Validation of an In Vivo Model for Monitoring Trabecular Bone Quality Changes Using Micro CT, Archimedes-based Volume Fraction Measurement and Serial Milling

A combination of three techniques — high resolution computed tomography (micro CT) scanning, Archimedes-based volume fraction measurement and serial sectioning or milling — were used to determine the volume fraction as a measurement of trabecular bone quality changes in rabbit distal femur. The objective of this study was to develop the capabilities of micro CT scanning and micro CT image segmentation based on a slice-by-slice global thresholding technique to investigate trabecular microstructural changes in vivo and in vitro. These results were validated within the in vivo and invitro scans at the same time, and validated with the Archimedes-based volume fraction measurements and serial sectioning experiments. A total of six six-month-old New Zealand white rabbits were utilized in this study. The rabbits were scanned twice in vivo seven days a part and all of the left and right femurs (medial and lateral) were scanned in vitro. All micro CT images were obtained at 28 µm (in vivo) or 14 µm (in vitro) nominal resolutions. Specimens from six left and right rabbit distal femurs (medial and lateral) were also measured based on Archimedes’ principle and serial milling. These findings have shown that the in vivo and in vitro micro CT scanning are consistently repeatable while the accuracy of the serial milling to Archimedes-based volume fractions and the in vitro micro CT scanning to Archimedes-based were within ± 2.5% estimation respectively.