Cortical Bone Density Determination with Microct Is Highly Reliable

Objective: Bone density is moderately correlated with elastic moduli and yield strength and is a partial determinant of bone quality. It can be used as an indicator of bone remodeling, tissue age, and functional adaptation. It must be determined for estimates of 3D elastic properties for finite element modeling, a numerical technique for understanding the functional behavior of skeletal organs. The bone density measurement standard uses Archimedes Principle and densitometry apparatus based on accurate scale measurements. This requires preparation of small samples and does not allow continuous cortical sampling. MicroCT is a 3D radiographic technique which is used to examine hard tissue structure and with adequate calibration, might be used for determining continuous variations in bone density. This study compares densities measured by these techniques.

Method: 40 cylindrical bone specimens from the primate facial skeletons were used and bone densities were measured using standard techniques. Cortical specimens were then scanned with a Scanco MicroCT 35 at a resolution of 3.5 microns. Apparent and material densities were estimated using Scanco’s calibrations.

Result: Results showed variation in cortical apparent density varying between 1400 and 2000 mg/ccm. MicroCT estimates of apparent density were lower ranging from 700 to 1000 mg/ccm yet were highly correlated with values measured by standard technique at R=0.95. Material density was correlated at a significant but lower level (R=0.75). Both standard and microCT techniques show high reliability.

Conclusion: These findings suggest that microCT can be used to assess continuous variations in apparent bone density and might be useful for gathering material property data for use in finite element studies.

(Supported by the National Science Foundation Physical Anthropology HOMINID program (NSF BCS 0725141 to PD) and the Baylor Oral Health Foundation).