# Medical Devices for Tremor Suppression: Current Status and Future Directions
## 4 Wearable Orthoses
### Passive Suppression  
Tremelo utilized two tuned vibration absorbers (TVAs) that are positioned over the dorsal and ventral surfaces of the arm (Figure 3). Each TVA contains a mass-spring-damper system in which the vibration energy of involuntary motions of the shaking arm during tremor are transferred from the spring to the added mass. This results in reduced tremulous movements and substantial motions of the added mass within the TVA. This device is purely mechanical, eliminating the need of a power source. Preliminary results showed an 85% tremor suppression in a patient with PD tremors [115]. Recruitment for a pilot clinical study is ongoing, which should provide further data. Steadi-One is mechanical device that integrates a tuned mass damper (TMD), which obviates the need for a power source [116] (Figure 4). Like TVAs, the TMD embodies a mass-spring-damper system. The difference between TMDs and TVAs is the presence of a dissipating element, which, in Steadi-One, is a non-Newtonian fluid in the interior space of the TMD. When the vibration energy is transferred to the added mass, this non-Newtonian fluid becomes viscous, reducing its amplitude of motions. There are no publicly available data to support its efficacy. However, it is claimed ([[https://www.steadiwear.com](https://www.steadiwear.com)]([https://www.steadiwear.com](https://www.steadiwear.com)), accessed on 26 March 2021) to have an 85-90% tremor suppression during the lab simulation. The Readi-Steadi glove embeds a multitude of metal disks that aims to add inertia to the tremulous hand. A preliminary study involving 40 participants who were healthy or with ET observed a 50% tremor suppression [117]. The metal disks function as sensory tricks that influence the aberrant sensorimotor integration to suppress tremor. While there is no study that examines the effectiveness of the sensory trick phenomenon in patients with ET or PD tremor, it has been studied in 30 patients with musician's dystonia [118]. Figure 4: Steadi-One passive orthosis. The non-Newtonian fluid within the tuned mass damper of Steadi-One (Steadiwear, Toronto, ON, Canada) becomes viscous when the vibration energy of tremor is transferred to a mass-spring-damper system, acting as a dissipating element that reduces the amplitude of motions. Figure 3: Tremelo passive orthosis. The vibration energy of tremor is being transferred to a mass-spring-damper system within the two tuned vibration absorbers of Tremelo (Five Microns, Fresno, CA, USA), positioned over the dorsal and ventral surfaces of the arm to counteract the involuntary motions. By wearing a glove, patients with more severe symptoms of dystonia showed better improvements in fine motor control (Pearson's r = \(-\)0.45; \(p\) = 0.01) [118]. The Task-Adjustable Passive Orthosis (TAPO) has a textile glove design to enhance wearability and comfort for daily activities. An air-filled structure, inflated on-demand by hand or electrical pump, is fitted within the glove on the dorsal surface of the hand. The inflated TAPO applies pressure to the back of the hand and the forearm, suppressing the involuntary motions in the wrist flexion/extension, ulnar/radial deviation, and pronation/supination. The proof of concept of TAPO has been examined in a patient with PD tremors performing six ADLs. The use of TAPO was associated with a significant tremor suppression in three specific tasks, including 82% while drinking (\(p\) = 0.03), 79% while pouring (\(p\) = 0.03), and 74% while drawing a spiral (\(p\) = 0.03) [119]. More recently, [PERSON] and [PERSON] examined and established a mechanical model for particle damping for passive vibration suppression in tremors [120]. Particle dampers involve the potential of energy absorption and dissipation through momentum exchange between moving particles and vibrating walls. There are several advantages of using particle dampers, including simple construction, low cost, robustness and reliability, wide damping frequency band, and insensitivity to extreme temperature [120].