**Conflict of interest**

Martin Matthews is employed as Chairman and United Kingdom state registered clinical specialist orthotist by DM Orthotics Ltd., UK in clinical roles, within the National Health Service hospitals. He is also an Honorary Associate Professor at the University of Plymouth.

James H. Wynne, CPO is employed as Vice President – Director of Education by Boston O&P, Boston, Massachusetts, USA. JIm Wynne and I worked as co authors and therefore although I fully acknowledge Jims involvement we worked closely together as dual authors.
