For people who have lost a limb, a well-fitting prosthesis is key to their mobility and quality of life. Researchers are testing whether 3D printing can make creating crucial, made-to-fit parts of prosthetic limbs faster and more comfortable for patients.
On Aug. 7, 2018, millwright Shawn Fitzpatrick was riding his motorcycle from his Ajax home to the plant in Scarborough where he worked. At 4:40 a.m., the 54-year-old was struck at an intersection by a left-turning transport truck.
“I could feel it hitting my ribs, and my face was stuck on the front headlight,” Shawn recalls. “I tried to get my motorcycle out of there, but with the impact, it must have stalled. Then I woke up with somebody holding my head.”
Shawn was taken to the Tory Regional Trauma Centre at Sunnybrook with life-threatening injuries.
He has almost no memory of the next few days. Later, Shawn learned that physicians had removed his damaged spleen, repaired his broken left hip, knee and lower leg bones and grafted skin onto places where he no longer had any. But the biggest concern was Shawn’s severely injured left foot.
“They kept on trying to save it, but finally they said, ‘Your foot’s started to turn black and your pulse there is really bad,’” he says.
Faced with the prospect of amputation, Shawn thought about all the things he still wanted to do with his life: playing with his grandchildren, spending time every year with his mother in their native Newfoundland, being in the outdoors and staying active. He chose to see the positive in the situation.
“I was happy getting my leg cut off because the prostheses today are amazing,” Shawn says. “I knew it was going to put me in a better spot.”
The amputation, about 20 centimetres below the knee, took place just over a month after the crash. Afterwards, Shawn began rehabilitation therapy at Sunnybrook’s St. John’s Rehab, where he stayed until going home in November.
Joining a 3D printer study
Shawn currently returns to St. John’s Rehab twice a week to attend physiotherapy. He’s also part of a study there looking at the potential benefits of using 3D printing technology versus traditional methods to make a socket – the part of a prosthesis that connects to the residual limb.
The research is being led by Dr. Amanda Mayo, a physiatrist (physician focusing on physical medicine and rehab) at St. John’s Rehab who specializes in working with patients with limb loss. She is collaborating with the team of prosthetists at the Sunnybrook Centre for Independent Living (SCIL). Another study partner is Nia Technologies, a non-profit organization affiliated with the University of Toronto.
With a grant from MaRS, a Toronto innovation hub, the researchers are exploring whether a 3D printing system is faster, more cost-effective and more comfortable for patients than the traditional method of making sockets using plaster casting.
They have produced “diagnostic” sockets using the innovative technique for five patients, to determine the quality of the fit. They hope to enroll another 15 patients in the study before the end of 2019. All patients, like Shawn, have below-the-knee amputations and are trying out these sockets during their therapy sessions at St. John’s Rehab.
Like the ‘foundation of a house’
The socket is the only part of a prosthesis that is custom-made for the patient and its fit is critical, says Shane Glasford, team lead in prosthetics at SCIL.
“I equate it to the foundation of a house. The other [prosthesis] components are built on top of that good-fitting socket,” says Glasford. “The socket has to be comfortable enough to walk on, to give enough support for the user and to hold their body weight, allowing them to do all the things they want to do.”
In the first year or two after limb loss, the shape of a patient’s residual limb changes rapidly, and the patient may go through several sockets. The 3D method may allow the prosthetist greater adaptability and versatility in the fabrication process to create better-fitting sockets.
While research into computer-aided socket design and 3D production is taking place elsewhere, few studies are looking at the potential cost savings, turn-around time and quality improvement aspects of 3D printing, Dr. Mayo says.
“We’re doing qualitative interviews to see how patients like the digital scanning process and 3D printed sockets,” she adds. “In keeping with our St. John’s Rehab research mandate, this is research focused on improving patient-centred prosthetic care.”
Dr. Mayo notes that conventional socket-making has some challenges. In this process, prosthetists first take a cast of the residual limb. The cast is then filled with plaster to create a positive mold. Once dry, the mold is contoured by hand. Finally, thermodynamic plastic is draped over the mold to create the prosthetic socket.
It takes about eight hours of manual labour to make a socket in this way. However, because of the time required for the plaster to dry and the need to chip out the plaster inside the socket, the turnaround for a patient staying in rehab is about seven days.
Dr. Mayo says that the initial step of making the mold also requires prosthetists to physically touch patients, which can be uncomfortable if they have skin wounds or skin grafts.
With digital scans and 3D printing, there is no need to touch the patient. The process involves a 10-to-15-minute scan using a tablet for “shape capture,” after which a trained prosthetist fine tunes the shape on a computer. The image is then transmitted to a 3D printer to produce the socket out of plastic, though the prosthetist then needs to “smooth out” its edges, Glasford says.
Studying the benefits
The team is still assessing the time and cost savings with the new method. According to Glasford, it currently takes six hours to 3D print a diagnostic socket.
“Cost-accessible 3D printers, such as the one we are using, [have shown they are] suitable for making temporary sockets for diagnostic purposes to verify fit,” Glasford says. He adds that the digital process will also become swifter as prosthetists at Sunnybrook get more comfortable with the new technology.