Key result
A novel in vitro technique combining micro-CT and digital volume correlation measured glenoid bone strain under 1500 N loading with an average accuracy of 694.3 µε and precision of 440.3 µε.
A novel in vitro technique using micro-CT and digital volume correlation accurately and precisely measures glenoid bone strain after anatomical total shoulder arthroplasty.
Enables precise in vitro glenoid strain quantification after shoulder arthroplasty; leaves open in vivo validation before clinical use.
Glenoid implant loosening remains a major source of failure and concern after anatomical total shoulder arthroplasty (aTSA). It is assumed to be associated with eccentric loading and excessive bone strain, but direct measurement of bone strain after aTSA is not available yet. Therefore, our objective was to develop an in vitro technique for measuring bone strain around a loaded glenoid implant. A custom loading device (1500 N) was designed to fit within a micro-CT scanner, to use digital volume correlation for measuring displacement and calculating strain. Errors were evaluated with three pairs of unloaded scans. The average displacement random error of three pairs of unloaded scans was 6.1 µm. Corresponding systematic and random errors of strain components were less than 806.0 µε and 2039.9 µε, respectively. The average strain accuracy (MAER) and precision (SDER) were 694.3 µε and 440.3 µε, respectively. The loaded minimum principal strain (8738.9 µε) was 12.6 times higher than the MAER (694.3 µε) on average, and was above the MAER for most of the glenoid bone volume (98.1%). Therefore, this technique proves to be accurate and precise enough to eventually compare glenoid implant designs, fixation techniques, or to validate numerical models of specimens under similar loading.
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Boulanaache et al. (2020) studied Glenoid bone strain after anatomical total shoulder arthroplasty (n=1). In vitro 1500 N axial loading using a custom device vs. Unloaded state was evaluated on Strain accuracy (mean absolute error) and precision (standard deviation of absolute error). A novel in vitro technique combining micro-CT and digital volume correlation measured glenoid bone strain under 1500 N loading with an average accuracy of 694.3 µε and precision of 440.3 µε.
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