Artificial joint to replace damaged body joints.

The functional surface of the joint implant is highly elongated and highly sensitive to contact. Important features are the overall surface's shape distortion and surface roughness, and the intermediate level of the measurement inaccuracy requirement is 20 μm to 50 μm. Due to the contact sensitive surface characteristics, it is important to use low measuring force scanning probes or parallel contactless optics to prevent surface damage. Free curves with free-form surface are a key basis for the comparison of shape differences with CAD data.