We conducted this study to develop an ultrasound-guided approach for facet joint injections of the lumbar spine. Five zygapophyseal joints (L1-S1) on each side of 5 embalmed cadavers were examined by ultrasound for a total of 50 examinations. The joint space was demonstrated under ultrasound guidance. The midpoint of the joint space, defined as the middle of its cranio-caudal extension on its dorsal surface, was taken as a reference point, and its position was computed from its depth and lateral distance from the spinous process. Forty-two of 50 approaches could be clearly visualized. Subsequently, these distances were compared to those obtained by computed tomography (CT). To assess the efficacy of ultrasound in the needle placement, all lumbar facet joints were approached in one embalmed cadaver. The exact placement of the needle tips was again evaluated by CT. Ultrasound and CT measurements showed the same mean depth and lateral distance to the reference point, 3.15 +/- 0.5 cm and 1.9 +/- 0.6 cm, respectively. Pearson's coefficient of correlation was 0.86 (P < 0.0001) between ultrasound and CT. All 10 needle tips were within the joint space during simulated facet joint injections. We conclude that ultrasound guidance might be a useful adjunct for facet joint injections in the lumbar spine.
Implications: This study was designed to develop an ultrasound-guided approach to the facet joints of the lumbar spine and to assess its feasibility and accuracy by means of a comparison to computed tomography images. The imaging study demonstrated a significant correlation between ultrasound and computed tomography measurements. During simulated facet injection, ultrasound guidance consistently resulted in accurate needle placement.