The Influence of the Stand-Off Distance on Surface Topography and Related Roughness Values for Titanium Implant Processing by Pure Water Jet

In cementless arthroplasty, the prosthetic surface is intentionally roughened to enhance the initial mechanical stability and to facilitate long-term osseointegration—the process by which bone gradually grows onto and integrates with the implant over time. For this goal this study investigates the processing of titanium implant surfaces, focusing on the achievable surface topography and roughness variations resulting from changes in stand-off distance (jet length) when using a pure water jet (without abrasive). This particle-free processing approach serves as an alternative to the conventional method of sandblasting followed by chemical etching. By eliminating the use of abrasive particles, this technique entirely mitigates the risk of implant failure caused by undetected particle contamination on or beneath the surface. The ability to achieve the desired surface topography depends on the jet profile as it impacts the titanium surface, as well as the disintegration of the water jet, which exits the nozzle as a compact stream but subsequently breaks into discrete fluid packets or, depending on the nozzle type, droplets. The dynamics of this jet profile and impact behavior evolve with increasing stand-off distance. In this laboratory study, the stand-off distance was varied as a processing parameter and its influence on the resulting surface characteristics was quantitatively assessed. The ultimate goal of optimizing the implant surface topography is to enable the use of titanium components as cement-free implants, ensuring direct contact between the implant surface and bone.