The New Era in Knee Replacement Surgery Increases Mobility and Reduces Costs, Thanks to Use of Unicompartmental Knee Arthroplasty Through a Small Incision

A new approach to knee replacement surgery using a specially-designed prosthesis and instrumentation that enables access to the knee through a small incision, dramatically reduces time in the hospital, pain and expenses, while increasing the immediate and long-term mobility of patients who receive the procedure compared with traditional knee replacement surgery.

The surgical instrumentation that permits minimally invasive unicompartmental knee replacement, introduced to the United States in April by orthopedic surgeon Dr. Mitchell Sheinkop at Rush-Presbyterian-St. Luke's Medical Center, Chicago, reduces the size of the incision required to place the knee prosthesis from about 18 inches in conventional knee replacement surgery to about three inches.

"The smaller incision speeds the patients' time to reach maximum medical improvement, and more importantly it offers patients greater function than a total knee replacement. It also cuts down time in the length of stay in the hospital, time in the operating room, the need for physical therapy and reduces the chances of complications," Sheinkop noted.

The use of precision instrumentation assures the reproducibility of the cut of the bone and the orientation of the prosthesis implant through the small incision. As a result, long-term outcome and survivorship of the prostheses are greatly improved, according to Sheinkop.

"This is important as the baby boomer population is growing older, living longer and wanting to keep vigorously active as they move through their 50s, 60s and 70s," said Sheinkop. "Patients who receive the 'uni' knee replacement through the small incision can play doubles tennis, ride a bicycle, bowl, dance and in most cases ski."

Knee replacement surgery is often recommended for individuals generally over 55 years of age with arthritis that is too advanced to benefit from other treatment options including medications, cellular and cartilage transfers, arthroscopy or less complex procedures involving surgery to realign the knee. They suffer from pain that limits routine as well as athletic function and performance.

"Patients are able to leave the hospital within 24 hours compared with a hospital stay of four days that is the average for a partial knee replacement through traditional approach, and compared with 5 days for a full knee replacement," said Sheinkop.

Of those individuals who require knee replacement surgery, about 30 to 40 percent have arthritis that affects only one part of the knee and can benefit from a unicompartmental knee replacement. Many of these individuals have degenerative (osteoarthritis) or post traumatic arthritis as a result of a previous fracture or injury. The unicompartmental knee replacement is not for individuals with rheumatoid arthritis.

Extensive research and clinical work on unicompartmental knee surgery had been done at Rush since the early 1980s when the procedure was learned from European orthopedic surgeons.

As a result of their experience in refining and developing implant materials used over years, Rush orthopedic surgeons have enjoyed a high success rate in reducing pain and restoring function to the knee following conventional unicompartmental knee replacement and a long survivorship of the prosthesis.

Sheinkop developed the minimally invasive instrumentation approach to unicompartmental knee surgery because of his interest in retaining a higher level of athletic activity than what is common for people in their 50s and 60s. He borrowed from the techniques developed by orthopedic sports medicine colleagues using arthroscopy to do knee repair through small puncture wounds, and worked with the Zimmer, Inc., of Warsaw, Ind., to manufacture the prosthesis and precision instrumentation that enables success working through the small incision.

The new instrumentation includes nine pieces of equipment including a cutting guide device that is inserted into the knee through a small holes to guide the angles of the cuts of the bone so that there is a perfect alignment for the placement of the prosthesis with the existing bone. The knee prosthesis includes a polyethylene surface that replaces the cartilage, which is attached to metal that replaces the bone. The metal bone replacement glides along the polyethylene surface in the same manner that the bone had moved along the surface of the cartilage.