Customized implants for knee replacements - Mayo Clinic

Sept. 18,

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Mayo Clinic offers customized prostheses for select patients who need total knee replacement. Each implant has a unique design, based on a CT scan of the patient's knee. Algorithms convert the scan to a 3D model by mapping the contours of the bone and correcting areas damaged by the disease process.

"A customized implant can function more like a patient's own knee because it works in unison with the patient's ligaments and tendons. With an off-the-shelf implant, we have to make compromises to get the soft tissues to work with an implant that isn't the same size or, more importantly, the same shape as the patient's natural bone," says Henry D. Clarke, M.D., an orthopedic surgeon at Mayo Clinic in Phoenix, Arizona, who helped develop the customized system.

The customized implants are designed for people who wish to remain active. "We use them in patients who want to do vigorous physical activity, such as tennis or downhill skiing. As with other knee prostheses, we don't advise high-impact activities such as basketball or soccer afterward," Dr. Clarke says.

Customized knee prostheses are costlier than some conventional knee replacements. In addition, design and production of a custom component can take six weeks; conventional implants are available immediately. Dr. Clarke notes that both of these factors currently restrict the wide use of customized knee prostheses.

Mayo Clinic offers the customized option, in addition to traditional knee replacement, as part of its commitment to improving patient satisfaction. Although conventional knee prostheses provide good outcomes in the aggregate, some patients experience persistent pain or restricted movement.

"At Mayo, our goal is to expand the good results we get in general with knee replacement surgery and reduce the segment of the patient population who feel that things just aren't quite right following knee replacement," Dr. Clarke says. "We want to achieve results with knee replacement akin to those we see with hip replacements, where patients are able to forget that they have a prosthetic joint."

Unlike a conventional knee prosthesis, a customized knee prosthesis is often asymmetrical, with different medial and lateral dimensions — mimicking variability in the patient's anatomy. Published research has demonstrated that customized total knee arthroplasty improves kinetic function. A study published in the April issue of the Journal of Arthroplasty used mobile fluoroscopy to analyze tibiofemoral kinematics in patients with customized and conventional knee implants. "This study indicated that when patients are climbing steps or squatting, the customized prosthesis functions more like a normal knee," Dr. Clarke says.

"The outcomes we see at Mayo are favorable," he adds. "Patients with a customized knee replacement do at least as well as I would expect with a conventional knee replacement, and many of them are among my happiest patients after surgery."

Disclaimer

Dr. Clarke reports receiving royalties and consulting payments from Conformis to help design and commercialize these total knee replacement prostheses.

For more information

The UAB Medicine Orthotics and Prosthetics Clinic specializes in support devices for weakened limbs and joints, as well as custom devices (prostheses) to replace limbs. Unlike with some clinics, these prostheses are designed, made, and adjusted in house at UAB Medicine, which makes it easier for patients to get a proper fit in less time.

If you are looking for more details, kindly visit Custom Prosthesis Parts.

Prosthetics is the branch of medicine that focuses on designing and making artificial body parts, called prostheses. UAB Medicine prosthetists are trained in the fitting and construction of both upper- and lower-limb prostheses. A standard prosthesis is made of individual parts that are combined to create an artificial limb. These parts connect to a socket that fits over the patient’s remaining limb.

Orthotics is a medical specialty that uses appliances to support joints and limbs, to help improve mobility and strength. UAB Medicine orthotists customize these appliances to make sure patients get the most comfortable and functional fit. Custom pedorthic (foot) devices, for example, support and reposition the foot structure to work in harmony with the leg, knee, and hip. This helps make each step pain-free, which is needed to prevent injury and maintain mobility.

In-House Advantage

UAB Medicine’s Orthotics and Prosthetics team delivers personalized care, using modern methods and materials that offer patients many choices. Because prostheses are made in house, patients benefit from better management of the care process and a better fit.

“We can keep our eyes on the fabrication from beginning to end,” says Brian Mueller, a certified prosthetist and manager of the clinic. “When getting the new prosthesis, patients may arrive here with swelling or shrinkage from surgery. That starts a period of adjustment where we are getting the fit and function perfected, the same way you might work to get a new medication at the correct dosage. If patients gain or lose weight, it may require yet another adjustment. I spend a lot of my time on adjustments and checking up with patients on how well the prosthesis is working. It’s convenient for our patients because they come here for adjustments rather than having to send anything to a vendor out-of-state.”

Tracy Brewer, administrative director of the Orthotics and Prosthetics Clinic, agrees that this convenience makes the entire process a better experience for patients.

“Having all the services right here, beginning with fabrication, is a huge benefit,” Brewer says. “It’s an ongoing process for our patients, including tweaking the device, replacing liners, and maintenance. Along with convenience, there’s the benefit of not incurring any additional costs. There’s no charge for office visits. Adjustments are free. In fact, our department even pays for parking.”

Creating a prosthesis involves plenty of personalized care at the clinic. The first treatment controls swelling and shapes the patient’s remaining limb. The process takes six to eight weeks, after which Mueller makes a cast or mold of the remaining limb and takes measurements. He creates the prosthesis within two weeks, then the patient comes in for a fitting.

“The first phase of my job is to get the best comfort and function,” Mueller says. “The second phase is selecting all the components that are available from manufacturers to fabricate the ideal prosthetic for the patient, based on age, activity level, and other criteria, so they can reach their maximum functional outcome.”

The team then tests range of motion, checks to see if the device causes discomfort, and completes the fit in about one week. Follow-up adjustments are done over the next few weeks and months, with additional adjustments and maintenance done every six months for the patient’s lifetime.

Complete Care for Over 50 Years

Located in UAB Spain Rehabilitation Center, the Orthotics and Prosthetics Clinic has been treating patients since . Its practitioners and technicians have over 100 years of combined experience. The clinic provides complete care, from pre-surgery through rehabilitation. A team of physicians consults with the prosthetists prior to amputation surgery so that they can better explain to their patients what to expect.

Patients usually are referred to Conley Carr, MD, who directs the Spain Rehabilitation Center Amputee Clinic. Dr. Carr counsels patients on pre-prosthetic rehabilitation prior to an amputation and follows their progress to prescribe prosthetic limbs and improve mobility and function.

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