In Vivo Evaluation of the Presence of Bone Marrow in Cortical Porosity in Postmenopausal Osteopenic Women

This is the first observational study examining cortical porosity in vivo in postmenopausal osteopenic women and to incorporate data from two different imaging modalities to further examine the nature of cortical porosity. The goal of this study was to combine high-resolution peripheral computed tomography (HR-pQCT) images, which contain high spatial resolution information of the cortical structure, and magnetic resonance (MR) images, which allow the visualization of soft tissues such as bone marrow, to observe the amount of cortical porosity that contains bone marrow in postmenopausal osteopenic women. The radius of 49 and the tibia of 51 postmenopausal osteopenic women (age 56 ± 3.7) were scanned using both HR-pQCT and MR imaging. A normalized mutual information registration algorithm was used to obtain a three-dimensional rigid transform which aligned the MR image to the HR-pQCT image. The aligned images allowed for the visualization of bone marrow in cortical pores. From the HR-pQCT image, the percent cortical porosity, the number of cortical pores, and the size of each cortical pore was determined. By overlaying the aligned MR and HR-pQCT images, the percent of cortical pores containing marrow, the number of cortical pores containing marrow, and the size of each cortical pore containing marrow were measured. While the amount of cortical porosity did not vary greatly between subjects, the type of cortical pore, containing marrow vs. not containing marrow, varied highly between subjects. The results suggest that cortical pore spaces contain components of varying composition, and that there may be more than one mechanism for the development of cortical porosity

Super-osteons (remodeling clusters) in the cortex of the femoral shaft: influence of age and gender.

Previous studies of cortical remodeling in the fractured femoral neck indicated that the merging of spatially clustered remodeling osteons could result in the formation of deleteriously large cavities associated with femoral neck fracture. This study aimed to identify whether remodeling osteons in the femoral shaft were also clustered and to assess the influence of age and gender. Microradiographic images of femoral mid-shaft cross-sections from 66 subjects over 21 years of age were analyzed to determine the number, size and location of all Haversian canals. Those most recently remodeled were identified using an edge-detection algorithm highlighting the most marked differential gradients in grey levels. Cluster analysis (JMP software) of these osteons identified the proportion of recently remodeled osteons that were within 0.75 mm clusters. As in the femoral neck, remodeling osteons were significantly more clustered than could occur by chance (real, 59.4%; random, 39.4%; P 385 microm) was inversely related to the presence of clusters (R(2) = 0.237, P < 0.0001). This data suggest that remodeling osteons tend to be spatially colocalized in the shaft as they are in the neck of the femur and their presence is independent of age or gender. We propose that these remodeling clusters be termed super-osteons. The negative relationship between super-osteons and giant canals raises the intriguing possibility that loss of the control of remodeling depth results in the merging of osteonal systems to form deleteriously large cortical cavities with a marked reduction in bone strength

Super-osteons (remodeling clusters) in the cortex of the femoral shaft: influence of age and gender.

Previous studies of cortical remodeling in the fractured femoral neck indicated that the merging of spatially clustered remodeling osteons could result in the formation of deleteriously large cavities associated with femoral neck fracture. This study aimed to identify whether remodeling osteons in the femoral shaft were also clustered and to assess the influence of age and gender. Microradiographic images of femoral mid-shaft cross-sections from 66 subjects over 21 years of age were analyzed to determine the number, size and location of all Haversian canals. Those most recently remodeled were identified using an edge-detection algorithm highlighting the most marked differential gradients in grey levels. Cluster analysis (JMP software) of these osteons identified the proportion of recently remodeled osteons that were within 0.75 mm clusters. As in the femoral neck, remodeling osteons were significantly more clustered than could occur by chance (real, 59.4%; random, 39.4%; P &lt; 0.0001). The density of these clusters (number/mm(2)) was not significantly associated with subject age or gender but was greatest near the periosteum and decreased toward the marrow cavity (periosteal 0.043 +/- 0.004; mid-cortex 0.028 +/- 0.003; endosteal 0.017 +/- 0.002). Cortical porosity increased with age. The presence of giant canals (diameter &gt;385 microm) was inversely related to the presence of clusters (R(2) = 0.237, P &lt; 0.0001). This data suggest that remodeling osteons tend to be spatially colocalized in the shaft as they are in the neck of the femur and their presence is independent of age or gender. We propose that these remodeling clusters be termed super-osteons. The negative relationship between super-osteons and giant canals raises the intriguing possibility that loss of the control of remodeling depth results in the merging of osteonal systems to form deleteriously large cortical cavities with a marked reduction in bone strength