Adjacent level ossification development after anterior cervical fusion without plate fixation.

Study Design: A retrospective.

Objective: The proximity of the plate to the adjacent disc space appeared to be the critical determinant of adjacent level ossification development (ALOD) but we had no data on unplated arthrodesis. Without such data, we could not be positive that ALOD was a complication related to plates.

Summary Of Background Data: We previously described the incidence and timing of ALOD after anterior cervical arthrodesis and plating.

Methods: One hundred sixty-five patients (total 330 adjacent levels) who underwent anterior cervical arthrodesis without plate fixation by a single surgeon were reviewed. The average follow-up period was 28.8 months (2-9 years); ages ranged from 32 to 79 years (median 59.86). The presence and severity of ALOD was assessed on the lateral radiographs at 3, 6, 12, and 24 months after surgery and then annually and recorded into 4 grades.

Results: ALOD developed in 9 patients at 10 levels (5.5% of patients and 3% of levels). Eight patients had a single-level (proximal or distal) ALOD, whereas 1 patient had both ALOD. Proximal ALOD developed in 7 cases, distal in 1 case and both in 1 case. ALOD initially appeared between 6 and 12 months in all cases: 4 cases occurred at 6 months and 5 cases at 12 months. During follow-up period, the final grade of proximal ALOD was grade I for 4 levels and grade II for 4 levels and final grade of distal ALOD was grade I for 1 level and grade II for 1 level. One patient with C3-C4 arthrodesis had both ALOD with grade I proximally and grade II distally.

Conclusion: ALOD is infrequent when certain techniques are adhered to. These include minimal stripping of the anterior longitudinal ligament and the avoidance of Caspar pins and anterior plates. It remains to be determined exactly which of these factors plays the dominant role in the production of ALOD.