[Interlaminar Distance and Bony Landmarks in Lumbar Neuraxial Anesthesia: A Concordance Study].

Background: Accurate identification of the puncture site in neuraxial anesthesia is essential. Accordingly, this study examines the concordance between interlaminar distance and bone landmark palpation in cases of difficult blockade. Objective: To reduce the risk of complications by enhancing the understanding of lumbar anatomy. Material and methods: A concordance study was conducted in 90 patients scheduled for neuraxial anesthesia, using bone landmark palpation and ultrasound measurement, with descriptive and inferential statistics applied through Cohen's Kappa coefficient. Results: The agreement between interlaminar distance and difficult blockade was κ = 0.565, p = 3.07×10⁻⁸; and between bone landmark palpation and difficult blockade was κ = 0.308, p = 0.00086. The odds ratio between difficult blockade and bone palpation was OR = 5.71 (95%CI: 1.93-16.93); for interlaminar distance and difficult blockade, the OR was 19.5 (95%CI: 5.85-65.00). The probability of encountering a difficult neuraxial blockade using the clinical technique was 80.77%, and with ultrasound guidance, it was 57.78%. Conclusions: An interlaminar distance <1.38 cm and grades 3 or 4 show moderate agreement with difficult blockade. Grades 3 or 4 were associated with a 5.71-fold increased likelihood of encountering a difficult blockade, whereas an interlaminar distance <1.38 cm was associated with a 19.5-fold increase. Based on probability difference, the use of ultrasound prior to neuraxial blockade reduces the likelihood of technical difficulty by 22.99% compared to the traditional clinical technique.