Head neck ratio

happyhopper · September 04, 2014, 03:47:36 AM

Hi everyone
Just wondered if anyone can explain (in laymans terms) the implications of the head neck ratio in resurfacing? Also wondered if there were any special considerations for the female head neck ratio?
Look forward to hearing your ideas.

chuckm · September 05, 2014, 08:33:46 AM

Hi Happyhopper, the words "implications" and "considerations" are keeping everyone silent. I think a resurfacing surgeon might answer those best.
But, my non-medical understanding is the head to neck ratio is a measurement that compares the size of the femoral head to the size of the femoral neck. In basic terms, the larger the diameter of the ball is compared to the diameter of the neck, the more range of motion can be achieved. In some people with FAI, the neck has grown "fatter" in certain areas and so the ratio is reduced. Simply put, the neck is too wide and it bangs into the edges of the socket. Other patients have developed over time a femoral head that has "slipped" away from being centered on the femoral neck. And so the neck will "bang" into the side much sooner on one side. In resurfacing, the new femoral cap is measured and placed to be right back in the center of the neck so it restores all the "clearances" for the neck. And sometimes non structural cysts are shaved off the neck too that were making the neck too wide.
But, there are so many other things involved in the head / neck ratio like the depth of the patients hip socket. I understand that women more often than men have hip dysplasia. A shallow hip socket will allow more range of motion theoretically but is less stable. And so that is another confusing issue with head neck ratio discussion. Can a shallow hip be reamed deeper to accommodate the new metal cup?
Sorry that is as far as I will try to go with a complex question.

Chuckm

Dannywayoflife · September 05, 2014, 11:01:32 AM

Great post there by chuck. And yes as far as I'm aware usually a shallow dysplasia socket can be reamed to accept a new cup

chuckm · September 05, 2014, 12:34:54 PM

Right...most of the time. But the good brands of resurfacing devices have a special dysplasia cup that has an external tab with a screw that can be tapped into the pelvis to help hold the cup in place when there is less bone to ream into.

Chuck