The grades of recommendations (standards, guidelines, and options) and classes of evidence (I–III) are defined at the end of the "Major Recommendations" field.
Standards. There is insufficient evidence to recommend a treatment standard.
Guidelines. There is insufficient evidence to recommend a treatment guideline.
Options. It is recommended that when performing lumbar arthrodesis for degenerative lumbar disease, strategies to achieve successful radiographic fusion should be considered. There appears to be a correlation between successful fusion and improved clinical outcomes; however, it should be noted that the correlation between fusion status and clinical outcome is not strong, and in a given patient, fusion status may be unrelated to clinical outcome.
Summary
At the present time, there is no Class I or II medical evidence to indicate that the appearance of a radiographic fusion is significantly associated with improved functional outcomes. The majority of Class III medical evidence does suggest that successful radiographic fusion is associated with improved clinical outcomes. It is widely acknowledged that this relationship is not perfect.
Definitions:
Grades of Recommendation
Standards Recommendations of the strongest type, based on Class I evidence reflecting a high degree of clinical certainty
Guidelines Recommendations based on Class II evidence reflecting a moderate degree of clinical certainty
Options Recommendations based on Class III evidence reflecting unclear clinical certainty
Classes of Evidence
Class I Evidence from one or more well-designed, randomized controlled clinical trials, including overviews of such trials
Class II Evidence from one or more well-designed comparative clinical studies, such as nonrandomized cohort studies, case-control studies, and other comparable studies, including less well-designed randomized controlled trials
Class III Evidence from case series, comparative studies with historical controls, case reports, and expert opinion as well as significantly flawed randomized controlled trials