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Does Total Knee Arthroplasty Affect Physical Activity Levels? Data from the Osteoarthritis Initiative
The Journal of Arthroplasty 30 (2015) 1521–1525
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Does Total Knee Arthroplasty Affect Physical Activity Levels? Data from the Osteoarthritis Initiative Timothy L. Kahn, BA, Ran Schwarzkopf, MD, MSc Deparment of Orthopaedic Surgery, University of California Irvine Medical Center, Orange, California
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Article history: Received 6 January 2015 Accepted 18 March 2015 Keywords: total knee arthroplasty accelerometer accelerometry physical activity patient-reported outcome measures physical activity guidelines
a b s t r a c t Total knee arthroplasty (TKA) is associated with improved patient-reported pain levels, function, and quality of life; however, it is poorly understood whether there is increased physical activity following TKA. Using data from the Osteoarthritis Initiative (OAI), we compare physical activity, as measured using an accelerometer, and patient-reported outcome measures of 60 patients who had already received a TKA with 63 patients who eventually received a TKA during the OAI study. There was no significant difference in activity levels between the two groups as measured by the accelerometer. Total WOMAC, KOOS Quality of Life, KOOS Knee Pain, and KOOS Function scores improved in the post-TKA compared to the pre-TKA group. In both pre-TKA and post-TKA groups, physical activity guidelines were met in only 5% or less. © 2015 Elsevier Inc. All rights reserved.
Total knee arthroplasty (TKA) is well established as the definitive treatment for end-stage knee osteoarthritis (OA) [1–4]. It is associated with improved patient-reported pain levels, increased function, and improved health-related quality of life [5,6]. From a financial perspective, TKA is also one of the most cost-effective procedures considering quality-of-life years gained per amount spent [5,7–12]. However, objective measures of physical activity following TKA are a relatively new area of research which is still poorly understood. Recent research has demonstrated that physical activity, as measured by accelerometry data, may not actually increase following TKA [13], although conflicting results have been reported in the literature [14–16]. Measuring physical activity following TKA is important both as an outcome measure [17] and a public health matter [18,19]. Many patients have high expectations regarding the amount of physical activity they will be able to achieve following TKA [20] and may become frustrated with their outcome if these expectations are not met or addressed. As a recent study by Harding et al demonstrated, very few patients, by 6 months following TKA, achieve activity levels recommended by the American Physical Activity Guidelines [13]. Consequently, inability to increase physical activity also places patients at increased risk of many disease processes, including cardiovascular disease, stroke, and overall mortality [21,22]. One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.03.016. Reprint requests: Ran Schwarzkopf, MD, MSc, Department of Orthopaedic Surgery, University of California Irvine Medical Center, 101 The City Drive South, Building 29, Pavilion III, Orange, CA 92868. http://dx.doi.org/10.1016/j.arth.2015.03.016 0883-5403/© 2015 Elsevier Inc. All rights reserved.
Accelerometry has become an important means of objectively measuring patients’ physical activity, as it is considered the most accurate means of doing so [23–25]. In contrast to a simple pedometer, accelerometers measure vertical acceleration of the subject, yielding data pertaining to duration, frequency, and intensity of exercise [25–27]. Consequently, accelerometry data provide important information regarding patient exercise which can be interpreted in metabolic equivalent task (MET) units. The utilization of accelerometry data is especially important considering the poor reliability of patient-reported physical activity [13,15,28]. For example, recent research on the physical activity for the elderly (PASE) questionnaire demonstrated several validity and reproducibility shortcomings, especially in women [28]. The primary objective of this study is to evaluate and compare the levels of physical activity using accelerometry data in two groups of patients: those who eventually receive TKA and those who have already received TKA. Secondary objectives include comparing patient-reported outcome measures including: pain, function, and health-related quality of life between these two groups of patients. Our hypothesis is that while patient-reported measures will be different between these groups, and improved in the post-TKA group compared to the preTKA group, there will be no difference in physical activity as measured by the accelerometer. Methods All data were obtained from the Osteoarthritis Initiative (OAI) database. The OAI is a publicly and privately funded prospective longitudinal observational study that studies the natural progression of osteoarthritis in patients [29]. The 4796 patients included in the OAI study were divided into subcohorts at the beginning of the study, which included
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a progression subcohort of 1389 patients who had clinically significant osteoarthritis at baseline, an incidence subcohort of 3285 patients who were determined to be at high-risk of developing clinically significant osteoarthritis, and a control cohort consisting of 122 patients with no symptoms or risk factors for osteoarthritis. All 4796 patients included in the study were required to attend a baseline visit followed by annual visits to their respective study center, where clinical, radiographic, and biomarker data were collected at each visit. The OAI study is also a multi-center study that is conducted at four different centers: (1) the Ohio State University, (2) the University of Maryland School of Medicine, (3) the University of Pittsburgh, and (4) Memorial Hospital of Rhode Island in Pawtucket, Rhode Island. All data, including radiographic images and biomarkers, are publically available at http://www.oai.ucsf.edu. At the 48 month visit of the OAI study, a subset of 2712 OAI participants were invited to join a physical activity ancillary study where participants would wear an ActiGraph GT1M uniaxial accelerometer (ActiGraph; Pensacola, Florida). Of these 2712 OAI participants, 2127 patients consented to participate. All patients were instructed on how to wear and use the accelerometer by trained OAI research staff. Patients were to wear the accelerometer from arising in the morning to retiring at night, except during water activities, for seven consecutive days. Patients were also instructed to maintain a daily log recording time spent in the water and cycling activities (both of which are not recorded accurately with the accelerometer). Upon return of the accelerometers to their respective study centers, data were analyzed to measure valid days of recording, which was defined as greater than or equal to 10 hours of recorded wear-time; 2001 patients provided one or more valid days of recording and 1927 patients provided four to seven valid days of recording. In our study, we studied two sets of patients taken from the accelerometry OAI study: “pre-TKA patients” and “post-TKA patients.” There was no overlap of patients between these two groups; as accelerometry data were only collected during the 48-month visit of the OAI study, these patient groups represent those who had TKA before accelerometry data collection (post-TKA patients) and those who had TKA after accelerometry data collection (pre-TKA patients). The preTKA patients included those who had not had a total knee arthroplasty prior to the 48 month visit where accelerometry data were collected, though did have an adjudicated TKA at an OAI visit any time after the 48 month visit where accelerometer data were collected (the OAI study currently has data up to an 84 month visit). Patients were included if they had an adjudicated TKA at any point following the accelerometry data collection and had 4 to 7 days of valid accelerometry recording — this inclusion criteria were based on previous studies which demonstrated that at least 3 to 5 days of wear-time is necessary to accurately predict overall physical activity for the patient [26]. The post-TKA patients included those who did have a TKA during the OAI study prior to the 48 month visit where accelerometry data were collected. Patients were included in this second group if they had an adjudicated TKA prior to accelerometry data collection and had 4 to 7 days of valid recording. Only patients with total knee arthroplasty were included in our study; those with partial knee arthroplasties were excluded. Accelerometry data for both patient sets were analyzed using cutpoints, which divide activity counts (units of accelerometry data that integrate vertical acceleration and deceleration) per minute into different physical activity intensity levels. Previously established cut-points in the literature have been designed to estimate the intensity of physical activity in terms of energy expenditure measured in MET units, with light activity corresponding to 1.5 to b3 METs, moderate activity to 3 to 6 METs, and vigorous activity to ≥6 METs [30–32]. In our study, we utilized “cut-points” published by Troiano et al, which were applied to the general adult population from the National Health and Nutrition Examination Study [30]. The final data for each patient are reported as minutes of activity above light, moderate, or vigorous activity threshold cut-points.
To better evaluate each patient’s physical activity, we also compared each patient’s accelerometry data to the 2008 Physical Activity Guidelines for Americans set forth by the United States Department of Health and Human Services (DHHS). The DHHS guidelines recommend 150 moderate intensity bout minutes (minutes are accumulated in 10 minute bouts) along with 75 vigorous bout minutes spread out across the week. We also compared accelerometry data to the 2008 DHHS guidelines of adults with arthritis, which recommends 150 moderate-to-vigorous bout minutes spread out across the week. As coexisting comorbidities could serve as confounding factors in this study, the Charlson Comorbidity Index was used to assess the level of comorbidity in each patient. The Charlson Comorbidity Index is a method of assessing and categorizing the amount of comorbidities in a given patient [33]. Contributing factors to the index are conditions such as heart failure, COPD, strokes, or diabetes. Patients from both the pre-TKA and post-TKA groups were stratified using this index into groups with either no comorbidities or at least 1 comorbidity. A similar stratification was performed for symptoms of hip pain. Patients were separated into two groups based on the presence or absence of any hip pain for more than half the days in a given month within the year previous to accelerometry data collection. For each of these stratifications, accelerometry data were compared across pre-TKA and postTKA groups. For each patient included in the study, self-reported outcome measures of knee function, knee pain, and overall quality of life were gathered from the 48-month visit (the same visit where the accelerometer data were collected on). Self-reported outcome measures included Western Ontario and McMaster osteoarthritis index (WOMAC) scores, Knee Injury and Osteoarthritis Outcome Score (KOOS), and Global Assessment score. As the WOMAC score, as well as some of the KOOS subsets, focuses on only one knee, such unilateral scores were combined by summing the scores from each knee together. The combined score was utilized as to have greater correspondence with physical activity and ambulation, which were pertinent to this study. The Global Assessment score asks the patient on a scale of 0 to 10, “Considering all ways knee pain and arthritis affect you, how are you doing today?”. Patient-reported physical activity was also measured using the PASE questionnaire, which was filled out by patients during the 48 month visit. The accelerometry data of pre-TKA patients and post-TKA patients were compared using SPSS Statistics (Version 22; SPSS Inc., Chicago, Illinois). Patients’ accelerometry data as well as self-reported function/ pain scores were compared using an independent samples T-test with Levene’s test to assess for equal variances among patient data. The percentage of patients achieving DHHS guidelines for physical activity were compared between pre-TKA and post-TKA groups using a Pearson’s chi-squared test. Results Based on our inclusion and exclusion criteria, there were 63 patients included in the pre-TKA group and 60 patients in the post-TKA group. Baseline characteristics of each of these groups can be seen in Table 1. The mean age of patients in pre-TKA and post-TKA groups was 68.4 (SD: 8.2) and 67.3 (SD: 8.7), respectively. The mean BMI in pre-TKA and post-TKA groups was 29.2 (SD: 4.8) and 31.1 (SD: 5.3), respectively. For the pre-TKA group, 34.9% of patients had at least 1 medical comorbidity, while in the post-TKA group, 48.3% of patients had at least 1 comorbidity (P = 0.123). In the pre-TKA group, 27.0% had hip pain for the majority of the days in a month within the previous year compared to 25.0% in the post-TKA group. All baseline characteristics of both study groups can be found in Table 1. For the pre-TKA patients, there was an average of 552.6 days (SD: 358.9) between the time of accelerometry data collection and TKA. For the post-TKA patients, there was an average of 624.8 days (SD: 420.6) between TKA and accelerometry data collection.
T.L. Kahn, R. Schwarzkopf / The Journal of Arthroplasty 30 (2015) 1521–1525 Table 1 Baseline Characteristics of Patients.
Age Gender (% male) Race (% of study population): White Black or African American Asian Non-white (other) Current Employment Status BMI Time before or after TKA (days)
Average Comorbidity Index Score (CIS) Patients with CIS ≥ 1 (%) Patients with Heart Failure (%) Patients with History of Stroke (%) Patients with COPD (%) Patients with Hip Pain (%)
Pre-TKA Patients (N = 63)
Post-TKA Patients (N = 60)
68.4 (8.2) 50.8%
67.3 (8.7) 50.0%
84.1% 12.7% 1.6% 1.6% 41.3% employed 29.2 (4.8) 552.6 (SD: 358.9; range: 7–1135) 0.67 34.9% 4.8% 4.8% 3.2% 27.0%
86.7% 11.7% 0.0% 1.7% 41.0% employed 31.1 (5.3) 624.8 (SD: 420.6; range: 65–1444) 0.73 48.3% 0.0% 11.7% 8.3% 25.0%
⁎ Includes COPD, emphysema, or chronic bronchitis. ⁎⁎ “Hip Pain” defined as any pain in hip for more than half the days of 1 month during the past 12 months.
Concerning the accelerometry data, there was no significant difference (P = 0.57) in the average daily activity count between preTKA patients (186,878.7 counts/day) and post-TKA patients (197,376.8 counts/day). Likewise, there was no significant difference between pre-TKA and post-TKA patients in daily minutes of either light (268.10 minutes vs. 283.93 minutes, respectively), moderate (13.21 minutes vs. 12.09 minutes), moderate-to-vigorous (13.28 minutes vs. 12.41 minutes), or vigorous activity (0.07 minutes vs. 0.33 minutes) (Table 2). Only 3 patients (4.8%) from the pre-TKA group and 3 patients (5.0%) from the post-TKA group met current DHHS activity guidelines for the general population based on accelerometry data. There was no difference in results when using the DHHS guidelines for patients with arthritis (Table 2). When stratified into groups with either no comorbidities or 1 or more comorbidities, there was no significant difference between preTKA and post-TKA patients in total activity count or daily minutes of either light, moderate, or vigorous activity (Table 3). Likewise, when patients were stratified into groups with either the presence or absence of hip pain for the majority of a month within the past year, there was no significant difference between pre-TKA and post-TKA patients in total activity count or daily minutes of light, moderate, or vigorous activity (Table 3). Regarding self-reported symptoms/function in the two patient groups, there was significantly lower combined WOMAC pain scores (P = 0.018), combined WOMAC disability scores (P = 0.001), and combined WOMAC total scores (P = 0.002) in the post-TKA group when compared to the pre-TKA group (Table 4). Higher WOMAC scores indicate greater severity of symptoms. Likewise, combined KOOS Knee
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Pain Score and combined KOOS Knee Symptoms Score were higher in post-TKA patients when compared to pre-TKA patients (P = 0.005; P = 0.016, respectively). Higher KOOS scores indicate decreased severity of symptoms. The KOOS Quality of Life Score and the KOOS Function, Sports, and Recreational Activities Score were higher in post-TKA patients (P = 0.001; P b 0.001, respectively). The Global Assessment Rating Scale was lower (better) in post-TKA patients (P = 0.001). The PASE score was not significantly different between pre-TKA and postTKA patients (Table 4).
Discussion While post-TKA patients’ self-reported symptoms of knee pain, knee function, and overall quality of life were substantially better than those of the pre-TKA patients, there was no significant difference in objective measures of physical activity, as demonstrated with the accelerometry data, between pre-TKA and post-TKA patients. Of note, our data do not necessarily indicate that there is no improvement in accelerometry data following TKA, as our study observed different patients at the same time point rather than the same patients before and after TKA. However, a recent study by Harding et al measured physical activity using an accelerometer, before and 6 months after TKA or THA, and demonstrated that activity levels did not significantly increase within 6 months following either type of arthroplasty [13]. Importantly, there was a consistent and substantial difference in self-reported measures of pain and function between pre-TKA and post-TKA patients. While scores such as the KOOS Function, Sports, and Recreational Activity Score and the WOMAC Disability Score are designed to measure the functional status of the knee, the significant difference in these scores between pre-TKA and post-TKA patients was not consistent with the accelerometry data. This suggests that such self-reported measures of knee function are not reliably associated with actual physical activity. Similar findings demonstrating this disassociation have been demonstrated in several studies [13–16]. Furthermore, while a patient may experience objectively improved function in his or her knee following TKA, there may still not be increased physical activity after TKA. As the results of this study show, less reported pain with a higher perceived function and quality of life in post-TKA patients does not automatically translate into activity levels higher than those seen in pre-TKA patients. This is a clinically important finding for orthopedic surgeons as increased physical activity following TKA is considered a measure of a successful outcome and has been found to correlate with patient satisfaction after TKA [5]. Likewise, these findings may signify the need for increased patient education, and greater rehabilitation and physical therapy efforts following TKA. In both the pre-TKA and post-TKA patient groups, only 5% or less of patients were currently meeting the DHHS guidelines for physical activity. From a clinical perspective, this is important since increased physical activity is associated with an up to 30% risk reduction of all-cause mortality [21]. This finding was similar to those of Harding et al, who demonstrated that only 6% of TKA or THA patients met American Physical Activity
Table 2 Comparing Accelerometry Data between Pre-TKA Patients and Post-TKA Patients. Patients Pre-TKA (N = 63)
Patients Post-TKA (N = 60)
T-Score
Significance
Mean of Average Daily Activity Count Average Daily Minutes of Light Activity Average Daily Minutes of Moderate Activity Avg. Daily Bout Minutes of Mod-Vigorous Activity Avg. Daily Minutes of Mod-Vigorous Activity Avg. Daily Bout Minutes of Vigorous Activity Avg. Daily Minutes of Vigorous Activity
186,878.70 268.10 13.21 5.57 13.28 0.04 0.07
197,376.80 283.93 12.09 4.69 12.41 0.31 0.33
Patients Who Met DHHS Guidelines (N) Met DHHS Guidelines for Patients with Arthritis (N)
3 (4.8%) 3 (4.8%)
3 (5%) 3 (5%)
0.57 1.05 −0.37 −0.39 −0.28 1.26 1.20 Pearson Chi-Square 0.004 0.004
0.57 0.30 0.71 0.70 0.78 0.21 0.23 Significance 1.000 1.000
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Table 3 Accelerometry Results with Comorbidity Subgroup Analysis.
Comorbidity Index Score of 0
Comorbidity Index Score ≥ 1
No Hip Pain
Hip Pain Present
Mean of Average Daily Activity Count Average Daily Minutes of Light Activity Average Daily Minutes of Moderate Activity Avg. Daily Minutes of Vigorous Activity Mean of Average Daily Activity Count Average Daily Minutes of Light Activity Average Daily Minutes of Moderate Activity Avg. Daily Minutes of Vigorous Activity Mean of Average Daily Activity Count Average Daily Minutes of Light Activity Average Daily Minutes of Moderate Activity Avg. Daily Minutes of Vigorous Activity Mean of Average Daily Activity Count Average Daily Minutes of Light Activity Average Daily Minutes of Moderate Activity Avg. Daily Minutes of Vigorous Activity
Patients Pre-TKA
Patients Post-TKA
T-Score
Significance
210,166.67 280.59 16.75 0.09 143,478.52 244.81 6.62 0.02 192,449.51 277.63 13.23 0.03 174,694.96 241.52 14.14 0.17
234,541.00 316.40 16.27 0.57 157,727.35 249.36 7.56 0.07 196,529.87 274.60 13.18 0.19 199,116.13 306.37 9.45 0.76
−0.94 −1.94 0.10 −1.18 −0.64 −0.19 −0.38 −0.58 −0.18 0.18 0.01 −1.14 −0.65 −1.82 0.92 −0.80
0.35 0.06 0.92 0.25 0.53 0.85 0.70 0.56 0.86 0.85 0.99 0.26 0.52 0.08 0.37 0.43
⁎ “Hip Pain” defined as any pain in hip for more than half the days of 1 month during the past 12 months.
Guidelines preoperatively and only 2% of the same patient population met guidelines 6 months post-operatively [13]. Furthermore, there were no patients that met the DHHS guidelines for adults with arthritis who did not already meet the DHHS guidelines for the general population (i.e. only 2 patients met these guidelines). This suggests that post-TKA patients do not reach adequate physical activity levels, even when arthritis as a comorbidity is accounted for. These findings also highlight the need for further work in setting physical activity standards as well as a way to encourage and monitor them for post-TKA patients. While there was no significant difference between pre-TKA and post-TKA groups in the percentage of patients with at least 1 comorbidity, there was a trend toward post-TKA patients being more likely to have coexisting comorbidities (34.9% vs. 48.3%). As such, stratified analysis was necessary to observe whether this may have played a role in the findings of this study. While there was no significant difference in accelerometry data between pre-TKA and post-TKA patients who were without comorbidities, this analysis was likely underpowered as sample sizes were decreased for stratification. Further work is needed to elucidate the relationship between TKA and physical activity in patients with no coexisting comorbidities. While stratified analysis of patients with hip pain did not show a significant difference in physical activity levels between pre-TKA and postTKA groups, it still may be that arthritic comorbidities limit the functional outcome of TKA patients. As patients who receive TKA are likely to also suffer from disease in other joints, the symptomatic relief that is granted by TKA may not be enough to overcome the other comorbidities limiting their physical activity levels. Likewise, as TKA is generally a treatment for end-stage osteoarthritis, many patients may have already developed a sedentary lifestyle secondary to the morbidity of end-stage arthritis. Interestingly, of the patient-reported measures, the PASE score was the only one not significantly different between pre-TKA and postTable 4 Comparing Self-Reported Outcome Measures between Pre-TKA and Post-TKA Patients. Patients pre TKA (N=63)
Patients post TKA (N=60)
T-score
41.6 (29.0)
25.7 (27.4)
3.119
0.002
8.5 (6.0)
5.8 (6.5)
2.401
0.018
Combined WOMAC Disability Score
28.8 (20.9)
16.9 (19.1)
3.263
0.001
KOOS Quality of Life Score
49.4 (19.8)
62.0 (21.6)
-3.384
0.001
KOOS Combined Knee Pain Score
147.1 (31.9)
164.2 (35.4)
-2.831
0.005
KOOS Combined Knee Symptoms Score
155.9 (29.8)
167.9 (24.8)
-2.436
0.016
47.5 (24.7)
75.1 (21.2)
-4.421
<0.001
3.0 (2.3)
1.7 (2.0)
3.333
0.001
150.1 (76.5)
148.3 (83.0)
0.121
0.904
Combined Total WOMAC Score Combined WOMAC Pain Score
KOOS Function Score* Global Assessment Score PASE Score
⁎KOOS Function, Sports, and Recreational Activities Score. **Highlighted cells represent significant values (P b 0.05).
Significance
TKA groups, which was congruent with the accelerometry results. A recent study by Bolszak et al on the relationship between accelerometry data and the PASE questionnaire found that while the reliability of the PASE total score was acceptable for men, it was not for women [28]. Furthermore, they found the PASE score to have low agreement and construct validity [28]. While our study does not specifically evaluate the PASE score, it did not contradict the accelerometry findings. There are several previous studies that have utilized accelerometry data to study the relationship between arthroplasty and physical activity [13–16,34,35]. A study by Brandes et al demonstrated a significant increase in ambulation at 6 and 12 months post-TKA compared to pre-operative measurements in a group of 53 patients, though also found that the average ambulation for this patient group at 12 months post-TKA was still significantly less than healthy patients [14]. A study by de Groot et al of 80 patients with either TKA or total hip arthroplasty (THA) found a slight (0.7%) increase in movement related activity at 6 months post-operatively; however, there was no significant increase in movement related activity when only the TKA group (44 patients) was measured [15]. A follow-up study of this patient group at 4 years post-TKA demonstrated no significant increase in physical activity from 6 months post-TKA [35]. Walker et al studied 19 patients undergoing TKA and found that total ambulatory energy expenditure increased by 79% at 6 months post-TKA as compared to pre-TKA levels; an increase in number of steps taken and time spend standing also increased [16]. All of the aforementioned studies utilized a 24 to 48 hour monitoring period. According to previous work on accelerometry data, an estimated 3 to 5 days of recording time is necessary for accurate estimations of a patient’s regular physical activity [26]. A more recent study by Harding et al of 63 patients receiving either TKA or THA utilized 7 full days of accelerometry recording before arthroplasty and 6 months following arthroplasty; the study demonstrated no significant increase in physical activity at 6 months post-TKA compared to before the TKA procedure [13]. While the study by Harding et al established similar findings to our study, the sample size of TKA patients with valid data before and after TKA was relatively small in the Harding study (25 patients). Our study design was also significantly different, utilizing two separate patient groups for pre-TKA and post-TKA analysis. However, both of our findings indicate that TKA likely has little to no effect on actual physical activity levels. Previous contradictory findings [14–16] may be due to the shorter length of accelerometry recording utilized in these studies. There are several limitations to consider with this study. First, as we did not measure the accelerometry data from the same patients before and after TKA, we cannot definitively conclude that there is no improvement in physical activity following TKA. However, while this study design is limiting regarding such conclusions, it also has the advantage of avoiding a certain amount of patient bias based on patient expectations
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regarding TKA’s effect on physical activity. Second, as the data for this study were drawn from the OAI database, which did not measure accelerometry in a standardized timeline in regard to timing of TKA, the amount of time before and after TKA was highly variable. Therefore, our results are best regarded in terms of the general effects of TKA, knowing that physical activity data can vary during the first 6 months following TKA [14,15]. However, as the average time between TKA and data collection in the post-TKA group was more than 1 year, our accelerometry results also portend to longer follow-ups than most previous studies. Third, as the OAI study did not collect data regarding the type of implant or specific technique used for TKA, we can only speak generally regarding TKA outcomes as a whole. Conclusion While TKA is associated with significantly improved patientreported pain, function, and health-related quality of life, our study showed no significant difference in physical activity between patients who would eventually receive TKA and those who had already received TKA. Very few patients (5% or less) in either study group were currently meeting DHHS guidelines for physical activity. This suggests that despite patients’ perceived improvement in function and pain, physical activity does not tend to increase following TKA and remains below recommended levels. Both physicians and patients must take this into account when considering TKA for end-stage OA, realizing that surgery alone is unlikely to result in increased physical activity and that physical activity levels will likely remain below those of healthy individuals unless specific intervention is undertaken. Acknowledgement The OAI is a public–private partnership comprised of five contracts (N01-AR-2-2258; N01-AR-2-2259; N01-AR-2-2260; N01-AR-2-2261; N01-AR-2-2262) funded by the National Institutes of Health, a branch of the Department of Health and Human Services, and conducted by the OAI Study Investigators. Private funding partners include Merck Research Laboratories; Novartis Pharmaceuticals Corporation, GlaxoSmithKline; and Pfizer, Inc. Private sector funding for the OAI is managed by the Foundation for the National Institutes of Health. This manuscript was prepared using an OAI public use data set and does not necessarily reflect the opinions or views of the OAI investigators, the NIH, or the private funding partners. References 1. Ranawat CS, Flynn Jr WF, Saddler S, et al. Long-term results of the total condylar knee arthroplasty. A 15-year survivorship study. Clin Orthop Relat Res 1993(286):94. 2. Grayson CW, Decker RC. Total Joint Arthroplasty for Persons With Osteoarthritis. PM R 2012;4(5, Supplement):S97. 3. Zhang W, Moskowitz RW, Nuki G, et al. OARSI recommendations for the management of hip and knee osteoarthritis, Part II: OARSI evidence-based, expert consensus guidelines. Osteoarthritis Cartilage 2008;16(2):137. 4. Jüni P, Reichenbach S, Dieppe P. Osteoarthritis: rational approach to treating the individual. Best Pract Res Clin Rheumatol 2006;20(4):721. 5. Ethgen O, Bruyere O, Richy F, et al. Health-related quality of life in total hip and total knee arthroplasty. A qualitative and systematic review of the literature. J Bone Joint Surg Am 2004;86-A(5):963.
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6. Jones CA, Voaklander DC, Johnston DW, et al. Health related quality of life outcomes after total hip and knee arthroplasties in a community based population. J Rheumatol 2000;27(7):1745. 7. Daigle ME, Weinstein AM, Katz JN, et al. The cost-effectiveness of total joint arthroplasty: A systematic review of published literature. Best Pract Res Clin Rheumatol 2012;26(5):649. 8. Losina E, Walensky RP, Kessler CL, et al. Cost-effectiveness of Total Knee Arthroplasty in the United States. Arch Intern Med 2009;169(12):1113. 9. Jenkins PJ, Clement ND, Hamilton DF, et al. Predicting the cost-effectiveness of total hip and knee replacement: a health economic analysis. Bone Joint J 2013; 95-B(1):115. 10. Quintana JM, Escobar A, Arostegui I, et al. Health-related quality of life and appropriateness of knee or hip joint replacement. Arch Intern Med 2006;166(2):220. 11. Rasanen P, Paavolainen P, Sintonen H, et al. Effectiveness of hip or knee replacement surgery in terms of quality-adjusted life years and costs. Acta Orthop 2007;78(1):108. 12. Ruiz Jr D, Koenig L, Dall TM, et al. The direct and indirect costs to society of treatment for end-stage knee osteoarthritis. J Bone Joint Surg Am 2013;95(16):1473. 13. Harding P, Holland AE, Delany C, et al. Do activity levels increase after total hip and knee arthroplasty? Clin Orthop Relat Res 2014;472(5):1502. 14. Brandes M, Ringling M, Winter C, et al. Changes in physical activity and healthrelated quality of life during the first year after total knee arthroplasty. Arthritis Care Res (Hoboken) 2011;63(3):328. 15. de Groot IB, Bussmann HJ, Stam HJ, et al. Small increase of actual physical activity 6 months after total hip or knee arthroplasty. Clin Orthop Relat Res 2008; 466(9):2201. 16. Walker DJ, Heslop PS, Chandler C, et al. Measured ambulation and self-reported health status following total joint replacement for the osteoarthritic knee. Rheumatology (Oxford) 2002;41(7):755. 17. Bauman S, Williams D, Petruccelli D, et al. Physical activity after total joint replacement: a cross-sectional survey. Clin J Sport Med 2007;17(2):104. 18. Jones DL. A public health perspective on physical activity after total hip or knee arthroplasty for osteoarthritis. Phys Sportsmed 2011;39(4):70. 19. Kohl III HW, Craig CL, Lambert EV, et al. The pandemic of physical inactivity: global action for public health. Lancet 2012;380(9838):294. 20. Nilsdotter AK, Toksvig-Larsen S, Roos EM. Knee arthroplasty: are patients' expectations fulfilled? A prospective study of pain and function in 102 patients with 5-year follow-up. Acta Orthop 2009;80(1):55. 21. Committee, P.A.G.A.. Physical Activity Guidelines Advisory Committee ReportIn: U.S.D.o.H.a.H. Services, editor. ; 2008 [Washington, DC]. 22. Khaw KT, Wareham N, Bingham S, et al. Combined impact of health behaviours and mortality in men and women: the EPIC-Norfolk prospective population study. PLoS Med 2008;5(1) e12. 23. Hansen BH, Kolle E, Dyrstad SM, et al. Accelerometer-determined physical activity in adults and older people. Med Sci Sports Exerc 2012;44(2):266. 24. Corder K, van Sluijs EM. Invited commentary: comparing physical activity across countries–current strengths and weaknesses. Am J Epidemiol 2010; 171(10):1065. 25. Naal FD, Impellizzeri FM. How active are patients undergoing total joint arthroplasty?: A systematic review. Clin Orthop Relat Res 2010;468(7):1891. 26. Trost SG, McIver KL, Pate RR. Conducting accelerometer-based activity assessments in field-based research. Med Sci Sports Exerc 2005;37(11 Suppl.):S531. 27. Freedson PS, Miller K. Objective monitoring of physical activity using motion sensors and heart rate. Res Q Exerc Sport 2000;71(2 Suppl):S21. 28. Bolszak S, Casartelli NC, Impellizzeri FM, et al. Validity and reproducibility of the Physical Activity Scale for the Elderly (PASE) questionnaire for the measurement of the physical activity level in patients after total knee arthroplasty. BMC Musculoskelet Disord 2014;15:46. 29. Lester G. The Osteoarthritis Initiative: A NIH Public–Private Partnership. HSS J 2012; 8(1):62. 30. Troiano RP, Berrigan D, Dodd KW, et al. Physical activity in the United States measured by accelerometer. Med Sci Sports Exerc 2008;40(1):181. 31. Freedson PS, Melanson E, Sirard J. Calibration of the Computer Science and Applications, Inc. accelerometer. Med Sci Sports Exerc 1998;30(5):777. 32. Swartz AM, Strath SJ, Bassett DR, et al. Estimation of energy expenditure using CSA accelerometers at hip and wrist sites. Med Sci Sports Exerc 2000;32(9 Suppl):S450. 33. Bjorgul K, Novicoff WM, Saleh KJ. Evaluating comorbidities in total hip and knee arthroplasty: available instruments. J Orthop Traumatol 2010;11(4):203. 34. Jevsevar DS. Treatment of osteoarthritis of the knee: evidence-based guideline, 2nd edition. J Am Acad Orthop Surg 2013;21(9):571. 35. Vissers MM, Bussmann JB, de Groot IB, et al. Physical functioning four years after total hip and knee arthroplasty. Gait Posture 2013;38(2):310.
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Does Total Knee Arthroplasty Affect Physical Activity Levels? Data from the Osteoarthritis Initiative Timothy L. Kahn, BA, Ran Schwarzkopf, MD, MSc Deparment of Orthopaedic Surgery, University of California Irvine Medical Center, Orange, California
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Article history: Received 6 January 2015 Accepted 18 March 2015 Keywords: total knee arthroplasty accelerometer accelerometry physical activity patient-reported outcome measures physical activity guidelines
a b s t r a c t Total knee arthroplasty (TKA) is associated with improved patient-reported pain levels, function, and quality of life; however, it is poorly understood whether there is increased physical activity following TKA. Using data from the Osteoarthritis Initiative (OAI), we compare physical activity, as measured using an accelerometer, and patient-reported outcome measures of 60 patients who had already received a TKA with 63 patients who eventually received a TKA during the OAI study. There was no significant difference in activity levels between the two groups as measured by the accelerometer. Total WOMAC, KOOS Quality of Life, KOOS Knee Pain, and KOOS Function scores improved in the post-TKA compared to the pre-TKA group. In both pre-TKA and post-TKA groups, physical activity guidelines were met in only 5% or less. © 2015 Elsevier Inc. All rights reserved.
Total knee arthroplasty (TKA) is well established as the definitive treatment for end-stage knee osteoarthritis (OA) [1–4]. It is associated with improved patient-reported pain levels, increased function, and improved health-related quality of life [5,6]. From a financial perspective, TKA is also one of the most cost-effective procedures considering quality-of-life years gained per amount spent [5,7–12]. However, objective measures of physical activity following TKA are a relatively new area of research which is still poorly understood. Recent research has demonstrated that physical activity, as measured by accelerometry data, may not actually increase following TKA [13], although conflicting results have been reported in the literature [14–16]. Measuring physical activity following TKA is important both as an outcome measure [17] and a public health matter [18,19]. Many patients have high expectations regarding the amount of physical activity they will be able to achieve following TKA [20] and may become frustrated with their outcome if these expectations are not met or addressed. As a recent study by Harding et al demonstrated, very few patients, by 6 months following TKA, achieve activity levels recommended by the American Physical Activity Guidelines [13]. Consequently, inability to increase physical activity also places patients at increased risk of many disease processes, including cardiovascular disease, stroke, and overall mortality [21,22]. One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.03.016. Reprint requests: Ran Schwarzkopf, MD, MSc, Department of Orthopaedic Surgery, University of California Irvine Medical Center, 101 The City Drive South, Building 29, Pavilion III, Orange, CA 92868. http://dx.doi.org/10.1016/j.arth.2015.03.016 0883-5403/© 2015 Elsevier Inc. All rights reserved.
Accelerometry has become an important means of objectively measuring patients’ physical activity, as it is considered the most accurate means of doing so [23–25]. In contrast to a simple pedometer, accelerometers measure vertical acceleration of the subject, yielding data pertaining to duration, frequency, and intensity of exercise [25–27]. Consequently, accelerometry data provide important information regarding patient exercise which can be interpreted in metabolic equivalent task (MET) units. The utilization of accelerometry data is especially important considering the poor reliability of patient-reported physical activity [13,15,28]. For example, recent research on the physical activity for the elderly (PASE) questionnaire demonstrated several validity and reproducibility shortcomings, especially in women [28]. The primary objective of this study is to evaluate and compare the levels of physical activity using accelerometry data in two groups of patients: those who eventually receive TKA and those who have already received TKA. Secondary objectives include comparing patient-reported outcome measures including: pain, function, and health-related quality of life between these two groups of patients. Our hypothesis is that while patient-reported measures will be different between these groups, and improved in the post-TKA group compared to the preTKA group, there will be no difference in physical activity as measured by the accelerometer. Methods All data were obtained from the Osteoarthritis Initiative (OAI) database. The OAI is a publicly and privately funded prospective longitudinal observational study that studies the natural progression of osteoarthritis in patients [29]. The 4796 patients included in the OAI study were divided into subcohorts at the beginning of the study, which included
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a progression subcohort of 1389 patients who had clinically significant osteoarthritis at baseline, an incidence subcohort of 3285 patients who were determined to be at high-risk of developing clinically significant osteoarthritis, and a control cohort consisting of 122 patients with no symptoms or risk factors for osteoarthritis. All 4796 patients included in the study were required to attend a baseline visit followed by annual visits to their respective study center, where clinical, radiographic, and biomarker data were collected at each visit. The OAI study is also a multi-center study that is conducted at four different centers: (1) the Ohio State University, (2) the University of Maryland School of Medicine, (3) the University of Pittsburgh, and (4) Memorial Hospital of Rhode Island in Pawtucket, Rhode Island. All data, including radiographic images and biomarkers, are publically available at http://www.oai.ucsf.edu. At the 48 month visit of the OAI study, a subset of 2712 OAI participants were invited to join a physical activity ancillary study where participants would wear an ActiGraph GT1M uniaxial accelerometer (ActiGraph; Pensacola, Florida). Of these 2712 OAI participants, 2127 patients consented to participate. All patients were instructed on how to wear and use the accelerometer by trained OAI research staff. Patients were to wear the accelerometer from arising in the morning to retiring at night, except during water activities, for seven consecutive days. Patients were also instructed to maintain a daily log recording time spent in the water and cycling activities (both of which are not recorded accurately with the accelerometer). Upon return of the accelerometers to their respective study centers, data were analyzed to measure valid days of recording, which was defined as greater than or equal to 10 hours of recorded wear-time; 2001 patients provided one or more valid days of recording and 1927 patients provided four to seven valid days of recording. In our study, we studied two sets of patients taken from the accelerometry OAI study: “pre-TKA patients” and “post-TKA patients.” There was no overlap of patients between these two groups; as accelerometry data were only collected during the 48-month visit of the OAI study, these patient groups represent those who had TKA before accelerometry data collection (post-TKA patients) and those who had TKA after accelerometry data collection (pre-TKA patients). The preTKA patients included those who had not had a total knee arthroplasty prior to the 48 month visit where accelerometry data were collected, though did have an adjudicated TKA at an OAI visit any time after the 48 month visit where accelerometer data were collected (the OAI study currently has data up to an 84 month visit). Patients were included if they had an adjudicated TKA at any point following the accelerometry data collection and had 4 to 7 days of valid accelerometry recording — this inclusion criteria were based on previous studies which demonstrated that at least 3 to 5 days of wear-time is necessary to accurately predict overall physical activity for the patient [26]. The post-TKA patients included those who did have a TKA during the OAI study prior to the 48 month visit where accelerometry data were collected. Patients were included in this second group if they had an adjudicated TKA prior to accelerometry data collection and had 4 to 7 days of valid recording. Only patients with total knee arthroplasty were included in our study; those with partial knee arthroplasties were excluded. Accelerometry data for both patient sets were analyzed using cutpoints, which divide activity counts (units of accelerometry data that integrate vertical acceleration and deceleration) per minute into different physical activity intensity levels. Previously established cut-points in the literature have been designed to estimate the intensity of physical activity in terms of energy expenditure measured in MET units, with light activity corresponding to 1.5 to b3 METs, moderate activity to 3 to 6 METs, and vigorous activity to ≥6 METs [30–32]. In our study, we utilized “cut-points” published by Troiano et al, which were applied to the general adult population from the National Health and Nutrition Examination Study [30]. The final data for each patient are reported as minutes of activity above light, moderate, or vigorous activity threshold cut-points.
To better evaluate each patient’s physical activity, we also compared each patient’s accelerometry data to the 2008 Physical Activity Guidelines for Americans set forth by the United States Department of Health and Human Services (DHHS). The DHHS guidelines recommend 150 moderate intensity bout minutes (minutes are accumulated in 10 minute bouts) along with 75 vigorous bout minutes spread out across the week. We also compared accelerometry data to the 2008 DHHS guidelines of adults with arthritis, which recommends 150 moderate-to-vigorous bout minutes spread out across the week. As coexisting comorbidities could serve as confounding factors in this study, the Charlson Comorbidity Index was used to assess the level of comorbidity in each patient. The Charlson Comorbidity Index is a method of assessing and categorizing the amount of comorbidities in a given patient [33]. Contributing factors to the index are conditions such as heart failure, COPD, strokes, or diabetes. Patients from both the pre-TKA and post-TKA groups were stratified using this index into groups with either no comorbidities or at least 1 comorbidity. A similar stratification was performed for symptoms of hip pain. Patients were separated into two groups based on the presence or absence of any hip pain for more than half the days in a given month within the year previous to accelerometry data collection. For each of these stratifications, accelerometry data were compared across pre-TKA and postTKA groups. For each patient included in the study, self-reported outcome measures of knee function, knee pain, and overall quality of life were gathered from the 48-month visit (the same visit where the accelerometer data were collected on). Self-reported outcome measures included Western Ontario and McMaster osteoarthritis index (WOMAC) scores, Knee Injury and Osteoarthritis Outcome Score (KOOS), and Global Assessment score. As the WOMAC score, as well as some of the KOOS subsets, focuses on only one knee, such unilateral scores were combined by summing the scores from each knee together. The combined score was utilized as to have greater correspondence with physical activity and ambulation, which were pertinent to this study. The Global Assessment score asks the patient on a scale of 0 to 10, “Considering all ways knee pain and arthritis affect you, how are you doing today?”. Patient-reported physical activity was also measured using the PASE questionnaire, which was filled out by patients during the 48 month visit. The accelerometry data of pre-TKA patients and post-TKA patients were compared using SPSS Statistics (Version 22; SPSS Inc., Chicago, Illinois). Patients’ accelerometry data as well as self-reported function/ pain scores were compared using an independent samples T-test with Levene’s test to assess for equal variances among patient data. The percentage of patients achieving DHHS guidelines for physical activity were compared between pre-TKA and post-TKA groups using a Pearson’s chi-squared test. Results Based on our inclusion and exclusion criteria, there were 63 patients included in the pre-TKA group and 60 patients in the post-TKA group. Baseline characteristics of each of these groups can be seen in Table 1. The mean age of patients in pre-TKA and post-TKA groups was 68.4 (SD: 8.2) and 67.3 (SD: 8.7), respectively. The mean BMI in pre-TKA and post-TKA groups was 29.2 (SD: 4.8) and 31.1 (SD: 5.3), respectively. For the pre-TKA group, 34.9% of patients had at least 1 medical comorbidity, while in the post-TKA group, 48.3% of patients had at least 1 comorbidity (P = 0.123). In the pre-TKA group, 27.0% had hip pain for the majority of the days in a month within the previous year compared to 25.0% in the post-TKA group. All baseline characteristics of both study groups can be found in Table 1. For the pre-TKA patients, there was an average of 552.6 days (SD: 358.9) between the time of accelerometry data collection and TKA. For the post-TKA patients, there was an average of 624.8 days (SD: 420.6) between TKA and accelerometry data collection.
T.L. Kahn, R. Schwarzkopf / The Journal of Arthroplasty 30 (2015) 1521–1525 Table 1 Baseline Characteristics of Patients.
Age Gender (% male) Race (% of study population): White Black or African American Asian Non-white (other) Current Employment Status BMI Time before or after TKA (days)
Average Comorbidity Index Score (CIS) Patients with CIS ≥ 1 (%) Patients with Heart Failure (%) Patients with History of Stroke (%) Patients with COPD (%) Patients with Hip Pain (%)
Pre-TKA Patients (N = 63)
Post-TKA Patients (N = 60)
68.4 (8.2) 50.8%
67.3 (8.7) 50.0%
84.1% 12.7% 1.6% 1.6% 41.3% employed 29.2 (4.8) 552.6 (SD: 358.9; range: 7–1135) 0.67 34.9% 4.8% 4.8% 3.2% 27.0%
86.7% 11.7% 0.0% 1.7% 41.0% employed 31.1 (5.3) 624.8 (SD: 420.6; range: 65–1444) 0.73 48.3% 0.0% 11.7% 8.3% 25.0%
⁎ Includes COPD, emphysema, or chronic bronchitis. ⁎⁎ “Hip Pain” defined as any pain in hip for more than half the days of 1 month during the past 12 months.
Concerning the accelerometry data, there was no significant difference (P = 0.57) in the average daily activity count between preTKA patients (186,878.7 counts/day) and post-TKA patients (197,376.8 counts/day). Likewise, there was no significant difference between pre-TKA and post-TKA patients in daily minutes of either light (268.10 minutes vs. 283.93 minutes, respectively), moderate (13.21 minutes vs. 12.09 minutes), moderate-to-vigorous (13.28 minutes vs. 12.41 minutes), or vigorous activity (0.07 minutes vs. 0.33 minutes) (Table 2). Only 3 patients (4.8%) from the pre-TKA group and 3 patients (5.0%) from the post-TKA group met current DHHS activity guidelines for the general population based on accelerometry data. There was no difference in results when using the DHHS guidelines for patients with arthritis (Table 2). When stratified into groups with either no comorbidities or 1 or more comorbidities, there was no significant difference between preTKA and post-TKA patients in total activity count or daily minutes of either light, moderate, or vigorous activity (Table 3). Likewise, when patients were stratified into groups with either the presence or absence of hip pain for the majority of a month within the past year, there was no significant difference between pre-TKA and post-TKA patients in total activity count or daily minutes of light, moderate, or vigorous activity (Table 3). Regarding self-reported symptoms/function in the two patient groups, there was significantly lower combined WOMAC pain scores (P = 0.018), combined WOMAC disability scores (P = 0.001), and combined WOMAC total scores (P = 0.002) in the post-TKA group when compared to the pre-TKA group (Table 4). Higher WOMAC scores indicate greater severity of symptoms. Likewise, combined KOOS Knee
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Pain Score and combined KOOS Knee Symptoms Score were higher in post-TKA patients when compared to pre-TKA patients (P = 0.005; P = 0.016, respectively). Higher KOOS scores indicate decreased severity of symptoms. The KOOS Quality of Life Score and the KOOS Function, Sports, and Recreational Activities Score were higher in post-TKA patients (P = 0.001; P b 0.001, respectively). The Global Assessment Rating Scale was lower (better) in post-TKA patients (P = 0.001). The PASE score was not significantly different between pre-TKA and postTKA patients (Table 4).
Discussion While post-TKA patients’ self-reported symptoms of knee pain, knee function, and overall quality of life were substantially better than those of the pre-TKA patients, there was no significant difference in objective measures of physical activity, as demonstrated with the accelerometry data, between pre-TKA and post-TKA patients. Of note, our data do not necessarily indicate that there is no improvement in accelerometry data following TKA, as our study observed different patients at the same time point rather than the same patients before and after TKA. However, a recent study by Harding et al measured physical activity using an accelerometer, before and 6 months after TKA or THA, and demonstrated that activity levels did not significantly increase within 6 months following either type of arthroplasty [13]. Importantly, there was a consistent and substantial difference in self-reported measures of pain and function between pre-TKA and post-TKA patients. While scores such as the KOOS Function, Sports, and Recreational Activity Score and the WOMAC Disability Score are designed to measure the functional status of the knee, the significant difference in these scores between pre-TKA and post-TKA patients was not consistent with the accelerometry data. This suggests that such self-reported measures of knee function are not reliably associated with actual physical activity. Similar findings demonstrating this disassociation have been demonstrated in several studies [13–16]. Furthermore, while a patient may experience objectively improved function in his or her knee following TKA, there may still not be increased physical activity after TKA. As the results of this study show, less reported pain with a higher perceived function and quality of life in post-TKA patients does not automatically translate into activity levels higher than those seen in pre-TKA patients. This is a clinically important finding for orthopedic surgeons as increased physical activity following TKA is considered a measure of a successful outcome and has been found to correlate with patient satisfaction after TKA [5]. Likewise, these findings may signify the need for increased patient education, and greater rehabilitation and physical therapy efforts following TKA. In both the pre-TKA and post-TKA patient groups, only 5% or less of patients were currently meeting the DHHS guidelines for physical activity. From a clinical perspective, this is important since increased physical activity is associated with an up to 30% risk reduction of all-cause mortality [21]. This finding was similar to those of Harding et al, who demonstrated that only 6% of TKA or THA patients met American Physical Activity
Table 2 Comparing Accelerometry Data between Pre-TKA Patients and Post-TKA Patients. Patients Pre-TKA (N = 63)
Patients Post-TKA (N = 60)
T-Score
Significance
Mean of Average Daily Activity Count Average Daily Minutes of Light Activity Average Daily Minutes of Moderate Activity Avg. Daily Bout Minutes of Mod-Vigorous Activity Avg. Daily Minutes of Mod-Vigorous Activity Avg. Daily Bout Minutes of Vigorous Activity Avg. Daily Minutes of Vigorous Activity
186,878.70 268.10 13.21 5.57 13.28 0.04 0.07
197,376.80 283.93 12.09 4.69 12.41 0.31 0.33
Patients Who Met DHHS Guidelines (N) Met DHHS Guidelines for Patients with Arthritis (N)
3 (4.8%) 3 (4.8%)
3 (5%) 3 (5%)
0.57 1.05 −0.37 −0.39 −0.28 1.26 1.20 Pearson Chi-Square 0.004 0.004
0.57 0.30 0.71 0.70 0.78 0.21 0.23 Significance 1.000 1.000
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Table 3 Accelerometry Results with Comorbidity Subgroup Analysis.
Comorbidity Index Score of 0
Comorbidity Index Score ≥ 1
No Hip Pain
Hip Pain Present
Mean of Average Daily Activity Count Average Daily Minutes of Light Activity Average Daily Minutes of Moderate Activity Avg. Daily Minutes of Vigorous Activity Mean of Average Daily Activity Count Average Daily Minutes of Light Activity Average Daily Minutes of Moderate Activity Avg. Daily Minutes of Vigorous Activity Mean of Average Daily Activity Count Average Daily Minutes of Light Activity Average Daily Minutes of Moderate Activity Avg. Daily Minutes of Vigorous Activity Mean of Average Daily Activity Count Average Daily Minutes of Light Activity Average Daily Minutes of Moderate Activity Avg. Daily Minutes of Vigorous Activity
Patients Pre-TKA
Patients Post-TKA
T-Score
Significance
210,166.67 280.59 16.75 0.09 143,478.52 244.81 6.62 0.02 192,449.51 277.63 13.23 0.03 174,694.96 241.52 14.14 0.17
234,541.00 316.40 16.27 0.57 157,727.35 249.36 7.56 0.07 196,529.87 274.60 13.18 0.19 199,116.13 306.37 9.45 0.76
−0.94 −1.94 0.10 −1.18 −0.64 −0.19 −0.38 −0.58 −0.18 0.18 0.01 −1.14 −0.65 −1.82 0.92 −0.80
0.35 0.06 0.92 0.25 0.53 0.85 0.70 0.56 0.86 0.85 0.99 0.26 0.52 0.08 0.37 0.43
⁎ “Hip Pain” defined as any pain in hip for more than half the days of 1 month during the past 12 months.
Guidelines preoperatively and only 2% of the same patient population met guidelines 6 months post-operatively [13]. Furthermore, there were no patients that met the DHHS guidelines for adults with arthritis who did not already meet the DHHS guidelines for the general population (i.e. only 2 patients met these guidelines). This suggests that post-TKA patients do not reach adequate physical activity levels, even when arthritis as a comorbidity is accounted for. These findings also highlight the need for further work in setting physical activity standards as well as a way to encourage and monitor them for post-TKA patients. While there was no significant difference between pre-TKA and post-TKA groups in the percentage of patients with at least 1 comorbidity, there was a trend toward post-TKA patients being more likely to have coexisting comorbidities (34.9% vs. 48.3%). As such, stratified analysis was necessary to observe whether this may have played a role in the findings of this study. While there was no significant difference in accelerometry data between pre-TKA and post-TKA patients who were without comorbidities, this analysis was likely underpowered as sample sizes were decreased for stratification. Further work is needed to elucidate the relationship between TKA and physical activity in patients with no coexisting comorbidities. While stratified analysis of patients with hip pain did not show a significant difference in physical activity levels between pre-TKA and postTKA groups, it still may be that arthritic comorbidities limit the functional outcome of TKA patients. As patients who receive TKA are likely to also suffer from disease in other joints, the symptomatic relief that is granted by TKA may not be enough to overcome the other comorbidities limiting their physical activity levels. Likewise, as TKA is generally a treatment for end-stage osteoarthritis, many patients may have already developed a sedentary lifestyle secondary to the morbidity of end-stage arthritis. Interestingly, of the patient-reported measures, the PASE score was the only one not significantly different between pre-TKA and postTable 4 Comparing Self-Reported Outcome Measures between Pre-TKA and Post-TKA Patients. Patients pre TKA (N=63)
Patients post TKA (N=60)
T-score
41.6 (29.0)
25.7 (27.4)
3.119
0.002
8.5 (6.0)
5.8 (6.5)
2.401
0.018
Combined WOMAC Disability Score
28.8 (20.9)
16.9 (19.1)
3.263
0.001
KOOS Quality of Life Score
49.4 (19.8)
62.0 (21.6)
-3.384
0.001
KOOS Combined Knee Pain Score
147.1 (31.9)
164.2 (35.4)
-2.831
0.005
KOOS Combined Knee Symptoms Score
155.9 (29.8)
167.9 (24.8)
-2.436
0.016
47.5 (24.7)
75.1 (21.2)
-4.421
<0.001
3.0 (2.3)
1.7 (2.0)
3.333
0.001
150.1 (76.5)
148.3 (83.0)
0.121
0.904
Combined Total WOMAC Score Combined WOMAC Pain Score
KOOS Function Score* Global Assessment Score PASE Score
⁎KOOS Function, Sports, and Recreational Activities Score. **Highlighted cells represent significant values (P b 0.05).
Significance
TKA groups, which was congruent with the accelerometry results. A recent study by Bolszak et al on the relationship between accelerometry data and the PASE questionnaire found that while the reliability of the PASE total score was acceptable for men, it was not for women [28]. Furthermore, they found the PASE score to have low agreement and construct validity [28]. While our study does not specifically evaluate the PASE score, it did not contradict the accelerometry findings. There are several previous studies that have utilized accelerometry data to study the relationship between arthroplasty and physical activity [13–16,34,35]. A study by Brandes et al demonstrated a significant increase in ambulation at 6 and 12 months post-TKA compared to pre-operative measurements in a group of 53 patients, though also found that the average ambulation for this patient group at 12 months post-TKA was still significantly less than healthy patients [14]. A study by de Groot et al of 80 patients with either TKA or total hip arthroplasty (THA) found a slight (0.7%) increase in movement related activity at 6 months post-operatively; however, there was no significant increase in movement related activity when only the TKA group (44 patients) was measured [15]. A follow-up study of this patient group at 4 years post-TKA demonstrated no significant increase in physical activity from 6 months post-TKA [35]. Walker et al studied 19 patients undergoing TKA and found that total ambulatory energy expenditure increased by 79% at 6 months post-TKA as compared to pre-TKA levels; an increase in number of steps taken and time spend standing also increased [16]. All of the aforementioned studies utilized a 24 to 48 hour monitoring period. According to previous work on accelerometry data, an estimated 3 to 5 days of recording time is necessary for accurate estimations of a patient’s regular physical activity [26]. A more recent study by Harding et al of 63 patients receiving either TKA or THA utilized 7 full days of accelerometry recording before arthroplasty and 6 months following arthroplasty; the study demonstrated no significant increase in physical activity at 6 months post-TKA compared to before the TKA procedure [13]. While the study by Harding et al established similar findings to our study, the sample size of TKA patients with valid data before and after TKA was relatively small in the Harding study (25 patients). Our study design was also significantly different, utilizing two separate patient groups for pre-TKA and post-TKA analysis. However, both of our findings indicate that TKA likely has little to no effect on actual physical activity levels. Previous contradictory findings [14–16] may be due to the shorter length of accelerometry recording utilized in these studies. There are several limitations to consider with this study. First, as we did not measure the accelerometry data from the same patients before and after TKA, we cannot definitively conclude that there is no improvement in physical activity following TKA. However, while this study design is limiting regarding such conclusions, it also has the advantage of avoiding a certain amount of patient bias based on patient expectations
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regarding TKA’s effect on physical activity. Second, as the data for this study were drawn from the OAI database, which did not measure accelerometry in a standardized timeline in regard to timing of TKA, the amount of time before and after TKA was highly variable. Therefore, our results are best regarded in terms of the general effects of TKA, knowing that physical activity data can vary during the first 6 months following TKA [14,15]. However, as the average time between TKA and data collection in the post-TKA group was more than 1 year, our accelerometry results also portend to longer follow-ups than most previous studies. Third, as the OAI study did not collect data regarding the type of implant or specific technique used for TKA, we can only speak generally regarding TKA outcomes as a whole. Conclusion While TKA is associated with significantly improved patientreported pain, function, and health-related quality of life, our study showed no significant difference in physical activity between patients who would eventually receive TKA and those who had already received TKA. Very few patients (5% or less) in either study group were currently meeting DHHS guidelines for physical activity. This suggests that despite patients’ perceived improvement in function and pain, physical activity does not tend to increase following TKA and remains below recommended levels. Both physicians and patients must take this into account when considering TKA for end-stage OA, realizing that surgery alone is unlikely to result in increased physical activity and that physical activity levels will likely remain below those of healthy individuals unless specific intervention is undertaken. Acknowledgement The OAI is a public–private partnership comprised of five contracts (N01-AR-2-2258; N01-AR-2-2259; N01-AR-2-2260; N01-AR-2-2261; N01-AR-2-2262) funded by the National Institutes of Health, a branch of the Department of Health and Human Services, and conducted by the OAI Study Investigators. Private funding partners include Merck Research Laboratories; Novartis Pharmaceuticals Corporation, GlaxoSmithKline; and Pfizer, Inc. Private sector funding for the OAI is managed by the Foundation for the National Institutes of Health. This manuscript was prepared using an OAI public use data set and does not necessarily reflect the opinions or views of the OAI investigators, the NIH, or the private funding partners. References 1. Ranawat CS, Flynn Jr WF, Saddler S, et al. Long-term results of the total condylar knee arthroplasty. A 15-year survivorship study. Clin Orthop Relat Res 1993(286):94. 2. Grayson CW, Decker RC. Total Joint Arthroplasty for Persons With Osteoarthritis. PM R 2012;4(5, Supplement):S97. 3. Zhang W, Moskowitz RW, Nuki G, et al. OARSI recommendations for the management of hip and knee osteoarthritis, Part II: OARSI evidence-based, expert consensus guidelines. Osteoarthritis Cartilage 2008;16(2):137. 4. Jüni P, Reichenbach S, Dieppe P. Osteoarthritis: rational approach to treating the individual. Best Pract Res Clin Rheumatol 2006;20(4):721. 5. Ethgen O, Bruyere O, Richy F, et al. Health-related quality of life in total hip and total knee arthroplasty. A qualitative and systematic review of the literature. J Bone Joint Surg Am 2004;86-A(5):963.
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