Yes, Robotics Is the Future of Joint Replacement

While joint replacement procedures are one of the most common elective surgeries in the United States, with total knee replacements expected to increase by 189% by 2030 and total hip replacement (TKR) by 171%, there is still room for improvement in how these surgeries are performed.

Studies show that up to 20% of patients are left unsatisfied after total knee replacement, begging the question, would robotic-assisted joint replacement offer patients better outcomes?

Many studies have weighed in on this question and while there are benefits to robotic-assisted total joint replacement, the jury is still out on whether the benefits are enough to justify the costs which is upwards of $1 million dollars. This is a big investment considering the pressure in today’s healthcare systems to reduce costs.

Researchers involved in one such study, “Comparison of conventional versus robotic-assisted total hip arthroplasty using the Mako system: An Italian retrospective study,” published March 2018 in the Journal of Health & Social Sciences, found the Stryker’s Mako Robotic Arm Assisted Technology did significantly decrease a patient’s hospital stay but did not find any significant differences in patient-reported outcome measures. Therefore, they recommended further long-term studies to justify additional costs.

Douglas E. Padgett, M.D., chief, Adult Reconstruction and Joint Replacement at the Hospital for Special Surgery in New York City, however, has found in his own research that despite cost concerns robotic-assisted total joint replacement does improve outcomes and that robotic technology is here to stay.

According to Padgett, in joint replacement there are still three main issues: bearing wear and failure, instability (largely in hip replacement) and patient satisfaction (largely in knee replacement).

Better Control Over Surgical Variables

Using a unicompartmental knee replacement (UKR) case study, he discussed how a robotic tool could improve how much control surgeons have over these issues.

“UKR is somewhat controversial. It has been said, ‘Only a doctor with half a brain would put in half a knee replacement,’” he said. “But if you look at UKR there are a lot of advantages.”

Some of the advantages include preserving the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL), low complication rates, a rapid return to work and possible cost savings. Researchers have also documented a high return to sport with more than 95% of patients returning to preoperative level of sports.

There are however durability concerns and the need for revision.. Variables that influence the outcome of UKR, according to Padgett, include: patient selection, implant positioning, fixation, lower limb alignment, proper sizing, implant design, whether inlay, onlay or mobile bearing and soft tissue balance

UKR failure, Padgett said, is often associated with technical error, with surgical technique having a dominant effect on outcome especially when it comes to avoiding over and under correction of lower limb alignment, attempting to reduce the varus angulation of tibial slope, and avoiding a posterior slope of implant greater than 7 degrees.

He pointed to an analysis of wear patterns on retrieved implants from non-robotic-assisted UKRs in “Unicondylar Knee Retrieval Analysis” published in the Journal of Arthroplasty on June 14, 2010. The wide variation of alignment found in the wear patterns on these implants suggests there is room for improvement.

What Can the Robot Do for You?

Padgett said that robotic-assisted surgery can enhance control of surgical variables which will then improve outcomes.

It offers the surgeon precision preoperative planning, allowing him or her to think and work in a 3-D space, as well as precision execution of the plan. The robotic tool controls variables such as implant positioning, soft-tissue balance, lower limb alignment and proper sizing. What the robotic tool cannot do is fixation, implant design and patient selection.

“The robot does not do pre-operative selection. Inlay UKR in a patient with tibial osteonecrosis is going to fail with or without the robot,” he said. “And it can’t cement the implant for you or choose the device for you.”

It can however improve positioning reliability as proven by two studies out of Great Britain published in The Journal of Bone & Joint Surgery in 2006, “Limb alignment in computer-assisted minimally-invasive unicompartmental knee replacement” and “Hands-on robotic unicompartmental knee replacement,” which both showed clear improvement in using the robot.

G. Keene and his colleagues in the first study compared 20 navigated UKRs to 20 conventional UKRs and found that surgeons using navigated UKRs had a better rate of staying within ±2 degrees of the pre-operative plan (87% vs. 60%).

J. Cobbs and colleagues conducted a prospective, randomized trial of the ACROBOT system where 13 robot-assisted surgeries were compared to 14 conventional surgeries.

In the robot group, there was 100% coronal plane alignment within 2 degrees of the computer tomography (CT)-based plan. In the conventional group, there was 40% within 2 degrees of the CT-based plan.

Cobbs and colleagues also reported a trend toward improved WOMAC (The Western Ontario and McMaster Universities Osteoarthritis Index) with robotics at 6 weeks and 3 months.

The data from these two studies was used to design the initial workflow for robotic UKR using the Mako technology:

• Implant pre-planning CT based for both sizing, and implant positioning
• Registration (robot and patient anatomy)
• Gap Planning (virtual trialing) – soft tissue balance, long leg alignment
• Robotic execution of plan
• Removal of osteophytes and meniscus including implant position verification

This was validated in a cadaver study, “Unicompartmental knee arthroplasty: Is robotic technology more accurate than conventional technique?” published in August 2013 in The Knee, which clearly demonstrated improved implant positioning with robotic technology.

Mustafa Citak, M.D., and colleagues reported that the femoral component RMS (Root Mean Square) placement errors were 3x more accurate (p < 0.05) and 3.1x less variable in the robotics group (p < 0.05) and the tibial component RMS placement errors were 3.4x more accurate (p < 0.05) and 2.6 less variable (p < 0.05) in the robotics group.

Padgett also pointed to the high two-year survivorship rate found in a multicenter study on robotically assisted UKA (unicompartmental knee arthroscopy) led by Andrew D. Pearle, M.D. of the Hospital for Special Surgery in New York.

“Were we able to control variables?” Padgett asked. “The answer is Yes. Interestingly enough there was an over tendency to overcorrect in lateral compartment medial UKR.”

According to the results, the revision rate at 2 years was a 1/3 reduction compared to the Swedish Registry which was 4.5% and a 75% reduction compared to the Australian Registry which was 4.8%.

Padgett said satisfaction in the UKA cohort was unbelievable high with 92% robotically assisted UKA patients “very satisfied” or “satisfied” (773/842).

Padgett also confirmed the robot’s ability to position implants more precisely in an analysis of failed MAKOplasty Unicondylar Knee Replacements that he and Evan O’Dea, M.D. of Weill Cornell Medical College conducted.

On the future of robotic technology, Padgett said, “Robotic TKR: It’s here and now. The future is upon us. Robotic UKR allows for customized control of implant positioning, reliable lower limb realignment, and control of soft tissue balance.”

He added, “Being able to use enabling technologies might allow the development of novel implant design shapes which otherwise might not be possible with traditional cutting tools.”

“And maybe make possible more kinematically ‘normal’ devices. Think bicruciate knees!”

In regard to fixation, he said that precision preparation may allow better cementless knee designs as well.

He warned though that “A fool with a tool is still a fool” so don’t use the robot in the wrong indication.

Meet Dr. Padgett at the Upcoming ICJR South Hip & Knee Course

Padgett’s research was originally presented at the International Congress for Joint Reconstruction’s 2016 4th Annual South Hip and Knee Course, during “Controversies in TKA – Why even consider robotics? Isn’t TJR pretty forgiving! Padgett’s presentation on robotic technology is also on the agenda for the 6th Annual ICJR South Hip & Knee Course which will be held June 21-23 in Key Largo, Florida, at the Ocean Reef Club.

The conference is designed for orthopedic surgeons and allied health professionals looking to learn the latest in orthopedic technology, surgical technique and optimum patient care. The course will include current controversies in TKA and total hip arthroplasty, enhances recovery and outpatient arthroplasty, live surgery and perioperative patient management.

To register, click here.