Medical implant
manufacturing and control
Medical implant manufacturing requires a very high level of quality
control, in particular when parts are intended for long-term implantationin the spinal region as shown in Figure 1. The inspected part presented
inhomogeneous marks of undefined origin, which were only revealed at thefinal visual inspection. Acceptability criteria for visual inspection rely often on
human eye interpretation and are generally poorly described in customer
specifications, which may lead to conflicts regarding parts’ compliance. As far
as machining was involved in the apparition of this defect, regular roughness
analyses might have been helpful to evaluate the marks. However, contact
stylus 2D profilometer marks created on this complex, finished titanium part
would generate a less acceptable defect. Consequently, non-contact opticalsurface profilometry inspection was chosen to point out the defect origin,measure the efficacy of manufacturing changes intended to avoid it and set
a quantitative threshold for non-compliance.

Anthogyr is a French company
founded on 1947 that designs,
manufactures and distributes
a complete range of implants
and instruments to support
professionals in treating millionsof patients across the world. Its
main market is the machining
and assembly of medical devices,including decontaminationand packaging in a clean room
for absolute cleanliness andcontamination control.

Figure 1. Top view of a medical implant (Left). Zoom in at a region

where defects (“stripes”) are shown.
CASE STUDY MEDICAL IMPLANT MANUFACTURING AND CONTROL

1■ Measurements
After studying the optimum acquisition settings for each technique, thecontinuous confocal mode, with a magnification of 20X, and an extended
measurement of 3 fields of view was found to be the most suitable settings
for this study.
Figure 2 shows two topographies, one with defects (non-compliant) andanother one free of defects (compliant). The former one shows few vertical“stripes” that are not evident on the compliant surface.

Figure 2. Top-view of the non-compliant surface topography (top)and the compliant surface topography (bottom).

Figure 3 shows 2D profiles extracted from both topographies. As it can beseen, the non-compliant topography shows a strong waviness component
that is not evident in the compliant surface. Measurements were repeated andthoroughly analyzed with SensoMAP software to identify the most reliable
parameters correlating visual inspection results; parameters such as the Areal
Material Ratio and its Inverse can be easily computed from the Abbot-Firestone
curve, which can be easily obtained using SensoMAP (Figure 4).

Figure 3. Top-view of the non-compliant 2D profile (top) and the compliant 2D profile (bottom).

The red line is an arbitrary threshold for compliance.

2CASE STUDY MEDICAL IMPLANT MANUFACTURING AND CONTROL

Figure 4. The Abbot-Firestone curve is shown in red for the non-compliant (left)

and compliant surfaces (right). It is the cumulative probability density
function of the surface profile’s height and can be calculated byintegrating the profile trace.

■ Conclusions
The 3D optical profilometer S neox allowed machining specialists to identify
the tool responsible for the defect and to follow its wear during serial
production, thus controlling the manufacturing process and improving its
outcome. In particular, the Confocal technique has been proven to be aneffective technique to qualitatively and quantitatively investigate surface
defects.
Extended analysis of compliant and non-compliant parts revealed that
common surface parameters like Sa or Sz were not sufficient to catch
appearance defects accurately enough. A functional parameter was
identified as the most reliable criterion, allowing controllers to undoubtedly
differentiate non-compliant parts when needed.
In addition, further studies might consider more advanced tools such as theS neox Five Axis that would enable the 3D reconstruction of the implant’s
complete shape, which can be of interest for wear analyses, CAD comparison
and/or quality control in further studies.

CASE STUDY MEDICAL IMPLANT MANUFACTURING AND CONTROL

3SENSOFAR is a leading-edge technology
company that has the highest quality standards
within the field of surface metrology
Sensofar Metrology provides high-accuracy optical profilers
based on confocal, interferometry and focus variation
techniques, from standard setups for R&D and quality
inspection laboratories to complete non-contact metrology
solutions for in-line production processes. The Sensofar Grouphas its headquarters in Barcelona, also known as a technology
and innovation hub in Europe. The Group is represented in over
30 countries through a global network of partners and has its own
offices in Asia, Germany and the United States.
HEADQUARTERS

SENSOFAR METROLOGY | BARCELONA (Spain) | T. +34 93 700 14 92 | info@sensofar.com
SALES OFFICES

sensofar.com

CS00-04B-EN-Anthogyr

SENSOFAR ASIA | SHANGHAI (China) | T. +86 021 51602735 | info.asia@sensofar.com
SENSOFAR GERMANY | MUNICH (Germany) | T. +49 151 14304168 | info.germany@sensofar.com
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