Safety of Thermosensor Insertion in the Midline of the Spinal Canal Anterior to the Dura: A Cadaveric Study

Objective: To evaluate the safety of the insertion of a blunt-tip thermosensor inside the anterior epidural space using the trans-osseous route in the dorsal spine and the double oblique trans-foraminal approach in the lumbar spine. Materials and Methods: A total of 10 attempts were made on a 91 years old human specimen. Thermosensors were inserted under fluoroscopic guidance in the anterior part of the spinal canal using various oblique angulations. Surgical dissection was then performed to identify the position of the thermosensor and look for any injury to the dural sac or the spinal cord/cauda equina. Results: Nine thermosensors could be deployed successfully in the anterior part of the spinal canal from Th8 to L5 while one attempt (L5 level) failed due to a technical issue on the coaxial needle. On anteroposterior projection, the tip of thermosensor relative to the midline was classified as centered in 5 cases, overcrossing in 3 cases and undercrossing in 1 case. At surgical dissection, the tip of the thermosensor was epidural posterior to the posterior longitudinal ligament in 8 cases and anterior to the longitudinal ligament in 1 case (the undercrossing case). There were 3 tears to the dura, all in the overcrossing group. There was no case of injury to the spinal cord/cauda equina. Conclusion: Insertion of a thin blunt-tip thermosensor with optimal angulation leads to an epidural post-ligamentous position on the midline without damage to the dural sac. The blunt-tip did not prevent from dural tearing should the insertion overcross the midline.