Personalized Knee Implants

By Mark Augusti, CEO of Conformis, Inc.

Quick Test Question: What’s the best way to get a great fitting suit or dress?

1. Have a tailor measure your actual dimensions and sew a garment to fit just you, or…
2. Pick a pre-made, “off-the-rack” small, medium or large garment that comes closest to your shape and size?

Actually, it’s not much of a test. Everyone knows a custom-made garment fits better. That’s why people pay extra to get custom-made clothing, and why “off-the-rack” is a synonym for something less expensive, and decidedly second-best.

And that explains why “customized” and “personalized” are two of the most overused words in the market for total knee arthroplasty (TKA), or, in everyday language, knee replacement surgery. Every manufacturer of knee implants is trying to capture a little bit of the halo effect from claiming that their devices are, indeed, customized for the patient.

It isn’t hard to blame them. There are numerous benefits from a fully personalized or custom-designed-and-manufactured knee, as compared to an off-the-shelf knee. For starters, there are better clinical outcomes, measured in numerous physiological and functional studies. The following section will highlight a few of these proven benefits – as reported by leading peer-reviewed medical publications.

Clinical Benefits of Fully Personalized Knees

The most important clinical benefit is that custom knees move much more like a patient’s natural knee. One study shows that patient-specific TKAs were more likely to result in proper neutral leg alignment compared to patient who received off-the-shelf TKA implants. Proper alignment results in better functional strength, improved range of motion, and less pain.

Another study in the Journal of Arthroplasty compared patients with customized implants to those with off-the-shelf implants as they performed exercises, including deep knee bends and rising from a seated position. The customized knees achieved kinematics – the relative motion of the femur and the tibia – closer to a normal knee. “Customized implant technology…affords benefits including more normal motion compared with a traditional [posterior cruciate-retaining] TKA,” the study concluded.

And a study in Arthroplasty Today published in 2017 showed a wide range of benefits for patients with the custom, individually manufactured knee, compared to off-the-shelf knees: lower rates of adverse events, lower rates of blood transfusions, and shorter hospital stays. Patients were more likely to receive favorable discharge dispositions – such a leaving the hospital for home care as opposed to a more expensive rehab facility.

The Patient Perspective

But what do patients say? Studies show that patients agree with physicians that customized knee implants are better than settling for off-the-shelf alternatives. Consider a study published earlier this year in the Journal of Bone & Joint Surgery Reviews (JBJS Reviews) that surveyed patients who had an off-the-shelf knee implant on one side, and a knee that was custom manufactured for their unique anatomy on the other side.

The JBJS Reviews study is the first to directly compare patient-reported outcomes for off-the-shelf implants to fully personalized knee joints. Nearly two-thirds of the patients said they preferred the customized knee, compared to only 6.4 percent who preferred the off-the-shelf implant. The patients reported less pain, better perceived mobility and a more “normal” feeling in the customized knee.

“Participants in the present study overall favored the customer total knee arthroplasty over the standard prostheses in all surveyed categories: pain, motion, stability, ‘normal’ feel and overall preference,” wrote the authors, three leading orthopedists from the U.S. and Europe. “The combination of a more precise implant fit and component rotation of [a customized implant] compared with the off-the-shelf TKA may have been a contributing factor for lower pain levels and functional superiority.”

Perhaps the best endorsement for customized knees is that patients were more likely to completely forget that they have an implant. The “forgotten joint score” (FJS) is a critical way of measuring patient satisfaction. If patients do not remember that their joints have been replaced, then the prosthesis has done its job perfectly. Here again, customized knees demonstrate superiority.

“The ability to forget one’s artificial knee joint in everyday activities can be considered the ultimate goal in total knee arthroplasty to ensure maximum patient satisfaction,” wrote the authors in the comparison study. And patients reported 16 percent higher FJS scores for their customized knee (67.9) over their off-the-shelf knee (58.3).

Then there’s yet another benefit to the use of fully personalized, or customized knee implants. In some ways, it is counterintuitive: despite the possibility of a higher implant unit cost to the medical facility, utilization of fully customized knee implants actually helps to save money on the procedure, as compared to off-the-shelf implants. Researchers at the University of Washington in Seattle, where both types of implants are used regularly, found that customized knees were associated with a shorter hospital stay (mean LOS 1.35 days) versus the traditional off-the-shelf implants (mean LOS 1.99 days).

Average direct costs to the hospital associated with the customized knee (e.g., shorter patient stay and sterilization) were $9,341, compared to $10,347 for the traditional implant (a 10.8 percent increase for the traditional implant). Ongoing research suggests that fully customized implants further reduce total costs to the healthcare system because patients recover more quickly and are less likely to require follow-up surgeries.

So, is that knee advertised as “personalized” really personalized?

It is not surprising that makers of TKA prostheses want to be associated with a personalized solution. For example, a European-based medical device company calls its TKA implant system “MyKnee®.” But this system really consists of a set of patient-specific tools and positioning guides, which are helpful for the surgeons, but do not include the most critical element: an actual personalized implant.

Similarly, the product name for another major orthopedic company is built around the concept of personalization. But it may be a bit of an overstatement because while it uses fancy software, the actual implants are made in predetermined sizes. There is nothing personalized about it from the manufacturer’s perspective. Doctors still have to try to best match a patient’s actual anatomy with one of the pre-existing sizes, as opposed to inserting a truly personalized implant that matches their individual patient’s anatomy precisely.

If I am being kind, I would say that these companies are trying to blur the line between off-the-shelf and customized – however, if I am being less kind, I would say that are engaging in false advertising.

The difference between a system with personalized elements included to aid the procedure and a fully personalized implant is more than one of semantics. Fully personalized knees, such as the Conformis Identity™ knee system offered through our Platinum Services^SM program, have demonstrated in multiple studies the benefits that matter most to patients: less pain, a more natural feel, quicker recovery time. It is why Conformis has been an innovator in fully personalized knees and hips since it was founded in 2004. Surgeons who truly put patients first will want to use genuinely personalized implants – not the systems that just feature a superficial “personalized” tag on the lapel.

Editor’s Note: Mark Augusti is President and CEO of Conformis, Inc., of Billerica, Mass.