Advanced technology personalizes knee implants
Two months ago, Reni Witt-Kriz, 62, was in so much pain she was hardly able to walk after more than a decade of progressive knee pain and numerous treatments that yielded temporary relief.
The Ossining resident has been walking effortlessly and without pain since orthopedic surgeon Eric Grossman outfitted her with a new, customized, 3-D-created knee implant.
“I”™m not climbing the Alps, still, I”™m on my way,” Witt-Kriz said recently at Grossman”™s CareMount Medical office in Mount Kisco.
Now in her third month of physical therapy, she remembered the 10-year progression of deterioration and pain in her left knee. Prior to her surgery, she tried many options, including Hyalgan treatments administered by her sports medicine physician, Seth Shifrin.
“I was getting quite a bit of relief from the Hyalgan injections into my knee,” she said. Derived from hyaluronan, the gel substance is found within the body with higher amounts in joint tissue and fluid that fills joints.
“Every six months I”™d return for a shot and it would last until the next shot,” Witt-Kriz said.
When the injections stopped working, she said, Shifrin referred her to Grossman. He showed her a ConforMIS implant and explained the 3-D image would be personalized for her anatomy.
Grossman is among the first surgeons in the United States to use this technology for total knee replacements. “We”™ve been doing three-dimensional imaging for a long time,” he said. “More recently we”™ve done 3-D preoperative navigation, whereby we navigate the area to be operated upon before making the 3-D image.”
The difference between other companies using 3-D technology and Bedford, Mass.-based ConforMIS, he said, “Is this company uses 3-D technology for implants using principles that have been around for 50 years. We create proper alignment and that alignment is based off a patient”™s hip and ankle center.”
Implants are made from a combination of cobalt chrome, a material that”™s been used for 50 years, Grossman said. “It”™s a metal alloy that has good durability and strength.”
Knee replacements made from 3-D imaging differ from traditional knee implants, he said, “But there”™s always a little bit of play. The Holy Grail of knee replacements is to replicate hip replacements, which is a simpler procedure and feels lifelike. We as surgeons are always trying to replicate lifelikeness.”
“If you looked at a knee model, then you”™d see you create almost a rectangular space. And you align the ligaments on the side to keep it tightly balanced,” Grossman said. “We recreate the anatomy the way it”™s supposed to be in its natural state. Because of the nature of knee replacements, not all implants have the same tension or fit.”
Witt-Kriz stood up to emphasize his point. “From day one I felt like this is my knee, except it was new and strong,” she said, and pointed to her left leg.
Hours after her surgery, the physical therapist came into her hospital room and told her to swing her legs over the side of the bed. “I was able to do that,” Witt-Kriz said. “Then she asked me to stand up. And I stood up. And when she asked me to take a few steps, to my amazement, I was able to walk a few steps.”
Witt-Kriz walked into the hallway and back, using a walker. “I couldn”™t believe it.”
“Before the surgery I was in constant pain every day and I couldn”™t walk any more,” she said. “And I was surprised after the surgery since I did not anticipate going home so quickly.”
Common indications are inhibited instability, a feeling that something”™s “not right” and a clicking sound.
“If someone wants to play tennis, for example, the person might not because the knee implant doesn”™t feel right. We”™re always looking for that stability that creates a natural feeling.”
Grossman said candidates for 3-D knee implants are selected two ways.
“I get a sense if the patient is conservative and wants to know about 20 years of data or is someone who hears about a new method and says, ”˜That makes sense to me,”™” he said. “I”™ve done my research and know this uses enough traditional elements that I”™m comfortable.”
The other factor is ascertaining if the patient”™s knee can accept the implant. “Someone who had major trauma or a significant deformity and bone loss to the area might not be a candidate,” he said.
Grossman received his medical degree from Jefferson Medical College and completed his internship and residency training at Thomas Jefferson University Hospital in Philadelphia. His fellowship training in adult reconstruction and joint replacement orthopedics was at The Rothman Institute at Thomas Jefferson University.
When asked if there is less recurrence of instability or injury with patients who have 3-D-created implants, Grossman said medicine is still in the early stages using this methodology.
ConforMIS”™ clinical studies show its technology can lead to superior outcomes that include better function and greater patient satisfaction as opposed to traditional implants manufactured in a limited range of sizes.
“In terms of what the literature has been producing, there have been no reports that have shown 3-D imaging to be superior to other implants,” he said. “What 3-D navigation does is reduce the chances of instabilities and mismatched implants.”
Insurance companies are sometimes hesitant to cover knee replacements made from 3-D imaging technology, Grossman said. “We are running into (situations) where the lack of valid evidence to support that this is scientifically needed inhibits the process, mostly because advanced imaging either a CAT scan or an MRI, is needed.”
While an MRI is necessary for diagnosing the need for knee replacement surgery, he said, patients who choose 3-D imaging replacements will have an MRI to diagnose the knee and another MRI prior to surgery, which insurance companies not familiar with this medical procedure view as duplicate tests.
Witt-Kriz said she is looking forward to finishing physical therapy and becoming more active as the weather gets warmer.