Ceramic femoral ball heads

These restrictions notwithstanding, yttria-stabilised zirconia polycrystal (Y-TZP) femoral heads presently make up about 25% of the total annual number of hip joint implants in Europe and 8% in the United States. Between 1985 and 2001 more than 400000 Y-TZP femoral heads were implanted worldwide. However, safety concerns continue to plague zirconia femoral heads. The U.S. Food and Drug Administration (FDA, 2013) issued a safety alert in August 2013 to orthopaedic surgeons that the French manufacturer St Gobain Desmarquest had recalled an unimplanted inventory of zirconia femoral heads that were found to fracture at a higher rate than expected in some patients 13-27 months after implantation. 

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Femoral ball heads of hip endoprostheses made from bioinert ceramics such as alumina or zirconia have to sustain high mechanical stresses, resorp-tion/corrosion by aggressive body fluid and abrasive wear over the lifetime of the implant in the human body of 15-20years. Some important properties of ceramic femoral ball heads are listed in Table 2.3 (Willmann, 1995). Mechanical properties of alumina and zirconia are discussed in Chapter 4.1. 

Table 2.3 Important mechanical and functional properties of ceramic femoral ball heads.

Performance Requirements and Quality Control of Ceramic Femoral Ball Heads... 

Figure 2.6 shows three standard diameter sizes (22, 28 and 32 mm) of zirconia femoral ball heads with laser markings to identify the individual part unequivocally. For example, the top ball carries the identification code 32-12/14M 96 Z 8179 that refers to a diameter of 32 mm, an inside taper of 12/14 mm, a medium neck length M, the year of manufacture (1996), the type of ceramics Z for zirconia, as well as the production number 8179. With this complete identification, it is possible to establish a quality test protocol and trace the history of this part that may... 

The reliability of ceramic femoral heads is closely related to their mechanical properties. Previously, measurement of the load to fracture of 107 explanted alumina (Biolox ) femoral ball heads did not reveal any fatigue of the material (Willmann, 1998). This can be related to the very favorable relationship between... 

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