Neurosurgery Resident Saint Louis University St. Louis, MO, US
Disclosure(s):
Jorge F. Urquiaga, MD: No financial relationships to disclose
Introduction: Instrumentation in the occipitocervical junction remains challenging in spine surgery. Occipital plates placement, alignment of the cervical plate with the cervical screws, and proper rod bending to match the fixation points are usually difficult tasks. The occipital condyle screw technique was previously described as a valid alternative to overcome such challenges. We aim to present an alternative to the current occipital fixation techniques, named the squamous-condyle screw, which allows the placement of a longer screw within a larger bone surface in the occipital bone.
Methods: A literature review was done to analyze the limitations in the current techniques for placement of condylar screws. A new entry point through the posterior occipital squama is proposed. We review the use of this technique in an illustrative case, highlighting its advantages over the classic entry point for the occipital condyle screw. Finally, some limitations of such a technique, especially related to patients with a thin occipital squama, and image-guidance dependence are discussed.
Results: The entry point of the squamous-condyle screw starts at the posterior surface of the lower portion of the occipital squama in craniocaudal alignment with the C1 lateral mass screw entry point. Due to the absence of clear anatomical landmarks to properly direct the screw toward the occipital condyle and the variable angle which such a screw can have depending on the initial degree of head positioning, the use of an intraoperative stereotactic-guidance is of paramount importance to locate the most appropriate entry point and trajectory. This new entry-point and trajectory allows for placement of longer screws (usually between 38-42mm screws) which further increase the biomechanical strength of this type of fixation. This modified condylar screw was successfully used intraoperatively for occipital fusion in several patients without any peri or post-operative complications.
Conclusion : The proposed squamous-condyle screw represents an alternative to the classic condyle screw, allowing the placement of a longer screw and minimizing the risks of neurovascular injuries associated with dissection and creation of an entry point in the posterior surface of the condyle.