[Intra-operative myelography in treatment of fractures of thoracolumbar spine].

Purpose Of The Study: The aim of this retrospective study was to evaluate the results of intra-operative myelography as the method used to assess the reduction of bone fragments from the posterior margin of the vertebral body.

Material And Methods: Forty patients with 42 comminuted fractures of the thoracolumbar spine were included in the study. The pre-operative spinal stenosis caused by bone fragments from the posterior margin of the vertebral body, as detected by CT scanning, ranged from 25 % to 85 %. Neurological deficit was due to injury in 19 patients and in one it developed post-operatively after the patient stood and walked. After ligamentotaxis and internal fixation, intra-operative myelography was used to show decompression of the spinal canal. A spinal block or severe constriction of contrast flow was an indication for hemilaminectomy (laminectomy) and direct decompression of the spinal canal. In the patients with neurological deficit and severe spinal stenosis persisting after ligamentotaxis and detectable by skiascopy, hemilaminectomy (laminectomy) and direct spinal decompression followed by intra-operative myelography were carried out.

Results: Intra-operative myelography was used 46 -times (20-times in 20 patients free from neurological deficit and 26-times in 20 patients with neurological deficit). In 38 cases (82.6 %) dural sac compression was not present (patients with neurological deficit, 13-times after ligamentotaxis, eight-times after ligamentotaxis and hemilaminectomy with direct decompression, twi- ce at repeat surgeryúúú patients without neurological deficit, 15-times). On two occasions (4.4 %) the contrast agent injected into the dural sac did not make the interior body part visible, on three occasions (6.5 %) contrast medium was injected extradurally, and dural sac compression following ligamentotaxis requiring hemilaminectomy (laminectomy) and direct decompression occurred in three cases (6.5 %). In the patients without neurological deficit, dural sac compression was not recorded. No serious complications associated with contrast medium injection in the dural sac were present, and there was no deterioration of neurological symptoms due to a dural tap. In three cases (6.5 %) a false negative finding was recorded, showing free flow of contrast medium with no areas of constriction or obstruction and signs of post-operative nerve irritation ( radicular syndrome associated with L3 fracture with a fragment placed laterally in two patients and hyperalgesia of the thigh after T12 fracture in one patient). Repeat surgery and additional decompression (hemilaminectomy and foraminotomy, laminectomy) resulted in immediate resolution of neurological symptoms.

Discussion: The success rate, complications and disadvantages of intra-operative myelography have not been reported. At present, ionic water-soluble contrast agents used for intrathecal administration are associated with only a low number of serious complications. Neurological deficit due to dural tap is rare. Extradural administration is not effective. A disadvantage reported here involves a failure to visualize the area because of a low amount of contrast agent administered to avoid spinal cord injury. A possibility of false negative findings arising from only one lateral view of the contrast agent flowing round fragments is the major disadvantage. In contrast to the previous reports, we relate the false negative findings to neurological findings.

Conclusions: Intra-operative myelography is still a currently used method. Its advantages include a simple procedure without removal of posterior column structures, and the possibility of objective recording and continuous observation of the dural sac. The free flow of contrast medium makes obstruction of the spinal canal impossible. The consequences of a false negative finding can be successfully treated at the second stage.