Getting Back to Basics: The "Primary" Outcome Measure Determines a Study's Conclusion.

In this month's issue, Hollman, Wolterbeek, Zijl, van Egeraat, and Wessel from Nieuwegein, The Netherlands, investigate an essential and most basic concern: how does an abduction brace compare to a simple sling after arthroscopic rotator cuff repair? A criticism of the study, well noted in Editorial Commentary by Kevin Plancher, is that Hollman et al. selected postoperative pain (rather than long-term clinical outcome) as their "primary" outcome measure. The primary outcome measure determines the conclusion of a study. Accurate conclusions require adequate statistical power, particularly if potentially underpowered secondary outcome measures (in this case, long-term clinical outcome) show no difference between 2 treatment options. Research clinicians, patients, and payers comparing abduction brace versus sling after shoulder rotator cuff repair ultimately need to understand if there is a difference in long-term clinical outcomes between the treatment options.