Complications associated with pedicle screws

Background: The safety and the effectiveness of pedicle-screw instrumentati on in the spine have been questioned despite its use worldwide to enhance s tabilization of the spine. This review was performed to answer questions ab out the technique of insertion and the nature and etiology of complications directly attributable to the screws. Methods: We performed a retrospective review of all of the pedicle-screw pr ocedures that were done by us from January 1, 1984, to December 31, 1993, W e inserted 4790 screws during 915 operative procedures on 875 patients; 668 (76.3 percent) of the patients had a lumbosacral arthrodesis. The mean dur ation of follow-up was three years (range, two to five years). The accuracy of screw placement was assessed on intraoperative, immediate postoperative , and follow-up radiographs with use of a technique that was developed by o ne of us (F. D.); this technique has yet to be validated to determine the p revalence of various types of error. Results: Of the 4790 screws, 4548 (94.9 percent) had been inserted within t he pedicle and the vertebral body One hundred and thirty-four (2.8 percent) of the screws had perforated the anterior cortex, and this was the most co mmon type of perforation, One hundred and fifteen (2.4 percent) of the scre ws were associated with complications that could be ascribed to the use of pedicle screws, The most common problem was late-onset discomfort or pain r elated to a pseudarthrosis or perhaps to the screws; this problem was assoc iated with 1102 (23.0 percent) of the screws, used in 222 (24.3 percent) of the procedures. The symptoms necessitated removal of the instrumentation w ith or without repair of the pseudarthrosis, A pseudarthrosis was found dur ing forty-six (20.7 percent) of the 222 procedures. Irritation of a nerve root occurred after nine procedures (1.0 percent) and was caused by eleven screws (0.2 percent); it was more commonly caused by medially placed screws. Three patients had residual neurological weakness d espite removal of the screws. Twenty-five screws (0.5 percent), used in twe nty procedures (2.2 percent), broke, The screws that broke were of an early design. A pseudarthrosis was found in thirteen of twenty patients who had broken screws, Sixteen of the twenty patients had an exploration; three of them were found to have a solid fusion, and thirteen were found to have a p seudarthrosis. The remaining four patients had evidence of a solid fusion o n radiographs and had no pain. Conclusions: There are few problems associated with the insertion of screws , provided that the surgeon is experienced and adheres to the principles an d details of the operative technique. Our review revealed a low rate of pos toperative complications related to pedicle screws, The problem of late-ons et pain mag be related to the implants or to the stiffness of the construct ; however, it is difficult to accurately identify its exact etiology.