Object: The purpose of this study is to determine the value of intraoperative clinical distinction between lumbar vertebrae, according to physical characteristics (of the fourth and fifth lumbar vertebrae) and the applicability of this physical distinction during lumbar spine surgery.
Materials and Methods: This descriptive study covers 30 random cadaver autopsies to evaluate physical characteristics of the fourth and fifth vertebral laminae and 200 patients undergoing a lumbar spine procedure to test the applicability of physical differentiation over a 2-year period from September 2004 to September 2006. Physical characteristics of laminae of the fourth and fifth lumbar vertebrae, including height, length, and thickness, were measured by microscopic scales. For each patient, an intraoperative x-ray image was also taken. All the data were analyzed using Statistical Package for Social Sciences Release 11.5 software and 2 independent tests and t test were applied as the statistical tests to ensure the results.
Conclusions: The results of this study confirmed that the mean thickness of inferior border of L5 lamina is less than L4 lamina (P<0.001) and it is possible for the surgeon to differentiate these 2 vertebrae intraoperatively. Also, a statistically significant difference was found between the mean height of L4 and L5 laminae (P<0.000) indicating that the height of L4 lamina is higher than L5 lamina. It was also concluded that the mean length of L5 lamina is more than L4 lamina and the difference was statistically significant. The positive predictive value of anatomic differentiation between L4 and L5 vertebrae is 93%.