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Orthopedic and Rehabilitation Engineering

Orthopedic and Rehabilitation Engineering - Poster Session B

Poster K11 - Development and Evaluation of a Haptic Feedback Device to Aid Low Back Surgery Recovery

Thursday, October 24, 2024
2:45 PM - 3:45 PM EST
Location: Exhibit Hall E, F & G

Introduction:  Lower back pain is a significant issue among various populations due to the physical demands of daily activities and certain professions. Surgery is one method to address lower back pain. The postoperative protocols for low back surgeries typically limit trunk flexion, trunk rotation, and the maximum weight of objects that should be lifted while one is recovering from surgery. However, these protocols do not specify the restricted range of motion (RoM) for the recovery process, which may vary based on the type of surgery. Considering that following aftercare instructions is a key factor in surgical success, this work explores the development and testing of a haptic feedback system for patients recovering from low back surgery. The long-term goal is for the device to be used during physical therapy sessions and in the home/community environment during the recovery process.

Materials and

Methods:  The current prototype includes a microcontroller (Adafruit Feather Express STM32F405), an IMU (ISM330DHCX - 6 DoF), two vibration feedback coin motors (SparkFun), and a LiPo battery (Adafruit STM32F405), all mounted on an adjustable harness (Figure 1). The microcontroller processes IMU data to convert trunk flexion and rotation angles. When these angles exceed occupational standards for trunk flexion while lifting, the coin motors provide vibrotactile feedback. Data is recorded on an SD card for further analysis.
To validate the system, an experiment with two participants (without a history of lower back pain) was conducted as a proof of concept. Maximum lower back flexion and trunk rotation angles were measured using a goniometer and input into the code to set appropriate thresholds. Participants performed various activities of daily living (ADLs) at their own pace, including picking up an object from the floor, bending to open a mini fridge, rotating to open a cabinet, hanging a poster, pouring coffee, hanging a coat on a rack, and getting up from a recliner while reaching for an object. We hypothesized that pouring coffee, hanging a coat on a rack, hanging a poster, and opening a cabinet would be within the expected RoM, while bending to open the minifridge, picking an object up from the floor, and getting up from the recliner would exceed the expected RoM. Each activity was performed twice, totaling 14 trials. After each activity, participants rated their perceived lower back discomfort on a Likert scale (1: Comfortable - 4: Uncomfortable).

Results, Conclusions, and Discussions: The experiment aimed to evaluate the effectiveness of a haptic device in detecting trunk flexion and rotation during various ADLs. The Likert scale rating for all trials was 1, indicating that participants were comfortable performing the activities. The haptic feedback for most activities functioned as we hypothesized. Not all the activities or how the subject performed them were above the thresholds for movement; however, there were activities where they did receive haptic feedback, such as the cabinet activity, the medicine ball activity, and the poster activity, in which the threshold was exceeded when the subject rotated in the range of 32-35 degrees, which exceeded the threshold by 2-5 degrees. The activity in which the flexion threshold was exceeded was the coat rack activity, where the threshold was exceeded by 2 degrees in the second trial, so it’s not as noticeable. On the other hand, the medicine ball and mini fridge trials had the thresholds exceeded by ~10 degrees for both trials in each activity. Variability in task performance within participants occasionally meant that the device provided haptic feedback when unexpected. Tasks like opening a cabinet or hanging a coat demonstrated significant variations in movement patterns, suggesting the need for standardization of task performance to ensure consistent data collection. While natural movement strategies are crucial for realistic data, balancing this with standardized execution can enhance data reliability.
A noted limitation was the trunk rotation threshold, which was based on an equation and may not accurately reflect the range of motion for individuals recovering from low back surgery. Further research is needed to understand these restrictions better.
In conclusion, the proof-of-concept test results were encouraging. Future work will involve testing the device with a larger cohort of participants without low back injury or pain. The selected ADLs were effective but required refinement to balance consistency and natural behavior. Standardizing tasks initially, followed by natural performance, can provide comprehensive insights into posture and discomfort. Refining the trunk rotation threshold will enhance the device's applicability in general and therapeutic settings, aiding in better posture training and lower back pain management.

Acknowledgements (Optional):  The authors would like to acknowledge the Hope College Department of Engineering for sponsoring this work.