Locating l4-l5 Intervertebral Space and its Relation to Intercristal Line Using USG Among Indian Population, A prospective Observational Study

Background: Accurate identification of the L4–L5 intervertebral space is crucial for safe neuraxial anesthesia. The conventional palpation method using Tuffier’s (intercristal) line is widely practiced; however, anatomical variations may lead to incorrect level identification. Ultrasound (USG) offers a more reliable alternative for precise localization, particularly in populations with variable anthropometry.

Aim: To evaluate the accuracy of palpation-based identification of the L4–L5 intervertebral space using the Tuffier’s line and to assess its relationship with demographic and anthropometric factors using ultrasound guidance among the Indian population.

Methods: This prospective observational analytical study was conducted over 12 months at a tertiary care hospital in Mumbai. A total of 85 adult participants undergoing preanesthetic evaluation were enrolled. Demographic variables and anthropometric measurements including weight, height, BMI, sitting height, and hip circumference were recorded. The L4–L5 interspace was identified using both palpation (Tuffier’s line) and ultrasound guidance. The distance between the palpated Tuffier’s line and the ultrasound-confirmed L4–L5 interspace was measured. Statistical analysis included descriptive statistics, correlation analysis, and appropriate tests of significance.

Results: Accurate alignment of the palpated Tuffier’s line with the ultrasound-confirmed L4–L5 interspace was observed in only 3.5% of participants, while 96.5% showed misalignment. The mean distance between the Tuffier’s line and the L4–L5 interspace was 4.3 ± 1.7 cm, with a maximum displacement of 9 cm. The Tuffier’s line most commonly corresponded to the L3–L4 (42%) and L2–L3 (40%) interspaces. Significant correlations were observed between the distance of the L4–L5 interspace from the Tuffier’s line and weight, sitting height, and hip circumference, whereas age, sex, and BMI did not show significant associations.

Conclusion: Palpation-based identification of the L4–L5 intervertebral space using the Tuffier’s line is unreliable in the Indian adult population. Ultrasound guidance significantly improves accuracy and should be considered a valuable adjunct for neuraxial anesthesia, especially in patients with varying anthropometric profiles.