Regional differences in trabecular BMD and micro-architecture of weight-bearing bone under habitual gait loading--a...

This study used both multi-slice pQCT and microCT to investigate regional changes in bone mineral density and structural parameters in the ultradistal tibia and in the mid-femoral neck under habitual gait loading. Twenty cadavers with 2 females and 18 males aged 70.8 +/- 8.5 were used in this study. Seventy-two cylindrical bone cores with 5 mm in diameter and 10 mm in length from the anterior/posterior and superior/inferior regions were obtained from ultradistal tibia and mid-femur neck, respectively, so that their differences in terms of volumetric trabecular bone mineral density (tBMD) as well as micro-architectural parameters could be studied. The results showed that the mean volumetric tBMD at both the organ (including the bone marrow spaces) and tissue levels (excluding the bone marrow spaces) were a 49.2% and 28.3%, respectively, lower in the anterior bone cores than in the posterior bone cores from the ultradistal tibia (P < 0.01). MicroCT measurements on BV/TV, BS/TV, Tb.N, Tb.Th, and DA were found to be on average of 33.5%, 23.6%, 9.1%, 18.0%, and 14.6%, respectively, lower in the anterior trabecular bone cores (P < 0.001), while Tb.Sp and SMI were 12.5% and 29.3%, respectively, higher in the anterior trabecular bone cores (P < 0.01). No significant difference in micro-architectural parameters was found in the trabecular bone cores obtained from mid-femoral neck, except that the mean DA of the inferior bone cores was significantly higher by 30.1% than that of the superior bone cores (P = 0.01). A statistically significant linear relationship with the correlation coefficient, ranging from 0.37 to 0.94 and -0.62 to -0.85, respectively, was shown between the tBMD at the organ level and all of the micro-architectural parameters (P < 0.05). We suggest that dynamic loading changes during the striking of the heel in normal gait, as well as the peaks of the hip joint reaction force occur during the heel strike and before toe off positions in the lifetime of the subject may account for such regional differences in BMD and micro-architecture. The findings from the correlation study also suggest that, apart from BMD, the micro-architecture may exhibit adaptation in response to such excessive loading.