Footnotes

• Contributors Both authors contributed in a substantial way to the conception or design of the work, the acquisition, analysis and interpretation of data; drafting the work or revising it critically for important intellectual content; final approval of the version published; and agreement to be accountable for all aspects of the work.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests The first author serves on the advisory boards of Axial Healthcare and Alosa and has stock options in Axial Healthcare. He serves on the board of directors for the Association of Pain Program Directors. These arrangements have been reviewed and approved by Johns Hopkins University in accordance with its conflict of interest policies.

• Patient consent for publication Not required.

• Provenance and peer review Not commissioned; externally peer reviewed.