Part 2- Pain Therapy Options: A patient-based outcome review of pain management devices

In Part 1 of this article, we featured the description and performance of the Willow Curve Smart Laser device. In part 2, we’ll discuss a patient-based outcome review of pain management devices, including the Quell and VibraCool.

January/February 2019 – Practical Pain Management Journal

Tiziano A. Marovino DPT, MPH, DAIPM                                         Michael Majewski, BAA, CSCS

Chief Health Strategy and Innovation Officer                                               Research Associate

Biogenesis Group, LLC                                                                                       TLC Group

Ypsilanti, MI                                                                                                          Ypsilanti, MI

This device review focuses on technologies that have emerged over the past few years which aim to benefit patients suffering from persistent pain, as well as infuse some innovation into home-based chronic pain management. The current healthcare economy and milieu in general relies on patients passively receiving clinical services, making the directionality of healthcare provision from the home to the hospital or clinic. With healthcare reform and the anticipated transition from volume- to value-based care, the clinical community will need to give greater thought to filling the post-discharge void regarding pain relief typically associated with on-site services. If reimbursement models change to reflect a greater pay-for-performance model based on out­comes, whereby providers are paid commensurate with clinical effectiveness, this trend may incentivize caregivers/providers to consider improved home-based pain management, includ­ing the judicious use of durable medical equipment (DME).

The devices featured represent just a sampling of a much larger trend that may transform healthcare delivery in the near future, including transitions from expensive inpatient settings to less costly outpatient settings, and eventually into the home. In the current complex healthcare ecosystem, hav­ing the ability to leverage the right technology for individual patients moving forward will be paramount. In addition, having access to a cohesive evidence-informed home care plan for conservative chronic pain management will be vital to total care coordination when it comes to ensuring positive outcomes. The three technologies highlighted herein are sleek, cleverly designed, and, in the authors’ view, have demonstrated medical-grade pain management at a fraction of the price.

Data Methods & Analysis: Quantifying Patient Improvement

This mixed-methods analysis utilized patient-reported out­comes and provider research with quantitative endpoints. The goal was to determine how each device worked and in which patients it worked best. The authors used a traditional odds ratio (OR) statistic to measure effect size, since ORs do not require intensive computation. In our design, the OR was simply the ratio of two probabilities: the probability of achieving the outcome of interest vs the probability of not achieving the outcome of interest. In a conventional case/control design, the subjects would be chosen based on the presence or absence of disease. In our clinical setting, the subjects were chosen based on the presence or absence of pain. Using classic OR convention, the cases and the controls represent two different groups and differ only by disease status.

When pain intensity is used as the primary endpoint, one may actually have the pain at one point in the day and not have pain in another part of the day (diurnal variation). In this modified OR format, we used the same group of patients as both the cases and the controls, taking advantage of fluc­tuations in pain status. By doing so, we have avoided many of the confounding factors that require statistical adjustment. However, by not implementing the same level of internal control(s) as a formal clinical trial, the data can only infer association and not causation between outcome and expo­sure variables.

Product Evaluation

Since the three devices reviewed do not require medical prescription, our primary outcome measure of interest was patient-reported pain intensity reduction using a 10-point visual analog scale (VAS). These three devices were presented to us at different times of the year in 2018. The Willow Curve (phototherapy) and Quell (electrostimulation) devices were tested for 8 and 11 months, respectively, while the VibraCool (vibrational) device was tested over a period of 3 months (received in October 2018). We applied a single subject design (multiple N of 1) that examined the change in pain intensity based on a single treatment session where the patient acted as his or her own control with the desired outcome of interest being a 3-point reduction in a 10 point (10 cm) VAS scale.

As clinicians know, it is important to be reminded that pain intensity is but one characteristic in the total pain experience of any patient and does not necessarily explain co-existing disability. The use of a pain VAS instrument as a surrogate to measure disability is not ideal as it simply measures a single dimension of the pain experience: pain intensity. However, the VAS has been shown to compare favorably to multi-item scales, showing good concurrent validity (SF-20), responsiveness, and excellent reliability. In fact, while common forms of pain intensity assessment have shown excellent test-retest reliability, the VAS has the smallest error associated with its use.

Product protocols were followed according to device instructions and verified through numerous communications.

Description & Performance of the Devices

Product: Quell

Manufacturer: NeuroMetrix, Inc. (Waltham, MA)

Recommended for pain conditions such as: systemic pain such as fibromyalgia, polymyalgia, generalized age-related stiffness, muscle strain, cramping, and spinal pain

Cost: $299*

*Please contact your MeyerPT Account Manager at the number below for Professional Pricing.

This technology is an electricity-based, TENS-like wearable unit cleared by FDA as a Class II (safety standard) medical device (see Figure 2). It is worn mid-calf regardless of pain location or condition and acts as a peripheral nerve stimula­tor whose mechanism of action (MOA) invokes the widely accepted spinal gating theory, along with stimulation-induced release of endogenous opiates as the primary mechanism. This device may be worn during sleep and/or activity since it is firmly secured to the stimulation site with a strap. Quell is well described by Gozani (2015).

Another nice feature of the Quell is that its battery life lasts for 4 to 7 days and only takes a few hours to charge. The actual output power in this unit is quite high at 100 V x 100 mA, with the user able to adjust these settings when needed. The waveform is described by the manufacturer as a symmetric biphasic 60 to 100 Hz changing frequency pattern, which is very important in preventing accommodation. In fact, waveform is often understated and underappreciated; it has been the authors’ experience that electrostimulation devices that lack this characteristic often have limited analgesic effects and usage due to central nervous system (CNS) adaptations.

Quell’s technology allows for the device to calibrate to the individual with optimal stimulation patterns, which is an impressive feat and consistent with today’s Smart technology. The Quell also comes with an app that can capture and store patient data, serving to increase patient compliance through engagement and insight.

Figure 2. Quell device on mid-calf

Editor’s Note: NeuroMetrix recently released Quell 2.0, an updated version that includes an option for shorter 15-minute ses­sions, coaching features, and new machine learning algorithms that take into account different char­acteristics tailored to the user. According to the manufacturer, Quell 2.0 is 50% smaller and 20% more powerful than its predecessor.

We issued the unit to patients for 3 to 4 weeks at a time where they agreed to use the unit for 2 to 3 sessions per day at 60 minutes or more if needed. Quell was trialed on mostly neuropathic and myopathic conditions, and due to the nature of the trial parameters, it took considerably longer to capture data. The Quell database (obser­vation points) is not as extensive as the other two technologies, but despite less empirical data, Quell performed admirably overall and became a favorite among patients.

Product: VibraCool

Manufacturer: PainCare Labs, LLC (Atlanta, GA)

Recommended for pain conditions such as: enthesopa­thies, ligamentous, musculotendinous, localized myalgia, and capsular pain

Cost: $70 to $90

The VibraCool (see Figure 3) provides an intervention that is a combination of ice and vibration, oscillating at 150 Hz and small enough to fit most anywhere on the body. VibraCool is a focal vibration device that is strapped on the body where needed. It provides a 10-minute continuous treatment to most any peripheral joint (we have even tested the device on painful sacroiliac joints). The vibratory frequency uti­lized targeted pain-specific receptors (mechanoreceptors) and nerve pathways that might further activate the spinal gating mechanism(s). Vibration (whole and/or focal) is being used therapeutically to reduce muscle atrophy, improve joint active range of motion (AROM), and reduce joint pain.



Figure 3. VibraCool on ankle

The authors found the VibraCool device to be a valuable adjunct to our clinical treatments, especially for very difficult-to-treat enthesopathic conditions that in many cases are unresponsive or recalcitrant to other forms of energy or manual therapies. These observations were consistent with the inherent predilection that vibration energy might have on ligamentous, capsular, and musculotendinous struc­tures based on the high concentration of mechanoreceptors found in collagen-based tissue. Patients showed both high compliance and tolerance for using the VibraCool device; chronic pain patients who had some hypersensitivity to general tactile stimulation did fine with the unit.

Our younger sports medi­cine patients (knees, ankles, and shoulders) responded exceptionally well to this form of treatment, but it was diffi­cult to discern whether this was related to a more youthful neurophysiological response, stimulation preferences, psy­chological factors, or some other variables introduced and influ­encing the treatment dynamic. There certainly was a tendency for younger patients to prefer being treated while they were exercising (dynamic treatment) versus older patients who seemed to prefer a more passive treatment post-exercise.


The technologies described are unique from each other and represent divergent technologies with convergent goals. They are a good example of how many different ways one may achieve cost-effective pain control. When used on a regular basis, these devices have demonstrated that they can modulate both acute and chronic pain and could make excellent home pain management options. Pain practitioners may want to consider adopting these devices for clinical use as well, or at least so that patient trials may be conducted in-office to determine response and whether a medical order for the device is warranted.

Since this investigation was not set up as a comparative effectiveness trial, we will report the global modified OR for the combined devices (Quell, Willow Curve, and VibraCool). The OR for the pooled data is 2.25 with a 95% CI (1.34 – 3.77) and a z statistic (3.077), all at a significance level (P = 0.0021).

Our data suggest that these diverse devices are effective at ameliorating pain intensity and are proof that there are many ways to peel the proverbial onion.

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