OP
Eric Sedletzky
Contributor
I asked my doctor about that very same subject of why the new hip ball is so small, and his answer was that they can't really ream out the socket big enough to place a metal carrier and delrin sleeve big enough to accomodate a ball the same size as an original OEM part.I was so surprised at how small the hip ball that they took out of me is -- just maybe about 1" diameter! I thought it would be about twice or thrice that.
- Bill
There isn't enough bone material on the socket side to be able to do this, otherwise they would be making the structure too thin and weak. When they ream out the socket with the half round bit they only clean it up big enough to set the carrier. He made it sound lime they remove only enough, about 1/8" or less. Then the carrier is probably 1/8" thick so that takes up room, then the teflon or delrin bushing is about 3/16" or 1/4" thick. So by the time you add up all the thickness of the parts for the socket that only leaves room for a 3/4" ball. In my case it might be about 7/8" because I'm pretty good size so they used fairly large parts.
I was hoping for big rig sized front end parts but
Unfortunately that's not the case.
So with this smaller ball, that's why we have restrictions, because it's not a huge ball like an original and it's not quite as stable. Plus at the extreme end of a stretch the new parts will bottom out on the edges and then it will tend to want to pry out the ball from the socket.
This is also why with an original stock hip joint it's so bad to power up a joint to full capacity at the very far reach of a stretch (like pushing like hell on a full stretch with weights) because the surface area is at it's least at that angle and there is the least amount of surface area distributing the weight across the joint.
Those wall climbers that contort their legs way out of normal range to get a foot hold then flex and power up to get another step up need to realize this. They put their joints in the most vulnerable position when they do this.
This is the birth of bone spurs along the edges of hip joints. The body is kind of stupid, it uses calcium to try and repair everything, but calcium is a lousy joint material for a fix.
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