Digital volume correlation can be used to estimate local strains in natural and augmented vertebrae: An organ-level study.
Digital Volume Correlation (DVC) has become popular for measuring the strain distribution inside bone structures. A number of methodological questions are still open: the reliability of DVC to investigate augmented bone tissue, the variability of the errors between different specimens of the same type, the distribution of measurement errors inside a bone, and the possible presence of preferential directions. To address these issues, five augmented and five natural porcine vertebrae were subjected to repeated zero-strain micro-CT scan (39μm voxel size). The acquired images were processed with two independent DVC approaches (a local and a global one), considering different computation sub-volume sizes, in order to assess the strain measurement uncertainties. The systematic errors generally ranged within ±100 microstrain and did not depend on the computational sub-volume. The random error was higher than 1000 microstrain for the smallest sub-volume and rapidly decreased: with a sub-volume of 48 voxels the random errors were typically within 200 microstrain for both DVC approaches. While these trends were rather consistent within the sample, two individual specimens had unpredictably larger errors. For this reason, a zero-strain check on each specimen should always be performed before any in-situ micro-CT testing campaign. This study clearly shows that, when sufficient care is dedicated to preliminary methodological work, different DVC computation approaches allow measuring the strain with a reduced overall error (approximately 200 microstrain). Therefore, DVC is a viable technique to investigate strain in the elastic regime in natural and augmented bones.
School of Engineering and Architecture, Alma Mater Studiorum - Università di Bologna, Via Terracini 28, Bologna 40131, Italy.
Marco
M
Palanca
School of Engineering and Architecture, Alma Mater Studiorum - Università di Bologna, Viale Risorgimento 2, Bologna 40136, Italy.
Luca
L
Cristofolini
Department of Oncology and Metabolism and INSIGNEO Institute for In Silico Medicine, University of Sheffield, Sir Frederick Mappin Building, Pam Liversidge building, Sheffield S1 3JD, UK.
Enrico
E
Dall'Ara
School of Engineering, University of Portsmouth, Anglesea Building, Anglesea Road, Portsmouth PO1 3DJ, UK.
Marco
M
Curto
School of Engineering and Architecture, Alma Mater Studiorum - Università di Bologna, Via Terracini 28, Bologna 40131, Italy.
Federica
F
Innocente
School of Engineering and Architecture, Alma Mater Studiorum - Università di Bologna, Via Terracini 28, Bologna 40131, Italy.
Valentina
V
Danesi
School of Engineering, University of Portsmouth, Anglesea Building, Anglesea Road, Portsmouth PO1 3DJ, UK. Electronic address: gianluca.tozzi@port.ac.uk.
Gianluca
G
Tozzi
D000818:Animals; D001696:Biomechanical Phenomena; D004548:Elasticity; D009929:Organ Size; D034421:Sus scrofa; D013904:Thoracic Vertebrae / Q000000981:diagnostic imaging* / Q000502:physiology; D055114:X-Ray Microtomography
Augmented and natural vertebrae; Digital Volume Correlation (DVC); Micro-CT; Strain measurement uncertainties