Correction: The protocol for a multisite, double blind, randomized, placebo-controlled trial of axillary nerve stimulation for chronic shoulder pain - Travis Cleland; Nitin B. Jain; John Chae; Kristine M. Hansen; Terri Z. Hisel; Douglas D. Gunzler; Victoria C. Whitehair; Chong H. Kim; Richard D. Wilson (Trials)