Abstract

Osteoarthritis (OA) is a progressive degenerative disease that commonly affects the knee joint. Current non-surgical interventions have low rates of efficacy, and many individuals who suffer from OA are not candidates for surgical interventions. Thus, there is a significant need for effective non-surgical treatments. Roam has developed a novel non-invasive smart knee orthosis (Ascend) to alleviate the pain associated with knee OA. The purpose of this study was to evaluate the ability of Ascend, a smart knee orthosis, to impact the symptoms of knee osteoarthritis, primarily activity limiting knee pain and instability, by comparing subjects’ baseline condition to their performance of activities of daily living while wearing the Ascend orthosis.  Specifically, a chair stand test (CST) and a stair test were performed while using a pain scale to assess knee pain. During this study, participants' pain scores were reduced by a clinically significant 48% during CST test and 47% for stair test. In addition, 67% of participants demonstrated an increase in functional outcome measures during the CST and stair tests. The results of this study provide strong indication of Ascend being a safe and effective non-invasive treatment for those suffering from knee OA, and a viable alternative to costly, higher risk surgery.

Introduction

Background

Affecting approximately 30 million Americans, [1] osteoarthritis (OA) is the most common chronic joint condition and the leading cause of disability in middle-aged to older adults in the United States [2]. Globally, the age-standardised point prevalence and annual incidence rate of OA in 2017 showed an increase of 9.3% (95% UI 8% to 10.7%) and 8.2% (95% UI 7.1% to 9.4%) from 1990, respectively [34]. Currently, OA accounts for $128 billion per year in direct and indirect medical costs in the U.S. [3, 4, 5]. Additionally, the middle-aged population (below the age of 55) will end up living more years with a disease for which there is no known cure [6]. With 14 million Americans suffering symptomatic knee OA [7], the knee is the joint most commonly affected by the disease. A stable and pain-free knee joint is essential for mobility, yet the Centers for Disease Control and Prevention report that among individuals with arthritis, 11 million find it hard to walk more than short distances, 8 million have trouble climbing stairs, and 6 million are limited in their social activities [8]. When these functional movements become difficult or painful, patients often become less mobile and suffer decreased quality of life associated with the comorbidities of obesity, hypertension, depression, and diabetes [9]. Increased physical exertion has been shown to be a significant predictor of improvement in life satisfaction [10] and increased psychological well-being [11]. Once conservative treatment methods have been exhausted, surgical intervention is the next option for individuals suffering from knee OA. However, many individuals decline or put off surgery which leads to a gap in treatment. Furthermore, when examining the Quality Adjusted Life Year (QALY) for many treatments for knee OA, the cost of these treatments exceed the dollar amount for which patients are willing or are able to pay [12]. There is a clear need for a clinically viable, affordable, and effective form of non-surgical intervention to treat patients suffering from symptomatic knee osteoarthritis.

Objective

The aim of this study was to evaluate the ability of Ascend, a smart knee orthosis, to impact the symptoms of knee osteoarthritis, primarily activity limiting knee pain and instability, by comparing subjects’ baseline condition to their performance of activities of daily living while wearing the Ascend orthosis. The knee orthosis (KO) prototype used in this research provides powered support to the user via extension and flexion moments generated by a pneumatically powered actuator on the orthosis, controlled by a SmartPack worn by the user. The SmartPack contains both the pneumatic and electrical power for the orthosis as well as the microcontroller which runs the system and allows the device to perform intent recognition style control. Our hypothesis is that the additional support provided by the pneumatic actuator of the device will relieve pain and improve stability for individuals experiencing symptoms of knee osteoarthritis.

Methods

Research Design

This study utilized a single-arm experimental design with patient-reported outcome measures (PROMs) collected before and during testing appointments.

Recruiting

Approval was obtained to conduct a human research study from the Ethical & Independent Review Services (082119). Potential participants were recruited via online advertisement and asked to complete a web-based questionnaire. For inclusion, subjects were required to have activity related knee pain or activity limited by knee pain, ability to ambulate without the use of an assistive device (use of a cane was acceptable), and were older than the age of 18. Individuals who have undergone a total knee arthroplasty (TKA) on either knee, experienced lower extremity trauma within the last 6 months, experience flexion contracture in the knee and/or hip joint in excess of 10° and/or knee varus/valgus malposition in excess of 10°, experience moderate to severe spasticity, possess a leg length discrepancy in excess of 2" and/or lower extremity amputation, or the inability to communicate clearly verbally or complete questionnaires in English were excluded from this study. Additionally, to fit with the Ascend prototype design, individuals weighing greater than 250 lbs and those who are shorter than 5' or taller than 6’6'' were also excluded.

Participants who completed the survey, and met the aforementioned criteria, were contacted to schedule a 90-minute testing appointment following a phone screening. The phone screening served to ensure participants were comfortable with the testing process, confirm previously determined eligibility, and elaborate on any necessary medical history. Eligible applicants were scheduled on a first come first basis with a total participation goal of 80 participants.

Testing Protocol

Each participant attended a single 90 minute appointment onsite at the testing facility of Roam Robotics (manufacturer of the Ascend orthosis in San Francisco, CA), for an evaluation session which included three phases, (1) participant intake, (2) baseline functional outcome measures wearing no device, and (3) device fitting and repeated functional outcomes testing using the Ascend orthosis prototype. Participant intake included study and data collection consent, the Knee Injury and Osteoarthritis Outcome Score (KOOS) [13, 14] and the Activities-Specific Balance Confidence (ABC) Scale [15,16] to assess baseline function, and a survey of current pain levels as well as confirmation of medical history with testing staff. Both the KOOS and ABC scales are validated for this population, which is why they were chosen for this research. For all consequent testing, participants were asked to evaluate their pain for that activity using the Wong Baker FACES [17,18,19], a 0-10 scale where a score of 10 represents the largest amount of pain. Additionally, participants were asked to assess their confidence, stability and use of aids for each functional test.

The first functional outcome test performed was the 30-second chair stand test (CST), performed on a 17” high chair [35]. The second function outcome test performed was a stair test using a single flight of twelve uniform steps. Each test was conducted twice: first as a baseline wearing no device and a second time using the Ascend orthosis prototype. Prior to each test with Ascend prototype, participants were allowed to practice the maneuver and select the level of support provided by the orthosis that would then be used for the test. Once each baseline functional outcome test was completed, participants were fitted with the Ascend orthosis prototype. Any necessary fitting adjustments to the orthosis were made by the study staff throughout the testing process. Immediately following each individual test, participants' were asked to report a pain score, differences in confidence, stability and use of aids for each functional test. Additionally, differences in functional ability, gait, and/or use of aids during each functional test observed by the study staff were recorded. For the CST test, aids were defined as the participant's use of a cane or hands to push off the chair or legs during the test. During the stair test, aids were defined as the use of a cane or hand rail during the test.

Results

Participants who completed the study were on average 57 years old and diagnosed with OA, post-traumatic OA, or experienced symptoms which present as OA. Study participant demographics are shown in (Table 1). The KOOS and The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain scales provided validate baseline metrics for subject-perceived pain, specifically for a population with knee osteoarthritis. At baseline our subjects reported a 54 (SD 3) average score on KOOS Pain and a 40 (SD 16) average score on WOMAC pain. KOOS scores are typically reported on a 0-100 scale, with 0 reflecting the most severe knee disease and 100 indicating no knee problems on a traditional orthopaedic assessment. WOMAC scores are also reported on a 0-100 scale with the inverse, a score of 100, indicating high knee disease severity. These baseline scores validate that the tested population have symptoms aligning with severe knee problems [20].

A majority of participants reported or demonstrated a reduction in pain and/or improved performance while completing the functional tests using the Ascend prototype compared to baseline testing (no device). For the CST, 78% (n=63) of participants reported a reduction in knee pain with an average pain reduction of 47% which represents a clinically significant average change of 2 points (Table 2; 4.2 to 2.0; mean difference of 2.2; 95% CI 1.6-2.4, P<0.001). Participants who reported a higher baseline pain score of 5-10 points (n=20) showed on average a greater reduction in pain compared to those who reported a lower baseline pain score of 0-5 (n=61) during the CST test (figure 3a). During the Stair Climb Test, 69% of participants reported a reduction in pain while using the Ascend prototype (n=54) with an average reported pain reduction of 47% (Table 2; 4.4 to 2.1; mean difference of 2.3; 95% CI 1.6-2.5, P<0.001). Participants who reported a higher baseline pain score of 5-10 points (n=24) showed on average a similar reduction in pain compared to those who reported a lower baseline pain score of 0-5 (n=54) during the stair test (figure 3b). Across the study, participants reported an average pain reduction of 47%. Additionally, 67% of participants reported or showed improvements in functional outcomes across the CST test and the stair tests. The functional outcomes included confidence, stability, compensation between legs, and/ or reduced use of aids. 35% percent reported an increase in confidence, 27% reported an increase in stability, and 10% demonstrated a reduction in the use of aids during CST specifically. The data collected during the stair test specifically proved to be too noisy to break down into specific functional improvement categories.

Discussion

Osteoarthritis (OA) is a degenerative disease with a spectrum of treatment options ranging from conservative measures to invasive joint replacement surgery. Conservative care can include patient activity modification, weight loss, physical therapy, bracing, pain medication, and steroid injections [21,22]. Minor surgical procedures such as arthroscopic lavage and debridement are other treatment options but have shown to have poor long term efficacy [23,24]. Once these more conservative interventions have failed, total knee arthroplasty (TKA) is the last remaining option. Typically, a patient experiences OA symptoms for 9-12 years before choosing surgical intervention [25,26,27]. However, a significant number of these patients refuse surgical interventions completely due to perceived high risk or reluctance to undergo surgery in general [28, 29]. This unwillingness or inability to undergo surgery leads to, at best, a gap in treatment and, at worst, a failure to provide treatment at all. The patients in the treatment gap typically endure symptoms for an average of 20 years, and up to 40 years for the younger population [30]. The most concerning group are the younger patients for whom the arthroplasty survival is shorter [31], and studies have found that 86.8% of surgeons are less likely to perform these surgeries on these patients [32, 33]. This study demonstrates how the Ascend orthosis prototype can improve functional mobility, reduce pain scores for adults who fall within the treatment gap in a clinical setting.

During this study, participants' pain scores were reduced by a clinically significant 48% during CST test and 47% for stair test. In addition, 67% of participants demonstrated an increase in functional outcome measures during the CST and Stair tests. Participants also reported increased confidence and stability during the CST and Stair tests. The reductions in knee pain and increase in functional outcome measures during these tests indicate a potential increase in participants’ overall mobility and quality of life.

We acknowledge that there are limitations to this study. As the braces used in this study were from a library of pre-made orthoses, not custom fabricated uniquely fit to each subject, the fit of the orthosis was not ideal for participants. The overall fit of the orthosis did have an impact on its ability to function properly. While we aimed to mitigate this for each participant, custom fabricated braces tailored to each individual’s unique anatomy, ensuring proper suspension and alignment of the powered joint to a subject’s anatomical knee joint, should lead to better outcomes. Participants with formal OA diagnosis or symptoms that strongly suggest the presence of OA, experience a substantial within-day range of pain [36]. Appointment times were scheduled on a first come first serve basis according to subject availability and were not optimized for when participants experienced the most pain. We did not control for gait speed; all subjects were told to walk at their preferred gait speed. For the CST test, this did not impact the outcome for the participant. However, during the stair test participants who used a slower gait speed were supported better by the orthosis than those who opted for a faster speed. It is known that an individual’s preferred speed is dependent on many factors such as time of day, current pain level, and motivation. Each appointment lasted approximately 90 minutes in total with a small portion of that being with the use of Ascend. It is possible that with more time using the orthosis, participants would become more familiar with the device and experience improved outcomes. Despite the limitations of the current study, it demonstrates the ability of the Ascend orthosis to reduce pain during activity, improve functional movement, and increase stability.

Conclusion

In conclusion, this study of 81 participants who suffer from diagnosed OA, post traumatic OA, or symptoms which present as OA, demonstrated the ability of the Ascend prototype orthosis to provide significant improvement in participants' pain during CST and the stair climb tests. In addition, participants reported increased confidence, stability and ability to perform activities of daily living without the use of assistive aids while wearing the device. This study provides strong indication of Ascend being a safe and effective non-invasive treatment for those suffering from knee OA, and a viable alternative to costly, higher risk surgery.

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