3D technology provides custom knee implants.
Knee replacement surgery has come a long way since the first modern total
knee implant operation was performed in 1974. One of the pioneering surgeons
who developed and implanted that artificial knee was a physician named
Chitranjan Ranawat, M.D. Today, a student of Dr. Ranawat is pioneering
the latest advancement in total knee replacement at The Joint Institute
at Saint Barnabas Medical Center.
Richard Rosa, M.D., administrative director of
The Joint Institute, works with a biomedical company which makes fully customized implants
that are “printed” using 3D technology to exactly match the
anatomy of the patient’s knee. “The first knee implants used
by my mentor were very basic in design,” Dr. Rosa says. “They
were just for elderly people with severe arthritis. Today, people are
more active and want to stay active, so they require more out of their
knees. Customized knee implants are more anatomically correct in design.
The one I use is an exact replica of the shape and size of the patient’s
knee before they developed arthritis.”
Standard knee implants, he says, come in about six different sizes. “We
had to take an off-the-shelf prosthesis and match it as close as we could
to the patient. But no two knees are exactly the same shape.” A
slight mismatch in where the implant meets the patient’s natural
tissue—called the “overhang”—can be problematic.
“Even an overhang as small as 3 millimeters can cause significant
pain if tissues rub against the implant. Today, 1 in 5 patients still
complains of residual pain or that the knee doesn’t feel right,”
Dr. Rosa says. “With custom design, you match all the small to major
variations in size and shape, so there is perfect fit and ligament balance
throughout the patient’s range of motion.”
Richard Rosa, M.D.
Before surgery, Dr. Rosa orders a special computed tomography (CT) scan
of the patient’s knee. That scan is converted into a 3D model by
mapping the surface of the joint, including the area of disease, correcting
the model for arthritic deformities such as bone spurs, cysts or flattening
of the joint. That 3D model is then used to design and print the implant
and the surgical cutting guides that also must be unique to each patient.
The company delivers the prosthesis and guides in a kit a few days before surgery.
The advantage to all this, Dr. Rosa says, is a knee that feels much more
natural. “With standard off-the-shelf knee replacements, we needed
to release and balance the ligaments and other soft tissues to achieve
stability and range of motion. In effect we were balancing the knee to
match the implant,” he says. “The custom implant exactly matches
the patient’s normal ligament tension, so this soft-tissue balancing
is rarely needed, in fact only in knees with severe deformity. Eliminating
this need decreases the extent of the surgery, decreases blood loss and
Custom knee implants match a patient’s normal ligament tension. This
leads to a decrease in the extent of surgery, and reduces blood loss and pain.
As a result, most patients are able to leave the hospital two days after
surgery. Recovery is typically much quicker. “The first person I
used this with was working in his yard for eight hours, just three weeks
after surgery,” Dr. Rosa says. “His wife came home and he
asked her, ‘Are you ready?’ ‘Ready for what?’
she asks. ‘Ready to go shopping. I’ll take you to the mall.’
This, after eight hours in the garden. That’s not common, but people
typically feel great in two to three weeks.”
The implant isn’t the only reason for this success. The Joint Institute,
which was formed about a dozen years ago, is a special unit dedicated
to hip and knee replacement surgery. Every patient attends a seminar prior
to surgery to learn what to expect before, during and after the operation.
“We believe that educated patients are better patients, because
they can better help themselves,” Dr. Rosa says. “During surgery,
we follow the standard protocols, and we believe in aggressive rehab therapy.”
That starts with progressive pain management using fewer narcotics, which
helps get patients up and moving sooner.
That’s just what today’s younger knee replacement patients
want. “People in their 50s and even late-40s who have arthritis
want to maintain an active lifestyle,” Dr. Rosa says. “We
are doing about 600,000 knee replacements a year nationally, and that
should go up to a million in the next 10–15 years. I use the customized
knee on almost all my patients now—in fact, I just did my 300th
case.” Dr. Rosa mentions one patient in particular, who came to
a presentation that he was giving recently. “I didn’t know
he was coming, but he stood up and said he needed to come and talk about
his experience,” Dr. Rosa recalls. “He told the group it was
the best thing that ever happened to him. It brought him back to the living.”
To find out more about the Joint Institute at Saint Barnabas Medical Center,
please call 973.322.9908 or visit