Abdominal circumference but not the degree of lumbar flexion affects the accuracy of lumbar interspace identification by Tuffier's line palpation method: An observational study

Background: Lumbar puncture for spinal or epidural anesthesia is commonly performed by palpating bony landmarks, but identification of the desired intervertebral level is often inaccurate. It is unclear whether such inaccuracy is related to patient factors, such as body mass index and degree of lumbar flexion. We hypothesized that overweight patients and patients with less of an ability to hyperflex their lumbar spines are prone to inaccurate lumbar spinous intervertebral level identification. Methods: 52 adult volunteers were included in this study. 7 anesthesiologists with different years of experience identified and marked subjects' levels of the iliac crests, then marked the presumed interspaces. Lumbar X-ray was then performed with metal markers, and actual radiographic findings were identified and compared to the initial markings. Results: Patients with larger abdominal circumferences (mean (SD), 94.0(12.1) cm), higher body mass indices (25.9(3.9) kg/m), and aged between 50 and 70 years old had lumbar interspaces that were higher than the presumed level; patients with smaller abdominal circumferences (82.8(13.5) cm) and lower body mass indices (21.6(4.1) kg/m) had intervertebral levels that were lower than the presumed level. Cobb's angle, indicating the degree of lumbar flexion, did not affect the accuracy obtained. Conclusions: Patients' abdominal circumference, body mass index, and age are factors that may impact the accuracy of lumbar level identification. Tuffier's line, as identified by palpation, does not seem to be a reliable landmark for proper lumbar interspace identification in all cases.