The debate on robotic vs patient specific implants for knee arthroplasty is getting hotter by day as more studies with conflicting prospective are published. An elite group of Indian orthopaedic surgeons share their insights on the same By M Neelam Kachhap
Innovations in knee arthroplasty concepts have always been targeted towards patients as means of achieving more consistent outcomes. However, the best match between new technology and clinical experties is the key to achieve good surgical outcomes. Currently, two new technologies – robotic techniques and patient-specific implants are making waves in the orthopaedic market.
Precision and alignment are the core of orthopaedic surgery and takes a fair bit of practice to master the art. The advent of robotics for clinical surgeries was hailed as the next breakthrough in medicine but somehow that hype has not translated into rapid adoption by surgeons. Orthopaedics has its fair bit of robotics. A new class of robotics for precision sculpting is now in the market. They bring the advantages of accuracy, precision and rapid reaction to the surgeon. These intelligent tools are said to simplify difficult and heavily instrumented procedures. Some of the technologies present in this category are The Acrobot Sculptor (Stanmore Implants Worldwide), Mako Rio (Stryker Corporation) and the Precision Freehand Sculptor – “PFS” (Blue Belt Technologies)
Dr Klaus Radermacher from Helmholtz-Institute in Germany seeded the idea for patient-specific templating in the 1990s. Recently, a lot of a renewed interest is centred around this image-to-implant technique. It involves three-dimensional (3-D) surgical planning of the knee arthroplasty with unique custome cutting and drilling.
The approach relies on CT or MRI imaging to customise the knee arthroplasty by capturing the patient-specific knee anatomy including the cartilage, and results in custom-fitted positioning guides. The images are also used to design and manufacture custom implants using rapid prototyping technology. Some of the products in this category are Patient Specific Instruments (Zimmer, Inc); Visionaire patient-matched instrumentation (Smith & Nephew), OtisKnee (OtisMed), and Signature (Biomet).
Many of these technologies are not widely accessible in India. But some surgeons have tried these innovative technologies. They provide their perspective on utilising these technologies in India.
PSI differs from navigation (computer-assisted) in that it shifts the bone landmarks required for surgery from intraoperative to preoperative planning . Many studies have shown that it has little impact on surgical procedure. As far as I know, no study has assessed implant survival, function and patient satisfaction rates. Besides, the pre-operation planning in PSI is done by an engineer hence chances of error do creep in.
Advantages of both PSI and navigation are that both are theoretically more accurate. However, the prohibitive cost of both the technologies is their biggest disadvantages. Also the being a new technologies, there is very little evidence to prove efficacy.
Computer-assisted total knee replacement (TKR), patient specific implant (PSI) and patient specific navigation – Is it ready for prime time?
The answer is a big NO. I feel both, PSI and computer navigation in TKR, are mostly used as a marketing tool, both by the implant companies and corporate hospitals to increase the volume of surgeries and implant usage. It brings in a snob value to a well performed TKR done by routine eye-balling as by most surgeons.
The number of people doing it is very minimal and a lot needs to be done still to see its usefulness and usage by most surgeons.
– Dr Deepak Inamdar, Chief Consultant Orthopedic and Joint replacement surgeon, Orthoone, Bangalore
Human being is a very advanced robot created by God!
Man-made robot has several limitations and will only work as per the programme and cannot ever perform anywhere close to humans as far as knee replacement surgery is concerned, simply because the variables are too many ! Besides the exorbitant cost of the robot, it may even be dangerous. Recently, I met a professor at IIT who is into robotics for factory machines and he too was of the opinion that since the knee moves during surgery and deformities are variable and gaps are variable it could be dangerous.
The other variety is the computer navigation for knee replacement which is being currently overused and being used more for marketing by some surgeons especially in Mumbai! It is neither cost effective nor particularly surgeon friendly, besides there is no software for revision surgery.
The patient-specific instrumentation or the trumatch is better in the sense that it reduces surgical time and almost guarantees good component positioning even for an inexperienced surgeon . However one has to send the MRI of the knee to the US to get the patient-specific jigs manufactured and it takes approximately four weeks for this and costs around Rs 50,000 in addition to the cost of the implant!
The trumatch technology is better and is a good alternative for those cases where navigation has to be used due to the inability to use routine jigs!
If the time period for manufacturing patient specific jig reduces and the cost is also affordable then it comes across as the best logical choice for all cases of knee replacement. It is safer because the medullary canal is not violated and this reduces chances of embolism.
The jigs are made by proper measurements and in addition, the experienced surgeon can compensate for any defects that may exist!
The idea of all these gadgets is to improve the bony cuts and component positioning ! This is one aspect of surgery! Others being asepsis, ligament balancing, cementing technique, hemostasis and other multiple factors for which there is no option other than a skilled, trained and experienced orthopaedic and joint replacement surgeon!
The cost of the robot to deal with knee replacement surgery goes into crores! Training doctors, paramedics and OT staff will also take the cost to new levels! Maintenance and upgradation of software and technology would be a separate issue! We are currently at infancy with regards this aspect! It would be experimental for a long long time!
We already have results of knee replacements with longevity of 20-25 years, and these are without using computer navigation or robotics or patient specific instrumentation !
Therefore, one has to really have a very strong technology which can better these results! Otherwise why change? Therefore the logic of trumatch, which only helps the surgeon without unnecessary burden to speeden the surgical time and improve upon the desired component positioning percentile wise is acceptable. This also reduces the implant inventory. It’s like a tailor-made suit rather than a readymade size option where one gets small, medium, large, extra large and double extra large.
– Dr Rajesh Dharia, Consultant Joint Replacement Surgeon, Mumbai
The goal of the surgeon during a total knee replacement is to get neutral alignment. However, studies have shown that even experienced surgeons don’t always achieve this perfection.
Hence computer navigation systems were introduced about a decade ago to achieve perfect alignment. In this system, pins were drilled in the thigh and leg bones away from the knee. These pins were attached to sensors. The sensors relayed information to a processor located elsewhere. The monitor of the processor displayed the accuracy of the bony cuts and bony alignment. Based on these, the surgeon could intra-operatively fine tune the cuts and positioning to get perfect alignment. As mentioned previously, the surgeon had to shift his gaze back and forth from the operating field to the computer monitor located elsewhere. This computer navigation system also requires intensive capital investment.
A different approach toward this goal was adopted with PSI. This required additional pre-operative imaging. The images were transferred electronically to engineers elsewhere. The engineers used computer-aided design to manufacture custom fit cutting tool for each patient. These patient specific instruments were shipped to the surgeon after an interval of a few weeks. Hence there is a time lag involved between the planning and execution in this process. Many patients don’t want to wait. This is where the new technology comes into picture.
I have recently introduced the ‘I-Assist’ for knee replacement. It has gone beyond patient specific instruments. Robotic knee replacement was not feasible in India because of the high costs.I was in favour of patients specific instruments before but I have now moved on to surgical guidance system. Earlier navigation systems required the back and forth transfer of the surgeon’s gaze from the operating field to a computer monitor elsewhere, several times intra-operatively.
The device integrates into the operation by requiring no complex imaging equipment and additional surgical incisions.
A sizeable number of young patients have additional complications in the leg that make a knee replacement difficult. Patients from Asia and Africa present with malunited thigh and leg fractures secondary to a previous accident. They have developed post traumatic knee arthritis as a result of these accidents. Bony deformities within the knee and outside preclude use of all previous modes of instrumentation. The use of conventional instruments which rely on intact straight bones is impossible. Conventional computer navigation is also inapplicable as it requires intact bone within the knee joint. PSI is also impossible to design with bone loss and extra articular deformities. It is vital to get perfect alignment as there is a positive correlation between accuracy and long term survival of the implant. A functional total knee replacement has to be well aligned, which implies that it should lie along the mechanical axis and in the correct axial and rotational planes.
– Dr AK Venkatachalam, Consultant Joint Replacement Surgeon, Chennai
Incorrect alignment will lead to abnormal wear, early mechanical loosening, and patellofemoral problems. There has been increased interest of late in total knee arthroplasty with robotic assistance.
Some cadaveric studies from Korea have shown that robotic knee surgery is more accurate compared to conventional surgery.
Conventional surgery achieves neutral alignment (within 3° of the mechanical axis) only 75 per cent of the time, and coronal suboptimal alignment greater than 3° correlates with worse outcomes.
Currently, two systems have been approved by the US Food and Drug Administration (FDA) and are commercially available in the US—RIO (MAKO Surgical, now owned by Stryker Corp) and ROBODOC (Curexo Technology).
The current MAKO system is a semi-active system controlled by the surgeon. It provides both auditory and haptic feedback, limiting milling of the tibia and femur to certain regions. Prior versions required rigid fixation to a frame, but newer systems have a dynamic tracking feature that results in better implant positioning primarily in unicompartmental knee replacements.
However it takes an average of 25 minutes longer to perform using the Robodoc system. An early trial reported a 41-minute setup time for the robot, 7.5 minutes for registration, and 34.8 minutes for robot-assisted burring. By the tenth case, however, surgeons were able to shave 20 minutes from the entire procedure to average 120 minutes for the entire surgery.
Overall, the use of robotics for TKAs and UKAs has demonstrated the ability to improve component positioning in some cases; however, no study has demonstrated improved functional outcome in near-term follow-up. This may be due to limited sensitivity of clinical outcome measures or limited follow-up period. Longer term follow-up will be needed to demonstrate whether the improved positioning will result in clinically significant improvements in patient outcomes.
Custom cutting blocks are an alternative approach to improve alignment over conventional techniques, but one early study reported that their use does not lead to improved component alignment. However, time in the operating room was less with the blocks than with conventional approaches.
Robotic systems and custom blocks have several drawbacks. They often require a preoperative CT to perform the necessary image registration, thus exposing patients to additional radiation over a typical preoperative TKA evaluation. All robotic procedures have been found to require additional surgical time in most circumstances. This raises concern about the correlation of surgical time with infection risk. In addition, the learning curve can be substantial, with a decrease in surgical time within about 20 cases. Finally, depending on the type of registration used, there can be a risk of pain or fracture from the fixation system.
Perhaps the largest question underlying robotic surgery is the cost-benefit trade-off. Incorporating robotics into a practice requires the upfront capital expenses for acquiring the robot, the additional costs for servicing the robot, and the generally increased cost of disposable equipment used for each surgery. The initial capital requirement can approach the $1 million mark for some systems. In an era of cost-benefit awareness, substantial evidence supporting improved clinical outcomes must distinguish systems that are truly beneficial from systems that support the marketing of a robotic service line.
Clinical outcomes, as assessed by WOMAC and Hospital for Special Surgery functional scores, were no different between the groups at follow-up (one year for the bilateral knee study and approximately 3.5 years for the randomised study).
Robotic assistance has the potential to be an exciting new addition to the long list of technologies that have incrementally improved the practice of arthroplasty, however newer implants have evolved with better minimally invasive instrumentation and soft tissue friendly features with infinite sizing options allowing a more natural knee kinematic range of motion.
– Dr Kiran Kharat, Senior Consultant, Joint Replacement Surgeon, Pune
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