Abstract
The design of an artificial hip joint is influenced by the problems of surgical technique in making the implant. Encouraging results have already attended the use of an elementary design of ball and socket joint with the rubbing surfaces exposed to tissue fluids. When the surfaces are of identical metals (chrome–cobalt alloy) the tissue fluids appear to lubricate in some measure; when the ball is of metal and the socket of high molecular weight polyethylene there appears to be some degree of self-lubrication in the plastic.
The essential problem is whether particles abraded from the rubbing surfaces will cause harmful tissue reactions over a long period of time. The more resistant the materials are to wear, the less will be the amount of the abraded material to cause harm. The success of the exposed joint is such that it seems desirable to explore to the limit this simple solution before seeking new and more complex designs. The exposed bearing has an additional advantage in permitting subluxation as a safeguard if the hip is violently forced beyond its designed range; this protects from avulsion the cement bond between the living bone and the implant.
General factors in design are discussed which have developed from practical experience with different types of total prosthesis used in clinical practice. The attempt has been made to concentrate on information obtained from surgical experience rather than to report laboratory tests which are readily repeatable in engineering laboratories.
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