Article History
Received: 27 October 2017
Revised: 31 March 2018
Accepted: 22 April 2018
First Online: 10 May 2018
Compliance with ethical standards
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: K. Abelin-Genevois, S. Verdun and D. Sassi have no conflict of interest to disclose. P. Roussouly is shareholder of SMAIO, France. He is also a consultant for Kisco Systems and receives royalties from Medtronic, but these disclosures are not related to the present work.