Inventing the Modern Total Knee Replacement

Adapted from the Spring 2013 issue of Discovery to Recovery


Total knee replacement is one of the most popular orthopedic surgical procedures in the world and the only cure for advanced knee arthritis. This life-changing surgery is an important part of HSS’s history, current practice, and vision for the future.

A Game Changer: Discovering the Modern Total Knee

In 1969, when John N. Insall, MD, became the chief of the HSS Knee Clinic, there was no reliable knee implant on the market. When patients had debilitating knee arthritis, their best option was often the temporary relief of pain medication. Seeking new hope for their patients, Dr. Insall worked with HSS surgeons Chitranjan Ranawat, MD, Allan E. Inglis, MD, and biomechanical engineer Peter Walker, PhD, to design and develop the modern total knee implant, called the total condylar knee. Dr. Insall and Dr. Ranawat first used the total condylar knee with patients in 1974.

For the first time, a knee implant recreated the way a real knee works, allowing patients to move naturally and without pain. “This knee was a game changer,” says Chief Scientific Officer Steven R. Goldring, MD, Richard L. Menschel Research Chair.

“The total condylar knee gave patients with advanced knee arthritis a chance to live without pain.” The total condylar was the first implant to address all aspects of the knee with anatomically shaped parts. Previous implants were cumbersome for surgeons to implant. Surgeons across the country appreciated the total condylar’s design and began to use it with their patients.

Today’s Patient Centered Research

Since 1974, HSS physicians, scientists, and engineers have continued to advance knee prostheses, dramatically increasing implant longevity and developing better implant materials. They now track long-term patient outcomes through a joint replacement registry that enrolls more than 30,000 participants and analyze retrieved implants at the Mary and Fred Trump Institute for Implant Analysis, in order to understand how the implants have performed and improve that performance.

Today, our research team is turning its attention to other areas of research, including developing new materials that address soft tissues and improving patients’ results throughout the pathway of care, from presurgery through rehabilitation, to improve overall outcomes.

“The partnership between surgeons and engineers that resulted in the invention of the modern knee replacement continues to drive innovation at HSS,” says Surgeon-in-Chief Thomas P. Sculco, MD. “We perform more than 9,000 hip, knee and other joint replacements each year – more than any other hospital in the world. Our team is devoted to identifying areas where we can achieve even higher standards across the pathway of care.”

When Two Knees Are Needed

Patients often require the replacement of both knees. For years, surgeons have debated which of the three surgical options is safest for patients:

  • both surgeries at the same time (called simultaneous or single stage bilateral),
  • separate surgeries staged a few days apart during the same hospitalization, or
  • separate surgeries separated by a few months.

HSS anesthesiologist and intensivist Stavros G. Memtsoudis, MD, PhD, has studied risk factors for bilateral knee replacement surgery. He and his colleagues, including Surgeon-in-Chief Thomas P. Sculco, MD, published a 2009 study that found that the risk of complication in bilateral procedures increases when patients have certain risk factors, including pulmonary hypertension, increased age, renal disease, and history of heart disease. They also found that staging two knee replacements several days apart during the same hospitalization increases the risk of adverse events.

Based on this research, HSS changed its guidelines to determine which patients are good candidates for bilateral surgery. “Bilateral knee replacement is a safe and effective procedure, but patients must be selected carefully,” says Dr. Sculco.

Nationwide, surgeons have been offering younger patients’ bilateral knee replacement as concern for risk factors has grown. In a study published in 2012, Dr. Memtsoudis and colleagues analyzed a large national database of patients who had bilateral knee replacements between 1999 and 2008 to determine if outcomes changed over time. He found that while patients were younger in 2008, complications did not decline. This finding was surprising but explainable by the fact that patients were actually sicker in 2008 than they were a decade earlier, with higher rates of comorbidities. For example, obesity increased by 131 percent during the study period.

Dr. Memtsoudis sees this study as a wake-up call. “Before this study, we expected that patient complications were steadily decreasing after bilateral knee replacement because of an increased understanding of risk factors and improved medical care,” he says. “Now we understand that the picture is more complex. We need to work on continuously improving management of patients with a variety of health issues.”

Preparing Patients for Recovery

At HSS, an interdisciplinary team of clinicians, researchers, and administrators works to fine-tune the “pathway of care” for knee replacement, from preoperative screening through rehabilitation. People who are healthy and prepared prior to surgery are more likely to succeed in rehabilitation following surgery and have better overall results.

Linda Russell, MD, a rheumatologist and director of the Perioperative Medicine Division, and orthopedic surgeon Charles Cornell, MD, have initiated a study of 100 knee replacement patients who have been identified as good candidates for a new program that includes increased health monitoring prior to surgery and an innovative step of a presurgical home visit by a physical therapist. The study will determine if this pre-care will increase the chances of patients successfully returning home with appropriate home-based and outpatient rehabilitation following surgery, as opposed to going to an inpatient rehabilitation facility.

“For many patients, going home and resuming normal life activities is their best option. The study will determine if receiving more support prior to surgery will result in a smooth transition home,” says Dr. Russell.

Read the full Discovery to Recovery Spring 2013 issue.

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