Modified C1 lateral mass screw insertion using a high entry point to avoid postoperative occipital neuralgia.

For the past decade, a screw-rod construct has been used commonly to stabilize the atlantoaxial joint, but the insertion of the screw through the C1 lateral mass (LM) can cause several complications. We evaluated whether using a higher screw entry point for C1 lateral mass (LM) fixation than in the standard procedure could prevent screw-induced occipital neuralgia. We enrolled 12 consecutive patients who underwent bilateral C1 LM fixation, with the modified screw insertion point at the junction of the C1 posterior arch and the midpoint of the posterior inferior portion of the C1 LM. We measured postoperative clinical and radiological parameters and recorded intraoperative complications, postoperative neurological deficits and the occurrence of occipital neuralgia. Postoperative plain radiographs were used to check for malpositioning of the screw or failure of the construct. Four patients underwent atlantoaxial stabilization for a transverse ligament injury or a C1 or C2 fracture, six patients for os odontoideum, and two patients for C2 metastasis. No patient experienced vertebral artery injury or cerebrospinal fluid leak, and all had minimal blood loss. No patient suffered significant occipital neuralgia, although one patient developed mild, transient unilateral neuralgia. There was also no radiographic evidence of construct failure. Twenty screws were positioned correctly through the intended entry points, but three screws were placed inferiorly (that is, below the arch), and one screw was inserted too medially. When performing C1-C2 fixation using the standard (Harms) construct, surgeons should be aware of the possible development of occipital neuralgia. A higher entry point may prevent this complication; therefore, we recommend that the screw should be inserted into the arch of C1 if it can be accommodated.