Posterior cervical arthrodesis and stabilization with a lateral mass plate. Clinical and computed tomographic evaluation of lateral mass screw placement and associated complications.

STUDY DESIGN: A prospective study evaluating screw position and associated complications in 21 consecutive patients treated with a plate and screw fixation system applied to the lateral masses of the cervical spine. OBJECTIVES: To determine the clinical safety of lateral mass screws by determining their anatomic location and clinical complications in a consecutive patient series. SUMMARY OF BACKGROUND DATA: Lateral mass plating has been advocated for procedures in which wiring techniques cannot be used, especially in instances in which the posterior elements are deficient. METHODS: The first 21 consecutive patients who underwent posterior cervical arthrodesis and lateral mass plating with a single fixation system were reviewed prospectively. Computed tomography scans taken after surgery were reviewed independently by an orthopedic spinal surgeon and by a radiologist to evaluate screw tip position. Clinical and radiographic outcome was assessed at each visit after surgery. RESULTS: Ten of 164 (6.1%) lateral mass screws were malpositioned in six patients. Three symptomatic patients underwent four additional operative procedures to remove or replace the malpositioned screws. All patients had radiographic union, and no patient developed mechanical implant failure requiring removal of instrumentation. Radiographic evaluation noted that 17% of the screws were in the central axial zone of the lateral mass on computed tomography. CONCLUSIONS: Lateral mass plating was associated with no vertebral artery or spinal cord injury. There was a 1.8%-per-screw risk of radiculopathy, which corresponds with published cadaveric studies. Radicular symptoms improved with screw removal in each case. The advantages of segmental fixation achieved with lateral mass plates and screws must be weighed against the risk of radiculopathy.