head-to-shell ratio

Please, could anyone explain me what the "head-to-shell" ratio means when talking about hip replacements. It is not very clear to me, what the "shell" is - is it the artificial acetabular surface that is in contact with the artificial femur head? ...and could the "head-to-shell" ratio mean the ratio of surfaces of the femur head and artificial acetabulum, which are in contact?
Sorry, there is no context, just "maximized head-to-shell ratio".
Thank you for any suggestions.
  • Cagey

    post mod (English Only / Latin)
    English - US
    Context would include information like:
    What field is this?
    What kind of document are you looking at?
    Even so, this may be specialized terminology that only people in the field will recognize, but we should have more information than this. Please. :)
    Thank you - the document deals with total hip replacement implants and types of bearings they use.
    Another sentence containing the "shell" in my "head to shell ratio", which may be the most informative I could find:
    The Coating on the back of all Pinnacle acetabular shells is a porous surface composed of commercially pure titanium sintered metal beads.