Measurement of Chinese lumbar pedicles: with special reference to transpedicular screw fixation

Abstract

Background: Thorough understanding of the morphometric parameters of the lumbar pedicles is essential for transpedicular screw fixation. The purpose of this study is to establish a database for proper spinal instrumentations in Chinese patients.

Methods: A total of 764 pedicles (L2-S1) were measured from spinal computed tomography (CT) of 100 Chinese volunteers. Parameters related to transpedicular fixation include pedicle width (PW), pedicle transverse angle (PTA), pedicle angle measured from the entry point of Roy-Camille through the midpoint of the pedicle (PPA), screw insertion depths to the anterior cortex from the entry point of Roy-Camille along the line parallel to the midsagittal line (PPLP) and from the entry point of Magerl along the pedicle axis (PPLS).

Results: The mean age of the volunteers was 46.2 years. The average PWs from L2 to S1 were: 0.85 +/- 0.15 cm for L2, 0.92 +/- 0.22 cm for L3, 1.19 +/- 0.24 cm for L4, 1.70 +/- 0.28 cm for L5 and 2.31 +/- 0.35 cm for S1. The average PTAs from L2 to S1 were: 13.9 degrees +/- 4.9 degrees for L2, 13.4 degrees +/- 5.1 degrees for L3, 16.2 degrees +/- 5.9 degrees for L4, 27.8 degrees +/- 7.2 degrees for L5 and 44.0 degrees +/- 8.4 degrees for S1. The average PPAs from L2 to S1 were: 5.3 degrees +/- 2.4 degrees for L2, 6.3 degrees +/- 2.2 degrees for L3, 7.2 degrees +/- 2.5 degrees for L4, 10.1 degrees +/- 3.6 degrees for L5 and 17.0 degrees +/- 4.8 degrees for S1. The average PPLPs from L2 to S1 were: 5.64 +/- 0.82 cm for L2, 5.05 +/- 0.62 cm for L3, 4.99 +/- 0.89 cm for L4, 4.42 +/- 0.77 cm for L5 and 4.23 +/- 0.72 cm for S1. The average PPLSs from L2 to S1 were: 5.75 +/- 0.72 cm for L2, 5.24 +/- 0.75 cm for L3, 5.27 +/- 0.84 cm for L4, 4.88 +/- 0.72 cm for L5 and 4.99 +/- 0.72 cm for S1.

Conclusions: Transpedicular screw fixation should be tailored on individual basis. Though variation exists, no sufficient evidence can be found to suggest major morphometric differences of the Chinese lumbar pedicles from the studies in the English literature.