Pedicle morphology of the lower thoracic and lumbar spine in a Chinese population.

Knowledge of padicile diameter and surface landmarks is crucial for safe placement of screws. Little attentionhas been paid to varilation of entrance points for pedicle screws, differentiation of male and female pedicle sized and pedicle size differences in nonwhite populations. Forthy thoracolumbar spinal columns from T9 to L5 were measured using vernier callpers. Cephalad-cauded and media-lateral diameter of the pedicie, length of the pedicle from posterior cortex to anterior cortex at the midline and parallel to midine was measured. Relation of the centre of teh pedicle to the trnasverse process (TP) and to the superior facet joint was noted. Twenty-five male and 15 female specimens were measured. Average pedicle width in the female was 5.2 mm at T9 (SD 0.9) to 13 mm at L5 (SD 2.7) and in the male 8.0 mm at T9 (SD 1.1) to 12.8 mm at L5 (SD 2.7). Cephalad caudad diameter was 12.5 mm (SD 1.2) at T9 to 20.5 mm (SD 3.6) at L5 in the male in in the female 12.2 mm (SD 1.3) at T9 to 18.7 mm (SD3.69) at L5, All specimens had starting points cephalad to the midpoint ot the TP at T9. At L5, 37 of 40 specimens had starting points at the midpoint of the TP, Starting pointswere parallel to the middle or lateral third of the superior facel joing at T9. At L5 starting points were at least one third of the facet joint lateral to the lateral border of the facet. Female pedicle width was smaller than male at T9 (P = 0.03) and T12 (P = 0.04). All pedicle widths except T11 are significantly smaller than the white population as measured by Zindrick et al. Male pedicle widths are significanltly smaller than whites as measured by Olsewski et al. Only L5 is smaller than the white population as measured by Berry et al. Starting points should be more lateral in the low lumbar spine. Pedicle screw insertion dependes on teh sex and sixe of teh patient, and the location of teh vertabrae.