Atlas Lateral Mass Screw Fixation in Atlanto-Axial Instability, Clinical Case Series

Background Data: Segmental spinal screw fixation has been used effectively for subaxial spine instability for long time. However, atlantoaxial fixation is still challenging due to complex topographical anatomy. So, sublaminar wires werefrequently used despite their complications. Unlike transarticular atlantoaxial screws which necessitate perfect reduction before insertion, C1 lateral mass screws are inserted independently of C2. Purpose: The aim of this work is to assess the safety and efficiency of C1 lateral mass screw fixation in cases with atlantoaxial instability. Study Design: A prospective clinical case study. Patients and Methods: This study was conducted in Al-Manial university hospital, Kasr Al-Aini Medical School, Cairo University, between 2008 and 2013. Ten patients underwent segmental atlantoaxial screw fixation using atlas lateral mass screws and either transpars interarticularis or transpedicular axis screws. Clinical results were evaluated by using the criteria of Japanese Orthopaedic Association Scoring System for Cervical Myelopathy (JOA score). The surgical technique, results and morbidity and mortality were assessed. Results: There were 6 females and 4 males; the average age was 30.2 ±17.5 y (range from 4y-61 years). The most common cause of atlantoaxial instability wastrauma (6 patients), followed by os odontoideum (2 patients ). The most common presentation was quadriparesis (5 patients) followed by neck pain and paresthesia. At the end of follow up (mean 8.5± 4.2 months) the average preoperative JOA score improved from 13.1±1.9 to 15.2±1.6 (P=0.005) and the average recovery rate was48.3±17.8%. Twenty screws were inserted in lateral mass of atlas successfully. The average screw length was 27.8±1.5mm (range 24-31mm). Postoperative CT scans showed the mean atlantodens interval improved from 5.4±1.9 to 1±1.4 (P=0.004), MRI showed that the mean cervico-medullary angle changed from 126.2°±9.4°to 141.1°±12.4° (P=0.005). There was no mortality or vertebral artery injury. One patient had profuse venous bleeding and one unit of blood was transfused and one patient had superficial wound infection and managed conservatively.Conclusion: C1 lateral mass screw fixation is a safe and effective method of atlantoaxial fixation with low complication rate. (2013ESJ052)