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Improving patient outcomes for total knee replacements
including the role of robots

By Peter Hardcastle

Total knee arthroplasty, or total knee replacement, is a mostly-effective surgical option to reduce pain and restore function in patients. Despite this, 15 to 20% (most literature has 15%) of patients globally are unsatisfied with the outcome of their knee replacement, usually due to pain, stiffness, or instability.

There are several factors that orthopaedic surgeons, like myself, need to consider to improve patient outcomes. These range from the alignment method that’s utilised, the use of computer or robot-assisted navigation to improve precision, and managing patient expectations.

Goals for the alignment of total knee replacements are changing

A key consideration when planning a patient’s surgery is which alignment method to use.

Traditionally, during a total knee replacement, surgeons use the mechanical alignment method. This aims to ensure that there’s a straight line between the patients’ hip, knee and ankle when viewing it in the two-dimensional, frontal plane. This approach focuses on the bone, often requiring that soft tissue and tight ligaments be released allowing the knee to feel balanced or stable.

However, not everyone is anatomically designed with a straight axis between the hip, knee and ankle. Because the variability of a patient’s limb alignment is not taken into account during a mechanically aligned knee replacement, they are more likely to experience discomfort, instability and loss of motion post-surgery.

Alternatively, the kinematic alignment method takes the patient’s natural anatomy, or kinematic axis, into account and considers the ligament balance of the individual knee. This approach takes a three-dimensional view of the knee, and the implant is placed at an angle that’s aligned with the patient’s anatomy, rather than straight. Ligaments are protected in this approach but some research suggests that wear may be accelerated.

In my opinion, it is acceptable to use the kinematic alignment approach. Overall, patients treated with this method report better outcomes, including better motion. The knee is balanced according to the soft tissue envelope and is stable through its range of motion.

Performing robot-assisted surgery for improved precision

Robotics are increasingly being used to assist in surgery. The improved accuracy in bone cuts and reduced soft tissue injury make them valuable in improving patient outcomes. While they don’t perform the entire surgery, they are a useful tool to assist with accuracy in procedures that require precision and navigation in small areas.

Robots have been used in orthopaedic surgeries since the early 90s. Robotic arms work from 3D images of a surgical area to perform tasks that may include creating a personalised surgical plan, preparation of the bone, placing the implant precisely and balancing it, and giving the surgeon real-time feedback.

Currently there are three types of robots being used by surgeons in South Africa for knee replacement surgery, each with a different benefit. For example, surgeons who use the Mako and Navio robots are less likely to damage soft tissue around the knee because the robot will stop working if the surgeon moves beyond its scope. I use the Navio for partial knee replacements to position the implant better, improving its longevity. The OMNIBotics robot, a robotic tensioner – which I will soon start using for total knee replacement surgeries – includes an instrument to help balance the knee giving real time feedback about the ligament tension and balance.

However, just as each robot has specific benefits, they also have limitations and it’s vital that the surgeon knows what those are. In some cases, it will be difficult to determine what the ligament tension is, while in others one might struggle to determine whether the bone has been cut accurately or not.

Regardless of which robot a surgeon uses, they must still be meticulous in their surgical technique. And of course, it doesn’t help if a surgeon is using a robot to improve accuracy, but not using an alignment method best suited to the patient’s anatomy. The two need to be used in conjunction to truly improve patient outcomes and satisfaction.

Managing patient expectations is directly linked to outcomes

Unfortunately, the way a patient experiences their knee replacement is not only dependent on the skill of their surgeon and the tools used during surgery. Several studies have shown that a patient’s expectation is directly linked to the outcome of their knee replacement surgery.

There is often poor correlation between the surgeon and patient’s view of the outcome. This is because the surgeon is aware of the limitations of the surgery and is realistic about what the outcome will be. As such, it’s vital that patients are properly briefed so that they go into surgery knowing exactly what to expect and what the limitations of the procedure are.

Equally important in ensuring patient satisfaction, is the general care the patient receives in hospital. This includes the level and quality of physician communication, the general hospital environment, and adequate information being provided about medication and discharge.

Essential to a good outcome is pain management and control. A patient who isn’t in pain will keep moving and is more likely to feel like they have benefited from the surgery.

Meticulous surgical technique remains crucial regardless of method

The design philosophy of the knee is another vital aspect to consider and is something I’ll discuss further in a future article. Design philosophy addresses aspects like the patient’s range of motion and the wear on the implant.

As surgeons, we are continuously learning and doing everything we can to improve our technique and the outcomes for our patients. Sometimes this means changing protheses or including robot-assisted surgery in your repertoire, even if the gains are only marginal. At the end of the day, we’re implanting a prosthesis into our patients. While that can never feel totally normal, we strive to achieve the best possible outcome for our patients.

No matter what alignment method a surgeon choses or which robot they use, their technique needs to be meticulous with dedicated attention to detail. Once you’ve decided on your approach you need to be accurate in your planning and precise in your execution. Only by doing this will we be able to improve patient outcomes for total knee replacements.

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