Study design: A morphometric study of lumbar vertebral pedicular parameters in cadavers and comparison with previous studies in the literature was conducted.
Objectives: To suggest dimensions for pedicular implants in the Indian population, and to improve the pedicular screw placement technique.
Summary of background data: Detailed knowledge of pedicle morphometry is critical for proper placement of a transpedicular screw. The size and shape of the vertebral pedicle vary between different races. Morphometric studies have been conducted in white and nonwhite populations (e.g., Chinese, Koreans).
Methods: The vertebral pedicles at L1-L5 were studied in 20 cadavers by direct roentgenographic and computerized tomographic scan methods. The following parameters were studied: transverse diameter, transverse angle, sagittal diameter, sagittal angle, chord length, interpedicular distance, medial and lateral cortical thickness.
Results: Transverse diameter was largest at L5 (16.19 mm) and smallest at L1 (7.05 mm). The transverse angle was largest at L5 (29 degrees) and smallest at L1 (9 degrees). The pedicles were directed cranially in the sagittal plane at all lumber levels except L5. The sagittal angle was largest at L5 (29 degrees) and smallest at L1 (9 degrees). Chord length was largest at L2 (47.5 mm) and smallest at L1 (46.01 mm). The values of linear measurements were smaller in females at all levels.
Conclusions: On the basis of this limited study in a subset of the Indian population, it appears that the transverse diameter and pedicle entrance point differ from those in the white population. The results suggest that a 5-mm screw would be safer in the upper lumbar levels (L1, L2), and 6-mm screw in the lower lumbar levels (L3-L5). The pedicle entrance point migrates laterally for lower lumbar levels, especially at L5. The medial pedicle cortex can be safely sounded while the pedicle is probed.