Skeletal Joe, Articulated Digital Model

Background: The purpose of this research was to develop an articulated digital model of the normal human spine. The model is proposed as a tool to assist a new method of serial monitoring the loaded spine. This monitoring method introduces a new 2D to 3D mapping technique using photography and digital modelling. Methods: Existing literature (1873-2007) measuring range of motion and coupling patterns for the entire spine, were reviewed. A meta-analysis of data was carried out and average flexion and extension ratios were calculated. The maximum inter-vertebral data for range of motion data was applied to a digital model. Inter-vertebral measurements were extrapolated from the model.Results: The maximum articulation for the entire spine for flexion (+) and extension (-) was +193.7° and -225.6° respectively, with 45.9%, 21.5% and 32.6% occurring in each of the cervical (C0-T1), thoracic (T1-T12) and lumber (T12-S1) regions. The percentages of flexion and extension were different in the cervical (+48.4% and -52.6%), thoracic (+69.0% and -31.0%) and lumbar spines (+28.2% and -71.8%). During lateral bending the maximum total rotation was 208° (each side), with 29.9%, 39.4% and 30.7% occurring in each of the spinal regions. During axial rotation the maximum total rotation was 255.7° (50% distributed to each side), with 38.5%, 38.7% and 22.8% occurring in each of the spinal regions.Articulation measurements, by different investigators varied due to different methods and apparatus being used. There were no ethno-geographic variations in articulation measurements reported in the literature. Variations existed due to age. The argument for gender variation was inclusive with the literature suggesting that physical length of the spine may be a more likely reason. The largest variations were because of the inherent individuality of human spines which over shadowed any of the other factors. Conclusion: There has been a significant body of research published on spine articulation, however understanding remains incomplete. There were similar results published for the range of motion observed in the cervical and lumbar spines, but disagreement or large variation reported regarding coupled motion. Little articulation research exists on the thoracic spine, the cervicothoracic junction and the thoracolumbar junction. No standardisation exists for coordinate systems used in digital human modelling and motion analysis. The Z-up system preferred for 3D virtual environments was used for the present research. To the best of our knowledge this digital model is the first to be informed by existing literature, quantifying both anatomy and articulation.