Cortical Margining Capabilities of Fins used to detect differences in stiffness and yield strength between the three conditions. Pearson correlations were calculated to determine the relationships between BMD and stiffness, and between BMD and yield strength. All statistical tests were performed using Graphpad Prism 3.02 (Graphpad Software Inc., San Diego, CA). Signi- ficance was defined as p < 0.05. RESULTS Stiffness The mean stiffnesses (±standard deviation) are shown in Fig. 3. The condition C specimens (fins plus screws) had the greatest stiffness, at 459 ± 80 N/mm, while the condition A specimens (fins alone) were the least stiff, at 266 ± 53 N/mm. This represented a 42% decrease in stiffness, as com- pared to condition C. The condition B specimens (screws alone) were 11% less stiff than the con- dition C specimens (410±117 N/mm). One-way ANOVA with a Newman-Keuls analysis indicated that the condition A specimens were significantly less stiff than those subjected to conditions B and C (p < 0.05). No significant difference was ob- served between conditions B and C (p > 0.05). A Pearson correlation indicated that there was no statistically significant correlation between stiff- ness and BMD (p > 0.05). Yield loads The mean yield loads (±standard deviation) are shown in Fig. 4. Once again, the condition C specimens had superior performance, and had the greatest yield load, 526±168 N. The condition A specimens had the smallest yield loads, 180±54 N, which represented a 66% decrease compared to the condition C specimens. The condition B specimens had 40% smaller yield loads than the Fig. 3. Bar graph showing the stiffness values of the three instrumented condi- tions. Fig. 4. Bar graph showing the yield loads of the three instrumented conditions. Yonsei Med J Vol. 46, No. 3, 2005