General health measures in shoulder surgery: are we powered for success?

Surgeons, policymakers, and payers increasingly use changes in general health to guide decision-making. It is unknown how such measures are incorporated into shoulder surgery research, how strongly they are associated with changes in shoulder-specific outcomes, and whether they are appropriately powered.

PubMed was searched for articles reporting shoulder-specific and general health measures after rotator cuff repair and total shoulder arthroplasty. Study characteristics, results at the study group level, reporting of power calculations, and statistical significance were recorded. Meta-regression was employed to describe the association of changes between shoulder-specific and general health measures.

Of 360 identified abstracts, 21 articles with 28 patient groups were included. Only 1 article was published before 2000. There was a strong association of changes between shoulder-specific and general health measures (r = 0.66; P < .001). Power calculations were mentioned in 33% of studies and based on shoulder-specific measures. Of 20 studies conducting hypothesis tests, 75% reported agreement regarding the statistical significance of shoulder-specific and general health tests. Of 5 discordant studies, 4 found the shoulder-specific measure statistically significant and not the general health measure.

Shoulder surgery research increasingly reports changes in general health measures that are associated with changes in shoulder-specific measures, suggesting that improvements in shoulder symptoms increase quality of life. When disagreement exists, it usually results from the general health measure's not meeting statistical significance, which may simply reflect type II error. Research reporting general health measures should carefully report power considerations to avoid misinterpretation of findings failing to reach statistical significance.