Robotic Knee Replacement

Knee replacements are successful operations that are designed to relieve pain in patients with knee arthritis. Once the cartilage in the knee joint wears out, the underlying bone is exposed. When bone rubs on bone, it can cause arthritic pain. In the early stages of knee arthritis, non-surgical measures such as anti-inflammatory medication, weight loss and physiotherapy can help. With advanced knee arthritis, a knee replacement can help alleviate pain and improve mobility.

Why consider a robotic knee replacement?

Mako Robotic Knee Surgery

Mr Pai performing robotic knee surgery

It allows your surgeon to plan your knee replacement and execute that plan with accuracy.

The technology behind knee replacements has been evolving since the first modern knee replacement, which was performed in 1968. Despite the use of modern knee replacement components, data shows that 1 in 5 patients are dissatisfied with the outcome after having a knee replacement. Surgical techniques and knee replacement prostheses are constantly being refined in an effort to improve patient satisfaction.

What techniques are used to perform a knee replacement?

There are four main techniques that can be utilised to perform a knee replacement:

  1. Conventional knee replacement

  2. Navigated knee replacement

  3. Patient-specific knee replacement

  4. Robotic knee replacement

Conventional knee replacement

A conventional knee replacement is performed using jigs that assist the surgeon to make the bony cuts to allow implantation of the knee replacement prosthesis. It is important to ensure accurate alignment of these bony cuts so that the knee replacement can last for many years. The jigs are positioned using anatomical landmarks within the knee. However, these anatomical landmarks can be variable between patients and can be affected by several other factors. Even in experienced hands, there is a degree of variability with the final implant position using conventional techniques.

Navigated knee replacement

Computer navigation was designed to reduce this variability by using trackers attached to the patient that relay information to a computer. The trackers allow more accurate placement of the jig, which reduces variability. Data from the Australian Orthopaedic Association National Joint Replacement Registry (AOA-NJRR) shows that patients younger than 65 whose knee replacement was performed using computer navigation had a lower revision rate.

Patient-specific knee replacement

Patient-specific knee replacements are another form of technology designed with the hope of improving accuracy. Preoperative imaging of the patient’s knee is used to generate a virtual model that will allow a patient-specific jig to be manufactured. The jig is applied to the patient’s knee, and the surgeon performs the bony cuts using a standard saw. Even though the jigs used are custom-made, the implant itself is not custom-made for the patient, and there are still instances where the jig may not fit accurately onto the patient’s knee intraoperatively. In these cases, the surgeon may need to revert to a conventional technique to make accurate bony cuts.

Robotic knee replacement

With robotic knee replacement surgery, the surgeon uses a saw or burr that is linked to a robot to perform the bone cuts with accuracy. There is a significant amount of literature that has shown that the accuracy of robotic knee replacement is higher than conventional means. There is ongoing research that will determine whether this will translate to better function or prosthesis survival.

How is a robotic knee replacement performed?

Robotic-assisted knee replacements have improved on computer navigated technology.

Steps involved:

  1. A preoperative CT scan of the knee is used to create a virtual model.

  2. The model is used to plan the knee replacement implant size and positioning.

  3. During the operation, anatomical landmarks within the patient’s knee are used to verify the positioning suggested by the virtual model prior to bony resection.

  4. Mr Pai performs the bony cuts with the assistance of the robot using pre-planned anatomic boundaries.

  5. Motion capture technology is then used to check the kinematics of the knee, which allows surgeons to fine-tune the bony cuts or make releases in the soft tissues to balance the knee.

It is important to know that all of the surgery will be performed by Mr Pai and that the robot is only used for assistance while making the bony cuts. Mr Pai still controls the robotic arm while performing the surgery.

Robotic Knee Surgery Plan

An example of a robotic knee surgery plan using Stryker Mako technology. The plan is prepared prior to surgery and is based on a CT scan. It can be adjusted intra-operatively to fine-tune the soft tissue balance of the knee.

What are the advantages?

Robotic knee replacement surgery has improved accuracy. The pre-operative plan can be executed to within 1 millimetre and 1 degree.

Robotic-assisted knee replacements have more accurate implant positioning than conventional total knee replacements. There is currently no long-term data available for analysis to help draw conclusions about better functional outcomes or improved survival.

Early data for partial knee replacement from the AOA-NJRR shows that the revision rate was almost halved for robotic partial knee replacement at 3 years follow-up. Partial knee replacements require training and experience to perform successfully. It is well established that surgeons performing partial knee replacements regularly, have better outcomes than those with less experience. The tolerances for implant malposition are much lower in partial knee replacement, and this may be the reason for the improvement in revision rate when robotic assistance is used.

Short-term follow-up shows a lower revision rate for robotically assisted partial knee replacement.

Results from the Australian Orthopaedic Association National Joint Replacement Registry show a survival advantage for robotically performed partial knee replacement.

Robotic knee replacements also have less post-operative pain and a faster time to discharge from hospital. This is thought to be due to decreased trauma to the surrounding soft tissues in the knee, as the robot works to a pre-planned boundary.

What are the disadvantages?

Robotic knee replacement surgery is a relatively new technology, and we are still awaiting long-term data about its outcome. Despite using robotics to achieve accurate bone cuts, the knee replacement implant that Mr Pai uses is well-established and performs well.

Some disadvantages of robotic knee surgery are that the surgery takes slightly longer than a conventional knee replacement. Performing robotic knee surgery requires specific training and accreditation by hospitals to ensure it is used by surgeons with an appropriate amount of experience. The robot is not available at all private hospitals in Melbourne as there is a significant cost for the hospital to purchase and service it.

Like navigated knee surgery, robotic knee surgery requires the placement of tracking pins around the knee. These pins provide the robot with data about the position of the knee in relation to the robotic arm so the saw cuts can be performed accurately. There is a rare risk of pin-site infection and fracture that can occur.

What robot does Mr Pai utilise?

Mr Pai has had extensive overseas and local training to use the Mako robot. He performs robotic knee replacement surgery at Holmesglen Private Hospital. The Mako robot is used with the Stryker Triathlon total knee replacement and the Stryker Restoris partial knee replacement prosthesis. These knee replacement prostheses have a long track record and have excellent results on the Australian Orthopaedic Association National Joint Replacement Registry.