Cervical Instrumentation II
5:01-5:30 PM

OCCIPITOCERVICAL FUSION WITH PLATES AND SCREWS: LESSONS FROM THE INITIAL SERIES

David W. Cahill, MD*

Tampa, FL

TIME: Friday, October 25, 1996, 5:09-5:15 PM
PLACE: Meeting Room 2/3

Introduction
Traditional occipitocervical fusion (O-C fusion) techniques involved nonrigid external orthoses. Subsequently, surgical constructs using rods, rod rectangles, or plate rods affixed with wire became popular in some centers. More recently, rigid fixation with screw fixated lateral mass to skull plates has become feasible. Herein, we discuss the intra- and post-operative complications noted in our first 12 cases using this technique.

Methods
Twelve cases of O-C plate fusion were accomplished over a 32-month period and have now been followed for 9 to 45 months. Three males and 9 females (aged 24 to 81 years) underwent surgery for rheumatoid instability (4), complex fractures (2), or congenital anomalies (6). Four of the latter also had transoral odontoidectomies. There were no deaths in the series but there were 2 major neurologic complications. One male with a complex basilar anomaly and 3 previous operations suffered a high cervical cord infarction 8 days post-op. A rheumatoid female suffered a cerebellar subdural hematoma secondary to drill or screw injury to a small cortical cerebellar artery. In 3 cases, thin occipital bone required occ. attachment of plates with cables rather than screws, in 3 cases complex anatomy required C1 or C2 purchases with cables rather than screws decreasing construct rigidity. Incidental pull-out of 1 or more skull screws occurred in 2 cases, subaxial lateral mass screw pull-out occurred in 3 cases. All cases went on to fusion eventually.

Conclusion

1. O-C fusion, using plates and screws, is technically demanding and not feasible in every case;
2. Purchase of the midline "keel" bone is greatly superior to dependence on the usually thin lateral subocciput;
3. There is a small but definite risk of life-threatening posterior fusion hemorrhage;
4. Firm purchase of the C2 vertebra is mandatory as subaxial lateral mass screws do not provide adequate purchase to resist loads imposed by the cranium; and
5. If anatomical constraints and bone quality allow rigid purchase of the subocciput and C2 vertebra, no better construct exists for occipitocervical fixation.