Development of sintered all-UHMWPE composites for joint implant sockets
Topic(s) : Special Sessions
Co-authors :
István NEMES-KÁROLY (HUNGARY), Gábor SZEBÉNYI (HUNGARY)Abstract :
Improving living conditions and health achievements have led to a significant increase in our average life expectancy. As a result, we use our bodies much longer, causing them to age and wear out. This wear and tear is compounded by the fact, that modern lifestyle places increased demands on our bodies, putting our joints and skeletal systems under severe strain. The challenges of repairing the damage caused by these factors must be addressed by the interdisciplinary disciplines of medicine and engineering. One solution for destroyed joints is the implantation of joint implants, which is one of the most successful surgical procedures [1].
For our joint implants, where some kind of movement is required, the most commonly used design is the metal-polymer artificial joint. This usually means that one of the surfaces that move on top of the other is a metal alloy of some kind, while the other is a plastic - usually ultra-high molecular weight polyethylene (UHMWPE). This combination is the gold standard up to date, but unfortunately, like all engineering structures, they have a lifetime and will eventually wear or excessively deform and need to be replaced during a revision surgery procedure. The most common cause of failure is wear of the UHMWPE, and a very significant proportion of revision surgery causes - inflammation, loosening, Willert polyethylene disease - are also attributed to this [2]. In order to preserve the quality of life of patients and to maintain joint function for as long as possible without complaints. To achieve this goal, further development of UHMWPE inserts is necessary.
At present, the most commonly used UHMWPE inserts are raw, irradiated or vitamin E added, produced by sintering from UHMWPE powder, as this is the only way to process UHMWPE. However, a few years ago, medical-grade UHMWPE fibre appeared on the market and is nowadays mainly used as a suture material. In our research we have prepared composites by sintering from medical grade UHMWPE matrix and Dyneema UHMWPE fibres in neat form and in an irradiation-crosslinked form to provide a wider processing temperature window. In the course of our research, we developed the appropriate manufacturing technology for the production of both plain homocomposite and irradiated reinforcement homocomposite test specimens. We have tested the specimens by differential scanning calorimetry to investigate the fabrication parameters. We then compared the creep and stress relaxation properties of the homocomposite specimens with those of UHMWPE used for implants.
The hardness and wear properties of the homocomposite samples were investigated, first with a pin-on-disk tribometer and then with a multi-axis joint simulator. The wear was examined using a 3D scanner and a confocal microscope and compared with the wear of conventional UHMWPE specimens.
For our joint implants, where some kind of movement is required, the most commonly used design is the metal-polymer artificial joint. This usually means that one of the surfaces that move on top of the other is a metal alloy of some kind, while the other is a plastic - usually ultra-high molecular weight polyethylene (UHMWPE). This combination is the gold standard up to date, but unfortunately, like all engineering structures, they have a lifetime and will eventually wear or excessively deform and need to be replaced during a revision surgery procedure. The most common cause of failure is wear of the UHMWPE, and a very significant proportion of revision surgery causes - inflammation, loosening, Willert polyethylene disease - are also attributed to this [2]. In order to preserve the quality of life of patients and to maintain joint function for as long as possible without complaints. To achieve this goal, further development of UHMWPE inserts is necessary.
At present, the most commonly used UHMWPE inserts are raw, irradiated or vitamin E added, produced by sintering from UHMWPE powder, as this is the only way to process UHMWPE. However, a few years ago, medical-grade UHMWPE fibre appeared on the market and is nowadays mainly used as a suture material. In our research we have prepared composites by sintering from medical grade UHMWPE matrix and Dyneema UHMWPE fibres in neat form and in an irradiation-crosslinked form to provide a wider processing temperature window. In the course of our research, we developed the appropriate manufacturing technology for the production of both plain homocomposite and irradiated reinforcement homocomposite test specimens. We have tested the specimens by differential scanning calorimetry to investigate the fabrication parameters. We then compared the creep and stress relaxation properties of the homocomposite specimens with those of UHMWPE used for implants.
The hardness and wear properties of the homocomposite samples were investigated, first with a pin-on-disk tribometer and then with a multi-axis joint simulator. The wear was examined using a 3D scanner and a confocal microscope and compared with the wear of conventional UHMWPE specimens.