Occipital Bone Erosion Caused by C1 Lateral Mass Screw-Rod Construct Used for C1/2 Arthrodesis: A Case Report

C1 lateral mass screw (C1LMS) is used as a standard implant for fixation of the upper cervical spine. The most significant benefit of the fixation using C1LMS is that it can obtain an excellent mechanical stability immediately after surgery without a massive structural bone graft and strict orthosis. Meanwhile, several studies have already referred to complications, which have not been seen in conventional devices. As for one of the complications, occipital bone erosion (OcBE) induced by repetitive impingement between the occipital bone and the protruded metal implant on the C1 posterior has been rarely reported. OcBE develops infrequently and leads to serious complications, including cerebrospinal fluid leakage and intracranial hemorrhaging. A 78-year-old male case with OcBE, which developed after atlantoaxial arthrodesis using C1 lateral mass and C2 translaminar screws, was presented. In the current case, increased O-C2 angle compensating the subaxial kyphosis, protrusion of C1LMS-rod construct, and cephalad located entry point of C1LMS are related to the occurrence of OcBE.