(PTFE), also known as Teflon. When we hear the name Teflon, an egg
skillet comes to mind, but its original use was industrial, in the
manufacturing of valve seatings and non-lubricated bearings. Charnley
evaluated Teflon, finding it to be biologically inert, creating almost no
local foreign-body reaction once implanted in a human (he conducted no
animal trials). Teflon is white, semi-translucent, almost waxy in
appearance, and able to be cut with a knife. Starting in 1956, Charnley
started performing the world’s first total hip arthroplasties, using Teflon
cups that were pounded into the patient’s own bony hip socket. The results
were amazing.^6 Patients had wonderful range of motion and excellent pain
relief. Charnley began reporting his results in the British Medical Journal
and the Lancet, two of the most prestigious medical publications in the
world.
One of the most dramatic changes Charnley made in hip replacement
was the courage to change the size of the metal femoral head. All early hip
pioneers, starting with Smith-Petersen and continuing with brothers
Robert and Jean Judet and Austin Moore, had designed their partial joint
replacements with a metal head that was the same size as the patient’s own
femoral head. With the introduction of a synthetic hip cup, Charnley made
a genius decision to decrease the size of the metallic head. Again focusing
on low friction arthroplasty, he determined that a smaller head would
provide less friction, and the head was therefore changed from Moore’s
42mm head (the size of a Ping-Pong ball) to 28mm, and finally to
22.25mm, about the size of an average toy marble. Many surgeons found
John Charnley’s hip design laughable, but he had math on his side.
In the beginning, Charnley was implanting the Austin Moore hip stem
with the large femoral head with no acrylic bone cement. After a few years
of implanting the Moore prosthesis and Teflon cup, he was looking for a
more stable method of implanting the femoral component. In older
patients with weaker bone, the slender metal stem of the Moore prosthesis
could begin to wobble in the canal of the femur, leading to subsidence and
pain. Charnley was used to consulting with the scientists at the University
of Manchester, and having had initial success with Teflon, he turned to
some of the chemists in the department of prosthetics in the University of
Manchester’s Dental School. Dentists were used to dealing with bony
socket defects after the loss of a tooth; in England, following creation of
the National Health Service in 1948, there were millions of patients who