Of the 62 surviving patients (98 TKAs), the average UCLA activity score was 8.3 points (range, 5-10 points; SD, 1.2 points). Surprisingly, 22 patients (35 TKAs) reported participation in impact activities such as jogging, volleyball, or singles tennis (Table 6). All patients reported active participation in at least some form of moderate activity (ie, Levels 5-10).
There are limitations to this study, however. First, as with any long-term study in older patients, we were able to identify only 128 of the original 1471 patients (8.7%) as living. However, we confirmed the other 1341 patients had died. Fifty patients were lost between the 2- and 20-year followup. It is possible some of these 50 patients would still be living and selection bias introduced into the study, thus, skewing the data. With longer periods of followup, patient attrition may tend to occur as patients relocate or prefer to avoid further followup. It is also possible the patients lost to followup may experience prosthetic failure or an inferior clinical result. Interestingly, Joshi et al.  in a review of 563 TKAs reported a lower rate of failure for revision surgery and higher satisfactory results in nonattenders compared with patients completing followup. They concluded patients who do not attend followup visits do not necessarily have poor results. Furthermore, these data are similar to those for actuarial data. According to the US National Center for Health Statistics , a 65-year-old individual between the years of 1979 and 1991 had a life expectancy of 16.5 to 17.3 years. Furthermore, a life expectancy of 20 years was noted for a 60-year-old individual (living between 1979 and 1991). The average age of those living beyond 20 years in our study was 64 years (± 9 years) at the time of operation. Thus, it appears this followup is at least consistent with the US life tables for the time period under question. Second, although the standard KS clinical and radiographic data were obtained prospectively and available in all 128 patients at the minimum 20-year followup, the UCLA activity scores were obtained retrospectively. As noted above, before 1989, patients were evaluated using the HSS Rating System . This score was then converted to the KS scoring system. Thus, these data on all 128 patients were collected preoperatively, postoperatively, and prospectively. We compared KS knee, function, and activity scores over time, but we were unable to compare the UCLA activity scores over time. Ritter et al.  reported, although knee and pain scores do not decline over time after TKA, function scores do decline an average of 0.88 points per year due to decreases in stair and walking scores and the need for support using cane, crutches, or walkers. Similarly, other authors have demonstrated long-term deterioration in joint evaluation scores due to an increasing prevalence of medical comorbid conditions and progression of arthritis at sites other than the joint arthroplasty [3, 15, 17, 29]. Third, only 62 (48%) of the 128 patients still living beyond the 20-year followup were queried for a UCLA activity level. These specific data are not part of our prospective database and, therefore, were unavailable for the 66 deceased patients (73 TKAs from the original cohort). Thus, while we were able to determine the general functional activity of this patient population over time (KS function, stair, and walking scores), we also wanted to determine a more specific activity level of the patients (UCLA score). Fourth, we recognize activity-rating scales, including the UCLA scale, do not evaluate all aspects of patient activity. While the UCLA score may be sensitive to patient exaggeration, we chose the UCLA because it is a reliable and valid instrument for assessment of activity levels in patients undergoing total joint arthroplasty . This scale correlates closely with pedometer studies , investigator VAS , and patient’s VAS . It has been strongly correlated with the WOMAC (pain, stiffness, function), International Physical Activity Questionnaire, Oxford knee score, KS knee score, KS function score, SF-12 physical component, and SF-12 mental component score . Fifth, our study group may be skewed to a higher activity level because of the relatively low number of patients categorized as Charnley Class C . Indeed, 92% of the study group (157 of the 171 TKAs) was categorized as Charnley Class A (unilateral disease or bilateral disease with the opposite knee successfully replaced) . Benjamin et al.  noted a decline in functional knee scores over time related to an increase in percentage of patients in Class C. Schmalzried et al.  demonstrated with pedometer testing patients in Charnley Class A were more active than those in Class B or C. We recognize our study group may be skewed to a highly selected group of healthy and active patients who lived 20 years after a successful TKA. Sixth, the functional results and activity scores in this study presume the successful survival of the TKA and the absence of any implant-related problems. While we are reporting 20-year survivorship of the PCC TKA, the ACG TKA reportedly has a 20-year survivorship of 97.8% . Similar survivorship may not necessarily apply to other knee arthroplasty systems unless device complications are minimized or eliminated. Finally, there is no control group of patients without osteoarthritis or prior TKA for comparison. To the author’s knowledge, there are no published data on the UCLA activity scores in otherwise healthy octogenarians without osteoarthritis.
There is no other long-term study reporting on the UCLA activity score after TKA. However, Dahm et al.  reported on 1630 TKAs (1206 patients) followed for an average of 5.7 years and noted an average UCLA activity score of 7.1 at an average age of 70 at final followup. Bauman et al.  studied 185 TKA patients with a mean age of 69 years at an average followup of 1 year and noted an average UCLA activity score of 6 points. Fisher et al.  noted an average UCLA activity score of 6.5 at an average of 18 months after unicompartmental knee arthroplasty in 71 patients (71 knees). Their average age at operation was 64 years .
The limits of the scoring systems used in this study are evident due to several apparent discrepancies between the KS function scores and the UCLA activity scores. Three patients (three TKAs) reported walking was limited to housebound ambulation only. Yet, the UCLA level of activity in these two patients was rated as Level 5 (moderate activity such as shopping). Furthermore, two patients (two TKAs) stated they were unable to negotiate stairs at all. Similarly, UCLA scores were rated as Level 5 in one of these individuals. Not all patients assigned a function score at last followup were alive to have a designated UCLA activity score. Another reason for this apparent discrepancy may be related to the scores being reported not necessarily at the exact same time.
Although aging may cause a gradual decline in physical activity after TKA, improved functional outcomes continue over the long term. Postoperative KS knee, function, pain, stair, and walking scores remained higher than the preoperative values throughout the entire followup. Our observations suggest this group of patients demonstrates remarkable functional capacity over 20 years after the index knee arthroplasty. This long-term functionality demands high implant survivorship and the absence of implant-related complications over time.
We thank Philip M. Faris, MD, who along with Merrill A Ritter, MD, and E. Michael Keating, MD, were orthopaedic surgeons for the patient population included in this study.
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