Received: 4 February 2018
Accepted: 16 November 2018
First Online: 24 November 2018
: PA is a member of the Editorial Board of BMC Muskuloskeletal Disorders. The other authors have no competing interests.
: All human specimens enrolled in this study were post mortem donors to the Anatomical Institute of the University of Munich and gave their consent to research and scientific investigations. The use of donated post mortem specimens for scientific investigations is in accordance with the Declaration of Helsinki and was approved by the ethical committee of the University of Munich.
: Not applicable.
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