EXACT CUTS After surgeons complete a fairly short learning curve, robotics ultimately make the joint replacement surgery much more reproducible.

Nothing makes a surgeon sweat like a unicompartmental knee replacement. It's a technically demanding surgery to pull off successfully, especially with conventional instrumentation. It's no wonder there are so few surgeons who perform enough procedures to achieve excellent outcomes. But now, thanks to the reproducibility afforded by robotics, even your lower-volume surgeons can operate like seasoned pros. Plus, if my center's experience is any indication, the revenue generated from the cases you'll add will more than make up for the amount you invest in the technology, because patients will want to have surgery in a facility with robotics.

Marking the boundaries
Most estimates say 15 to 20% of knee replacement patients may be candidates for partial replacement of the joint. That means if 1 out of every 5 of your joint replacement patients isn't at least considered for a unicompartmental procedure, your surgeons are replacing too many total knees. Robotic-assisted surgery can help flip those percentages around by making uni knees much easier and more reproducible to perform.

All patients who are candidates for partial knee replacements can have the procedure done robotically. There are 2 main options to choose from. One requires a pre-op CT scan of the knee, which is used to generate a 3D model of the joint's anatomy. During the intraop planning phase, surgeons can assess the kinematic balancing of the knee's ligaments and optimize implant positioning before any bone preparation is performed. The robotic platform's camera captures the pose and applies it to the 3D model, which surgeons use to plan the precise placement of implants in the joint, where they'll achieve the desired alignment and stability. If the implant is ultimately placed in the exact position indicated on the model, the knee's ligaments will be balanced and the implants will be sized correctly. That means the implants' contact area will be placed along the joint's centerline, so premature wear and loosening can be avoided.

On the day of the surgery, the surgeon places optical arrays in the femur and tibia near the knee joint. The robotic system tracks the arrays in real 3D space and in real time. Once the arrays are placed and the bone is registered with the system, the surgeon moves the platform's robotic burr into the joint. The burr is constrained by haptic boundaries, so it can shave away bone only in the locations indicated on the model created during the pre-op and intraop planning phases, meaning the implant will fit precisely where the surgeon intends.

Another robotic-assisted system employs a handheld smart instrument that uses haptic boundaries to guide the surgeon to areas of the bone in the joint that need to be shaved. Much like surgical navigation systems, the instrument is completely dependent on the surgeon inputting data points — not on actual patient anatomic data taken from a CT scan — so it might not be as accurate as a true robotics system. However, it's also approximately half the price and is a vast improvement over joint replacement performed with standard instrumentation.

ADDED VALUE
Patients Prefer Partial Knees

FOLLOW-UP EXAM Patients who undergo partial knee replacements report a high degree of satisfaction and are in less pain than total joint patients.

Surgeons often open up knees to replace the entire joint only to discover that the lateral compartment looks pristine or that the patient is suffering only from medial arthritis. Those patients typically have good range of motion, but might suffer from a diseased medial compartment with bowlegged varus deformity. They may or may not have arthritic changes in the patella femoral joint, and they don't have significant anterior knee pain. They point to the medial side of knee and say nearly all their pain occurs there. Or if they suffer from lateral arthritis, which is less common, they indicate that most of their pain is in the lateral part of the knee. If they're experiencing isolated patella femoral arthritis, they get a jolt of anterior knee pain when walking up and down steps or standing from a sitting position. It's these patients, in whom pain can be isolated to a single knee compartment, who are ideal candidates for uni knee procedures.

I've performed the procedure on patients in their 70s and 80s whose knees I would have replaced entirely just 2 or 3 years ago, before using robotics. They experienced good results after undergoing total knee replacements and were happy to be rid of their arthritis pain, but they felt like their joints never returned to normal function. Now, with the use of robotics, those same patients are be back home ambulating 6 hours after surgery in a lot less pain and rehabbing at twice the pace they would have after having their entire joints replaced. I've spoken with my patients who've had a total joint replacement performed on one knee and a robotic partial replacement performed on the other. Uniformly they prefer the outcome of the uni knee.

— Joseph Nessler, MD

EXTRA GUIDANCE Robotics can help surgeons overcome some of the inherent challenges of using conventional instrumentation when placing implants.

Clinical benefits
Most surgeons who perform partial knee replacements with conventional instrumentation find that it's a more demanding procedure than total knee arthroplasty and that it's more difficult to align the implant components in order to achieve reproducible and predictable outcomes. I'm no different. When I attempted the uni knees in the past, using manual instruments, the procedures would take longer than my total knee cases and, even after spending that additional time, post-op joint alignment and stability were not always satisfactory. Robotic assistance has eliminated those concerns for me and countless other surgeons. We're also able to preserve more soft tissue, thanks to the use of a precise tool and pre-op planning that eliminates the placement of external cutting blocks and jigs on the bones in the knee.

After exposing the knee joint, surgeons might spend a few extra minutes reviewing the pre-op plan, placing the arrays and registering their locations into the platform's system, but then the robotic burr is primed to resurface the joint in a matter of minutes. Procedures therefore ultimately become faster. In fact, robotics reduces the overall operative times of my unicompartmental knee replacements by 15 to 20 minutes.

It's somewhat of a leap of faith to trust that the robotic burr is shaving off bone precisely where it's programmed to work. Surgeons watch the robotic burr very closely during the first few times they turn the procedure over to it, but they quickly see that the haptic boundaries let the burr resurface the bone only where it's supposed to, so the implant can be positioned only where the surgeon intends it to be based on the planning.

Demand skyrockets
Robotics won't improve the performance of bad surgeons, but the technology will enhance the outcomes of surgeons who haven't done enough uni knees to become proficient, and even improve the consistency and outcomes of experienced surgeons. Once they see the reproducible outcomes robotics affords in potentially 20% of their total knee patient population, they'll be able to quickly build up case volumes.

My physician partners and I experienced this rapid growth in case volumes. We launched our outpatient joint program in 2014. In May 2015, I performed my first outpatient partial knee and total hip procedures using the robotics platform. Six months later, patient demand was so high and the return on investment so significant that we planned to pay off the robot much earlier than expected and decided to add a second platform. For the last 8 months, we've had both systems up and running and case volume continues to be strong.

The robotic platform's $1 million price tag is admittedly steep, but facilities can buy the platform outright, lease it or enter into a capital lease over several years in order to find a financial fit. Besides, the number of cases we've been able to add since bringing robotics online has more than offset the initial investment. OSM