Evaluation of treatments effectiveness in a context of value-based health care is based on outcomes, and in their assessment. The patient perspective is gaining renovated interest, as demonstrated by the increasing diffusion of Patient Reported Outcome Measure (PROMs) collection initiatives. The concept of Minimal Clinically Important Dif-ference (MID) is generally seen as the basis to estimate the actual effect perceived by the patient after a treatment, like a surgical intervention, but a universally recognized threshold has not yet been established. At the Orthopedic Institute Galeazzi (Milan, Italy) we began a digitized program of PROM collection in spine surgery by means of a digital platform, called Datareg. In this work we aim to investigate MID in the treatment of degenerated disc in terms of patients' perceptions as these are collected through the above electronic registry. We proposed a computation of MID on the basis of two PROM scores, and a critical comparison with a domain expert's proposal.