Efficacy of Total Knee Arthroplasty in Elderly Patients With Locomotive Syndrome: a Prospective Longitudinal Study

doi:10.21203/rs.3.rs-841197/v1

Background: To preserve the ability to perform physical activities among the elderly, the concept of locomotive syndrome and its evaluation method, the locomotive syndrome risk test, have been applied in an integrated manner to capture the decline in mobility resulting from musculoskeletal disorders. During treatment, physicians can use the locomotive syndrome risk test to evaluate the impact of each therapy such as total knee arthroplasty for knee osteoarthritis, a common disorder found in locomotive syndrome. The purpose of this study was to evaluate the impact of total knee arthroplasty in the elderly with respect to locomotive syndrome.

Methods: A total of 111 patients were registered at six hospitals prior to total knee arthroplasty and postoperatively followed up for 1 year. Three components of the locomotive syndrome risk test (the two-step test, stand-up test, and geriatric locomotive function scale-25) were assessed together with the EuroQol-5 Dimension scores pre- and postoperatively.

Results: Post surgery, all three components of the locomotive syndrome　risk test as well as the EuroQol-5 Dimension utility score showed significant improvements from the baseline (two-step test, 1.01±0.25 to 1.12±0.21; stand-up test, 2.02±1.14 to 2.38±1.20; geriatric locomotive function scale-25, 38.3±15.8 to 18.7±16.6, mean ± standard deviation). The ratio of stage 3 locomotive syndrome patients (progressed stage of decrease in mobility, restricting social engagement) reduced from 82.3% to 33.9% postoperatively. There was no significant difference in the degree of change in the three test scores between the younger (60-74 years) and older (≥75 years) age groups.

Conclusions: We found that total knee arthroplasty has a major impact in preventing the progression of locomotive syndrome in patients with knee osteoarthritis. The locomotive syndrome risk test is a feasible tool for longitudinal evaluation of patients with musculoskeletal diseases of varying severity and with multiple symptoms.

Trial registration: This study was registered as UMIN000023595 (10/08/2016)

Geriatrics & Gerontology

total knee arthroplasty

locomotive syndrome

elderly patients

longitudinal study

health problems

Managing the health problems of the aging population is now a common medical challenge in many countries including Japan where the elderly (older than 65 years) constitute more than 28% of the total population [1, 2]. In these countries, health policies are directed at prolonging the period during which the elderly can live independently without care from others. According to Japanese governmental statistics, the three leading causes of disabilities which compel the elderly to avail the services of the long-term care insurance (LTCI) system, a governmental policy to provide suitable individual care services for the disabled elderly, are cerebrovascular diseases, dementia, and musculoskeletal diseases [3]. Therefore, the management of problems associated with aging with respect to the musculoskeletal system is of social interest, and this prompted the Japanese Orthopaedic Association to propose the concept of the locomotive syndrome in 2007 [4]. Locomotive syndrome is defined as a condition of decreased mobility in activities essential to daily life such as walking, standing up, and climbing stairs, resulting from impairment of the locomotive organs [5]. The severity of locomotive syndrome is evaluated using the locomotive syndrome (LS) risk test, a screening tool which consists of three tests: the two-step test, stand-up test, and 25-Question Geriatric Locomotive Function Scale (GLFS-25) [6, 7]. The simplicity and feasibility of these tests enable them to be used as a screening tool in various types of surveys focusing on not only the disabled elderly but also the general population [8–10].

Knee osteoarthritis (KOA) is a common pathological condition observed in patients with locomotive syndrome [11, 12]. Its painful symptoms prevent the active lifestyle typical of middle-aged people. In the later stages of the disease, the activities of daily living of the patients are also impaired [13, 14]. Total knee arthroplasty (TKA) sufficiently improves both pain and knee function of KOA patients which are commonly evaluated by knee-specific patient-reported outcome measures such as the Knee Society Score and the Japanese Knee Osteoarthritis Measure [15–17]. As the survival rate of implants has improved, the current therapeutic challenge is to maintain long term post-operative physical activities. However, several studies have revealed that the locomotive functions gradually declined after surgery even without implant-related problems [18, 19]. This may be due to the degenerative changes in musculoskeletal organs other than knees since most Japanese people undergo initial TKA surgeries in their 70s [20]. Therefore, patients opting for TKA should also be evaluated using an integrated measurement tool, such as the LS risk test, for musculoskeletal function and difficulties in daily living. While the application of the test has been reported in surgical treatments for hip osteoarthritis and lumbar canal stenosis, it has not been evaluated in patients undergoing TKA surgeries [21, 22]. Therefore, the purpose of this study was to evaluate the pre- and post-operative condition of patients undergoing TKA for KOA using the LS risk test to assess their condition from the point of view of integrated care in the management of musculoskeletal disorders.

Study participants

For this observational cohort study, patients who were scheduled to undergo TKA surgery were registered at six hospitals in a prospective manner. The inclusion criteria were as follows: (1) patients aged ≥ 60 and < 90 years and (2) those undergoing TKA for KOA in one or both knees. Those with severe comorbidities, such as chronic renal disease and chronic heart failure, were excluded. All subjects provided written informed consent prior to participation. The study was approved by the IRB of the authors’ affiliated institutions and conducted in accordance with the principles of the Declaration of Helsinki.

Data collection

The initial data, LS risk test scores, and 5-level EuroQol-5 Dimension (EQ-5D-5L) scores together with the demographic data were collected by a medical specialist within 3 months before the surgery. The patients were instructed to visit the hospital 1 year after surgeries to undergo similar evaluations as the one stated above. For patients who underwent TKA for both knees consecutively, the follow-up evaluations were scheduled 1 year after the last surgery.

Locomotive syndrome risk test

The locomotive syndrome risk test consists of one patient-reported outcome measure: the GLFS-25 and two performance tests: the two-step and stand-up tests. These tests were performed as described in previous papers [7]. To summarize, the GLFS-25 included 25 questions each of which had a 0–4 graded Likert scale about mobility-related difficulties in daily life, with the higher grades representing a deteriorating health condition. As for the two-step test, patients began from the standing position and then stepped forward as far as they could with the right and left steps in succession. The maximum distance covered by the two steps was divided by the patients’ heights for standardization. In the stand-up test, patients were asked to sit on boxes that were 10 to 40 cm high and then stand up without any support using either one or both legs. Successful trials were recorded.

Statistical analysis

To compare the demographic background between the two groups, we used Fisher’s exact test for categorical variables and the t-test for continuous variables. The differences in the pre- and post-operative test scores (LS risk test and EQ-5D) were compared using the paired t-test because of its approximately normal distribution (Supplementary Fig. 1). We used multiple imputation to handle the missing data in the GLFS-25 scores because of its relatively high percentage (22% of follow-up patients) [23]. We imputed by fully conditional specification method using discriminant function with Proc MI in SAS (SAS Institute, Cary, NC, USA) [24]. The imputation procedure used each score of all 25 questions of GLFS-25 because of their close association with the missing GLFS-25 value. The results across 20 imputed data set were combined by averaging and standard errors were adjusted according to within and between imputation variability [25]

The linear mixed-effects model with an unstructured covariance matrix for residuals was used to examine whether the pre- and post-operative change in each test score was different between the age groups. To control other possible confounders, we included the gender, number of TKAs (bilateral/unilateral), and body mass index in the model. We also compared the baseline test scores between patients who were followed up and those who were lost to follow-up. A p-value of less than 0.05 was considered statistically significant. All statistical analyses were performed using SAS 9.4 (SAS Institute, NC, US).

A total of 111 patients were enrolled in the study, 87 of whom completed the follow-up assessments. The follow-up period was 406.4 ± 102.5 (mean ± standard deviation) days after surgery. The age of the patients at the time of surgery was 74.6 ± 5.9 years, ranging from 60 to 88 years. The other demographic data are presented in Table 1. The pre-operative evaluation showed that the mean scores of the two-step test, stand-up test, and GLFS-25 were 1.01 ± 0.25, 2.02 ± 1.14, and 38.3 ± 15.8, respectively (Table 2). The details of the GLSF-25 scores are shown in Fig. 1, presenting the average scores for each item. The GLFS-25 questionnaire contains several items associated with “pain” (Q1: neck and upper limb pain, Q2: back and buttock pain, Q3: leg pain, and Q4: pain in motion). While the item for pain in the legs (Q3) had a higher average score than others, 48.1% of participants experienced moderate or severe pain in other parts of their bodies. Similar scores were observed in all three tests irrespective of whether the patients had undergone TKA for one or both knees. A significant difference was observed in the two-step test scores between those who dropped out and those who completed the follow-up. However, the results of the GLFS-25 and stand-up tests were similar between them (Supplementary Table 1).

Table 1

The demographic background of the patients
	Men (n=23)	Women (n=88)	Total (n=111)
Age, mean ± SD	74.0 ± 6.7	74.7 ± 5.7	74.6 ± 5.9
BMI, mean ± SD	26.2 ± 2.6	26.5 ± 4.1	26.4 ± 3.8
Bilateral operation, n(%)	2 (8.7)	14 (15.9)	16 (14.4)
Medication^#, n(%)
Hypertension	14 (73.7)	59 (75.6)	73 (75.3)
Diabetes Melltius	2(10.5)	15 (19.2)	17 (17.5)
Nsaids	8(42.1)	16 (20.5)	24 (24.7)
Osteoprosis*	0 (0.0)	19 (24.4)	19 (19.6)
Steroid	0 (0.0)	3 (3.9)	3 (3.1)
Depression	0 (0.0)	4 (5.1)	4 (4.1)
*p<0.05, significant sex difference using Fisher's exact test; BMI=body mass index.
#medication (n = 97).

Table 2

Pre and post-operative scores of locomotive syndrome risk test and EQ-5D
		Pre-operation		1-year post operation		P-value*
	N	Mean (SD)	Median (IQR)	Mean (SD)	Median (IQR)
Two-step test score	80	1.01 (0.25)	1.06 (0.90-1.17)	1.12 (0.21)	1.16 (1.02-1.27)	<0.001
Stand-up test score	83	2.02 (1.14)	2 (1-3)	2.38 (1.20)	2 (2-3)	0.0069
Total GLFS-25 score	68	38.3 (15.8)	37 (26-48)	18.7 (16.6)	13 (6.5-25)	<0.001
EQ-5D utility score	83	0.58 (0.14)	0.59 (0.53-0.67)	0.77 (0.17)	0.75 (0.67-1.0)	<0.001
SD = standard deviation; IQR = interquatile range; GLFS-25 = the 25-question geriatric locomotive function scale; EQ-5D = EuroQol 5 dimensions
* Paired t-test

The LS risk test and EQ-5D utility scores before surgery and at follow-up are shown in Fig. 2 and Table 2. Significant improvements were observed in all three components of the LS risk test as well as in the EQ-5D utility scores. The improvements in the mean values were 0.11 for the two-step test, 0.36 for the stand-up test, 19.6 for the GLFS-25, and 0.19 for EQ-5D (Table 2). For the GLFS-25, the changes in each item were examined using the mean values. While most of the items showed improvement after the surgery, a marked improvement (improvement of > 1.5 points) was observed in Q3 (leg pain) and Q13 (difficulty in walking briskly). On the other hand, no change was observed in Q8 (difficulty in putting on and taking off shirts) (Fig. 1).

The severity of locomotive syndrome is summarized by the locomotive syndrome staging criteria: normal, stage 1 (starting stage of decrease in mobility defined by two-step test score < 1.3, or stand-up test score ≤ 4, or GLFS-25 score ≥ 7), and stage 2 (progressing stage of decrease in mobility defined by two-step test score < 1.1, or stand-up test score ≤ 2, or GLFS-25 score ≥ 16) [8]. Recently, the more severe condition of decrease in mobility was defined as stage 3 (progressed stage of decrease in mobility, restricting social engagement defined by two-step test score < 0.9, or stand-up test score ≤ 1, or GLFS-25 score ≥ 24) to recommend visiting medical specialists [26]. In the preoperative survey, the ratio of the patients who were categorized as stage 3, 2, and 1 is 82.3%, 16.1%, and 1.6% respectively. The conversion of the stages of locomotive syndrome after surgery is presented in Fig. 3. The ratio of stage 3 patients reduced from 82.3–33.9% post-operatively, while the ratio of stage 2 patients increased from 16.1–45.2%.

Since locomotive syndrome tends to progress with age, patients undergoing TKA at older ages were speculated to have a worse clinical course. While patients in the older age group showed higher GLFS-25 scores indicating a poor condition both pre- and post-operatively, there was no interaction between the age group and the pre/post-operative time period (Table 3). This result indicated that age (60–74 years or ≥ 75 years) did not affect the degree of improvement afforded by the TKA surgery. Figure 4 illustrates the parallel trend of the LS risk test between the 60–74 and ≥ 75 age groups.

Table 3

The estimated effect of age groups on the change of pre-and post operative test scores, using linear mixed effects model
Outcomes and fixed effects	Estimate	SE	df	t value	Pr >\|t\|
Two-step test score
Period (post operation)	0.124	0.028	80	4.430	< .0001
Sex (male)	0.177	0.048	80	3.670	< .0001
Age group (age ≥ 75)	-0.087	0.052	80	-1.680	0.098
Number of TKA (bilateral)	0.013	0.051	80	0.260	0.792
BMI (bmi ≥ 25)	-0.059	0.041	80	-1.430	0.156
Period × age group	-0.029	0.041	80	-0.710	0.480
Stand-up test score
Period (post operation)	0.198	0.195	80	1.010	0.313
Sex (male)	0.615	0.257	80	2.400	0.019
Age group (age ≥ 75)	-0.401	0.251	80	-1.600	0.113
Number of TKA (bilateral)	-0.402	0.268	80	-1.500	0.138
BMI (bmi ≥ 25)	-0.399	0.220	80	-1.820	0.073
Period × age group	0.371	0.286	80	1.300	0.199
Total GLFS-25 score
Period (post operation)	-18.612	2.444	78	-7.620	< .0001
Sex (male)	-9.172	3.668	78	-2.500	0.015
Age group (age ≥ 75)	9.152	3.500	78	2.620	0.011
Number of TKA (bilateral)	-5.003	3.893	78	-1.290	0.203
BMI (bmi ≥ 25)	3.729	3.170	78	1.180	0.243
Period × age group	-1.688	3.536	78	-0.480	0.635
EQ-5D utility score
Period (post operation)	0.208	0.028	80	7.320	< .0001
Sex (male)	0.066	0.033	80	2.010	0.047
Age group (age ≥ 75)	-0.045	0.032	80	-1.410	0.161
Number of TKA (bilateral)	0.018	0.034	80	0.510	0.600
BMI (bmi ≥ 25)	-0.034	0.028	80	-1.230	0.224
Period × age group	-0.025	0.042	80	-0.590	0.557
Outcomes are three locomotive syndrome risk test scores and EQ-5D utility score. Each estimate reflects an association between each outcome (test score) and independent variables, adjusting for all other variables in the model.
Reference = period (pre-operation), female (sex), age < 75(age group), unilateral TKA (number of TKA), BMI (bmi < 25) SE = standard error; GLFS-25 = the 25-question geriatric locomotive function scale; EQ-5D = EuroQol 5 dimensions; BMI = body mass index.

In total, 16 participants (14.4%) underwent bilateral knee operation during the survey period. The magnitude of improvement was not affected by the number of TKAs (Table 3).

In this study, we described the condition of the musculoskeletal organs in patients undergoing TKA by the LS risk test and evaluated the changes afforded by the surgery. Our data clearly showed that most of the patients belonged to locomotive syndrome stage 2 or 3 pre-operatively (98.4%), and TKA improved their condition in terms of patient-oriented outcome measures and objective function tests.

A recent report on the reference values of the LS risk test in a healthy population showed that the median GLFS-25 scores for those aged between 65 and 69, and 75 and 79 were 4 and 6, respectively [10]. On the other hand, Yamada et al. reported that the mean GLFS-25 score for the elderly who availed the services of the LTCI system was 33.8 [9]. In our study, the average preoperative GLFS-25 score was 38.3 suggesting that the pre-operative condition of patients undergoing TKA was similar to the condition of individuals who need care and support and have a risk of dependency. The significant improvement in the GLFS-25 and other tests after TKA confirmed that joint replacement surgeries have a beneficial impact not only on knee pain and function but also on the improvement of general musculoskeletal function.

The selection of the optimal age is critical for successful surgeries [27, 28]. Our study showed that the degree of improvement provided by TKA is equivalent between the older (≥ 75 years) and younger (64–74 years) age groups, suggesting that surgery is expected to improve the ability to perform daily activities even in older patients. However, it should be noted that the pre- and post-operative GLFS-25 scores were higher in the older age group than that of the younger age group (mean post-operative GLFS-25 score, ≥ 75 age group, 21.8 ± 19.4 vs. 60–74 age group, 16.0 ± 13.5). As the number of people using the LTCI services increases after the age of 75, the residual dysfunction and difficulty in daily activities among the older age group patients should be carefully monitored so that their physical condition can be maintained through suitable lifestyle modifications and if necessary, treatments.

One of the advantages of the LS risk test is its ability to evaluate the condition of the musculoskeletal organs in an integrated manner. In our study, 48.1% of patients had moderate or severe pain in sites other than the leg, suggesting that the patients suffered not only from KOA but also from other musculoskeletal disorders such as degenerative spinal disorders and upper limb pain. As previously reported, many patients tend to have multiple bone and joint diseases, and the difficulties faced by them in daily life reflect the summation of all these symptoms [11, 29, 30]. Using the LS risk test, the physician can gauge the overall impact of the disease on patients’ daily living and the function of their locomotive organs. The integrated difficulties in the daily living of patients with multiple musculoskeletal problems have been evaluated using various quality of life assessment scales such as EQ-5D, a well-established scale that consists of five questionnaires, assessing the mobility, self-care, activity, pain, and anxiety [31]. Because Seichi et al. reported that the GLFS-25 score correlated well with the EQ-5D score, the GLFS-25 has a potential to be used as a quality of life outcome measure for patients with musculoskeletal diseases as demonstrated in the current study where the two scales showed similar trends [6]. While the LS risk test questionnaire form takes longer to complete which is a disadvantage, its wide range of scores provides sufficient sensitivity to detect changes during longitudinal observation. Therefore, the LS risk test would be useful for a long-term follow-up analysis in patients undergoing conservative treatment and/or musculoskeletal surgeries in organs other than the knee joints. In future, the data accumulated from the LS risk test during the long-term follow-up will help physicians develop therapeutic strategies for managing the mobility function of each patient.

Our study has several limitations. First, we excluded patients with severe comorbidities from the study. Therefore, the current data should be considered as information conceived from typical clinical cases of KOA. In cases with severe comorbidities, the score of the LS risk test would be influenced by conditions other than those affecting the bones and joints and would need to be interpreted more cautiously. Second, since the minimum clinically important difference (MCID) of the LS risk test has not been established, the efficacy of treatment in each case cannot be determined. Further studies are required to determine the MCID to identify the factors that may have an impact on the efficacy of treatment. Finally, a fraction of patients was lost to follow-up. The lower score observed in the two-step test in the lost to follow-up group suggests the possibility that patients who had poor mobility after surgery could not turn up for the follow-ups. As this is an inherent limitation in longitudinal studies related to mobility disorders, an alternative method of data collection from patients who have restricted mobility is required in future studies.

In conclusion, we observed that the LS risk test was useful in evaluating patients undergoing TKA. In the baseline assessment, the scores revealed that the physical condition of the patients was similar to that of individuals who required assistance for their daily activities. These tests can also be used to describe changes after surgery, providing qualitative information about difficulties in daily life and functions. The locomotive syndrome risk test is a feasible tool for evaluating patients with musculoskeletal diseases of varying severity and with multiple symptoms.

LTCI: long-term care insurance

LS: locomotive syndrome

GLFS-25: 25-Question Geriatric Locomotive Function Scale

KOA: knee osteoarthritis

TKA: total knee arthroplasty

EQ-5D-5L: 5-level EuroQol-5 Dimension

MCID: minimum clinically important difference

Ethics approval and consent to participate: All subjects provided written informed consent prior to participation, which was approved by the ethical committee of the University of Tokyo (No. 11256) as well as by each hospital.

Consent for publication: Not applicable

Availability of data and materials: The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Competing interests: All authors declare that they have no conflicts of interest.

Funding: This study was supported by JOA-Subsidized Science Project Research 2015-1. The funder had no role in collection, analyses, and interpretation of the data, nor decision to submit results.

Authors' contributions: TO, KN and ST designed the study. KY and YI performed statistical analyses. HM and KO established data collecting systems. KH, TK, KW, TK, YI, YY, TS, SM, SK, MW, TT, MT, TI, HM, SI and YM collected data and interpreted the patient data. TO and KY wrote the manuscript. All authors read and approved the final manuscript.

Acknowledgements: Not applicable

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No competing interests reported.

Efficacy of Total Knee Arthroplasty in Elderly Patients With Locomotive Syndrome: a Prospective Longitudinal Study

Status:

Version 1

Abstract

Figures

Background

Methods

Study participants

Data collection

Locomotive syndrome risk test

Statistical analysis

Results

Discussion

Conclusions

Abbreviations

Declarations

References

Additional Declarations

Supplementary Files

Status:

Version 1