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Chapter 9258to be an asset, even when reduced total femoral head penetration was observed at a 3-year follow-up.(48)Tissue IntegrationAnother important aspect of an implant (endoprosthesis) besides biocompatibility is tissue integration. Osseous integration is the apparent direct attachment of bone to a biocompatible material without intervening tissue. A recent study(49) found that there is a direct relationship between the roughness of the titanium surface and the stimulation of bone formation, with pores measuring 600 µm (macroroughness) show greater bone ingrowth compared to a smaller (100–300 µm) pore diameter.(50–53) Secondly, sandblasted, large-grit, and acid-etched (SLA) surfaces (micro roughness) show increased osseointegration compared to smooth surfaces.(50) It is believed that these mechanical and chemical abrasions induce the adsorption of fibronectin and other proteins that, in turn, trigger osteoblasts to form focal adhesions via an integrin-mediated mechanism.(54,55) Removing surface contaminants while imparting wettability is equally useful and may trigger hard tissue formation as well.(56–58) Further, plasma activation induces the initial adhesion of proteins and bone marrow cells. Unfortunately, steam sterilization after plasma activation completely removes this increase in wettability. In comparison to osseointegration, soft tissue integration is less precisely defined. It is rather described as “a strong soft tissue-implant seal … with a thin capsule containing few inflammatory cells and fibroblasts…and collagen fiber orientation preferably oblique to the implant surface or randomly oriented”.(59) A surface roughness Ra value between 0.5 and 1 µm has been shown to induce soft tissue adhesion. Smoother surfaces, with the exception of acidpolished and anodized titanium (Ra = 0.2 µm), prevent adhesion. Micro-arc oxidation (also known as plasma electrolytic oxidation) significantly increases the percentage of soft tissue adhesion.(60) Similarly, a fibroblast growth factor-2/apatite composite coating applied by immersion (for 48 h) induced significantly less inflammation and yielded promising skin-screw interfaces.(61) Both processes have a low cost-effectiveness.(59)Nikolas de Meurechy NW.indd 258 05-06-2024 10:14