Structural properties of a novel design of composite analogue humeri models.

Background: Mechanical analogue composite bone models have been used as cadaveric bone substitutes in a wide variety of biomechanical tests. The objective of this study was to compare the structural properties of two types (Third- and Fourth-Generation) of commercially available composite analogue humeri.

Methods: Eighteen of each generation composite analogue humeri were evaluated for flexural rigidity, torsional rigidity, and failure strength. Three tests were performed: medial-lateral four-point bending, anterior-posterior four-point bending, and external rotational torque.

Results: The Fourth-Generation analogue humeri performed more closely to the biological average with respect to failure strength, flexural rigidity, and torsional stiffness when compared to the Third-Generation humeri. Both the Third- and Fourth-Generation analogues were within the range of published human bone values. There was a statistically significant difference in strength in all modes of testing between the Fourth-Generation humeri and the Third-Generation humeri.

Conclusion: These composite analogue humeri are ideal for standardization in biomechanical analyses. The advantage of these humeri is that their variability is significantly lower than that of cadaveric specimens for all loading regimens. The widely varying results observed when comparing composite analogue humeri to cadaveric humeri might be derived from the use of different ranges of applied load, varied test methodologies, and diverse methods of computing the stiffness. Mechanical validation of whole Fourth-Generation humeri bone models would be an appropriate follow-up to this study with a direct comparison to cadaveric humeri.

Clinical Relevance: This study validated and advanced our overall understanding of the capacity of composite analogue humeri to model the structural properties of human bone.