A798. COUNTERACTING MATERIAL RELIABILITY PROBLEMS IN HIP PROSTHESES BY MEANS OF ADVANCED METHODS OF RAMAN SPECTROSCOPY

Abstract

Total hip arthroplasty (THA) represents a very spread and effective surgical procedure. Surgeons and technologists make daily efforts in improving the outcomes of THA, with the ultimate goal of creating a prosthesis that reliably lasts at least as long as a human lifetime. While the results of primary hip arthroplasty are generally very good, revision surgeries might score variable success with regards to their clinical outcomes. In addition, they invariably represent an expensive procedure and a severe burden to the patients. Thus, a reduction of the failure rates of only a few percents can, due to the large number of patients involved, have a vast influence on the accumulated costs and patient suffering. In other words, the key issue in hip arthroplasty resides in the improvement of the prostheses with regard to their long-term in vivo reliability. These circumstances amply justify a continuous search for new hip prostheses with improved structural characteristics and elongated lifetimes.

Most recent innovative trends in THA have focused on the improvement of the tribological behavior of hip joints and challenged the achievement of a longer durability, with the potential for a service-life spanning several decades. Such trends have naturally led to an increase in the use of ceramic materials, either as ceramic femoral heads yet coupled with advanced acetabular cups made of polyethylene (i.e., with improved molecular structure and quality), or as ceramic hip components for both acetabular and femoral bearing surfaces. The greater driving force in using ceramic bearings is their potential of systematically reducing periprosthetic osteolysis (i.e., mainly arising from polyethylene wear debris), which could potentially reduce the number of surgical revisions. The high inertness and biocompatibility of ceramic materials may also reduce to a minimum the collateral effects on the human body, as possibly observed with metallic prostheses (e.g., contamination by metal ions, hypersensitivity, etc.). Despite those advantages, chipping and fracturing have severely limited the popularity of ceramic components. As a further issue, it should be noted that ceramic-on-ceramic articulations strongly require high precision in setting the orientation of the components during surgery (in order to avoid excessive impingement on the ceramic surface). Partly fractured ceramic bearings necessarily dictate revision. The main reason is that the ceramic remnants in the articulation would give rise to severe third-body wear, especially in the presence of a softer bearing counterpart. Clearly, ceramic components offer a very high potential for further improving both structural performance and lifetime of hip joints but, being made of fragile materials, they also require significant progress in surgery technique, further advancements in joint design and materials manufacturing processes, as well as a peer non-destructive control of their structural reliability.

In this presentation, we shall first have a brief survey on the main cases of failure in the recent history of hip prostheses. Then, a description of the most advanced and recent technological approaches to material preparation, reliability control and non-destructive analysis of hip components will also be given. The main aim of this presentation is to drive the attention of the international orthopaedic community on the need for a highly interdisciplinary approach to the study of hip joint arthroplasty. In this context, we provide here some vivid examples of how newly developed Raman spectroscopic methods may provide final solutions to historical problems related to the chemical and structural reliability of materials widely employed in total hip arthroplasty.