Ceramic Ball Heads Research Articles

Simulator test of artificial joints

This report deals with the characteristic changes in frictional torque of a ceramic (alumina and zirconia) ball head against an UHMWPE socket which was subjected to intense creep deformation under continuous loading in 37 °C pseudo-extracellular fluid (PECF). As a result, the ceramic ball heads exhibited lower friction compared with a more usual metal ball head. A static vertical load caused much greater frictional torque compared with vibrating loading condition. The zirconia ball head withstood a pulsating fatigue load of 12 kN for up to 10 9 cycles.

Investigations into the mechanical reliability of ceramic femoral heads for hip joints

This paper reports the findings of a finite element analysis applied to the study of ceramic femoral ball heads. The objective of carrying out these analyses was to assess the shape design and loading conditions applied to specific femoral heads and to capture the stress fields developed when they are subjected to idealized test conditions. Two designs were considered, these being the existing Biolox keyhole shape, manufactured by Cerasiv, Medical Products Division and an alternative design with a flat top internal hole. For each of these designs, three load cases and two types of frictional contact were considered. It is shown that the key hole shape with full taper contact conditions together with the higher value of surface friction produce the lowest tensile stress fields in the ball head hence increasing mechanical reliability.

Research and development of alumina and zirconia artificial hip joint

The object of the experiments was to discover the static and dynamic load-carrying capacity of a prosthetic system consisting of a titanium alloy stem, zirconia ceramic ball head and UHMWPE (ultra-high molecular weight polyethylene) socket molded in the ceramic shell, the latter two were both of 22 mm in diameter. The components of the artificial hip joint were placed in a vertical position and load was applied, alternating between 0 and 10 kN and then 12 kN with a frequency of 30 Hz under Ringer's solution up to 10 7 cycles respectively. After 2 × 10 7 cycles there was no sign of damage to be observed among the system tested using the joint simulator. This seems to be a very high safety factor compared with loads occurring in vivo.

Bruchlast keramischer Kugelköpfe von Hüftgelenkprothesen - Fracture Load of Ceramic Ball Heads of Hip Joint Prostheses

To ensure the stability of ceramic ball heads of hip joint prostheses over the long term, both standards for the material and FDA-regulations for the components have been established. In this paper the philosophy underlying design and reliability is discussed. On the basis of fracture loads determined for Biolox ball heads the high level of stability and reliability that has been achieved and can now be guaranteed, is demonstrated.

Biologic Fixation of a Press-Fit Titanium Hip Joint Endoprosthesis

The rectangular cross section of a straight-stem prosthesis makes a primary stable, rotation-safe fixation possible that is independent of the individual form of the femur. Due to the curvature of the femur, a three-dimensional large-area anchorage is achieved along the entire prosthesis length in the corticalis as well as in the spongiosa. The titanium-aluminum-niobium alloy is extremely biocompatible and enables the fast ongrowth of newly formed osseous tissue to act as secondary stabilization. Pathohistologic examinations on the prostheses of deceased patients show that this osseointegration leads to a complete osseous ingrowth of the implant. The average surface roughness of 3-5 microns, with which the entire prosthesis length is structured, supports this osseointegration. This microroughness is, therefore, totally sufficient for the primary and secondary stabilization of the implant. The osseous fixation of the prosthesis over the entire stem length guarantees a physiologic and functional load transmission to the surrounding femoral bone, thus avoiding stress shielding. The combination of a ceramic ball head with a polyethylene cup results in less wear than is the case with the customary metal-polyethylene combination and, thus, prolongs the life span of artificial hip joints. Good results in the future can only be expected in osseointegrated implants with minimal wear of the synthetic material.

Tissue reactions to titanium endoprostheses: Autopsy studies in four cases

Four cementless prosthetic hip implants of Ti 6Al 4V alloy with and without longitudinal grooves and Al 2O 2 ceramic ball heads, with implant periods of 3, 4, 5, and 10 months, were sectioned and examined histologically in undecalcified thin ground sections. Especially on the medial and lateral sides of the prostheses, there was direct bone-to-metal contact without interposed connective tissue, spreading to the dorsal and ventral areas of the prosthesis shaft, which was considered osseointegration. This is based mainly on the technique of implantation with primary stability in the cortical bone by press-fit and on the bioinertness of the titanium alloy. Ungrooved prosthesis areas seem to favor bone growth at the shaft. The secondary bone ring, occurring on the dorsal and ventral areas of the prosthesis, with evidence of further bone remodeling with the passage of time, indicates that osseointegration is a dynamic process that continues to improve prosthetic stability.

Concept and material properties of a cementless hip prosthesis system with Al2O3 ceramic ball heads and wrought Ti-6Al-4V stems.

A cementless total hip system of modular design is presented. The design of the stem provides for a firm seating on the cortical bone over a large area. Therefore primarily stable fixation is accomplished. The stem in seven different sizes is made of hot forged Ti-6Al-4V Protasul-64 WF alloy of high corrosion fatigue strength. The Biolox ceramic ball with three different neck lengths is connected to the high strength stem by means of a special selflocking conical spigot with a structured surface. The ceramic ball is combined with a polyethylene screw socket in four different sizes, designed by Endler and anchored in the acetabulum without acrylic cement. This hip prosthesis system has proved itself in clinical application since 1979.