Cortical Index
Definition
The ratio of total cortical bone area to total bone cross-sectional area at a defined midshaft location. Used in fragment identification to distinguish thick-walled long-bone shafts from thin-walled ribs and from avian or other non-human elements. Also used in osteoporosis assessment in clinical contexts.
- Definition
- Ratio of cortical bone area to total cross-sectional area
- Measured at
- Defined midshaft location
- Forensic use
- Distinguishes long-bone shafts from ribs and non-human elements
- Clinical use
- Osteoporosis assessment
Common questions
Why would fragment identification need a ratio rather than just measuring cortical thickness directly?+
A ratio normalises for the overall size of the fragment, so a thin-walled but large bone and a thick-walled but small bone can be distinguished consistently regardless of how much of the original shaft survives.
How does the cortical index help separate human from animal bone fragments?+
Different species and different skeletal elements have characteristic cortical-to-total-area proportions, so a fragment whose ratio falls well outside the human long-bone range points toward a non-human or non-long-bone origin.
Related terms
- Fragment Identification
- The assignment of a bone fragment to a specific skeletal element (rib, long-bone shaft, vertebral arch, cranial vault, etc.) and anatomical region,...
- Haversian Canal
- The central vascular channel of an osteon, carrying blood vessels and nerves through the cortical bone. Diameter 20-70 µm in human bone....
- Minimum Number of Individuals (MNI)
- The smallest number of distinct individuals required to account for all skeletal elements present in an assemblage. Determined by identifying the element...
- Neural Arch
- The posterior bony arch of a vertebra, formed by two pedicles and two laminae meeting at the spinous process. In foetal and...
- Osteon
- The basic structural unit of cortical bone: a set of concentric lamellae surrounding a central Haversian canal. Human secondary osteons are roughly...
- Owsley-Mann Protocol
- The fragment identification and triage methodology developed by Douglas Owsley (Smithsonian Institution) and Robert Mann (DPAA) for systematically assigning commingled bone fragments...
- Plexiform Bone
- A microstructural pattern found in the cortical bone of large rapid-growth mammals (bovids, horses, deer) characterised by alternating layers of woven bone...
- Side Determination
- The osteological process of assigning a paired skeletal element (clavicle, humerus, femur, rib, os coxae, etc.) to the left or right side...
- Species Confirmation (DNA)
- PCR-based or sequencing-based confirmation that a bone fragment is of human (Homo sapiens) origin, using human-specific primer sequences or mitochondrial cytochrome b...