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

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.

To reduce the risk of complications by enhancing the understanding of lumbar anatomy.

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.

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%.

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.