Changing my religion: Robotics in knee arthroplasty

Unfortunately, 15 to 20% of patients globally are unsatisfied with the outcome of their knee replacement, usually due to pain, stiffness, or instability. In this article, I explore whether robotic-assisted knee replacement surgery improves patient outcomes. I explain how the Omnibotics and Navio systems work, discuss what the benefits and limitations of robotic-assisted surgery are, and look at what the future of robotic-assisted surgery in might hold.

I call this equipment ‘robots’ for ease of reference in this article. However, these devices aren’t actually robots because they don’t perform surgery without direct human control. The United States Food and Drug Administration (FDA) considers robotic-assisted surgical systems as a type of computer-assisted surgical system.

Corin’s Omnibotics: Getting the correct tension in TKAs

The Omnibotics system, which I recently used for the first time, contains two components. The first is a robotic-assisted femoral cutting device, which maps the femur before the surgeon starts cutting the tibia.

The second component is a sensor-based ligament balancing system, which is the part of this device that I really appreciate. This robotic tensioner gets placed in the knee to help determine the correct knee ligament tension, usually between 80 to 90 Newtons. As you move the knee, a graph shows whether the ligaments surrounding it are too lax or tight. We then use a cutting block to cut in the correct places, based on the tension we’ve chosen.

Real-time feedback about the soft tissue in the knee ensures that we don’t release more tissues than necessary. This guarantees a kinematic alignment, so that the patient’s new knee is aligned the same way it was previously, rather than being put in straight. To explain further, this means that a patient who has bandy legs won’t leave their knee replacement surgery with one straight leg and one bandy leg. On top of this, the ligaments and soft tissue will remain balanced because of the real-time feedback we received from the robot’s sensors.

Smith and Nephew’s Navio: Protecting soft tissue in partial replacements

Smith and Nephew’s Navio robot can be used in partial and total knee replacements. I have been using the Navio in partial knee replacements for more than a year now. During surgery, this device maps the whole femur, suggests an implant size as well as the position of the implant. The robotic burr (saw) retracts if the surgeon tries to cut outside of the predefined boundaries helping to limit unnecessary soft tissue injury. As with the Omnibotics, real-time feedback helps position the implant accurately.

Both the Navio and Omnibotics systems are imageless. The patient isn’t required to have CT scans or X-rays before the surgery. Everything is planned in theatre, which has a positive cost implication for the patient.

The benefits

Several benefits to using robotic assistance in knee arthroplasty surgery are emerging, despite the use of these devices being in its infancy.

• There is significant improvement in bone cutting precision when trying to reproduce ideal leg alignment
• Implants are placed more accurately
• Revision rates are reduced, which means there’s less chance of a knee replacement needing to be redone in the 10 to 15 years post-surgery due to incorrect implant placement or soft tissue issues.
• There is increased implant survival
• Overall recovery time is potentially decreased
• There is less variation in execution

The limitations

There are still several limitations to robotic-assisted knee arthroplasty surgery, owing largely to the newness of this field. These are some of them.

• The robots available in South Africa are closed systems which means they can only be used with the implants made by the same parent-company. Different surgeons use different implants, so it’s not possible to have one robotic system per hospital.
• The increased procedure time using a robotic assistant can lead to a higher risk of infection.
• There is some hesitancy around the uptake of robots in orthopaedic surgery in South Africa because there is no evidence yet that patient outcomes are improved by robotic-assisted knee arthroplasty.
• The software and hardware of these devices is upgraded frequently. This makes the decision to buy a multi-million Rand piece of equipment a difficult one for hospitals if it’s likely to become outdated very quickly.

What the future holds for robotics in knee arthroplasty

The field of robotic-assisted knee arthroplasty is growing rapidly. This is evident by the increase in publications on the topic. In 2015, 2,500 publications covered robotics in orthopaedics. This rose to 6,500 publications in 2020.

However, we need longer term studies to assess all the outcomes of robotic-assisted knee replacement surgery to determine whether the use of these devices will ultimately have a positive, long-term impact on patient outcomes. While it’s difficult for all surgeons, myself included, to hand over control to a robot, I believe that the hesitancy around robotics in orthopaedics will be largely squashed if we can prove that this exciting, new technology improves patient outcomes in the long run.

I encourage the manufacturers of these robots to market them in South Africa, as open systems which can be used with multiple types of implants, to improve their uptake. Hospitals need to explore whether renting or buying this technology is the best option for their facility, its orthopaedic surgeons, and their patients.

As surgeons we want the best outcomes for our patients, and hopefully after a few more years, we will have the data we need to see whether robotics can help produce more satisfied patients. Despite some of the current uncertainties, I am excited to be part of this quickly evolving field and am looking forward to seeing what the future holds for robotic-assisted knee arthroplasty.