Salvage Knee Implant Stands the Test of Time

First-of-its-kind research helps a growing number of people at risk of leg amputation

CHICAGO (Sept. 15, 2015) — There’s new hope for the tens of thousands of people who risk losing their leg because of severe knee damage. A first-of-its-kind study published in the Journal of Arthroplasty shows the effectiveness of a special implant in preventing amputation for up to two decades.

These findings most impact people with few to no surgical options because of a knee infection, loose joint, or significant bone loss.

“Previous implants were associated with a high complication rate and lacked long-term durability, often failing in under three years. It begged the question: should this surgery be done?” said study co-author Henry Finn, MD, F.A.C.S., director of the Chicago Center for Orthopedics, chair of the Department of Surgery at Weiss Memorial Hospital, and professor of Orthopedic Surgery at the University of Chicago.

“Our goal always is to perform as few surgeries as possible in a person’s lifetime, so proving this implant could last about 20 years is reassuring to patients as well as surgeons that potential subsequent surgeries will be minimized,” Dr. Finn added.

Long-term data on knee revision implants is just starting to take shape as the medical community builds a registry to better note outcomes for this revision and limb salvage procedures. This study will serve as a baseline for showing longevity, durability, and reliability of various implants.

The study focused on the Orthopedic Salvage System (OSS) featuring the Finn™ Knee, a rotating hinge-knee implant designed by Dr. Finn. It analyzed outcomes over a nearly 20-year period.

THE JOINT-SAVING IMPLANT

The prosthetic knee implant is designed to salvage severely damaged knees caused by multiple previous surgeries, infections, trauma, tumors, congenital deformities, and a variety of other conditions affecting the knee that result in bone damage.

Made of titanium, cobalt chrome, and polyethylene, the rotating mechanism allows for knee stability but with enhanced durability by its design and fixation to bone.  Stems attached to the joint connect to the thighbone and shinbone, securing the new knee in place.

The Finn Knee has been recognized as one of the most significant advancements in the field of orthopedics by the American Academy of Orthopaedic Surgeons (AAOS) in its 75 years of existence. The FDA approved the device in 1991, in a decade marked by rapidly advancing technology.

To date, approximately 23,000 Finn Knees worldwide have helped patients at risk of losing their leg.

“The patients most in need of this technology are the ones who face leg amputation or knee fusion because they have major bone loss and no ligaments to hold the knee in place,” said the study’s first author, Yasser Farid, M.D., Ph.D., surgeon at the Chicago Center for Orthopedics. “They essentially have nothing left of their knee to secure a knee implant. But the Finn Knee supports the new joint, and empowers patients to walk again.”

Surgeons at the Chicago Center for Orthopedics have implanted hundreds of the device over the past 25 years. “Our research proves this implant is reliable and durable over the long haul, with most patients experiencing significant functional improvements to their knee and leg in their daily life,” said Dr. Farid, who is also assistant professor of Clinical Orthopaedics at University of Illinois at Chicago.

The study reviewed 142 non-oncological cases involving the OSS implant over a 17-year period (1994-2011). The complete revision system originally was designed for patients at risk of losing their leg due to osteosarcoma, but the surgeons quickly realized that they could help an even greater number of people. This study focuses on patients without bone cancer, and notes a high infection rate (22 percent), due to the complex conditions end-stage revision patients have going into the procedure.

“This surgery should not be taken lightly,” Dr. Finn noted. “Surgeons have to plan carefully, especially when the reconstruction of soft tissue is involved. There are always risks, but this implant enables calculated risks.”

The study also reports nearly 80 percent of patients walk away from surgery with their knee functioning very well for a significant number of years.

INITIAL CANCER PATIENT FOCUS

Kathy Hnilica, 52, of Hoffman Estates, Ill., is one of the first patients to benefit from the rotating hinge-knee implant, a technology that’s still a part of her following surgery in 1990. She was faced with amputation after being diagnosed with osteosarcoma. Doctors discovered a cancerous tumor in her thighbone, which was touching her knee, at the age of 27.

“I was willing to do anything to save my leg,” said Ms. Hnilica. “I was too young to lose a limb.”

Her leg was saved with a rotating hinge-knee implant.

She remains active participating in biking, swimming, bowling and gardening.

She also enjoys traveling. In celebration of 25 years of saving her leg and still being able to walk, she booked a 3-week trip to Europe over the summer.

“I did a lot of walking on hilly, cobblestone streets,” Ms. Hnilica explained. “After all these years, I still walk well. I can’t imagine life without my leg. It’s been worth all I’ve had to go through to save it, and worth celebrating.”

Dr. Finn salvaged Ms. Hnilica’s diseased knee.

He said he designed this new rotating hinge-knee implant because of his dissatisfaction with the other salvage knee devices then available to patients. “Nobody wants amputation. Nobody wants their knee fused and walk with a peg leg. So I developed a better option for these complex cases to salvage the limb,” Dr. Finn added.  

GROWING CONCERN

More than 4.7 million Americans are living with an artificial knee, according to the AAOS.

An estimated 54,000 people face knee revision operations each year in the U.S. These initial implants are at even greater risk of failing fast due to a heavier and high-impact exercising aging population. Also, a growing number of younger patients getting joint replacements return to their intense exercise routine, which leads to quicker wear or damage to their artificial joint. This lifestyle often leads to a knee revision sooner in life.

Half of knee revision surgeries happen within five years of the original knee, mainly due to a loosening of the implant or infection.

An estimated 600,000 people undergo knee replacement operations every year. It’s one of the most common surgical procedures. By 2030, some 3.4 million Americans are expected to need knee replacements annually, which means more than 300,000 of them will likely need a knee revision within a few years of their operation.

An estimated 70,000 of those revision surgeries will be the result of an infected knee. With concern over resistance to antibiotics, and significant bone loss due to multiple knee surgeries, more people are expected to benefit from the limb saving, rotating hinge-knee implant.

“We expect there will be an increased need for the implant, and we are pleased that our research has shown it to be a reasonable alternative to amputation or knee fusion,” Dr. Farid added.

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