The Geometry of the roots of the Brachial Plexus

Journal of Anatomy - Tập 237 Số 6 - Trang 999-1005 - 2020
Ryckie G. Wade1,2, Emily R Bligh3,4, Kieran Nar5, Rebecca S. Stone6, David J. Roberts3, Irvin Teh7, Gráinne Bourke1,2
1Department of Plastic and Reconstructive Surgery, Leeds Teaching Hospitals Trust, Leeds
2Leeds Institute for Medical Research, University of Leeds, Leeds, UK
3Division of Anatomy, Leeds Institute of Medical Education, University of Leeds, Leeds, UK
4Faculty of Medicine, Dentistry & Health, University of Sheffield Medical School, Sheffield, UK
5Faculty of Engineering, University of Sheffield, Sheffield, UK
6School of Computing, University of Leeds, Leeds, UK
7Leeds Institute of Cardiovascular and Metabolic Medicine, University of Leeds, Leeds, UK

Tóm tắt

AbstractDiffusion tensor magnetic resonance imaging (DTI) can be used to reconstruct the brachial plexus in 3D via tracts connecting contiguous diffusion tensors with similar primary eigenvector orientations. When creating DTI tractograms, the turning angle of connecting lines (step angle) must be prescribed by the user; however, the literature is lacking detailed geometry of brachial plexus to inform such decisions. Therefore, the spinal cord and brachial plexus of 10 embalmed adult cadavers were exposed bilaterally by posterior dissection. Photographs were taken under standardised conditions and spatially calibrated in MATLAB. The roots of the brachial plexus were traced from the dorsal root entry zone for 5 cm laterally using a 2.5‐mm2 Cartesian grid overlay. The trace was composed of points connected by lines, and the turning angle between line segments (the step angle) was resolved. Our data show that the geometry of the roots increased in tortuosity from C5 to T1, with no significant differences between sides. The 1st thoracic root had the most tortuous course, turning through a maximum angle of 56° per 2.5 mm (99% CI 44° to 70°). Significantly higher step angles and greater variability were observed in the medial 2 cm of the roots of the brachial plexus, where the dorsal and ventral rootlets coalesce to form the spinal root. Throughout the brachial plexus, the majority of step angles (>50%) were smaller than 20° and <1% of step angles exceeded 70°. The geometry of the brachial plexus increases in tortuosity from C5 to T1. To reconstruct 99% of tracts representing the roots of the brachial plexus by DTI tractography, users can either customise the step angle per root based on our findings or select a universal threshold of 70°.

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