The concordance rate of L3/4 intervertebral lumbar level estimated by palpation and ultrasonography in Japanese parturients.

BACKGROUND: The accurate identification of an intervertebral lumbar level is essential to avoid neuraxial anesthesia and analgesia-related spinal cord injury. It has been shown that estimation of L3/4 intervertebral lumbar level based on the intercristal line determined by palpation (palpated L3/4) is often inaccurate. However; studies evaluating intervertebral lumbar level concordance based on palpation vs. ultrasonography were conducted in Western populations (i.e. in North America and/or Europe). Radiological studies suggest that the intercristal line intersects at a lower level of the spine in Japanese women than in Western women. Therefore, we hypothesized that differences exist in intervertebral levels based on the palpated intercristal line between Asian and Western women. Herein we present the results of the first study in Japan comparing the concordance rate of L3/4 intervertebral lumbar level estimated by palpation and ultrasonography in pregnant Japanese women.

STUDY OBJECTIVE: The objective of this study was to evaluate the accuracy of palpated L3/4 in Japanese parturients assessed by ultrasonography (US).

DESIGN: A prospective, observer-blinded study.

SETTING: Labor and delivery room at the Kitasato University Hospital, Sagamihara, Kanagawa, Japan.

PATIENTS: Sixty-three term parturients underwent induction of labor and requested neuraxial labor analgesia.

INTERVENTIONS: With the patients in the sitting position, an attending anesthesiologist marked the intervertebral space estimated as L3/4 based on intercristal line with palpation. Another attending anesthesiologist who was blinded to the marker performed US to identify L3/4.

RESULTS: The overall agreement rate of palpated and US L3/4 was 69.8% (44/63). Palpated L3/4 was US L2/3 in 8/63 (12.7%) and US L4/5 in 11/63 (17.5%). In comparison with women with palpated L3/4 agreed with US L3/4, women with palpated L3/4 agreed with US L2/3 were more frequently multiparous (52 vs. 100%, p < .05) and women with palpated L3/4 identified as L4/5 were younger (36 ± 4 years vs. 33 ± 4 yrs, p < .05) and gained less weight during pregnancy (10 ± 4 kg vs. 7 ± 4 kg, p < .05). The patients whose palpated L3/4 were found to be US L2/3 were all multiparous.

CONCLUSION: The accuracy rate of palpated L3/4 intervertebral lumbar level in pregnant women included in our study was 69.8%. Pregnancy-related weight gain, parity, and maternal age can all influence an estimation of L3/4 intervertebral lumbar level by palpation. In addition, we believe that this is the first study to analyze the correlation between maternal parity and interspace estimation by palpation in pregnant women.