We aimed to determine cut-offs between mild, moderate and severe myelopathy on the modified Japanese Orthopedic Association (mJOA) score.

Between December 2005 and January 2011, 757 patients with clinically diagnosed DCM were enrolled in the prospective AOSpine North America (n = 278) or International (n = 479) study at 26 sites. Functional status and quality of life were evaluated at baseline using a variety of outcome measures. Using the Nurick score as an anchor, receiver operating curve (ROC) analysis was conducted to determine cut-offs between mild, moderate and severe disease. The validity of the identified cut-offs was evaluated by examining whether patients in different severity groups differed in terms of impairment, disability, quality of life and number of signs and symptoms.

A mJOA of 14 was determined to be the cut-off between mild and moderate myelopathy and a mJOA of 11 was the cut-off score between moderate and severe disease. Patients in the severe myelopathy group (n = 254) had significantly reduced quality of life and functional status and a greater number of signs and symptoms compared to patients classified as mild (n = 190) or moderate (n = 296).

Mild myelopathy can be defined as mJOA from 15 to 17, moderate as mJOA from 12 to 14 and severe as mJOA from 0 to 11. These categories should be adopted worldwide to standardize clinical assessment of DCM.