were seeking medical and dental treatment for the first time in their lives.
This demand for healthcare led to a crusade to find better materials for
dentures and tooth implants, and it was an organic chemist in Manchester,
Dennis Smith, who recommended polymethylmethacrylate to John
Charnley.
Polymethylmethacrylate (PMMA), also known as acrylic cement, is a
self-curing cement that is formed by the simple combination of a liquid
monomer and a powdered polymer. The watery liquid monomer is stored
in a vial (with an inhibitor chemical), while the powder (with the
appearance of powdered sugar) is saved in a pouch. At the time of surgery,
the surgical assistant combines the two ingredients in a mixing bowl, akin
to making bread dough. The mixture is initially creamy, then becomes
doughy, and in a few minutes is like fresh Play-Doh. Polymerization is the
frantic race of smaller chemical molecules, the “monomers,” linking with
larger chain-like polymers to form a complex latticework of rigid matter.
The chemical process is “exothermic,” meaning that heat is given off as
the molecular linkage occurs, starting as a viscous slurry, then progressing
to a pliable plastic, and as it hardens, an elastic blob, before becoming a
solid piece of polymer. Today, we see PMMA every day, in Plexiglas
windows, display cases, eyeglasses, signs, bathtubs, and skylights. But
Charnley saw PMMA as the ideal grout for holding hip stems in place.
Without experimenting on animals, he first started using it in humans in
1958, and was immediately convinced of its potential. A half century later,
Charnley’s cement is used daily in every hospital in the world, with only
slight chemical modifications.
Charnley left Manchester for good after 1958, initially working part-
time in Wrightington, but eventually spending all his time at the previous
TB hospital in the countryside. The local hospital board provided the funds
for a biomechanical workshop and laboratory, and Charnley soon hired a
laboratory technician, Harry Craven, a jack-of-all-trades who was at
Charnley’s side for many years during the pivotal moments of the 1960s.
The lab opened in 1961, and with a dedicated staff and purpose-built
operating rooms, Charnley was optimistic enough in his ongoing success
to give his epicenter a name, the Centre for Hip Surgery—Wrightington
Hospital.
Like all innovators of science and medicine, John Charnley was a
tinkerer. He made things, fixed machines, fabricated models, and
marcin
(Marcin)
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