Validation of an optical system to measure acetabular shell deformation in cadavers

Abstract

Deformation of the acetabular shell at the time of surgery can result in poor performance and early failure of the hip replacement. The study aim was to validate an ATOS III Triple Scan optical measurement system against a co-ordinate measuring machine using in vitro testing and to check repeatability under cadaver laboratory conditions. Two sizes of custom-made acetabular shells were deformed using a uniaxial/two-point loading frame and measured at different loads. Roundness measurements were performed using both the ATOS III Triple Scan optical system and a co-ordinate measuring machine and then compared. The repeatability was also tested by measuring shells pre- and post-insertion in a cadaver laboratory multiple times. The in vitro comparison with the co-ordinate measuring machine demonstrated a maximum difference of 5 µm at the rim and 9 µm at the measurement closest to the pole of the shell. Maximum repeatability was below 1 µm for the co-ordinate measuring machine and 3 µm for the ATOS III Triple Scan optical system. Repeatability was comparable between the pre-insertion (below 2 µm) and post-insertion (below 3 µm) measurements in the cadaver laboratory. This study supports the view that the ATOS III Triple Scan optical system fulfils the necessary requirements to accurately measure shell deformation in cadavers.

The effect different substrates have on the trueness and precision of eight different intraoral scanners

“…Each IOS scan file was imported then superimposed onto the reference model, using an Initial Alignment and a Best Fit Alignment , considering only the segmented typodont teeth (Figure ). The software's Best Fit Alignment function aligns the test file, and reference file using an iterative closest point algorithm, which has become a standard method for aligning digital 3D files …”

Evaluation of the trueness and precision of complete arch digital impressions on a human maxilla using seven different intraoral digital impression systems and a laboratory scanner

“…This blue light scanner uses multiple camera sources to record the features of the object being scanned. It has been shown to be able to capture data with a very high precision and an accuracy of 3 μm for a jaw sized scan …”

Evaluation of the effect scan pattern has on the trueness and precision of six intraoral digital impression systems

“…A master scan of this model was made to fabricate the master digital model, against which the different scan patterns would be compared for trueness and precision. This scan was taken using ATOS Triple Scan (GOM technologies, Santa Ana, CA), an industrial grade, blue‐light 3D scanner that has been shown to be accurate to 3 μm . This produced a master stereolithography (.stl) file that, when imported into a three‐dimensional (3D) analysis software Geomagic Control (3D Systems, Rock Hill, SC), allowed for alignment of experimental and control .stl files by highest average nodal data‐point overlay; and graphic comparison of the separate scan patterns (Figure ).…”