Setting It Right with a Robot
Focusing on the diseased part of the knee, MAKOplasty can speed recovery.
photograph by Bewuel | Dreamstime
With 19 years’ experience in orthopedics and sports medicine, Dr. Peter Lindy knows the value of total knee replacements. “They’re wonderful for those who need them and they have a great success rate,” says this surgeon with East Memphis Orthopedic Group. “However, when you ask people how happy they are [after the procedure] they’ll say it’s better than what they had. In other words they’re happier, but how happy are they? You really can’t make people 100 percent again.”
That’s why Lindy’s a believer in partial knee replacement because it addresses the specific problem — primarily the degree of arthritis — within the individual knee joint. “Repairing just the bad part is attractive to me [because] in sports medicine the goal is to get people back to a level of functioning. So let’s just fix what’s wrong.”
And zeroing in on what’s wrong and making appropriate adjustments to “fix” it has became more precise with a new technology called MAKOplasty partial knee resurfacing, which has been available in Memphis for about a year. Lindy is one of only two local doctors trained in the procedure, which he’s been performing since late spring at St. Francis Hospital-Memphis, the first facility in Memphis to acquire this technology.
“When we talk about the knee joint, we talk a lot about the three bone compartments — the medial, or inside part of the knee; the lateral, or the outside part; and the patella femoral behind the kneecap,” says Lindy. “If arthritis is involved in all three parts, then it makes sense to replace them all [with metal or plastic implants or prosthetics].” But Lindy stresses that any discussion of total knee replacement should also address the ligaments that control the knee’s motion. “The two in the middle, the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL), are so important. In order to do a total knee replacement we have to sacrifice these ligaments whether they’re really damaged or not. And when we remove these ligaments, we change something — and that’s the concept of feeling normal and having the ligaments maintain that normal balance.”
In the manual (or traditional) version of partial knee replacement, as opposed to MAKOplasty partial knee resurfacing, Lindy explains that “ligament balance is done by feel while the patient is asleep. I might carefully remove a little more of the bone and change the position of the implants I’m using so that the tension or balance is more appropriate to how I feel it should be.
“With MAKOplasty,” he continues, “I’m doing that in a virtual setting on a computer with a robotic arm and a more precise, minimally invasive technique.”
First, however, the patient undergoes a series of x-rays that confirms the diagnosis of arthritis in a specific area of the knee. “Then we obtain a special sequence of a CT scan that is fed into the robot’s computer,” says Lindy, “and from that we create a three-dimensional model of the knee. It’s a fairly accurate bone description of what the end of the femur bone looks like and what the top of the tibia bone looks like, and it shows us what the disease process is.”
Using that computer model, Lindy selects the appropriate-sized prosthesis; cobalt chrome is used for the femur and titanium for the tibia. “These implants come in about eight different sizes with small increments between each one,” he explains.” And with this 3-D model on the computer screen, we determine where the implants would best fit.”
Bear in mind, he adds, that “all this is done on the computer before the patient ever gets in the operating room.”
On surgery day, when the patient is on the table, computer devices are attached to the femur and tibia bones, and the devices communicate to the robot computer complex just where the knee is located. In other words, “the computer knows the CT scan model of the knee but doesn’t know where the actual knee is in relation to the robotic arm. So now we’re telling the computer that information.”
Next comes what Lindy describes as “the elegance of the procedure.”
“We’ve registered the knee joint to the computer, and so now we take the knee through a series of movements where we try to balance the ligaments to get them at the tension they should be. As we do this, the computer records where we want that tension. And all this is done through very sophisticated and clever algorithms. We shift the components on the computer, and through the algorithm the computer knows how to bring this ligament to the tension we desire. And it will tell us how the movements we’ve made are affecting other ligaments. So I get this immediate feedback, something I get through no other procedure.”
Once the optimal position of the implants is decided, Lindy brings in the robotic arm. It’s attached to a 6-millimeter burr, or round cutting device. While he holds the burr, the computer guides him to the place that needs to be resected — or surgically removed — and tells him how much needs to be cut in order to fit the chosen prosthesis in the right place.
Even with such precise technology, Lindy doesn’t rule out the human factor. “Basically we have a plan, we execute it, and it should come to a good result. But there’s still need for a surgeon’s technical ability to make sure it all works the way we plan it. Bottom line: Is it correct in the patient?”
So far, he adds, his patients have been pleased with their MAKOplasty knee resurfacing. “One lady said, ‘Why couldn’t you do this on all my other joints?’” he recalls with a smile. “It’s a very comfortable procedure.” Certainly it results in less pain, minimal hospitalization, and more rapid recovery that allows patients to get back to golf, tennis, and other low-impact activities. It also means less implant wear and loosening, a smaller scar, and a more natural-feeling knee.
“As I said when we started out talking,” Lindy recalls, “nothing gets you back to 100 percent. My goal is to get you as good as you can be and as active as you can. That’s going to help you in the long run.”