Knee replacement in young patients

Dr.A.K.Venkatachalam

Consultant orthopedic surgeon

Chennai

Unheard of until recently, this is now becoming a hot subject of deliberation amongst patients and orthopedic surgeons. Normally the typical patient for a knee replacement would be a patient in their golden years of life. Surprisingly now increasingly large number of young patients, plagued by end stage arthritis from various causes, are now seeking an end to their constant pain and stiffness by demanding a total knee replacement. The number of patients less than 65 years old seeking a knee replacement is increasing. According to a national sample survey in the US done in 2005, about 9660 patients less than 45 years underwent a primary total knee replacement. This figure is expected to touch 108000 by 2030. To quote some figures, 27 percent of TKR recipients are between 18 and 64 years. This is setting a new trend in orthopedic surgery.

At present Knee replacement is advised for elderly patients. Whenever orthopedic surgeons come across younger patients less than 65 years, they generally advise exhaustion of conservative measures before proceeding to a total knee replacement. As the above figures show, more and more younger patients are likely to demand a total knee replacement in years to come.

Younger patients live a more active life style and joint replacement is likely to result in early failure if standard approaches are adopted.

The purpose of this article is to inform readers particularly the younger ones about some of the advances in Joint replacement for the young patient with knee arthritis.

Conditions

The conditions leading to end stage arthritis in the young are rheumatoid arthritis, post traumatic arthritis, ankylosing spondylitis, post infective arthritis hemophilic arthritis and osteoarthritis in the genetically predisposed young patient.

Survivorship of standard knee replacements

Conventional knee prostheses are made of an alloy of Cobalt, Chromium, Molybdenum & Nickel and Titanium. The plastic component is high density poly ethylene. The survivorship is such that 1 % of every 100 knees fail every year, so that after 15 years, 85 % of knees implanted on day one are expected to survive or remain intact without loosening. This excludes loosening due to faulty insertion and infection. So in the elderly patient, a reasonable outcome is expected with the prosthesis expected to outlive the person.

In the young however the situation is different. Historically, total knee replacements are known to have poor outcomes in the young due to their higher activity levels compared to older patients. Hence surgeons are reluctant to place them in younger patients as they are bound to outlive their implants.

Better materials

With the advent of newer materials and designs of knee prostheses, these perceptions are about to change. The biggest advance is the availability of newer materials like Ceramic for knee replacements. Pure ceramic or ceramic coatings on metal are the latest in technology.

Titanium carbide has been used for dental implants but its use as a bearing surface in hip & knee prostheses is not widespread. Knees made of ceramic are in restricted use. Implantation of pure ceramic knees requires specialized instrumentation.

OxiniumorOxidised Zirconiumis the wonder material that has been used successfully for knee & hip implants. It is a metal with a coating of ceramic. In the manufacturing process, prosthetic components made of Zirconium are heated and infused with oxygen to create a ceramic surface on metal. This ceramic surface is more durable than normal metals. This material received FDA approval in 1996. After rigorous testing, this material received approval for use in knees.

Advantages of Zirconium knees

The significant advantage of a Zirconium knee implant is that it is considerably harder. On testing it lasts 85 times longer in tests that simulate the stresses inside the actual knee.
Additional advantages are scratch resistance. When it is wet, ceramic can glide smoothly along plastic, making for smoother motion than with metal-on-plastic. As a result, the Oxinium total knee replacement will not generate the quantity of plastic wear debris that cobalt chrome will, and the implants should last considerably longer.
Zirconium is one of the six most biocompatible elements know to man. So, your immune system will more easily tolerate your new implant.
Lastly, patients who are allergic to nickel, the metal most often used in the current implants, cannot currently receive total knee replacements. The ceramic implant, however, can be implanted safely in patients with nickel allergies, since it uses a zirconium alloy with no nickel. Implants made of Oxinium have been implanted in larger number of patients in the UK Australia and the US with great success.

Who would benefit most from an Oxinium total knee replacement?
Threetypes of patient have been identified as the "best" candidates for an Oxinium total knee replacement.

"Younger"patients: Because Oxinium knee implants offer significantly less wear compared to cobalt chrome implants, they are expected to last considerably longer. In the past, orthopedic surgeons have advised patients less than 65 years of age to wait to have knee replacement surgery because the life span of the cobalt chrome knee implants is only 10-15 years. Now, surgeons have a viable option for a younger patient who previously would not be a candidate for a total knee replacement because the Oxinium knee implants should last much longer. Therefore, a patient under the age of 65 who has advanced arthritis of the knee no longer has to suffer for years until he reaches an appropriate age for total knee replacement surgery.

"Active"patients: Patients, who desire to return to an active lifestyle, including sports, dancing, gardening, or other strenuous activities, may also benefit from an Oxinium knee replacement. As a result of their high activity level, this patient population will put more "wear and tear" on their knee replacement, which can cause the implants to wear more quickly. An Oxinium knee is better able to tolerate this high activity level and last longer that the traditional cobalt chrome knee.

Metal allergypatients: Because Oxinium is one of the most biocompatible materials known to man; It is the only choice for patients who exhibit metal allergies. Patients who have needed total knee replacement surgery, but could not tolerate the cobalt chrome implants due to their nickel content, can now have the surgery they need to return to an active lifestyle without the fear of an allergic reaction.
Three designs are available, the Genesis knee, Journey knee and the Deuce knee, according to the manufacturer, Smith & Nephew.
In India, the Genesis knee in Oxinium is to be introduced soon in South India.