The author(s) declare that they have no competing interests.
ØS conceived of the study, carried out the radiographic examination and is the main author of the paper. ØK carried out the histopathologic examination. Both authors read and approved the final manuscript.
We are grateful to Ms. Birgit Røe and Ms. Anne-Kristine Fevang for performing the histopathologic sections, to Dr. Agnar Kvellestad for practical help with photographic editing and to Dr. Monica Theresa Johnsen for language consultation.