Accuracy of pedicle and mass screw placement in the spine without using fluoroscopy: a prospective clinical study

Spinal instrumentation is accompanied by various problems, including screw malpositioning. One way of preventing this is the employment of intraoperative biplanar fluoroscopy. However, screw malpositioning despite the use of fluoroscopy has been reported, and exposure to radiation is another burden of this method. Therefore, the purpose of this article was to compare the results of instrumentation applications without using scopy versus the harmful effects of radiation exposed during spinal instrumentation.

The aim of this article was to review the literature and this is the first prospective clinical study performed on this subject.

Patient report.

One hundred thirty-two patients with spinal instrumentations were included.

Radiological investigation with computed tomography (CT) scans was performed 2 days after the procedure.

Craniosacral posterior spinal instrumentation was performed without using scopy at the Neurosurgery Clinic of Haseki Training and Research Hospital between January 2000 and January 2005. Postoperative CT analyses were performed to evaluate whether the 527 screws used during posterior instrumentation in a total of 132 patients were positioned correctly. In all cases, the screw applications were performed with regard to anatomic landmarks, whereas the distances were determined according to lesion localizations. Screw malpositioning and the functional effects and relations with interactions with neurovascular structures were examined. At the end of the operations, all patients were examined with direct lateral roentgenograms and CT scans for the evaluation of screw positions.

According to their locations, 75 cervical screwing in 24 patients, 32 upper thoracic screwing in 7 patients, 30 midthoracic screwing in 7 patients, 306 thoracolumbar screwing in 54 patients, and 84 sacral screwing in 40 patients were performed by the senior spinal surgeon (KK). Among all posterior spinal instrumentation applications, the cervical region analyses revealed penetration of the medial wall of vertebral foramen with two (0.4%) screws, penetration of the lateral wall with one (0.2%) screw, and protrusion into the vertebral foramen without vascular penetration with one (0.2%) screw, whereas in the upper thoracic region there was penetration into the lateral pedicle wall with one (0.2%) screw and deviation toward the disc space through the superior end plate with two (0.4%) screws. In the midthoracic region, there was penetration into the disc space with two (0.4%) screws in only one case, whereas in the thoracolumbar complex, there was deviation toward the superior end plate with seven (1.4%) screws in four cases, deviation toward the disc space with two (0.4%) screws, medial wall penetration with six (1.2%) screws (two of which caused nerve root irritation in three cases), and penetration of the lateral wall of pedicle with four (0.8%) screws. In the sacral instrumentations, malpositioning occurred with only two (0.4%) screws because of deviation toward the medial wall. In summary, malpositioning occurred with 30 (5.6%) of the total 527 screws; none of the cases had neural or vascular damage. Two (1.5%) cases were revised for malpositioning and distance errors. The mean duration for preparation of screw introduction site and placement of the screw was 3 minutes. Infection occurred in only one (0.75%) case.

Screw application without fluoroscopy is performed with calculation of all essential anatomic details, and because of the reduction of surgery time, the absence of exposure to radiation, and very low infection rates as a consequence of reduced surgery time, it is a method recommendable for surgeons experienced with screw placement. Besides, its malpositioning rates are within acceptable limits. Because screw malpositioning is also found after biplanar fluoroscopy, the prevention of screw malpositioning requires knowing the anatomic landmarks accurately.