The Six-Minute Walking Test (6MWT) as a Measure of Functional Impairment in Lumbar Degenerate Disc Disease.

The study determines the reliability and validity of the 6-Minute Walking Test (6MWT) in patients with lumbar degenerative disc disease (DDD).

The purposes of the study is to assess the ability of the 6-Minute Walking Test (6MWT) as a reliable and standardized objective outcome assessment and its relation to already established subjective patient reported outcome measures in patients suffering from lumbar degenerative disc disease. We want to use an existing smartphone-application that uses global positioning system (GPS) coordinates to measure walking distance. Applying self- measurement of the 6MWT before and after a therapeutic intervention, we determine objective functional impairment (OFI) in patients. The results of this study add to the understanding of achievable objective outcomes after therapeutic interventions applied to patients with DDD and examines patients acceptance for smartphone based self-measurement. Primary Objectives The primary objective is to determine the reliability and validity of the 6-Minute Walking Test (6MWT) in patients with lumbar degenerative disc disease (DDD) Secondary objectives are 1. to correlate objective functional impairment (OFI) with already established patient-rated outcome measures (PROMs) in the sense of cross-validation. 2. To correlate OFI, as determined by the 6MWT with OFI that is determined by another objective test, the TUG test 3. to then analyze the change in OFI in patients before and after surgical intervention 4. to determine whether patients prefer the objective (6MWT) or subjective (PROMs) repeated assessment of their functional condition.