Fatigue behavior of Zirconia hip joint heads: Experimental results and finite element analysis

Abstract

Crack propagation in a commercial surgical grade zirconia ceramic was performed under static and cyclic loading. The slow crack growth (SCG) parameters were determined in both cases. The results reveal the existence of threshold values of applied stress intensity factor, for both static and cyclic loadings, below which no slow crack growth occurs. Such threshold values represent one of the best advantages of the present zirconia ceramic compared with other ceramic materials used in orthopedics, which could lead to a strong enhancement of implant lifetime. This threshold value was also identified by cyclic fatigue tests performed on zirconia femoral heads. From a new statistical approach based on the Monte Carlo method, the knowledge of SCG behavior, and the help of finite element analysis, an estimate of the lifetime prediction has been made and discussed.

Fracture Propagation Propensity of Ceramic Liners During Impingement-Subluxation

“…Impact seating of the ceramic head onto the metal trunnion (“Morse” taper) of the femoral neck creates regions of high circumferential hoop stress, which sometimes tended to cause crack propagation and ultimately critical fracture. However, extensive investigation into the design of this ceramic-metal interface, by experimental [6–8], analytical [9] and finite element (FE) [10, 11] techniques, identified critical design factors which increased fracture propensity. This led to optimization of parameters such as component size, shape, taper angle, surface roughness and neck length.…”

Threshold intensity factors as lower boundaries for crack propagation in ceramics

“…4: 9.4 ± 1.5 MPa·√m) which is about three times larger than this of alumina. Values in the literature for zirconia are up to about 8 MPa·√m [16], compared with 5.4 MPa·√m and [5]: 5.0 ± 0.2 MPa·√m [17] for alumina. Naturally, this is a significant advantage when operations near the critical stress of a material are involved.…”

Alternative bearing surfaces in total hip arthroplasty

“…The finer grain size of zirconia, in part, contributes to its improved fracture toughness and bending strength as compared with alumina [89]. However, such material properties are best maintained through yttria stabilization of zirconia (yttrium-stabilized tetragonal polycrystalline zirconia; [Y-TZP]), thereby limiting unstable phase changes between its monoclinic, cubic and tetragonal forms [90,91]. Laboratory studies conducted to assess wear rates of zirconia femoral balls coupled individually to polyethylene, alumina or itself have provided variable results for the latter two articulations [85,92].…”