A Lithuanian healthcare company has leveraged the metrology scanning solutions of Nikon Metrology to produce patient-specific hip implants.
Ortho Baltic sees quality assurance as the key to better understand additive manufacturing and the products it manufactures with the technology, namely patient-specific implants, endopirostheses and surgical guides. The company uses a multi-sensor coordinate measuring machine (CMM), which includes a laser scanner in conjunction with a micro-CT (computed tomography) system, all supplied by its partner, Nikon Metrology. The centre previously used the metrology solutions of Nikon to produce jaw implants, and has now endeavoured to offer a similar service to patients who need hip replacements and other treatment.
With the ALTERA CMM, which boasts a LC15Dx laser scanner, Ortho Baltic can inspect the quality of 3D printed implant surfaces and screw holes in quick time. Meanwhile, the XT H 225 CT is used to assure the quality of the internal structures, as well as the correlation of geometry between CAD implant model and the manufactured part.
And since these products need to befit the patient as well as possible, the assurance that the utensils being used are of good quality and function is paramount.
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A 3D-printed acetabular implant being inspected using the Nikon Metrology LC15Dx laser scanner.
“3D printing is a complicated technology and there is a big variation in processing parameters, so predicting the quality and geometry of printed objects is quite a challenge,” said Paulius Luksevicius, Engineer of Mechanics. “Patient-specific implants are a bespoke treatment solution, which means that the surgery must be ‘pre-planned’ virtually so the implant can simply be put in place. To be able to execute the virtual plan, it is vital to be 100% sure that implant geometry is exactly the same as the CAD model and that the holes are machined to high accuracy.
“To fulfil these goals, we use a variety of metrology equipment. The CMM with laser scanner is irreplaceable when we need to perform fast checks after each manufacturing and post-processing stage, especially to check spherical surfaces, bearing surfaces and hole angles.”
The production of patient-specific hip implants, unlike standard modular versions, sees the design done as a single device with anatomically adapted surfaces, which adapts the implant to the bone, rather than vice-versa. During surgery, the need to shape the bone to adapt it to the implant is removed, as is the need to use bone cement, meshes and augments to fill bone defect.
Designed using virtual anatomical bone models obtained from medical CT scans, the implants are then manufactured using direct metal laser sintering. Then, the implants go through a post-processing phase, which can include heat treatment, surface polishing and milling for screw holes. These processes are repeated until the physical implant matches exactly the desired virtual design. Here, the LC15Dx laser scanner is used to show quickly how well the physical part matched the virtual model.
Nikon Metrology’s inspection solutions have proved particularly helpful to Ortho Baltic. The Lithuanian medical centre highlights the Nikon Metrology LC15Dx’s ability to scan reflective and multi-material surfaces thanks to the enhanced sensor performance (ESP) technology. Speed, accuracy and data quality is maintained by intelligently adapting laser settings for each measured point. Meanwhile, probing error is comparable to that of tactile inspection (1.9 μm) and data is fast at 70,000 points per second. Because of these capabilities, Ortho Baltic sees the LC15Dx as the ideal tool for inspecting the complex parts it uses as part of its service.
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Close-up of the acetabular implant.
“The Nikon solution offers more in-depth knowledge of what we are manufacturing and gives better precision and understanding of 3D printing errors and deviations,” Luksevicius adds. “It means we achieve superior product quality and avoid problems during operations. Implants with Nikon quality assurance are more reliable and it is easier to prove their worth.
“Often our quality control laboratory receives inquiries from other manufacturers in the medical sector and other industries to perform geometry inspection for them.”