Thurs., 10/13/11 Basic Science, Paper #38, 4:53 pm OTA-2011
Are Commercially Available Synthetic Osteoporotic Bone Models Valid?
Edward H. Becker, MD1; Hyunchul Kim, MS2; Michael J. Shorofsky, BS1;
Adam H. Hsieh, PhD2; Robert V. O’Toole, MD1;
1R Adams Cowley Shock Trauma Center, Baltimore, Maryland, USA;
2Department of Orthopaedics, University of Maryland School of Medicine,
College Park, Maryland, USA
Purpose: Many biomechanical studies focusing on osteoporotic bone have opted to use commercially available synthetic models rather than cadaveric samples due to their decreased variability, increased availability, and overall ease of use. To the best of our knowledge, the companies’ claims that these models reasonably approximate osteoporotic bone for use in fracture fixation studies has not been tested. Our hypothesis was that these models would mimic actual osteoporotic cadaveric bone properties.
Methods: We compared the performance of 6 commercially available synthetic bone analogs (n = 6 each) to 12 osteoporotic cadaveric humeri (DEXA [dual-energy x-ray absorptiometry]– validated). We utilized a previously described 5-mm fracture gap model and posterior plating technique using a 4.5-mm narrow 10-hole locking compression plate. Torque was applied to a peak of ±10 Nm for 1000 cycles at 0.3 Hz using a servohydraulic biaxial testing machine.
Results: Unlike actual osteoporotic bone, 3 groups of synthetic bone analogs did not survive sufficient numbers of cycles during the loading procedure to even be analyzed. The remaining 3 types of osteoporotic bone analogs were found to have more subtle differences in biomechanical properties from osteoporotic cadaveric specimens. For example, relative to initial stiffness (cycle 1), cadaveric humeri exhibited a slight decrease in stiffness that became statistically significant at cycle 7 (P <0.05). In contrast, by approximately cycles 30 through 70, all synthetic humeri had statistically significant increases in torsional stiffness (strain hardening) relative to initial stiffness (P <0.05).
Conclusions: We found differences between osteoporotic bone analogs and actual osteoporotic cadaveric bone that ranged from profound (complete failure at initial failure) to more subtle differences (strain hardening that is not present in actual bone). These findings may invalidate conclusions from prior work depending on the bone analog that was used in the fracture model. Future work should strive to validate bone analogs before using them to draw clinical conclusions.
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• The FDA has not cleared this drug and/or medical device for the use described in this presentation (i.e., the drug or medical device is being discussed for an “off label” use). ◆FDA information not available at time of printing. Δ OTA Grant.