Despite the superior tribological properties of ceramic, these bearings are associated with a unique complication—fracture. Since the initial development of ceramics, specific efforts have been made to lower the fracture rate. Overall, with each generation of ceramics, there have been improvements in the manufacturing and regulatory processing leading to a smaller grain sizes and change in composition, hence producing a more fracture-resistant material. An evaluation of a large number of ceramic heads from the first three ceramic generations demonstrated a progressive reduction in the fracture rate [2]. Similarly, a clinical evaluation of data acquired from the French national agency for safety of drugs and medical products (Agence nationale de sécurité du médicament et des produits de santé) determined improved fracture rate of the femoral head between the third and fourth generation of ceramics [3]. However, this evaluation concluded that there were no significant changes in the rate of fracture for the acetabular liner. Overall, with contemporary bearings the rates of ceramic fracture are extremely low [1]. It is estimated that with the fourth generation of ceramic the fracture rate is very low with liner fractures being more common than head fracture (0.03% and 0.003%, respectively) [3]. The fracture rates of various studies reporting on ceramic fractures are summarized in Table 14.1. Due to the fact that ceramic fractures are relatively uncommon with the later generations of ceramics, they are generally reported as sporadic case reports and smaller retrieval studies. This may document higher fracture rates up to 13.4% [4] which may give a misleading estimate to the actual fracture rates. Despite the very low rate of fractures associated with modern ceramics, it is still a documented phenomenon, which requires further surgical intervention.

Ceramic fractures can occur either on the head or on the liner, and can be spontaneous or as a consequence of trauma. Risk factors can be classified as those related to implant design, technical factors, implant positioning, and/or material characteristics.

The clinical presentation of a broken ceramic component may be either symptomatic or asymptomatic. Symptomatic presentation can be varied and may present as an acute sharp pain, or an audible sound (squeaking/other form of noises) which may vary throughout the hip arc of motion. Patient assessment should include a thorough history, physical examination, and radiographic assessment. Clinical examination may reveal limited range of motion and an appearance of clunks, grinding, and/or new noises. Radiographic assessment is conducted via anteroposterior (AP) pelvis and hip radiographs which may demonstrate ceramic particles embedded in the synovium and joint capsule (Fig. 14.1). In addition, an eccentric position of the head can be detected. A CT scan should always be performed to further assess the fracture pattern which has a special importance if the liner fracture is suspected, as this is more difficult to detect clinically [19]. Moreover, CT is beneficial for assessing component positioning and plays an important role in the evaluation of patients with newly appeared noise such as squeaking. The appearance of squeaking has been shown to have a clinical association with ceramic fractures [20, 21]. Joint aspiration and synovial fluid microanalysis were described as early diagnostic tools for ceramic liner fractures [17]. Ceramic fragments with a 5 μm diameter were associated with the presence of liner fractures. However, the role of aspiration in early detection of ceramic liner fractures requires further clinical assessment using larger patient cohorts.

In the case of a ceramic fracture, revision surgery is always recommended and should be performed urgently. During revision surgery, multiple irrigations of the joint and a complete synovectomy should be performed in order to reduce the ceramic particles within the joint, ultimately reducing the risk of third-body particle wear. Following removal of the ceramic particles, inspection of the trunnion and the cup should be conducted. In the case of ceramic liner fracture, the acetabular metal shell will be damaged or deformed and should be replaced. In the case of ceramic head fracture, the trunnion most probably will be deformed due to its direct loading by the ceramic acetabular liner. In these cases we advocate for stem replacement. In rare cases where the femoral trunnion is macroscopically undamaged and the stem is well fixed, it is possible to consider retaining the stem as its removal can be associated with increased patient morbidity and impairment in hip function.

Generally, the literature supports the use of taper sleeves with a new head if the surface of the trunnion is not macroscopically damaged. A damaged trunnion surface will require stem removal and replacement [22, 23]. If a damaged trunnion is retained, it is theorized that it will lead to an uneven load distribution on the femoral head which can lead to ceramic fractures due to point loading [2, 24].

If the acetabular or femoral components are maloriented, removal of the component is advocated.

For bearing selection in revision surgery, the literature is in agreement that a CoC or a CoP bearing should be utilized [25, 26]. A conversion to a MoP is not recommended due to the scratching effect of the ceramic particles on the metal femoral head potentially leading to excessive wear of the head and the polyethylene [25, 26]. Studies evaluating the use of CoC in revision THA show good clinical results [27, 28].

Ceramic-on-ceramic bearings were developed in the 1970s to reduce wear and osteolysis traditionally associated with metal-on-polyethylene bearings . The two tribological properties important about CoC bearings are their hardness and wettability. The higher hardness allows ceramics to be highly polished and produce a lower surface roughness, hence providing a high resistance to scratching and wear. However, ceramics are a brittle material. Good wettability provides a uniform thin fluid across the bearing interface, which eliminates the frictional forces acting across the bearing.

Ceramics are a nonmetallic material that can be classed into crystalline or amorphous structures [29]. The localized density variation, grain size distribution, and porosity of ceramics identify the variation in their mechanical properties [29]. In the early 1970s, alumina was the chosen oxide ceramic. Clinical publications of alumina CoC demonstrated high clinical failure rates predominately due to aseptic loosening, and a high rate of ceramic fractures [30–32]. This was mainly associated with the lack of ingrowth surface and the variability in the manufactured material standardization of the alumina [8, 33].

In 1985, the development of zirconia was promoted due to its superior biomechanical strength in comparison to alumina [34, 35]. Zirconia has three different phases known as monoclinic, tetragonal, and cubic. The tetragonal stage is the strongest biomechanically; however it is unstable. Conversion from a tetragonal to a monoclinic phase creates a toughened ceramic. However, it is associated with volumetric change. Therefore, stabilization with yttrium oxide is used in combination with zirconia. The use of yttrium provides small tetragonal particles to exist within a stable state below the transformation temperature. In case of a crack formation, the tetragonal grains within the matrix will fill the void formed of the crack while constricted by neighboring grains which are still in the tetragonal stage. This fabrication process improved fracture resistance; however it produced an increase in surface roughness potentially leading to excessive wear [36, 37]. Early clinical experiences with zirconia/alumina and zirconia/zirconia generated large volumetric wear. Therefore, zirconia could be only coupled with polyethylene [38, 39]. By the end of the twentieth century and due to these wear characteristics zirconia has been withdrawn from the market [40, 41].

The high fracture toughness of zirconia and the high hardness and good wear characteristics of alumina are the two key material properties which are desired to be preserved in modern ceramics. Modern ceramics undergo better material control and improved manufacturing processes which optimize the grain sizes and density. Currently, alumina matrix composite is the dominating ceramic in clinical use. Alumina FORTE (BIOLOX forte, CeramTec AG, Plochingen, Germany) is a third generation of ceramic material which is composed of ultrapure alumina, zirconia, and yttrium. To further improve the fracture resistance of ceramics, a fourth generation of ceramic was introduced, which included the addition of strontium oxides in the form of platelets within the alumina matrix. The impregnation of the strontium platelets deflects the path of crack propagation, hence improving the fracture resistance, as a higher energy is required to cause catastrophic crack propagation.

Table 14.2 represents a variety of clinical studies which have reported on ceramic fractures for both the acetabular liner and femoral heads . However, as discussed previously, the fracture rate fluctuates in relation to the cohort size.

Results of revision surgery due to ceramic fracture are variable. A multicenter study reported on the results of 105 revision THAs due to early-generation ceramic head fracture. At a mean follow-up of 3.5 years 33 patients (31%) needed further revisions. The survival rate was significantly worse when the cup had not been changed, when the new femoral head was made of stainless steel, when a total synovectomy had not been done, and when the patient was less than 50 years old [26]. Another study reported on the long-term results of eight patients who had revision THA due to ceramic fracture. At 10.5 years following revision surgery none of the patients had further revision surgery. A link between the results and a thorough synovectomy performed at the time of revision surgery was suggested [52].

The outcomes of revision surgery with newer generation of ceramics are limited. A study evaluating 24 THAs undergoing revision of third-generation CoC due to fracture demonstrated unfavorable results when the femoral stem was retained as compared to patients in which the stem was changed. The authors suggested that a possible explanation is related to the fact that newer generations of ceramics are harder and therefore can create larger damage to the Morse taper; thus the authors advocated for stem exchange [23].

Following diagnosis of the fractured liner, the patient underwent revision surgery. During the procedure, the ceramic insert was found to be broken and an effort was made to remove all fragments of ceramic, including an extensive synovectomy . There were no signs of neck-to-rim impingement. The acetabular cup was removed and a new cup was fixed with two screws followed by the insertion of a ceramic acetabular liner. The femoral stem taper was evaluated and showed no macroscopic surface deformation. As such, it was fitted with an adapter sleeve and a new ceramic femoral head (revision ceramic head). Following revision surgery, the hip noises disappeared and the patient had pain-free full hip range of motion. Postoperative radiographs were acceptable (Fig. 14.3). The broken ceramic fragments and the ceramic head were sent to a research laboratory and were further analyzed. The femoral head demonstrated a characteristic stripe wear pattern and the overall volumetric wear rate was high (19 mm³). The regions of wear showed a roughened surface with grain pullout. The ceramic liner fragments similarly had a roughened appearance when examined under a scanning electron microscope . The ceramic liner showed a characteristic wear region on the edge of the ceramic liner representing edge loading which is commonly observed in ceramic retrievals.

During the manufacturing process of a ceramic acetabular liner, a sharp edge is generated inside the rim [53]. During hip movement, the femoral head loads against the sharp edge of the cup resulting in edge loading [8]. This in turn will lead to the formation of long narrow area of damage (strip wear), along the femoral head and the edge of the cup (Fig. 14.4). Stripe wear has been reported for first- and second-generation ceramic bearing, and initially was associated with steep cup angles, revision surgery, and young patients [54]. Since no cup coating was found in these early generations of ceramic bearings, component migration was common. Thus, it was initially hypothesized that the formation of the strip wear was linked to cup migration. However, similar stripe pattern can be seen in well-fixed and well-positioned third-generation ceramic articulations [55]. A retrieval study of third-generation ceramic bearings demonstrated that wear on the acetabular component always involved the edge [53]. The location of the wear patch may indicate whether edge loading occurs during deep hip flexion (posterior edge loading) or during walking and hip extension (anterior superior edge loading) [53]. It was also observed that insufficient anteversion will lead to posterior edge loading while anterior edge loading is associated with increased cup anteversion and inclination [53, 56]. Posterior edge loading is more commonly seen in comparison to anterior edge loading, and may be associated with micro-separation of the femoral head during the swing phase [55]. Neck-to-rim impingement, bony impingement, medial soft-tissue bulk, and reduction in soft-tissue tone can lead to subluxation-relocation motion and this can produce a wider stripes and scratches along the head [53]. Overall, it was suggested that edge loading is a normal mechanism in CoC articulations. The wear produced by edge loading is unavoidable [45, 53, 57] but considered clinically insignificant as the produced wear volumes are very low to generate osteolysis [8].