What's new in joint replacement?
Dr. Fisher provides the latest news in joint replacement.
Minimally Invasive Surgical Approaches For Hip Replacement
Surgeons have been trying to perform total knee replacement through smaller incisions since 2001. Surgical tools and techniques have been developed to allow this complicated surgery to now be performed in this manner. However, we have learned that smaller incisions also limit visibility and potentially can decrease our accuracy and increase the complications of the procedure.
Ceramic bearings were approved for use in the US by the FDA in 2003. These types of implants have been used outside the United States for over 20 years. While the early designs were subject to wear, breakage and failure, newer ceramic bearings have much better wear resistance with a very small incidence of breakage.
Surface Replacement (Hip)
Surface replacement is a type of hip replacement where the socket is replaced much like a total hip, but the femoral head (ball of the hip joint) is machined to accept a metal cap that sits on the ball. The reported advantages of this technology are less femoral bone loss and an easier revision on the femoral side if that became necessary.
Metal on Metal
Metal on metal bearings are composed of a metal hip liner and metal femoral ball. I no longer use this type of bearing. All metal cups have caused problems that required revision in some patients and many of those have been discontinued.
Total hip replacement is a fantastic operation for those who suffer from hip arthritis. It can relieve pain and restore function better than any other operation. It is also incredibly durable, with over 95% of the hips I implanted 10 years ago still functioning well. However, these implants can fail and require a secondary surgery to repair them. The most common cause of failure is wear of the artificial bearing.
The “Gender Knee” is a marketing term used by Zimmer Orthopedics to describe their latest knee system, theoretically designed for women. The implication is that woman’s knee anatomy is different from men.
Unicompartmental (or partial) knee replacement is an operation that has been around for over 40 years. First popularized in the 1970’s, these operations were used commonly before total knee replacement became popular. Some surgeons, however, have continued to use unicompartmental implants for certain patients in their practices.
Mobile Bearing Knees
Mobile bearing knees were designed to reduce the wear of the polyethylene tibial bearing in total knee replacement. As with fixed bearing knees, they have been around for over 30 years with very good clinical results. The difference between a mobile bearing and a fixed bearing device is that in the fixed bearing, the polyethylene is rigidly fixed to the tibia and all prosthetic motion occurs between the femoral implant and the polyethylene bearing.
A small percentage of patients may have an allergy to certain metals. This is usually a nickel sensitivity that makes wearing jewelry containing nickel troublesome due to the skin rash it can create. The Chrome Cobalt implants have a trace amount of Nickel in them in addition to the chromium and cobalt metals. This type of sensitivity can rarely cause an allergic type of reaction to the prosthetic implant. While it is estimated that 10% of the population has some metal sensitivity, implant related reactions are estimated to be 1 in several thousand patients and have been more commonly observed after knee replacements.
Pain Management and Rapid Rehabilitation
Total hip and knee replacement are truly miracles of modern medicine. The pain relief and improvement in function are amazing. However, the surgery is a painful and unpleasant procedure for patients to undergo. Much work has been done since 2001 to improve the patient experience by reducing the pain they experience and speeding up their recovery process. This has led to new anesthesia and pain management protocols that significantly reduce the pain experience for the patient. Patients start their rehabilitation within hours of their surgery and are allowed to walk, sit in a chair, and do therapy exercises immediately.