Clinical and Computed Tomography Evaluation of Plate and Screw on the Cervical Lateral Mass: A Modified Magerl's Technique

OBJECTIVE: To determine the clinical and radiological safety of 15 consecutive patients managed with plate and screw fixation systems applied to the cervical lateral mass. METHODS: 15 patients who underwent posterior cervical and T1 arthrodesis were reviewed from Jan 2002 to Dec 2004. Posterior cervical screw and plate fixation was applied on the lateral mass of the cervical spine. The authors have tried lateral mass screw fixation using a modified Magerl's technique (20 degrees lateral and 20~30 degrees rostral screw trajectory) under preliminary radiological study. The average patient age was 39.73 degrees+/-11.00 years, and the average follow-up period was 9.73 degrees+/-6.77 months. Computed tomography scans taken after surgery were reviewed to confirm the attempted screw trajectory correct and safety. RESULTS: Three of 93 lateral mass screws were malpositioned but clinical damage was not noted. Two of 8 pedicle screws on the T1 vertebrae were not placed on the correct pedicle area. Screw and plate loosening was observed in one case but was not subjected to an additional procedure because of maintained screw position observed during follow-up periods. CONCLUSION: The results of this study indicate that lateral mass screw fixation using the Modified Magerl's technique on the cervical lateral mass may provide safe and effective application on the patients. In addition, the chance of incorrectly placed screws was higher in T1 pedicle screw fixation than in lateral mass screw fixation of the cervical area.

Radiological Considerations of Posterior Cervical Lateral Mass Fixation Using Plate and Screw

The aim of this study is to determine whether the posterior cervical fusion methods with the plate-screw system applied to the lateral mass of cervical spine are radiologically safe to patients. The lateral cervical X-rays and CT scans were done on 40 normal adults without cervical problem. Based on Roy-Camille and Magerl's method, the theological trajectory of screw was shown on films and the parameters were measured. The study based on Roy-Camille's method showed less than one percent chance of injury on the facet joint and the mean depth of the screw to be 10.5+/-1.4mm. On the other hand, Magerl's method showed the mean depth of screw to be 11.9+/-1.5mm which is slightly larger than that of Roy-Camille's method and no chance of facet injury occurred. A reduced lateral angle of screw (19.6+/-3.5 degrees) performed with the concept based on Magerl's method resulted a longer depth of screw (13.5+/-2.1mm). Both Roy-Camille and Magerl's methods seemed to be radiologically safe to normal persons. However, the authors recommend the reduced lateral angle (19.6+/-3.5 degrees) of screw based on the Magerl's method more than an original Magerl's methods.