Abstract
Aim: Of Calveston (USA) and Crete (HELLAS). We studied immediate and long-term outcome of 50 patients who underwent subaxial lateral mass fixation of the cervical spine between January 1997 and March 2001.
Patients and Methods: Intraopeartive fluoroscopy and somatosensory evoked potential monitoring were employed in all patients. Immediate postoperative CT scans were performed to determine screw trajectory and placement. Follow up ranged from 1 to 5 years.
Results: Postoperative CT scans showed that 113 of 210 screws (54%) had unicorticate and 46% had bicorticate purchase. Forty-five screws (31 %) had suboptimal trajectory, but only 7 of these screws minimally penetrated the foramen transversarium without resultant vascular or neurological sequelae.
The overall fusion success rate in our series was 90%, while pseudoarthrosis occurred in 5 patients (10%), with screw breakage in 1 patient (2%). Two of these patients had bone graft supplementation and in other 2 patients was done anterior fusion.
Conclusions: Results of this study show that the recommended drilling technique and trajectory (15–25 degrees postal to the sagital plane, 20–30 degrees lateral I the axial plane), supplemented bone grafting and intraoperative SEP monitoring are all associated to good screw placement, fusion and neurological outcome and are recommended for all lateral mass fusion procedures.
Correspondence should be addressed to 8 Martiou Str. Panorama, Thessaloniki PC:55236, Greece.
