The impact of self-efficacy for physical activity on health-related quality of life in total knee arthroplasty recipients

Abstract

BACKGROUND:

Some patients with end-stage osteoarthritis of the knee remain unsatisfied after total knee arthroplasty (TKA). We postulated that to increase satisfaction, self-efficacy (SE) for physical activity should receive more attention in rehabilitative intervention, alongside the management of patient expectations, pain, and function.

OBJECTIVE:

We examined the relative impact of Physical Activity SE on Health-Related Quality of Life (HRQOL) alongside other factors such as pain and physical function which are well-addressed by current interventions.

METHODS:

One hundred and six first-TKA recipients (15 Male/91 Female, age 73.6 $\pm$ 7.2) were evaluated at 3 and 6 months post-operatively using the Medical Outcomes Study 36-Item Health Survey (SF-36v2) for HRQOL, knee extension strength measurement, Timed Up and Go test (TUG), One Leg Standing time test (OLS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) for pain and function, and an instrument for measuring Physical Activity SE among the frail elderly in Japan.

RESULTS:

Significant improvement over pre-operative values was found at 3 and 6 months in TUG, OLS, WOMAC Pain and Function, and the 8 subscales of the SF-36v2. Factors found to significantly impact SF-36v2 subscale scores at 6 months post-operatively were found to be knee pain, knee function, and SE for physical activity.

CONCLUSION:

These results support our postulation that interventions to improve SE for physical activity could have comparable impact alongside interventions for knee pain and knee function, on the advancement of HRQOL among TKA recipients.

Keywords

Total knee arthroplasty Health-Related Quality of Life self-efficacy physical function rehabilitation

1. Introduction

In Japan, total knee arthroplasty (TKA) for end-stage osteoarthritis of the knee (knee OA) is increasing yearly and has reached 95,000/yr [1]. TKA is established as an effective treatment for the resolution of pain and recovery of physical function. However, patient satisfaction among TKA recipients remains at around 80% [2]. Dunbar et al. reported on the top risk factors for TKA recipient dissatisfaction and concluded that post-operative interventions to reduce dissatisfaction “should focus on expectations, pain, and function” [3]. Now, we postulated that after the best efforts have been made to manage pre-operative expectations, interventions to maximize postoperative satisfaction should focus not only on improvements in pain and function, but also on self-efficacy (SE) expectations for activity and participation relevant to the comprehensive improvement of Health-Related Quality of Life (HRQOL).

Using the Medical Outcomes Study Short-Form 36-Item Health Survey Standard Form v2 (SF-36v2) as an established comprehensive index of HRQOL, we previously reported improvements in subscale scores over preoperative scores at one month post-TKA that were maintained at 3 months [4]. Striking improvements in the HRQOL of TKA recipients at 3 and 6 months have been reported elsewhere [5]. However, in Japan, to our knowledge the HRQOL of TKA recipients beyond 3 months post-op, as measured using SF-36v2, has not been reported.

Physical activity SE has gained attention as a factor in the improvement of HRQOL. SE expectation is defined by Bandura as the personal conviction regarding one’s level of ability to perform the actions necessary to produce specific results [6]. Specifically, SE for exercise and SE for physical activity are said to be related to behavioral change, physical activity, continuation of exercise [7], and also HRQOL [8]. For the improvement of HRQOL in TKA recipients, Physical Activity SE is an important factor as a parameter. However, to our knowledge there are no reports focusing on physical activity SE in TKA recipients, and no studies of interventions to improve it, presumably because the influence of physical activity SE on HRQOL has not been clarified.

We hypothesized that interventions not only for pain and physical function, but also for the improvement of psychological factors such as SE for Physical Activity, would bring gains over the current levels of HRQOL and satisfaction in TKA recipients. However, verification of factors impacting the HRQOL of TKA recipients is a critical prerequisite to the ascertainment of prognoses with any intervention under consideration. For this reason, this single site prospective cohort study was designed to examine the relative importance of physical activity SE alongside other known factors impacting the postoperative recovery of HRQOL after TKA.

2. Participants and methods

2.1 Participants

Participants were selected from 320 first-time recipients of unilateral TKA for end-stage knee OA at our institution from August 2009 to July 2018. Patients with cognitive disabilities preventing proper responses on questionnaires, and patients with neurological or other conditions that can impact walking ability and those with other difficulties getting to the outpatient clinic for follow up were excluded from the study such that 106 recipients remained who could be followed for six months. Participants included 15 males and 91 females average age 73.6 $\pm$ 7.2 (Table 1). For ethical considerations, signed consent to participate was obtained after the study content was conveyed verbally and using explanatory text. This study was conducted with the approval of the Dokkyo Medical University Saitama Medical Center Bioethics Committee (0826).

Table 1
Preoperative characteristics

Age (y)	73.6 $\pm$ 7.2
Gender (m/f)	15/91
Height (cm)	151.3 $\pm$ 7.4
Weight (kg)	60.4 $\pm$ 11.0
Body Mass Index (kg/m ${}^{2}$ )	26.3 $\pm$ 4.2
Post-op hospital days (d)	24.7 $\pm$ 6.5

2.2 Methods

1)
Knee extension strength was measured using the Biodex system 3 (Biodex Medical Systems, USA). Measurements were made with patients seated and using a series of 5 isokinetic contractions and an angular velocity of 60 ${}^{\circ}$ /sec.
2)
The Timed Up and Go test (TUG) was conducted according to the method described by Podsiadlo et al. [9]. To minimize variation caused by psychological state and interpretation of instructions the Japanese equivalent of “do it as fast as you can” was used consistently. The test was conducted twice and the faster of the two values used as the representative value.
3)
The One Leg Standing time test (OLS) was conducted as described by Takahashi et al. [10]. With the operated side barefoot and both hands placed on the hips, the time until the raised foot touched the floor was measured for each of 3 performances, and the maximum value was then used as the representative value.
4)
For the evaluation of knee joint pain and function a Japanese translation of Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) [11] was used and is hereafter referred to as WOMAC-J. Self-reported, with 100 points possible, the higher scores indicate better knee joint function and lower pain.
5)
For the measurement of SE expectations, Inaba’s Rating Scale for Self-Efficacy of Physical Activity in Frail Elderly People (SEPAF) was used [12]. The reliability and validity of this scoring system for the frail elderly in Japan have been demonstrated and reported in the Japanese literature. In this scale there are three categories of physical activity: Walking, Stairs, and Lifting. The participant rates perceived activity burden (duration and exertion) on a five level Likert scale from Can’t perform at all, to Absolutely can perform and where 5 to 25 points are allocated and where the higher scores indicate greater SE.
6)
For the evaluation of HRQOL the comprehensive SF-36v2 was used. The SF-36v2 is composed of eight subscales: Physical functioning (PF), Role physical (RP), Bodily pain (BP), General health perceptions (GH), Vitality (VT), Social functioning (SF), Role emotional (RE), Mental health (MH) [13]. Deviation scores for each subscale were calculated.

Postoperative physical therapy was conducted according to our institution’s clinical path. From the next day after surgery range of motion exercises, strength training and walking with full weight-bearing were started. Approximately two weeks postoperatively, depending on the degree of walking improvement achieved, balance practice and stairs were added. Discharge was planned for 3 weeks post-op with the goal of achieving independence in walking and stairs before discharge. After discharge outpatient physical therapy was continued 1 to 2 times weekly for 3 months to support the continuation of home exercise and to monitor the improvement of physical function and physical activity. After three months the subjects were given instruction along with evaluation results and feedback to continue strength training exercises such as half-squats and one-leg stands on their own at home. Evaluations were conducted prior to surgery and at three and six months post-operatively.
2.3 Statistical analysis

For statistical evaluation one-way analysis of variance and Bonferroni multiple comparison were conducted on each measured aspect of the recovery progress. Additionally at 6 months, to clarify the factors relevant to HRQOL, univariate analyses were performed on each of the SF-36v2 subscales using an age-adjusted partial correlation coefficient. Multiple regression analysis using the stepwise method was performed, with factors found to have correlation to the eight SF-36v2 subscales designated as independent variables, and with the SF-36v2 subscale scores designated as dependent variables. Statistical analyses were performed using SPSS ver. 25.0 (IBM, Japan) with significance set at 5%.

3. Results

Physical Function and Physical Activity SE recovery progression is shown in Table 2. Knee extension strength at 6 months improved significantly ( $p<$ 0.001) over both preoperative and 3 months postoperative values. TUG and OLS at both 3 and 6 months were significantly improved ( $p<$ 0.001) over preoperative values. WOMAC-J operative side and non-operative side pain and function at both 3 and 6 months were significantly improved ( $p<$ 0.001) over preoperative values. Also WOMAC-J operative side pain at 6 months was significantly improved ( $p<$ 0.001) over 3 months postoperative values. All measures of Physical Activity (SE) including Walking SE, Stairs SE and Lifting SE were significantly improved ( $p<$ 0.001) over preoperative values at both 3 and 6 months postoperatively.

Table 2
Outcome measures

	Pre-op		Post-op 3 M		Post-op 6 M
Quadriceps strength (N $\cdot$ m/kg)	56.0	$\pm$ 24.6	58.6	$\pm$ 18.0	67.1	$\pm$ 18.0 ${}^{\ast\ast 2),\ast\ast 3)}$
TUG (seconds)	11.2	$\pm$ 3.6	9.6	$\pm$ 2.6 ${}^{\ast\ast 1)}$	9.4	$\pm$ 2.6 ${}^{\ast\ast 2)}$
OLS (seconds)	12.4	$\pm$ 17.2	2 2.9	$\pm$ 27.6 ${}^{\ast\ast 1)}$	23.3	$\pm$ 25.9 ${}^{\ast\ast 2)}$
WOMAC-J (pts)
Operative side pain	47.3	$\pm$ 20.0	73.9	$\pm$ 18.1 ${}^{\ast\ast 1)}$	78.1	$\pm$ 16.7 ${}^{\ast\ast 2),\ast 3)}$
Non-operative side pain	69.2	$\pm$ 23.5	79.2	$\pm$ 19.6 ${}^{\ast\ast 1)}$	77.2	$\pm$ 20.3 ${}^{\ast\ast 2)}$
Function	58.8	$\pm$ 20.2	77.5	$\pm$ 16.0 ${}^{\ast\ast 1)}$	79.4	$\pm$ 14.8 ${}^{\ast\ast 2)}$
SEPAF (pts)
Walking SE	13.1	$\pm$ 5.5	17.1	$\pm$ 5.0 ${}^{\ast\ast 1)}$	17.6	$\pm$ 4.5 ${}^{\ast\ast 2)}$
Stairs SE	9.2	$\pm$ 4.6	12.5	$\pm$ 5.2 ${}^{\ast\ast 1)}$	12.3	$\pm$ 5.2 ${}^{\ast\ast 2)}$
Lifting SE	16.0	$\pm$ 6.1	18.1	$\pm$ 5.6 ${}^{\ast\ast 1)}$	18.6	$\pm$ 5.4 ${}^{\ast\ast 2)}$

TUG: Timed Up and Go test. OLS: One Leg Standing time test. WOMAC-J: Western Ontario and McMaster Universities Osteoarthritis Index. SEPAF: Self-Efficacy of Physical Activity in Frail Elderly People. ${}^{\ast\ast 1)}$ : Pre-op and post-op 3 M $p<$ 0.01. ${}^{\ast 1)}$ : Pre-op and post-op 3 M $p<$ 0.05. ${}^{\ast\ast 2)}$ : Pre-op and post-op 6 M $p<$ 0.01. ${}^{\ast\ast 3)}$ : Post-op 3 M and post-op 6 M $p<$ 0.01. ${}^{\ast 3)}$ : Post-op 3 M and post-op 6 M $p<$ 0.05.

Table 3

SF-36v2 8 subscales

	Pre-op	Post-op 3 M	Post-op 6 M
PF	15.3 $\pm$ 14.7	27.8 $\pm$ 15.2 ${}^{\ast\ast 1)}$	27.7 $\pm$ 15.2 ${}^{\ast\ast 2)}$
RP	25.7 $\pm$ 14.3	32.3 $\pm$ 14.5 ${}^{\ast\ast 1)}$	34.6 $\pm$ 12.0 ${}^{\ast\ast 2)}$
BP	33.1 $\pm$ 7.5	41.0 $\pm$ 8.9 ${}^{\ast\ast 1)}$	41.4 $\pm$ 8.4 ${}^{\ast\ast 2)}$
GH	42.0 $\pm$ 9.4	46.5 $\pm$ 9.8 ${}^{\ast\ast 1)}$	45.8 $\pm$ 9.9 ${}^{\ast\ast 2)}$
VT	42.9 $\pm$ 11.2	47.2 $\pm$ 10.3 ${}^{\ast\ast 1)}$	47.2 $\pm$ 8.8 ${}^{\ast\ast 2)}$
SF	37.0 $\pm$ 14.5	41.2 $\pm$ 14.8 ${}^{\ast 1)}$	42.6 $\pm$ 13.0 ${}^{\ast\ast 2)}$
RE	31.3 $\pm$ 15.9	36.1 $\pm$ 15.1 ${}^{\ast\ast 1)}$	38.2 $\pm$ 13.4 ${}^{\ast\ast 2)}$
MH	43.8 $\pm$ 11.5	47.8 $\pm$ 11.3 ${}^{\ast\ast 1)}$	48.1 $\pm$ 9.8 ${}^{\ast\ast 2)}$

PF: Physical functioning. RP: Role physical. BP: Bodily pain. GH: General health perceptions. VT: Vitality. SF: Social functioning. RE: Role emotional. MH: Mental health. ${}^{\ast\ast 1)}$ : Pre-op and post-op 3 M $p<$ 0.01. ${}^{\ast 1)}$ : Pre-op and post-op 3 M $p<$ 0.05. ${}^{\ast 1)}$ : Pre-op and post-op 3 M $p<$ 0.05. ${}^{\ast\ast 2)}$ : Pre-op and post-op 6 M $p<$ 0.01.

The recovery progression of HRQOL is shown in Table 3. Significant improvement over preoperative values was seen in all SF-36v2 subscales at 3 months postoperatively (PF, RP, BP, GH, VT, MH: $p<$ 0.001, SF: $p=$ 0.040, RE: $p=$ 0.002) and at 6 months (PF, RP, BP, GH, VT, RE, MH: $p<$ 0.001, SF: $p=$ 0.002).

The age-adjusted partial correlation coefficients showing correlation between the SF-36v2 subscales and all measurement items are shown in Table 4. PF showed significant correlation ( $|r|=0.25\sim 0.57$ ) to knee extension strength, TUG, operative side knee pain, knee function and all measures of Physical Activity SE. RP showed significant correlation ( $|r|＝0.20\sim 0.54$ ) to TUG, operative side knee pain, knee function and all measures of Physical Activity SE. BP showed significant correlation ( $r=0.28\sim 0.59$ ) to operative side knee pain, non-operative side knee pain, knee function and all measures of Physical Activity SE. GH showed significant correlation ( $|r|=0.23\sim 0.53$ ) to TUG, OLS, operative side knee pain, knee function and all measures of Physical Activity SE. VT showed significant correlation ( $|r|=0.20\sim 0.57$ ) to TUG, OLS, operative side knee pain, knee function and all measures of Physical Activity SE. SF showed significant correlation ( $r=0.24\sim 0.42$ ) to operative side knee pain, knee function, and RE showed significant correlation ( $r=0.37\sim 0.49$ ) to operative side knee pain, knee function and all Physical Activity SE measures except Stairs SE. MH showed significant correlation ( $r=0.20\sim 0.45$ ) to operative side knee pain, knee function and all measures of Physical Activity SE.

Table 4

Partial correlation coefficient with SF-36v2 subscale post-op 6 M

	Quadriceps strength	TUG	OLS	Operative side pain	Non-operative side pain	Function	Walking SE	Stairs SE	Lifting SE
PF	0.27 ${}^{\ast\ast}$	$-$ 0.25 ${}^{\ast\ast}$	0.19	0.25 ${}^{\ast}$	0.13	0.57 ${}^{\ast\ast}$	0.48 ${}^{\ast\ast}$	0.43 ${}^{\ast\ast}$	0.35 ${}^{\ast\ast}$
RP	0.14	$-$ 0.20 ${}^{\ast}$	0.16	0.37 ${}^{\ast\ast}$	0.10	0.54 ${}^{\ast\ast}$	0.50 ${}^{\ast\ast}$	0.27 ${}^{\ast\ast}$	0.31 ${}^{\ast\ast}$
BP	0.03	$-$ 0.16	0.12	0.55 ${}^{\ast\ast}$	0.47 ${}^{\ast\ast}$	0.59 ${}^{\ast\ast}$	0.48 ${}^{\ast\ast}$	0.28 ${}^{\ast\ast}$	0.34 ${}^{\ast\ast}$
GH	0.17	$-$ 0.28 ${}^{\ast\ast}$	0.23 ${}^{\ast}$	0.37 ${}^{\ast\ast}$	0.18	0.53 ${}^{\ast\ast}$	0.39 ${}^{\ast\ast}$	0.39 ${}^{\ast\ast}$	0.40 ${}^{\ast\ast}$
VT	0.04	$-$ 0.29 ${}^{\ast\ast}$	0.30 ${}^{\ast\ast}$	0.45 ${}^{\ast\ast}$	0.20 ${}^{\ast}$	0.57 ${}^{\ast\ast}$	0.51 ${}^{\ast\ast}$	0.37 ${}^{\ast\ast}$	0.48 ${}^{\ast\ast}$
SF	0.10	$-$ 0.07	0.17	0.33 ${}^{\ast\ast}$	0.08	0.38 ${}^{\ast\ast}$	0.42 ${}^{\ast\ast}$	0.24 ${}^{\ast}$	0.27 ${}^{\ast\ast}$
RE	0.10	$-$ 0.14	0.14	0.38 ${}^{\ast\ast}$	0.13	0.49 ${}^{\ast\ast}$	0.48 ${}^{\ast\ast}$	0.18	0.37 ${}^{\ast\ast}$
MH	0.02	$-$ 0.02	0.15	0.45 ${}^{\ast\ast}$	0.16	0.44 ${}^{\ast\ast}$	0.31 ${}^{\ast\ast}$	0.20 ${}^{\ast}$	0.36 ${}^{\ast\ast}$

${}^{\ast\ast}$ : $p<$ 0.01. ${}^{\ast}$ : $p<$ 0.05.

Table 5

Multiple regression analysis

Dependent variable	Independent variable	B	$\beta$	$p$	R	R ${}^{2}$
PF	(Constant)	$-$ 22.664		0.001	0.612	0.374
	Function	0.458	0.445	0.000
	Walking SE	0.788	0.231	0.020
RP	(Constant)	$-$ 2.920		0.587	0.590	0.348
	Function	0.301	0.369	0.000
	Walking SE	0.779	0.289	0.005
BP	(Constant)	6.589		0.073	0.693	0.481
	Function	0.222	0.391	0.000
	Non-operative side pain	0.099	0.239	0.004
	Operative side pain	0.122	0.242	0.008
GH	(Constant)	18.479		0.00	0.517	0.267
	Function	0.344	0.517	0.000
VT	(Constant)	14.719		0.00	0.646	0.418
	Function	0.199	0.337	0.001
	Lifting SE	0.451	0.277	0.002
	Operative side pain	0.105	0.200	0.026
SF	(Constant)	21.188		0.00	0.423	0.179
	Walking SE	1.215	0.423	0.000
RE	(Constant)	1.238		0.843	0.525 ${}^{\text{b}}$	0.276
	Function	0.287	0.317	0.003
	Walking SE	0.804	0.273	0.009
MH	(Constant)	21.563		0.000	0.519	0.27
	Operative side pain	0.218	0.371	0.000
	Lifting SE	0.515	0.284	0.001

B: Non-standard partial regression coefficient. $\beta$ : Standardized partial regression coefficients.

Results of multiple regression analyses of factors impacting the SF-36v2 subscale scores are listed in Table 5. Extracted factors were knee function and Walking SE for PF, RP and RE; knee function, operative-side knee pain and non-operative side knee pain for BP; knee function for GH; knee function, Lifting SE and operative-side knee pain for VT; Walking SE for SF; and operative-side knee pain and Lifting SE for MH.

4. Discussion

As pointed out in the introduction, this study was, at the time, the longest follow up using the SF-36 instrument in the Japanese population to measure TKA recipients’ recovery of HRQOL along with physical function and Physical Activity SE and, all of which were clearly significant at 3 and 6 months post-op. Moreover, as the study’s primary objective, this study clarifies that in addition to improvement of knee pain and physical function, SE for physical activity substantially determines the overall HRQOL of TKA recipients, and thereby supports calls for further research and development of rehabilitative interventions to improve Physical Activity SE.

Physical activity SE scores have been reported for Japanese frail elderly [12]. While the 6 month post-TKA Physical Activity SE scores in this study were improved over preoperative scores, none of the scores were up to the reported averages for the frail elderly in Japan. Prior to TKA recipients have lower physical activity levels than healthy individuals [14] and while their post-operative physical activity increases it remains lower than that of healthy individuals [15]. Accordingly, the reduced preoperative physical activity of TKA recipients may be due to lower Physical Activity SE.

Reliability of SF-36v2 scores were validated for the Japanese healthy population [13]. Scores for 70–80 year old people were reported at PF 37.9, RP 42.4, BP 46.9, GH 47.0, VT 49.4, SF and MH 50.9. At 6 months post-op none of the TKA recipients in this study reached 50 points for any of the SF-36v2 subscale scores, and they scored lower than the normal for their age-matched cohorts in the Japanese population. It has been reported that while HRQOL improves at 12 months post-op as indicated by SF-36v2 subscale scores, those scores still remain below the normal values for the population at large [16]. The results of this study were in line with previous studies. Improvement in the HRQOL of TKA recipients has been reported to be time limited by the increase of comorbidities and by non-TKA related pain and other environmental factors that impact the quality of life [17]. This would suggest that for longer-term HRQOL improvement interventions related to comorbidities, pain in other joints, and environmental factors would contribute to the HRQOL of TKA recipients.

Factors in this study found to impact SF-36v2 scores at 6 months post-op were knee pain, physical function and Physical Activity SE. It has been reported that TKA recipients score well below healthy individuals in pain and function but that these remain the most important predictive factors for the improvement of HRQOL among TKA recipients [18]. In this respect our study supports the conclusions of previous research. However, it has been reported that improvement, in physical function among the elderly does not directly correlate to HRQOL improvement [19, 20]. Indeed, for the TKA recipients in our study, physical function indicators such as knee extension strength and TUG performance indicating walking and dynamic balance, and OLS scores indicating passive balance were all found to have significant correlation to the eight subscales of the SF-36v2. (This is a comprehensive index of HRQOL, and again, these results are in line with previous studies.) but, our multiple regression analysis did not support a direct influence. We think pain reduction and improvement in knee function resulted in HRQOL improvement to the extent that those factors promoted activity and participation in the course of daily living.

Of course we are not the first to posit that SE is the major decisive factor in the outcome of TKA recipients. Early post-operative SE has been reported to be an excellent prognostic indicator of long-term outcomes after TKA [21]. Accordingly, intervention designed for early postoperative SE improvement is important for HRQOL improvement. According to McAuley et al., efficacy expectation is a parameter of HRQOL improvement, and is enhanced by physical activity and the implementation of exercise [22]. In our data as well, it is probable that SE for physical activity rose with physical activity and the implementation of exercise, influencing HRQOL improvement. Accordingly, after discharge and after outpatient rehabilitation has ended, how to get TKA recipients to continue physical activity and exercise is key.

According to Bandura improvement of SE is affected by information from four sources including performance accomplishments, vicarious experience, verbal persuasion and emotional arousal [6]. A study among local elderly residents has posited the efficacy of behavioral science-based interventions that focus on those four information sources for the improvement of physical activity SE [23]. In the future outlook for the field of locomotive organ rehabilitation, the provision of behavioral-science-based intervention aimed at physical activity SE improvement can be expected to contribute to the continuity of physical activity and exercise and the improvement of HRQOL.

5. Limitations and conclusion

Among the limitations of this study we might mention that the small sample size, where all subjects were treated at the same facility, weakens any generalizations we might wish to make. We did not examine other factors that could influence HRQOL such as environmental factors, comorbidities, pain or dysfunction in other joints, or wait times prior to surgery. Also, after the end of the first 3 months’ rehabilitation period, patient lifestyle, exercise habits and living environment are unclear and could skew the final 6 month evaluation of physical function, Physical Activity SE, and HRQOL maintenance. However, this study clarifies the fact that Physical Activity SE ranks alongside knee pain and function in importance as a factor contributing to HRQOL gains in TKA recipients. We suggest that this warrants a call for behavioral-science-based interventions in rehabilitation practice that are aimed at promoting SE for physical activity in TKA recipients.

Footnotes

Acknowledgments

The authors would like to thank the Rehabilitation Medicine Department staff for helping them with the measurements.

Conflict of interest

The authors have no conflict of interest to report.

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