Degree of the Polyethylene Component Wear – a Predictive Factor for the Outcome of Total Hip Arthroplasty

In patients suffering of osteoarthritis of the hip (a degenerative condition of the hip that finally leads to anatomical and functional impairment of the joint), the only efficient treatment in advanced stages of the disease is the surgical replacement of the joint with a total hip prosthesis. Unfortunately, despite improving the composition of the materials from which these prostheses are made of, as well as their design, they remain functional only for a limited period of time, on one hand due to material wear, and on the other hand due to the loss of attachment to the surrounding bone. Depending on the manner in which the prosthetic components are fixed to the bone, the prostheses can be cemented, when an acrylic cement is used, or uncemented, when the fixation is performed by “forceingly” introducing the prosthetic parts into the anatomic bony articular structures, previously adjusted to the appropriate size. However, the movement coupling of hip prostheses can be made of various materials: polyethylene, metal or ceramics. At present, at a global level, the majority of hip prostheses implanted contain polyethylene, which has been proven to release submicronic particles during its functioning, responsible for altering the quality of the periprosthetic bone (particle desease). This results in loss of appropriate fixation of the prosthetic components, reinstatement of hip pain and functional impairment and the need for a new surgery, to replace the prosthesis with a revision one. A lot of recent material composition and tribology research is aimed to decrease this phenomenon, trying to prolonge the survival rate of these articular prostheses. The purpose of this paper is a radiological evaluation of the prosthetic polyethylene component wear in time (years), a quantification of this wear depending on the different types of prostheses and a correlation between the degree of wear and the radiological signs of deterioration of the periprosthetic bone structures, resulting in mobilization of the prosthetic components (loosening).