks post-TKA)

Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)

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. The mean total score was then calculated across subjects for each time point.

Time frame: Visit 1 (Baseline), Visit 3 (Day of Total Knee Arthroplasty (TKA)), Visit 6 (2-weeks post-TKA), Visit 8 (4-weeks post-TKA), Visit 10 (3-months post-TKA), and Visit 11 (12-months post-TKA)

Number of Subjects Reporting Meaningful Improvement, Minimal or No Change, or Meaningful Worsening on the Patient Global Impression of Change (PGIC) Survey

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." Ratings of Minimally Improved, No Change, or Minimally Worse are considered "Minimal or No Change."

Time frame: Visits 3-11 (Day of Total Knee Arthroplasty (TKA) through 12-months post-TKA)

Pain Catastrophizing Scale (PCS)

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.

Time frame: Visit 1 (Baseline), Visit 8 (4 weeks post-Total Knee Arthroplasty (TKA)), Visit 10 (3-months Post-TKA)

Time to Meet Recovery Milestones up to Twelve Months Post-Total Knee Arthroplasty (TKA)

Participants were queried at each visit 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 met each milestone or through their completion of the study, whichever came first (up to twelve months post-surgery). For each milestone, the median number of days between the date of TKA and date to achieve the milestone was calculated.

Time frame: From Day of Surgery through completion of milestone or 12-months from Day of Surgery, whichever came first

Subject Satisfaction Survey

Subjects completed a sponsor-developed survey with questions pertaining to their feelings about the treatment they received following total knee arthroplasty (TKA) surgery. Treatment Group subjects were asked to report on their experience using the SPRINT Beta Stimulation System as a method for managing post-surgical pain. Depending on the question, subjects were asked to indicate their agreement with the question (strongly disagree, agree, neutral, disagree, strongly disagree), their comfort with the therapy (very uncomfortable, a little bit uncomfortable, fairly comfortable, very comfortable), or when pain relief was felt (immediately, a few minutes later, a few hours later, more than a day later or never). Responses are presented for Treatment Group subjects for key groups of questions related to the therapy whereby answer options are considered affirmative for strongly agree/agree, very easy/easy, very comfortable/comfortable.

Time frame: Visit 8 (4-weeks post-total knee arthroplasty (TKA))

Number of Physical Therapy Sessions Attended Following Total Knee Arthroplasty

Following discharge after total knee arthroplasty (TKA) surgery, subjects were asked to report how many physical therapy sessions they attended since the previous study visit. The median number of physical therapy sessions attended is reported for each group at each time point.

Time frame: Visit 5 (1-week post-Total Knee Arthroplasty (TKA)), Visit 6 (2-weeks post-TKA), Visit 7 (3-weeks post-TKA), Visit 8 (4-weeks post-TKA), Visit 9 (2-months post-TKA), and Visit 10 (3-months post-TKA)

Subject's Use of Device (Compliance)

The hours of usage were recorded for each Lead (femoral and sciatic) from the SPRINT Beta stimulator throughout the study to assess the level of subject compliance with the peripheral nerve stimulation therapy. Treatment Group subjects were asked to use the device for up to 24 hrs each day. The stimulator provided the cumulative number of hours in use since the device was activated. For each timepoint for Treatment Group participants (subjects who received stimulation therapy), the median cumulative number of hours of use for each lead is presented for each timepoint.

Time frame: Visit 4 (In-Hospital), Visit 6 (2-weeks post-Total Knee Arthroplasty (TKA)), and Visit 8 (4-weeks Post-TKA)

Inpatient Pain Management Experience Survey (Pain Management During Hospital Stay)

Subjects completed a survey comprised of a subset of questions from the Hospital Consumer Assessment of Healthcare Providers and Systems to assess subject satisfaction with pain management during their time in the hospital for total knee arthroplasty surgery. Questions regarding experience with in-hospital pain management are reported below.

Time frame: 1-week post-Total Knee Arthroplasty (TKA)

Inpatient Pain Management Experience Survey (Pain Medicine During Hospital Stay)

Subjects completed a survey comprised of a subset of questions from the Hospital Consumer Assessment of Healthcare Providers and Systems to assess subject satisfaction with pain management during their time in the hospital for total knee arthroplasty surgery. The number of subjects that responded affirmatively to the following question are reported below: "During this hospital stay, did you need medicine for pain?"

Time frame: 1-week post-Total Knee Arthroplasty (TKA)

Inpatient Pain Management Experience Survey (Discharge Facility)

Subjects completed a survey comprised of a subset of questions from the Hospital Consumer Assessment of Healthcare Providers and Systems to assess subject satisfaction with pain management during their time in the hospital for total knee arthroplasty surgery. The question regarding discharge location following hospital stay is reported below.

Time frame: 1-week post-Total Knee Arthroplasty (TKA)

Inpatient Pain Management Experience Survey (Overall Rating of Hospital)

Subjects completed a survey comprised of a subset of questions from the Hospital Consumer Assessment of Healthcare Providers and Systems to assess subject satisfaction with pain management during their time in the hospital for total knee arthroplasty surgery. As part of this survey, subjects were asked to rate their hospital stay on an 11-point numerical rating scale where 0 represents "worst hospital possible" and 10 represents "best hospital possible." The median score for each group is reported.

Time frame: 1-week post-Total Knee Arthroplasty (TKA))