Adjacent Nonbridged Ossification Near the Fixation Poses a Risk of Postoperative Progression of Ossification After Posterior Decompression and Fusion for Cervical Ossification of the Posterior Longitudinal Ligament.

INTRODUCTION

Postoperative progression of ossification of the posterior longitudinal ligament (OPLL) has been noted after posterior decompression surgery that does not involve direct resection of OPLL. It appeared that posterior decompression and fusion (PDF) may be more effective in preventing OPLL progression than posterior decompression alone; however, the connection between progression and the extent of fixation remains unclear. This study aimed to identify the ideal fixation range in PDF concerning the progression of OPLL after surgery. We also examined the OPLL progression characteristics post-PDF and the correlation between progression and fixation range.

METHODS

This retrospective study included 52 patients with cervical OPLL who underwent PDF and had both pre- and post-operative computed tomography images. We examined OPLL progression in thickness, width, and sagittal extension at each vertebra and intervertebral level. We statistically compared patient demographics and radiological data in patients with and without OPLL progression.

RESULTS

Throughout the average follow-up of 3.0 years, OPLL progression was observed in the fixed segments in one case (1.9%). However, 16 cases (31%) exhibited progression in the adjacent levels to the fusion. In one case (1.9%), reoperation was necessary owing to spinal cord compression resulting from the advanced OPLL. A comparison of patients with and without OPLL progression revealed that those with progression had a notably higher rate of nonbridged OPLL in the adjacent intervertebral space (94.1% versus 31.4%; p<0.001). A multivariate logistic analysis revealed that fewer fixation levels and nonbridged OPLL adjacent to the fixation were independent risk factors for OPLL progression.

CONCLUSIONS

Fixation with instrumentation could prevent OPLL progression in the fixation area in 98% of cases. However, 31% of cases progressed at the adjacent segment to the fixed end. Nonbridged OPLL at the segment adjacent to the fixation and fewer fixation levels were significant risk factors for OPLL progression.