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The conceptually equivalent Dutch version of the Western Ontario Rotator Cuff Index (WORC)©
© Wessel et al.; licensee BioMed Central Ltd. 2013
Received: 31 October 2012
Accepted: 13 December 2013
Published: 21 December 2013
The WORC is a quality of life questionnaire designed for patients with disorders of the rotator cuff, originally developed in English. The purpose of this study was to cross-culturally adapt the WORC for use in the Dutch population and to evaluate reliability, agreement and floor and ceiling effects of this Dutch version in a population of patients with rotator cuff disease.
Reliability was tested by measuring the Cronbach’s alpha for internal consistency and intraclass correlation coefficients (ICC) for test-retest reliability. Agreement was measured using the Standard Error of Measurement (SEMagreement); and the smallest detectable change (SDC) was calculated based on the SEM. Pearson Correlations Coefficients were used to comparing the WORC with the RAND-36, the Constant Score and 11-point shoulder hindrance scale.
Fifty-seven patients entered into this study of whom 50 were available for test-retest validation. The internal consistency of the Dutch WORC tested by Cronbach’s alpha was 0.95 for the total questionnaire. The ICC for the WORC is 0.91 with a 95% confidence interval of 0.85-0.95. Standard Error of Measurement was 6.0 points with a Smallest Detectable Change of 16.7 points on a 0-100 scale. Pearson Correlations Coefficients showed a significant positive correlation between the Dutch WORC and Constant Score (r = 0.60) and a strong reversed correlation with the shoulder hindrance scale (r = -0.75).
The Dutch WORC seems to be a reliable health-related quality of life questionnaire for patients with rotator cuff disorders.
KeywordsWORC Quality of life questionnaires Translation process Validation Rotator cuff repair
Arthroscopic repair of a rotator cuff tear is a procedure that has gained increased interest. Results are reported to be good to excellent in more than 90% of patients [1–9]. There is however no consensus on how to measure success after this procedure. Results can be measured by patient satisfaction, cuff continuity or clinical scores. Examples of widely used outcome measures in rotator cuff repair studies are the Constant Score and the UCLA Shoulder Score. Dutch quality of life measurement tools specifically suitable to investigate patients with diseases of the rotator cuff are lacking in the literature.
Disease specific quality of life measurement tools are essential for evaluating orthopedic healthcare, since the goal of orthopedic surgery is to improve quality of life rather than to prolong a patient’s life . If the questionnaires are self-administered then they are less susceptible to evaluator bias. It is important to measure results from a patient’s point of view rather than from a practitioner’s perspective.
Multiple questionnaires concerning shoulder pathology have been developed [11–19]. The Western Ontario Rotator Cuff index (WORC) and the Rotator Cuff Quality-of-Life Measure (RC-QOL) are disease specific quality of life measurement tools for patients with rotator cuff disease. We chose to translate and validate the WORC, as it was developed for people with rotator cuff disease with well described methodology that included item generation and reduction, scaling and weighting, pretesting, reliability and validation testing . Furthermore, a common international interpretation and analysis of results is only possible if data comes from the same instrument . The WORC has been translated into a number of languages [21–25], which makes this measurement tool appropriate for international comparison of results.
The purpose of this study was to cross-culturally adapt the WORC for use in the Dutch population and to evaluate reliability, agreement and floor and ceiling effects of this Dutch version in a population of patients with rotator cuff disease.
In this prospective study the WORC index was translated and adapted into the Dutch language. After the translation process was completed, the questionnaire was evaluated in a population of patients with rotator cuff disease. It was compared to the RAND-36  and the Constant Score.
The WORC is designed for patients with disorders of the rotator cuff . It is a disease-specific Health Related Quality of Life (HRQL) questionnaire that has 21 items representing 5 domains, each with a visual analogue scale–type response option. The 5 domains are (1) physical symptoms, (2) sports and recreation, (3) work, (4) social function, and (5) emotions. Each item is scored on a 100-mm scale (ranging from 0 best to 100 worst). The most symptomatic total score is 2100, and the best or asymptomatic total score is 0. To present this in a more clinically meaningful format, the score is reported as a percentage by subtracting the total from 2100, dividing by 2100, and multiplying by 100. Total final WORC scores can, therefore, vary from 0%, the lowest functional status level, to 100%, the highest functional status level. In this article both the WORC total and domain scores are expressed as percentages (0-100%).
The RAND 36-Item Health Survey 1.0 (distributed by RAND, ) includes the same items as those found in the SF-36, but with a scoring algorithm that is somewhat different from that of the SF-36 . The RAND-36 is a widely used HRQL survey instrument. It assesses eight health concepts with multi-item scales (35 items): physical functioning (10 items), role limitations caused by physical health problems (4 items), role limitations caused by emotional problems (3 items), social functioning (2 items), emotional well being (5 items), energy/fatigue (4 items), pain (2 items) and general health perceptions (5 items). An additional single item assesses change in perceived health during the last 12 months [26, 28].
The Constant Score has become the most widely used shoulder evaluation instrument in Europe. It is a 100-point scoring system and combines physical examination tests with subjective evaluations by the patients. The subjective assessments of pain and activities of daily living are allocated 15 and 20 points, respectively. A maximum of 40 points is assigned for active range of motion, and 25 points for quantitative measurement of abduction strength [14, 29, 30].
“Forward” translation by two independent translators
Reconciliation meeting between the two “forward” translators and the local project manager
“Backward” translation by an independent translator
Comparison of the source questionnaire with the “backward” translation
List questions and explanations, which have not been translated literally
How much difficulty do you have with someone or something coming in contact with your affected shoulder?
Hoe bang bent u dat iets of iemand tegen uw geblesseerde schouder stoot?
How much difficulty is translates as How afraid are you
How much difficulty do you experience working above your head?
Hoeveel last ervaart u bij het verrichten van werkzaamheden boven schouderhoogte?
Above your head is translated as above shoulder level
Refers to anything that you would do to your hair such as combing, brushing or washing that requires you to reach up with your problematic arm.
Heeft betrekking op alles wat er bij haarverzorging komt kijken, zoals kammen, borstelen of wassen, waarbij u uw aangedane arm moet optillen. Indien u schouderklachten heeft, maar daar geen last van heeft bij de verzorging van uw haar (bijvoorbeeld omdat dat prima gaat met uw andere arm of dat u kalend bent), zet u een streepje links op de lijn.
The explanation was expanded by: If you have shoulder complaints, but they do not bother you when styling your hair (because it goes fine with the other arm) you put a slash left on the line. If you do not experience difficulty styling your hair because your are balding, indicate your difficulty to wash the top of your head
How much difficulty do you have “roughhousing or horsing around” with family or friends?
Hoeveel last hebt u met ‘stoeien en ravotten’ met familie/vrienden vanwege uw schouder?
The explanation was adjusted by adding ‘e.g. grandchildren’
Review by clinicians working in the medical field
After reporting the process and the final translation of the WORC (Additional file 1) we received approval from the author to use this questionnaire for the Dutch population.
Patients above the age of 18 with at least 3 months duration of disorders of the rotator cuff (DRC), including both rotator cuff lesion and non-ruptured disorders of the rotator cuff, were prospectively included in this study. The patients were recruited from the outpatient clinic of the St Antonius Hospital in Utrecht, the Netherlands and had to have two or more of the following signs present: impingement (Neer’s impingement sign or Hawkins-Kennedy impingement sign), painful arc sign, positive Jobe test (supraspinatus), positive infraspinatus test (resistance test with external rotation at the side and in 90 degrees of abduction), positive lift-off/belly press test (resistance test of subscapularis) , positive drop-arm test , or positive Neer impingement test  (subacromial injection with lidocaine). The lesions were confirmed by Magnetic Resonance Imaging (MRI) or arthroscopy. Calcific tendonitis was confirmed on X-ray . Exclusion criteria was previous operations and co-existing pathology such as osteoarthritis, frozen shoulder or instability of the affected shoulder. Patients who had difficulty understanding the Dutch language were also excluded.
The visits for the validation study were scheduled with an independent physical therapist with a two week interval between visits (minimum of one week). During these two visits (T0 and T1), patients filled out the WORC, RAND-36 (general health) and the Constant Score in a separate room with the independent physical therapist in attendance. They were also asked to rate their shoulder hindrance on an 11-point scale from 0 (no hindrance) to 10 points (extreme hindrance). The one to two week test-retest interval was chosen because it was unlikely that the patient’s condition would substantially change, but the time span was large enough for the patients to forget their initial responses to the questions. In order to detect a possible substantial change in the patient’s condition, the shoulder hindrance scale was used. When the difference between T0 and T1 on this scale was more than 2 points, the patient was excluded from the test-retest analysis, regardless if this was caused by natural variation or by an actual change in condition. The protocol was approved by the institutional review board of the St. Antonius Hospital and all patients gave informed consent.
Descriptive statistics were compiled for demographic and clinical characteristics of the study population. Based on the general recommendations for comparing measurement properties, at least 50 patients need to be included . Pearson Correlations Coefficients (r) were used to compare the Dutch WORC with a general quality of life questionnaire (RAND-36), a commonly used clinical shoulder score (Constant Score) and an 11-point shoulder hindrance scale. For this analysis, the data from the first administration (T0) of the questionnaires was used. Floor and ceiling effects were considered to be present if more than 15% of the patients achieved respectively the lowest or highest possible score . If floor or ceiling effects are present, patients with the lowest or highest possible score cannot be distinguished from each other, indicating limited content validity . All data was analyzed with SPSS statistical software (SPSS, Inc., version 19). For statistical analyses, the level of significance was set at 5%.
Agreement and reliability
Cronbach’s alpha coefficients were calculated for internal consistency of the WORC total score and the five domains . An alpha <0.6 indicates a poor internal consistency, 0.7-0.8 acceptable, 0.8-0.9 good and >0.9 excellent internal consistency. High internal consistency indicates a strong correlation between the items, which supports summarizing the items . Intraclass correlation coefficients (ICC) were calculated for test-retest reliability of the WORC total score and the five domains (two-way random effects model, single measurements and absolute agreement) . In general, 0.70 is recommended as a minimum standard for test-retest reliability; a correlation less than 0.5 is described as weak, whereas a correlation greater than 0.8 is described as strong . The 95% confidence interval (CI) for the ICC, the range of values contained with the 95% confidence (the ‘true’ correlation coefficient), were also calculated. Agreement was measured using the Standard Error of Measurement (SEM) calculated as SEMagreement. The larger the SEM, the lower the precision of the instrument. The smallest detectable change (SDC), based on the measurement error, was defined as 1.96 * √2 * SEM .
Demographics of study population (N = 57)
Rotator cuff tear
Operated side (Right/Left)
Dominant side (Right/Left)
Clinical characteristics of study population at the first administration of the questionnaires (N = 57)
54.2 (± 10.8)
Interval T0-T1 (days)
8.6 (± 3.0)
WORC index total
44.2 (± 21.2)
53.9 (± 20.6)
WORC-sports and recreation
38.8 (± 24.1)
33.8 (± 23.8)
39.7 (± 24.8)
51.6 (± 29.1)
36.0 (± 20.6)
7.2 (± 2.0)
71.8 (± 14.4)
67.1 (± 26.2)
23.3 (± 33.4)
63.2 (± 44.4)
75.9 (± 18.0)
61.4 (± 20.6)
42.0 (± 20.5)
65.9 (± 20.2)
36.8 (± 22.7)
Physical health (summary score)
52.9 (± 14.7)
Mental health (summary score)
66.7 (± 19.4)
Pearson correlations coefficient between WORC, constant score, RAND-36 and Shoulder hindrance (N = 57)
Correlation coefficients (r)
Physical health (summary score)
Mental health (summary score)
There were no ceiling effects for the different domains of the WORC. Two patients (3.5%) had a minimal score (worst possible), in the ‘Emotions’ and ‘Work’ domains. There were no floor or ceiling effects for the total WORC. No floor effects on the shoulder hindrance scale were seen, however, 5 patients (8.8%) had the maximum score (extreme hindrance). No floor or ceiling effects were present for the Constant Score or for the summary scores ‘Physical health’ and ‘Mental health’ of the RAND-36. Since the questionnaires were filled out in the present of an independent physical therapist, there was no missing data.
Agreement and reliability
Cronbach’s Alpha, Intraclass Correlation Coefficients (ICC), Standard error of Measurement (SEM) and Smallest Detectable Change (SDC) of the Dutch version of the WORC (0-100)
ICC (95% CI)
WORC score total
WORC-sports and recreation
This article presents the Dutch version of the WORC. The translation of an HRQL-questionnaire is not a simple operation as it is subject to one overriding requirement–equivalence between source and target version(s), and subject to two constraints–of time and cost . This paper shows the step-by-step creation of a conceptually equivalent of the WORC by following the MAPI methodology. As stated previously, this translation is not a literal translation. The explanation of the questions section at the end of the questionnaire and the ‘Instructions to patients’ at the beginning of the questionnaire are very valuable supplements. In the Instruction section, patients are advised to make their “best guess” if an item does not pertain to them. The “best guess” leaves some space for free interpretation, however as long as this interpretation is the same each time a patient fills out the questionnaire there is no devaluation of the test. This ‘Instructions to patients’ and the ‘section with explanations to the questions’ are essential to the questionnaire and should not be omitted.
Table 1 shows the differences between the Dutch WORC and the original questionnaire. We believe these differences were due to linguistic or cultural differences, except for question 16 (How much difficulty have you experienced with styling your hair because of your shoulder?). Strictly speaking bald people have no difficulty styling their hair. On the other hand in the instruction section patients were asked to make their “best guess” if an item did not pertain to them. In close consultation with the developer of the test we adjusted the explanation of the question. Question 9 (How much difficulty do you have with someone or something coming in contact with your affected shoulder?), 12 (How much difficulty do you experience working above your head?) and 17 (How much difficulty do you have “roughhousing and horsing around” with family or friends?) have been slightly adjusted, because of linguistic differences. Testing the WORC revealed cultural differences e.g. question 10 (How much difficulty do you experience doing push-ups or other strenuous shoulder exercises because of your shoulder?). In the Netherlands far less elderly perform push-ups or other strenuous shoulder exercises on regular basis. Emphasizing to the patient that they read the instruction section carefully resolved this problem.
Even though the Constant Score has become the most widely used shoulder evaluation instrument in Europe, we are not aware of any validated translation. Validated translations have probably never been performed because it is not purely a patient reported outcome measure since 65% is based on physical examination. A correlation of 0.60 between the objective Constant Score and the subjective Dutch WORC was found. This is in accordance with correlations found in other articles [10, 22]. There was a strong reversed correlation demonstrated between experienced shoulder hindrance and the WORC (r = -0.75). There were no floor or ceiling effects present. This indicates that patients with the lowest or highest possible score could be distinguished from each other. Furthermore, the responsiveness of questionnaires with substantial floor or ceiling effects would be limited, because changes over time cannot be measured in these patients .
Agreement and reliability
The Crohnbach’s Alpha and intraclass correlation coefficients for this Dutch version were high (ICC 0.91; α 0.95) showing excellent internal consistency and strong test-retest reliability. Results are comparable to the original questionnaire (ICC 0.96)  and translations in other countries like Persia (ICC 0.90; α 0.92) , Turkey (ICC 0.98; α 0.92) , Germany (α 0.96) , Norway (ICC 0.84; α 0.91)  and Brazil (ICC 0.97; α 0.88) . SEM and SDC in this study are acceptable. The larger the SEM the lower the precision of the instrument. Small changes cannot be distinguished from measurement error when the measurement error is large .
The authors of the original WORC suggested that the WORC would be an appropriate measurement tool for primary outcome in clinical trials evaluating treatments in this patient population. Additionally it could be used in clinical practice for following individual patients . Holtby et al. stated that the WORC could provide valuable information to examiners in detecting which patients might not respond favorably to treatment or might require a different management . In the current study the WORC is validated in a heterogeneous population with DRC (rotator cuff tear, calcific tendonitis, tendonitis and impingement). We expect that further validation of the WORC in more specific patient groups and responsiveness of the WORC will give more information about the usage of it in individual patients.
This study presents the cross-cultural Dutch equivalent of the WORC and elaborates its realization process. The Dutch version of the WORC seems to be a reliable measurement tool for assessing health-related quality of life in patients with rotator cuff disorders within the Dutch population.
SG is one of the authors and the copyright holder of the original WORC questionnaire.
We thank Duo Vertaalburo and Yvonne Verdonschot for creating the forward translations.
- Boileau P, Brassart N, Watkinson DJ, Carles M, Hatzidakis AM, Krishnan SG: Arthroscopic repair of full-thickness tears of the supraspinatus: does the tendon really heal?. J Bone Joint Surg. 2005, 87 (6): 1229-1240. 10.2106/JBJS.D.02035.View ArticlePubMedGoogle Scholar
- Burkhart SS, Tehrany AM: Arthroscopic subscapularis tendon repair: technique and preliminary results. Arthroscopy. 2002, 18 (5): 454-463. 10.1053/jars.2002.30648.View ArticlePubMedGoogle Scholar
- Murray TF, Lajtai G, Mileski RM, Snyder SJ: Arthroscopic repair of medium to large full-thickness rotator cuff tears: outcome at 2- to 6-year follow-up. J Shoulder Elbow Surg. 2002, 11 (1): 19-24. 10.1067/mse.2002.120142.View ArticlePubMedGoogle Scholar
- Tauro JC: Arthroscopic rotator cuff repair: analysis of technique and results at 2-and 3-year follow-up. Arthroscopy. 1998, 14 (1): 45-51. 10.1016/S0749-8063(98)70119-7.View ArticlePubMedGoogle Scholar
- Wolf EM, Pennington WT, Agrawal V: Arthroscopic rotator cuff repair: 4-to 10-year results. Arthroscopy. 2004, 20 (1): 5-12. 10.1016/j.arthro.2003.11.001.View ArticlePubMedGoogle Scholar
- Wolf EM, Pennington WT, Agrawal V: Arthroscopic side-to-side rotator cuff repair. Arthroscopy. 2005, 21 (7): 881-887. 10.1016/j.arthro.2005.03.014.View ArticlePubMedGoogle Scholar
- Huijsmans PE, Pritchard MP, Berghs BM, van Rooyen KS, Wallace AL, de Beer JF: Arthroscopic rotator cuff repair with double-row fixation. J Bone Joint Surg. 2007, 89 (6): 1248-1257.View ArticlePubMedGoogle Scholar
- Burkhart SS, Danaceau SM, Pearce CE: Arthroscopic rotator cuff repair: analysis of results by tear size and by repair technique-margin convergence versus direct tendon-to-bone repair. Arthroscopy. 2001, 17 (9): 905-912. 10.1053/jars.2001.26821.View ArticlePubMedGoogle Scholar
- Wilson F, Hinov V, Adams G: Arthroscopic repair of full-thickness tears of the rotator cuff: 2-to 14-year follow-up. Arthroscopy. 2002, 18 (2): 136-144. 10.1053/jars.2002.30443.View ArticlePubMedGoogle Scholar
- Kirkley A, Alvarez C, Griffin S: The development and evaluation of a disease-specific quality-of-life questionnaire for disorders of the rotator cuff: the Western Ontario Rotator Cuff Index. Clin J Sport Med. 2003, 13 (2): 84-92. 10.1097/00042752-200303000-00004.View ArticlePubMedGoogle Scholar
- Dawson J, Fitzpatrick R, Carr A: Questionnaire on the perceptions of patients about shoulder surgery. J Bone Joint Surg Br. 1996, 78 (4): 593-600.PubMedGoogle Scholar
- Hollinshead RM, Mohtadi NG, Vande Guchte RA, Wadey VM: Two 6-year follow-up studies of large and massive rotator cuff tears: comparison of outcome measures. J Shoulder Elbow Surg. 2000, 9 (5): 373-381. 10.1067/mse.2000.108389.View ArticlePubMedGoogle Scholar
- Hudak PL, Amadio PC, Bombardier C: Development of an upper extremity outcome measure: the DASH (disabilities of the arm, shoulder and hand) [corrected]: the upper extremity collaborative group (UECG). Am J Ind Med. 1996, 29 (6): 602-608. 10.1002/(SICI)1097-0274(199606)29:6<602::AID-AJIM4>3.0.CO;2-L.View ArticlePubMedGoogle Scholar
- Kirkley A, Griffin S, Dainty K: Scoring systems for the functional assessment of the shoulder. Arthroscopy. 2003, 19 (10): 1109-1120. 10.1016/j.arthro.2003.10.030.View ArticlePubMedGoogle Scholar
- L’Insalata JC, Warren RF, Cohen SB, Altchek DW, Peterson MG: A self-administered questionnaire for assessment of symptoms and function of the shoulder. J Bone Joint Surg. 1997, 79 (5): 738-748. 10.1302/0301-620X.79B5.7345.View ArticlePubMedGoogle Scholar
- Lippitt SB, Harryman DT, Matsen FA: A practical tool for evaluating function: the simple shoulder test. 1992, Rosemont, IL: American Academy of Orthopaedic SurgeonsGoogle Scholar
- Richards RR, An K-N, Bigliani LU, Friedman RJ, Gartsman GM, Gristina AG, Iannotti JP, van Mow C, Sidles JA, Zuckerman JD: A standardized method for the assessment of shoulder function. J Shoulder Elbow Surg. 1994, 3 (6): 347-352. 10.1016/S1058-2746(09)80019-0.View ArticlePubMedGoogle Scholar
- Roach KE, Budiman-Mak E, Songsiridej N, Lertratanakul Y: Development of a shoulder pain and disability index. Arthritis Care Res. 1991, 4 (4): 143-149. 10.1002/art.1790040403.View ArticlePubMedGoogle Scholar
- Rowe CR, Patel D, Southmayd WW: The Bankart procedure: a long-term end-result study. J Bone Joint Surg. 1978, 60 (1): 1-16.PubMedGoogle Scholar
- Acquadro C, Jambon B, Ellis D, Marquis P: Language and translation issues. 1996, Philadelphia: Lippincott-Raven, 2Google Scholar
- Ekeberg OM, Bautz-Holter E, Tveita EK, Keller A, Juel NG, Brox JI: Agreement, reliability and validity in 3 shoulder questionnaires in patients with rotator cuff disease. BMC Musculoskelet Disord. 2008, 9: 68-10.1186/1471-2474-9-68.View ArticlePubMedPubMed CentralGoogle Scholar
- El O, Bircan C, Gulbahar S, Demiral Y, Sahin E, Baydar M, Kizil R, Griffin S, Akalin E: The reliability and validity of the Turkish version of the Western Ontario Rotator Cuff Index. Rheumatol Int. 2006, 26 (12): 1101-1108. 10.1007/s00296-006-0151-2.View ArticlePubMedGoogle Scholar
- Huber W, Hofstaetter JG, Hanslik-Schnabel B, Posch M, Wurnig C: Translation and psychometric testing of the Western Ontario Rotator Cuff Index (WORC) for use in Germany. Z Orthop Grenzgeb. 2005, 143 (4): 453-460. 10.1055/s-2005-836677.View ArticleGoogle Scholar
- Lopes AD, Ciconelli RM, Carrera EF, Griffin S, Faloppa F, Dos Reis FB: Validity and reliability of the Western Ontario Rotator Cuff Index (WORC) for use in Brazil. Clin J Sport Med. 2008, 18 (3): 266-272. 10.1097/JSM.0b013e31817282f4.View ArticlePubMedGoogle Scholar
- Mousavi SJ, Hadian MR, Abedi M, Montazeri A: Translation and validation study of the Persian version of the Western Ontario Rotator Cuff Index. Clin Rheumatol. 2009, 28 (3): 293-299. 10.1007/s10067-008-1042-6.View ArticlePubMedGoogle Scholar
- VanderZee KI, Sanderman R, Heyink JW, de Haes H: Psychometric qualities of the RAND 36-item health survey 1.0: a multidimensional measure of general health status. Int J Behav Med. 1996, 3 (2): 104-122. 10.1207/s15327558ijbm0302_2.View ArticlePubMedGoogle Scholar
- Hays RD, Sherbourne CD, Mazel RM: The RAND 36-item health survey 1.0. Health Econ. 1993, 2 (3): 217-227. 10.1002/hec.4730020305.View ArticlePubMedGoogle Scholar
- Hays RD, Morales LS: The RAND-36 measure of health-related quality of life. Ann Med. 2001, 33 (5): 350-357. 10.3109/07853890109002089.View ArticlePubMedGoogle Scholar
- Constant CR, Murley AH: A clinical method of functional assessment of the shoulder. Clin Orthop Relat Res. 1987, 214: 160-164.PubMedGoogle Scholar
- Constant CR, Gerber C, Emery RJ, Sojbjerg JO, Gohlke F, Boileau P: A review of the constant score: modifications and guidelines for its use. J Shoulder Elbow Surg. 2008, 17 (2): 355-361. 10.1016/j.jse.2007.06.022.View ArticlePubMedGoogle Scholar
- Krishnan SG, Hawkins RJ, Bokor DJ: Clinical Evaluation of Shoulder Problems. 2004, Philadelphia: Saunders, Volume 3rd: 1Google Scholar
- Andrews JR: Diagnosis and treatment of chronic painful shoulder: review of nonsurgical interventions. Arthroscopy. 2005, 21 (3): 333-347. 10.1016/j.arthro.2004.11.003.View ArticlePubMedGoogle Scholar
- Wessel RN, Lim TE, van Mameren H, de Bie RA: Validation of the Western Ontario Rotator Cuff index in patients with arthroscopic rotator cuff repair: a study protocol. BMC Musculoskelet Disord. 2011, 12: 64-10.1186/1471-2474-12-64.View ArticlePubMedPubMed CentralGoogle Scholar
- Terwee CB, Bot SD, de Boer MR, van der Windt DA, Knol DL, Dekker J, Bouter LM, de Vet HC: Quality criteria were proposed for measurement properties of health status questionnaires. J Clin Epidemiol. 2007, 60 (1): 34-42. 10.1016/j.jclinepi.2006.03.012.View ArticlePubMedGoogle Scholar
- McHorney CA, Tarlov AR: Individual-patient monitoring in clinical practice: are available health status surveys adequate?. Qual Life Res. 1995, 4 (4): 293-307. 10.1007/BF01593882.View ArticlePubMedGoogle Scholar
- Bland JM, Altman DG: Cronbach’s alpha. BMJ Clin Res. 1997, 314 (7080): 572-10.1136/bmj.314.7080.572.View ArticleGoogle Scholar
- Shrout PE, Fleiss JL: Intraclass correlations: uses in assessing rater reliability. Psychol Bull. 1979, 86 (2): 420-428.View ArticlePubMedGoogle Scholar
- Nunnally JC, Bernstein IH: Psychometric theory. 1994, New York: McGraw-Hill, 3Google Scholar
- de Vet HC, Terwee CB, Knol DL, Bouter LM: When to use agreement versus reliability measures. J Clin Epidemiol. 2006, 59 (10): 1033-1039. 10.1016/j.jclinepi.2005.10.015.View ArticlePubMedGoogle Scholar
- Holtby R, Razmjou H: Measurement properties of the Western Ontario rotator cuff outcome measure: a preliminary report. J Shoulder Elbow Surg. 2005, 14 (5): 506-510. 10.1016/j.jse.2005.02.017.View ArticlePubMedGoogle Scholar
- The pre-publication history for this paper can be accessed here:http://www.biomedcentral.com/1471-2474/14/362/prepub
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