Cervical Radiculopathy Impact Scale: Translation, cross-cultural adaptation, reliability and validity of the Turkish version

Alp Eren Çelenlioğlu1, Savaş Şencan2, Rekib Saçaklıdır2, Ekim Can Öztürk2, Osman Hakan Gündüz2

1Department of Pain Medicine, University of Health Sciences, Gülhane Training and Research Hospital, Ankara, Türkiye
2Department of Physical Medicine and Rehabilitation, Division of Pain Medicine, Marmara University Faculty of Medicine, Istanbul, Türkiye

Keywords: Cervical radiculopathy, disability evaluation, herniated disc, pain measurement, questionnaire.

Abstract

Objectives: The aim of this study was to translate and cross-culturally adapt the English version of the Cervical Radiculopathy Impact Scale (CRIS) and to investigate the validity and reliability of the Turkish version of the CRIS.

Patients and methods: Between October 2021 and February 2022, a total of 105 patients (48 males, 57 females; mean age: 45.4±11.8 years; range, 36.5 to 55.5 years) who were diagnosed with cervical radiculopathy due to disc herniation were included. Disability and quality of life were evaluated with the Neck Disability Index (NDI), Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH), and Short Form-12 (SF-12). Pain severity was evaluated using the Numerical Rating Scale (NRS) in three subscales (neck pain, pain radiating to the arm, and numbness in the finger, hand, or arm). The internal consistency for CRIS was assessed using the Cronbach alpha and test-retest reliability by intraclass correlation coefficients (ICCs). Explanatory factor analyses were performed for construct validity. To examine the content validity, the correlations among the three subgroup scores of CRIS and the other scale scores were analyzed.

Results: The internal consistency of CRIS was found to be high (α=0.937). A high reliability was obtained for test-retest reliability for the three subscales of CRIS (Symptoms, Energy and postures, Actions and activities) (ICC: 0.950, 0.941, 0.962, respectively; p<0.001). All three subscale scores of CRIS were correlated with the NDI, QuickDASH, SF-12 (physical and mental) and NRS scores (r=0.358-0.713, p<0.001). Factor analysis showed that the scale had five factors.

Conclusion: The CRIS is a valid and reliable instrument for Turkish patients with cervical radiculopathy due to disc herniation.

Introduction

Cervical radiculopathy (CR) describes radiating pain in one or both upper extremities caused by compression or inflammation of a spinal nerve root by a cervical herniated disc or by degenerative osteophytes.[1] Neck pain is often present with pain radiating to the extremities. It can be accompanied by motor and/or sensory deficits.[2,3] The incidence is reported to be up to 100 per 100,000 individuals, with a peak at fourth and fifth decades of life.[4] The most frequently affected nerve roots are C6 and C7.[4,5] Diagnosis is usually made by medical history and physical examination combined with imaging modalities.[6] The management of CR includes conservative, interventional, and surgical treatments, although the results of comparative studies still remain controversy.[7,8]

There is a growing interest in cervical disc herniation (CDH) treatment in the literature, and a number of studies have been published, particularly during the recent years.[9-11] Nevertheless, most studies are limited due to the fact that a patientreported comprehensive outcome scoring system approved for CR is not available. Functional and comprehensive outcome measures for CR are essential to depict the effectiveness of different treatment techniques and to choose the most convenient one. The Cervical Radiculopathy Impact Scale (CRIS) was recently developed by Gartner et al.[3] which comprises 21 questions divided over three subscales. It is intended to cover the measurement of symptoms and limitations of the arm and neck due to CR and has shown good validity and reliability. However, to date, the Turkish version of the CRIS has not been validated, which impedes a thorough assessment of Turkish patients with CR. In the present study, we, therefore, aimed to translate and crossculturally adapt the English version of the CRIS and validate the reliability of the Turkish version of the CRIS in patients with CR due to disc herniation.

Patients and Methods

This prospective study was conducted at Marmara University Pendik Training and Research Hospital and Gülhane Training and Research Hospital Pain Medicine outpatient clinics between October 2021 and February 2022. A permission was obtained from Anne M. Stiggelbout for the translation of the CRIS into Turkish, adapt it cross-culturally, and investigate the validity and reliability of the Turkish version of CRIS.

A total of 168 patients were screened. Cervical spinal stenosis was detected in 34 patients and these patients were excluded from the analysis. In addition, 12 patients with diabetes, 12 patients with peripheral nerve entrapment, and five patients had cervical spinal surgery were also excluded. The study was carried out with 105 patients (48 males, 57 females; mean age: 45.4±11.8 years; range, 36.5 to 55.5 years) with CDH. The number of participants was calculated as five for each question according to previously published guidelines.[12] Inclusion criteria were as follows: age between 18 and 65 years, having CR due to CDH as confirmed by magnetic resonance imaging, a symptom duration of ≥3 months, at least one of the three criteria (i.e., severity of neck pain, radiating to the arm, numbness in the finger, hand or arm) based on the Numerical Rating Scale (NRS) ≥4, and patient literacy, on physical examination, presence of sensory deficit and/or motor deficit, or reflex changes in the affected nerve-root distribution. Exclusion criteria were having cervical spinal stenosis, having a neuromuscular and rheumatic diseases, having diabetes mellitus, undergoing cervical spinal surgery, and the presence of upper extremity entrapment neuropathy. The study flowchart is shown in Figure 1.

Figure 1. Study flowchart. NRS: Numerical Rating Scale; DASH: Disabilities of the Arm, Shoulder and Hand; NDI: Neck disability Index; CRIS: Cervical Radiculopathy Impact Scale.

Demographic data of the patients, age, sex, body mass index (BMI), comorbid diseases, medications used, previous treatments, symptoms duration, and occupational status were collected. All participants were evaluated with the NRS, Quick Disabilities of the Arm, Shoulder and Hand (QuickDASH), Short Form-12 (SF-12), Neck Disability Index (NDI), and CRIS. In addition, the CRIS was re-filled for retest 15 days later.

NRS: The NRS pain scale is used to measure the severity of pain. Scores ranged from 0 no pain/numbness) to 10 (worst possible pain/numbness). The patient scores his/her pain between 0 and 10. It is frequently used in clinical studies, as it is an easy-to-understand scale. Three different NRS scores were used in the study: neck pain (NRS-neck), pain radiating to the arm (NRS-arm), and numbness in the finger, hand or arm (NRS-numbness).

QuickDASH: This is an 11-item questionnaire with a five-point response scale for each question that measures patients’ perceptions of disability and symptoms associated with any condition that affects the upper extremity. A total score is calculated for participants who complete at least 10 out of 11 items. The total score ranges from 0 (no injury) to 100 (most serious injury).[13] It has been shown to be valid and reliable in the Turkish population.[14]

SF-12: This is a test consisting of seven questions in total, in which the quality of life of the patient is questioned. Two types of scores are calculated in the questionnaire: physical (PCS-12) and mental score (MCS-12). High scores are associated with patient well-being and improved quality of life.[15] It has been shown to be valid and reliable in the Turkish population.[16]

NDI: This is a questionnaire that measures disability in patients with neck pain, based on the extent to which disability and pain can participate in the patient's performance and activities of daily living, and it has been validated in Turkish population.[17] The 10-item questionnaire has a six-point response scale ranging from 0 (no disability) to five (total disability), with higher scores indicating a higher degree of disability.

CRIS: This scale focuses on arm and neck symptoms and functionality related to cervical radicular syndrome. It is a questionnaire that includes the measurement of symptoms and limitations due to neck disability, radiating pain in the arm, numbness and loss of sensation in patients with CR. It is a 21-item questionnaire that consists of three subscales (Symptoms, Energy and postures, and Actions and activities), and it is scored between 0 and 100.[3]

Translation and cultural adaptation

In the present study, the translation and intercultural adaptation processes were used following previously published guidelines.[18,19]

Stage 1 (Translation): The questionnaire was translated into Turkish by two translators, who were able to speak Turkish and English fluently, according to the conceptual translation of phrases. One of the translators has no medical/clinical background.

Stage 2 (Synthesis): After the translation, a joint text was prepared with the participation of all translators.

Stage 3 (Back translation): The Turkish version was translated back into English by two native English-speaking translators.

Stage 4 (Clinician’s committee): A review group consisting of four pain medicine specialists, two physiatrists, and a health professional was convened. They were asked to comment on points that could be related to cultural differences and cause difficulties in daily life. Finally, a synthesis of the Turkish pre-final version of the index was conducted.

Stage 5 (Face validity, pretest): The pre-final version of the questionnaire was used on 10 patients. The patients were asked to indicate the points they did not understand about the questionnaire questions.

Stage 6 (Committee evaluation and test): Pretest results were evaluated by the committee. The final version of the questionnaire was prepared based on the opinions of the committee members.

Reliability

The reliability of the scale was evaluated under two headings: internal consistency and test-retest reliability. Internal consistency was evaluated with the Cronbach alpha (α) coefficient, and test-retest reliability was evaluated with the intraclass correlation coefficient (ICC) and 95% confidence interval (CI).

Validity

The validity of the scale was examined under the titles of construct validity and content validity. Explanatory factor analysis was performed for construct validity. To examine the content validity, the correlations among the three subgroup scores of CRIS and the NRS, QuickDASH, SF-12, and NDI scores were analyzed with the Spearman correlation coefficient. The correlation coefficient between 0.91-1.00 was considered perfect, 0.71-0.90 good, 0.51-0.70 moderate, 0.31-0.50 acceptable, and < 0.30 weak.[20]

Statistical analysis

Statistical analysis was performed using the IBM SPSS version 23.0 (IBM Corp., Armonk, NY, USA) and Jamovi version 2.0 software (The Jamovi Project, 2021). Descriptive data were presented in mean ± standard deviation (SD), median (min-max) or number and frequency, where applicable. The conformity of numerical variables to the normal distribution was examined using the Shapiro-Wilk test, and it was seen that they fit the normal distribution. Relationships between the CRIS subgroup scores and categorical data were analyzed using the one-way analysis of variance (ANOVA), and the relationship between numerical features was analyzed using the Spearman correlation analysis. A p value of < 0.05 was considered statistically significant.

Results

The median CR symptom duration was 12 (range, 3 to 240) months. Cervical disc herniation was detected most frequently at the level of C6-7 (n=40, 38.1%). This was followed by C5-6 (n=32, 30.5%), more than one disc level (n=13, 12.4%) and C7-T1 (n=12, 11.4%) disc herniation, respectively. The numerical demographic and clinical characteristics of the patients are shown in Table 1, and the categorical demographic and clinical characteristics of the patients are shown in Table 2. The mean and median scores of the NDI, QuickDASH, SF-12 subscales, NRS, and CRIS subscales are shown in Table 3.

Table 1. Descriptive data of numerical variables

Table 2. Descriptive data of categorical variables

Table 3. Scale scores used in the study

Reliability

The internal consistency of CRIS was high (α=0.937). Twenty-six patients were re-tested. Test-retest reliability was evaluated for the three subscales of CRIS (Symptoms, Energy and postures, and Actions and activities), and high reliability was obtained (ICC: 0.950, 0.941, 0.962, p< 0.001) (Table 4).

Table 4. Test-retest reliability results (n=26)

Content validity

Three subscale scores of the CRIS were correlated with NDI, Quick-DASH, SF-12 (physical and mental), NRS-neck, NRS-arm, and NRS-numbness (r=0.358-713, p< 0.001) (Table 5).

Table 5. Content validity results

Construct validity

Explanatory factor analysis was performed to evaluate internal construct validity. After the factor loads were rotated with the Varimax rotation method, five subscales with eigenvalues greater than 1 and explaining 72% of the total variance were obtained. The correlations of each question with the underlying factors are presented in Table 6.

Table 6. Rotated component loadings according to explanatory factor analysis

Discussion

In the present study, we investigated the validity and reliability of the CRIS in patients with radiculopathy due to CDH upon translation of the original English version of the scale into Turkish. The translation procedure was carried out in line with the cross-cultural adaptation guidelines and no difficulties were reported.[18,19] The results indicated that the CRIS was a valid and reliable instrument that could be used in the future to evaluate the arm and neck symptoms and functionality associated with CR in Turkish populations.

A number of studies have been published in the relevant literature during recent years due to a growing interest in the treatment of CDH.[9-11,21] The main goal of CR treatment is to reduce radicular pain along with reducing present functional loss. Therefore, studies investigating treatment efficacy should be carried out using comparable, reliable, and verified assessment tools.[22] Nevertheless, most studies are limited due to the fact that a patientreported comprehensive outcome scoring system approved for CR is not available.[3] Despite the widespread use in the relevant studies, the NRS and Visual Analog Scale (VAS) are inadequate, as they only assess the severity of pain and do not provide information about disability or functional status. The NDI, which has a Turkish version with proven validity and reliability, only assesses the disability due to neck problems.[17] Similarly, QuickDASH, which also has a Turkish version with proven validity and reliability, only evaluates the disability and symptoms of the upper extremity, and therefore, cannot provide a comprehensive assessment of the CR symptoms.[23] Therefore, CRIS was developed by Gartner et al.[3] with an aim to improve the quality of the studies, ensuring a comprehensive assessment of CR symptoms and functional losses caused by CR as a whole. To the best of our knowledge, there is no validity and reliability study in the relevant literature conducted for adapting the CRIS to other languages.

The CRIS development study found the Cronbach α values for the three subscales of the CRIS (symptoms, energy and posture, action, and activities) as 0.927, 0.909, and 0.902, respectively, indicating a high internal consistency.[3] Similarly, in the present study, the overall Cronbach α value for the CRIS was 0.937 and, thus, the internal consistency was very high. In the CRIS development study, the ICC scores for the three subscales were above 0.8, indicating a good test-retest reliability.[3] In the present study, the ICC scores for three subscales were 0.950, 0.941, and 0.962 respectively, suggesting a very high reliability. Our results had internal consistency in this respect.

Furthermore, we found that the CRIS subscale scores were acceptable and positively and significantly correlated with the NDI scores. In addition, the symptoms and energy and posture subscales of the CRIS was positively and significantly correlated with QuickDASH, where the action and activities subscale was moderately positively and significantly correlated. In the CRIS development study, all three subscales of CRIS were well, positively, and significantly correlated with the NDI and QuickDASH scores.[3] This difference between the correlation of the NDI and CRIS subscale may be due to the difference in patient selection in the respective studies. Only the patients with CR associated with CDH were included in the present study to form a homogeneous patient population. Patients with cervical spinal stenosis and patients who underwent cervical spinal surgery were excluded from the study.

In many studies, the SF-12 was used to measure health-related quality of life (HRQoL) in patients with CR.[24-26] Unlike the CRIS development study, SF-12 was used instead of SF-36 in the present study to assess the HRQoL, as it was shorter and took less time to complete.[3,27] The PCS-12 was moderately, negatively, and significantly correlated with the symptoms subscale of CRIS and acceptably, negatively, and significantly correlated with the action and activities subscale of CRIS. The mental health component scale (MCS-12), on the other hand, was acceptably, negatively, and significantly correlated with the three subscales of the CRIS. Bhadra et al.[24] reported postoperative improvements in both PCS-12 and MCS-12 in patients with a single-level CR. This result is suggestive of the impaired physical and mental function in patients with CR. The fact that the CRIS is correlated with both physical and mental functionality is important for a comprehensive evaluation of patients with CR who are assessed based on the CRIS.

In the present study, the NRS was preferred over the VAS due to the ease of application in the assessment of the severity of pain.[28] In the CRIS development study, there was a moderately-well, positive, and significant correlation between the three subscales of the CRIS and the VAS scores (neck pain, pain radiating to the arm, and numbness in the finger, hand, or arm), while there was an acceptable-moderate, positive, and significant correlation with NRS scores in the present study. In the current study, the lowest correlation was between the action and activities subscale of the CRIS and NRS neck pain, similar to correlation results for NDI scores. The difference in the number of patients included or the difference in patient inclusion criteria in the respective studies may account for this difference. In addition, although both the VAS and NRS scales are valid, reliable, and suitable for use in clinical practice for the assessment of pain severity, the difference between the two studies, albeit minor, may be due to the difference in the way the VAS and NRS were applied.[29]

While there were three subscales defined in the original scale, five subscales were found during explanatory factor analysis in the present study unlike the original scale.[3] As a result of these results, some items were included in the different subscales, where the number of subscales was higher than the original scale. The differences as regards the inclusion criteria in the respective studies may account for the above. In the CRIS development study, patients with a duration of CR symptoms for two months or more were included in the study, where patients with CR during the subacute period were also included in the study. In the present study, patients with CR in the chronic period of three months or more were included. Furthermore, only the patients with CR associated with CDH were included in our study and patients with a history of cervical spinal surgery were excluded. On the contrary, 21% of the patients had a history of surgical operation in the CRIS development study.[3] Pursuant to the inclusion criteria of the present study, patients with a score of at least ≥4 from three different NRS scores (neck pain, pain radiating to the arm, and numbness in the finger, hand, or arm) were included in the study, where the CRIS development study required the sum of three different VAS scores to be a minimum of 1. This difference as regards the patient groups might have been associated with a change in CR-related symptoms and functional impairment, thereby resulting in a higher number of subscales as a result of the factor analysis in our study. Therefore, we suggest that the suitability of this weak scale can be increased by further studies, which would separately investigate the acute, subacute, and chronic periods in patients with CR due to a specific diagnostic etiology and standardize the cut off values based on the severity levels for pain and/or numbness.

Nonetheless, this study has certain limitations. First, only the patients with chronic CR were included in this study. The patients with CR in acute and subacute periods were excluded from the study. Second, the reaction of the CRIS scores to post-treatment change were unable to be assessed. Nevertheless, the main strength of the study lies in the fact that it was carried out in two centers and with a homogeneous patient group with a specific diagnosis.

In conclusion, the Turkish version of the CRIS is a valid and reliable instrument that can be used in the future to assess the arm and neck symptoms and functionality in CR associated with disc herniation in the Turkish population. Unlike the other scales that contain general items for the assessment of CR, the CRIS is specific to and objective for CR.

Citation: Çelenlioğlu AE, Şencan S, Saçaklıdır R, Öztürk EC, Gündüz OH. Cervical Radiculopathy Impact Scale: Translation, cross-cultural adaptation, reliability and validity of the Turkish version. Arch Rheumatol 2022;37(4):574-583.

Ethics Committee Approval

The study protocol was approved by the Marmara University Faculty of Medicine Ethics Committee (date: 08.10.2021, no: 1107). The study was conducted in accordance with the principles of the Declaration of Helsinki.

Author Contributions

Contributed to the study conception and design: A.E.Ç., S..; Material preparation, data collection, and analysis were performed: A.E.Ç., R.S., E.C.Ö.; The manuscript was written: A.E.Ç., S.., R.S., E.C.Ö.; The supervisor: O.H.G.; All authors read and approved the final manuscript.

Conflict of Interest

The authors declared no conflicts of interest with respect to the authorship and/or publication of this article.

Financial Disclosure

The authors received no financial support for the research and/or authorship of this article.

References

  1. Sanal-Toprak C, Ozturk EC, Yucel FN, Sencan S, Gunduz OH. Does the presence of neuropathic pain affect the outcomes of the interlaminar epidural steroid injection for cervical disc herniation?: A prospective clinical study. Medicine (Baltimore) 2021;100:e25012. DOI: 10.1097/MD.0000000000025012
  2. Childress MA, Becker BA. Nonoperative management of cervical radiculopathy. Am Fam Physician 2016;93:746-54.
  3. Gärtner FR, Marinus J, van den Hout WB, Vleggeert-Lankamp C, Stiggelbout AM. The Cervical Radiculopathy Impact Scale: Development and evaluation of a new functional outcome measure for cervical radicular syndrome. Disabil Rehabil 2020;42:1894-905. DOI: 10.1080/09638288.2018.1534996
  4. Kim DG, Chung SH, Jung HB. The effects of neural mobilization on cervical radiculopathy patients’ pain, disability, ROM, and deep flexor endurance. J Back Musculoskelet Rehabil 2017;30:951-9. DOI: 10.3233/BMR-140191
  5. Borrella-Andrés S, Marqués-García I, Lucha-López MO, Fanlo-Mazas P, Hernández-Secorún M, PérezBellmunt A, et al. Manual therapy as a management of cervical radiculopathy: A systematic review. Biomed Res Int 2021;2021:9936981. DOI: 10.1155/2021/9936981
  6. Woods BI, Hilibrand AS. Cervical radiculopathy: Epidemiology, etiology, diagnosis, and treatment. J Spinal Disord Tech 2015;28:E251-9. DOI: 10.1097/BSD.0000000000000284
  7. Taso M, Sommernes JH, Kolstad F, Sundseth J, Bjorland S, Pripp AH, et al. A randomised controlled trial comparing the effectiveness of surgical and nonsurgical treatment for cervical radiculopathy. BMC Musculoskelet Disord 2020;21:171. DOI: 10.1186/s12891-020-3188-6
  8. House LM, Barrette K, Mattie R, McCormick ZL. Cervical epidural steroid injection: Techniques and evidence. Phys Med Rehabil Clin N Am 2018;29:1-17. DOI: 10.1016/j.pmr.2017.08.001
  9. Sun FQ, Wen SJ, Ye BL, Li CX, Fan YF, Luo YS, et al. Posterior percutaneous endoscopic versus traditional surgery for cervical disc herniation: A protocol for systematic review and meta analysis. Medicine (Baltimore) 2020;99:e21442. DOI: 10.1097/MD.0000000000021442
  10. Mesregah MK, Feng W, Huang WH, Chen WC, Yoshida B, Mecum A, et al. Clinical effectiveness of interlaminar epidural injections of local anesthetic with or without steroids for managing chronic neck pain: A systematic review and meta-analysis. Pain Physician 2020;23:335-48.
  11. Byvaltsev VA, Stepanov IA, Riew DK. Mid-term to long-term outcomes after total cervical disk arthroplasty compared with anterior diskectomy and fusion: A systematic review and meta-analysis of randomized controlled trials. Clin Spine Surg 2020;33:192-200. DOI: 10.1097/BSD.0000000000000929
  12. Anthoine E, Moret L, Regnault A, Sébille V, Hardouin JB. Sample size used to validate a scale: A review of publications on newly-developed patient reported outcomes measures. Health Qual Life Outcomes 2014;12:176. DOI: 10.1186/s12955-014-0176-2
  13. Gummesson C, Ward MM, Atroshi I. The shortened disabilities of the arm, shoulder and hand questionnaire (QuickDASH): Validity and reliability based on responses within the full-length DASH. BMC Musculoskelet Disord 2006;7:44. DOI: 10.1186/1471-2474-7-44
  14. Mehta S, Macdermid JC, Carlesso LC, McPhee C. Concurrent validation of the DASH and the QuickDASH in comparison to neck-specific scales in patients with neck pain. Spine (Phila Pa 1976) 2010;35:2150-6. DOI: 10.1097/BRS.0b013e3181c85151
  15. Gandek B, Ware JE, Aaronson NK, Apolone G, Bjorner JB, Brazier JE, et al. Cross-validation of item selection and scoring for the SF-12 Health Survey in nine countries: Results from the IQOLA Project. International Quality of Life Assessment. J Clin Epidemiol 1998;51:1171-8. DOI: 10.1016/S0895-4356(98)00109-7
  16. Soysal Gündüz Ö, Mutlu S, Aslan Basli A, Gül C, Akgül Ö, Yilmaz E, et al. Validation of the Turkish Form of Short Form-12 health survey version 2 (SF-12v2). Arch Rheumatol 2021;36:280-6. DOI: 10.46497/ArchRheumatol.2021.8458
  17. Telci EA, Karaduman A, Yakut Y, Aras B, Simsek IE, Yagli N. The cultural adaptation, reliability, and validity of neck disability index in patients with neck pain: A Turkish version study. Spine (Phila Pa 1976) 2009;34:1732-5. DOI: 10.1097/BRS.0b013e3181ac9055
  18. Beaton DE, Bombardier C, Guillemin F, Ferraz MB. Guidelines for the process of cross-cultural adaptation of self-report measures. Spine (Phila Pa 1976) 2000;25:3186-91. DOI: 10.1097/00007632-200012150-00014
  19. Guillemin F. Cross-cultural adaptation and validation of health status measures. Scand J Rheumatol 1995;24:61-3. DOI: 10.3109/03009749509099285
  20. Koo TK, Li MY. A guideline of selecting and reporting intraclass correlation coefficients for reliability research. J Chiropr Med 2016;15:155-63. DOI: 10.1016/j.jcm.2016.02.012
  21. Wang QL, Tu ZM, Hu P, Kontos F, Li YW, Li L, et al. Long-term results comparing cervical disc arthroplasty to anterior cervical discectomy and fusion: A systematic review and meta-analysis of randomized controlled trials. Orthop Surg 2020;12:16-30. DOI: 10.1111/os.12585
  22. Gebremariam L, Koes BW, Peul WC, Huisstede BM. Evaluation of treatment effectiveness for the herniated cervical disc: A systematic review. Spine (Phila Pa 1976) 2012;37:E109-18. DOI: 10.1097/BRS.0b013e318221b5af
  23. Koldas Dogan S, Ay S, Evcik D, Baser O. Adaptation of Turkish version of the questionnaire Quick Disability of the Arm, Shoulder, and Hand (Quick DASH) in patients with carpal tunnel syndrome. Clin Rheumatol 2011;30:185-91. DOI: 10.1007/s10067-010-1470-y
  24. Bhadra AK, Raman AS, Casey AT, Crawford RJ. Single-level cervical radiculopathy: Clinical outcome and cost-effectiveness of four techniques of anterior cervical discectomy and fusion and disc arthroplasty. Eur Spine J 2009;18:232-7. DOI: 10.1007/s00586-008-0866-8
  25. Joswig H, Neff A, Ruppert C, Hildebrandt G, Stienen MN. Repeat epidural steroid injections for radicular pain due to lumbar or cervical disc herniation: What happens after ‘salvage treatment’? Bone Joint J 2018;100-B:1364-71. DOI: 10.1302/0301-620X.100B10.BJJ-2018-0461.R1
  26. Massel DH, Mayo BC, Bohl DD, Narain AS, Hijji FY, Fineberg SJ, et al. Improvements in neck and arm pain following an anterior cervical discectomy and fusion. Spine (Phila Pa 1976) 2017;42:E825-E832. DOI: 10.1097/BRS.0000000000001979
  27. Ware J Jr, Kosinski M, Keller SD. A 12-Item ShortForm Health Survey: Construction of scales and preliminary tests of reliability and validity. Med Care 1996;34:220-33. DOI: 10.1097/00005650-199603000-00003
  28. Karcioglu O, Topacoglu H, Dikme O, Dikme O. A systematic review of the pain scales in adults: Which to use? Am J Emerg Med 2018;36:707-14. DOI: 10.1016/j.ajem.2018.01.008
  29. Williamson A, Hoggart B. Pain: A review of three commonly used pain rating scales. J Clin Nurs 2005;14:798-804. DOI: 10.1111/j.1365-2702.2005.01121.x