Study Design:

This vvas a prospective computed tomographic analysis and clinical complications of the first twenty one consecutive patients treated with a plate and screw fixation system applied to the lateral masses of the cervical spine,

Objectives:

We wished to determine the clinical safety of lateral mass screws by detecmining 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. Two cadaver studies have reported the procedure to be relatively saf e with a low, but definable, rate of potential neurologic in-jury. No clinical series have been published correlating the CT anatomy with clinical outcome.

Methods:

The first twenty-one consecutive patients who undement posterior cervical arthrodesis and lateral mass plating with a single fixation system were reviewedprospectively. The surgeries were performed by two ex-perienced spinal surgeons with the assistance of a spine surgery fellow. The Magerl technique vvas employed for screw placement. Postoperative CT seans were revievved independently by an orthopaedic spinal surgeon and by a radiologist to evaluate screw tip position. An axial and sagittal zone system was used to precisely locate the serevvtip within the lateral mass. Clinical and radiographic outcome vvas assessed at each postoperative visit.

Results:

Ten of 164 (6.1%) lateral mass screws were malpositioned in six patients. Three symptomatic patients undement 4 additional operative procedures to remove or replace the ineriminating screws. One patient had a motor deficit which responded to screw removal. Two patients had sensory radiculopathies which incompletely resolved after screw removal. No patient had spinal cord or vertebral artery injury. AH patients had radiographic union and no patient developed mechanical failure requiring removal of instrumentation.

Conclusions:

Lateral mass plating vvas associated with no vertebral artery or spinal cord injury in this clinical series. There was a low per screw risk of neurologic injury (1.8%) which corresponded with published cadaver studies. The method vvas found to be clinically efficacious as there were no instances of radiographic nonunion or mechanical hardware failures leading to revision.

Keywords: CT evaluatin, Lateral Mass, Cervical, Arthrodesis, Plating