In this case report, researchers from the Department of Orthopaedics at the University of Southern California and the Los Angeles Orthopaedic Hospital noted that the hip replacement was made of mixed metals and polyethylene, and was composed of different components from different manufacturers. The reason to mix component parts is that surgeons can get a prosthesis to fit the anatomical requirements of different patients.
This journal report cites sources that go as far back as 1973. The researchers conclude that cobalt and chromium alloy have a corrosion potential similar to that of titanium alloy, while alumina ceramic has a very high corrosion resistance. The junction between the hip ball and the stem at the Morse taper appeared to be especially susceptible to crevice corrosion and fretting as a result of the movement of the patient.
As far back as 1978, a published study found mild surface effects from titanium alloy disks implanted in dogs for 30 months resulting in crevice corrosion. Another published review from 1981 found a small opening between the ball and the neck of a cobalt-chromium alloy coupled with a titanium alloy stern. Slight corrosion was obvious, though considered insignificant.
A 1988 published report found deep wear on a retrieved cobalt-chromium femoral stem attributed to defective components made ‘out-of-tolerance’ which resulted in loose fit. A 1988 report found a patient with a metal hip experienced a severe reaction to the surrounding tissues including necrosis, inflammation, fibrosis and osteolysis of the pubic bone. In a patient with a total hip replacement, osteolysis results from metal wear particles leaving debris in the ball and socket joint. The body tries to absorb the debris, whether plastic or metal, which triggers an autoimmune reaction as well as the resorption of bone tissue which can loosen the prosthesis.
As long ago as 1988, scientists were discussing formation of soft-tissue pseudo tumors after uncemented hip arthroplasty. Yet scientists at the U.S. Food and Drug Administration listening to metal hip manufacturers during a June expert panel gathering acted as though they had not heard of these complications. Manufacturers acted as though it was business-as-usual when complications arose.
With almost 40 years worth of scientific papers accumulated on the wear of metal-on-metal and ceramic hip replacement components, why are we still making the same hips that have thousands of patients facing life-altering complications?