Sliderboard (The Ohio State University)

Jaime Bravo, Matt D’Errico, Marija Ilievska, Jessica Russo, Maria Talarico  

ABSTRACT

Stroke is one of the leading causes of long-term disability in adults, often resulting in an impaired gait or inability to walk altogether. One method of restoring a natural gait is by increasing a client’s range of motion using an assistive device. Due to the limited availability of gait rehabilitation specific devices in the clinic setting, we proposed a design for a new range of motion rehabilitation device (sliderboard). Unlike current devices being used for clinical therapy, such as furniture movers and the ProFitter board, the sliderboard allows for anterior/posterior, lateral/medial motion, and circular motions in a controlled and constrained manner. Preliminary EMG testing showed that the sliderboard was activating the correct muscle groups during use. The devices were used in a clinical setting for several weeks and received positive feedback from both the clients and the physical therapist himself.

CLINICAL BACKGROUND

Stroke, one of the leading causes of long-term disability in adults, results from damaged brain cells due to a lack of blood supply to the brain or hemorrhage into the brain tissue. Stoke results in neurological motor deficits leading to disability and handicap in about 90% of survivors(1). These motor deficits greatly impact a person’s life, especially in gait performance. Approximately 80% of people who have had a stroke lose their ability to walk independently and 33% may require assistance or supervision to walk within three months post-stroke (2). Since walking independently is a significant aspect of everyday life, gait rehabilitation leading to improved walking ability is a priority for survivors of a stroke. Rehabilitation aims to eventually improve the overall gait cycle through motor learning, task-specific and context-specific training, high-intensity task-oriented practice, and impairment focused programs, such as muscle strengthening, muscular re-education with support of biofeedback, and stimulation of the neuromuscular pathways effected (3).  The primary issue is the lack of neural control of the muscles, but there are limited devices accessible for therapists to use in the clinic that specifically aim to improve neural control and range of motion (ROM).

In other clinics there has been a push to use treadmills for the rehabilitation of clients recovering from a stroke.  It has been proven that treadmill training increases brain activity in the affected hemisphere (4); however, the downfall to treadmill training is that the client is just reacting to the treadmill, and they are not generating the force necessary to walk independently. Sometimes the clients can master walking on a treadmill, but they fail when walking on the ground because they do not know how to generate their own force, only how to move their legs in response to a mechanical stimulus.

PROBLEM STATEMENT

A major issue in the full recovery of gait by clients is the limited amount of meetings their insurance will allow them to have with their physical therapist. If a device existed at a low enough cost to allow the client to own it and perform the exercises at home, it would allow for the therapy sessions to be more spread out and allow the therapist to guide the client through a larger percentage of their overall recovery, greatly increasing the chances for rehabilitation success.

Therefore, we have proposed the development of a new range of motion rehabilitation device, from now on referred to as sliderboard, designed to help the client regain a natural gait. The end goal is to help a person walk independently again by developing motor learning skills and creating new neural pathways between the patient’s brain and their muscles. The sliderboard’s design requires the client to generate their own force and movements, instead of reacting to an outside stimulus.

DESIGN OBJECTIVES

The clinic we worked with, located in Martha Morehouse Medical Plaza, resorted to using devices designed for other applications to exercise the patient’s ROM. For example, the physical therapist that oversaw our project used a device originally designed to teach people how to ski (the ProFitter) and furniture movers.  The ProFitter was used for linear motion exercises; the curved base, which allows it to rock while in use, and unsecured footplate, that would occasionally pop off the track, were huge safety concerns for the clients and took their focus away from the exercise.  Additionally, the furniture movers could not be confined to a circular path so clients could complete the exercise without activating the target muscle groups (primarily the adductors and abductors). In order to create a device that addressed the needs discussed above, the following objectives were identified to guide us in the design process:

  • Safety
    • Pieces of device should not detach while in use.
    • Ability for sudden movements to occur should be limited.
    • Clients should feel safe when using the device.
    • No sharp edges.
    • Low profile; close to ground.
  • Stability
    • Base of device should not move while in use.
    • Should not move during mount/dismount.
    • Accommodates patients up to 300lbs and size 16 shoe.
  • Portability
    • Device weight < 50 lbs.
    • Easily stored in clinic.
  • Simplistic Design
    • The client will supply all the energy to create the movements.
    • ROM’s can be switched easily and quickly

DESIGN AND DEVELOPMENT

Materials

The tracks were made of high density polyethylene (HDPE), which allowed for a light-weight, low-friction surface. We used an automated CNC machine to mill out the features into a 2’x5’ piece of plastic to create the linear track. The linear footplates were made out of wood, with a plastic piece attached to the bottom. The circular track’s base was a 32″x36″ sheet of HDPE and the footplates were constructed primarily from HDPE and PVC (polyvinyl chloride) pieces.

Linear Track

Figure 1: CAD model of the sliderboard's linear track

The linear track offers both medial/lateral and anterior/posterior motion through the use of interchangeable footplates. Linear motion is achieved through plastic on plastic sliding by moving the footplate in the desired direction. The length of the track allows for extension in one or two directions, depending on where the user stands. The perpendicular grooves serve to house a hard stop, at various positions along the track, to limit motion should the physical therapist or patient find it necessary. This design for the linear track has proven to be simple and effective.

 

Circular Track

Figure 2: CAD model of the sliderboard's circular track

Circular motion required a different design to account for the added complexities. The footplate would be designed to allow movement via plastic-on-plastic sliding, just like the linear footplate. However, the circular base does not use a milled trough to confine the motion. Instead, the footplate, a rigid rod, and fixed pivot point work together to confine movement to a circular path. For simplicities sake, we decided to make the footplate and rod as one constructed piece that could easily be swapped out in its entirety. Footplates with different rod lengths can easily be swapped out to match the patient’s ability. Turf was applied to the base and the footplates to designate where the patient should stand and, more importantly, add grip where the patient would be standing.

RESULTS AND DISCUSSIONS

Friction Test

Figure 3: Testing to determine the coefficient of friction for plastic on plastic sliding

To provide appropriate resistance settings for both tracks, we wanted to match the resistance of the devices that were previously being used in the clinic. We tested the Pro Fitter device, the furniture mover, and our plastic on plastic sliding using an S-load cell. Using the S-load cell force readings, the coefficients of friction were determined and we saw that the sliderboard devices matched the predicate devices’ coefficients of friction.

Client Surveys

To record client feedback after using the sliderboard devices, surveys for both the linear and circular tracks were given to the physical therapist. The linear track was in the clinic for a longer period of time and we have already received very positive feedback from the clients and the physical therapist. We have yet to receive client surveys for the circular track but the preliminary feedback from the physical therapist has been positive.

EMG Test

Figure 4: Example EMG wave data

The primary muscles used for the ROM access and balance required for our devices are those of the quadriceps muscle group, the gastrocnemius, and the soleus.  In order to prove that the sliderboard activates these muscles, the 5 members of our team each performed exercises on the circular device while being connected to an electromyography (EMG) system (BioPac PRO).  Calibration was done for the activation associated with max voluntary activation, and then the EMG results were constructed as percentages of maximum activation.  The hamstring muscle group will be referred to as the thigh and the gastrocnemius and soleus will be combined into a muscle group referred to as the calf.

EMG testing revealed that for the case where the patients’ center of gravity is consistently above their stance leg, the thigh is always activated more than the calf and the stance leg is always activated more than the moving leg.  It was also found that the legs are cyclically loaded, resulting in the majority of activation being seen when the foot is between 90° and 270° away from the initial start position (normal stance width).  This is primarily caused by the need for the user to bend his or her stance leg in order to reach the outer edge of the circular path with the other foot.

Our results from this test confirm that the targeted muscles are being activated.  It also provides evidence that the exercise is low resistance, as the moving leg is not greatly taxed.  This means that survivors of a stoke should be able to complete the exercise, even having limited muscle recruitment and strength.  Finally, there was also evidence that shows an increase in muscle activation exists when a larger exercise radius is used.  This confirmed the ability for the device to have multiple levels of difficulty, allowing the device to be effective for a client during a larger portion of their rehabilitation.

Figure 5: Shows our starting point and where the majority of the muscle activation took place

 

Figure 6: Graph showing the average percentage of muscle activation for each circular path

CONCLUSIONS AND FUTURE WORK

We proposed the development of a range of motion rehabilitation device to help a client regain their natural gait. After completing various tests on the device and getting feedback from actual clinical use, we believe that the sliderboard could provide a cheaper and more effective alternative to devices currently used for range of motion rehabilitation. The feedback we received from the clinic was invaluable during our design process and while designed with clients recovering from a stroke, at its core the sliderboard is a device for ROM rehabilitation and could benefit any client with an abnormal gait or limited/impaired joint movement.

Before the sliderboard is ready to be produced on a wide scale, there are still some final adjustments that need to be done. With production quality materials and machining, the circular footplates can become thinner and closer to the ground, which would reduce the height difference that is currently in place. Production-grade equipment could also minimize the amount of pieces of the footplates for both the linear and circular tracks. A different material with a lower coefficient of friction or better wear properties could be used in place of HDPE to make a better product.

ACKNOWLEDGMENTS

We would like to thank Adam Spitznagle, physical therapist at Martha Morehouse Medical Plaza, and Dr. Mark Ruegsegger, our engineering advisor, for informing us on the problem, and working with us to propose a solution. Thanks to Robert Jones, David Lee, Isaac Kennedy and Will Estep for their help during the fabrication process. Also, thanks to the Department of Biomedical Engineering at The Ohio State University for funding our project.

REFERENCES

  1. Hesse, Stefan (2003). Rehabilitation of Gait after Stroke: Evaluation, Principles of Therapy, Novel Treatment Approaches, and Assistive Devices. Topics in Geriatric Rehabilitation19, pp. 109 – 126
  2. Richards, Carol L. (2008). Gait Rehabilitation after Stroke.  2nd National Stroke Conference.
  3. Belda-Lois, Juan-Manuel et al. (2011). Rehabilitation of gait after stroke: a review towards a top-down approach.  J Neuroeng Rehabil 8, p. 66.
  4. Enzinger, Christian et al. (July 2009). Brain activity changes associated with treadmill training after stroke. Stroke 40.7, pp. 2460–2467.

 

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