Objective: A major element of developmental anatomical abnormalities associated with congenital lumbar spinal stenosis is congenitally shortened pedicles. We analyzed the role of congenitally shortened pedicles in LSS by quantitatively analyzing the antero-posterior midsagittal diameter of the spinal canal and the pedicle lengths on lumbar magnetic resonance imaging (MRI).
Methods: The lumbar MRI database of our hospital was retrospectively searched for terms’ lumbar spinal stenosis, spinal stenosis and stenosis’ in patients older than 18 years between January 2020 and January 2021. Midsagittal AP diameters of the lumbar spinal canal were measured at L2, L3, L4, and L5 levels on sagittal T2w images. Patients having at least one level of AP diameter equal to or less than 12 mm were considered as having LSS and included in the study group. After exclusions, 19 patients met the criteria and additional measurements were made for the pedicle lenght. They were compared with 76 control subjects.
Results: The rate of AP diameter being 12 mm or less at all levels was statistically significantly higher in the LSS group. The mean length of pedicles at the L2, L3, L4 and L5 levels in the LSS group was significantly shorter. The cut-off value for the pedicle length at the L2 level in the diagnosis of LSS was ≤8.7 mm. This was ≤9.7 for L3 level, ≤9.5 for L4 level and ≤10.1 for L5 level.
Conclusion: Decrease in pedicle length is proportionally associated with reduced diameter of the spinal canal resulting in CCS. Furthermore, the congenitally shortened pedicles give the canal a flattened appearance. The other-discriminating feature is that narrowing of the spinal canal is usually distributed throughout the lumbar spine. We found greater threshold values for shortened pedicles associated with decreased spinal canal AP diameter than found in other studies in the literature. In conclusion, the congenitally shortened pedicle plays an important role by increasing the likelihood of symptomatic presentations in LSS patients.