Session III: Total Knee Replacement in Young Patients

The earliest studies in the 1970s describing the use of total knee replacement for severe arthritis ^5–7 usually described an average patient age in the eighth decade. Life expectancy of the implant, and for the patient, of 5 years was considered excellent. During the ensuing years, however, advances in surgical sophistication and materials improvement were matched by a greater expected life expectancy for the implants and for the patients.

Almost all of these original knee replacements were done for patients with osteoarthritis of aging. With the rapid expansion of exercise as a method of health enhancement, there has been a concomitant increase in exercise-related knee injuries. Changes in lifestyle, muscle strengthening, antiinflammatory drugs, and arthroscopic surgery have allowed many of these patients to alleviate some of the symptoms. There has been, however, an increasing number of patients in the fifth decade and early sixth decade of life who have advanced degenerative changes in their knees caused by prior injuries to the anterior cruciate ligament, the menisci, or articular surface injuries whose symptoms persist and are severely impacting on their ability to participate in normal activities of daily living.

Doing a knee replacement in a patient in the fifth decade or sixth decade of life is different than doing a knee replacement for a patient in the eighth or ninth decade of life. Activities of daily living place higher stresses on the implants and their fixation to the underlying bones. In the current author’s institution, the mean body mass index for patients having knee replacement in this younger age group is 33.6, more than 6 points higher than that seen in the patients having knee replacement in the seventh or eight decades of life. This has led to a reexamination of implant design and technique for these patients.

Is the polyethylene that has been used for the past 25 years satisfactory for patients in this high demand group? Implants are no longer gamma-irradiated in air and left to oxidize on the shelf, but is this enough to ensure their efficacy in the long-term? Should the properties of the polyethylene be enhanced (if possible) by such methods as cross linking? Will such enhancement increase brittleness in a high contact stress environment such as the knee? Should cement be used in these young patients ^2,3 or should the arthroplasty be done cement-free ⁴ ?

Should the surgeon look for a nontraditional knee design for the younger patient with high physical demands? Is a mobile-conforming bearing surface the answer to polyethylene wear in these patients ¹ ? Should the surgeon temporize and resurface as little of the joint surface as possible concomitant with the patient’s disease, hopefully forestalling the eventual knee replacement until the patient is older? Should the surgeon search for alternate bearing surfaces, such as ceramic, to articulate against the polyethylene? ⁸

This session will examine these issues in light of extensive clinical experience.