Aqua Therapy for Total Knee Replacement (TKR)
Summary
I designed an aqua-therapy tub for Total Knee Replacement patients after using design methodologies to determine the patient need. This tub would allow for better rehabilitation after surgery, solving many patient needs and allowing for a better recovery. After the thorough design research phase, I created the CAD model that could be sent to a manufacturer, a 1 to 1 scale physical mockup, and a VR experience to better understand how the design would work.
You can also experience this page as a museum in a VR application I built using Unity, Blender 2.8, Keyshot, Solidworks, and Audacity. If you have a VR PC, you can play my experience.
Tested with Valve Index and Oculus Rift, should also work with any Steam VR compatible headset, including Vive and Windows MR.
Overview
Being able to walk is a huge advantage in society. But many people have problems with their joints over the years, leading to increased pain and/or decreased joint functionality. Total Knee Replacement (TKR) is a highly effective surgical procedure to solve this problem.
Modern Replacements
The procedure has come to be one of the most effective surgical procedures in medicine, and a multibillion dollar industry. Over 700,000 TKR surgeries were performed in 2010 (Source: CDC/NCHS National Hospital Discharge Survey, 2010),
Who Needs TKR
The aging population is only going to make TKR surgery more prevalent in the future.
Excess weight on the knee is one of the leading causes for knee failure, necessitating a TKR surgery. This too, is a problem that is only getting worse.
Mind Map
I created a Mind Map to identify the parts of the TKR, and what could possibly work better.
Laura Rosenberg - Physical Therapist Interview
Make sure that their quad muscles are in good shape, because that's what really holds the knee together
All the muscles surrounding the knee, but also work on the hips, just for stabilization of the entire leg.
Keep that joint moving. Sometimes they come in and tissue has formed around the knee replacement. And they will have to manually go in there, go back in and rip the tissue off, because they haven't been moving it.
I interviewed Laura Rosenberg, a Physical Therapist on the recovery aspect. Above are some notes from the interview, emphasizing the need to keep the joint moving and build muscle.
TKR Patients, Sample From 8 Interviews
The pool helps because there is not weight when doing the exercises. - Janet
Was no way you were going to get a squat out of me on land, but in water that was possible. - Dee Anne
As soon as you are completely healed, get in the water. - Jean
Getting in cold water in the pool, I would struggle with. - Jean
For my left knee, I would come home from PT and go up to the pool and do the exercises I did at PT. But not with my right knee, it was fall. - Cindy
There wasn't one available where I went for PT. - Sue
I joined TKR Recovery support groups on Facebook, and asked if people would let me interview them about their recovery process. I was able to conduct eight interviews, via either Facebook Messenger or the phone. Many of the participants mentioned aqua-therapy, and being in a pool as key to their recovery, but there were many burdens to receiving that care.
I read research papers to make sure Aqua-Therapy was medically valid. Silva, et al., wrote a paper showing "the water-based exercise group experienced a significantly greater decrease in pain than the land-based exercise group." https://doi.org/10.2522/ptj.20060040
Hinman, et al., wrote a paper showing "aquatic physical therapy resulted in significantly less pain and improved physical function, strength, and quality of life." https://doi.org/10.2522/ptj.20060006
Aqua-Therapy - Exercises
I found that there were comparable aqua exercises for all the standard land exercises for TKR rehab, but the aquatic ones seemed more fun and less like a chore.
I created a persona to design around, trying to create one that met most common criteria.
Current Tubs - Standard - $700
I looked at the current bathtub marketplace. Most bathtubs are under $1000, but too small to stand in. They also had posed problems for people who had a TKR surgery, as it required a climbing motion that wasn’t always possible.
Current Walk In Tubs - $3,000
Walk in tubs are designed for people who have trouble laying down and pulling themselves back up. But they were still not large enough for aqua-therapy to be effective. They also were ugly, and still difficult to enter for someone just starting their TKR recovery process.
Current Therapy Pool - $75,000
Current aqua-therapy pools are large and great for exercise, but incredibly expensive and too large for a normal home.
Market Space
I looked at the market for bathtubs, and my 150gal, $4000 tub would be larger than most, and on the higher side of price, but would still fit in nicely in the existing marketplace.
Ideal Pool
I made sure I took the size of the 99 percentile largest men and women, and the smallest 1 percentile men and women. I wanted an inclusive tub, since multiple people likely live in one house, and multiple molds would make manufacturing dramatically more expensive.
Physical Size Testing
I was able to use some of my fellow class-mates to test the size of a cardboard mockup, to make sure the textbook matched real-life. I ended up changing some of the rail handle heights to be more accommodating of shorter people.
Door Sketches
No one wants to have an ugly thing at home, and especially not something that points them out as "one of those old people." I iterated on door designs to try to add some flair and perhaps made the tub more of a statement.
Railing Sketches
I also sketched various hand-rail patterns, to try to make the tub visually appealing as well as functional.
Combination Sketches
I combined the two and tried to iterate further with some slightly more developed sketch concepts.
I wanted to leave no stone unturned, and iterated on doors.
I made CAD models using SolidWorks to visualize my ideas and nail down some details. The first tub is boxy, but useful, with a partition to pre-fill part of the tub before you enter.
The second concept had more style to it. The profile of the handle grip is in grey on the right. This profile has a lower chance of splashes reaching beyond the tub.
The third design has a tear-drop shape, to allow enough space to stretch out a leg, but saving water compared to a rectangle.
The fourth concept was a more stereotypically masculine, angular and grey metal design, including the space saving shape.
I then made renders of my favorites to see them in their environment.
Validation Thesis
I asked the same TKR Recovery Facebook group that I was able to get interviews from if they would potentially buy this, and any feedback.
Validation Results
7 Responses
Yes, but...
Only if health insurance covered it
Only if there were some design changes
Most people said yes, but... The price was out of reach of many people, who would only buy it if health insurance covered it. Others wanted some design tweaks, like a spot for soap and shampoo. Others were concerned about how long it would take to fill. I took all the criticism in consideration for my final design.
Final Aqua-Therapy Tub
I took those criticisms to heart and tried to design an even better final product. I made sure there was a spot for soaps and shampoo.
To save time, I designed a separate compartment that can fill up before you step in the tub. Then once in the tub, you pull a handle to equalize the water, then keep filling up the tub the rest of the way. The water divider can be folded away to allow you to use the entire tub.
If you have an iPhone, you can see the aqua-therapy tub in AR in your own space.
You can also experience this page as a museum in a VR application I built using Unity, Blender 2.8, Keyshot, Solidworks, and Audacity. If you have a VR PC, you can play my experience.
Tested with Valve Index and Oculus Rift, should also work with any Steam VR compatible headset, including Vive and Windows MR.
