Occipital bone erosion induced by C1 pedicle screw as a late complication of atlantoaxial fixation: a case report and literature review

Purpose The objective of this case report is to highlight occipital bone erosion as an unusual late complication of C1-C2 instrumented fixation. Case presentation A 60-year-old man of a displaced Anderson type II odontoid fracture was surgically treated by C1-C2 pedicle screw fixation. Occipital bone erosions, caused by a repeat irritation of the end of rod to the occipital bone, were detected on multiplane reconstructed computed tomography at 3 months after surgery. The lesion progressed over time with increasing the C2 anteversion on radiological evaluations. Eventually, the bony shell had been reactively formed around the protruded screw-rod construct and the Oc-C1 segment had been spontaneously stabilized. Fortunately, he had experienced no symptoms caused by the lesion at 5-year follow-up. Conclusion The occipital bone erosion is an unusual late complication in C1-C2 posterior fixation using C1 pedicle screw. The increasing occipital-C1 lordosis compensating for the great C2 anteversion (high C2 slope) was related to the progression of the lesion. In C1-C2 pedicle screw fixation, surgeons should recognize a possibility of this complication and realize a relation between the occurrence of the lesion and the sagittal alignment of the cervical spine to take measures to avoid the complication.