German translation and initial measurement properties of the Q-TFA in transfemoral bone-anchored prosthesis users

Abstract Background To translate and cross-culturally adapt the Questionnaire for Persons with a Transfemoral Amputation (Q-TFA) into German and evaluate initial measurement properties in adults with unilateral transfemoral amputation using a transcutaneous bone-anchored prosthesis. Methods Sixty-one participants completed the German Q-TFA and comparator patient-reported outcome measures at baseline and after 12–15 days. The original four-score Q-TFA structure was retained: Prosthetic Use, Prosthetic Mobility, Problem, and Global scores. Test-retest reliability, measurement error, internal consistency of the Problem Score, floor and ceiling effects, and hypothesis-based construct validity were assessed. Results The 61 participants (42 male, 19 female; mean age 56.2 ± 11.7 years) used bone-anchored transfemoral prostheses; trauma was the etiology in 74%. Baseline mean ± SD scores were 82.1 ± 29.2 for Prosthetic Use, 52.0 ± 10.0 for Prosthetic Mobility, 21.3 ± 16.6 for Problems, and 65.4 ± 18.6 for Global. ICCs ranged from 0.960 to 1.000. The Problem Score had high internal consistency (Cronbach’s α = 0.955), no score showed a substantial floor or ceiling effect, and all six nonredundant construct-validity hypotheses were confirmed. Conclusions The German Q-TFA, scored according to its original four-score structure, showed high short-interval test-retest reliability and supportive construct-validity findings in this selected bone-anchored prosthesis cohort. Structural validity, patient-based content validity, responsiveness, and interpretability remain to be established before the instrument is used to infer clinically important change or for formal cross-center benchmarking.