Force Plate Measurement System for Physiotherapy

"The entire system was delivered to St Vincent’s Hospital with the exact features, specifications, and user interface required by the customer at around half the price of available off-the-shelf force plate measurement systems."

- Karina Taylor , EnvisEng Pty Ltd

The Challenge:

EnvisEng set out to provide a system that consistently measures and analyses human balance on one leg to assess the progress of patients under their rehabilitation treatments to regain mobility.

The Solution:

Utilising NI’s compact and modular CompactDAQ platform, EnvisEng delivered a custom-built hardware and software analysis system to St Vincent’s Hospital Physiotherapy Department at a lower price point than any off-the-shelf force plate measurement system.

EnvisEng is an NI Partner in Sydney, Australia, that specialises in scientific and medical applications of LabVIEW-based data monitoring, analysis, and control. The founder of the company is a Certified LabVIEW Architect, a Certified Professional Instructor, a physicist, and an electrical engineer with many years of experience in project management and software development.

The Musculoskeletal Outpatient Physiotherapy Department at St Vincent’s Hospital provides rehabilitation treatments to its patients. Physical therapists needed a method of consistently measuring human balance on one leg, over multiple physiotherapy sessions, to assess patients’ responses to their prescribed exercise programs. Off-the-shelf force plate measurement systems were prohibitively expensive to St Vincent’s Hospital, which needed only a subset of the features in these systems. St Vincent’s had a small but specific list of requirements that could easily be met using a simple NI data acquisition solution.

Application Overview

EnvisEng designed and built a custom hardware and software analysis system for St Vincent’s Hospital using the NI cDAQ-9181 single-slot Ethernet chassis with an NI 9237 four-channel bridge/strain measurement module. This compact, Ethernet-connected DAQ product provided the most simple, accurate, and cost-effective solution for the customer.

The 750 x 750 mm force plate itself was fabricated out of steel. A load cell was placed in each of the four corners of the force plate. The top plate that the patient stands on was covered with a non-slip flooring laminate for safety and aesthetics.

The NI data acquisition hardware and power supply were housed in an electrically safe enclosure adjacent to the instrument, which was connected to the mains power and monitoring PC via Ethernet. The whole setup is like an accurate, industrialised Wii-fit style balance board.

The software application written in LabVIEW has the following high-level features:

Multiple test modes:
- Single leg balance
- Repeated knee bends on one leg
- Calf raise
- Hop
Simple and intuitive test procedure with a real-time balance plot and overall balance “score”
Balance “score” that is calculated by the software based on the overall width and height of the figure drawn by the movement of the centre of mass in the relative XY plane over the duration of a test
Patient-based data files recorded in a human-readable file format
Comparison mode that compares a patient’s current test results with past test results

Application Benefits and Conclusion

The entire system was delivered to St Vincent’s Hospital with the exact features, specifications, and user interface required by the customer at around half the price of available off-the-shelf force plate measurement systems.

Because the system is based on a modular DAQ platform and custom-built software application, the customer has the option to expand the capabilities of the system as needed in the future. This may include more detailed analysis features, additional test modes, and increased weight ratings. The possibilities are endless.