USE OF MICROCOMPUTED TOMOGRAPHY SCANNING AS A NEW TECHNIQUE FOR THE EVALUATION OF MEMBRANOUS BONE

Previous basic bone studies in cranial bone biology and bone grafting have used calipers, volume displacement, and cephalometric tracings to measure membranous bone and to infer fundamental properties of crania l bone. These tools have limited accuracy and reproducibility. Histomo rphometry has also been used in the quantitative analysis of cranial b one; however, two-dimensional histology is unable to capture a precise representation of the three-dimensional structure of bone. For the fi rst time, we have used the advanced technology of three-dimensional mi crocomputed tomographic (micro-CT) scanning as a highly accurate acid automated tool to precisely measure changes in bone stereology, volume and projection, and microarchitecture in the evaluation of membranous bone. The advantages of this technology are numerous and include the rapid and nondestructive three-dimensional analysis of bane microstruc ture al resolutions between 10 and 75 mu m, Measures of ''connectivity '' in three dimensions and the architectural parameter of ''anisotropy '' are available through micro-CT imaging but can only be inferred thr ough two-dimensional histological series. We successfully imaged two f ull-thickness cranial bone specimens and one cancellous iliac bone gra ft. The images demonstrate a similarity between the two membranous spe cimens and a marked difference in comparison with the endochondral gra ft. These differences are borne out by mathematical analysis, and thei r significance is discussed. The utility of micro-CT in the evaluation of membranous bone was displayed by its ability to rapidly calculate differences in bone stereology and to quantitatively measure morpholog ical changes at an ultrastructural level. We believe the benefits of t his system Will prove to be extremely useful for investigations into t he basic biology of membranes bone, bone grafts, and craniofacial inte rfaces, and we encourage its use by other scientific investigators in the field of craniofacial surgery as they strive for more scientifical ly rigorous tools to understand the basic biology of membranous bone.