Experts disagree about the optimal classification of upper extremity disorders. To explore whether differential response to treatments offers a basis for choosing between case definitions, we analyzed previously published research.
We screened 183 randomized controlled trials (RCTs) of treatments for upper extremity disorders identified from the bibliographies of 10 Cochrane reviews and 4 other systematic reviews, and a search in Medline, Embase, and Google Scholar to June 2010. From these, we selected RCTs that allowed estimates of benefit (expressed as relative risks [RRs]) for >1 case definition to be compared when other variables (treatment, comparison group, followup time, outcome measure) were effectively held constant. Comparisons of RRs for paired case definitions were summarized by their ratios, with the RR for the simpler and broader definition as the denominator.
Two RCT reports allowed within-trial comparison of RRs and 13 others allowed between-trial comparisons. Together these provided 17 ratios of RRs (5 for shoulder treatments, 12 for elbow treatments, and none for wrist/hand treatments). The median ratio of RRs was 1.0 (range 0.3-1.7, interquartile range 0.6-1.3).
Although the evidence base is limited, our findings suggest that for musculoskeletal disorders of the shoulder and elbow, clinicians in primary care will often do best to apply simpler and broader case definitions. Researchers should routinely publish secondary analyses for subgroups of patients by different diagnostic features at trial entry to expand the evidence base on optimal case definitions for patient management.