Abstract
We performed posterior spinal fusion with cortical bone trajectory screws (CBTs) in 5 patients (4 females, 1 male). The average age of the patients at surgery was 78 (range 65 to 89) years, and the average postoperative follow-up period was 12 (range 7 to 16) months. The average Japanese Orthopaedic Association Score was improved from 9.6 points preoperatively to 21.8 points postoperatively, although one patient developed MRSA infection after surgery. Postoperative computed tomography scanning revealed 4 cases of screw loosening in 2 patients. There were no other complications such as screw backout, fractures of the lamina around the screws, or nerve root injuries. The CBTs were designed to primarily utilize cortical bone of the lamina and pedicle, and to be placed in the medial to lateral direction as compared to conventional pedicle screws, which utilize cancellous bone in the pedicle and vertebrae by screw placement in a lateral to medial direction. The CBTs have pullout and toggle characteristics equivalent to those of conventional pedicle screws. The entry point on the lamina is located more medial by CBTs than by conventional pedicle screws. Therefore, wide exposure is unnecessary for placement of CBTs, thus minimizing surgical damage to the back muscles. Additional long-term follow-up will be needed to clarify the advantages or disadvantages associated with CBTs.
