Biomechanical Comparison of Cadaveric and Commercially Available Synthetic Osteoporotic Bone Analogues in a Locked Plate Fracture Model Under Torsional Loading

Objectives: Biomechanical studies of osteoporotic bone have used synthetic models rather than cadaveric samples because of decreased variability, increased availability, and overall ease of the use of synthetic models. We compared the torsional mechanical properties of cadaveric osteoporotic bone with those of currently available synthetic osteoporotic bone analogues. Methods: We tested 12 osteoporotic cadaveric humeri and 6 specimens each of 6 types of synthetic analogues. A 5-mm fracture gap model and posterior plating technique with 4.5-mm narrow 10-hole locking compression plate were used. Torque was applied to a peak of +/- 10 N.m for 1000 cycles at 0.3 Hz. Data were continuously collected during cyclical and ramped loading with a servohydraulic materials testing system. Results: Cadaveric bone had a 17% failure rate before completing 1000 cycles. Three osteoporotic bone models had 100% failure (P < 0.05), 2 had 17% failure, and 1 had 0% failure before 1000 cycles. Significant differences in the stiffness of the 3 types of synthetic bone models that survived cyclic loading were noted compared with the cadaveric bone model (P < 0.05). Osteoporotic bone analogues had torsional mechanical properties different from those of osteoporotic cadaveric specimens. Conclusions: The differences between osteoporotic cadaveric humeri and synthetic osteoporotic bone analogues ranged from profound with complete catastrophic failure after a few cycles to subtler differences in stiffness and strain hardening. These findings suggest that different bone analogue models vary substantially in their torsional mechanical properties and might not be appropriate substitutes for cadaveric bone in biomechanical studies of osteoporotic bone.