SPINE Volume 39, Number 10, pp 820-825 ©2014, Lippincott Williams & Wilkins
HEALTH SERVICES RESEARCH
Reliability and Validity of Simplified Chinese Version of Swiss Spinal Stenosis Questionnaire for Patients With Degenerative Lumbar Spinal Stenosis Honglei Yi, MD,*† Xianzhao Wei, MD,* Wei Zhang, MD,‡ Ziqiang Chen, MD,* Xinhui Wang, MD,† Xinran Ji, MD,* Xiaodong Zhu, MD,* Fei Wang, MM,* Ximing Xu, MD,* Zhikun Li, MM,* Jianping Fan, MM,* Chuanfeng Wang, MM,* Kai Chen, MM,* Guoyou Zhang, MD,* Yinchuan Zhao, MD,* and Ming Li, MD*
Study Design. This was a prospective clinical validation study. Objective. To evaluate the reliability and validity of the adapted simplified Chinese version of Swiss Spinal Stenosis (SC-SSS) Questionnaire. Summary of Background Data. The SSS Questionnaire is a reliable and valid instrument to assess the perception of function and pain for patients with degenerative lumbar spinal stenosis. However, there is no culturally adapted SSS Questionnaire for use in mainland China. Methods. This was a prospective clinical validation study. The adaption was conducted according to International Quality of Life Assessment Project guidelines. To examine the psychometric properties of the adapted SC-SSS Questionnaire, a sample of 105 patients with lumbar spinal stenosis were included. Thirtytwo patients were randomly selected to evaluate the test-retest reliability. Reliability assessment of the SC-SSS Questionnaire was determined by calculating Cronbach α and intraclass coefficient values. Concurrent validity was assessed by correlating SC-SSS Questionnaire scores with relevant domains of the 36-Item Short Form Health Survey. Results. Cronbach α of the symptom severity scale, physical function scale, patients, and satisfaction scale of SC-SSS Questionnaire are 0.89, 0.86, 0.91, respectively, which revealed
From the *Department of Orthopaedic Surgery, The Affiliated Changhai Hospital of the Second Military Medical University, Shanghai, China; †89th Hospital of PLA, Weifang, Shandong, China; and ‡Department of Orthopaedics, 401th Hospital of PLA, Qingdao, Shandong, China. Acknowledgment date: July 22, 2013. First revision date: January 7, 2014. Acceptance date: February 2, 2014. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. No relevant financial activities outside the submitted work. Address correspondence and requests for reprints to Ming Li, MD, Orthopedic Department of Changhai Hospital, Second Military Medical University. No 168, Changhai Rd, Shanghai, People’s Republic of China; E-mail: [email protected] DOI: 10.1097/BRS.0000000000000273
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very good internal consistency. The test–retest reproducibility was found to be excellent with the intraclass correlation coefficient of 0.93, 0.91, and 0.95. In terms of concurrent validity, SC-SSS Questionnaire had good correlation with physical functioning and bodily pain of 36-Item Short Form Health Survey (r = 0.663, 0.653) and low correlation with mental health (r = 0.289). The physical function scale had good correlation with physical functioning of 36-Item Short Form Health Survey (r = 0.637), whereas the rest had moderate correlation. The satisfaction scale score was highly correlated with the change in the symptom severity (r = 0.71) and physical function (r = 0.68) scale score. Conclusion. The SC-SSS Questionnaire showed satisfactory reliability and validity in the evaluation of functionality in patients with lumbar spinal stenosis who are experiencing neurogenic claudication. It is simple and easy to use and can be recommended in clinical and research practice in mainland China. Key words: lumbar spinal stenosis, Swiss Spinal Stenosis Questionnaire, Chinese, reliability, validity. Level of Evidence: 3 Spine 2014;39:820–825
D
egenerative lumbar spinal stenosis (LSS) refers to narrowing of the osteoligamentous vertebral canal and/ or the intervertebral foramina causing compression of the thecal sac and/or the caudal nerve roots, with the symptoms of intermittent claudication, radicular pain, paresthesia, and weakness of the legs, as described by Postacchini.1 To quantitatively measure the intensity of low back pain, a variety of subjective evaluation instruments in the past 20 years, such as visual analogue scale (VAS), Oswestry Disability Index (ODI),2 Functional Rating Index,3 Roland–Morris Disability Questionnaire,4 and Quebec Back Pain Disability Scale,5 have been created. However, none of these are spinal stenosis-specific. When VAS is applied, walking capacity cannot necessarily be assessed. In addition, although the ODI can assess the intensity of pain and restrictions in activities of daily living, including walking capacity due to pain, it cannot sufficiently assess symptoms other than pain. As a result,
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HEALTH SERVICES RESEARCH with the currently available questionnaires, there are limits to comprehensively assessing the severity of LSS symptoms. Therefore, Stucki et al6 developed a short spinal stenosisspecific outcome measure in 1996, which was named Swiss Spinal Stenosis (SSS) Questionnaire consisting of symptom severity, physical function, and satisfaction scales. Stucki et al describe explicitly how the measurement was developed, how the items in each scale were chosen, and how to calculate the score of the scales. The minimum score is 13 and the highest is 59. The higher the score is, the more serious the patient’s dysfunction. In recent years, SSS Questionnaire has been widely applied in many publications as a very popular tool because of its disease-specific measurement.7–14 Therefore, the North American Spine Society recommended that this questionnaire be considered as a potential “gold standard” in future studies of specific outcome measures for the treatment of LSS.15 SSS Questionnaire has been translated to several languages in Norway, Switzerland, Slovenia, and other countries.7–14 As far as we know, there is no simplified Chinese (SC) version yet. Therefore, the purpose of this study was to develop and adapt SSS Questionnaire into SC and assess the reliability and validity among Chinese patients with LSS.
MATERIALS AND METHODS The Questionnaire The SSS Questionnaire is a specific measure of functionality in patients with LSS. It includes symptom severity, physical function, and satisfaction scales. The 7 questions of symptom severity addressed overall pain, pain frequency, back pain, leg pain, numbness, weakness, and trunk balance. All but 1 item (1–5) had Likert response scales with 5 categories scored. Balance disturbance had 3 categories and was transformed to 1–3–5 scale. The 6 physical function questions asked about walking distance and ability to walk for pleasure, for shopping, for getting around the house or apartment, and from bathroom to bedroom. All but 1 item had scales with 4 categories (no, could not perform; yes, but always with pain; yes, but sometimes with pain; yes, comfortably). The 4 categories of walking distance were more than 2 miles, more than 2 blocks but less than 2 miles, more than 50 ft but less than 2 blocks, and less than 50 ft. The possible range of scores is 1 to 4. The scale score was calculated as the unweighted mean of all answered items in the questionnaire except that more than 2 items were missing. The satisfaction questions asked about patient satisfaction with the overall results of the spinal surgery; pain relief after the surgery; walking ability after the surgery; ability to do housework or yard work or job after the surgery; strength in the thighs, legs, or feet; and balance or steadiness on feet. These questions had Likert response scales with the 4 categories: very satisfied, somewhat satisfied, somewhat dissatisfied, and very dissatisfied. The range of the scale scores is 1 to 4. The satisfaction scale score was the unweighted mean of all 6 items if the number of responses exceeded 4.6 Spine
Validation of Simplified Chinese SSS • Yi et al
Translation According to international guidelines recommended by Beaton et al16 the procedure of cross-cultural adaptation of the SC-SSS Questionnaire was similar to our previous studies.3–5,17 The original English SSS Questionnaire was translated into SC by 2 bilingual translators of 1 native Chinese-speaking spine surgeon and 1 nonmedical worker. They independently performed the forward translation to SC. After comparing the translations, discrepancies were identified and reconciled by consensus. The backward translation was performed by 2 independent native English speakers with Chinese as their second language, who were blinded to the study purpose. Both translators lacked medical background and were unaware of the prior translation procedures or the original document. Each English translation was compared with the original English SSS Questionnaire and checked for inconsistencies by the translation team. Then, the team consolidated the original questionnaire, translations, back translations, and corresponding written reports to reach a consensus. Before finalizing, the SC-SSS Questionnaire was pilot tested in 44 patients with LSS. Each patient completed the SC-SSS Questionnaire and was subsequently interviewed about any difficulties in completing the questionnaire or understanding the purpose and meaning of each question. The team discussed all the findings and then developed the final SC-SSS Questionnaire (see Supplemental Digital Content, Appendix, available at http://links.lww.com/BRS/A858), which was subjected to further psychometric testing.
Participants To examine the psychometric properties and clinical application of the adapted SC-SSS Questionnaire, a survey was conducted in a group of randomly selected 118 outpatients and inpatients in Changhai Hospital of Shanghai and 89th Military Hospital of Shandong. These patients are all diagnosed with LSS by attending doctors. All patients filled in the SC-SSS Questionnaire and a previously validated Chinese (Mainland) version of the 36-Item Short Form Health Survey (SF-36) in the hospital with a consent form. Three to 5 days after their first survey, some of patients were asked to complete the tests again by phone or e-mail. The SF-36 is a brief self-administered questionnaire derived from an aggregate of items included in the RAND/Medical Outcomes Study. The categories of health tested included physical functioning, role limitations due to physical problems, bodily pain, general health, vitality, social functioning, role limitations due to emotional problems, mental health (MH), and 1 single-item scale on health transition. When functioned in Hangzhou, China, results are near equivalent to those when tested in an American Chinese or Hong Kong populations.18 Inclusion criteria were as follows: (1) more than 50 years of age; (2) low back pain, lower limbs numbness, and pain aggravated after the extension of the body; (3) hyperplasia of facet joint, hypertrophy of yellow ligament, bulge or herniation of the intervertebral disc, and oppressive nerve had been www.spinejournal.com
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HEALTH SERVICES RESEARCH proven by the films; and (4) the patient received at least 6-year compulsory education and accurately understood the questionnaire. Exclusion criteria included trauma, tumor, inflammation, or history of lumbar spine surgery. Ethical approval from the research committee of the author’s institution and participation consent were obtained.
Reliability and Validity Reliability assessment of the SC-SSS Questionnaire was determined by calculating Cronbach α and intraclass coefficient (ICC) values as previously described. Concurrent validity was evaluated by comparing SC-SSS Questionnaire domains with relevant domains of the SF-36 questionnaire; correlation was made using Pearson correlation coefficients (r).
Statistical Analysis SPSS version 13.0 (SPSS, Statistical Package for the Social Sciences) for Windows was used for all statistical analyses. Data were expressed as the mean ± SD and were analyzed using a Pearson correlation method with the level of significance P < 0.05.
RESULTS A total of 105 patients with LSS completed the questionnaires from December 2008 to April 2009. All patients came from 2 regions representing different economic development degrees: a general hospital in developed regions in eastern coast (Changhai Hospital) and a primary hospital in an inland underdeveloped region (the 89th military hospital). Of these patients, 75 outpatients decided to have nonsurgical treatment, whereas 30 inpatients were ready for surgery. Table 1 shows their age, sex, pain or numbness duration, and occupational level. All of the patients completed the physical function and symptom severity domains of SC-SSS Questionnaire within 3 minutes, whereas 29 of the inpatients finished satisfaction questions of SC-SSS Questionnaire within 1 minute, average 13 months after the surgical procedures. All of the patients completed the SF-36 test. Table 2 summarizes the descriptive data of the SC-SSS Questionnaire and the SF-36.
RELIABILITY Homogeneity
Cronbach α values of symptom severity and physical function domains of SC-SSS Questionnaire were 0.89 and 0.86, respectively, which was greater than 0.7, indicating excellent internal consistency.
Reproducibility Thirty-two patients were randomly selected to complete the second assessment by phone or e-mail in the interval of 3 to 5 days. The first test of symptom severity domain was 3.36 ± 0.92 with 3.32 ± 0.79 of the second time; the ICC of test–retest reliability was excellent and reached 0.93 (95% 822
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TABLE 1. Demographic Data of the First Survey Inpatients Outpatients Sex (male/female)
Total
13/17
44/31
57/48
58.0 (6.7)
59.3 (7.6)
58.9 (7.4)
Pain or numbness (mo) 39.4 (76.2) Occupation
42.2 (80.5)
41.1 (78.9)
Age (yr)
Workers
14
20
34
Farmers
6
34
40
Teachers
0
5
5
Merchants
3
8
11
Office-bearer
4
4
8
Others
3
4
7
confidence interval: 0.86–0.97). The first test of physical function domain was 2.57 ± 0.83 with 2.52 ± 0.73 of the second time. The ICC of test–retest reliability was also excellent and reached 0.91 (95% confidence interval: 0.82–0.95). The results are shown in Table 3.
Validity Concurrent validity of SC-SSS Questionnaire domains when compared with SF-36 domains is described in Table 4. Excellent (r = 0.75–1) (0 domain), good (r = 0.50–0.75)
TABLE 2. Descriptive Data of the SC-SSS
Questionnaire and the SF-36 (n = 105) Mean ± SD
Range (Minimum– Maximum)
Symptom severity
2.9 ± 0.9
1.4–4.7
Physical function
2.4 ± 0.8
1–4
Physical functioning
76.4 ± 24.2
0–100
Role-physical
49.5 ± 41.6
0–100
Bodily pain
69.9 ± 19.5
30–100
General health
64.1 ± 15.4
25–92
Vitality
63.8 ± 13.9
20–85
Social functioning
75.6 ± 16.3
10–100
Role-emotional
33.0 ± 35.9
0–100
Mental health
59.6 ± 20.0
16–92
Domain SC-SSS Questionnaire
SF-36
SC-SSS Questionnaire indicates simplified Chinese version of Swiss Spinal Stenosis Questionnaire; SF-36, 36-Item Short Form Health Survey.
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HEALTH SERVICES RESEARCH
Validation of Simplified Chinese SSS • Yi et al
TABLE 3. Test–Retest Reproducibility of Domain
Scores as Determined by ICC (n = 32)
SC-SSS Questionnaire
First Test
Second Test
ICC
Symptom severity
3.36 ± 0.92 3.32 ± 0.79
0.93 (0.86–0.97)
Physical function
2.57 ± 0.83 2.52 ± 0.73
0.91 (0.82–0.95)
SC-SSS Questionnaire indicates simplified Chinese version of Swiss Spinal Stenosis Questionnaire; ICC, intraclass coefficient.
(9 domains), moderate (r = 0.25–0.50) (7 domains), and poor (r = 0–0.25) (0 domain) correlations were observed.
Satisfaction Domain This domain is to assess the outcome of the operative patients. Thirty inpatients from the initial group were selected to complete the test. One of them was lost to follow-up. The rest of the cases, 12 males and 17 females with average age of 58 years, were followed for an average of 13 months through the e-mail and telephone. Cronbach α value was 0.90, whereas ICC was 0.92. Symptom severity scale score was 3.42 ± 0.92 before the surgery and 2.20 ± 0.69 after the surgery. Physical function domain score was 2.64 ± 0.84 before the surgery and 1.84 ± 0.57 after the surgery. Satisfaction scale score was highly correlated with the change in the symptom severity (r = −0.678) and physical function scale (r = −0.681).
DISCUSSION The outcomes of illness and treatment in musculoskeletal diseases are problematic for researchers, clinicians, and policy makers. Musculoskeletal illnesses are often chronic and rarely fatal. Precise and reliable assessment of pain, functional status, and satisfaction with care are crucial in measurement of these outcomes. As a result, multiple function questionnaires evaluating low back pain and walking ability are currently available, including Roland–Morris Disability Questionnaire, ODI, Functional Rating Index, VAS, and so on. But all of these are not spinal stenosis–specific scales. They cannot be used to assess exactly the patients with pain, numbness, walking limitation, and trunk imbalance due to the LSS. The questionnaire developed by Stucki et al6 represents a
substantial advancement in our ability to assess the outcomes of LSS among the elderly. It has been widely used all over the world because it is disease-specific, simple to score, and follow up. However, SC version of SSS Questionnaire has not been reported yet. In this study, the questionnaire is translated, back translated, modified, and predicted in accordance with the guidelines by Beaton et al.16 To respect the expression of the original scale, some of the culturally relevant modifications to syntactical construction, word choice, and equivocal terminologies have been made according to Chinese tradition. For example, the term “block” is defined in Wikipedia as the smallest area that is surrounded by streets. The distance of block varies from each other. There is no corresponding word in Chinese. So, it was redefined as “100 meters.” For the same reason, “two miles” was redefined as “3 kilometers.” To summarize, the original questionnaire was translated and adapted on the basis of the different cultural background to help avoid mistaken interpretation and measurement. In this study, patients come from 2 representative medical centers, a general hospital in developed regions in eastern coast and a primary hospital in an inland underdeveloped region. Even more, this study included not only operative patients but also conservatively managed patients. This is very different from other studies. Both of these can effectively prevent the bias from the same kind of population in single center. In this study, Cronbach α values of symptom severity and physical function domains were 0.89 and 0.86, respectively, showing excellent internal consistency, in agreement with the values reported by Stucki et al6 (0.64, 0.82), Pratt et al8 (0.84, 0.89), and Thornes et al9 (0.96, 0.94). The ICCs of these 2 domains were 0.93 and 0.91, respectively, which were the same as reported by other authors: Stucki et al6 (0.94, 0.94), Prat et al8 (0.82, 0.93), and Thornes et al9 (0.92, 0.89). To evaluate test– retest reliability, it is generally suggested that the time period between repeated administrations be long enough to prevent recall but short enough to ensure that clinical change has not occurred. No definitive time interval has been experimentally determined, and 2 days to 2 weeks are often considered to be appropriate.19 All of these test–retest studies were carried out with a time interval of 3 to 5 days, because the inpatients cannot wait for longer time to finish the tests. From the results of this study, it did not affect the test–retest reliability. Several studies have compared the SSS Questionnaire with the ODI and the VAS, showing that there was a significant
TABLE 4. Concurrent Validity of SC-SSS Questionnaire Domains With SF-36 Domains by Pearson
Correlation Coefficients (n = 105)
SC-SSS Questionnaire
SF-36
PF
RP
BP
GH
VT
SF
RE
MH
Symptom severity
−0.685*
−0.663*
−0.391*
−0.653*
−0.403*
−0.494*
−0.500*
−0.398*
−0.289*
Physical function
−0.700*
−0.637*
−0.371*
−0.531*
−0.431*
−0.572*
−0.523*
−0.410*
−0.311*
*P < 0.05. SC-SSS Questionnaire indicates simplified Chinese version of Swiss Spinal Stenosis Questionnaire; SF-36, 36-Item Short Form Health Survey; PF, physical functioning; RP, role-physical; BP, bodily pain; GH, general health; VT, vitality; SF, social functioning; RE, role-emotional; MH, mental health.
Spine
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HEALTH SERVICES RESEARCH correlation between them. In this study, symptom severity domain was highly correlated with physical functioning and bodily pain of SF-36, with Pearson correlation coefficients of 0.663 and 0.653, respectively, whereas it was poorly correlated with MH (r = 0.289). Physical function domain was highly correlated with physical functioning (r = 0.637). That was comparable with the results of the original study. The low correlation coefficient with MH is due to the lack of psychology and sociology questions in the original SSS Questionnaire. In addition, Cronbach α and ICC of the satisfaction domain of SC-SSS Questionnaire were 0.90 and 0.92, respectively, showing good repeatability and internal consistency. It was also highly correlated with the change in the symptom severity (r = −0.678) and physical function scale (r = −0.681), in the agreement with other studies.6 This indicated that the scale of satisfaction can be more intuitive to reflect the operative outcomes and can also be a very good reflection of the improvement in symptom severity and physical function after treatment. The structure of this particular study also generated new data. First, the symptom severity domain score for all patients was 2.9 ± 0.9 but it was 3.4 ± 0.9 for inpatients. The physical function domain score for all patients was 2.4 ± 0.8, and 2.6 ± 0.8 for inpatients. Therefore, the decision to perform surgery does not depend only on patients’ radiological films but also on patients’ subjective complaints. There are some limitations of this study. First, imaging findings should be correlated with both the severity of LSS and the SC-SSS Questionnaire score. In this study, radiological evaluations including radiography, computed tomography, or magnetic resonance imaging were taken into account whenever possible to make precise diagnosis. However, there was a lack of statistical analysis between the SC-SSS Questionnaire score and the imaging. Further study of the correlation analysis between SC-SSS Questionnaire score and radiological evaluations is advocated in patients with LSS. Second, we carried out only a limited number of tests for this validation study. In the future, it may be necessary to perform other tests to establish stronger psychometric indexes for the SC-SSS Questionnaire. Therefore, we recommend using recognized clinical measures for known group comparison. Perhaps performing factor analysis might also help establish further psychometric evidence for the questionnaire. However, our main recommendation is to use simple and straightforward procedures to make technical issues understandable for clinicians as we did in this study.
CONCLUSION The English SSS Questionnaire was successfully translated into SC-SSS Questionnaire and culturally adapted for use in mainland China. The SC-SSS Questionnaire is easy to understand and quick to complete. The psychometric properties of the original version are maintained. The SC-SSS Questionnaire has good homogeneity, reproducibility, and discriminative and construct validity. We suggest that the SC-SSS Questionnaire can be widely used for assessing function in patients with LSS in mainland China. 824
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➢ Key Points SSS questionnaire is culturally adapted to Chinese (SC-SSS) for measurement of degenerative LSS in mainland China. The SC-SSS Questionnaire is easy to understand and quick to complete, so it is practical for wide use in clinical practice. The SC-SSS Questionnaire shows excellent homogeneity, reproducibility, and discriminative and construct validity. We find that the decision to perform surgery does not depend only on patients’ radiological films but also on patients’ subjective complaints.
Acknowledgments Honglei Yi, Xianzhao Wei, Wei Zhang, and Ziqiang Chen contributed equally to this study. Supplemental digital content is available for this article. Direct URL citation appearing in the printed text is provided in the HTML and PDF version of this article on the journal’s web site (www.spinejournal.com).
References
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HEALTH SERVICES RESEARCH 12. Siddiqui M, Smith FW, Wardlaw D. One-year results of X STOP interspinous implant for the treatment of lumbar spinal stenosis. Spine 2007;32:1345–8. 13. Tomkins-Lane CC, Battié MC. Validity and reproducibility of selfreport measures of walking capacity in lumbar spinal stenosis. Spine 2010;35:2097–102. 14. Fokter SK, Yerby SA. Patient-based outcomes for the operative treatment of degenerative lumbar spinal stenosis. Eur Spine J 2006;15:1661–9. 15. Watters WC, III, Baisden J, Gilbert TJ, et al. Degenerative lumbar spinal stenosis: an evidence-based clinical guideline for the diagnosis and treatment of degenerative lumbar spinal stenosis. Spine J 2008;8: 305–10.
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16. Beaton D, Bombardier C, Guillemin F, et al. Guidelines for the process of cross-cultural adaptation of self-report measures. Spine 2000;25:3186–91. 17. Wei X, Zhu X, Bai Y, et al. Development of the Simplified Chinese Version of the Spinal Appearance Questionnaire: cross-cultural adaptation and psychometric properties evaluation. Spine (Phila Pa 1976) 2012;37:1497–504. 18. Li L, Wang H, Shen Y. Development and psychometric tests of a Chinese version of the SF-36 Health Survey Scales. Zhonghua Yu Fang Yi Xue Za Zhi 2002;36:109–13. 19. Streiner DL, Norman GR. Health Measurement Scales. A Practical Guide to Their Development and Use. 2nd ed. New York, NY: Oxford University Press; 1995.
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HEALTH SERVICES RESEARCH
Reliability and Validity of Simplified Chinese Version of Swiss Spinal Stenosis Questionnaire for Patients With Degenerative Lumbar Spinal Stenosis Honglei Yi, MD,*† Xianzhao Wei, MD,* Wei Zhang, MD,‡ Ziqiang Chen, MD,* Xinhui Wang, MD,† Xinran Ji, MD,* Xiaodong Zhu, MD,* Fei Wang, MM,* Ximing Xu, MD,* Zhikun Li, MM,* Jianping Fan, MM,* Chuanfeng Wang, MM,* Kai Chen, MM,* Guoyou Zhang, MD,* Yinchuan Zhao, MD,* and Ming Li, MD*
Study Design. This was a prospective clinical validation study. Objective. To evaluate the reliability and validity of the adapted simplified Chinese version of Swiss Spinal Stenosis (SC-SSS) Questionnaire. Summary of Background Data. The SSS Questionnaire is a reliable and valid instrument to assess the perception of function and pain for patients with degenerative lumbar spinal stenosis. However, there is no culturally adapted SSS Questionnaire for use in mainland China. Methods. This was a prospective clinical validation study. The adaption was conducted according to International Quality of Life Assessment Project guidelines. To examine the psychometric properties of the adapted SC-SSS Questionnaire, a sample of 105 patients with lumbar spinal stenosis were included. Thirtytwo patients were randomly selected to evaluate the test-retest reliability. Reliability assessment of the SC-SSS Questionnaire was determined by calculating Cronbach α and intraclass coefficient values. Concurrent validity was assessed by correlating SC-SSS Questionnaire scores with relevant domains of the 36-Item Short Form Health Survey. Results. Cronbach α of the symptom severity scale, physical function scale, patients, and satisfaction scale of SC-SSS Questionnaire are 0.89, 0.86, 0.91, respectively, which revealed
From the *Department of Orthopaedic Surgery, The Affiliated Changhai Hospital of the Second Military Medical University, Shanghai, China; †89th Hospital of PLA, Weifang, Shandong, China; and ‡Department of Orthopaedics, 401th Hospital of PLA, Qingdao, Shandong, China. Acknowledgment date: July 22, 2013. First revision date: January 7, 2014. Acceptance date: February 2, 2014. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of this work. No relevant financial activities outside the submitted work. Address correspondence and requests for reprints to Ming Li, MD, Orthopedic Department of Changhai Hospital, Second Military Medical University. No 168, Changhai Rd, Shanghai, People’s Republic of China; E-mail: [email protected] DOI: 10.1097/BRS.0000000000000273
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very good internal consistency. The test–retest reproducibility was found to be excellent with the intraclass correlation coefficient of 0.93, 0.91, and 0.95. In terms of concurrent validity, SC-SSS Questionnaire had good correlation with physical functioning and bodily pain of 36-Item Short Form Health Survey (r = 0.663, 0.653) and low correlation with mental health (r = 0.289). The physical function scale had good correlation with physical functioning of 36-Item Short Form Health Survey (r = 0.637), whereas the rest had moderate correlation. The satisfaction scale score was highly correlated with the change in the symptom severity (r = 0.71) and physical function (r = 0.68) scale score. Conclusion. The SC-SSS Questionnaire showed satisfactory reliability and validity in the evaluation of functionality in patients with lumbar spinal stenosis who are experiencing neurogenic claudication. It is simple and easy to use and can be recommended in clinical and research practice in mainland China. Key words: lumbar spinal stenosis, Swiss Spinal Stenosis Questionnaire, Chinese, reliability, validity. Level of Evidence: 3 Spine 2014;39:820–825
D
egenerative lumbar spinal stenosis (LSS) refers to narrowing of the osteoligamentous vertebral canal and/ or the intervertebral foramina causing compression of the thecal sac and/or the caudal nerve roots, with the symptoms of intermittent claudication, radicular pain, paresthesia, and weakness of the legs, as described by Postacchini.1 To quantitatively measure the intensity of low back pain, a variety of subjective evaluation instruments in the past 20 years, such as visual analogue scale (VAS), Oswestry Disability Index (ODI),2 Functional Rating Index,3 Roland–Morris Disability Questionnaire,4 and Quebec Back Pain Disability Scale,5 have been created. However, none of these are spinal stenosis-specific. When VAS is applied, walking capacity cannot necessarily be assessed. In addition, although the ODI can assess the intensity of pain and restrictions in activities of daily living, including walking capacity due to pain, it cannot sufficiently assess symptoms other than pain. As a result,
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HEALTH SERVICES RESEARCH with the currently available questionnaires, there are limits to comprehensively assessing the severity of LSS symptoms. Therefore, Stucki et al6 developed a short spinal stenosisspecific outcome measure in 1996, which was named Swiss Spinal Stenosis (SSS) Questionnaire consisting of symptom severity, physical function, and satisfaction scales. Stucki et al describe explicitly how the measurement was developed, how the items in each scale were chosen, and how to calculate the score of the scales. The minimum score is 13 and the highest is 59. The higher the score is, the more serious the patient’s dysfunction. In recent years, SSS Questionnaire has been widely applied in many publications as a very popular tool because of its disease-specific measurement.7–14 Therefore, the North American Spine Society recommended that this questionnaire be considered as a potential “gold standard” in future studies of specific outcome measures for the treatment of LSS.15 SSS Questionnaire has been translated to several languages in Norway, Switzerland, Slovenia, and other countries.7–14 As far as we know, there is no simplified Chinese (SC) version yet. Therefore, the purpose of this study was to develop and adapt SSS Questionnaire into SC and assess the reliability and validity among Chinese patients with LSS.
MATERIALS AND METHODS The Questionnaire The SSS Questionnaire is a specific measure of functionality in patients with LSS. It includes symptom severity, physical function, and satisfaction scales. The 7 questions of symptom severity addressed overall pain, pain frequency, back pain, leg pain, numbness, weakness, and trunk balance. All but 1 item (1–5) had Likert response scales with 5 categories scored. Balance disturbance had 3 categories and was transformed to 1–3–5 scale. The 6 physical function questions asked about walking distance and ability to walk for pleasure, for shopping, for getting around the house or apartment, and from bathroom to bedroom. All but 1 item had scales with 4 categories (no, could not perform; yes, but always with pain; yes, but sometimes with pain; yes, comfortably). The 4 categories of walking distance were more than 2 miles, more than 2 blocks but less than 2 miles, more than 50 ft but less than 2 blocks, and less than 50 ft. The possible range of scores is 1 to 4. The scale score was calculated as the unweighted mean of all answered items in the questionnaire except that more than 2 items were missing. The satisfaction questions asked about patient satisfaction with the overall results of the spinal surgery; pain relief after the surgery; walking ability after the surgery; ability to do housework or yard work or job after the surgery; strength in the thighs, legs, or feet; and balance or steadiness on feet. These questions had Likert response scales with the 4 categories: very satisfied, somewhat satisfied, somewhat dissatisfied, and very dissatisfied. The range of the scale scores is 1 to 4. The satisfaction scale score was the unweighted mean of all 6 items if the number of responses exceeded 4.6 Spine
Validation of Simplified Chinese SSS • Yi et al
Translation According to international guidelines recommended by Beaton et al16 the procedure of cross-cultural adaptation of the SC-SSS Questionnaire was similar to our previous studies.3–5,17 The original English SSS Questionnaire was translated into SC by 2 bilingual translators of 1 native Chinese-speaking spine surgeon and 1 nonmedical worker. They independently performed the forward translation to SC. After comparing the translations, discrepancies were identified and reconciled by consensus. The backward translation was performed by 2 independent native English speakers with Chinese as their second language, who were blinded to the study purpose. Both translators lacked medical background and were unaware of the prior translation procedures or the original document. Each English translation was compared with the original English SSS Questionnaire and checked for inconsistencies by the translation team. Then, the team consolidated the original questionnaire, translations, back translations, and corresponding written reports to reach a consensus. Before finalizing, the SC-SSS Questionnaire was pilot tested in 44 patients with LSS. Each patient completed the SC-SSS Questionnaire and was subsequently interviewed about any difficulties in completing the questionnaire or understanding the purpose and meaning of each question. The team discussed all the findings and then developed the final SC-SSS Questionnaire (see Supplemental Digital Content, Appendix, available at http://links.lww.com/BRS/A858), which was subjected to further psychometric testing.
Participants To examine the psychometric properties and clinical application of the adapted SC-SSS Questionnaire, a survey was conducted in a group of randomly selected 118 outpatients and inpatients in Changhai Hospital of Shanghai and 89th Military Hospital of Shandong. These patients are all diagnosed with LSS by attending doctors. All patients filled in the SC-SSS Questionnaire and a previously validated Chinese (Mainland) version of the 36-Item Short Form Health Survey (SF-36) in the hospital with a consent form. Three to 5 days after their first survey, some of patients were asked to complete the tests again by phone or e-mail. The SF-36 is a brief self-administered questionnaire derived from an aggregate of items included in the RAND/Medical Outcomes Study. The categories of health tested included physical functioning, role limitations due to physical problems, bodily pain, general health, vitality, social functioning, role limitations due to emotional problems, mental health (MH), and 1 single-item scale on health transition. When functioned in Hangzhou, China, results are near equivalent to those when tested in an American Chinese or Hong Kong populations.18 Inclusion criteria were as follows: (1) more than 50 years of age; (2) low back pain, lower limbs numbness, and pain aggravated after the extension of the body; (3) hyperplasia of facet joint, hypertrophy of yellow ligament, bulge or herniation of the intervertebral disc, and oppressive nerve had been www.spinejournal.com
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HEALTH SERVICES RESEARCH proven by the films; and (4) the patient received at least 6-year compulsory education and accurately understood the questionnaire. Exclusion criteria included trauma, tumor, inflammation, or history of lumbar spine surgery. Ethical approval from the research committee of the author’s institution and participation consent were obtained.
Reliability and Validity Reliability assessment of the SC-SSS Questionnaire was determined by calculating Cronbach α and intraclass coefficient (ICC) values as previously described. Concurrent validity was evaluated by comparing SC-SSS Questionnaire domains with relevant domains of the SF-36 questionnaire; correlation was made using Pearson correlation coefficients (r).
Statistical Analysis SPSS version 13.0 (SPSS, Statistical Package for the Social Sciences) for Windows was used for all statistical analyses. Data were expressed as the mean ± SD and were analyzed using a Pearson correlation method with the level of significance P < 0.05.
RESULTS A total of 105 patients with LSS completed the questionnaires from December 2008 to April 2009. All patients came from 2 regions representing different economic development degrees: a general hospital in developed regions in eastern coast (Changhai Hospital) and a primary hospital in an inland underdeveloped region (the 89th military hospital). Of these patients, 75 outpatients decided to have nonsurgical treatment, whereas 30 inpatients were ready for surgery. Table 1 shows their age, sex, pain or numbness duration, and occupational level. All of the patients completed the physical function and symptom severity domains of SC-SSS Questionnaire within 3 minutes, whereas 29 of the inpatients finished satisfaction questions of SC-SSS Questionnaire within 1 minute, average 13 months after the surgical procedures. All of the patients completed the SF-36 test. Table 2 summarizes the descriptive data of the SC-SSS Questionnaire and the SF-36.
RELIABILITY Homogeneity
Cronbach α values of symptom severity and physical function domains of SC-SSS Questionnaire were 0.89 and 0.86, respectively, which was greater than 0.7, indicating excellent internal consistency.
Reproducibility Thirty-two patients were randomly selected to complete the second assessment by phone or e-mail in the interval of 3 to 5 days. The first test of symptom severity domain was 3.36 ± 0.92 with 3.32 ± 0.79 of the second time; the ICC of test–retest reliability was excellent and reached 0.93 (95% 822
Validation of Simplified Chinese SSS • Yi et al
TABLE 1. Demographic Data of the First Survey Inpatients Outpatients Sex (male/female)
Total
13/17
44/31
57/48
58.0 (6.7)
59.3 (7.6)
58.9 (7.4)
Pain or numbness (mo) 39.4 (76.2) Occupation
42.2 (80.5)
41.1 (78.9)
Age (yr)
Workers
14
20
34
Farmers
6
34
40
Teachers
0
5
5
Merchants
3
8
11
Office-bearer
4
4
8
Others
3
4
7
confidence interval: 0.86–0.97). The first test of physical function domain was 2.57 ± 0.83 with 2.52 ± 0.73 of the second time. The ICC of test–retest reliability was also excellent and reached 0.91 (95% confidence interval: 0.82–0.95). The results are shown in Table 3.
Validity Concurrent validity of SC-SSS Questionnaire domains when compared with SF-36 domains is described in Table 4. Excellent (r = 0.75–1) (0 domain), good (r = 0.50–0.75)
TABLE 2. Descriptive Data of the SC-SSS
Questionnaire and the SF-36 (n = 105) Mean ± SD
Range (Minimum– Maximum)
Symptom severity
2.9 ± 0.9
1.4–4.7
Physical function
2.4 ± 0.8
1–4
Physical functioning
76.4 ± 24.2
0–100
Role-physical
49.5 ± 41.6
0–100
Bodily pain
69.9 ± 19.5
30–100
General health
64.1 ± 15.4
25–92
Vitality
63.8 ± 13.9
20–85
Social functioning
75.6 ± 16.3
10–100
Role-emotional
33.0 ± 35.9
0–100
Mental health
59.6 ± 20.0
16–92
Domain SC-SSS Questionnaire
SF-36
SC-SSS Questionnaire indicates simplified Chinese version of Swiss Spinal Stenosis Questionnaire; SF-36, 36-Item Short Form Health Survey.
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HEALTH SERVICES RESEARCH
Validation of Simplified Chinese SSS • Yi et al
TABLE 3. Test–Retest Reproducibility of Domain
Scores as Determined by ICC (n = 32)
SC-SSS Questionnaire
First Test
Second Test
ICC
Symptom severity
3.36 ± 0.92 3.32 ± 0.79
0.93 (0.86–0.97)
Physical function
2.57 ± 0.83 2.52 ± 0.73
0.91 (0.82–0.95)
SC-SSS Questionnaire indicates simplified Chinese version of Swiss Spinal Stenosis Questionnaire; ICC, intraclass coefficient.
(9 domains), moderate (r = 0.25–0.50) (7 domains), and poor (r = 0–0.25) (0 domain) correlations were observed.
Satisfaction Domain This domain is to assess the outcome of the operative patients. Thirty inpatients from the initial group were selected to complete the test. One of them was lost to follow-up. The rest of the cases, 12 males and 17 females with average age of 58 years, were followed for an average of 13 months through the e-mail and telephone. Cronbach α value was 0.90, whereas ICC was 0.92. Symptom severity scale score was 3.42 ± 0.92 before the surgery and 2.20 ± 0.69 after the surgery. Physical function domain score was 2.64 ± 0.84 before the surgery and 1.84 ± 0.57 after the surgery. Satisfaction scale score was highly correlated with the change in the symptom severity (r = −0.678) and physical function scale (r = −0.681).
DISCUSSION The outcomes of illness and treatment in musculoskeletal diseases are problematic for researchers, clinicians, and policy makers. Musculoskeletal illnesses are often chronic and rarely fatal. Precise and reliable assessment of pain, functional status, and satisfaction with care are crucial in measurement of these outcomes. As a result, multiple function questionnaires evaluating low back pain and walking ability are currently available, including Roland–Morris Disability Questionnaire, ODI, Functional Rating Index, VAS, and so on. But all of these are not spinal stenosis–specific scales. They cannot be used to assess exactly the patients with pain, numbness, walking limitation, and trunk imbalance due to the LSS. The questionnaire developed by Stucki et al6 represents a
substantial advancement in our ability to assess the outcomes of LSS among the elderly. It has been widely used all over the world because it is disease-specific, simple to score, and follow up. However, SC version of SSS Questionnaire has not been reported yet. In this study, the questionnaire is translated, back translated, modified, and predicted in accordance with the guidelines by Beaton et al.16 To respect the expression of the original scale, some of the culturally relevant modifications to syntactical construction, word choice, and equivocal terminologies have been made according to Chinese tradition. For example, the term “block” is defined in Wikipedia as the smallest area that is surrounded by streets. The distance of block varies from each other. There is no corresponding word in Chinese. So, it was redefined as “100 meters.” For the same reason, “two miles” was redefined as “3 kilometers.” To summarize, the original questionnaire was translated and adapted on the basis of the different cultural background to help avoid mistaken interpretation and measurement. In this study, patients come from 2 representative medical centers, a general hospital in developed regions in eastern coast and a primary hospital in an inland underdeveloped region. Even more, this study included not only operative patients but also conservatively managed patients. This is very different from other studies. Both of these can effectively prevent the bias from the same kind of population in single center. In this study, Cronbach α values of symptom severity and physical function domains were 0.89 and 0.86, respectively, showing excellent internal consistency, in agreement with the values reported by Stucki et al6 (0.64, 0.82), Pratt et al8 (0.84, 0.89), and Thornes et al9 (0.96, 0.94). The ICCs of these 2 domains were 0.93 and 0.91, respectively, which were the same as reported by other authors: Stucki et al6 (0.94, 0.94), Prat et al8 (0.82, 0.93), and Thornes et al9 (0.92, 0.89). To evaluate test– retest reliability, it is generally suggested that the time period between repeated administrations be long enough to prevent recall but short enough to ensure that clinical change has not occurred. No definitive time interval has been experimentally determined, and 2 days to 2 weeks are often considered to be appropriate.19 All of these test–retest studies were carried out with a time interval of 3 to 5 days, because the inpatients cannot wait for longer time to finish the tests. From the results of this study, it did not affect the test–retest reliability. Several studies have compared the SSS Questionnaire with the ODI and the VAS, showing that there was a significant
TABLE 4. Concurrent Validity of SC-SSS Questionnaire Domains With SF-36 Domains by Pearson
Correlation Coefficients (n = 105)
SC-SSS Questionnaire
SF-36
PF
RP
BP
GH
VT
SF
RE
MH
Symptom severity
−0.685*
−0.663*
−0.391*
−0.653*
−0.403*
−0.494*
−0.500*
−0.398*
−0.289*
Physical function
−0.700*
−0.637*
−0.371*
−0.531*
−0.431*
−0.572*
−0.523*
−0.410*
−0.311*
*P < 0.05. SC-SSS Questionnaire indicates simplified Chinese version of Swiss Spinal Stenosis Questionnaire; SF-36, 36-Item Short Form Health Survey; PF, physical functioning; RP, role-physical; BP, bodily pain; GH, general health; VT, vitality; SF, social functioning; RE, role-emotional; MH, mental health.
Spine
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HEALTH SERVICES RESEARCH correlation between them. In this study, symptom severity domain was highly correlated with physical functioning and bodily pain of SF-36, with Pearson correlation coefficients of 0.663 and 0.653, respectively, whereas it was poorly correlated with MH (r = 0.289). Physical function domain was highly correlated with physical functioning (r = 0.637). That was comparable with the results of the original study. The low correlation coefficient with MH is due to the lack of psychology and sociology questions in the original SSS Questionnaire. In addition, Cronbach α and ICC of the satisfaction domain of SC-SSS Questionnaire were 0.90 and 0.92, respectively, showing good repeatability and internal consistency. It was also highly correlated with the change in the symptom severity (r = −0.678) and physical function scale (r = −0.681), in the agreement with other studies.6 This indicated that the scale of satisfaction can be more intuitive to reflect the operative outcomes and can also be a very good reflection of the improvement in symptom severity and physical function after treatment. The structure of this particular study also generated new data. First, the symptom severity domain score for all patients was 2.9 ± 0.9 but it was 3.4 ± 0.9 for inpatients. The physical function domain score for all patients was 2.4 ± 0.8, and 2.6 ± 0.8 for inpatients. Therefore, the decision to perform surgery does not depend only on patients’ radiological films but also on patients’ subjective complaints. There are some limitations of this study. First, imaging findings should be correlated with both the severity of LSS and the SC-SSS Questionnaire score. In this study, radiological evaluations including radiography, computed tomography, or magnetic resonance imaging were taken into account whenever possible to make precise diagnosis. However, there was a lack of statistical analysis between the SC-SSS Questionnaire score and the imaging. Further study of the correlation analysis between SC-SSS Questionnaire score and radiological evaluations is advocated in patients with LSS. Second, we carried out only a limited number of tests for this validation study. In the future, it may be necessary to perform other tests to establish stronger psychometric indexes for the SC-SSS Questionnaire. Therefore, we recommend using recognized clinical measures for known group comparison. Perhaps performing factor analysis might also help establish further psychometric evidence for the questionnaire. However, our main recommendation is to use simple and straightforward procedures to make technical issues understandable for clinicians as we did in this study.
CONCLUSION The English SSS Questionnaire was successfully translated into SC-SSS Questionnaire and culturally adapted for use in mainland China. The SC-SSS Questionnaire is easy to understand and quick to complete. The psychometric properties of the original version are maintained. The SC-SSS Questionnaire has good homogeneity, reproducibility, and discriminative and construct validity. We suggest that the SC-SSS Questionnaire can be widely used for assessing function in patients with LSS in mainland China. 824
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➢ Key Points SSS questionnaire is culturally adapted to Chinese (SC-SSS) for measurement of degenerative LSS in mainland China. The SC-SSS Questionnaire is easy to understand and quick to complete, so it is practical for wide use in clinical practice. The SC-SSS Questionnaire shows excellent homogeneity, reproducibility, and discriminative and construct validity. We find that the decision to perform surgery does not depend only on patients’ radiological films but also on patients’ subjective complaints.
Acknowledgments Honglei Yi, Xianzhao Wei, Wei Zhang, and Ziqiang Chen contributed equally to this study. Supplemental digital content is available for this article. Direct URL citation appearing in the printed text is provided in the HTML and PDF version of this article on the journal’s web site (www.spinejournal.com).
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