BACKGROUNDSacral nerve injury is a common complication of pelvic or sacral fractures. As the sacral nerve courser within the sacrum and has a complex relationship with the surrounding tissues, different parts of the sacral plexus injury have similar clinical symptoms and signs. Since lack of specific imaging technique in the diagnosis of sacral nerve injury, especially on multi-segment, multi-site, how to determine the preoperative location and extent of the sacral nerve injury accurately becomes a concern of the general orthopaedic and images practitioners. This study was conducted to gain an insight into the overall anatomical features of the sacral nerve (SN) on the same slice in high resolution computed tomography (HRCT) reconstruction and to determine the value of this information for the clinical diagnosis of related diseases.

METHODSFifty healthy volunteers and 30 patients (40 sides) with SN lesions confirmed by surgery were scanned using a 16-slice helical CT scanner (Light Speed, GE, USA). Among the patients, 6 with intervertebral disk hernia (6 sides), 8 with spinal stenosis (12 sides), 11 with pelvic trauma (14 sides), 4 with pelvic malignancies (6 sides), and 1 with sacral vertebral tuberculosis (2 sides). The SN multiplanar reconstruction was performed using a UNIX-based SCD4.1 workstation where the image was set on the same slice. All images were stored in the Digital Imaging and Communications in Medicine format. The display of nerves in different sections was analyzed using a five-graded scale with coordinate curves of each individual score. The overall anatomic features visible on the slice were analyzed and the abnormalities of the lesions were studied.

RESULTSThe image of the same slice clearly revealed the shape, running direction, thickness, tension and adjacent anatomy of the S1-S4 nerves. The rank of display rates in different sections was: outward-rotated oblique sagittal > outward-rotated oblique coronal > oblique coronal plane > coronal > sagittal > transverse section. The S5 nerve was partially displayed from the starting point to the segment around the posterior sacral foramen. The overall anatomy of the triangular sacral plexus was only revealed in the oblique outward-rotated sagittal section, while 100% of its individual rami, as well as two or three of the adjacent rami, were displayed from their starting points to the anterior border of the piriformis. The abnormalities included 39 sides of morphological change (97.5%), 38 sides of compression (95.0%), 35 sides of adhesion (87.5%), 32 sides of displacement (80.0%), 34 sides of shrinkage (85.0%), 6 sides of thickening (15.0%), and 2 sides of abruption (5.0%).

CONCLUSIONSThe 16-slice CT multiplanar reconstruction was able to reveal the overall anatomic features of the SN on the same slice. The section of reconstruction was a crucial factor in determining the display capability of various sacral nerves. This technology was valuable in the diagnosis and management of related diseases.