A total knee replacement is a highly effective way to treat knee pain and stiffness due to arthritis or other conditions that cause severe pain and disability. Statistics from the American Academy of Orthopaedic Surgeons (AAOS) suggest that 90% of patients who undergo a knee replacement experience a significant reduction in pain, enabling them to enjoy an active life once more and resume many of the activities they used to enjoy.
What is a total knee replacement?
A total knee replacement is a surgical procedure that involves removing the damaged knee joint and replacing it with a prosthetic (artificial) implant. Knee prostheses are made from hard plastic, ceramic and metal. When it comes to positioning the knee implant, accuracy is crucial as even a fractional misalignment can have a detrimental impact on patient comfort and performance of the artificial knee joint.
This is why many leading orthopaedic surgeons, like Prof Joseph Queally, are now using Mako robotic arm-assisted technology from Stryker to support their surgical expertise during a total knee replacement.
Mako robotic arm-assisted surgery
Mako uses advanced system software to enable surgeons to plan the surgical procedure in advance with pinpoint precision. Everyone’s anatomy is unique so the Mako system uses a CT scan of the damaged knee to create a detailed 3D image of the patient’s knee joint. From this, the surgeon can see precisely which areas to cut away and which to retain, resulting in better and more predictable outcomes.
During the surgery itself, the Mako system guides the surgeon to remain within the limits of this pre-operative plan, using Mako’s high-tech robotic arm to cut away diseased bone and cartilage, guided by the surgeon. Slight adjustments can be made, if necessary, but the objective is to follow the plan as closely as possible to achieve the highest levels of precision.
Research into Mako accuracy and precision
A recent survey by Mayo Clinic Hospital in Phoenix Arizona set out to compare the accuracy and precision of Mako robotic arm-assisted total knee replacements against conventional techniques. The researchers wanted to test out the premise that a Mako total knee replacement is more accurate for positioning of the prosthetic knee joint than a total knee replacement carried out with standard mechanical instruments.
They also wanted to assess whether the fact that the pre-operative plan incorporates data on soft tissue laxity means Mako technology reduces variability between planned polyethylene thicknesses and the final implanted polyethylene – another factor in improve implant performance.
What they did
The researchers reviewed 220 total knee replacement procedures carried out between May 2016 and November 2018 by a single surgeon. Comparing the two approaches, they analysed average deviations from the following planned alignments – planned coronal plane component and overall limb alignment 0° to the mechanical axis; tibial posterior slope 2° and polyethylene thickness 9mm. They also assessed positioning, size and outliers for each group.
There were 103 total knee replacements performed using conventional mechanical techniques and 96 carried out using the Mako robotic arm. The researchers discovered the Mako surgery was more accurate and precise both in terms of component positioning and the thickness of the final polyethylene insert. Specifically, there were significantly lower deviations in relation to mean femoral positioning, mean tibial positioning, mean posterior tibial slope and mean mechanical axis limb alignment. All Mako procedures deviated significantly less from the plan and far fewer knees required a distal femoral recut. Deviation from planned polyethylene thicknesses were also significantly less (1.4 mm (SD 1.6) vs 2.7 mm (SD 2.2), p < 0.001).
The researchers conclude that the greater accuracy and reproducibility of Mako total knee replacements could be increasingly important as surgical procedures advance and precise goals for component positioning are developed, allowing even greater individualisation for the patients.
If you are due to undergo a total knee replacement and would like to find out more about Mako robotic arm-assisted surgery, contact us.
