Resonably fixed charnley stem and loose cup
Why did it fail?
Poor acetabular cementing
Medial wall penentration could cause other problems but not loosening.
Tips for good acetabular cementing
Dont ream the subchondral bone off
The last reamer used should be at least 2 mm or 4 mm more than the cup size to get at least a 2 mm cement mantle with good penetrarion
Don't ream the subchondral bone. Multiple(8 to 10 in no) 4 mm peg holes better than large key holes. Make the key holes wider than the mouth for macro locking.
Dry acetabular bed before cementing
Pressurise after inserting doughy cement
Apply cement on the back of the cup too to avoid blood at the cement implant interface
Insert the cup locking the inferior cement first in an open position before bringing it to 40 degrees and anterverting. Maintain pressure with the head shaped pusher while removing excess cement from the periphery till its hard
Remove any peripheral osteopyhtes to prevent impingement
Finally it is easier to do an uncemented cup well than a cemented cup for the beginner
Do we revise the cup alone?
If we do this, the dislocation chances are higher due to neck cup impingement. To correct this one needs to revise the stem to use a 32 mm or 36 mm head.
How do we revise the stem?
a. ETO and distal fixing uncemented stem
b. Cement on cement revision as advised by Dr. Phil Roberts
We did a cement on cement stem and an uncemented cup without removing the medial cement, obtained could posterior superior contact
Used a high speed drill and stem extraction and cementeda tapered stem with an oxinium on xlpe liner
