A Comprehensive Study of Physical Parameters, Biomechanical Properties, and Statistical Correlations of Iliac Crest Bone Wedges Used in Spinal Fusion Surgery

Iliac crest wedges are commonly used in spinal fusion procedures and must be capable of withstanding considerable mechanical stress during the healing process. Physical parameters, mechanical properties, correlations among physical parameters, and correlations of mechanical properties versus physical parameters have been presented by the authors in companion papers. In this study, mathematical formulas have been developed, using multi-variable regression analysis, which permit calculation of the axial load-bearing capacity and compressive strength of a wedge, provided donor age, cortical bone cross-sectional area, total cross-sectional area, and wedge "width" are available. The formulas proposed are simple, easy to use, and provide acceptable accuracy. For the predicted load-bearing capacity, experimentally determined data illustrated that 59% of the calculated values had either less than 10% error or their predicted values were smaller than the observed values, 75% of the calculated values had either less than 20% error or their predicted values were smaller than the observed values. Similar accuracies were estimated for calculation of compressive strengths. Charts are generated from the established formulas, which permit a visual determination of load-bearing capacity and compressive strength of a wedge.