Use of spinous processes to determine the optimal trajectory for placement of lateral mass screws: technical note

Retrospective chart analysis. In the current report, we present a new technique for the placement of lateral mass screws from C3 to C7. The safety, complications, and long-term clinical and imaging follow-up were analyzed. To address potential risk factors for this technique, relevant literature was reviewed and discussed herein. Multiple techniques have been reported to place lateral mass screws in the subaxial cervical spine. The trajectory used aims to avoid the vertebral artery and the exiting nerve root. Because of inherent differences in determining the screw trajectory for placement, there can be considerable differences among surgeons. A retrospective analysis of our experience over the period from 2003 to 2006 was undertaken. Standard practices for obtaining institutional review board approval were followed. Radiographs, hospital records, and office charts of 34 patients were reviewed. There was an equal distribution between males and females and the mean age was 56.3 years. Pain was the most frequent presentation. The indications for posterior instrumentation included instability secondary to pseudoarthrosis, infection, spondylosis, osseous metastasis, trauma, and iatrogenic etiologies. The follow-up period ranged from 1 to 30 months (average 9.1 mo). Postoperative complications included wound infection (3 cases), malpositioned screw (1 case), cerebrospinal fluid leak (1 case), and dislodged rod (1 case). There were no mortalities directly related to the procedure. This technique for placement of lateral mass screws yielded adequate fixation without any appreciable neurovascular complications. It provides a useful alternative for screw placement in patients with intact spinous processes.