The midpedicular and interpedicular distance of thoracolumbar vertebrae.

OBJECTIVES

1. To introduce the measurement of the midpedicular distance (MPD) as an alternative to the interpedicular distance (IPD). 2. To measure the IPD and MPD of T11, T12, L1 and L2 vertebrae on anteroposterior (AP) plain film of the normal spine. 3. To study the relationship of the IPD and MPD of T11 to L2 of the normal spine.

STUDY DESIGN

Thoracolumbar AP plain film of 89 subjects (39 males, 50 females) with an average age of 47.6 years (range 21-78 years) from the roentgenographic files were included. Both the IPD and MPD of T11, T12, L1 and L2 were measured by two observers. The mean difference of IPD and MPD at these four levels were compared by using a one-way ANOVA. The relationship of the IPD and MPD measured from the T11 to L2 levels were evaluated using the simple linear regression model.

RESULTS

The mean IPD was progressively wider (p = 0.000) from the T11 to L1 level, but no significant difference (p = 0.308) was found between the mean IPDs of L1 and L2. The mean MPD of each level was significantly different from the others (p = 0.000) except the mean MPDs of T12 and L1 (p = 1.000). Both the IPD and MPD had a statistically significant linear relationship with the level of the vertebrae from T11 to L2 (p = 0.000) with the coefficients of determination (R2) of 0.39 and 0.28, respectively.

CONCLUSION

More care should be taken in clinical practice when measuring the IPD of a fractured vertebra relative to those of adjacent lower levels in order to determine whether or not widening has occurred, especially IPD L1 vis-à-vis IPD L2. MPD measurement has no advantage over the IPD measurement but is a useful alternative when a comparison of the pedicular distance of L1 and L2 is needed.