Reliability and Validity of The Korean Translation of The Achilles Tendon Total Rupture Score

The Achilles tendon Total Rupture Score (ATRS) is a widely used patient-reported outcome measure to assess clinical outcomes of Achilles tendon rupture, but it has not been validated in Korean yet. The purpose of this study was to translate the ATRS into Korean and evaluate its reliability and validity in a Korean population. The ATRS was translated into Korean according to recommended guidelines for forward-backward translation. Thirty-eight patients who underwent surgical treatment for Achilles tendon rupture from 2017 to 2019 were enrolled. Reliability was evaluated by the intraclass correlation coecient (ICC), standard error of the measurement (SEM), minimal detectable change (MDC), and Cronbach’s alpha. Construct validity was assessed with Spearman rank correlations with the Foot and Ankle Outcome Score (FAOS) and Numeric Rating Scale (NRS) for pain in daily activity.


Introduction
Achilles tendon rupture is one of the most common tendon injuries in the human body. Due to greater participation in sports activities, this injury has been on the rise. Indeed, the overall incidence of Achilles tendon rupture was 21.5/100,000 per year in 2011 compared to 2.1/100,000 per year in 1979 [1][2][3]. In line with this trend, various treatments have been introduced, requiring accurate evaluation of the clinical outcomes of these treatments.
Patient-reported outcome measures (PROMs) are questionnaires completed by the patients themselves, and they should play a signi cant role in the evaluation of treatment results and decision making for rehabilitation in Achilles tendon rupture. Among available PROMs, the Achilles tendon Total Rupture Score (ATRS) [4] was speci cally developed to evaluate outcomes in patients treated for acute Achilles tendon ruptures, and it is one of the commonly used PROMs for this condition. The ATRS was originally developed in Swedish but has been validated in English, Danish, Dutch, Persian, Polish, Turkish, Greek, Norwegian, Chinese, Italian, Brazilian Portuguese, and French [5][6][7][8][9][10][11][12][13][14][15][16].
To date, no Korean PROMs have been validated speci cally for Achilles tendon rupture. For the Korean population, ankle-speci c PROMs such as the Foot and Ankle Outcome Score (FAOS) have been validated [17], but an Achilles tendon-speci c PROM is important for a more precise evaluation of treatment outcomes, especially since the incidence of this injury is growing. Therefore, the purpose of this study was to translate the ATRS into Korean and to validate its measurement properties. This will facilitate future research on the treatment of Achilles tendon ruptures in the Korean population.

Translation procedure
The validated English ATRS was translated into Korean according to the guidelines of cross-cultural adaptation, which standardize the translation procedures into six steps to achieve linguistic and cultural equivalence between the original and translated versions of the questionnaire [18]. Forward translations from English to Korean were performed by two independent bilingual translators, and discrepancies were resolved by judgement of a third bilingual translator. The backward translation into English was performed by another two independent bilingual translators. A diverse group of 15 volunteers checked to ensure clear comprehension of each question. If there were discrepancies, they were resolved by consensus discussion among translators.

Study population
This study included patients who underwent surgical treatment for acute Achilles tendon rupture from June 2017 to May 2019. Exclusion criteria were concomitant lower limb injury, age less than 18 years, and unable to read, write, and understand Korean. After approval by the by the local Ethics Committee, patients who were eligible were informed of the objectives of the study and consent was obtained from those willing to participate. Because there is no consensus regarding sample size calculations for the validation of PROMs, we aimed to recruit as many participants as possible during the study period. Among 67 patients with Achilles tendon rupture during the study period, two were excluded, 24 were not willing to participate in the study, and three did not complete the questionnaires. Therefore, questionnaires from 38 patients were used for the statistical analysis.

Questionnaires
All questionnaires contained the Korean-translated version of the ATRS, a validated Korean FAOS, and Numeric Rating Scale (NRS) for pain. The ATRS questionnaire contains 10 questions, and each question is answered on an 11-point Likert scale ranging from 0 to 10. The total score ranges from 0 to 100 and is calculated by summing the individual Likert items. Higher scores indicate good physical activity and lower symptoms [4].
The FAOS is a self-administered questionnaire originally designed to evaluate patients with ankle ligament injuries, but it has also been used for Achilles tendon rupture [4,19]. The FAOS includes 42 questions with ve subscales: pain, other symptoms, activities of daily living (ADL), function in sports and recreation, and foot-and ankle-related quality of life (QOL). Each question is answered on a 5-point Likert scale ranging from 0 to 4. A normalized score is calculated for each subscale, with 100 indicating no symptoms and 0 indicating severe symptoms [19].
The NRS is a commonly used assessment of pain severity. To express the intensity of pain, patients quantify their pain on an 11-point Likert scale ranging from 0 to 10, with 0 indicating no pain and 10 indicating the worst pain imaginable [20]. In this study, the NRS in daily activity was assessed.

Reliability
Each patient completed the questionnaires twice, with a 2-week interval, between 6 and 12 months after surgery. Because patient health status should be unchanged over the 2-week interval, patients did not receive any rehabilitation or treatment that could signi cantly affect their condition during the test-retest period. One of the authors evaluated the health status of patients at baseline and after 2 weeks, and patients who reported a change in their health status were excluded.
Internal consistency refers to the degree of homogeneity of the responses to the items of the questionnaire and was evaluated with the Cronbach alpha coe cient. A Cronbach alpha coe cient greater than 0.7 was considered to be acceptable [24].

Construct validity
Construct validity was evaluated with correlations between the Korean translation of the ATRS and the ve subscales of the FAOS and the NRS in daily activity. Correlations were measured with Spearman rank correlations and assessed with the following criteria: uncorrelated (lower than 0.4 or higher than − 0.4), moderate (between 0.4 and 0.7 or between − 0.4 and − 0.7), and strong (higher than 0.7 or lower than − 0.7) [25]. On the basis of the results of Dutch and Swedish validation studies [4,11], we hypothesized that the Korean translation of the ATRS would be strongly correlated with the FAOS symptom, pain, function, and ADL subscales, and moderately correlated with the FAOS QOL subscale and the NRS in daily activity.
Floor and ceiling effects If more than 15% of responders achieve the lowest or highest possible score, oor or ceiling effects are considered to be present [25]. When either effect is present, patients with a minimum or maximum score cannot be distinguished from one another, which reduces the interpretability of the questionnaire. In the current study, oor and ceiling effects were evaluated with histograms.

Statistical analysis
Data normality was determined with the Kolmogorov-Smirnov test. Continuous variables showing a normal distribution were summarized as mean and SD. Clinimetric properties were calculated as described above. Statistical analyses were performed with the Statistical Package for the Social Sciences (SPSS®) software, version 23.0 (IBM, Armonk, New York, USA), and signi cance was set at p < 0.05.

Ethics
This study was approved by the Ethics Committee of Korea University Medical Center (IRB No. 2019GR0477). Informed consent was obtained from all participants. All methods were carried out in accordance with Declaration of Helsinki.

Translation process
Both forward and backward translation were performed without signi cant di culties. Despite a few semantic differences during translations, there were no major discrepancies in translation to discuss, and few adjustments were necessary. Volunteers checked the Korean version of the questionnaire and found it to be clearly comprehensible. Therefore, we approved the nal version of the Korean translation of the ATRS (Appendix 1).

Demographics
Patient characteristics were similar between non-participants and participants, with no signi cant difference observed between groups (Table 1).

Floor and ceiling effects
None of the patients achieved the lowest score, and two patients (5.3%) achieved the highest score. Therefore, there were no oor or ceiling effects in the Korean translation of the ATRS.

Discussion
The primary nding of this study was that the Korean translation of the ATRS showed su cient reliability and validity. Therefore, the Korean translation of the ATRS can be used in the Korean population to evaluate the clinical outcomes of treatment for Achilles tendon rupture.
In this study, the ICC value for test-retest reliability of the Korean translation of the ATRS was 0.838, which is lower than that of previous translations of the original ATRS into other languages, including English (ICC = 0.986) [13], Persian (ICC = 0.98) [10], Turkish ( ICC = 0.98) [7], Chinese (ICC = 0.979) [6], Greek (ICC = 0.97) [15], French (ICC = 0.966) [16], Italian (ICC = 0.96) [5], Brazilian Portuguese (ICC = 0.93) [9], Danish (ICC = 0.908) [12], Norwegian (ICC = 0.90) [5], Polish (ICC = 0.90) [14], and Dutch (ICC = 0.852) [11]. We suspect that the relatively low ICC value in this study was due to the timing of completion of the questionnaires, which occurred between 6 and 12 months after surgery. Patients in this study did not reported changes in health status over the 2-week test-retest interval, but may have experienced a marked improvement in activities compared to patients in other studies conducted later after surgery. This difference could have affected the test-retest reliability of this study. Indeed, Carmont et al. [13] evaluated test-retest reliability of the ATRS at 3, 6, and 12 months after treatment and found that reliability increased as time passed after treatment. Although the ICC value of the current study is not as high as other studies, it can still be categorized as excellent. Thus, we conclude that the Korean translation of the ATRS is reliable.  [10], Norwegian (6.13) [5], Danish (6.67) [12], and Dutch (10.91) [11]. In addition, the %SEM value, which is an expression of the SEM as a percentage of the mean score, was 8.8% in the current study. Values of %SEM that are lower than 10% are regarded as acceptable for clinical purposes [26]. The MDC at the group and individual levels indicated that the Korean translation of the ATRS was suitable for identifying real changes when comparing groups of patients with a difference above 2.98 points and individual patients with a difference above 13.38 points.
Until now, no validated questionnaire speci c to the evaluation of clinical outcomes of treatment for Achilles tendon rupture, such as the VISA-V [27] or Leppilahti score [28], has been validated in Korean. Therefore, we used the FAOS to evaluate the validity of the Korean translation of the ATRS because the FAOS has been validated in Korean and has been used to assess the outcomes of Achilles tendon rupture, as well as the validity of other translations of the ATRS [4,5,11,17,29]. The overall correlation between the Korean translation of the ATRS and the FAOS was above 0.7. Although the correlation coe cient was below 0.7 for the FAOS subscale QOL, four out of ve a priori hypothesized correlations were con rmed by this study. Therefore, we considered the validity of the Korean translation of the ATRS to be acceptable.
This study had two main limitations. First, the number of participants was relatively small compared to previous studies of the validity and reliability of outcome measures for ATRS. Although there is no agreed optimum method to determine the appropriate sample size for evaluating the validity of PROMs, the 38 participants in this study may be considered insu cient when compared with previous studies that enrolled a mean of 78 participants (range, 46 to 112 participants) [5][6][7][8][9][10][11][12][13][14][15][16]. Second, the responsiveness or sensitivity to change of the Korean translation of the ATRS was not assessed because no participants reported any changes in their status over the test-retest interval. Evaluating changes in patient status is critical for the assessment of therapeutic interventions, so it will be necessary con rm this in future studies of the Korean translation of the ATRS.

Conclusion
The Korean translation of the ATRS showed su cient reliability and validity for use in the Korean population to evaluate clinical outcomes of treatment for Achilles tendon rupture. Authors' contributions YHP: study design, patient enrollment, data collection, and original draft preparation; HWC: patient enrollment and data collection; JWC: statistical analysis and manuscript correction; HJK: study design, and manuscript correction.

Funding
Not applicable.

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

Ethics approval and consent to participate
This study was approved by the Ethics Committee of Korea University Medical Center (IRB No. 2019GR0477). Informed consent was obtained from all participants. All methods were carried out in accordance with Declaration of Helsinki.

Consent for publication
Written informed consent for publication was obtained from all participants.