B Nguyen, N Baicoianu, D Howell, KM Peters, KM Steele (2020) “Accuracy and repeatability of smartphone sensors for measuring shank-to-vertical angle” Prosthetics & Orthotics International

Journal Article in Prosthetics & Orthotics International

Example of how the smartphone app was used for this research. The top images show a black smartphone attached with a running arm band to the side or front of the shank - the two positions tested in this research. The middle figure shows the placement of the reflective markers for 3D motion analysis to evaluate the accuracy of the smartphone measurements. Markers were placed on the lateral epicondyle of the knee, lateral maleolus of the ankle, tibial tuberosity, and the distal tibia. Blacklight was used to mark the position of each marker and hide the position from the clinicians. The bottom panel shows screenshots from the app. The first screen is used to align the device and has arrows at the top and bottom that remind the clinician which anatomical landmarks should be used to align the device while displaying the shank-to-vertical angle in real time. The second screenshot shows an example of the calculated shank-to-vertical angle while someone was walking. The average is shown with a bold black line, with all other trials shown in blue and excluded trials (e.g., when someone was stopping or turning) that deviated more than one standard deviation from other trials are shown in red. There is also text below the graph that provides summary measures, like shank-to-vertical angle in mid stand and cadence (steps/min). The results can be exported as a picture or sent via e-mail using the app.
A) Smartphone positioning on the front or side of the shank. B) Reflective markers on the the tibial tuberosity (TT) – distal tibia (DT) and lateral epicondyle (LE) – lateral malleolus (LM) were used to compare the accuracy of the smartphone to traditional motion capture. UV markings were used to keep placement of these markers constant while blinding clinicians. C) Sample screenshots of the mobile application, including the set-up screen and results automatically produced after a walking trial.

Background

Assessments of human movement are clinically important. However, accurate measurements are often unavailable due to the need for expensive equipment or intensive processing. For orthotists and therapists, shank-to-vertical angle (SVA) is one critical measure used to assess gait and guide prescriptions. Smartphone-based sensors may provide a widely-available platform to expand access to quantitative assessments.

Objectives

Assess accuracy and repeatability of smartphone-based measurement of SVA compared to marker-based 3D motion analysis.

Method

Four licensed clinicians (two physical therapists and two orthotists) measured SVA during gait with a smartphone attached to the anterior or lateral shank surface of unimpaired adults.  We compared SVA calculated from the smartphone’s inertial measurement unit to marker-based measurements. Each clinician completed three sessions/day on two days with each participant to assess repeatability.

Results

Average absolute differences in SVA measured with a smartphone versus marker-based 3D motion analysis during gait were 0.67 ± 0.25° and 4.89 ± 0.72°, with anterior or lateral smartphone positions, respectively. The inter- and intra-day repeatability of SVA were within 2° for both smartphone positions.

Conclusions

Smartphone sensors can be used to measure SVA with high accuracy and repeatability during unimpaired gait, providing a widely-available tool for quantitative gait assessments.

Try it out!

The app for monitoring shank-to-vertical angle is available for you to download and use on either Android or iOS smartphone. Please complete THIS SURVEY which will then send you an e-mail with instructions for installation and use. This app is not an FDA approved medical device and should be used appropriately.

NBC Learn: Exoskeletons and Engineering

NBC Learn logo for the Discovering YOU series - engineer your world. Supported by NSF, Chevron, and ASEE.

We partnered with NBC Learn to share some of our work on exoskeletons to help encourage students to consider a career in engineering. What can be more exciting than musculoskeletal modeling, exoskeletons, horses, and stuffed animals?

Check out the video – a lesson plan will also be posted soon for classrooms to use.

Go team!

ISB 2019 Recap

Five members of our lab – Kat, Michael, Alyssa, Megan, & Nicole – attended ISB 2019 in Calgary, Canada. The International Society of Biomechanics promotes and supports international contacts amongst scientists, the dissemination of knowledge, and the activities of national organizations in the field of biomechanics.

Four individuals stand in hallway smiling at conference.

Our work at the conference included:

Kat Steele: ISB presentation on in-clinic EMG monitoring for muscle activity and movement in acute care in the initial days after stroke.
Michael Rosenberg: ISB poster showcasing how individuals’ kinematics and muscle activity change in response to ankle exoskeleton stiffness during acceleration from standing. ISB presentation on open-loop modeling of response to ankle exoskeleton torque during walking.
Alyssa Spomer: ISB poster highlighting how motor control is impacted when typically developing individuals emulate cerebral palsy gait patterns. ISB poster on understanding how individuals can alter motor control expression using visual biofeedback.
Megan Auger: ISB presentation on how muscle coordination strategies in typically developing children and children with cerebral palsy are not accurately captured using standard musculoskeletal modeling optimization algorithms in computer simulation.
Nicole Zaino: ISB presentation on spasticity reduction via rhizotomy in children with cerebral palsy and how there was no significant difference in the change in energy consumption when compared to a control group of children with cerebral palsy who had no rhizotomy.


TGCS 2019

Additionally, two members of our lab – Michael & Megan – attended TGCS 2019 in Canmore, Canada prior to ISB 2019. The Technical Group on Computer Simulation (TGCS) is a scientific and technical meeting for investigators and students in all areas of computer simulation in biomechanics. This group was a highly-focused subset of the ISB community, primarily focusing on forward simulation of unimpaired and pathological gait patterns, but also touching on multi-scale simulation, diving, cycling, and wheelchair use. 

A mountain view in Canmore, Canada with sharp jagged peaks and a bright blue lake.
Michael standing in the front of a room in between two screens giving a presentation.
Michael Rosenberg: TGCS presentation on Dynamic Mode Decomposition for modeling response to ankle exoskeletons during gait.

US Patent Office Visit

Patent examiners spend their days critically evaluating the latest innovations, to determine if they are useful, novel, and non-obvious. When one of our students asked them what daily life is like as a patent examiner they responded, we basically write a 10-15 page report every 2-3 days.

Thankfully the patent office lets them escape from behind their computers a few times a year to meet with companies, research labs, and other entities. These visits help them see what is new and exciting in their specialty area.

We were lucky enough to host one of these teams this past week in the AMP Lab. Tim Stanis, a primary examiner from Art Unit 3786 that specializes in exoskeletons, orthoses, passive motion rehabilitation devices, and biomechanical technology led the visit. He was joined by nine other examiners.

One of the patent examiners in a red checkered shirt answers students questions. He is seated at a table with hands clasped in front of him.

Our lab demoed our latest creations in orthoses, biofeedback systems, and smartphone sensing. Patrick Aubin from the VA Hospital, Murray Maitland from Rehab Medicine, Chet Moritz from Electrical Engineering, and Tapo Bhattacharjee also shared their latest work.

We ended the session with a Q&A Panel for summer students to learn about career opportunities as a patent examiner and advice for new innovators. Most of the examiners had an undergraduate or master’s degree in engineering. They emphasized that working for the patent office is a great, flexible career path. As a patent examiner they are able to work remotely, have flexible hours, and enjoy other benefits such as having law school paid for.

Students listen attentively to the Q&A Panel. Some look bored, some look amused, and one is even taking notes, or maybe doodling!

For new innovators, they emphasized the importance of understanding the patent landscape. They recommended using Google Patents! Patents can seem intimidating. They recommended starting with the pictures and focusing on the claims. They also emphasized the importance of having a team. Translating technology requires team members with technical, business, and clinical backgrounds.

For our part, we were excited to meet real, live patent examiners. We appreciated seeing their faces and enjoyed sharing our work with them.