The measures reflects the percent of patients receiving spine surgery who report an improvement in leg or arm pain that is equal to, or greater than, the standard "Minimum Clinically Important Difference" for the specific measures used in MSSIC to assess back or neck pain. The MCID values are standard values (e.g., 1.75 points or more on a 0-10 rating scale) obtained from published articles, and are specific to spine surgery. The ideal value for the measure is 100% (all patients got better), but actual values are lower than that and vary significantly from hospital to hospital and surgeon to surgeon. Rates are reported on a risk-adjusted basis, with the risk adjustment model based on a set of demographic and clinical characteristics, as well as case-mix variables (e.g., fusion vs. non-fusion) so that rates are truly comparable from surgeon to surgeon. Although it is a rare situation, patients with baseline scores so low as to not allow for an improvement larger than the MCID are excluded from the rate calculation. (Patients with myelopathy as an indication for surgery, for example, may not have pain.)