[German Translation and Validation of the Patient-Oriented Questionnaire "Thumb Disability Examination" (TDX) for Specific Diagnosis and Follow-Up of Thumb Carpometacarpal Joint Osteoarthritis].

Background: Patient-reported outcome measures (PROMs) are becoming increasingly important in today's patient care. Unfortunately, the most common PROMs in hand surgery are very time-consuming and usually do not cover the actual, diagnosis-specific complaints of the patients. For diagnosis and follow-up of thumb carpometacarpal joint osteoarthritis, Noback et al. developed and validated the Thumb Disability Examination (TDX) questionnaire. This 20-item questionnaire specifically assesses daily living limitations and pain as well as patient-reported satisfaction of thumb function. The aim of this study is to validate the German translation of the TDX, the Thumb Disability Examination - German (TDX-G), and to compare it with the German-language versions of the MHQ and qDASH, which are currently used as gold standard.

Material und methods: Translation and back-translation were performed in accordance with accepted guidelines. For statistical validation of the TDX-G, 30 consecutive patients with thumb carpometacarpal joint osteoarthritis were interviewed under standardised conditions. Internal consistency was calculated using Cronbach's alpha. Test-retest reliability was determined in 10 patients who completed the TDX-G twice at an interval of 2 weeks. The validity of the TDX-G was determined by calculating the correlation coefficients of the TDX-G with the MHQ and qDASH, subjective pain sensation (NRS), and hand strength levels (coarse and pinch strength). In addition, the time to collect each questionnaire was compared.

Results: The TDX-G has high internal consistency (Cronbach's alpha 0.932) and test-retest reliability (intraclass correlation coefficient 0.963 [0.850-0.991]). There is a significant correlation between TDX-G and MHQ (- 0.782; p<0.001) and qDASH (0.833; p<0.001). All questionnaires correlate significantly with pain on exertion and pinch force, with the TDX-G having the highest correlation in each case. Significantly less time is needed to record the TDX-G (110±28 s) than to record the MHQ (413±98 s).

Conclusion: The TDX-G is a reliable tool for diagnosing and monitoring the progression of thumb carpometacarpal joint osteoarthritis. It can be used in both patient care and clinical research and accurately mirrors the symptoms.