Femoral ball heads

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.

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... 

Figure 2.6 Femoral ball heads, manufactured from zirconia with laser-engraved identification (Heimann and Willmann, 1998).

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

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... 

---