1 Metal on polyethylene total hip replacement.

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... with a series of studies in the 1970's in Goteborg (23-26); thereafter, the conventional hip replacements were generally composed of a titanium femoral stem, a metal femoral head (mostly Co-Cr-Mo alloy) articulating with an Ultra-High Molecular-Weight Polyethylene (UHMWPE) liner, most frequently supported by a titanium acetabular shell ( Fig. 1.1). The lower mechanical behavior of polyethylene produced the generation of wear debris that led to clinical complications involving inflammation and bone resorption (27). To avoid these problems, second generation MoM articulations were developed in the 1990s ( Fig. 1.2). The articulating surfaces in the femoral head and acetabular cup ...

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... (UHMWPE) liner, most frequently supported by a titanium acetabular shell ( Fig. 1.1). The lower mechanical behavior of polyethylene produced the generation of wear debris that led to clinical complications involving inflammation and bone resorption (27). To avoid these problems, second generation MoM articulations were developed in the 1990s ( Fig. 1.2). The articulating surfaces in the femoral head and acetabular cup in MoM implants are composed 60-65% of cobalt, 27-30% chromium, 5-7% molybdenum and 2-5% other traces elements as manganese, silicon, iron, nickel and carbon (Co-Cr-Mo) (28)(29)(30). Through the use of new technologies, it was possible to obtain smoother surfaces ...

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... analyses demonstrated that the increase of friction between larger contact surfaces would not be significant if the clearance between the surfaces is decreased (31,43). The possibility of having a metallic femoral head, articulating directly over the metal of the acetabular cup, allowed the development of hip resurfacing (Fig 1.3), a surgical procedure that involves minimal bone removal on the femoral head. The design was especially indicated for young active patients, with a good outcome after 5 years of surgery, and a lower hospital stay (2.3 days) compared with total hip replacement (4.1 days) (1,44,45) Due to those advantages, 35% of THA performed between 1998 and 2008 in the US and Europe were MoM implants, and it is estimated that more than a million of them were implanted (15,46). ...

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... technological improvement to hip prostheses was the development of modularity of the femoral components (Figure 1.1). The possibility of selecting independently the femoral stem and head, and (in some implants design) the femoral neck, allowed the surgeons to give a better-fitted solution in all clinical conditions such as angles and length, allows reduction in the inventory in hospitals and manufacturers, and simplifies revisions since not all parts need to be removed (50). ...

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... surgery patients (out of 25). Out of the 18 MoP samples with ALTR, six corresponded to the regular amber-translucent color (Fig. 4.1 A), nine of them had an opaque cafe-au-lait color with a creamy-sandy consistency (Fig. 4.1 B), and three were dark grey color with fluid consistency (Fig 4.1 C). The samples obtained from MoM patients were mostly ...

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... surgery patients (out of 25). Out of the 18 MoP samples with ALTR, six corresponded to the regular amber-translucent color (Fig. 4.1 A), nine of them had an opaque cafe-au-lait color with a creamy-sandy consistency (Fig. 4.1 B), and three were dark grey color with fluid consistency (Fig 4.1 C). The samples obtained from MoM patients were mostly ...

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... surgery patients (out of 25). Out of the 18 MoP samples with ALTR, six corresponded to the regular amber-translucent color (Fig. 4.1 A), nine of them had an opaque cafe-au-lait color with a creamy-sandy consistency (Fig. 4.1 B), and three were dark grey color with fluid consistency (Fig 4.1 C). The samples obtained from MoM patients were mostly amber-translucent; ...

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... Brown spotted vesicles: observed in the cytoplasm of macrophages. These structures corresponded to hemosiderin as it was confirmed through SEM-EDX due to their high iron content (Fig. ...

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... wear particles were observed in 57 % (Fig. 4.11). Under BSE looked like bright spots, which was consistent with their elevated metal content (figure ...

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... corrosion particles were analyzed: 26 MoM (12 patients), 21 in MoP (8 patients), and 5 controls (3 patients). All the particles showed a major composition of chromium (61.6 % MoM, 55.2 % MoP, St. dev +-7.1 % and +-6.82 % respectively), with minimal or no cobalt and molybdenum. The particles had a high content of calcium and phosphorous (Fig. 4.12). Although the general composition of these particles is similar among the cases, the particles in MoM cases revealed a higher amount of Cr than MoP (p < 0.05). These results suggest that wear particles correspond to relatively un-corroded particles generated by wear of the articulating surfaces or by fretting in the modular joints. The ...

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... order to analyze the crystal structure of the corrosion particles found in the tissues, we In the analysis of XRD, the particles displayed a weak signal at 1.43 Å (Fig. 4.14), which prevents determining a specific crystal structure, and suggests that these particles are mostly amorphous but some crystalline elements could be contained in the particles. This observation is similar to the one that has been described at the interface between the metal surfaces in the modular joints ...

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... Co and Cr. The results of this study showed that synovial fibroblasts respond to the presence of metals through the secretion of cytokines. These cytokines are capable of activating human endothelium and inducing chemotaxis of human monocytes, which are starting points of inflammation, and may be the triggering event for the development of ALTRs (Fig. ...