Pedicle morphometry of the lumbar spine in a sample of the Mexican population, measured by computed tomography

Background:The greatest purchase of a screw in the lumbar spine occurs in the pedicle.This makes it important to have the largest diameter possible without damaging its walls.Objective: The aim of the study was to determine lumbar pedicle parameters in a population sample from Mexico City, to properly select the screw for use in lumbar spine surgery.Material and methods: Sixty patients, aged 20-70 years, were evaluated.Computed tomography (CT) scans measured the internal and external cortical pedicle height, internal and external cortical pedicle width, and the convergence angle in each lumbar pedicle.Descriptive statistics and the Mann-Whitney U test were used to determine the difference between means by sex and segment.Results: The mean age was 51.7 and 49.7 years in men and women, respectively.In women, the internal cortical pedicle width was smaller from L1 to L4, and the internal cortical pedicle height was smaller at L5.In men, the inner cortical pedicle width was narrower from L1 to L3, and the inner cortical pedicle height was narrower at L4 and L5.The angle of convergence was narrower at L1 and gradually increased up to L5 in both men and women.Conclusions: In women, 5.0 mm screws are safe for L4 and L5, and 4.0 mm screws are safe for L1-L3.In men, 5.0 mm screws are safe for L1 and L2, and 5.5 mm screws are safe for L3.At L4 and L5, 5.5 mm screws are safe.