Computer Assisted Total Knee Replacement Surgery 

Total knee replacement surgery isn’t new. It has been practiced worldwide for 40 years, and as might be imagined, the procedure has been refined to the point where hundreds of thousands of people every year are returning to a life of pain-free mobility.

However, standard knee replacement surgery has its limitations—the laws of physics being chief among them. The surgeon’s task is daunting. He must implant the orthopedic device in such a manner that its components—a metal and plastic platform atop the tibia and a metal surface on the bottom of the femur—rub together, or "articulate," at precise angles in order to prevent premature or excessive wear of the implant.

If, during the procedure, a surgeon shaves off bone at an angle just five degrees from perfection, the uneven wear and tear during normal physical activity literally will shave years off the life expectancy of the device. That leads to additional knee replacement surgeries during a patient’s lifetime.

As is commonly practiced today, a surgeon achieves proper alignment through "feel." That is, he uses specialized cutting blocks combined with his bare hands’ years of operating room experience to determine where best to remove bone for the implant. Once the cut is made, the natural bone cannot be replaced. Thus, a carpenter’s advice to "measure twice, cut once" is especially vital in knee replacement surgery.

The new solution

Computer-assisted surgery addresses this issue of alignment with an advanced convergence of multiple medical technologies. Using infrared cameras, fluoroscopic images and simple tracking devices, Smith & Nephew’s computer-assisted knee replacement procedure achieves alignment to within one degree and one millimeter of total accuracy.

How it works

The logic is simple: By combining fluoroscopic images of the femur and tibia with an implant-specific software package, the computer hardware can track the precise position of the patient’s leg, the implant and the surgeon’s instruments at all times during the procedure.

Do not fear—the surgeon performs the surgery. The computer simply puts together all of the information coming in from the patient and the instruments and tells the surgeon where the precise cut should be made. Given that every patient’s knee geometry is different, this level of patient-specific, computer-guided accuracy is unprecedented in the history of knee replacement surgery.

Less invasive surgery

As you might imagine, a surgeon armed with these tools has the ability to achieve better outcomes. As the computer-assisted procedure evolves, it will become less and less invasive.

It has already eliminated the use of an intramedullary (IM) rod—a device inserted down the length of the femur used for determining proper knee implant alignment in relation to the hip joint. Since the data generated by the computer supplants this device, patients undergoing computer-assisted knee surgery may have a reduced risk of suffering fat embolism, caused when the IM rod forces body fat into the patient’s blood stream.

Further, the quality and accuracy of the image provided to the surgeon by the computer will soon enable smaller and smaller incisions while achieving the same successful outcomes. Smaller incisions lead to faster surgeries, shorter hospital stays and shorter rehabilitation.