Footnotes

• Handling editor Josef S Smolen

• Collaborators The Surgery for rotator cuff disease Finland (SURFIN) Investigators: Markus Sormaala; Tero Irmola; Heidi Lehtokangas; Juho Liukkonen; Konsta Pamilo; Tero Ridanpää; Kai Sirniö; Juhana Leppilahti.

• Contributors Concept and design: JP, IK, HK, JY. Acquisition analysis or data interpretation: SC, TF, JY, HK, AT, IK, JP. SC and JP had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.Drafting the manuscript: SC, TF, JY, HK, AT, IK, JP. Critical revision of the manuscript for important intellectual content: SC, TF, JY, HK, AT, IK, JP. Statistical analysis: HK, SC, JP. Funding procurement: JP, IK, JL. Supervision: JP, IK, HK.

• Funding This work was supported by grants from the Academy of Finland (grant 12321/13 September 2007) 265646/17 April 2013) and National Competitive Research Funding of the University of Eastern Finland. None of the writers has any conflicts of interest relevant to this article.

• Competing interests None declared.

• Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

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