While metal or plastic interbody spinal fusion devices are manufactured to appropriate mechanical standards, mechanical properties of commercially prepared structural allograft bone remain relatively unassessed. Robust models predicting compressive load to failure of structural allograft bone based on easily measured variables would be useful. Three hundred twenty seven femoral rings from 34 cadaver femora were tested to failure in axial compression. Predictive variables included age, gender, bone mineral density (BMD), position along femoral shaft, maximum/minimum wall thickness, outer/inner diameter, and area. We used support vector regression and 10-fold cross-validation to develop robust nonlinear predictive models for load to failure. Model performance was measured by the root-mean-squared-deviation (RMSD) and correlation coefficients (r). A polynomial model using all variables had RMSD ¼ 7.92, r ¼ 0.84, indicating excellent performance. A model using all variables except BMD was essentially unchanged (RMSD ¼ 8.12, r ¼ 0.83). Eliminating both age and BMD produced a model with RMSD ¼ 8.41, r ¼ 0.82, again essentially unchanged. Compressive strength of structural allograft bone can be estimated using easily measured geometric parameters, without including BMD or age. As DEXA is costly and cumbersome, and setting upper age-limits for potential donors reduces the supply, our results may prove helpful to increase the quality and availability of structural allograft. Keywords: structural bone allograft; spinal fusion; biomechanics; bone mineral densityThe allograft bone industry is guided by practices intended to optimize safety and effectiveness of allograft bone in numerous clinical applications. Guidelines have been developed and used with respect to avoidance of transmission of neoplastic and infectious disease based on high level scientific data. 1,2 Adherence to these guidelines has resulted in safe and successful allograft implantation over many years of experience. 3 Despite this excellent track record, the mechanical properties of what is essentially a mechanical device 4 remain comparatively un-assessed. In fact, there are no guidelines prescribed with respect to material properties of structural allograft bone products within the Food and Drug Administration or the American Association of Tissue Banks. 2,5 A recent survey of allograft providers demonstrated that given this lack of guidelines, a variety of practices are employed with regard to screening of donors and allografts. 6 On the other hand, interbody spacers manufactured using materials such as carbon fiber, titanium, or polyetheretherketone are expected to have consistent biomechanical properties. 7-9 While the cited advantages of allograft bone over such implants include lower cost and equal or better clinical performance, 10-21 the mechanical performance of structural allograft bone intended for use as an interbody device should be similarly uniform and reliable.We have accumulated a database of load to failure measurements for fem...