TESS 2.0—Adaptation of the German Version of the Toronto Extremity Salvage Score: Addition of an Item Regarding the Use of a Touchscreen and Keyboard in the Upper Extremity Questionnaire

Background/Objectives: Limb salvage surgery is the preferred treatment for bone and soft tissue tumors. The Toronto Extremity Salvage Score (TESS) is a validated patient-reported outcome measure (PROM). However, its upper extremity section is outdated, lacking assessment of modern technology use. This study adapted TESS (creating TESS 2.0) by adding a question on touchscreen/keyboard use, based on an existing Italian version. Methods: Two independent translations of the new item were synthesized. Linguistic feedback was obtained from two German speakers from Germany and Switzerland. Pretesting with eight individuals refined the wording. Fourteen patients who underwent upper extremity surgery completed the TESS 2.0 twice (once in person, once at home) and the DASH questionnaire once. Reliability was assessed using Cronbach’s alpha and ICC, and validity was assessed using Spearman’s correlation between TESS 2.0 and DASH. Results: TESS 2.0 demonstrated excellent internal consistency (Cronbach’s alpha ≥ 0.98 at both time points). A strong, statistically significant inverse correlation existed between TESS 2.0 and DASH (r = −0.867, p < 0.001). Test–retest reliability was high (ICC = 0.98). Conclusions: German TESS 2.0 is a reliable and valid instrument for assessing upper extremity function in patients treated for bone and soft tissue tumors. Further research is needed to validate its use in postoperative follow-up and a larger, more diverse patient population.