Abstract
Background:
Shoulder pain is one of the main symptoms of patients treated at orthopaedic clinics. The Constant score (CS) is widely used in the literature to assess shoulder functional outcomes. To the authors’ knowledge, no outcome measure has been related to shoulder complaints in Indonesia.
Purpose:
To perform a translation and cross-cultural adaptation and assess the validity and reliability of the Indonesian CS (CS-INA) as a shoulder functional assessment instrument in Indonesia.
Study Design:
Cohort study (Diagnosis); Level of evidence, 2.
Methods:
After a translation cross-cultural adaptation of the CS into the Indonesian language was performed, the validity and reliability of the CS-INA were investigated. Data from patients with shoulder pain were collected consecutively in the orthopaedic clinic of 2 tertiary hospitals in Jakarta in 2023. The validity and reliability study of the final version of the CS-INA was conducted by 1 researcher in 2 meetings within 1 week. The Indonesian version of the 36-item Short Form Survey (SF-36) questionnaire was also given to the respondents. The correlation between CS-INA and SF-36 was determined to evaluate construct validity, whereas internal consistency, intraclass correlation, standard error of measurement (SEM), and minimal detectable change (MDC) were calculated to provide data on reliability.
Results:
A total of 102 shoulders (101 patients) were included in the study. CS-INA showed excellent construct validity with SF-36 (Pearson correlation 0.90; P < .05). The reliability study showed good internal consistency (Cronbach α = 0.85) and intraclass correlation (ICC = 0.86). The SEM of the test and retest was 7.37, whereas the MDC was 14.3. No floor or ceiling effects were observed in this study.
Conclusion:
The Indonesian version of the Constant score showed good validity and reliability for the Indonesian population experiencing shoulder pain.
Keywords: Constant score, cross-cultural adaptation, validity, reliability
Shoulder pain is one of the most commonly encountered musculoskeletal problems.10,23 In their systematic review, Luime et al 14 showed that shoulder pain occurs in approximately 7% to 26% of adults, with 15 cases per 1000 patients annually. 24 Other studies showed that the prevalence of chronic shoulder pain (symptoms for >6 months) reached 41%.18,19 Most shoulder pain is caused by rotator cuff pathology, with other causes including impingement and capsular tissue pathology, biceps tendon pathology, acromioclavicular arthritis, glenohumeral arthritis, or cervical radicular pain.10,25 In evidence-based medicine, the assessment of these complaints is often carried out using patient-reported outcome measures (PROMs), which allow the physician to evaluate the treatment effectiveness and benchmarking. 8 More than 30 different instruments have been to measure clinical outcomes of the shoulder, including the American Shoulder and Elbow Surgeons Score, Constant score (CS), and Disabilities of the Arm, Shoulder and Hand. The CS is the only instrument providing both patient- and physician-reported outcome measurements. This instrument consists of 4 scoring components: 2 subjective components of pain and daily function and 2 objective components of shoulder joint range of motion (ROM) and shoulder abduction strength. This English-language questionnaire has been used for >30 years since it was first published in 1987, 5 and the CS has been translated into Danish, Turkish, Arabic, Greek, Brazilian, Spanish, and Chinese.1,3,13,15,17,27 Tests conducted on the translated questionnaires yielded good validity and reliability. The current study aimed to translate and adapt the CS for use in the Indonesian population. The Indonesian version of the CS (CS-INA) is expected to be useful in the evaluation of Indonesian patients with shoulder symptoms in clinical and research settings. We hypothesized that CS-INA would be valid and reliable for use in Indonesian-speaking patients with shoulder pain.
Methods
Ethical approval was obtained from the ethics committee of the Faculty of Medicine, University of Indonesia—Cipto Mangunkusumo Hospital (KET-1136/UN2.F1/ETIK/PPM.00.02/2023), in compliance with the Declaration of Helsinki. Informed consent for the use of participants’ data was obtained during their hospital visits.
A cohort study was performed to test the validity and reliability of CS-INA in patients with shoulder symptoms. The study was conducted at the orthopaedic and traumatology outpatient clinics of 2 tertiary-level hospitals in Jakarta, Indonesia. The study was conducted between January and September 2023. All patients in both hospitals who reported shoulder pain were included consecutively. The inclusion criteria were age >18 years, shoulder pain for at least a month, and ability to speak Indonesian actively and passively. Exclusion criteria were shoulder pain of cervical origin (through clinical examination), fracture, and patients undergoing surgical procedure of the affected shoulder who were still in the postoperative recovery process. We followed the cross-cultural adaptation guidelines published by Guillemin et al 8 and Beaton et al. 2 The sample size of 102 was calculated based on Terwee and colleagues’ 22 recommendation that the minimum sample size needed to produce internal consistency, construct validity, and good reliability while avoiding floor and ceiling effects is at least 100 samples. All patients agreed to participate in the study, and none of them were excluded. Due to a lack of validated shoulder outcome measures in the country, we used a validated Indonesian version of the 36-item Short Form Survey (SF-36) 21 to test the construct validity.
The translation of the CS involved a team of experts who adjusted and consolidated each question in the questionnaire. The expert team in this study included methodologists and orthopaedic surgeons. The expert team reviewed the final version of the CS-INA, which was produced through forward and back translations by certified linguists. The result was a duplicate of the original version, with adjustments to Indonesian cultural terms to make it understandable for lay people.
The CS-INA is a shoulder function assessment questionnaire consisting of 4 sections and 11 items. The subjective part of the questionnaire was completed in <5 minutes, whereas subsequent objective measurements were taken in <10 minutes.
The research team rechecked the questionnaires returned by the correspondents. The objective section of the CS was measured by a single orthopaedic surgeon (J.P.). ROM data were obtained by asking the patients to actively abduct the shoulder joint until pain was limited. Shoulder strength was measured using calibrated and certified dynamometers. Shoulder strength was measured 5 times, and the results were averaged. The completed questionnaire data were entered into the database as follows: pain, 0 to 15 points (mean of items 1 and 2); activities of daily living (ADLs), 0 to 20 points (total of items 3-6); ROM, 0 to 40 points (total of items 7-10); and power, 0 to 25 points (mean of motor strength scores multiplied by 2). Afterward, the patients were given a set of SF-36 questionnaires to assess their current general quality of life. The SF-36 consists of several components: physical function, physical limitations, pain, general health, vitality, social function, emotional limitations, and mental limitations. 12 The data obtained were entered into the research database. The subjective components can yield a maximum of 35 points, whereas the objective components can yield 65 points, culminating in a total possible score of 100 points (optimal performance).
Data Analysis
Data were collected and processed using SPSS Statistics Version 23.0 (IBM). The significance level was set to .05. The distribution of the study participants’ characteristics was processed using univariate analysis. Construct validity was assessed by comparing the points of the questionnaire criteria with the Pearson correlation coefficient of the CS-INA with SF-36. Reliability testing assessed the internal consistency and intraclass correlation coefficient (ICC) to evaluate the test-retest value.
Results
Based on the results of the forward and back translations, the translation of the CS-INA (Figure 1) questionnaire was linguistically and culturally appropriate.
Figure 1.
Sample questionnaire of the adapted version of the Indonesian version of the Constant score.
This study tested the questionnaire on 102 study participants who experienced shoulder symptoms in the previous month. The median age was 53 years (range, 19-83). The respondents were mostly female (60.8%) (Table 1).
Table 1.
Characteristics of Research Participants
| Variables | Frequency (%) a |
|---|---|
| Age, y, median (min-max) | 53 (19-83) |
| Sex | |
| Male | 40 (39.2) |
| Female | 62 (60.8) |
| Job | |
| Working | 40 (39.2) |
| Not working | 56 (54.9) |
| Student | 6 (5.9) |
| Surgery history | |
| Preoperative | 71 (69.6) |
| Postoperative | 31 (30.4) |
| Diagnosis | |
| Rotator cuff injury | 36 (35.3) |
| Glenohumeral arthritis | 10 (9.8) |
| Bicipital tendinitis | 9 (8.8) |
| Adhesive capsulitis | 17 (16.7) |
| Impingement syndrome | 11 (10.8) |
| Shoulder instability | 7 (6.9) |
| Other | 12 (11.8) |
| Shoulder side | |
| Right | 49 (48) |
| Left | 53 (52) |
Data are expressed as n (%) unless otherwise noted.
The measurement results of each question in the CS-INA resulted in a mean total score of 59.2 ± 19.7. The minimum and maximum scores obtained were 16.5 and 96, respectively. The median ADL score was 14 out of a maximum score of 20, whereas the median for ROM was 7 (0-10) for flexion, 7 (0-10) for abduction, 8 (2-10) for external rotation, and 6 (0-10) for internal rotation (Table 2). The median of motoric strength was 9.4 (1-25). The mean score for the SF-36 was 59.7 ± 13.3. All components had an uneven distribution (Table 3).
Table 2.
CS-INA Outcomes in Research Participants a
| Component | Median (min-max) |
|---|---|
| Pain | 10 (0-14) |
| ADLs | 14 (4-20) |
| Work | 2 (0-4) |
| Recreation | 2 (0-4) |
| Sleep | 1 (0-2) |
| Position | 8 (4-10) |
| Range of motion / joint scope of motion | 26 (6-40) |
| Flexion | 7 (0-10) |
| Abduction | 7 (0-10) |
| External rotation | 8 (2-10) |
| Internal rotation | 6 (0-10) |
| Power | 9.4 (1-25) |
| Total, mean ± SD | 59.17 ± 19.7 |
Data are presented as median (min-max) unless otherwise noted. ADLs, activities of daily living; CS-INA, Indonesian version of the Constant score.
Table 3.
SF-36 Outcomes in Research Participants
| Component | Median (min-max) a |
|---|---|
| Physical function | 72.5 (10-100) |
| Physical limitations | 50 (0-100) |
| Pain | 55 (0-90) |
| General health | 50 (15-80) |
| Vitality | 55 (20-80) |
| Social function | 56.5 (13-88) |
| Emotional limitations | 100 (33-100) |
| Mental health | 68 (28-92) |
| Total, mean ± SD | 59.7 ± 13.3 |
Data are presented as median (min-max) unless otherwise noted.
The reliability or consistency test was carried out with internal consistency and test-retest consistency. The internal consistency test was conducted using the Cronbach α test. In the test of repeatability consistency, an ICC test was conducted to assess consistency. The standard error of measurement (SEM) and minimal detectable changes (MDCs) were also evaluated. The reliability of the CS-INA was considered excellent, with a Cronbach α of 0.856 (Table 4).
Table 4.
Reliability Test With Cronbach α and ICC a
| Mean ± SD | SEM | MDC | ||
|---|---|---|---|---|
| Internal consistency | Cronbach α 0.86 | |||
| Test | 59.1 ± 19.7 | 7.37 | 14.4 | |
| Retest | 63.0 ± 20.3 | 6.82 | 13.3 | |
| ICC | 0.902 (0.86-0.93) |
ICC, intraclass correlation coefficient; MDC, minimal detectable change; SEM, standard error of measurement.
We also evaluated the relationship between the CS-INA and SF-36 components to assess the equivalence of the questionnaires. The pain components, ROM–physical function, and power–physical function in both questionnaires were well correlated (R = 0.878, 0.774, and 0.748, respectively). This showed that the CS-INA could reveal the patients’ functional status (Table 5).
Table 5.
Correlation of CS-INA Components and SF-36 Components a
| CS-INA | SF-36 | Correlation Coefficient | P |
|---|---|---|---|
| Pain | Pain | 0.878 | .000 |
| ADLs | Physical limitations | 0.356 | .000 b |
| ROM | Physical function | 0.774 | .000 |
| Power | Physical function | 0.748 | .000 |
| Total | Mental Health | 0.106 | .289 b |
ADLs, activities of daily living; CS-INA, Indonesian version of the Constant score; ROM, range of motion.
Analysis conducted with Pearson test.
Discussion
Overall, the CS-INA can be considered a valid and reliable questionnaire for use in patients with shoulder pain in the Indonesian population. These results are in accordance with previous studies conducted by several researchers in various countries who tested the validity and reliability of the original CS. Previous studies have also obtained significant results, with a Cronbachαα range of 0.73 to 0.93.3-8 The results obtained in this study are in accordance with previous studies with good results.
In this study, a test-retest reliability test was conducted to assess the consistency of the CS-INA questionnaire in measurements at different times. An excellent intraclass correlation with a value of 0.948 was obtained. The measurement results showed that the CS-INA questionnaire was highly consistent in repeated use. Previous studies have shown similar results, with fairly good test-retest outcomes. A study conducted in Turkey showed an intraclass correlation with a value of 0.838 to 0.995, which is in accordance with the results of the current study. 16
SEM and MDC were the other reliability components measured in this study. The SEM in this study was 7.37, and the MDC was 14.4. These results align with a study by Henseler et al 9 regarding MDCs in CS in patients with impingement syndrome and rotator cuff injuries. The study showed SEM results of 8 and MDCs of 17, 18, and 23 in the respective subgroups. 9 Better SEM and MDC values of 4.2 and 11.6, respectively, were found in a study by Moeller et al. 17 This difference is likely due to the different populations measured and the number of patients involved in Moeller's Danish study. Nevertheless, the scores achieved in the current study indicate that the reliability of CS-INA is sufficient to measure SEM and MDC.
The adaptation of CS to the Indonesian population followed 2 steps: translation into the Indonesian language, and the study of its validity and reliability. The construct validity test was conducted by comparing the total value of the CS-INA with the SF-36 questionnaire, which is also used to assess clinical outcomes in research participants. The SF-36 was used as a comparator, as there is no mutual consensus regarding the gold standard in measuring shoulder pain. Nevertheless, SF-36 has been widely used as a comparator in previous studies. Contrary to a study by Yao et al, 27 who found a poor correlation between CS and SF-36, our study showed a strong correlation between CS-INA and SF-36. This difference could be due to the overall low SF-36 score and its components (ie, Physical Component Summary and a Mental Component Summary) in the study by Yao et al.
Although CS can be widely used in assessing shoulder function and has many advantages, it also has some limitations. First, it requires training and expertise, as the effective implementation of CS requires specialized training and experience, potentially limiting its applicability in some contexts.11,20,26 Second, the measurement of shoulder strength requires a certain device that is quite costly and not standardized worldwide, although this problem can be overcome by using calibrated and certificated measurement tools.
This is the first study in Indonesia to validate the adaptation of a PROM for assessing shoulder functional outcomes. The limitations of this study include the fact that there was no validated comparator that was entirely suitable for measuring shoulder outcomes in Indonesia. This indicates the need for further research to develop a more suitable comparator for a more accurate and comprehensive assessment of clinical outcomes in the shoulder. Therefore, this study represents a robust initial achievement in developing this assessment in Indonesia and identifies challenges that can inform future research in this area.
Conclusion
The CS-INA questionnaire has good validity and reliability in assessing the functional status of patients with shoulder pain in Indonesia.
Acknowledgments
The authors thank the clinical staff and patients of Cipto Mangunkusumo Hospital for their participation and support in this study.
Footnotes
Final revision submitted March 31, 2025; accepted April 25, 2025.
The authors have declared that there are no conflicts of interest in the authorship and publication of this contribution. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.
Ethical approval for this study was obtained from the University of Indonesia—Cipto Mangunkusumo Hospital (KET-1136/UN2.F1/ETIK/PPM.00.02/2023).
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