Background and Aims Transforaminal approach under ultrasounds (US) remains challenging. We evaluated on phantoms if fusions of computed tomography (CT) images with dynamic US examinations lead to precise location and puncture of the foramina between the fourth and fifth lumbar vertebra (L4-L5).

Methods Three anesthesiologists performed fusions of US and CT images with 3 different techniques on 2 models of phantom. Technique 1: fusion of the edge of the spinous process of L5 and the 2 posterior superior iliac spines. Technique 2: location of the 2 lateral extremities of the laminae instead of iliac spines. Technique 3: skin landmarks. Comparisons were performed with the value of precision (VP). 3 punctures targeting the right L4-L5 foramina were performed, needles positions were checked under X-ray. VPs were compared with ANOVAs, p<0.05 considered significant and results reported as means ± standard deviation.

Results One hundred and fifty fusions were recorded. Techniques 1 and 2 were performed on the gelatin phantom; technique 2 was superior to technique 1 (VP: 1.12 ± 0.54 vs 2.38 ± 1.49 for operator 1, 0.6 ± 0.39 vs 3.66 ± 1.22 for operator 2, 0.89 ± 0.31 vs 1.23 ± 0.63 for operator 3, p<0.001). There was no difference between the 3 techniques evaluated with the marketed phantom. X-ray examinations confirmed that punctures under fusion led the tip of the needle in the L4-L5 foramina.

Conclusions Bony and surface landmarks allow an accurate fusion of CT and US images of the lumbar spine and precise localizations and puncturing of lumbar neural foramina.