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A longitudinal study of quality of life and functional status in total hip and total knee replacement patients
International Journal of Orthopaedic and Trauma Nursing (2015) 19, 102–113
International Journal of Orthopaedic and Trauma Nursing www.elsevier.com/locate/ijotn
A longitudinal study of quality of life and functional status in total hip and total knee replacement patients Lynda L. Mandzuk RN, MN (Clinical Nurse Specialist) a,*, Diana E. McMillan RN, PhD (Associate Professor) b, Eric R. Bohm BEng, MD, MSc, FRCSC (Associate Professor) c a
Rehabilitation Geriatrics Program, St. Boniface Hospital, 409 Taché Avenue, Winnipeg, Manitoba, Canada, R2H 2A6 b College of Nursing, Faculty of Health Sciences, Helen Glass Centre, University of Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2 c Concordia Joint Replacement Group, Department of Surgery, University of Manitoba, 1155 Concordia Avenue, Winnipeg, Manitoba, Canada, R2K 2M4
KEYWORDS Quality of life; Functional status; Total hip arthroplasty; Total knee arthroplasty
Abstract Background: Primary total hip and primary total knee surgeries are commonly performed to improve patients’ quality of life and functional status. Aim: This longitudinal retrospective study (N = 851) examined self-reported quality of life and functional status over the preoperative and postoperative periods: 12 months prior to surgery, one month prior to surgery and 12 months following surgery. Methods: A linear mixed effects model was used to analyze the changes in quality of life and functional status over the sampling period. Results: Patients in the convenience sample reported improvements in quality of life and functional status utilizing the SF-12 and Oxford Hip and Oxford Knee, although differences were noted by procedure and gender. Total hip patients tended to demonstrate greater improvement than total knee patients and males reported higher levels of physical and mental quality of life as well as functional status when compared to females. Of particular note was that mental health scores were consistently lower in both total hip and total knee replacement patients across the perioperative period and up to one year postoperative. Conclusion: This study identifies an opportunity for health care providers to proactively address the mental health of total hip and total knee replacement patients throughout their joint replacement trajectory. © 2014 Elsevier Ltd. All rights reserved.
* Corresponding author. E-mail address: [email protected] (L.L. Mandzuk). http://dx.doi.org/10.1016/j.ijotn.2014.07.001 1878-1241/© 2014 Elsevier Ltd. All rights reserved.
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Editor’s comment In a world constrained by available resources the outcomes of surgery are central to measuring success. Total hip and knee arthroplasties are focused on improving patients’ pain experience, their functional status and enhancing their quality of life. This important study adds to the growing body of evidence that demonstrates that although the outcomes of arthroplasty surgery vary between patients with different characteristics, there is a general improvement in both function and quality of life which makes the surgery worthwhile. Longitudinal research has the advantage of being able to provide a picture over time – taking a ‘snapshot’ at only one point in time is likely to be far less valuable. The longer term impact on mental health and well-being shown by this study is an important area for both further research and for practice development. JS-T
Introduction The two most prevalent primary joint replacement surgeries are total hip (THR) and total knee (TKR) replacements. In 2010–2011 these two surgeries accounted for 35,295 hospitalizations (Canadian Institute for Health Information (CIHI), 2013). Many patients experience lengthy preoperative waits. In the current study a wait was considered lengthy if it surpassed the recommended 26 weeks (Wait Time Alliance, 2012). The trend of a 13% increase in hospitalizations for total joint replacement surgeries in the past five years (CIHI, 2013) is expected to add to wait times.
Literature Two primary clinical aims associated with joint replacement surgery are to decrease pain and to decrease disability (Canadian Orthopaedic Foundation, 2010). For the purposes of this study, quality of life (QOL) and functional status (FS) were the related health status markers that were evaluated. QOL, in this study, is defined as the physical and mental wellbeing of the individual. Because QOL is multidimensional (Ferrans and Powers, 1992) and dynamic (Berra, 2003) it can mean “different things to different people” as well as “different things to the same person over a disease trajectory” (Sprangers and Schwartz, 1999, p. 1507). FS focuses on a balance between what the individual does and what the individual aspires to do (Wang, 2004). FS activities help the individual to achieve fundamental needs, roles and health. The domains of both QOL (Goodridge et al., 2005) and FS (Patrick and Chiang, 2000) are physical, psychological and social in nature. Given the often lengthy wait time experience and the significance of QOL and FS to individuals’
well-being it is important to examine QOL and FS across the care trajectory for THR and TKR patients. During the wait for joint replacement surgery QOL and FS are impaired (McHugh et al., 2008). With respect to procedure, some researchers (Choi et al., 2012; de Beer et al., 2012) report that THR patients have better FS postoperatively when compared to TKR patients. Health outcome differences by gender were also identified in the literature. In some studies, females tended to have less improvement in their QOL following THR surgery compared to males (Quintana et al., 2009). Others reported that females had more functional decline at the time of their TKR surgery but they gained FS at a faster rate and by 12 months postoperatively they had similar functional levels as males (Liebs et al., 2011). In terms of comparative longitudinal research, several studies explored the preoperative and postoperative phases. Ostendorf et al. (2004) evaluated both FS and QOL outcomes using the Oxford Hip Score (OHS), 36-Item Medical Outcomes Short Form (SF-36), EuroQOL Health Status and the Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) instruments when THR patients were placed on the waiting list, prior to surgery and three and 12 months postoperative. Garbuz et al. (2006) also studied THR patients’ functional outcomes with the use of the WOMAC but only at the time of orthopedic consultation and one year following surgery. De Beer et al. (2012) focused on FS one year postoperatively utilizing the OHS and Oxford Knee Score (OKS) in THR and TKR patients respectively. This current study provides a more complete examination of QOL and FS during the preoperative and postoperative phases in both the THR and TKR populations. More importantly, this research addresses the scarcity of longitudinal inquiry providing insight into QOL and FS over time with consideration for procedure and gender.
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Methods This longitudinal study examined self-reported QOL and FS data for THR and TKR patients over time. Data were collected across the preoperative wait period and up to one year postoperative. Data were retrospective, having been collected previously and analyzed later. Patients had their surgery in urban community hospitals in a mid-western city in Canada between October 2004 and May 2007. A convenience sample of 851 patients who had waited for and then had surgery, either a primary THR or primary TKR, was included from the database following study institutional ethical approval. Participant inclusion criteria were as follows: (1a) either a primary THR or primary TKR was proposed; (1b) either a primary THR or primary TKR surgery was performed; (2) understood verbal and written English; (3) cognitively capable of completing the instruments and (4) anonymized data were accessible from a joint replacement registry. General health-related QOL was measured using the 12-Item Medical Outcomes Short Form (SF-12) (Ware et al., 1996). The SF-12 yields physical (PCS) and mental (MCS) component summaries with total scores of 0–100 for each. Lower scores indicated lower QOL. Functional status was assessed using the OHS (Dawson et al., 1996) and the OKS (Dawson et al., 1998). Total scores range from 12 to 60 with lower scores indicating less perceived disability with functional ability. The tools focus on the physical, psychological and social aspects of FS while concentrating on pain, function, and activity. While the OHS and OKS are similar in format, scoring and total score ranges, there are six items that differ making the measures comparable but not identical. The study involved three approximate measurement points: 12 months prior to surgery (waitlist), one month prior to surgery (preoperative) and 12 months following surgery (postoperative). To ensure that measurement points closely reflected the target measurement points and that there was sufficient opportunity for clinical change to occur a measurement point criteria was used; scores that were compared had a minimum of six months in between them. Using the Statistical Package for the Social Sciences (Version 15.0), two approaches were used to explore the QOL and FS data related to time, procedure and gender. In Dataset One, the relationship of QOL and FS was examined using the 1 month preoperative to 12 months postoperative data points. All possible patients in the analysis who met the measurement point criteria were included [N = 798; 92/ 890 patients excluded because of short (<6 months)
L.L. Mandzuk et al. data window]. In Dataset Two, the relationship of QOL over three target measurement points was explored: 12 months preoperative, 1 month preoperative and 12 months postoperative. This approach was limited to patients in the sample who met the criteria for all three measurement points [N = 53; 49/ 102 patients excluded because of short (<6 month) data window]. A linear mixed effects model was used to analyze the changes in QOL and FS over the sampling periods. In a repeated measures context, this approach allows valid inferences to be made comparing procedures at all time points by accounting for the correlation between multiple observations made on the same subject. Repeated measures mixed effects models are analogous to repeated measures analysis of variance (ANOVA) except that the former are more flexible since they can directly model the covariance structure instead of imposing the assumption of compound symmetry. Also, they handle missing data better as ANOVA eliminates subjects that have any missing data, whereas a mixed effects model will keep all the information in the dataset. Statistical significance was set at p ≤ .05. (B. Dufault, personal communication, April 29, 2010).
Results Adjustments for the wait time and QOL component scores were applied to the mixed effects models as appropriate; age and body mass index (BMI) were determined to be nonsignificant factors within all models.
Dataset One: QOL and FS in the preoperative to postoperative period Dataset One (N = 798) was composed of 45.1% males and 54.9% females. THR surgery was performed on 43.6% of the patients while 56.4% of patients had TKR surgery. Hip surgery patients were on average both younger and lighter (64.8 ± 12.3 years; BMI 28.8 ± 5.3 kg/m2) than those undergoing TKR surgery (67.3 ± 10.3 years; BMI 31.9 ± 6.7 kg/m2). These differences were significant (p = .0024 and p < .0001, respectively). In terms of wait time, TKR patients waited on average longer than THR patients (43.0 ± 29.1 weeks vs 50.6 ± 31.5 weeks, p = .0005) (see Table 1). Using the mixed effects model it was determined that there was a significant improvement in QOL with respect to the PCS for both THR (27.9 ± .5 vs 42.6 ± .5) and TKR (29.2 ± .5 vs 40.2 ± .5) patients from the preoperative to postoperative period,
Longitudinal quality of life and functional status Table 1
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Demographics for Dataset One and Dataset Two by procedure
Variables
Dataset One (N = 798)
Dataset Two (N = 53)
Total hip
Total knee
Total hip
Total knee
Procedure n (%) Gender n (%) Male Female Age (years) Mean (SD) Range BMI (kg/m2) Mean (SD) Range Wait (weeks) Mean (SD) Range
348 (43.6%)
450 (56.4%)
28 (52.8%)
25 (47.2%)
177 (50.4%) 171 (49.1%)
183 (40.7%) 267(59.3%)
15 (53.6%) 13 (46.4%)
11 (44.0%) 14 (56.0%)
64.8 (12.3) 18–92
67.3 (10.3) 32–91
61.1 (10.3) 41–79
68.52 (11.0) 49–87
28.8 (5.3) 17.5–49.0
31.9 (6.7) 16.1–60.7
30.1 (5.0) 20.7–43.0
31.74 (5.6) 23.2–47.0
43.0 (29.1) 3–162
50.6 (31.5) 0–143
59.7 (11.8) 35–84
65.08 (14.8) 44–103
Note. Dataset One: 1 month prior to surgery and 12 months following surgery and Dataset Two: 12 months prior to surgery, 1 month prior to surgery, and 12 months following surgery.
respectively, (p < .0001) (see Table 2). However, there was no significant between group difference in this regard (see Fig. 1). The PCS scores improved significantly preoperatively to postoperatively
(p < .0001) for both males (30.1 ± .5 vs 43.1 ± .5) and females (27.4 ± .5 vs 39.7 ± .5) with males reporting higher mean scores at both time points (p < .0001).
Table 2 Comparison of least squares mean physical and mental component summaries and least squares mean Oxford Hip/Knee Scores for Dataset One by procedure (N = 798) Procedure/measure/time THR PCS 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post TKR PCS 1 month prior to surgery 12 months following surgery Diff 1 month prior–12 months post THR MCS 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post TKR MCS 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post THR Oxfordo 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post TKR Oxfordo 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post
Least squares Differences of least means squares means (p value) 27.9 ± .5 42.6 ± .5 29.2 ± .5 40.2 ± .5 49.2 ± .7 54.4 ± .6 51.5 ± .6 53.4 ± .5 42.5 ± .4 19.6 ± .5 40.4 ± .4 23.8 ± .4
−14.8 ± .6 (<.0001)
−10.1 ± .5 (<.0001)
−5.1 ± .7 (<.0001)*
−1.9 ± .6 (.0018)*
22.9 ± .6 (<.0001)**
16.6 ± .5 (<.0001)**
Note. Dataset One: 1 month prior to surgery and 12 months following surgery; THR: total hip replacement; TKR: total knee replacement, PCS: physical component summary; MCS: mental component summary; Oxford: Oxford Hip/Knee Score; Diff: difference between; THR n = 348; TKR n = 450; * model adjusted by PCS, ** model adjusted by length of wait; o missing data for Oxford scores 1 month prior to surgery = 97 and 12 months after surgery = 66.
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Physical Component Summary Mean Scores
60 50 40 Hip
30
Knee
20 10 0 1 month preoperative
12 months postoperative
Two Time Points
Fig. 1
Mean physical health scores over two time points compared by procedure.
Similarly, there was a significant improvement in QOL with respect to the MCS scores preoperatively to postoperatively for both THR (49.2 ± .7 vs 54.4 ± .6; p < .0001) and TKR patients (51.5 ± .6 vs 53.4 ± .5; p = .0018). While there was no between group difference for MCS scores, the MCS scores for THR patients indicated significantly faster improvement than patients receiving TKR surgery (p < .0001). Significant improvement in MCS scores was also seen preoperatively to postoperatively in both males (51.8 ± .6 vs 54.4 ± .6; p = .0002) and females (49.6 ± .6 vs 53.2 ± .5; p < .0001) although a comparison of the improvements in MCS was not significantly different between males and females. In terms of functional status, a significant change was seen in the Oxford-12 scores by time (p < .0001) and by procedure (p = .0311). There was a significant improvement in the FS scores between the two time points and THR patients (42.5 ± .4 vs 19.6 ± .5) had higher levels of FS at 12 months postoperatively than TKR patients (40.4 ± .4 vs 23.8 ± .4). There was
also a significant interaction between procedure and time, indicating that THR patients improved in their FS at a greater rate than TKR patients. THR patients had on average a poorer FS score preoperatively and a better FS score postoperatively (p < .0001) (see Fig. 2). It is important to remember that while the OHS and OKS are similar, they are not identical tools as they are joint-specific. Both males and females showed significant improvement in FS scores preoperatively to postoperatively (p < .0001) (see Table 3). Males reported significantly better FS scores both preoperatively and postoperatively (39.4 ± .4 and 20.8 ± .5, p < .0001) compared to females (43.1 ± .4 and 22.9 ± .5, p < .0001). However, there was a significant interaction between gender and time (p = .0428) with a greater amount of improvement in the FS of females than males. Females had on average a much poorer FS preoperatively and, while they improved significantly, the females continued to have poorer FS postoperatively when compared to males.
Oxford Mean Scores
60 50 40 Hip
30
Knee
20 10 0 1 month preoperative
12 months postoperative Two Time Points
Fig. 2
Mean functional status scores over two time points compared by procedure.
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Table 3 Comparison of least squares mean physical and mental component summaries and least squares mean Oxford Hip/Knee Scores for Dataset One by gender (N = 798). Gender/measure/time Male PCS 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post Female PCS 1 month prior to surgery 12 months following surgery Diff 1 month prior–12 months post Male MCS 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post Female MCS 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post Male Oxfordo 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post Female Oxfordo 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post
Least squares Differences of least means squares means (p value) 30.1 ± .5 43.1 ± .5 27.4 ± .5 39.7 ± .5 51.8 ± .6 54.4 ± .6 49.6 ± .6 53.2 ± .5 39.4 ± .4 20.8 ± .5 43.1 ± .4 22.9 ± .5
−12.9 ± .6 (<.0001)*
−12.3 ± .6 (<.0001)*
−2.6 ± .7 (.0002)**
−3.7 ± .6 (<.0001)**
18.6 ± .6 (<.0001)***
20.2 ± .5 (<.0001)***
Note. Dataset One: 1 month prior to surgery and 12 months following surgery; THR: total hip replacement; TKR: total knee replacement, PCS: physical component summary; MCS: mental component summary; Oxford: Oxford Hip/Knee Score; Diff: difference between; male n = 360; female n = 438; * model adjusted by MCS; ** model adjusted by PCS; *** model adjusted by length of wait; o missing data for Oxford scores 1 month prior to surgery = 97 and 12 months after surgery = 66.
Dataset Two: QOL in the waitlist to preoperative to postoperative periods Dataset Two measured QOL for patients at three measurement points (N = 53). With respect to this smaller second dataset, the demographic characteristics were similar to the larger dataset with the exception that the smaller dataset had a longer mean wait time (see Table 1). The average wait time in weeks was 59.7 ± 11.8 for THR surgery and 65.1 ± 14.8 for TKR surgery. Within Dataset Two the TKR patients waited on average six more weeks than the THR patients, but this difference was not statistically significant. Based on the three measurement point data (i.e., 12 months preoperative, 1 month preoperative, 12 months postoperative) there was significant improvement in physical health as measured by PCS scores, over time (p < .0001) for THR and TKR patients (see Table 4 for specific time point differences). This significant improvement in the physical component of QOL was almost exclusively attributed to the change seen 1 month preoperatively to postoperatively (see
Fig. 3). Although the amount of change over measurement points was comparatively greater in THR patients, this difference between procedures was not significant (p = .0512). There were significant changes in physical health scores by time (p < .0001) and gender (p = .0276). Specifically, and similar to findings using the larger dataset, physical health scores improved significantly for both males and females with males reporting significantly higher physical health scores overall compared to females (see Fig. 4). Using the three point, mixed effects model analysis it was determined that there was a significant improvement in QOL mental health scores by time (p = .0199) (see Table 5). Specifically mental health, as measured by MCS scores, improved significantly over time for both THR and TKR patients, with the change primarily attributed again to the improvement 1 month preoperatively to postoperatively. There were no significant mean differences in MCS scores between THR and TKR patients nor in the rate of their improvement. Mental health scores did improve significantly over time (p = .0383) for both
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Table 4 Comparison of least squares mean physical and mental component summaries for Dataset Two by procedure (N = 53). Procedure/measure/time
Least squares means
THR PCS 12 months prior to surgery 1 month prior to surgery 12 months after surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 months post Diff 1 month prior–12 months post TKR PCS 12 months prior to surgery 1 month prior to surgery 12 months following surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 months post Diff 1 month prior–12 months post THR MCS 12 months prior to surgery 1 month prior to surgery 12 months after surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 months post Diff 1 month prior–12 months post TKR MCS 12 months prior to surgery 1 month prior to surgery 12 months after surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 months post Diff 1 month prior–12 months post
27.2 ± 1.4 28.1 ± 1.4 47.1 ± 2.5
27.6 ± 1.5 27.3 ± 1.4 39.1 ± 2.6
45.4 ± 2.6 46.1 ± 2.5 54.6 ± 2.7
49.2 ± 2.8 50.1 ± 2.6 53.1 ± 2.5
Differences of least squares means (p value)
−0.9 ± 1.1 (.4282)* −19.9 ± 2.3 (<.0001)* −19.0 ± 2.3 (<.0001)*
−0.2 ± 1.2 (.8591)* −11.5 ± 2.4 (<.0001)* −11.7 ± 2.4 (<.0001)*
−0.7 ± 1.6 (.6754)** −9.2 ± 3.1 (.0035)** −8.5 ± 2.7 (.0024)**
−.9 ± 1.7 (.6018)** −3.9 ± 2.8 (.1755)** −3.0 ± 2.5 (.2325)**
Note. Dataset Two: 12 months prior to surgery, 1 month prior to surgery, and 12 months following surgery; Oxford Hip/Knee was not collected at 12 months prior to surgery therefore no Oxford scores for Dataset Two; THR: total hip replacement; TKR: total knee replacement, PCS: physical component summary; MCS: mental component summary; Diff: difference between; THR n = 28; TKR n = 25; * model adjusted by PCS; ** model adjusted by MCS.
Physical Component Summary Mean Scores
males and females and no significant differences in this improvement by gender were found (see Fig. 5). The wait was considered in all linear mixed effects models and it did not influence QOL or FS.
Adjustments for the wait time and QOL component scores were applied to the linear mixed effects models as appropriate. Age and BMI were determined to be nonsignificant factors within all models.
60 50 40 Hip
30
Knee
20 10 0 12 months preoperative
1 month preoperative
12 months postoperative
Three Time Points
Fig. 3
Mean physical health scores over three time points compared by procedure.
Physical Component Summary Mean Scores
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60 50 40 Male 30
Female
20 10 0 12 months preoperative
1 month preoperative
12 months postoperative
Three Time Points
Fig. 4
Mean physical health scores over three time points compared by gender.
Discussion The patients in this study reported significant improvements in their QOL and FS over time. When the
datasets were further examined it was revealed that there were specific differences in QOL and FS based on procedure and gender at preoperative and postoperative time points. Generally speaking, THR
Table 5 Comparison of least squares mean physical and mental component summaries for Dataset Two by gender (N = 53). Gender/measure/time Male PCS 12 months prior to surgery 1 month prior to surgery 12 months after surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 month post Diff 1 month prior–12 months post Female PCS 12 months prior to surgery 1 month prior to surgery 12 months following surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 month post Diff 1 month prior–12 months post Male MCS 12 months prior to surgery 1 month prior to surgery 12 months after surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 month post Diff 1 month prior–12 months post Female MCS 12 months prior to surgery 1 month prior to surgery 12 months after surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 month post Diff 1 month prior–12 months post
Least squares Differences of least means squares means (p value). 29.3 ± 1.4 30.4 ± 1.3 45.6 ± 2.6
25.6 ± 1.4 25.2 ± 1.3 41.0 ± 2.6
47.6 ± 2.7 47.5 ± 2.6 54.6 ± 2.6
47.2 ± 2.7 48.8 ± 2.6 52.3 ± 2.4
−1.2 ± 1.2 (0.3396)* −16.4 ± 2.5 (<.0001)* −15.2 ± 2.5 (<.0001)*
0.4 ± 1.2 (.7357)* −15.4 ± 2.5 (<.0001)* −15.8 ± 2.4 (<.0001)*
0.1 ± 1.7 (.9536)** −7.0 ± 2.1 (.0230)** −7.1 ± 2.6 (.0083)**
−1.6 ± 1.7 (.3359)** −5.0 ± 3.0 (.0893)** −3.4 ± 2.7 (.1947)**
Note. Dataset Two: 12 months prior to surgery, 1 month prior to surgery, and 12 months following surgery; Oxford Hip/Knee was not collected at 12 months prior to surgery therefore no Oxford scores for Dataset Two; THR: total hip replacement; TKR: total knee replacement, PCS: physical component summary; MCS: mental component summary; Diff: difference between; male n = 26; female n = 27; * model adjusted by MCS; ** model adjusted by PCS.
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Mental Component Summary Mean Scores
60
50 Male Female 40
30 12 months preoperative
1 month preoperative
12 months postoperative
Three Time Points
Fig. 5
Mean mental health scores over three time points compared by gender.
patients andmale patients tended to report more favorable results than TKR patients and female patients. There are demographic similarities with for age, gender and BMI values the datasets used in this study and other databases such as the CIHI (2013) database. Current recommendations prescribe that nonurgent surgery should be performed within 26 weeks of specialist consultation (Wait Time Alliance, 2012). Although most current THR and TKR patients receive their surgery within the recommended guidelines (Manitoba Health, 2014), the average wait times in this study of 43 and 51 weeks in Dataset One and 60 and 65 weeks in Dataset Two (for THR and TKR patients, respectively) far exceeded this recommended waiting period. This study offered a unique perspective of changes in QOL and FS over time from when THR and TKR patients are placed on a waiting list and until one year postoperative. Compared to previous reports (de Beer et al., 2012; Garbuz et al., 2006; Ostendorf et al., 2004) our findings offer a more comprehensive and comparative analysis of health impact in both THR and TKR patients. Although QOL and FS scores did improve significantly, as predicted following surgery, our evidence shows that these improvements may differ by procedure and gender. Furthermore, QOL scores remained relatively stable between 12 months preoperative to one month preoperative, unlike the wait period declines reported elsewhere (Garbuz et al., 2006), supporting that it is not enough to know that the wait is nearly over to improve one’s emotional outlook. In order to better understand the impact of orthopedic patients’ health conditions it is helpful to examine how their QOL scores compare to normative values. Canadian normative scores for SF-36 PCS and SF-36 MCS are 46.8–47.6 and 53.4–54.0 respectively (Hopman et al., 2000). Since the SF-12 and SF36 are not identical instruments, these comparisons
should be made with caution. Secondly, and of major therapeutic importance, is whether clinically significant improvement occurred in QOL and FS health outcome measures. Norman et al. (2003), in their systematic review, reported that a minimally important difference in the change in health-related QOL can be estimated using half the standard deviation of the baseline score. In their systematic review of THR and TKR patients for the first six to 12 months after surgery, Browne et al. (2013) concluded that a minimally important difference of one standard error of the measurement is 2.7 for the OHS and 2.1 for the OKS. QOL scores in the current study showed important differences when compared to normative levels and both QOL and FS measures evidenced clinically important differences in scores between at least some time points. QOL, as measured by both PCS and MCS, was significantly below normal preoperatively, reflected little change from the early to immediate preoperative period and improved significantly by 12 months postoperatively. Despite clinically significant improvements, not all QOL health outcomes returned to normative levels for all patient groups by 12 months postoperative. Patients were often still below normative levels in their physical health scores, with TKR and female patients reporting worst PCS scores. de Beer et al. (2012) reported that THR patients had greater improvement clinically at one year following surgery. Choi et al. (2012) in their two year follow-up, agree that THR patients reported higher physical QOL scores in comparison to TKR patients. Ethgen et al. (2004) in their systematic review of 32 studies, report that males’ health related QOL seemed to improve more following their THR/TKR surgery than females. In the current study, significant improvements in mental health were reported by both THR and TKR patients although there was no difference between procedures. This contrasts with the
Longitudinal quality of life and functional status research performed by Choi et al. (2012) who found that MCS scores were higher for THR patients. Gender appeared to distinguish QOL mental health outcomes. Although both genders improved significantly over time, men reported higher mental health outcomes compared to females in the two time point dataset. In the significantly smaller three time point dataset only physical health was differentially improved for men compared to women. Female patients remained slightly below normative levels for mental health scores even 12 months postoperatively. This contrasts with Kostamo et al. (2009) who reported that female THR patients had greater improvement in their mental health scores compared to men. Functional status was based on data from the OHS and OKS results available only at two data points. Based on these measures, this study suggests that THR patients had poorer function preoperatively but more favorable functional outcomes postoperatively compared to TKR patients. Other researchers (Choi et al., 2012; de Beer et al., 2012; Wylde et al., 2009) found that THR patients reported better functional outcomes than TKR patients. Our study also determined that males reported higher FS than female patients, although females showed more improvement in FS scores. Females on average started with much poorer FS levels than males and improved, but to levels still poorer than men. In contrast, Liebs et al. (2011) concluded that although females had lower FS at the time of TKR surgery, they had greater improvements at three and six months. They also reported that at 12 months there were no functional differences between males and females. In the current study the length of the wait did not impact the patients’ reported QOL and FS. There is controversy in the literature as Ostendorf et al. (2004) agree but Garbuz et al. (2006) believe that longer waits for surgery decrease functional outcomes.
Clinical implications The change in the perceived level of QOL and FS across the perioperative period and up to one year postoperative for THR and TKR patients was the focus of this longitudinal study. This current study provides a more inclusive examination of QOL and FS both before and up to one year after THR/TKR surgery. Our findings demonstrated that patients’ physical and mental QOL remained clinically low but relatively stable during the wait period, and showed significant improvement 12 months following surgery. This study suggests that compared to the normal
111 population, most patients waiting for THR and TKR surgery are not only impaired functionally, but are also at risk in terms of their mental health. This mental health impairment is consistently low presurgery, low even when a surgical date is known and scheduled within the next month and continues to be lower than normal for women even 12 months following surgery. More positively, physical health and mental health components of QOL and FS do demonstrate improvement following surgery although the trajectory is somewhat different for THR and TKR patients and by gender. THR patients experience a greater improvement than TKR patients. Males rated their QOL and FS higher than female patients. All patients reported FS that reflected perceived difficulty although clinically significant positive changes were reported in all scores. In the larger dataset THR patients achieved greater mental health improvements and FS improvements than TKR patients. Further research is required to determine the specific nature of this positive association. Another area of concern would be to examine which interventions are appropriate to address the mental health needs of these THR and TKR patients. Does FS recovery in THR patients lead to greater improvement in mental health or vice versa? Bischoff-Ferrari et al. (2004) emphasized that mental health was linked to poor FS in their follow-up study of THR patients. Rolfson et al. (2009) agree that mental health issues can affect postoperative outcomes for THR patients. Likewise, Walton and Newman (2008) reported that patients who had lower mental health prior to surgery had worse outcomes at 2 years following TKR surgery. Mental health is an important factor that needs to be explored when discussing patient-reported physical health and postoperative outcomes following THR and TKR surgery (Perruccio et al., 2011). Male patients improved to a significantly higher level of physical health, mental health and FS than female patients although the amount of functional improvement was greater in female patients than the male patients. When the smaller dataset was studied male patients also reported a significantly higher level of physical health when compared to their female counterparts. This study begins to address the dearth of research exploring physical and mental components of QOL pre- and postoperatively in THR and TKR patients. The goals of joint replacement surgery include the significant reduction of pain and disability which in turn can lead to better QOL and FS. On average, and in keeping with clinical expectations, THR and TKR patients in this study showed significant improvements in their physical health and mental health
112 over time from one month prior to surgery to 12 months following surgery.
L.L. Mandzuk et al.
Ethical Approval The study received institutional and regional ethical approval.
Conclusions THR and TKR are some of the most common surgeries performed in Canada and typically lead to enhanced QOL and FS for patients (CIHI, 2013). The patients in this study tended to report improvements in their physical QOL, mental QOL and FS over time although differences by procedure and by gender were noted. Across the measurement time points, THR patients tended to demonstrate a greater amount of improvement than TKR patients. Males demonstrated higher levels of physical QOL, mental QOL, and FS when compared to females. However, even though the males had higher functional levels, the females had greater functional improvement when compared to the males. Although lower than normative physical QOL scores can be expected for individuals with conditions severe enough to necessitate surgery, the findings related to significantly impaired mental health QOL point to a serious additional health burden and risk. The consistently lower mental health scores found here at both data points prior to surgery for both THR and TKR patients and the continued lower than normative scores for women even 12 months following surgery, identify a potential area for clinical intervention. This study revealed insights into the trajectory of QOL components and FS across a fairly broad perioperative window from the time that the patient was placed on the waiting list and until one year postoperative. More work is needed to fully understand why recovery in these domains differs by procedure and gender and to target effective interventions that will put the quality back into patient quality of life, during the wait period and postoperatively.
Conflict of Interest Statement There are no conflicts of interest for the authors of this manuscript.
Funding Source The study was funded by an Alexander Gibson Orthopaedic Fund and a Health Outcomes Research Grant, Manitoba Centre for Nursing and Health Research, University of Manitoba without any influences on the project or article.
Acknowledgments Special thanks to the Winnipeg Regional Health Authority for supporting access to the database; to Tara Sawchuk for assistance with data extraction; and to Brenden Dufault BSc, MSc, Statistician at the Manitoba Centre for Nursing and Health Research at the Faculty of Nursing, University of Manitoba for his assistance with the statistical analysis.
References Berra, K., 2003. The effect of lifestyle interventions on quality of life and patient satisfaction with health and health care. Journal of Cardiovascular Nursing 18 (4), 319–325. Bischoff-Ferrari, H.A., Lingard, E.A., Losina, E., Baron, J.A., Roos, E.M., Phillips, C.B., et al., 2004. Psychosocial and geriatric correlates of functional status after total hip replacement. Arthritis & Rheumatism (Arthritis Care & Research) 51 (5), 829– 835. Browne, J.P., Bastaki, H., Dawson, J., 2013. What is the optimal time point to assess patient-reported recovery after hip and knee replacement? A systematic review and analysis of routinely reported outcome data from the English patientreported outcome measures programme. Health and Quality of Life Outcomes 11, 128. Canadian Institute for Health Information (CIHI), 2013. Hip and knee replacements in Canada: Canadian Joint Replacement Registry 2013 Annual Report. Retrieved on February 18, 2014 from. Canadian Orthopaedic Foundation, 2010. FAQ for total joint replacements. Retrieved on July 2, 2014 from . Choi, J.K., Geller, J.A., Yoon, R.S., Wang, W., Macaulay, W., 2012. Comparison of total hip and knee arthroplasty cohorts and short-term outcomes from a single-center joint registry. The Journal of Arthroplasty 27 (6), 837–841. de Beer, J., Petruccelli, D., Adili, A., Piccirillo, L., Wismer, D., Winemaker, M., 2012. Patient perspective survey of total hip vs total knee arthroplasty surgery. The Journal of Arthoplasty 27 (6), 865–869, e5. Dawson, J., Fitzpatrick, R., Carr, A., Murray, D., 1996. Questionnaire on the perceptions of patients about total hip replacement. Journal of Bone and Joint Surgery (British Volume) 78-B, 185–190. Dawson, J., Fitzpatrick, R., Murray, D., Carr, A., 1998. Questionnaire on the perceptions of patients about total knee replacement. Journal of Bone and Joint Surgery (British Volume) 80-B, 63–69. Ethgen, O., Bruyère, O., Richy, F., Dardennes, C., Reginster, J.-Y., 2004. Health-related quality of life in total hip and total knee arthroplasty. The Journal of Bone and Joint Surgery 86-A (5), 963–974.
Longitudinal quality of life and functional status Ferrans, C.E., Powers, M.J., 1992. Psychometric assessment of the quality of life index. Research in Nursing and Health 15, 29–38. Garbuz, D.S., Xu, M., Duncan, C.P., Masri, B.A., Sobolev, B., 2006. Delays worsen quality of life outcome of primary total hip arthroplasty. Clinical Orthopaedics and Related Research 447, 79–84. Goodridge, D., Trepman, E., Embil, J.M., 2005. Health-related quality of life in diabetic patients with foot ulcers: literature review. The Journal of Wound, Ostomy and Continence Nursing 32 (6), 368–377. Hopman, W.M., Towheed, T., Anastassiades, T., Tenenhouse, A., Poliquin, S., Berger, C., et al., 2000. Canadian normative data for the SF-36 health survey. Canadian Medical Association Journal 163 (3), 265–271. Kostamo, T., Bourne, R.B., Whittaker, J.P., McCalden, R.W., MacDonald, S.J., 2009. No difference in gender-specific hip replacement outcomes. Clinical Orthopaedics Related Research 467, 135–140. Liebs, T.R., Herzberg, W., Roth-Kroeger, A.M., Rüther, W., Hassenpflug, J., 2011. Women recover faster than men after standard knee arthroplasty. Clinical Orthopaedic Related Research 469, 2855–2865. Manitoba Health, 2014. Manitoba wait time information – total hip and total knee. Retrieved on March 29, 2014 from. McHugh, G.A., Luker, K.A., Campbell, M., Kay, P.R., Silman, A.J., 2008. Pain, physical functioning and quality of life of individuals awaiting total joint replacement: a longitudinal study. Journal of Evaluation in Clinical Practice 14, 19–26. Norman, G.R., Sloan, J.A., Wyrwich, K.W., 2003. Interpretation of changes in health-related quality of life: the remarkable universality of half a standard deviation. Medical Care 41 (5), 582–592. Ostendorf, M., Buskens, E., van Stel, H., Schrijvers, A., Marting, L., Dhert, W., et al., 2004. Waiting for total hip arthroplasty: avoidable loss in quality time and preventable deterioration. The Journal of Arthoplasty 19 (3), 302–309.
113 Patrick, D.L., Chiang, Y.-P., 2000. Measurement of health outcomes in treatment effectiveness evaluations: conceptua l and methodological challenges. Medical Care 38 (9 Suppl. II), II-14–II-25. Perruccio, A.V., Davis, A.M., Hogg-Johnson, S., Badley, E.M., 2011. Importance of self-rated health and mental well-being in predicting health outcomes following total joint replacement surgery for osteoarthritis. Arthritis Care & Research 63 (7), 973– 981. Quintana, J.M., Escobar, A., Aguirre, U., Lafuente, I., Arenaza, J.C., 2009. Predictors of health-related quality of life changes after total hip arthroplasty. Clinical Orthopaedic Related Research 467, 2886–2894. Rolfson, O., Dahlberg, L.E., Nilsson, J.-A., Malchau, H., Garellick, G., 2009. Variables determining outcome in total hip replacement surgery. The Journal of Bone and Joint Surgery (British Volume) 91-B, 157–161. Sprangers, M.A.G., Schwartz, C.E., 1999. Integrating response shift into health-related quality of life research: a theoretical model. Social Science & Medicine 48, 1507–1515. Wait Time Alliance, 2012. Shedding light on Canadians’ Total Wait for Care: report card on wait times in Canada. Retrieved on February 18, 2014 from. Walton, M.J., Newman, J.H., 2008. Preoperative mental wellbeing and the outcome of knee replacement. The Knee 15, 277–280. Wang, T.-J., 2004. Concept analysis of functional status. International Journal of Nursing Studies 41, 457–462. Ware, J.E., Kosinski, M., Keller, S.D., 1996. A 12-item shortform health survey: construction of scales and preliminary tests of reliability and validity. Medical Care 34 (3), 220– 233. Wylde, V., Blom, A.W., Whitehouse, S.L., Taylor, A.H., Pattison, G.T., Bannister, G.C., 2009. Patient-reported outcomes after total hip and knee arthroplasty. The Journal of Arthroplasty 24 (2), 210–215.
Available online at www.sciencedirect.com
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International Journal of Orthopaedic and Trauma Nursing www.elsevier.com/locate/ijotn
A longitudinal study of quality of life and functional status in total hip and total knee replacement patients Lynda L. Mandzuk RN, MN (Clinical Nurse Specialist) a,*, Diana E. McMillan RN, PhD (Associate Professor) b, Eric R. Bohm BEng, MD, MSc, FRCSC (Associate Professor) c a
Rehabilitation Geriatrics Program, St. Boniface Hospital, 409 Taché Avenue, Winnipeg, Manitoba, Canada, R2H 2A6 b College of Nursing, Faculty of Health Sciences, Helen Glass Centre, University of Manitoba, Winnipeg, Manitoba, Canada, R3T 2N2 c Concordia Joint Replacement Group, Department of Surgery, University of Manitoba, 1155 Concordia Avenue, Winnipeg, Manitoba, Canada, R2K 2M4
KEYWORDS Quality of life; Functional status; Total hip arthroplasty; Total knee arthroplasty
Abstract Background: Primary total hip and primary total knee surgeries are commonly performed to improve patients’ quality of life and functional status. Aim: This longitudinal retrospective study (N = 851) examined self-reported quality of life and functional status over the preoperative and postoperative periods: 12 months prior to surgery, one month prior to surgery and 12 months following surgery. Methods: A linear mixed effects model was used to analyze the changes in quality of life and functional status over the sampling period. Results: Patients in the convenience sample reported improvements in quality of life and functional status utilizing the SF-12 and Oxford Hip and Oxford Knee, although differences were noted by procedure and gender. Total hip patients tended to demonstrate greater improvement than total knee patients and males reported higher levels of physical and mental quality of life as well as functional status when compared to females. Of particular note was that mental health scores were consistently lower in both total hip and total knee replacement patients across the perioperative period and up to one year postoperative. Conclusion: This study identifies an opportunity for health care providers to proactively address the mental health of total hip and total knee replacement patients throughout their joint replacement trajectory. © 2014 Elsevier Ltd. All rights reserved.
* Corresponding author. E-mail address: [email protected] (L.L. Mandzuk). http://dx.doi.org/10.1016/j.ijotn.2014.07.001 1878-1241/© 2014 Elsevier Ltd. All rights reserved.
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Editor’s comment In a world constrained by available resources the outcomes of surgery are central to measuring success. Total hip and knee arthroplasties are focused on improving patients’ pain experience, their functional status and enhancing their quality of life. This important study adds to the growing body of evidence that demonstrates that although the outcomes of arthroplasty surgery vary between patients with different characteristics, there is a general improvement in both function and quality of life which makes the surgery worthwhile. Longitudinal research has the advantage of being able to provide a picture over time – taking a ‘snapshot’ at only one point in time is likely to be far less valuable. The longer term impact on mental health and well-being shown by this study is an important area for both further research and for practice development. JS-T
Introduction The two most prevalent primary joint replacement surgeries are total hip (THR) and total knee (TKR) replacements. In 2010–2011 these two surgeries accounted for 35,295 hospitalizations (Canadian Institute for Health Information (CIHI), 2013). Many patients experience lengthy preoperative waits. In the current study a wait was considered lengthy if it surpassed the recommended 26 weeks (Wait Time Alliance, 2012). The trend of a 13% increase in hospitalizations for total joint replacement surgeries in the past five years (CIHI, 2013) is expected to add to wait times.
Literature Two primary clinical aims associated with joint replacement surgery are to decrease pain and to decrease disability (Canadian Orthopaedic Foundation, 2010). For the purposes of this study, quality of life (QOL) and functional status (FS) were the related health status markers that were evaluated. QOL, in this study, is defined as the physical and mental wellbeing of the individual. Because QOL is multidimensional (Ferrans and Powers, 1992) and dynamic (Berra, 2003) it can mean “different things to different people” as well as “different things to the same person over a disease trajectory” (Sprangers and Schwartz, 1999, p. 1507). FS focuses on a balance between what the individual does and what the individual aspires to do (Wang, 2004). FS activities help the individual to achieve fundamental needs, roles and health. The domains of both QOL (Goodridge et al., 2005) and FS (Patrick and Chiang, 2000) are physical, psychological and social in nature. Given the often lengthy wait time experience and the significance of QOL and FS to individuals’
well-being it is important to examine QOL and FS across the care trajectory for THR and TKR patients. During the wait for joint replacement surgery QOL and FS are impaired (McHugh et al., 2008). With respect to procedure, some researchers (Choi et al., 2012; de Beer et al., 2012) report that THR patients have better FS postoperatively when compared to TKR patients. Health outcome differences by gender were also identified in the literature. In some studies, females tended to have less improvement in their QOL following THR surgery compared to males (Quintana et al., 2009). Others reported that females had more functional decline at the time of their TKR surgery but they gained FS at a faster rate and by 12 months postoperatively they had similar functional levels as males (Liebs et al., 2011). In terms of comparative longitudinal research, several studies explored the preoperative and postoperative phases. Ostendorf et al. (2004) evaluated both FS and QOL outcomes using the Oxford Hip Score (OHS), 36-Item Medical Outcomes Short Form (SF-36), EuroQOL Health Status and the Western Ontario McMaster Universities Osteoarthritis Index (WOMAC) instruments when THR patients were placed on the waiting list, prior to surgery and three and 12 months postoperative. Garbuz et al. (2006) also studied THR patients’ functional outcomes with the use of the WOMAC but only at the time of orthopedic consultation and one year following surgery. De Beer et al. (2012) focused on FS one year postoperatively utilizing the OHS and Oxford Knee Score (OKS) in THR and TKR patients respectively. This current study provides a more complete examination of QOL and FS during the preoperative and postoperative phases in both the THR and TKR populations. More importantly, this research addresses the scarcity of longitudinal inquiry providing insight into QOL and FS over time with consideration for procedure and gender.
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Methods This longitudinal study examined self-reported QOL and FS data for THR and TKR patients over time. Data were collected across the preoperative wait period and up to one year postoperative. Data were retrospective, having been collected previously and analyzed later. Patients had their surgery in urban community hospitals in a mid-western city in Canada between October 2004 and May 2007. A convenience sample of 851 patients who had waited for and then had surgery, either a primary THR or primary TKR, was included from the database following study institutional ethical approval. Participant inclusion criteria were as follows: (1a) either a primary THR or primary TKR was proposed; (1b) either a primary THR or primary TKR surgery was performed; (2) understood verbal and written English; (3) cognitively capable of completing the instruments and (4) anonymized data were accessible from a joint replacement registry. General health-related QOL was measured using the 12-Item Medical Outcomes Short Form (SF-12) (Ware et al., 1996). The SF-12 yields physical (PCS) and mental (MCS) component summaries with total scores of 0–100 for each. Lower scores indicated lower QOL. Functional status was assessed using the OHS (Dawson et al., 1996) and the OKS (Dawson et al., 1998). Total scores range from 12 to 60 with lower scores indicating less perceived disability with functional ability. The tools focus on the physical, psychological and social aspects of FS while concentrating on pain, function, and activity. While the OHS and OKS are similar in format, scoring and total score ranges, there are six items that differ making the measures comparable but not identical. The study involved three approximate measurement points: 12 months prior to surgery (waitlist), one month prior to surgery (preoperative) and 12 months following surgery (postoperative). To ensure that measurement points closely reflected the target measurement points and that there was sufficient opportunity for clinical change to occur a measurement point criteria was used; scores that were compared had a minimum of six months in between them. Using the Statistical Package for the Social Sciences (Version 15.0), two approaches were used to explore the QOL and FS data related to time, procedure and gender. In Dataset One, the relationship of QOL and FS was examined using the 1 month preoperative to 12 months postoperative data points. All possible patients in the analysis who met the measurement point criteria were included [N = 798; 92/ 890 patients excluded because of short (<6 months)
L.L. Mandzuk et al. data window]. In Dataset Two, the relationship of QOL over three target measurement points was explored: 12 months preoperative, 1 month preoperative and 12 months postoperative. This approach was limited to patients in the sample who met the criteria for all three measurement points [N = 53; 49/ 102 patients excluded because of short (<6 month) data window]. A linear mixed effects model was used to analyze the changes in QOL and FS over the sampling periods. In a repeated measures context, this approach allows valid inferences to be made comparing procedures at all time points by accounting for the correlation between multiple observations made on the same subject. Repeated measures mixed effects models are analogous to repeated measures analysis of variance (ANOVA) except that the former are more flexible since they can directly model the covariance structure instead of imposing the assumption of compound symmetry. Also, they handle missing data better as ANOVA eliminates subjects that have any missing data, whereas a mixed effects model will keep all the information in the dataset. Statistical significance was set at p ≤ .05. (B. Dufault, personal communication, April 29, 2010).
Results Adjustments for the wait time and QOL component scores were applied to the mixed effects models as appropriate; age and body mass index (BMI) were determined to be nonsignificant factors within all models.
Dataset One: QOL and FS in the preoperative to postoperative period Dataset One (N = 798) was composed of 45.1% males and 54.9% females. THR surgery was performed on 43.6% of the patients while 56.4% of patients had TKR surgery. Hip surgery patients were on average both younger and lighter (64.8 ± 12.3 years; BMI 28.8 ± 5.3 kg/m2) than those undergoing TKR surgery (67.3 ± 10.3 years; BMI 31.9 ± 6.7 kg/m2). These differences were significant (p = .0024 and p < .0001, respectively). In terms of wait time, TKR patients waited on average longer than THR patients (43.0 ± 29.1 weeks vs 50.6 ± 31.5 weeks, p = .0005) (see Table 1). Using the mixed effects model it was determined that there was a significant improvement in QOL with respect to the PCS for both THR (27.9 ± .5 vs 42.6 ± .5) and TKR (29.2 ± .5 vs 40.2 ± .5) patients from the preoperative to postoperative period,
Longitudinal quality of life and functional status Table 1
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Demographics for Dataset One and Dataset Two by procedure
Variables
Dataset One (N = 798)
Dataset Two (N = 53)
Total hip
Total knee
Total hip
Total knee
Procedure n (%) Gender n (%) Male Female Age (years) Mean (SD) Range BMI (kg/m2) Mean (SD) Range Wait (weeks) Mean (SD) Range
348 (43.6%)
450 (56.4%)
28 (52.8%)
25 (47.2%)
177 (50.4%) 171 (49.1%)
183 (40.7%) 267(59.3%)
15 (53.6%) 13 (46.4%)
11 (44.0%) 14 (56.0%)
64.8 (12.3) 18–92
67.3 (10.3) 32–91
61.1 (10.3) 41–79
68.52 (11.0) 49–87
28.8 (5.3) 17.5–49.0
31.9 (6.7) 16.1–60.7
30.1 (5.0) 20.7–43.0
31.74 (5.6) 23.2–47.0
43.0 (29.1) 3–162
50.6 (31.5) 0–143
59.7 (11.8) 35–84
65.08 (14.8) 44–103
Note. Dataset One: 1 month prior to surgery and 12 months following surgery and Dataset Two: 12 months prior to surgery, 1 month prior to surgery, and 12 months following surgery.
respectively, (p < .0001) (see Table 2). However, there was no significant between group difference in this regard (see Fig. 1). The PCS scores improved significantly preoperatively to postoperatively
(p < .0001) for both males (30.1 ± .5 vs 43.1 ± .5) and females (27.4 ± .5 vs 39.7 ± .5) with males reporting higher mean scores at both time points (p < .0001).
Table 2 Comparison of least squares mean physical and mental component summaries and least squares mean Oxford Hip/Knee Scores for Dataset One by procedure (N = 798) Procedure/measure/time THR PCS 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post TKR PCS 1 month prior to surgery 12 months following surgery Diff 1 month prior–12 months post THR MCS 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post TKR MCS 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post THR Oxfordo 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post TKR Oxfordo 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post
Least squares Differences of least means squares means (p value) 27.9 ± .5 42.6 ± .5 29.2 ± .5 40.2 ± .5 49.2 ± .7 54.4 ± .6 51.5 ± .6 53.4 ± .5 42.5 ± .4 19.6 ± .5 40.4 ± .4 23.8 ± .4
−14.8 ± .6 (<.0001)
−10.1 ± .5 (<.0001)
−5.1 ± .7 (<.0001)*
−1.9 ± .6 (.0018)*
22.9 ± .6 (<.0001)**
16.6 ± .5 (<.0001)**
Note. Dataset One: 1 month prior to surgery and 12 months following surgery; THR: total hip replacement; TKR: total knee replacement, PCS: physical component summary; MCS: mental component summary; Oxford: Oxford Hip/Knee Score; Diff: difference between; THR n = 348; TKR n = 450; * model adjusted by PCS, ** model adjusted by length of wait; o missing data for Oxford scores 1 month prior to surgery = 97 and 12 months after surgery = 66.
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Physical Component Summary Mean Scores
60 50 40 Hip
30
Knee
20 10 0 1 month preoperative
12 months postoperative
Two Time Points
Fig. 1
Mean physical health scores over two time points compared by procedure.
Similarly, there was a significant improvement in QOL with respect to the MCS scores preoperatively to postoperatively for both THR (49.2 ± .7 vs 54.4 ± .6; p < .0001) and TKR patients (51.5 ± .6 vs 53.4 ± .5; p = .0018). While there was no between group difference for MCS scores, the MCS scores for THR patients indicated significantly faster improvement than patients receiving TKR surgery (p < .0001). Significant improvement in MCS scores was also seen preoperatively to postoperatively in both males (51.8 ± .6 vs 54.4 ± .6; p = .0002) and females (49.6 ± .6 vs 53.2 ± .5; p < .0001) although a comparison of the improvements in MCS was not significantly different between males and females. In terms of functional status, a significant change was seen in the Oxford-12 scores by time (p < .0001) and by procedure (p = .0311). There was a significant improvement in the FS scores between the two time points and THR patients (42.5 ± .4 vs 19.6 ± .5) had higher levels of FS at 12 months postoperatively than TKR patients (40.4 ± .4 vs 23.8 ± .4). There was
also a significant interaction between procedure and time, indicating that THR patients improved in their FS at a greater rate than TKR patients. THR patients had on average a poorer FS score preoperatively and a better FS score postoperatively (p < .0001) (see Fig. 2). It is important to remember that while the OHS and OKS are similar, they are not identical tools as they are joint-specific. Both males and females showed significant improvement in FS scores preoperatively to postoperatively (p < .0001) (see Table 3). Males reported significantly better FS scores both preoperatively and postoperatively (39.4 ± .4 and 20.8 ± .5, p < .0001) compared to females (43.1 ± .4 and 22.9 ± .5, p < .0001). However, there was a significant interaction between gender and time (p = .0428) with a greater amount of improvement in the FS of females than males. Females had on average a much poorer FS preoperatively and, while they improved significantly, the females continued to have poorer FS postoperatively when compared to males.
Oxford Mean Scores
60 50 40 Hip
30
Knee
20 10 0 1 month preoperative
12 months postoperative Two Time Points
Fig. 2
Mean functional status scores over two time points compared by procedure.
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Table 3 Comparison of least squares mean physical and mental component summaries and least squares mean Oxford Hip/Knee Scores for Dataset One by gender (N = 798). Gender/measure/time Male PCS 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post Female PCS 1 month prior to surgery 12 months following surgery Diff 1 month prior–12 months post Male MCS 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post Female MCS 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post Male Oxfordo 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post Female Oxfordo 1 month prior to surgery 12 months after surgery Diff 1 month prior–12 months post
Least squares Differences of least means squares means (p value) 30.1 ± .5 43.1 ± .5 27.4 ± .5 39.7 ± .5 51.8 ± .6 54.4 ± .6 49.6 ± .6 53.2 ± .5 39.4 ± .4 20.8 ± .5 43.1 ± .4 22.9 ± .5
−12.9 ± .6 (<.0001)*
−12.3 ± .6 (<.0001)*
−2.6 ± .7 (.0002)**
−3.7 ± .6 (<.0001)**
18.6 ± .6 (<.0001)***
20.2 ± .5 (<.0001)***
Note. Dataset One: 1 month prior to surgery and 12 months following surgery; THR: total hip replacement; TKR: total knee replacement, PCS: physical component summary; MCS: mental component summary; Oxford: Oxford Hip/Knee Score; Diff: difference between; male n = 360; female n = 438; * model adjusted by MCS; ** model adjusted by PCS; *** model adjusted by length of wait; o missing data for Oxford scores 1 month prior to surgery = 97 and 12 months after surgery = 66.
Dataset Two: QOL in the waitlist to preoperative to postoperative periods Dataset Two measured QOL for patients at three measurement points (N = 53). With respect to this smaller second dataset, the demographic characteristics were similar to the larger dataset with the exception that the smaller dataset had a longer mean wait time (see Table 1). The average wait time in weeks was 59.7 ± 11.8 for THR surgery and 65.1 ± 14.8 for TKR surgery. Within Dataset Two the TKR patients waited on average six more weeks than the THR patients, but this difference was not statistically significant. Based on the three measurement point data (i.e., 12 months preoperative, 1 month preoperative, 12 months postoperative) there was significant improvement in physical health as measured by PCS scores, over time (p < .0001) for THR and TKR patients (see Table 4 for specific time point differences). This significant improvement in the physical component of QOL was almost exclusively attributed to the change seen 1 month preoperatively to postoperatively (see
Fig. 3). Although the amount of change over measurement points was comparatively greater in THR patients, this difference between procedures was not significant (p = .0512). There were significant changes in physical health scores by time (p < .0001) and gender (p = .0276). Specifically, and similar to findings using the larger dataset, physical health scores improved significantly for both males and females with males reporting significantly higher physical health scores overall compared to females (see Fig. 4). Using the three point, mixed effects model analysis it was determined that there was a significant improvement in QOL mental health scores by time (p = .0199) (see Table 5). Specifically mental health, as measured by MCS scores, improved significantly over time for both THR and TKR patients, with the change primarily attributed again to the improvement 1 month preoperatively to postoperatively. There were no significant mean differences in MCS scores between THR and TKR patients nor in the rate of their improvement. Mental health scores did improve significantly over time (p = .0383) for both
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Table 4 Comparison of least squares mean physical and mental component summaries for Dataset Two by procedure (N = 53). Procedure/measure/time
Least squares means
THR PCS 12 months prior to surgery 1 month prior to surgery 12 months after surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 months post Diff 1 month prior–12 months post TKR PCS 12 months prior to surgery 1 month prior to surgery 12 months following surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 months post Diff 1 month prior–12 months post THR MCS 12 months prior to surgery 1 month prior to surgery 12 months after surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 months post Diff 1 month prior–12 months post TKR MCS 12 months prior to surgery 1 month prior to surgery 12 months after surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 months post Diff 1 month prior–12 months post
27.2 ± 1.4 28.1 ± 1.4 47.1 ± 2.5
27.6 ± 1.5 27.3 ± 1.4 39.1 ± 2.6
45.4 ± 2.6 46.1 ± 2.5 54.6 ± 2.7
49.2 ± 2.8 50.1 ± 2.6 53.1 ± 2.5
Differences of least squares means (p value)
−0.9 ± 1.1 (.4282)* −19.9 ± 2.3 (<.0001)* −19.0 ± 2.3 (<.0001)*
−0.2 ± 1.2 (.8591)* −11.5 ± 2.4 (<.0001)* −11.7 ± 2.4 (<.0001)*
−0.7 ± 1.6 (.6754)** −9.2 ± 3.1 (.0035)** −8.5 ± 2.7 (.0024)**
−.9 ± 1.7 (.6018)** −3.9 ± 2.8 (.1755)** −3.0 ± 2.5 (.2325)**
Note. Dataset Two: 12 months prior to surgery, 1 month prior to surgery, and 12 months following surgery; Oxford Hip/Knee was not collected at 12 months prior to surgery therefore no Oxford scores for Dataset Two; THR: total hip replacement; TKR: total knee replacement, PCS: physical component summary; MCS: mental component summary; Diff: difference between; THR n = 28; TKR n = 25; * model adjusted by PCS; ** model adjusted by MCS.
Physical Component Summary Mean Scores
males and females and no significant differences in this improvement by gender were found (see Fig. 5). The wait was considered in all linear mixed effects models and it did not influence QOL or FS.
Adjustments for the wait time and QOL component scores were applied to the linear mixed effects models as appropriate. Age and BMI were determined to be nonsignificant factors within all models.
60 50 40 Hip
30
Knee
20 10 0 12 months preoperative
1 month preoperative
12 months postoperative
Three Time Points
Fig. 3
Mean physical health scores over three time points compared by procedure.
Physical Component Summary Mean Scores
Longitudinal quality of life and functional status
109
60 50 40 Male 30
Female
20 10 0 12 months preoperative
1 month preoperative
12 months postoperative
Three Time Points
Fig. 4
Mean physical health scores over three time points compared by gender.
Discussion The patients in this study reported significant improvements in their QOL and FS over time. When the
datasets were further examined it was revealed that there were specific differences in QOL and FS based on procedure and gender at preoperative and postoperative time points. Generally speaking, THR
Table 5 Comparison of least squares mean physical and mental component summaries for Dataset Two by gender (N = 53). Gender/measure/time Male PCS 12 months prior to surgery 1 month prior to surgery 12 months after surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 month post Diff 1 month prior–12 months post Female PCS 12 months prior to surgery 1 month prior to surgery 12 months following surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 month post Diff 1 month prior–12 months post Male MCS 12 months prior to surgery 1 month prior to surgery 12 months after surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 month post Diff 1 month prior–12 months post Female MCS 12 months prior to surgery 1 month prior to surgery 12 months after surgery Diff 12 months prior–1 month prior Diff 12 months prior–12 month post Diff 1 month prior–12 months post
Least squares Differences of least means squares means (p value). 29.3 ± 1.4 30.4 ± 1.3 45.6 ± 2.6
25.6 ± 1.4 25.2 ± 1.3 41.0 ± 2.6
47.6 ± 2.7 47.5 ± 2.6 54.6 ± 2.6
47.2 ± 2.7 48.8 ± 2.6 52.3 ± 2.4
−1.2 ± 1.2 (0.3396)* −16.4 ± 2.5 (<.0001)* −15.2 ± 2.5 (<.0001)*
0.4 ± 1.2 (.7357)* −15.4 ± 2.5 (<.0001)* −15.8 ± 2.4 (<.0001)*
0.1 ± 1.7 (.9536)** −7.0 ± 2.1 (.0230)** −7.1 ± 2.6 (.0083)**
−1.6 ± 1.7 (.3359)** −5.0 ± 3.0 (.0893)** −3.4 ± 2.7 (.1947)**
Note. Dataset Two: 12 months prior to surgery, 1 month prior to surgery, and 12 months following surgery; Oxford Hip/Knee was not collected at 12 months prior to surgery therefore no Oxford scores for Dataset Two; THR: total hip replacement; TKR: total knee replacement, PCS: physical component summary; MCS: mental component summary; Diff: difference between; male n = 26; female n = 27; * model adjusted by MCS; ** model adjusted by PCS.
110
L.L. Mandzuk et al.
Mental Component Summary Mean Scores
60
50 Male Female 40
30 12 months preoperative
1 month preoperative
12 months postoperative
Three Time Points
Fig. 5
Mean mental health scores over three time points compared by gender.
patients andmale patients tended to report more favorable results than TKR patients and female patients. There are demographic similarities with for age, gender and BMI values the datasets used in this study and other databases such as the CIHI (2013) database. Current recommendations prescribe that nonurgent surgery should be performed within 26 weeks of specialist consultation (Wait Time Alliance, 2012). Although most current THR and TKR patients receive their surgery within the recommended guidelines (Manitoba Health, 2014), the average wait times in this study of 43 and 51 weeks in Dataset One and 60 and 65 weeks in Dataset Two (for THR and TKR patients, respectively) far exceeded this recommended waiting period. This study offered a unique perspective of changes in QOL and FS over time from when THR and TKR patients are placed on a waiting list and until one year postoperative. Compared to previous reports (de Beer et al., 2012; Garbuz et al., 2006; Ostendorf et al., 2004) our findings offer a more comprehensive and comparative analysis of health impact in both THR and TKR patients. Although QOL and FS scores did improve significantly, as predicted following surgery, our evidence shows that these improvements may differ by procedure and gender. Furthermore, QOL scores remained relatively stable between 12 months preoperative to one month preoperative, unlike the wait period declines reported elsewhere (Garbuz et al., 2006), supporting that it is not enough to know that the wait is nearly over to improve one’s emotional outlook. In order to better understand the impact of orthopedic patients’ health conditions it is helpful to examine how their QOL scores compare to normative values. Canadian normative scores for SF-36 PCS and SF-36 MCS are 46.8–47.6 and 53.4–54.0 respectively (Hopman et al., 2000). Since the SF-12 and SF36 are not identical instruments, these comparisons
should be made with caution. Secondly, and of major therapeutic importance, is whether clinically significant improvement occurred in QOL and FS health outcome measures. Norman et al. (2003), in their systematic review, reported that a minimally important difference in the change in health-related QOL can be estimated using half the standard deviation of the baseline score. In their systematic review of THR and TKR patients for the first six to 12 months after surgery, Browne et al. (2013) concluded that a minimally important difference of one standard error of the measurement is 2.7 for the OHS and 2.1 for the OKS. QOL scores in the current study showed important differences when compared to normative levels and both QOL and FS measures evidenced clinically important differences in scores between at least some time points. QOL, as measured by both PCS and MCS, was significantly below normal preoperatively, reflected little change from the early to immediate preoperative period and improved significantly by 12 months postoperatively. Despite clinically significant improvements, not all QOL health outcomes returned to normative levels for all patient groups by 12 months postoperative. Patients were often still below normative levels in their physical health scores, with TKR and female patients reporting worst PCS scores. de Beer et al. (2012) reported that THR patients had greater improvement clinically at one year following surgery. Choi et al. (2012) in their two year follow-up, agree that THR patients reported higher physical QOL scores in comparison to TKR patients. Ethgen et al. (2004) in their systematic review of 32 studies, report that males’ health related QOL seemed to improve more following their THR/TKR surgery than females. In the current study, significant improvements in mental health were reported by both THR and TKR patients although there was no difference between procedures. This contrasts with the
Longitudinal quality of life and functional status research performed by Choi et al. (2012) who found that MCS scores were higher for THR patients. Gender appeared to distinguish QOL mental health outcomes. Although both genders improved significantly over time, men reported higher mental health outcomes compared to females in the two time point dataset. In the significantly smaller three time point dataset only physical health was differentially improved for men compared to women. Female patients remained slightly below normative levels for mental health scores even 12 months postoperatively. This contrasts with Kostamo et al. (2009) who reported that female THR patients had greater improvement in their mental health scores compared to men. Functional status was based on data from the OHS and OKS results available only at two data points. Based on these measures, this study suggests that THR patients had poorer function preoperatively but more favorable functional outcomes postoperatively compared to TKR patients. Other researchers (Choi et al., 2012; de Beer et al., 2012; Wylde et al., 2009) found that THR patients reported better functional outcomes than TKR patients. Our study also determined that males reported higher FS than female patients, although females showed more improvement in FS scores. Females on average started with much poorer FS levels than males and improved, but to levels still poorer than men. In contrast, Liebs et al. (2011) concluded that although females had lower FS at the time of TKR surgery, they had greater improvements at three and six months. They also reported that at 12 months there were no functional differences between males and females. In the current study the length of the wait did not impact the patients’ reported QOL and FS. There is controversy in the literature as Ostendorf et al. (2004) agree but Garbuz et al. (2006) believe that longer waits for surgery decrease functional outcomes.
Clinical implications The change in the perceived level of QOL and FS across the perioperative period and up to one year postoperative for THR and TKR patients was the focus of this longitudinal study. This current study provides a more inclusive examination of QOL and FS both before and up to one year after THR/TKR surgery. Our findings demonstrated that patients’ physical and mental QOL remained clinically low but relatively stable during the wait period, and showed significant improvement 12 months following surgery. This study suggests that compared to the normal
111 population, most patients waiting for THR and TKR surgery are not only impaired functionally, but are also at risk in terms of their mental health. This mental health impairment is consistently low presurgery, low even when a surgical date is known and scheduled within the next month and continues to be lower than normal for women even 12 months following surgery. More positively, physical health and mental health components of QOL and FS do demonstrate improvement following surgery although the trajectory is somewhat different for THR and TKR patients and by gender. THR patients experience a greater improvement than TKR patients. Males rated their QOL and FS higher than female patients. All patients reported FS that reflected perceived difficulty although clinically significant positive changes were reported in all scores. In the larger dataset THR patients achieved greater mental health improvements and FS improvements than TKR patients. Further research is required to determine the specific nature of this positive association. Another area of concern would be to examine which interventions are appropriate to address the mental health needs of these THR and TKR patients. Does FS recovery in THR patients lead to greater improvement in mental health or vice versa? Bischoff-Ferrari et al. (2004) emphasized that mental health was linked to poor FS in their follow-up study of THR patients. Rolfson et al. (2009) agree that mental health issues can affect postoperative outcomes for THR patients. Likewise, Walton and Newman (2008) reported that patients who had lower mental health prior to surgery had worse outcomes at 2 years following TKR surgery. Mental health is an important factor that needs to be explored when discussing patient-reported physical health and postoperative outcomes following THR and TKR surgery (Perruccio et al., 2011). Male patients improved to a significantly higher level of physical health, mental health and FS than female patients although the amount of functional improvement was greater in female patients than the male patients. When the smaller dataset was studied male patients also reported a significantly higher level of physical health when compared to their female counterparts. This study begins to address the dearth of research exploring physical and mental components of QOL pre- and postoperatively in THR and TKR patients. The goals of joint replacement surgery include the significant reduction of pain and disability which in turn can lead to better QOL and FS. On average, and in keeping with clinical expectations, THR and TKR patients in this study showed significant improvements in their physical health and mental health
112 over time from one month prior to surgery to 12 months following surgery.
L.L. Mandzuk et al.
Ethical Approval The study received institutional and regional ethical approval.
Conclusions THR and TKR are some of the most common surgeries performed in Canada and typically lead to enhanced QOL and FS for patients (CIHI, 2013). The patients in this study tended to report improvements in their physical QOL, mental QOL and FS over time although differences by procedure and by gender were noted. Across the measurement time points, THR patients tended to demonstrate a greater amount of improvement than TKR patients. Males demonstrated higher levels of physical QOL, mental QOL, and FS when compared to females. However, even though the males had higher functional levels, the females had greater functional improvement when compared to the males. Although lower than normative physical QOL scores can be expected for individuals with conditions severe enough to necessitate surgery, the findings related to significantly impaired mental health QOL point to a serious additional health burden and risk. The consistently lower mental health scores found here at both data points prior to surgery for both THR and TKR patients and the continued lower than normative scores for women even 12 months following surgery, identify a potential area for clinical intervention. This study revealed insights into the trajectory of QOL components and FS across a fairly broad perioperative window from the time that the patient was placed on the waiting list and until one year postoperative. More work is needed to fully understand why recovery in these domains differs by procedure and gender and to target effective interventions that will put the quality back into patient quality of life, during the wait period and postoperatively.
Conflict of Interest Statement There are no conflicts of interest for the authors of this manuscript.
Funding Source The study was funded by an Alexander Gibson Orthopaedic Fund and a Health Outcomes Research Grant, Manitoba Centre for Nursing and Health Research, University of Manitoba without any influences on the project or article.
Acknowledgments Special thanks to the Winnipeg Regional Health Authority for supporting access to the database; to Tara Sawchuk for assistance with data extraction; and to Brenden Dufault BSc, MSc, Statistician at the Manitoba Centre for Nursing and Health Research at the Faculty of Nursing, University of Manitoba for his assistance with the statistical analysis.
References Berra, K., 2003. The effect of lifestyle interventions on quality of life and patient satisfaction with health and health care. Journal of Cardiovascular Nursing 18 (4), 319–325. Bischoff-Ferrari, H.A., Lingard, E.A., Losina, E., Baron, J.A., Roos, E.M., Phillips, C.B., et al., 2004. Psychosocial and geriatric correlates of functional status after total hip replacement. Arthritis & Rheumatism (Arthritis Care & Research) 51 (5), 829– 835. Browne, J.P., Bastaki, H., Dawson, J., 2013. What is the optimal time point to assess patient-reported recovery after hip and knee replacement? A systematic review and analysis of routinely reported outcome data from the English patientreported outcome measures programme. Health and Quality of Life Outcomes 11, 128. Canadian Institute for Health Information (CIHI), 2013. Hip and knee replacements in Canada: Canadian Joint Replacement Registry 2013 Annual Report. Retrieved on February 18, 2014 from
Longitudinal quality of life and functional status Ferrans, C.E., Powers, M.J., 1992. Psychometric assessment of the quality of life index. Research in Nursing and Health 15, 29–38. Garbuz, D.S., Xu, M., Duncan, C.P., Masri, B.A., Sobolev, B., 2006. Delays worsen quality of life outcome of primary total hip arthroplasty. Clinical Orthopaedics and Related Research 447, 79–84. Goodridge, D., Trepman, E., Embil, J.M., 2005. Health-related quality of life in diabetic patients with foot ulcers: literature review. The Journal of Wound, Ostomy and Continence Nursing 32 (6), 368–377. Hopman, W.M., Towheed, T., Anastassiades, T., Tenenhouse, A., Poliquin, S., Berger, C., et al., 2000. Canadian normative data for the SF-36 health survey. Canadian Medical Association Journal 163 (3), 265–271. Kostamo, T., Bourne, R.B., Whittaker, J.P., McCalden, R.W., MacDonald, S.J., 2009. No difference in gender-specific hip replacement outcomes. Clinical Orthopaedics Related Research 467, 135–140. Liebs, T.R., Herzberg, W., Roth-Kroeger, A.M., Rüther, W., Hassenpflug, J., 2011. Women recover faster than men after standard knee arthroplasty. Clinical Orthopaedic Related Research 469, 2855–2865. Manitoba Health, 2014. Manitoba wait time information – total hip and total knee. Retrieved on March 29, 2014 from
113 Patrick, D.L., Chiang, Y.-P., 2000. Measurement of health outcomes in treatment effectiveness evaluations: conceptua l and methodological challenges. Medical Care 38 (9 Suppl. II), II-14–II-25. Perruccio, A.V., Davis, A.M., Hogg-Johnson, S., Badley, E.M., 2011. Importance of self-rated health and mental well-being in predicting health outcomes following total joint replacement surgery for osteoarthritis. Arthritis Care & Research 63 (7), 973– 981. Quintana, J.M., Escobar, A., Aguirre, U., Lafuente, I., Arenaza, J.C., 2009. Predictors of health-related quality of life changes after total hip arthroplasty. Clinical Orthopaedic Related Research 467, 2886–2894. Rolfson, O., Dahlberg, L.E., Nilsson, J.-A., Malchau, H., Garellick, G., 2009. Variables determining outcome in total hip replacement surgery. The Journal of Bone and Joint Surgery (British Volume) 91-B, 157–161. Sprangers, M.A.G., Schwartz, C.E., 1999. Integrating response shift into health-related quality of life research: a theoretical model. Social Science & Medicine 48, 1507–1515. Wait Time Alliance, 2012. Shedding light on Canadians’ Total Wait for Care: report card on wait times in Canada. Retrieved on February 18, 2014 from
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