A1219. TKA: CHANGING PATIENTS AND DEMOGRAPHICS: IMPLICATIONS FOR FUTURE IMPLANT NEEDS

Abstract

It has become a platitude that total knee arthroplasty (TKA) is an excellent operation, provides good pain relief, and over 90% survivorship at 20 years in many series. While all these points are true, total knee arthroplasty as practiced currently still will not meet the demands of many patients who will desire the procedure in the next ten years. The reasons for this include changing demographics of TKA and the changing demands of TKA candidates. TKA is being performed more frequently in patients under 60, in fact this is the fastest growing group of patients by percent growth. We performed a population-based study of trends utilization of TKA and found increasing TKA utilization in all age groups over time but the greatest increase by percent in the youngest patients. Furthermore, younger patients now no longer tend to be lowactivity patients with inflammatory disease. The percentage of patients with primary osteoarthritis and post traumatic arthritis has increased dramatically. Long-term studies of TKA have shown such durability in part because many of the younger patients were Charnley Class C patients, and because historically most TKA patients were older with an average age of most early series of around 69 years. This means there were far fewer young patients in early TKA series than in early THA series. This is important because material failures occur predominantly in younger patients and durability is a greater concern in younger patients, so one may predict that this younger, more active group will not enjoy the same level of TKA durability reported in the literature unless technology improves.

Total knee arthroplasty patients are more active than one might predict. In a study of 1200 patients surveyed at five years the average UCLA score was 7 out of 10. Younger patients achieved a higher activity level but were in general less satisfied with activity provided by TKA than older patients. This implies there is a need for better designs and surgery to facilitate more normal kinematics, more flexion, and more quadriceps strength. A study by Weiss and Noble (CORR 2002) identified specific activities associated with limitations after knee arthroplasty.

Furthermore, a study by Bourne and associates demonstrated lower satisfaction scores after total knee arthroplasty than hip arthroplasty. Finally, in our study of activity levels after knee arthroplasty we found that 16% of current patients participate in heavy labor or sports not recommended by Knee Society guidelines. These patients tend to be younger and predominantly male. This implies there is a subset of the population already doing things that will challenge the current generation of total knee arthroplasty and more patients want to do these activities and already do so. Therefore, there is a need for improved implant durability and improved knee function after knee arthroplasty. This suggests the methods of fixation may need to evolve to accommodate higher demands, and bearing surfaces definitely need to evolve to accommodate higher demands. Finally, more sophisticated implant kinematics to avoid or compensate for anterior cruciate ligament and posterior collateral ligament deficiency and more sophisticated surgery to optimize implant alignment and soft tissue balancing in the individual patient will be necessary to achieve more normal patient knee kinematic stability, strength and “feel”. Finally, we will need better and more sensitive scoring systems to detect improvements in future TKA surgery and design in the future.