No abstract

To fulfill the need for reliable and consistent medical training of the neurological examination technique to assess ankle clonus, a series elastic actuator (SEA) based haptic training simulator was proposed and developed. The simulator's mechanism (a hybrid of belt and linkage drive) and controller (impedance control) were designed to render a realistic and safe training environment. Benchtop tests demonstrated that the prototype simulator was able to accurately estimate the interaction torque from the trainee (average RMSE of 0.2 Nm) and closely track a chirp torque command up to 10 Hz (average RMSE of < 0.22 Nm). The high-level impedance controller could switch between different clinically encountered states (i.e., no clonus, unsustained clonus, and sustained clonus) based on trainee's assessment technique. The simulator was evaluated by a group of 17 experienced physicians and physical therapists. Subjects were instructed to induce sustained clonus using their normal technique. The simulator was assessed in two common clinical positions (seated and supine). Subjects scored simulation realism on a variety of control features. To expedite controller design iteration, feedback from Day 1 was used to modify simulation parameters prior to testing on Day 2 with a new subject group. On average, all subjects could successfully trigger a sustained clonus response within 4-5 attempts in the first position and 2-3 in the second. Feedback on the fidelity of simulation realism improved between Day 1 and Day 2. Results suggest that this SEA-based simulator could be a viable training tool for healthcare trainees learning to assess ankle clonus.

Spasticity is a hypertonic muscle behavior commonly observed in patients with multiple sclerosis, cerebral palsy, stroke, etc. Clinical assessment for spasticity is done through passive stretch evaluations of various joints using qualitative clinical scales, such as the Modified Ashworth Scale (MAS). Due to the subjective nature of this evaluation method, diagnostic results can have poor reliability and inconsistency. A few research groups have developed electromechanical training simulators of upper arm spasticity with the intent of providing healthcare students practical training opportunities. This paper presents a novel, purely mechanical (nonpowered) training simulator as an alternative design approach. This passive design utilizes a hydraulic damper with selectable viscous effect to simulate the speed-dependent spastic muscle tone and a Scotch-Yoke linkage system to create the “catch-release” behavior of spasticity. An analytical fluid model was developed to systematically design the hydraulic damper. The error residuals between model prediction and experimental damping force were found within ±2.0 N and percent errors within ±10% across various testing speeds (i.e., 250, 500, 750, and 1000 mm/min). The performance of the fully assembled simulator was tested under slow (ω ≤ 60 deg/s), medium (60 deg/s &lt; ω &lt; 150 deg/s), and fast (ω ≥ 150 deg/s) stretch speeds, where ω is the joint angular speed. Preliminary bench-top results suggested the feasibility of replicating five distinct levels of spasticity behaviors (MAS levels 0–4), where resistive torque increased with higher stretch speed and peak resistive torque ranged from 1.3 to 6.7 N · m under the fast stretch speed.

Spasticity is a common consequence of the upper motor neuron syndrome and usually associated with brain lesion, stroke, cerebral palsy, spinal cord injury, and etc. On the other hand, rigidity is a neuromuscular disorder often found in Parkinson’s disease patients. Both of spasticity and rigidity are characterized by abnormal hypertonic muscle behaviors that will cause discomfort and hinder daily activities. Worldwide, the estimated affected population of spasticity is around 12 million [1], and rigidity affects more than 10 million people [2]. Clinical evaluation of spasticity or rigidity involves personal assessment using qualitative scales, such as the Modified Ashworth Scale (MAS) or Modified Tardieu Scale (MTS) for spasticity and Unified Parkinson’s Disease Rating Scale (UPDRS) for rigidity. However, this evaluation method heavily relies on the rater’s personal experience/interpretation and usually results in poor consistency and low reliability. The goal of this design was to develop a quantitative measurement device that can be used to assist clinical evaluation of spasticity or rigidity. This portable device, the Position, Velocity, and Resistance Meter (PVRM), can be strapped around a patient’s limb to measure angular position, angular velocity and muscle resistance of a given joint while the patient’s limb is passively stretched by the clinician. Acquiring this quantitative data from patients will not only allow clinicians to make more reliable assessments but also help researchers gain additional insights into the quantification of spasticity and rigidity.

Patients with neuromuscular disorders such as Parkinson’s disease (PD), traumatic brain or spinal cord injury, or multiple sclerosis (MS) can develop different levels of abnormal muscle behavior (hypertonia) such as rigidity and spasticity [1], [2]. Hypertonia can affect different parts of the body such as upper or lower extremities. Symptoms include pain, increased muscle tone, spasms, and decreased functional abilities. Hypertonia can interfere with many activities of daily living, greatly affecting the quality of life in patients and causing anxiety, depression, and social isolation [2].