An investigation of craniocervical stability post-condylectomy

BACKGROUND: Occipital condylectomy is often necessary to gain surgical access to various neurological pathologies. As the lateral limit of the craniovertebral junction (CVJ), partial condylectomy can lead to iatrogenic craniocervical instability. What was once considered an inoperable location is now the target of various complex neurosurgical procedures such as tumor resection and aneurysm clipping. METHODS: In this study, we will review the anatomical structure of the CVJ and provide the first comprehensive assessment of studies investigating craniovertebral stability following condylectomy with the transcondylar surgical approaches. Furthermore, we discuss future considerations that must be evaluated to optimize the chances of preserving craniocervical stability postcondylectomy. RESULTS: The current findings postulate upward of 75% of the occipital condyle can be resected without significantly affecting mobility of the CVJ. The current findings have only examined overall dimensions and have not established a significant correlation into how the shape of the occipital condyles can affect mobility. Occipitocervical fusion should only be considered after 50% condyle resection. In terms of indicators of anatomical stability, components of range of motion (ROM) such as the neutral zone (NZ) and the elastic zone (EZ) have been discussed as potential measures of craniocervical mobility. These components differ by the sense that the NZ has little ligament tension, whereas the EZ does represent ROM where ligaments experience tension. NZ is a more sensitive indicator of instability when measuring for instability postcondylectomy. CONCLUSION: Various transcondylar approaches have been developed to access this region including extreme-lateral and far-lateral condylectomy, with hopes of preserving as much of the condyle as possible and maintaining postoperative craniocervical stability.