Reliability of vernier caliper measurements of the thoracic pedicle transverse diameter

Abstract

The thoracic pedicle is generally cylindrical with various  indentations on its surface that may introduce an error in measurements, thus making the measurements unreliable. One hundred and eighty thoracic pedicle diameter measurements were carried out in five cadaveric human thoracic spine specimens, using a Vernier caliper. Coefficient of variation (CV) was used to evaluate the variation in measurements within and between  pedicles. Linear regression model was used to evaluate the  relationship between the variation in measurements and the average diameter of the bone per cadaver. The largest standard deviations in the five specimens were found at T2, T3, T6 and T12 levels. The least standard deviations were found at T1, T7, T9, T10 and T11. Four specimens demonstrated a negative linear relationship between the coefficient of variation and the average transverse diameter of the pedicle. This relationship was  significant (p<0.05) in two specimens. Vernier caliper measurements tend to be less reliable as the thoracic pedicle transverse diameter decreases. Caution is required when measuring the thoracic pedicle transverse diameter in the narrower mid-thoracic area of the spine with Vernier calipers.

Keywords: reliability, thoracic pedicle morphometry