Classification systems of soft tissue disorders of the neck and upper limb: do they satisfy methodological guidelines?
A critical appraisal of existing classifications of soft tissue disorders of the neck and upper limb was performed utilizing methodological criteria including appropriateness for purpose, validity, reliability, feasibility, and generalizability. Five classifications were assessed independently by three raters using standardized forms. For those criteria that can be assessed by inspection of the classification itself, none of the classification systems appeared acceptable for reasons such as failure to be comprehensive, overlap of categories, and lack of demonstration that the criteria for inclusion into the categories are valid and reliable. No judgement could be passed about those criteria that require formal testing, such as reliability and construct validity, because of the absence of data. The overall interrater reliability of the critical appraisal was high, with an intraclass correlation coefficient of 0.82. The validity of studies that have relied upon existing classifications of soft tissue disorders of the neck and upper limb to group the entities under study is questioned in light of the findings of this study. Future work should be directed toward improving existing classification systems and/or developing new ones that fulfil basic measurement criteria