Ar. Vaccaro et al., PLACEMENT OF PEDICLE SCREWS IN THE THORACIC SPINE .1. MORPHOMETRIC ANALYSIS OF THE THORACIC VERTEBRAE, Journal of bone and joint surgery. American volume, 77A(8), 1995, pp. 1193-1199
We studied the morphology of the thoracic vertebrae in the spines of s
eventeen human cadavera in order to define parameters that could be us
ed as guidelines for the placement of hooks and screws in the pedicles
to obtain internal fixation. We also reviewed computerized tomographi
c scans of nineteen thoracic spines in living patients who had no evid
ence of any vertebral deformity. The transverse diameter of the pedicl
e, which helps to determine the size of the screw, ranged from a mean
(and standard deviation) of 4.5 +/- 1.2 millimeters in the fourth thor
acic vertebra to a mean of 7.8 +/- 2.0 millimeters in the twelfth thor
acic vertebra. The pedicles were inclined anteromedially throughout th
e thoracic spine, and the angle ranged from 0.3 degree toward the midl
ine in the twelfth thoracic vertebra to 13.9 degrees in the fourth tho
racic vertebra. The morphometric data revealed wide variations in the
dimensions of the pedicles, demonstrating the importance of accurate p
reoperative imaging with transaxial computerized tomographic scans to
visualize the precise osseous margins and angles of insertion of the t
horacic pedicles.