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Comparison between a novel 2D-3D ultrasound system with pattern recognition and a conventional 2D ultrasound system for assessment of the lumbar spine: a cohort study in volunteers.
Abstract Number: F1B-5
Abstract Type: Original Research
Introduction: A wireless handheld ultrasound equipped with 3D pattern recognition software has recently been made available (Accuro, Rivana Medical, Charlottesville, VA). This device automatically identifies spinal bony landmarks and calculates the depth to the epidural space, and has shown promising results (1). We sought to assess the degree of agreement between the Accuro® and a conventional 2D ultrasound in assessing lumbar spine anatomy .
Methods: We performed a prospective cohort study in non-pregnant volunteers. The 5 anesthesiologists who performed the assessments were proficient in 2D spinal ultrasound and underwent a 4-hour hands-on workshop conducted by a sonographer trained to use the Accuro® before recruitment started. Each volunteer was assessed by 2 investigators who were randomized to perform the scanning with either the conventional 2D ultrasound (M-Turbo, FUJIFILM SonoSite,Inc., Markham, Canada) or the Accuro®. For each volunteer, the investigators were asked to identify the L3-L4 interspace and the optimal insertion point, and to estimate the depth to the epidural space. The assessment with the Accuro® was performed scanning from the sacrum, only in the transverse plane, and the optimal insertion point and estimated depth to the epidural space were determined based on the automated 3D screen display. The 2D ultrasound assessment was performed both in the longitudinal and transverse plane in the usual fashion and the distance to the ligamentum flavum-dura mater unit measured with the aid of a built-in caliper. Both investigators were blinded to each other’s markings, as they were made with an ink marker only visible to ultraviolet light. The primary outcome was the identification of the L3-L4 interspace. Secondary outcomes were the identification of the optimal insertion point and the estimated depth to the epidural space. The agreement between the two devices was assessed using the accuracy rate and intra-class correlation coefficient (ICC). The Bland-Altman method was also applied.
Results: We studied 48 volunteers. The agreement on the primary outcome (identification of L3-L4) using the Accuro® compared to 2D was only 46%. There was no specific bias (cephalad/caudad) in cases of non-agreement. In those cases where the interspace coincided, the median (IQ range) distance between the insertion points was 4.5 (3-9) mm. The estimated depth to the epidural space was always shorter when measured with the Accuro® (mean difference± SD 0.66±0.77 cm) and demonstrated poor agreement with the 2D estimate (ICC 0.1).
Discussion: There is poor agreement between the two methods in the determination of L3-L4. The clinical and safety implications of this lack of agreement at determining a given interspace may be significant. Further studies are needed to compare both methods against a gold standard such as MRI to further understand this lack of agreement.
References: 1)Anesth Analg. 2017 Aug 30. doi: 10.1213/ANE.0000000000002407