The Push-N-Go

Made by Rebecca Berman, Bethel Desta, Clarissa Shieh, Lauren Weil

Executive Summary

Problem:

Due to limited hand dexterity and low endurance, patients with rheumatoid arthritis and interstitial lung disease have difficulty operating standard assistive walking devices. Our client, Stephanie Groth, a physical therapist at the University of Chicago Medicine, asked us to devise a solution that allows patients to continue to walk independently without the assistance of others and remain active members of their community without the use of their hands.

Purpose and Requirements:

The purpose of the Push-N-Go is to provide a hands-free solution that allows patients with rheumatoid arthritis and interstitial lung disease to walk independently. The design should be safe, independently operated, and easily transportable.

Methodology:

Our team interviewed and met with Mrs. Groth and her patient to learn about patients’ experiences with rheumatoid arthritis and current solutions. In addition, we interviewed a teammate’s grandmother, who has limited hand mobility and uses a rollator and a bike shop, to learn about various brake systems. We built mockups to explore three concepts and tested them with Mrs. Groth.

Design:

Our design consists of ergonomic forearm attachments, palm supports, and a pressure-activated brake system. The user can move forward by applying weight from the elbows onto the forearm attachments. To brake, the user simply removes weight from the forearm attachments. These modifications allow the user to easily and independently control and brake the rollator without hand dexterity.

Figure 1: Prototype of design

Introduction

Many rheumatoid arthritis patients suffer from limited hand mobility due to painful, swollen, and stiff joints. Furthermore, patients often also have interstitial lung disease, impacting their endurance and ability to walk for long periods. Combined, These two conditions make it difficult for patients to operate standard rollator and walker devices that rely extensively on hand function. While the severity of rheumatoid arthritis differs between patients, this is a condition that typically worsens very rapidly (Appendix C). Patients can become homebound due to a lack of a solution that allows them to walk independently. Thus, our project task was to design a solution that would support patients with limited hand dexterity and low endurance in walking independently and remaining active community members.

The current walker and rollator solutions do not meet our clients’ needs. Standard two-wheeled walkers do not include a seat, which would allow users to take breaks. They also need to be picked up to move or pushed with two wheels dragging, and both of these actions require hand grip strength. While standard four-wheeled rollators typically have seats and are pushed along four wheels, they also require significant hand dexterity to operate. Using a rollator typically involves a squeezing motion to engage the brakes and a relatively firm hand grip to control the device, both of which are difficult for rheumatoid arthritis patients. Push-down brakes are currently the most popular hands-free brake system, but because users tend to put some body weight onto the forearm rests when walking with a rollator, the brakes can accidentally be engaged (Appendix C).

The Push-N-Go solves these problems by modifying an existing rollator’s brake system and forearm attachments. These forearm attachments span the user’s entire forearm and have palm rests at the end, allowing them to use their arm strength to control the rollator. Our design features a deadman brake system, in which the brakes are released when the user pushes down on the forearm attachments, preventing the rollator from accidentally being engaged. In its resting position, the brakes are engaged, and the rollator does not move.

This report discusses how the Push-N-Go provides a solution to the project task. We discuss our users and project requirements and our rationale for designing a concept that meets our users’ needs. Finally, we explain the limitations of our project and future developments we would like to implement in future iterations of our design.

Users and Requirements

Users

As the final product of this project is an assistive device, the users include but are not limited to people diagnosed with rheumatoid arthritis and Interstitial Lung Disease. This device can also benefit those with limited hand dexterity who cannot walk independently. To go in-depth into the users:

Primary Users

Patients with Rheumatoid Arthritis: Patients with this disorder experience joint pain, particularly affecting hand and foot joints. It leads to a loss of grip strength and mobility, making it difficult for individuals to use standard walkers or rollators that require hand dexterity and strength (Appendix C).

Patients with Interstitial Lung Disease: Patients with this disorder experience breathing difficulties and usually have rheumatoid arthritis. As patients find breathing difficult, the disease makes it challenging for them to walk for long periods without taking frequent breaks (Appendix C).

Rollator users with limited hand dexterity: Rollators can be used by people who are not diagnosed with rheumatoid arthritis or interstitial lung disease. This device would help individuals with limited hand dexterity, such as elders, control the rollator more effectively.

Secondary Users

Physical and Occupational Therapists: Angled forearms also enforce physical therapy recommendations of decreasing weight rested on the rollator (Appendix D).

Workers at assisted living/senior centers and caretakers: Patients who struggle to control rollators independently no longer need assistance in braking, and caretakers can focus their attention on other aspects of care.

Requirements

Eliminate need for use of hands: Develop a braking system that can be controlled by the foot or palm.

Reason: To accommodate users with limited hand dexterity and grip strength, ensuring they can safely stop and lock the device without using their fingers.

Allows users to walk independently: Limited to no assistance is required to use this rollator

Reason: To allow users not only to walk but also use the rollator to provide independence in their community, such as sitting down or carrying items

Safe to use: The device should cause no harm to the user

Reason: The user’s safety should not be compromised when using this device anywhere.

Design should function as a form of therapy: The use of this device should not only be comfortable to use but should also have clinical benefits.

Reason: The device should allow the user to walk independently without having to depend on it forever. It should be a form of physical therapy. The device should allow the user to remain upright and continue to be able to walk.

Design Concept and Rationale

The Push-N-Go is a modified version of an existing rollator that supports people with hand dexterity and strength issues to improve their quality of life by allowing them to remain active in the community. The rollator has a modified brake system that requires the user to push down on the forearm rest to release the brakes. It consists of forearm rests, palm rests, and a modified wire-braking system. The wire brakes are attached to each forearm rest, and the resting position of the wire is in tension, keeping the brakes activated. The user deactivates the brakes by putting weight on the forearm rests, allowing them to use and control the rollator without the use of their hands.

Forearm Rests

Specifications and Use

The forearm rests are made of memory foam with a gel topper that adapts to the user’s arm, wrist, and elbow. They are also covered in mesh to release heat. The dimensions are 9.8 x 4 x 2.7 inches, and they are attached to a wood panel that is 3 x 10.5 x .75 inches.

Rationale

The ergonomic forearm rests provide comfort for the user as users tend to shift their body weight onto their forearms for support and stability. The additional padding and longer length will allow the user to walk for a longer period without their arms hurting from digging into the material of the rests. The forearm attachments have a resting angle of 20º, with the elevated end of the rest closest to the user. A spring holds a brake wire in tension; this is attached to the forearm rest. The user applies weight to compress the spring and push the forearm rest to sit at 90º from their body.

When in use, the forearm rests will be at a height around the user’s waist, and the height of the forearm rests is adjustable through the existing rollator. This allows the rollator to function as a form of therapy, keeping the user’s posture upright and allowing them to only use their forearms as much as necessary (Appendix E).

The users’ limited hand mobility and grip strength make it very difficult for them to hold onto the existing assistive devices (Appendix D). Allowing the user to support their upper body with their forearms was the next best option since it does not require the use of hand joints. This observance led to the incorporation of forearm rests in the final design. The pads will allow the user to support their weight comfortably and for an extended time, keeping their hands out of the equation.

Figure 2: Prototype of forearm attachment

Palm Rests

Specifications and Use

The palm rest consists of a stress ball made of foam and a wooden block to elevate the rest. The stress ball has a diameter of 2.5 inches. The foam is non-toxic and child-safe. See Appendix B for the specific materials used.

Rationale

The palm rests sit in front of the forearm attachments and place the hands at a slight angle, supporting the user’s hands and joints. These also give the user something to push against while walking, preventing their forearms from slipping out of the rests. The user will also gain turn control by allowing them to push more on one hand while holding back on the other.

The users expressed interest in one mockup, which consisted of a forearm rest with a palm rest attachment during mockup testing. Mrs. Groth also supported the idea due to the control it would add for the user, leading to its inclusion in the final design. See Appendix E for further details.

Springs

Specifications and Use

The compression springs are coated in nickel and composed of tempered steel wire. They have a diameter of 1.125 inches and a length of 3 inches. The wire diameter is 0.105 inches, and each spring supports a maximum weight of 41.6 pounds and a maximum compression of 1.108 inches.

Rationale

The compression spring keeps the brake wire in tension so that the brakes are activated in the rollator’s resting state. The compression spring should not warp since it has a maximum compression limit and is not being stretched. Thus, the coils should maintain their shape. See Table 7 for the compression spring selected for construction.

Brake System

Specifications and Use

Each brake cable is zinc-coated and consists of 19 wires. The length of the cable is 6.56 ft, but the length is adjustable to the height of the user since the length required to keep the cable in tension, which varies depending on the user’s height.

Rationale

The modified brake system functions similarly to the existing brake system of the rollator by pulling a stopper that presses against the wheel to prevent the wheels from moving. The brake wire is attached to the forearm rests, and the wire has a resting state in tension since the spring attached to the forearm keeps the wire taut. When the user puts their weight on the forearm rests, the spring compresses, giving the wire some slack. When the wire slacks, the stopper releases from the wheel, allowing the user to roll.

By controlling the brakes through a weight-based system that stems from the forearms, the user’s hands are not required to control the rollator. This allows the user to continue walking and being involved in the community, improving their quality of life.

From the secondary and primary research, it became clear that any braking system involving the hands would be too difficult for our users. (Appendix C) Instead of using their hands to control items typically maneuvered by hands, they would use their wrist, the palm of their hand, or their forearms. Based on this, the design focused on the forearms and palms since that does not require using the hand joints. The rollator frame was chosen because it is already common in the user base. It has the existing components of a built-in chair, a brake system that can be modified, and adjustable height, making it familiar to the users.

With our design, the user will not have to use their hands to control the movement of the rollator since they will have forearm rests and palm supports, and they will be able to control the brakes independently of the function of their hands and fingers. This design will accommodate our users’ needs by providing a device to safely navigate the community without depending on hand strength or mobility.

Figure 3: A drawing depicting the entire rollator with the attached forearm rests and brake system. In this drawing, the forearms are pressed down on the springs, meaning the brakes would be released and the walker would be able to roll.

Figure 4: This drawing depicts a closer image of the forearm-spring mechanism. When the spring is in its resting position, it is pulling the wire and keeping it in tension, meaning the brakes would be activated. When the forearms are pushed down, like in the bottom image, the wire gains slack, releasing the brakes.

Limitations and Next Steps

Limitations

The Push-N-Go design utilizes the same braking wire as current rollator walkers and bike brakes. While these brakes are standard, they tend to stretch out and lose their tautness over time. Accommodations for this were incorporated into the design similarly to current brake wires, as the wire can be pulled through a barrel adjuster at the bottom end, and new wires can be purchased to replace them. Still, the lack of longevity of these brakes limits the lifespan of the solution.

Further Testing

The Push-N-Go was developed based on testing of the mockup involving only Mrs. Groth since the patient was unable to attend. The initial interview with Mrs. Groth and one of her patients involved a very capable patient who had functioning hand joints and had never used an assistive walking device. Feedback from more patients and people who have difficulty maneuvering their hands would be beneficial. A more extensive base of clients from different areas and terrains would also provide information on what needs to be modified to make the design more adaptable. Further feedback on the comfortability, functionality, and durability of the design would be helpful to improve the prototype.

Next Steps

Maintenance

The wire brakes are adjustable by tightening the wire, but this may not be intuitive or easy to adjust. With the design, it is easy to swap out the wire for a new one; see Appendix G. The rollator may also wear out over time as the brake stopper begins to wear down, which is not easily replaceable. More research would be needed to modify that, but the current solution would be to modify a new rollator. The spring should not morph since it is a compression spring and has a maximum compression limit. This limit should keep the spring intact, allowing the brake system to continue functioning.

Wire Placement

Currently, the brake wire has been strung directly from the armrest to the wheel, exposing it to snagging during use. In future iterations, re-wiring the brake wire to follow the rollator’s frame would prevent possible damage to the design, along with improving the aesthetics of the design.

Figure 5: A drawing depicting the brake wires string onto the rollator frame, rather than straight down from the armrest to the wheel, to prevent snagging during use.

Attached Brakes

To improve the design, attaching the brakes on all the wheels would allow the user to control both brakes with only one arm. This improvement would be helpful when they need to open a door or use one arm to perform a task while still walking. Achieving this would require adding a bar or some rigid mechanism to attach the forearm rests to one another behind the back of the built-in seat or below the seat. This mechanism would mean that applying weight to one of the forearms releases the brakes attached to both forearms.

Safety and Failure Analysis Consideration

One of the main safety concerns for this design is when the user would like to rest on the device without the device moving. Since the design is weight-activated, this scenario could lead to injury since it may roll when they are simply trying to rest. To counteract this, the design was built with the intention of there being a minimum weight requirement before the brakes release. The design currently supports less than four pounds without the brakes releasing, which may not be enough to allow the user to comfortably rest without moving.

To fix this, side armrests or supports could be added, allowing the user to rest on something that is not attached to the brakes. These rests could be placed in front (front being the side closest to the user’s body) of the existing forearm rests in the design, or they could be outside of the existing rests. The outside ones, however, may be too far apart to be comfortable for the user.

The minimum weight required to release the brakes could also be increased by using a spring with a greater spring constant, but the design is meant to function as a form of therapy. If the threshold is increased, it may encourage the user to place extra weight on the rollator, contradicting part of the rollator’s purpose.

To gather a more clear solution, further research and user testing are required. Consulting with Mrs. Groth would be helpful, but it is currently unclear what the best solution would be.

Forearm Rest Angle

Currently, the forearm rest is pitched at a twenty-degree angle. With compression, this angle decreases to closer to fifteen degrees. In the future, Insetting the spring further into the forearm rest and decreasing the length of the spring would allow for an angle closer to ninety degrees between the upper and lower arm while compressed. This angle is optimal for patients, according to Mrs. Groth (Appendix D).

Additional Attachments

As built, the seat attached to the rollator provides a helpful place for the user to place their bag or any other item, but they can no longer use that to hold their stuff when they need to rest. An improvement to the design would be some hooks, attachable desks, or cup holders. These modifiers would improve the user’s ability to move independently through their day by allowing them to carry more items they need in one trip.

Conclusion

The design meets Mrs. Groth’s desire for an assistive device that improves the quality of life for someone with difficulty maneuvering their hands and joints by allowing them to comfortably and independently walk. This device consists of:

Ergonomic forearm attachments
Palm rests
Modified brakes that are released by weight

The design does not require the use of hands and relies on the forearms and gravity, allowing users with hand mobility issues to walk independently. The rollator’s height and the brake wire’s tension are adjustable, making the design accessible for users of many heights. It is simple to use and fix since it modifies the existing brakes of a rollator, and the frame of the rollator is familiar to the users. The design is easy to maintain and will improve the user’s quality of life by providing an assistive walking device that does not depend on the hands for use.

References

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Appendices