Cobalt Chromium Toxicity Resource Center

Trunnionosis: A pain in the neck, World Journal of Orthopedics, October 2013

In this article, the authors discuss the recent discovery of a condition  known as “trunnionosis.” The consequences of metal on metal hip arthroplasty can be described with an adverse reaction to metal debris, or ARMD. ARMD occurs when the body’s soft tissues are affected by metal ions from Metal on metal (MOM) prosthetics. Some patients who suffer from ARMD may show symptoms, hip1and eventually need a prosthetic replacement, while others may show no symptoms at all. Asymptomatic patients are more difficult to treat because the extent of damage is harder to determine.

Earlier hip replacements were accomplished using a method called “monobloc”. Monobloc is when the prosthesis consists of a non modular femoral head and a single neck. Nowadays, a process called Modularity replaced the monobloc method. In Modularity, there is a femoral neck and femoral body called the trunnion. Modularity works at the junction between the femoral neck and the femoral head at the trunnion. The femoral head then fits into the acetabulum, or socket joint in the pelvis. The femoral neck-head junction has a trunnion with a taper so they can fit together. The taper is where the trunnion attaches to the femoral head.

Recently, however, there is concern about the modularity method and its connection with metal on metal hip replacements. The connection between the femoral head and trunnion with Metal on metal (MOM) hip replacements is indicated as a source of the metal wear debris, a process also known as “truinnionosis”. This connection is currently analyzed using MOM prostheses revision procedures which provide an idea and insight on the extent of damage they are causing. A particular concern is at the junction where the femoral head and trunnion meet. Implant wear debris and material loss are derived mainly at the head-trunnion taper junction as a result of corrosion. Significant evidence suggests wear debris of the hips, and consequently a high failure rate, is associated with the use of MOM prosthetics.

As mentioned above, ARMD phenomenon results from metal ion deposits and debris created from the wear of MOM prostheses. For instance, massive areas of scar tissue, and tissue necrosis (death), resulted from an excess cobalt and chromium levels in the blood stream after implantation of these MOM prostheses.  There is a strong correlation, or connection, between the extent of tissue destruction in patients and the incidence of corrosive wear: there is more tissue destruction in patient’s with a higher percentage of corrosive wear. Some of the damage was so extensive Hip 2physicians were able to palpate (feel) exactly where in the hip the wear had occurred.  The amounts of chromium and cobalt levels in the blood were also significantly higher in MOM prostheses than those with non MOM bearing surfaces. The trunnion-femoral head junction left permanent grooves and pits from extensive corrosion within the prosthetic hip which contained chromium and other metal ions. The hips were also deformed and discolored as a result of the oxidative wear and corrosive damage. This evidence of oxidative wear involved all implants regardless of the manufacturer.

The Full Article can be read at:

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