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Joint Replacement: The Time has Come for Mass Customization of Implants

        Douglas Unis
        Dr. Douglas Unis

Douglas Unis, M.D., is a board certified and fellowship trained orthopedic surgeon specializing in hip and knee replacement. He has extensive experience in the muscle- and tendon-sparing anterior hip replacement technique, and was among the first to perform the procedure in New York City in 2006. Dr. Unis actively participates in clinical research related to hip and knee reconstruction, including anatomic knee alignment, 3D printing of implants and robotics. As founder and Chief Medical Officer of Monogram Orthopaedics, he is leading a team that intends to disrupt the industry with a just-in-time, clinically superior solution that cost-efficiently normalizes patient outcomes.


Custom implants aren’t new. In your opinion, what do they get right…and wrong?

No, custom implants are not new at all. But in the past, their utility in all but the most unusual clinical scenarios had been limited by high cost, long design and manufacturing times and inadequate surgical delivery methods. I remember, while a resident at Northwestern in the ‘90s, one of my professors was very interested in custom hip stems. He used them for about six months, but ultimately found that they didn’t solve any real clinical problem, were not cost-effective and had a several-month lead time. The bone was prepared with a final custom broach that did a relatively poor job. It just didn’t achieve the precision necessary to realize the benefit of the custom implant, and the stems either sat too high or too low, or too often a crack in the femur would occur while trying to force down the last broach.

But with advances in cloud based computing, AI, additive manufacturing and robotics, mass customization of orthopaedic implants is an idea whose time has finally arrived. There is now no reason that the orthopaedic industry should not provide the same on-demand customization that my eight-year-old currently enjoys in her entertainment options! First and foremost, custom implants must solve real clinical problems and advance the state of the art, lest they be relegated to the dust heap of orthopaedic gimmickry. Too often, we see cool new tech that amounts to solutions in search of problems. Achieving clinical benefit is dependent upon first identifying clinical problems and then designing a system to solve them, not the other way around. Second, they should decrease cost to the system whether related to carrying large inventories, implant manufacturing costs, surgical time and complications, etc. And third, patient-matched implants must be manufactured in a rapid and reliable fashion to be delivered to the O.R. without disruption to established workflow.

Some areas of medicine have been more successful at patient-specific implants, such as CMF and oncology. Patient-specific implants quite simply do a better job of restoring patient anatomy. The reason that they work is low mix and low volume with less need for robotic delivery. The industry hasn’t yet figured out how to scale high mix/high volume patient-specific implants or their delivery tools. It is well recognized by the major implant makers, however, that patient-specific implants are the future.

What is Monogram Orthopaedics’ solution to improve joint replacement?

We aim to fine-tune joint replacement surgery at every point at which human error and limitations in off-the-shelf implants currently exist. From surgical planning to bone preparation to implant positioning, our platform provides an end-to-end solution. The 3D pre-op planning station incorporates surgeon-driven modification of certain features of the implants. To ensure that the plan is executed accurately, Monogram links custom implants with a high precision robotic mill that exerts a fraction of the force of manual broaching. Our implants achieve more metal-to-bone conformity than is possible with standard implants and manual instrumentation, thereby making their initial fixation nearly indistinguishable from cemented implants in mechanical testing. This stability allows for bone conservation and produces ideal conditions for osteointegration and long-term fixation. Our hip stem restores the center of rotation of the hip, or whatever target the surgeon sets, with sub-millimeter accuracy. Monogram’s motto is, “No complications, quick surgery, lower cost, happy patients.”

What’s different between your approach and others that are already out there? For example, what is your robot doing differently? What sets your AI apart?

Like many other technologies, robots have gotten exponentially better even as costs have plummeted. Our robot is lightweight and agile with a long reach and 7° of freedom, allowing it to perform any number of tasks while remaining out of the surgical team’s way and not disrupting normal O.R. workflow. We have eliminated line of site issues like pole-mounted cameras by equipping the robot itself with advanced machine vision. We have developed dynamic obstacle avoidance capability and optimized the robotic cut paths in real time, facilitating safe automated robotic motion and dramatically improving efficiency. In short, the Monogram robot will not only make joint surgery more accurate, but also faster and safer at a reasonable price point and with minimal disruption to a surgeon’s existing workflow.

There is a lot of hype surrounding AI, but it can be a powerful tool. Our algorithms compress the timeline and decrease man hours required to analyze patient imaging and design, and manufacture patient-specific implants. Monogram’s secret sauce is the algorithms that auto-generate our implant designs, as well as the cut paths. This is a non-trivial problem, and our solutions have allowed us to fundamentally rethink implant design to address the clinical limitations and failings of generic implant design.

How will Monogram’s technology address hospital pain points?

As I mentioned, the price of advanced collaborative robotic technology has come down precipitously, so we expect that the capital expense will be significantly lower than existing technologies. We will significantly diminish the number of surgical trays to be processed and transported, as well as the size of implant inventory. It is estimated that 40% of an implant sales rep’s time is spent managing inventory and instrument trays. And it is well recognized that the burden of carrying massive inventories is quite significant for the major implant manufacturers. By reducing these costs, we can bring down implant prices even as we deliver patient matched products. At a higher level, the orthopaedic market is an oligopoly, largely driven by necessarily large inventories and capital cost of servicing customers. Smaller companies with smaller balance sheets just don’t have the ability to offer the range of products, and they can get away with overcharging for medical equipment. Monogram plans to disrupt this paradigm by facilitating a highly differentiated just-in-time inventory solution that normalizes the hardware costs.

Bundled payments have introduced new financial pain points for hospitals for surgical complications, re-admissions and returns to the O.R. Our platform aims to decrease many of the most common complications: peri-prosthetic fracture, early loosening, dislocation. We can also increase patient satisfaction by eliminating leg length discrepancy, decreasing bursitis and tendinitis following joint surgery, accurately restoring biomechanics and optimizing patient function. Satisfied patients, of course, drive business to hospitals.

Our technology may also expand surgical indications to younger knee replacement patients by introducing cementless implants with “cement-like” stability. Just as better bearing surfaces and cementless implants brought down the average age of total hip patients, more robust and reliable cementless fixation may have a similar effect on total knee patients.

Who is on your team, and how did you find each other? What keeps you inspired on the road to commercialization?

Our platform has freed us to completely reimagine orthopaedic implants, asking only, “What is the ideal implant for each individual patient?” And as we move forward looking at knees, shoulders and other joints, we are aware of being on the cusp of a completely new generation of implants and perhaps a paradigm shift in the orthopaedic industry. We are a tech-heavy, engineering-focused company. We have made deliberate efforts not to hire conventional “in-the-box”-thinking engineers. Monogram is fundamentally rethinking the limitations of generations of implant design.

So like I said, our team is very tech-heavy. Our CEO and VP of Robotics have a nice internal MIT vs. Caltech rivalry going. Our head of software is an incredibly gifted programmer who took a sabbatical from medical school to help drive the development of our algorithms. Programmers with deep clinical knowledge are really hard to find! I think what sets our company apart is the incredible energy level and passion of our team. The words “this is how it’s been done” don’t mean much to our group. We are fundamentally rethinking an industry that in our view has grown a bit complacent with the status quo.

What questions do you wish we’d asked? (What would you have said in response?)

“How can people get involved and follow the story? When will you have more to share with world?”

We have been very “stealth” about our development efforts, but stay tuned for 3Q19. We have some very big announcements coming.