7/365 What is bone cement? It's a polymer, a chain of 'mer' units - MMA, methylmethacrylate - and is therefore known as PMMA or, more commonly, under one of the trade names below. 
The inert effect of PMMA in the human body was first noticed by Harold Ridley, an ophthalmic surgeon, who looked after pilots after WW2, removing shrapnel from their eyes. He noticed that pilots who flew behind glass canopies developed an aggressive foreign body reaction
However, Spitfire pilots who flew behind their streamlined canopies made from Lucite/ Perspex, produced no foreign body reaction around the fragments of PMMA. This prompted him to make the first intraocular lenses out of PMMA.
It's an organic substance, made from C,H and O and polymerises when the powder polymer is mixed with the vial of liquid monomer.
Like all material it has a stress strain curve and a modulus of elasticity
One of the many lovely things about PMMA is that it has a very low modulus of elasticity, similar to bone and similar to polyethylene. And an order of magnitude less than metal such as steel and titanium. This means it's 'kind' to bone.
It's a modulator of stress. Between loads applied to sockets, through the polyethylene, to the metal implant , then down the femoral component, back into the cement and once again out into the bone, delivered to the individual trabeculae into which it has been pressurised.
And thanks to Julius Wolff and his law, the bone responds, strengthening, preserving and reacting.
And this is why, 44.5 years after insertion, the femoral bone in this hip on the right looks as good as the day it had its #ExeterHip put in. #ExeterHip50
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